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

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Revision 147 - (show annotations)
Fri Aug 12 01:45:47 2005 UTC (14 years, 6 months ago) by jgs
Original Path: trunk/esys2/modellib/py_src/flow.py
File MIME type: text/x-python
File size: 4221 byte(s)
erge of development branch dev-02 back to main trunk on 2005-08-12

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

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