modellib/py_src/flow.py

# $Id$

__copyright__="""  Copyright (c) 2006 by ACcESS MNRF
                    http://www.access.edu.au
                Primary Business: Queensland, Australia"""
__license__="""Licensed under the Open Software License version 3.0
             http://www.opensource.org/licenses/osl-3.0.php"""

from esys.escript import *
from esys.escript.modelframe import Model,IterationDivergenceError
from esys.escript.linearPDEs import LameEquation

class SteadyIncompressibleFlow(Model):
       """

       M{-\left(\eta\left(v_{i,j}+v_{j,i}\right)\right)_{,j}+p_{,i}=F_i}
       
       M{\sigma_{ij}=2\eta D_{ij}-p\,\delta_{ij}}

       M{D_{ij}=\frac{1}{2}\left( v_{j,i} + v_{i,j }\right)}
       
       M{v_{k,k} = 0}

       """

       def __init__(self,debug=False):
           """
           set up model
           """
           Model.__init__(self,debug=debug)
           self.declareParameter(domain=None, \
                                 velocity=0., \
                                 pressure=0., \
                                 viscosity=1., \
                                 internal_force=0., \
                                 location_prescribed_velocity=Data(), \
                                 prescribed_velocity=Data(), \
                                 rel_tol=1.e-3,abs_tol=0.,max_iter=10,relaxation=0.0001)
           self.__iter=0

       def doInitialization(self):
           """
           initialize model
           """
           self.__p_old=None
           self.__p_very_old=None
           self.__dt_old=None
           self.__pde=LameEquation(self.domain)
           self.__pde.setSolverMethod(LameEquation.DIRECT)

       def stress(self):
           """
           returns current stress"""
           return 2*self.viscosity*self.stretching-self.pressure*kronecker(self.domain)

       def stretching(self):
           """
           returns stertching tensor
           """
           g=grad(self.velocity)
           return (g+transpose(g))/2

       def doStepPreprocessing(self,dt):
            """
            step up pressure iteration

            if run within a time dependend problem extrapolation of pressure from previous time steps is used to
            get an initial guess (that needs some work!!!!!!!)
            """
            self.__iter=0
            self.__diff=1.e40
            if not self.__p_old==None:
               if self.__p_very_old==None:
                  self.pressure=self.__p_old
               else:
                  self.pressure=(1.+dt/self.__dt_old)*self.__p_old-dt/self.__dt_old*self.__p_very_old

       def doStep(self,dt):
          """

          performs an iteration step of the penalty method.
          IterationDivergenceError is raised if pressure error cannot be reduced or max_iter is reached.

          """
          penalty=self.viscosity/self.relaxation
          self.__pde.setValue(lame_mu=self.viscosity, \
                              lame_lambda=penalty, \
                              F=self.internal_force, \
                              sigma=self.pressure*kronecker(self.__pde.getDomain()), \
                              r=self.prescribed_velocity, \
                              q=self.location_prescribed_velocity)
          self.__pde.setTolerance(self.rel_tol/10.)
          self.velocity=self.__pde.getSolution()
          update=penalty*div(self.velocity)
          self.pressure=self.pressure-update
          self.__diff,diff_old=Lsup(update),self.__diff
          self.__iter+=1
          self.trace("velocity range %e:%e"%(inf(self.velocity),sup(self.velocity)))
          self.trace("pressure range %e:%e"%(inf(self.pressure),sup(self.pressure)))
          self.trace("pressure correction: %e"%self.__diff)
          if self.__iter>2 and diff_old<self.__diff:
              self.trace("Pressure iteration failed!")
              raise IterationDivergenceError,"no improvement in pressure iteration"
          if self.__iter>self.max_iter:
              raise IterationDivergenceError,"Maximum number of iterations steps reached"

       def terminateIteration(self):
          """iteration is terminateIterationd if relative pressure change is less then rel_tol"""
          return self.__diff<=self.rel_tol*Lsup(self.pressure)+self.abs_tol

       def doStepPostprocessing(self,dt):
          self.__dt_old=dt
          self.__p_old,self.__p_very_old=self.pressure,self.__p_old
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=0.0001)
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	self.__pde.setSolverMethod(LameEquation.DIRECT)
50
51	def stress(self):
52	"""
53	returns current stress"""
54	return 2self.viscosityself.stretching-self.pressure*kronecker(self.domain)
55
56	def stretching(self):
57	"""
58	returns stertching tensor
59	"""
60	g=grad(self.velocity)
61	return (g+transpose(g))/2
62
63	def doStepPreprocessing(self,dt):
64	"""
65	step up pressure iteration
66
67	if run within a time dependend problem extrapolation of pressure from previous time steps is used to
68	get an initial guess (that needs some work!!!!!!!)
69	"""
70	self.__iter=0
71	self.__diff=1.e40
72	if not self.__p_old==None:
73	if self.__p_very_old==None:
74	self.pressure=self.__p_old
75	else:
76	self.pressure=(1.+dt/self.__dt_old)self.__p_old-dt/self.__dt_oldself.__p_very_old
77
78	def doStep(self,dt):
79	"""
80
81	performs an iteration step of the penalty method.
82	IterationDivergenceError is raised if pressure error cannot be reduced or max_iter is reached.
83
84	"""
85	penalty=self.viscosity/self.relaxation
86	self.__pde.setValue(lame_mu=self.viscosity, \
87	lame_lambda=penalty, \
88	F=self.internal_force, \
89	sigma=self.pressure*kronecker(self.__pde.getDomain()), \
90	r=self.prescribed_velocity, \
91	q=self.location_prescribed_velocity)
92	self.__pde.setTolerance(self.rel_tol/10.)
93	self.velocity=self.__pde.getSolution()
94	update=penalty*div(self.velocity)
95	self.pressure=self.pressure-update
96	self.__diff,diff_old=Lsup(update),self.__diff
97	self.__iter+=1
98	self.trace("velocity range %e:%e"%(inf(self.velocity),sup(self.velocity)))
99	self.trace("pressure range %e:%e"%(inf(self.pressure),sup(self.pressure)))
100	self.trace("pressure correction: %e"%self.__diff)
101	if self.__iter>2 and diff_old<self.__diff:
102	self.trace("Pressure iteration failed!")
103	raise IterationDivergenceError,"no improvement in pressure iteration"
104	if self.__iter>self.max_iter:
105	raise IterationDivergenceError,"Maximum number of iterations steps reached"
106
107	def terminateIteration(self):
108	"""iteration is terminateIterationd if relative pressure change is less then rel_tol"""
109	return self.__diff<=self.rel_tol*Lsup(self.pressure)+self.abs_tol
110
111	def doStepPostprocessing(self,dt):
112	self.__dt_old=dt
113	self.__p_old,self.__p_very_old=self.pressure,self.__p_old
Name	Value
svn:eol-style	native
svn:keywords	Author Date Id Revision