[7906] | 1 | """Class Domain - |
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| 2 | 1D interval domains for finite-volume computations of |
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| 3 | the shallow water wave equation. |
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| 4 | |
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| 5 | This module contains a specialisation of class Domain from module domain.py |
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| 6 | consisting of methods specific to the Shallow Water Wave Equation |
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| 7 | |
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| 8 | |
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| 9 | U_t + E_x = S |
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| 10 | |
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| 11 | where |
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| 12 | |
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| 13 | U = [w, uh] |
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| 14 | E = [uh, u^2h + gh^2/2] |
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| 15 | S represents source terms forcing the system |
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| 16 | (e.g. gravity, friction, wind stress, ...) |
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| 17 | |
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| 18 | and _t, _x, _y denote the derivative with respect to t, x and y respectiely. |
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| 19 | |
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| 20 | The quantities are |
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| 21 | |
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| 22 | symbol variable name explanation |
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| 23 | x x horizontal distance from origin [m] |
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| 24 | z elevation elevation of bed on which flow is modelled [m] |
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| 25 | h height water height above z [m] |
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| 26 | w stage absolute water level, w = z+h [m] |
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| 27 | u speed in the x direction [m/s] |
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| 28 | uh xmomentum momentum in the x direction [m^2/s] |
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| 29 | |
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| 30 | eta mannings friction coefficient [to appear] |
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| 31 | nu wind stress coefficient [to appear] |
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| 32 | |
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| 33 | The conserved quantities are w, uh |
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| 34 | |
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| 35 | For details see e.g. |
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| 36 | Christopher Zoppou and Stephen Roberts, |
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| 37 | Catastrophic Collapse of Water Supply Reservoirs in Urban Areas, |
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| 38 | Journal of Hydraulic Engineering, vol. 127, No. 7 July 1999 |
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| 39 | |
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| 40 | John Jakeman, Ole Nielsen, Stephen Roberts, Duncan Gray, Christopher Zoppou |
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| 41 | Geoscience Australia, 2006 |
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| 42 | |
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| 43 | Sudi Mungkasi, ANU, 2010 |
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| 44 | """ |
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| 45 | |
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| 46 | |
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| 47 | from domain import * |
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| 48 | Generic_Domain = Domain #Rename |
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| 49 | |
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| 50 | #Shallow water domain |
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| 51 | class Domain(Generic_Domain): |
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| 52 | |
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| 53 | def __init__(self, coordinates, boundary = None, tagged_elements = None): |
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| 54 | conserved_quantities = ['stage', 'xmomentum'] #['height', 'xmomentum'] |
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| 55 | evolved_quantities = ['stage', 'xmomentum', 'elevation', 'height', 'velocity'] |
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| 56 | other_quantities = ['friction'] |
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| 57 | Generic_Domain.__init__(self, coordinates, boundary, |
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| 58 | conserved_quantities, evolved_quantities, other_quantities, |
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| 59 | tagged_elements) |
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| 60 | |
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| 61 | from config import minimum_allowed_height, g, h0 |
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| 62 | self.minimum_allowed_height = minimum_allowed_height |
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| 63 | self.g = g |
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| 64 | self.h0 = h0 |
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| 65 | |
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| 66 | self.forcing_terms.append(gravity_F2) |
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| 67 | #self.forcing_terms.append(manning_friction) |
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| 68 | |
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| 69 | #Realtime visualisation |
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| 70 | self.visualiser = None |
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| 71 | self.visualise = False |
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| 72 | self.visualise_color_stage = False |
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| 73 | self.visualise_stage_range = 1.0 |
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| 74 | self.visualise_timer = True |
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| 75 | self.visualise_range_z = None |
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| 76 | |
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| 77 | #Stored output |
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| 78 | self.store = True |
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| 79 | self.format = 'sww' |
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| 80 | self.smooth = True |
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| 81 | |
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| 82 | #Evolve parametrs |
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| 83 | self.cfl = 1.0 |
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| 84 | |
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| 85 | #Reduction operation for get_vertex_values |
