# Contents of /trunk/modellib/py_src/flow.py

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 1 # $Id$ 2 3 __copyright__=""" Copyright (c) 2006 by ACcESS MNRF 4 5 Primary Business: Queensland, Australia""" 6 __license__="""Licensed under the Open Software License version 3.0 7 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_oldself.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

## Properties

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