source: trunk/anuga_work/development/2010-projects/anuga_1d/channel/channel_domain.py @ 7884

"""Class Domain -
1D interval domains for finite-volume computations of
the shallow water wave equation.

This module contains a specialisation of class Generic_domain from module
generic_domain.py
consisting of methods specific to Channel flow using the Shallow Water Wave Equation

This particular modification of the Domain class implements the ability to
vary the width of the 1D channel that the water flows in. As a result the
conserved variables are different than previous implementations and so are the
equations.

U_t + E_x = S

where

U = [A, Q] = [b*h, u*b*h]
E = [Q, Q^2/A + g*b*h^2/2]
S represents source terms forcing the system
(e.g. gravity, boundary_stree, friction, wind stress, ...)
gravity = -g*b*h*z_x
boundary_stress = 1/2*g*b_x*h^2

and _t, _x, _y denote the derivative with respect to t, x and y respectiely.

The quantities are

symbol    variable name    explanation
A         area             Wetted area = b*h
Q         discharge        flux of water = u*b*h
x         x                horizontal distance from origin [m]
z         elevation        elevation of bed on which flow is modelled [m]
h         height           water height above z [m]
w         stage            absolute water level, w = z+h [m]
u                          speed in the x direction [m/s]
uh        xmomentum        momentum in the x direction [m^2/s]
b         width            width of channel
eta                        mannings friction coefficient [to appear]
nu                         wind stress coefficient [to appear]

The conserved quantities are A, Q
--------------------------------------------------------------------------
For details see e.g.
Christopher Zoppou and Stephen Roberts,
Catastrophic Collapse of Water Supply Reservoirs in Urban Areas,
Journal of Hydraulic Engineering, vol. 127, No. 7 July 1999


John Jakeman, Ole Nielsen, Stephen Roberts, Duncan Gray, Christopher Zoppou,
Padarn Wilson, Geoscience Australia, 2008
"""


from anuga_1d.base.generic_domain import *
import numpy


#Shallow water domain
class Domain(Generic_domain):

    def __init__(self, coordinates, boundary = None, tagged_elements = None):

        conserved_quantities = ['area', 'discharge']
        evolved_quantities = ['area', 'discharge', 'elevation', 'height', 'velocity','width','stage']
        other_quantities = ['friction']
        Generic_domain.__init__(self,
                                coordinates = coordinates,
                                boundary = boundary,
                                conserved_quantities = conserved_quantities,
                                evolved_quantities = evolved_quantities,
                                other_quantities = other_quantities,
                                tagged_elements = tagged_elements)
        
        from anuga_1d.config import minimum_allowed_height, g, h0
        self.minimum_allowed_height = minimum_allowed_height
        self.g = g
        self.h0 = h0
        self.setstageflag = False
        self.discontinousb = False


        # forcing terms gravity and boundary stress are included in the flux calculation
        #self.forcing_terms.append(gravity)
        #self.forcing_terms.append(boundary_stress)
        #self.forcing_terms.append(manning_friction)
       

        
        #Stored output
        self.store = True
        self.format = 'sww'
        self.smooth = True

        
        #Reduction operation for get_vertex_values
        from anuga_1d.base.util import mean
        self.reduction = mean
        #self.reduction = min  #Looks better near steep slopes

        self.set_quantities_to_be_stored(['area','discharge'])

        self.__doc__ = 'channel_domain'

        self.check_integrity()


    def check_integrity(self):

        #Check that we are solving the shallow water wave equation

        msg = 'First conserved quantity must be "area"'
        assert self.conserved_quantities[0] == 'area', msg
        msg = 'Second conserved quantity must be "discharge"'
        assert self.conserved_quantities[1] == 'discharge', msg

        msg = 'First evolved quantity must be "area"'
        assert self.evolved_quantities[0] == 'area', msg
        msg = 'Second evolved quantity must be "discharge"'
        assert self.evolved_quantities[1] == 'discharge', msg
        msg = 'Third evolved quantity must be "elevation"'
        assert self.evolved_quantities[2] == 'elevation', msg
        msg = 'Fourth evolved quantity must be "height"'
        assert self.evolved_quantities[3] == 'height', msg
        msg = 'Fifth evolved quantity must be "velocity"'
        assert self.evolved_quantities[4] == 'velocity', msg
        msg = 'Sixth evolved quantity must be "width"'
        assert self.evolved_quantities[5] == 'width', msg
        msg = 'Seventh evolved quantity must be "stage"'
        assert self.evolved_quantities[6] == 'stage', msg

        Generic_domain.check_integrity(self)

    def compute_fluxes(self):
        #Call correct module function
        #(either from this module or C-extension)
        compute_fluxes_channel(self)

    def distribute_to_vertices_and_edges(self):
        #Call correct module function
        #(either from this module or C-extension)
        distribute_to_vertices_and_edges_limit_a_d(self)
        