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| 86 | from util import mean |
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| 87 | self.reduction = mean |
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| 88 | #self.reduction = min #Looks better near steep slopes |
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| 89 | |
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| 90 | self.quantities_to_be_stored = ['stage','xmomentum'] |
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| 91 | |
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| 92 | self.__doc__ = 'sww_domain_shm' |
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| 93 | self.check_integrity() |
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| 94 | |
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| 95 | |
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| 96 | def set_quantities_to_be_stored(self, q): |
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| 97 | """Specify which quantities will be stored in the sww file. |
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| 98 | |
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| 99 | q must be either: |
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| 100 | - the name of a quantity |
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| 101 | - a list of quantity names |
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| 102 | - None |
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| 103 | |
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| 104 | In the two first cases, the named quantities will be stored at each |
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| 105 | yieldstep |
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| 106 | (This is in addition to the quantities elevation and friction) |
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| 107 | If q is None, storage will be switched off altogether. |
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| 108 | """ |
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| 109 | |
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| 110 | if q is None: |
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| 111 | self.quantities_to_be_stored = [] |
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| 112 | self.store = False |
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| 113 | return |
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| 114 | |
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| 115 | if isinstance(q, basestring): |
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| 116 | q = [q] # Turn argument into a list |
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| 117 | |
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| 118 | #Check correcness |
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| 119 | for quantity_name in q: |
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| 120 | msg = 'Quantity %s is not a valid conserved quantity' %quantity_name |
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| 121 | assert quantity_name in self.conserved_quantities, msg |
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| 122 | |
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| 123 | self.quantities_to_be_stored = q |
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| 124 | |
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| 125 | |
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| 126 | def initialise_visualiser(self,scale_z=1.0,rect=None): |
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| 127 | #Realtime visualisation |
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| 128 | if self.visualiser is None: |
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| 129 | from realtime_visualisation_new import Visualiser |
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| 130 | self.visualiser = Visualiser(self,scale_z,rect) |
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| 131 | self.visualiser.setup['elevation']=True |
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| 132 | self.visualiser.updating['stage']=True |
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| 133 | self.visualise = True |
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| 134 | if self.visualise_color_stage == True: |
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| 135 | self.visualiser.coloring['stage'] = True |
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| 136 | self.visualiser.qcolor['stage'] = (0.0, 0.0, 0.8) |
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| 137 | print 'initialise visualiser' |
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| 138 | print self.visualiser.setup |
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| 139 | print self.visualiser.updating |
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| 140 | |
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| 141 | def check_integrity(self): |
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| 142 | Generic_Domain.check_integrity(self) |
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| 143 | #Check that we are solving the shallow water wave equation |
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| 144 | |
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| 145 | msg = 'First conserved quantity must be "stage"' |
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| 146 | assert self.conserved_quantities[0] == 'stage', msg |
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| 147 | msg = 'Second conserved quantity must be "xmomentum"' |
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| 148 | assert self.conserved_quantities[1] == 'xmomentum', msg |
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| 149 | |
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| 150 | msg = 'First evolved quantity must be "stage"' |
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| 151 | assert self.evolved_quantities[0] == 'stage', msg |
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| 152 | msg = 'Second evolved quantity must be "xmomentum"' |
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| 153 | assert self.evolved_quantities[1] == 'xmomentum', msg |
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| 154 | msg = 'Third evolved quantity must be "elevation"' |
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| 155 | assert self.evolved_quantities[2] == 'elevation', msg |
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| 156 | msg = 'Fourth evolved quantity must be "height"' |
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| 157 | assert self.evolved_quantities[3] == 'height', msg |
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| 158 | msg = 'Fifth evolved quantity must be "velocity"' |
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| 159 | assert self.evolved_quantities[4] == 'velocity', msg |
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| 160 | |
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| 161 | def extrapolate_second_order_sw(self): |
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| 162 | #Call correct module function |
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| 163 | #(either from this module or C-extension) |
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| 164 | extrapolate_second_order_sw(self) |
