Commit c47614d9 authored by Martin Bauer's avatar Martin Bauer
Browse files

Added entropic SRT method

-> equilibrium is constructed according to maximum entropy principle
-> many sqrts in equilibrium formulation
parent 7f4fce4a
......@@ -623,7 +623,7 @@ class SteadyStateChapmanEnskogAnalysis(object):
spatialDerivativeOrders=None, # do not expand the differential operator itself
pdfs=(['f', 0, order + 1],)) # expand only the 'f' terms
self.scaleHierarchy = [-B * epsDict[i] for i in range(0, 5)]
self.scaleHierarchy = [-B * epsDict[i] for i in range(0, order+1)]
self.scaleHierarchyRaw = self.scaleHierarchy.copy()
expandedPdfs = [feq, self.scaleHierarchy[1]]
......@@ -145,6 +145,7 @@ from functools import partial
from lbmpy.methods import createSRT, createTRT, createOrthogonalMRT, createKBCTypeTRT, \
createRawMRT, createThreeRelaxationRateMRT
from lbmpy.methods.entropic import addIterativeEntropyCondition, addEntropyCondition
from lbmpy.methods.entropic_eq_srt import createEntropicSRT
from lbmpy.methods.relaxationrates import relaxationRateFromMagicNumber
from lbmpy.stencils import getStencil
import lbmpy.forcemodels as forceModels
......@@ -406,6 +407,8 @@ def createLatticeBoltzmannMethod(**params):
raise NotImplementedError("KBC type TRT methods can only be constructed for D2Q9 and D3Q27 stencils")
methodNr = methodName[-1]
method = createKBCTypeTRT(dim, relaxationRates[0], relaxationRates[1], 'KBC-N' + methodNr, **commonParams)
elif methodName.lower() == 'entropic-srt':
method = createEntropicSRT(stencil, relaxationRates[0], forceModel, params['compressible'])
raise ValueError("Unknown method %s" % (methodName,))
import sympy as sp
from lbmpy.maxwellian_equilibrium import getWeights
from lbmpy.methods.abstractlbmethod import AbstractLbMethod, LbmCollisionRule
from lbmpy.methods.conservedquantitycomputation import DensityVelocityComputation
class EntropicEquilibriumSRT(AbstractLbMethod):
def __init__(self, stencil, relaxationRate, forceModel, conservedQuantityCalculation):
super(EntropicEquilibriumSRT, self).__init__(stencil)
self._cqc = conservedQuantityCalculation
self._weights = getWeights(stencil, c_s_sq=sp.Rational(1, 3))
self._relaxationRate = relaxationRate
self._forceModel = forceModel
self.shearRelaxationRate = relaxationRate
def conservedQuantityComputation(self):
return self._cqc
def weights(self):
return self._weights
def zerothOrderEquilibriumMomentSymbol(self, ):
return self._cqc.zerothOrderMomentSymbol
def firstOrderEquilibriumMomentSymbols(self, ):
return self._cqc.firstOrderMomentSymbols
def getEquilibrium(self, conservedQuantityEquations=None, includeForceTerms=False):
return self._getCollisionRuleWithRelaxationRate(1, conservedQuantityEquations=conservedQuantityEquations,
def _getCollisionRuleWithRelaxationRate(self, relaxationRate, includeForceTerms=True,
f = sp.Matrix(self.preCollisionPdfSymbols)
rho = self._cqc.zerothOrderMomentSymbol
u = self._cqc.firstOrderMomentSymbols
if conservedQuantityEquations is None:
conservedQuantityEquations = self._cqc.equilibriumInputEquationsFromPdfs(f)
allSubexpressions = conservedQuantityEquations.allEquations
eq = []
for w_i, direction in zip(self.weights, self.stencil):
f_i = rho * w_i
for u_a, e_ia in zip(u, direction):
B = sp.sqrt(1 + 3 * u_a ** 2)
f_i *= (2 - B) * ((2 * u_a + B) / (1 - u_a)) ** e_ia
collisionEqs = [sp.Eq(lhs, (1 - relaxationRate) * f_i + relaxationRate * eq_i)
for lhs, f_i, eq_i in zip(self.postCollisionPdfSymbols, self.preCollisionPdfSymbols, eq)]
if (self._forceModel is not None) and includeForceTerms:
forceModelTerms = self._forceModel(self)
forceTermSymbols = sp.symbols("forceTerm_:%d" % (len(forceModelTerms, )))
forceSubexpressions = [sp.Eq(sym, forceModelTerm)
for sym, forceModelTerm in zip(forceTermSymbols, forceModelTerms)]
allSubexpressions += forceSubexpressions
collisionEqs = [sp.Eq(eq.lhs, eq.rhs + forceTermSymbol)
for eq, forceTermSymbol in zip(collisionEqs, forceTermSymbols)]
return LbmCollisionRule(self, collisionEqs, allSubexpressions)
def getCollisionRule(self):
return self._getCollisionRuleWithRelaxationRate(self._relaxationRate)
def createEntropicSRT(stencil, relaxationRate, forceModel, compressible):
if not compressible:
raise NotImplementedError("entropic-srt only implemented for compressible models")
densityVelocityComputation = DensityVelocityComputation(stencil, compressible, forceModel)
return EntropicEquilibriumSRT(stencil, relaxationRate, forceModel, densityVelocityComputation)
......@@ -27,6 +27,9 @@ def getShearRelaxationRate(method):
Shear moments in 3D are: x*y, x*z and y*z - in 2D its only x*y
The shear relaxation rate determines the viscosity in hydrodynamic LBM schemes
if hasattr(method, 'shearRelaxationRate'):
return method.shearRelaxationRate
relaxationRates = set()
for moment, relaxInfo in method.relaxationInfoDict.items():
if isShearMoment(moment):
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