/[escript]/trunk/modellib/py_src/flow.py
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Annotation of /trunk/modellib/py_src/flow.py

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Revision 628 - (hide annotations)
Thu Mar 23 02:27:57 2006 UTC (14 years, 7 months ago) by elspeth
File MIME type: text/x-python
File size: 4348 byte(s)
Copyright information added.

1 jgs 144 # $Id$
2    
3 elspeth 628 __copyright__=""" Copyright (c) 2006 by ACcESS MNRF
4     http://www.access.edu.au
5     Primary Business: Queensland, Australia"""
6     __license__="""Licensed under the Open Software License version 3.0
7     http://www.opensource.org/licenses/osl-3.0.php"""
8    
9 jgs 149 from esys.escript import *
10     from esys.escript.modelframe import Model,IterationDivergenceError
11     from esys.escript.linearPDEs import LameEquation
12 jgs 144
13     class SteadyIncompressibleFlow(Model):
14 jgs 147 """
15 jgs 144
16 jgs 149 M{-\left(\eta\left(v_{i,j}+v_{j,i}\right)\right)_{,j}+p_{,i}=F_i}
17    
18     M{\sigma_{ij}=2\eta D_{ij}-p\,\delta_{ij}}
19 jgs 144
20 jgs 149 M{D_{ij}=\frac{1}{2}\left( v_{j,i} + v_{i,j }\right)}
21    
22     M{v_{k,k} = 0}
23 jgs 144
24     """
25    
26     def __init__(self,debug=False):
27 jgs 149 """
28     set up model
29     """
30 jgs 144 Model.__init__(self,debug=debug)
31     self.declareParameter(domain=None, \
32     velocity=0., \
33     pressure=0., \
34 jgs 147 viscosity=1., \
35 jgs 144 internal_force=0., \
36 jgs 147 location_prescribed_velocity=Data(), \
37     prescribed_velocity=Data(), \
38     rel_tol=1.e-3,abs_tol=0.,max_iter=10,relaxation=0.001)
39 jgs 144 self.__iter=0
40    
41 jgs 147 def doInitialization(self):
42 jgs 149 """
43     initialize model
44     """
45 jgs 147 self.__p_old=None
46     self.__p_very_old=None
47     self.__dt_old=None
48 jgs 144 self.__pde=LameEquation(self.domain)
49    
50     def stress(self):
51 jgs 149 """
52     returns current stress"""
53 jgs 147 return 2*self.viscosity*self.stretching-self.pressure*kronecker(self.domain)
54 jgs 144
55     def stretching(self):
56 jgs 149 """
57     returns stertching tensor
58     """
59 jgs 144 g=grad(self.velocity)
60     return (g+transpose(g))/2
61 jgs 147
62     def doStepPreprocessing(self,dt):
63 jgs 144 """
64 jgs 149 step up pressure iteration
65 jgs 144
66 jgs 149 if run within a time dependend problem extrapolation of pressure from previous time steps is used to
67     get an initial guess (that needs some work!!!!!!!)
68 jgs 144 """
69 jgs 147 self.__iter=0
70     self.__diff=1.e40
71     if not self.__p_old==None:
72     if self.__p_very_old==None:
73     self.pressure=self.__p_old
74     else:
75     self.pressure=(1.+dt/self.__dt_old)*self.__p_old-dt/self.__dt_old*self.__p_very_old
76 jgs 144
77 jgs 147 def doStep(self,dt):
78 jgs 144 """
79    
80 jgs 149 performs an iteration step of the penalty method.
81     IterationDivergenceError is raised if pressure error cannot be reduced or max_iter is reached.
82 jgs 144
83     """
84     penalty=self.viscosity/self.relaxation
85 jgs 147 self.__pde.setValue(lame_mu=self.viscosity, \
86     lame_lambda=penalty, \
87     F=self.internal_force, \
88     sigma=self.pressure*kronecker(self.__pde.getDomain()), \
89     r=self.prescribed_velocity, \
90     q=self.location_prescribed_velocity)
91     self.__pde.setTolerance(self.rel_tol/10.)
92     self.velocity=self.__pde.getSolution()
93 jgs 144 update=penalty*div(self.velocity)
94     self.pressure=self.pressure-update
95 jgs 147 self.__diff,diff_old=Lsup(update),self.__diff
96     self.__iter+=1
97     self.trace("velocity range %e:%e"%(inf(self.velocity),sup(self.velocity)))
98     self.trace("pressure range %e:%e"%(inf(self.pressure),sup(self.pressure)))
99     self.trace("pressure correction: %e"%self.__diff)
100     if self.__iter>2 and diff_old<self.__diff:
101     self.trace("Pressure iteration failed!")
102 jgs 144 raise IterationDivergenceError,"no improvement in pressure iteration"
103 jgs 147 if self.__iter>self.max_iter:
104     raise IterationDivergenceError,"Maximum number of iterations steps reached"
105 jgs 144
106 jgs 147 def terminateIteration(self):
107     """iteration is terminateIterationd if relative pressure change is less then rel_tol"""
108     return self.__diff<=self.rel_tol*Lsup(self.pressure)+self.abs_tol
109 jgs 144
110 jgs 147 def doStepPostprocessing(self,dt):
111     self.__dt_old=dt
112     self.__p_old,self.__p_very_old=self.pressure,self.__p_old

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