#=============== End of Channel Domain ===============================

#-----------------------------------
# Compute flux definition with channel
#-----------------------------------
def compute_fluxes_channel(domain):
    import sys
    timestep = float(sys.maxint)

    area       = domain.quantities['area']
    discharge  = domain.quantities['discharge']
    bed        = domain.quantities['elevation']
    height     = domain.quantities['height']
    velocity   = domain.quantities['velocity']
    width      = domain.quantities['width']


    from anuga_1d.channel.channel_domain_ext import compute_fluxes_channel_ext
    domain.flux_timestep = compute_fluxes_channel_ext(timestep,domain,area,discharge,bed,height,velocity,width)

#-----------------------------------------------------------------------
# Distribute to verticies with stage reconstructed and then extrapolated
#-----------------------------------------------------------------------
def distribute_to_vertices_and_edges_limit_a_d(domain):
    
    #Remove very thin layers of water
    #protect_against_infinitesimal_and_negative_heights(domain)  



    import sys
    from anuga_1d.config import epsilon, h0

    
    N = domain.number_of_elements

    #Shortcuts
    area      = domain.quantities['area']
    discharge = domain.quantities['discharge']
    bed       = domain.quantities['elevation']
    height    = domain.quantities['height']
    velocity  = domain.quantities['velocity']
    width     = domain.quantities['width']
    stage     = domain.quantities['stage']

    #Arrays   
    a_C   = area.centroid_values
    d_C   = discharge.centroid_values
    z_C   = bed.centroid_values
    h_C   = height.centroid_values
    u_C   = velocity.centroid_values
    b_C   = width.centroid_values
    w_C   = stage.centroid_values

    if domain.setstageflag:
        a_C[:,] = (w_C-z_C)*b_C
        domain.setstageflag = False

    if domain.discontinousb:
        width.extrapolate_second_order()
        

    h0 = 1.0e-12

    h_C[:] = numpy.where( (a_C>h0) | (b_C>h0), a_C/(b_C+h0/b_C), 0.0 )
    u_C[:] = numpy.where( (a_C>h0) | (b_C>h0), d_C/(a_C+h0/a_C), 0.0 )

    a_C[:] = numpy.where( (a_C>h0) | (b_C>h0), a_C, 0.0 )
    b_C[:] = numpy.where( (a_C>h0) | (b_C>h0), b_C, 0.0 )
    d_C[:] = numpy.where( (a_C>h0) | (b_C>h0), d_C, 0.0 )

    w_C[:] = h_C + z_C
    
                

    bed.extrapolate_second_order()
    
    for name in ['velocity','stage']:
        Q = domain.quantities[name]
        if domain.order == 1:
            Q.extrapolate_first_order()
        elif domain.order == 2:
            Q.extrapolate_second_order()
        else:
            raise 'Unknown order'


    a_V  = area.vertex_values
    w_V  = stage.vertex_values
    z_V  = bed.vertex_values
    h_V  = height.vertex_values
    u_V  = velocity.vertex_values
    d_V  = discharge.vertex_values
    b_V  = width.vertex_values


    h_V[:] = w_V-z_V

    w_V[:] = numpy.where(h_V > h0, w_V, z_V)
    h_V[:] = numpy.where(h_V > h0, h_V, 0.0)
    a_V[:] = b_V*h_V
    d_V[:] = u_V*a_V

    
    return


#--------------------------------------------------------
#Boundaries - specific to the channel_domain
#--------------------------------------------------------
class Reflective_boundary(Boundary):
    """Reflective boundary returns same conserved quantities as
    those present in its neighbour volume but reflected.

    This class is specific to the shallow water equation as it
    works with the momentum quantities assumed to be the second
    and third conserved quantities.
    """

    def __init__(self, domain = None):
        Boundary.__init__(self)

        if domain is None:
            msg = 'Domain must be specified for reflective boundary'
            raise msg

        #Handy shorthands
        self.normals  = domain.normals
        self.area     = domain.quantities['area'].vertex_values
        self.discharge     = domain.quantities['discharge'].vertex_values
        self.bed      = domain.quantities['elevation'].vertex_values
        self.height   = domain.quantities['height'].vertex_values
        self.velocity = domain.quantities['velocity'].vertex_values
        self.width    = domain.quantities['width'].vertex_values
        self.stage    = domain.quantities['stage'].vertex_values

        self.evolved_quantities = numpy.zeros(7, numpy.float)

    def __repr__(self):
        return 'Reflective_boundary'


    def evaluate(self, vol_id, edge_id):
        """Reflective boundaries reverses the outward momentum
        of the volume they serve.
        """

        q = self.evolved_quantities
        q[0] =  self.area[vol_id, edge_id]
        q[1] = -self.discharge[vol_id, edge_id]
        q[2] =  self.bed[vol_id, edge_id]
        q[3] =  self.height[vol_id, edge_id]
        q[4] = -self.velocity[vol_id, edge_id]
        q[5] =  self.width[vol_id,edge_id]
        q[6] =  self.stage[vol_id,edge_id]