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| 165 | |
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| 166 | def compute_fluxes(self): |
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| 167 | #Call correct module function(either from this module or C-extension) |
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| 168 | compute_fluxes_C_wellbalanced(self) |
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| 169 | #compute_fluxes_C_nonwellbalanced2(self) |
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| 170 | |
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| 171 | def compute_timestep(self): |
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| 172 | #Call correct module function |
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| 173 | compute_timestep(self) |
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| 174 | |
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| 175 | def distribute_to_vertices_and_edges(self): |
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| 176 | #Call correct module function(either from this module or C-extension) |
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| 177 | #distribute_to_vertices_and_edges_shv(self) |
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| 178 | distribute_to_vertices_and_edges_shm(self) |
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| 179 | |
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| 180 | def evolve(self, yieldstep = None, finaltime = None, duration = None, skip_initial_step = False): |
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| 181 | #Call basic machinery from parent class |
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| 182 | for t in Generic_Domain.evolve(self, yieldstep, finaltime, duration, skip_initial_step): |
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| 183 | yield(t) |
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| 184 | |
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| 185 | def initialise_storage(self): |
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| 186 | """Create and initialise self.writer object for storing data. |
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| 187 | Also, save x and bed elevation |
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| 188 | """ |
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| 189 | |
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| 190 | import data_manager |
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| 191 | |
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| 192 | #Initialise writer |
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| 193 | self.writer = data_manager.get_dataobject(self, mode = 'w') |
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| 194 | |
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| 195 | #Store vertices and connectivity |
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| 196 | self.writer.store_connectivity() |
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| 197 | |
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| 198 | |
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| 199 | def store_timestep(self, name): |
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| 200 | """Store named quantity and time. |
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| 201 | |
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| 202 | Precondition: |
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| 203 | self.write has been initialised |
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| 204 | """ |
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| 205 | self.writer.store_timestep(name) |
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| 206 | |
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| 207 | |
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| 208 | #=============== End of Shallow Water Domain =============================== |
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| 209 | |
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| 210 | # Compute flux definition |
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| 211 | # ################################### |
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| 212 | def compute_fluxes_C_wellbalanced(domain): |
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| 213 | import sys |
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| 214 | from Numeric import Float |
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| 215 | from numpy import zeros |
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| 216 | |
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| 217 | N = domain.number_of_elements |
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| 218 | timestep = float(sys.maxint) |
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| 219 | epsilon = domain.epsilon |
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| 220 | g = domain.g |
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| 221 | neighbours = domain.neighbours |
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| 222 | neighbour_vertices = domain.neighbour_vertices |
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| 223 | normals = domain.normals |
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| 224 | areas = domain.areas |
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| 225 | |
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| 226 | Stage = domain.quantities['stage'] |
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| 227 | Xmom = domain.quantities['xmomentum'] |
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| 228 | Bed = domain.quantities['elevation'] |
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| 229 | Height = domain.quantities['height'] |
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| 230 | Velocity = domain.quantities['velocity'] |
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| 231 | |
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| 232 | |
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| 233 | stage_boundary_values = Stage.boundary_values |
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| 234 | xmom_boundary_values = Xmom.boundary_values |
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| 235 | bed_boundary_values = Bed.boundary_values |
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| 236 | height_boundary_values= Height.boundary_values |
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| 237 | vel_boundary_values = Velocity.boundary_values |
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| 238 | |
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| 239 | stage_explicit_update = Stage.explicit_update |
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| 240 | xmom_explicit_update = Xmom.explicit_update |
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| 241 | bed_explicit_values = Bed.explicit_update |
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| 242 | height_explicit_values= Height.explicit_update |
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| 243 | vel_explicit_values = Velocity.explicit_update |
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| 244 | |
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| 245 | max_speed_array = domain.max_speed_array |
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| 246 | |
