source: anuga_work/development/2010-projects/anuga_1d/sww/sww_forcing_terms.py @ 7839

Last change on this file since 7839 was 7839, checked in by steve, 12 years ago

Changing name of 1d projects so that it will be easy to moveto the trunk

File size: 4.5 KB
Line 
1#! /usr/bin/python
2
3
4"""
5Forcing terms for the shallow water equations, gravity, friction etc
6"""
7
8__author__="Stephen Roberts"
9__date__ ="$05/06/2010 5:49:35 PM$"
10
11
12def gravity(domain):
13    """Apply gravitational pull in the presence of bed slope
14    """
15
16    from flow_1d.utilities.util import gradient
17
18    xmom  = domain.quantities['xmomentum'].explicit_update
19    stage = domain.quantities['stage'].explicit_update
20#    ymom = domain.quantities['ymomentum'].explicit_update
21
22    Stage = domain.quantities['stage']
23    Elevation = domain.quantities['elevation']
24    #h = Stage.edge_values - Elevation.edge_values
25    h = Stage.vertex_values - Elevation.vertex_values
26    b = Elevation.vertex_values
27    w = Stage.vertex_values
28
29    x = domain.get_vertex_coordinates()
30    g = domain.g
31
32    for k in range(domain.number_of_elements):
33#        avg_h = sum( h[k,:] )/3
34        avg_h = sum( h[k,:] )/2
35
36        #Compute bed slope
37        #x0, y0, x1, y1, x2, y2 = x[k,:]
38        x0, x1 = x[k,:]
39        #z0, z1, z2 = v[k,:]
40        b0, b1 = b[k,:]
41
42        w0, w1 = w[k,:]
43        wx = gradient(x0, x1, w0, w1)
44
45        #zx, zy = gradient(x0, y0, x1, y1, x2, y2, z0, z1, z2)
46        bx = gradient(x0, x1, b0, b1)
47
48        #Update momentum (explicit update is reset to source values)
49        xmom[k] += -g*bx*avg_h
50        #xmom[k] = -g*bx*avg_h
51        #stage[k] = 0.0
52
53
54def manning_friction(domain):
55    """Apply (Manning) friction to water momentum
56    """
57
58    from math import sqrt
59
60    w = domain.quantities['stage'].centroid_values
61    z = domain.quantities['elevation'].centroid_values
62    h = w-z
63
64    uh = domain.quantities['xmomentum'].centroid_values
65    #vh = domain.quantities['ymomentum'].centroid_values
66    eta = domain.quantities['friction'].centroid_values
67
68    xmom_update = domain.quantities['xmomentum'].semi_implicit_update
69    #ymom_update = domain.quantities['ymomentum'].semi_implicit_update
70
71    N = domain.number_of_elements
72    eps = domain.minimum_allowed_height
73    g = domain.g
74
75    for k in range(N):
76        if eta[k] >= eps:
77            if h[k] >= eps:
78                #S = -g * eta[k]**2 * sqrt((uh[k]**2 + vh[k]**2))
79                S = -g * eta[k]**2 * uh[k]
80                S /= h[k]**(7.0/3)
81
82                #Update momentum
83                xmom_update[k] += S*uh[k]
84                #ymom_update[k] += S*vh[k]
85
86def linear_friction(domain):
87    """Apply linear friction to water momentum
88
89    Assumes quantity: 'linear_friction' to be present
90    """
91
92    from math import sqrt
93
94    w = domain.quantities['stage'].centroid_values
95    z = domain.quantities['elevation'].centroid_values
96    h = w-z
97
98    uh = domain.quantities['xmomentum'].centroid_values
99#    vh = domain.quantities['ymomentum'].centroid_values
100    tau = domain.quantities['linear_friction'].centroid_values
101
102    xmom_update = domain.quantities['xmomentum'].semi_implicit_update
103#    ymom_update = domain.quantities['ymomentum'].semi_implicit_update
104
105    N = domain.number_of_elements
106    eps = domain.minimum_allowed_height
107    g = domain.g #Not necessary? Why was this added?
108
109    for k in range(N):
110        if tau[k] >= eps:
111            if h[k] >= eps:
112                S = -tau[k]/h[k]
113
114                #Update momentum
115                xmom_update[k] += S*uh[k]
116 #              ymom_update[k] += S*vh[k]
117
118
119
120def check_forcefield(f):
121    """Check that f is either
122    1: a callable object f(t,x,y), where x and y are vectors
123       and that it returns an array or a list of same length
124       as x and y
125    2: a scalar
126    """
127
128
129    if callable(f):
130        #N = 3
131        N = 2
132        #x = ones(3, numpy.float)
133        #y = ones(3, numpy.float)
134        x = ones(2, numpy.float)
135        #y = ones(2, numpy.float)
136
137        try:
138            #q = f(1.0, x=x, y=y)
139            q = f(1.0, x=x)
140        except Exception, e:
141            msg = 'Function %s could not be executed:\n%s' %(f, e)
142            #FIXME: Reconsider this semantics
143            raise msg
144
145        try:
146            q = numpy.array(q, numpy.float)
147        except:
148            msg = 'Return value from vector function %s could ' %f
149            msg += 'not be converted into a numpy array of numpy.floats.\n'
150            msg += 'Specified function should return either list or array.'
151            raise msg
152
153        #Is this really what we want?
154        msg = 'Return vector from function %s ' %f
155        msg += 'must have same lenght as input vectors'
156        assert len(q) == N, msg
157
158    else:
159        try:
160            f = float(f)
161        except:
162            msg = 'Force field %s must be either a scalar' %f
163            msg += ' or a vector function'
164            raise msg
165    return f
166
167
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