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

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Revision 628 - (show 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 # $Id$
2
3 __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 from esys.escript import *
10 from esys.escript.modelframe import Model,IterationDivergenceError
11 from esys.escript.linearPDEs import LameEquation
12
13 class SteadyIncompressibleFlow(Model):
14 """
15
16 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
20 M{D_{ij}=\frac{1}{2}\left( v_{j,i} + v_{i,j }\right)}
21
22 M{v_{k,k} = 0}
23
24 """
25
26 def __init__(self,debug=False):
27 """
28 set up model
29 """
30 Model.__init__(self,debug=debug)
31 self.declareParameter(domain=None, \
32 velocity=0., \
33 pressure=0., \
34 viscosity=1., \
35 internal_force=0., \
36 location_prescribed_velocity=Data(), \
37 prescribed_velocity=Data(), \
38 rel_tol=1.e-3,abs_tol=0.,max_iter=10,relaxation=0.001)
39 self.__iter=0
40
41 def doInitialization(self):
42 """
43 initialize model
44 """
45 self.__p_old=None
46 self.__p_very_old=None
47 self.__dt_old=None
48 self.__pde=LameEquation(self.domain)
49
50 def stress(self):
51 """
52 returns current stress"""
53 return 2*self.viscosity*self.stretching-self.pressure*kronecker(self.domain)
54
55 def stretching(self):
56 """
57 returns stertching tensor
58 """
59 g=grad(self.velocity)
60 return (g+transpose(g))/2
61
62 def doStepPreprocessing(self,dt):
63 """
64 step up pressure iteration
65
66 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 """
69 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
77 def doStep(self,dt):
78 """
79
80 performs an iteration step of the penalty method.
81 IterationDivergenceError is raised if pressure error cannot be reduced or max_iter is reached.
82
83 """
84 penalty=self.viscosity/self.relaxation
85 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 update=penalty*div(self.velocity)
94 self.pressure=self.pressure-update
95 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 raise IterationDivergenceError,"no improvement in pressure iteration"
103 if self.__iter>self.max_iter:
104 raise IterationDivergenceError,"Maximum number of iterations steps reached"
105
106 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
110 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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