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| 247 | domain.distribute_to_vertices_and_edges() |
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| 248 | domain.update_boundary() |
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| 249 | |
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| 250 | stage_V = Stage.vertex_values |
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| 251 | xmom_V = Xmom.vertex_values |
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| 252 | bed_V = Bed.vertex_values |
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| 253 | height_V= Height.vertex_values |
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| 254 | vel_V = Velocity.vertex_values |
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| 255 | |
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| 256 | number_of_elements = len(stage_V) |
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| 257 | |
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| 258 | from comp_flux_ext_wellbalanced import compute_fluxes_ext_wellbalanced |
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| 259 | domain.flux_timestep = compute_fluxes_ext_wellbalanced(timestep, |
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| 260 | epsilon, |
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| 261 | g, |
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| 262 | |
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| 263 | neighbours, |
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| 264 | neighbour_vertices, |
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| 265 | normals, |
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| 266 | areas, |
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| 267 | |
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| 268 | stage_V, |
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| 269 | xmom_V, |
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| 270 | bed_V, |
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| 271 | height_V, |
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| 272 | vel_V, |
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| 273 | |
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| 274 | stage_boundary_values, |
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| 275 | xmom_boundary_values, |
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| 276 | bed_boundary_values, |
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| 277 | height_boundary_values, |
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| 278 | vel_boundary_values, |
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| 279 | |
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| 280 | stage_explicit_update, |
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| 281 | xmom_explicit_update, |
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| 282 | bed_explicit_values, |
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| 283 | height_explicit_values, |
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| 284 | vel_explicit_values, |
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| 285 | |
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| 286 | number_of_elements, |
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| 287 | max_speed_array) |
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| 288 | |
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| 289 | |
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| 290 | # ################################### |
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| 291 | # Module functions for gradient limiting (distribute_to_vertices_and_edges) |
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| 292 | def distribute_to_vertices_and_edges_shv(domain): |
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| 293 | """Distribution from centroids to vertices specific to the |
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| 294 | shallow water wave |
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| 295 | equation. |
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| 296 | |
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| 297 | It will ensure that h (w-z) is always non-negative even in the |
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| 298 | presence of steep bed-slopes by taking a weighted average between shallow |
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| 299 | and deep cases. |
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| 300 | |
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| 301 | In addition, all conserved quantities get distributed as per either a |
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| 302 | constant (order==1) or a piecewise linear function (order==2). |
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| 303 | |
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| 304 | FIXME: more explanation about removal of artificial variability etc |
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| 305 | |
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| 306 | Precondition: |
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| 307 | All quantities defined at centroids and bed elevation defined at |
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| 308 | vertices. |
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| 309 | |
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| 310 | Postcondition |
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| 311 | Conserved quantities defined at vertices |
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| 312 | |
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| 313 | """ |
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| 314 | |
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| 315 | #from config import optimised_gradient_limiter |
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| 316 | |
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| 317 | #Remove very thin layers of water |
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| 318 | #protect_against_infinitesimal_and_negative_heights(domain) |
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| 319 | |
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| 320 | import sys |
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| 321 | from Numeric import Float |
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| 322 | from numpy import zeros |
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| 323 | from config import epsilon, h0 |
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| 324 | |
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| 325 | N = domain.number_of_elements |
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| 326 | |
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| 327 | #Shortcuts |
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| 328 | Stage = domain.quantities['stage'] |
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| 329 | Xmom = domain.quantities['xmomentum'] |
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| 330 | Bed = domain.quantities['elevation'] |
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| 331 | Height = domain.quantities['height'] |
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| 332 | Velocity = domain.quantities['velocity'] |
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| 333 | |