        return q

class Dirichlet_boundary(Boundary):
    """Dirichlet boundary returns constant values for the
    conserved quantities
if k>5 and k<15:
            print discharge_ud[k],-g*zx*avg_h*avg_b
        discharge_ud[k] +=-g*zx*avg_h*avg_b    """


    def __init__(self, evolved_quantities=None):
        Boundary.__init__(self)

        if evolved_quantities is None:
            msg = 'Must specify one value for each evolved quantity'
            raise msg

        assert len(evolved_quantities) == 7

        self.evolved_quantities=numpy.array(evolved_quantities,numpy.float)

    def __repr__(self):
        return 'Dirichlet boundary (%s)' %self.evolved_quantities

    def evaluate(self, vol_id=None, edge_id=None):
        return self.evolved_quantities


#----------------------------
#Standard forcing terms:
#---------------------------
def gravity(domain):
    """Apply gravitational pull in the presence of bed slope
    """

    from util import gradient
    from Numeric import zeros, Float, array, sum



    Area      = domain.quantities['area']
    Discharge  = domain.quantities['discharge']
    Elevation = domain.quantities['elevation']
    Height    = domain.quantities['height']
    Width     = domain.quantities['width']

    discharge_ud  = Discharge.explicit_update


       
    h = Height.vertex_values
    b = Width.vertex_values
    a = Area.vertex_values
    z = Elevation.vertex_values

    x = domain.get_vertex_coordinates()
    g = domain.g
    for k in range(domain.number_of_elements):
        avg_h = 0.5*(h[k,0] + h[k,1])
        avg_b = 0.5*(b[k,0] + b[k,1])
        
        #Compute bed slope
        x0, x1 = x[k,:]
        z0, z1 = z[k,:]
        zx = gradient(x0, x1, z0, z1)
       
        #Update momentum (explicit update is reset to source values)
        discharge_ud[k]+= -g*zx*avg_h*avg_b
      

def boundary_stress(domain):

    from util import gradient
    from Numeric import zeros, Float, array, sum

    Area     = domain.quantities['area']
    Discharge  = domain.quantities['discharge']
    Elevation = domain.quantities['elevation']
    Height    = domain.quantities['height']
    Width     = domain.quantities['width']

    discharge_ud  = Discharge.explicit_update
 
    h = Height.vertex_values
    b = Width.vertex_values
    a = Area.vertex_values
    z = Elevation.vertex_values

    x = domain.get_vertex_coordinates()
    g = domain.g

    for k in range(domain.number_of_elements):
        avg_h = 0.5*(h[k,0] + h[k,1])
        

        #Compute bed slope
        x0, x1 = x[k,:]
        b0, b1 = b[k,:]
        bx = gradient(x0, x1, b0, b1)
        
        #Update momentum (explicit update is reset to source values)
        discharge_ud[k] += 0.5*g*bx*avg_h*avg_h
        #stage_ud[k] = 0.0
 
 
def manning_friction(domain):
    """Apply (Manning) friction to water momentum
    """

    from math import sqrt

    w = domain.quantities['stage'].centroid_values
    z = domain.quantities['elevation'].centroid_values
    h = w-z

    uh = domain.quantities['xmomentum'].centroid_values
    eta = domain.quantities['friction'].centroid_values

    xmom_update = domain.quantities['xmomentum'].semi_implicit_update

    N = domain.number_of_elements
    eps = domain.minimum_allowed_height
    g = domain.g

    for k in range(N):
        if eta[k] >= eps:
            if h[k] >= eps:
                #S = -g * eta[k]**2 * sqrt((uh[k]**2 + vh[k]**2))
                S = -g * eta[k]**2 * uh[k]
                S /= h[k]**(7.0/3)

                #Update momentum
                xmom_update[k] += S*uh[k]
                #ymom_update[k] += S*vh[k]

def linear_friction(domain):
    """Apply linear friction to water momentum

    Assumes quantity: 'linear_friction' to be present
    """

    from math import sqrt

    w = domain.quantities['stage'].centroid_values
    z = domain.quantities['elevation'].centroid_values
    h = w-z

    uh = domain.quantities['xmomentum'].centroid_values
    tau = domain.quantities['linear_friction'].centroid_values

    xmom_update = domain.quantities['xmomentum'].semi_implicit_update

    N = domain.number_of_elements
    eps = domain.minimum_allowed_height

    for k in range(N):
        if tau[k] >= eps:
            if h[k] >= eps:
                S = -tau[k]/h[k]

                #Update momentum
                xmom_update[k] += S*uh[k]




def linearb(domain):

    bC = domain.quantities['width'].vertex_values
    
    for i in range(len(bC)-1):
        temp= 0.5*(bC[i,1]+bC[i+1,0])
        bC[i,1]=temp
        bC[i+1,0]=temp