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| 334 | #Arrays |
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| 335 | w_C = Stage.centroid_values |
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| 336 | uh_C = Xmom.centroid_values |
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| 337 | z_C = Bed.centroid_values |
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| 338 | h_C = Height.centroid_values |
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| 339 | u_C = Velocity.centroid_values |
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| 340 | |
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| 341 | for i in range(N): |
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| 342 | h_C[i] = w_C[i] - z_C[i] |
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| 343 | if h_C[i] <= epsilon: |
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| 344 | uh_C[i] = 0.0 |
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| 345 | u_C[i] = 0.0 |
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| 346 | #w_C[i] = z_C[i] |
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| 347 | else: |
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| 348 | u_C[i] = uh_C[i]/(h_C[i] + h0/h_C[i]) |
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| 349 | |
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| 350 | for name in ['stage', 'height', 'velocity']: |
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| 351 | Q = domain.quantities[name] |
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| 352 | if domain.order == 1: |
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| 353 | Q.extrapolate_first_order() |
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| 354 | elif domain.order == 2: |
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| 355 | Q.extrapolate_second_order() |
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| 356 | else: |
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| 357 | raise 'Unknown order' |
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| 358 | |
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| 359 | stage_V = domain.quantities['stage'].vertex_values |
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| 360 | bed_V = domain.quantities['elevation'].vertex_values |
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| 361 | h_V = domain.quantities['height'].vertex_values |
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| 362 | u_V = domain.quantities['velocity'].vertex_values |
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| 363 | xmom_V = domain.quantities['xmomentum'].vertex_values |
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| 364 | |
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| 365 | bed_V[:] = stage_V - h_V |
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| 366 | xmom_V[:] = u_V * h_V |
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| 367 | |
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| 368 | return |
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| 369 | |
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| 370 | def distribute_to_vertices_and_edges_shm(domain): |
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| 371 | # shm stands for STAGE, HEIGHT, MOMENTUM |
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| 372 | """Distribution from centroids to vertices specific to the |
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| 373 | shallow water wave |
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| 374 | equation. |
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| 375 | |
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| 376 | It will ensure that h (w-z) is always non-negative even in the |
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| 377 | presence of steep bed-slopes by taking a weighted average between shallow |
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| 378 | and deep cases. |
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| 379 | |
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| 380 | In addition, all conserved quantities get distributed as per either a |
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| 381 | constant (order==1) or a piecewise linear function (order==2). |
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| 382 | |
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| 383 | FIXME: more explanation about removal of artificial variability etc |
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| 384 | |
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| 385 | Precondition: |
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| 386 | All quantities defined at centroids and bed elevation defined at |
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| 387 | vertices. |
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| 388 | |
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| 389 | Postcondition |
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| 390 | Conserved quantities defined at vertices |
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| 391 | |
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| 392 | """ |
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| 393 | |
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| 394 | #from config import optimised_gradient_limiter |
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| 395 | |
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| 396 | #Remove very thin layers of water |
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| 397 | #protect_against_infinitesimal_and_negative_heights(domain) |
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| 398 | |
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| 399 | import sys |
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| 400 | from Numeric import Float |
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| 401 | from numpy import array, zeros |
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| 402 | from config import epsilon, h0 |
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| 403 | |
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| 404 | N = domain.number_of_elements |
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| 405 | |
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| 406 | #Shortcuts |
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| 407 | Stage = domain.quantities['stage'] |
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| 408 | Xmom = domain.quantities['xmomentum'] |
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| 409 | Bed = domain.quantities['elevation'] |
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| 410 | Height = domain.quantities['height'] |
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| 411 | Velocity = domain.quantities['velocity'] |
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| 412 | |
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| 413 | #Arrays |
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| 414 | w_C = Stage.centroid_values |
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| 415 | uh_C = Xmom.centroid_values |
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| 416 | z_C = Bed.centroid_values |
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| 417 | h_C = Height.centroid_values |
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| 418 | u_C = Velocity.centroid_values |
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| 419 | |
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| 420 | |
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| 421 | for i in range(N): |
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| 422 | h_C[i] = w_C[i] - z_C[i] |
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| 423 | if h_C[i] <= epsilon: |
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| 424 | uh_C[i] = 0.0 |
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| 425 | u_C[i] = 0.0 |
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| 426 | else: |
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| 427 | u_C[i] = uh_C[i]/(h_C[i] + h0/h_C[i]) |
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| 428 | |
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| 429 | for name in ['stage', 'height', 'xmomentum']: |
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| 430 | Q = domain.quantities[name] |
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| 431 | if domain.order == 1: |
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| 432 | Q.extrapolate_first_order() |
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| 433 | elif domain.order == 2: |
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| 434 | Q.extrapolate_second_order() |
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| 435 | else: |
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| 436 | raise 'Unknown order' |
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| 437 | |
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| 438 | stage_V = domain.quantities['stage'].vertex_values |
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| 439 | bed_V = domain.quantities['elevation'].vertex_values |
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| 440 | h_V = domain.quantities['height'].vertex_values |
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| 441 | u_V = domain.quantities['velocity'].vertex_values |
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| 442 | xmom_V = domain.quantities['xmomentum'].vertex_values |
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| 443 | |
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| 444 | bed_V[:] = stage_V - h_V |
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| 445 | |
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| 446 | for i in range(N): |
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| 447 | if min(h_V[i]) <= 0.0: |
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| 448 | h_V[i] = array([0.0, 0.0]) |
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| 449 | stage_V[i] = bed_V[i] |
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| 450 | xmom_V[i] = array([0.0, 0.0]) |
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| 451 | |
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| 452 | u_V[:] = xmom_V/(h_V + h0/h_V) |
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| 453 | |
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| 454 | return |
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| 455 | |
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| 456 | |
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| 457 | |
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| 458 | # |
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| 459 | def protect_against_infinitesimal_and_negative_heights(domain): |
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| 460 | """Protect against infinitesimal heights and associated high velocities |
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| 461 | """ |
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| 462 | |
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| 463 | #Shortcuts |
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| 464 | wc = domain.quantities['stage'].centroid_values |
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| 465 | zc = domain.quantities['elevation'].centroid_values |
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| 466 | xmomc = domain.quantities['xmomentum'].centroid_values |
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| 467 | hc = wc - zc #Water depths at centroids |
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| 468 | |
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| 469 | zv = domain.quantities['elevation'].vertex_values |
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| 470 | wv = domain.quantities['stage'].vertex_values |
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| 471 | hv = wv-zv |
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| 472 | xmomv = domain.quantities['xmomentum'].vertex_values |
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| 473 | #remove the above two lines and corresponding code below |
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| 474 | |
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| 475 | #Update |
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| 476 | for k in range(domain.number_of_elements): |
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| 477 | |
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| 478 | if hc[k] < domain.minimum_allowed_height: |
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| 479 | #Control stage |
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| 480 | if hc[k] < domain.epsilon: |
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| 481 | wc[k] = zc[k] # Contain 'lost mass' error |
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| 482 | wv[k,0] = zv[k,0] |
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| 483 | wv[k,1] = zv[k,1] |
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| 484 | |
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| 485 | xmomc[k] = 0.0 |
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| 486 | |
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| 487 | |
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| 488 | |
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| 489 | |
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| 490 | |
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| 491 | ######################### |
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| 492 | #Standard forcing terms: |
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| 493 | # |
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| 494 | def gravity(domain): |
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| 495 | """Apply gravitational pull in the presence of bed slope |
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| 496 | """ |
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| 497 | |
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| 498 | from util import gradient |
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| 499 | from Numeric import Float |
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| 500 | from numpy import zeros, array, sum |
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| 501 | |
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| 502 | xmom = domain.quantities['xmomentum'].explicit_update |
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| 503 | stage = domain.quantities['stage'].explicit_update |
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| 504 | |
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| 505 | Stage = domain.quantities['stage'] |
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| 506 | Elevation = domain.quantities['elevation'] |
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| 507 | h = Stage.vertex_values - Elevation.vertex_values |
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| 508 | b = Elevation.vertex_values |
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| 509 | w = Stage.vertex_values |
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| 510 | |
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| 511 | x = domain.get_vertex_coordinates() |
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| 512 | g = domain.g |
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| 513 | |
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| 514 | for k in range(domain.number_of_elements): |
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| 515 | avg_h = sum( h[k,:] )/2 |
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| 516 | |
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| 517 | #Compute bed slope |
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| 518 | x0, x1 = x[k,:] |
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| 519 | b0, b1 = b[k,:] |
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| 520 | |
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| 521 | w0, w1 = w[k,:] |
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| 522 | wx = gradient(x0, x1, w0, w1) |
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| 523 | bx = gradient(x0, x1, b0, b1) |
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| 524 | |
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| 525 | #Update momentum (explicit update is reset to source values) |
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| 526 | xmom[k] += -g*bx*avg_h |
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| 527 | |
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| 528 | def gravity_F2(domain): |
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| 529 | """Apply gravitational pull in the presence of bed slope |
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| 530 | """ |
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| 531 | |
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| 532 | from util import gradient |
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| 533 | from Numeric import Float |
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| 534 | from numpy import zeros, array, sum |
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| 535 | from parameters import F2#This is an additional friction!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! |
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| 536 | |
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| 537 | xmom = domain.quantities['xmomentum'].explicit_update |
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| 538 | stage = domain.quantities['stage'].explicit_update |
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| 539 | |
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| 540 | Stage = domain.quantities['stage'] |
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| 541 | Elevation = domain.quantities['elevation'] |
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| 542 | h = Stage.vertex_values - Elevation.vertex_values |
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| 543 | b = Elevation.vertex_values |
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| 544 | w = Stage.vertex_values |
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| 545 | |
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| 546 | x = domain.get_vertex_coordinates() |
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| 547 | g = domain.g |
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| 548 | |
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| 549 | for k in range(domain.number_of_elements): |
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| 550 | avg_h = sum( h[k,:] )/2 |
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| 551 | |
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| 552 | #Compute bed slope |
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| 553 | x0, x1 = x[k,:] |
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| 554 | b0, b1 = b[k,:] |
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| 555 | |
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| 556 | w0, w1 = w[k,:] |
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| 557 | wx = gradient(x0, x1, w0, w1) |
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| 558 | bx = gradient(x0, x1, b0, b1) |
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| 559 | |
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| 560 | #Update momentum (explicit update is reset to source values) |
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| 561 | xmom[k] += -g*bx*avg_h + avg_h*F2#This is an additional friction!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! |
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| 562 | |
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| 563 | |
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| 564 | def manning_friction(domain): |
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| 565 | """Apply (Manning) friction to water momentum |
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| 566 | """ |
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| 567 | |
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| 568 | from math import sqrt |
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| 569 | |
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| 570 | w = domain.quantities['stage'].centroid_values |
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| 571 | z = domain.quantities['elevation'].centroid_values |
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| 572 | h = w-z |
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| 573 | |
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| 574 | uh = domain.quantities['xmomentum'].centroid_values |
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| 575 | eta = domain.quantities['friction'].centroid_values |
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| 576 | |
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| 577 | xmom_update = domain.quantities['xmomentum'].semi_implicit_update |
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| 578 | |
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| 579 | N = domain.number_of_elements |
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| 580 | eps = domain.minimum_allowed_height |
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| 581 | g = domain.g |
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| 582 | |
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| 583 | for k in range(N): |
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| 584 | if eta[k] >= eps: |
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| 585 | if h[k] >= eps: |
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| 586 | S = -g * eta[k]**2 * uh[k] |
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| 587 | S /= h[k]**(7.0/3) |
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| 588 | |
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| 589 | #Update momentum |
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| 590 | xmom_update[k] += S*uh[k] |
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