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• #1857
ivan
Member

Hello, everybody,rnrnCurrently I am working with the example Multicomponent2D and by changing some geometry and force aspects I was able to turn it into a simulation of a rising bubble of a lighter fluid in a heavier one, as explained in the topic “”Simulation of a Raising Droplet in a Channel- Help””, and now I would like to convert the whole simulation into physical units. My first thought was to implement an LBConverter class, so I got the archive “”cylinder2d.dat”” to have a look and a doubt came up:rnrn

Code:
LBconverter informationrnrncharacteristical valuesrn———————————————————————-rnDimension(d): dim=2rnCharacteristical length(m): charL=0.1rnCharacteristical speed(m/s): charU=0.2rnCharacteristical time(s): charT=0.5rnDensity factor(kg/m^d): charRho=1rnCharacterestical mass(kg): charMass=0.01rnCharacterestical force(N): charForce=0.004rnCharacterestical pressure(Pa): charPressure=0.04rnPressure level(Pa): pressureLevel=0rnPhys. kinematic viscosity(m^2/s): charNu=0.001rnPhys. dynamic viscosity(N*s/m^2): dynVisco=0.001rn======================================================================rnrnlattice valuesrn———————————————————————-rnDeltaX: deltaX=0.05rnLattice velocity: latticeU=0.02rnDeltaT: deltaT=0.001rnReynolds number: Re=20rnDimlessNu: dNu=0.05rnViscosity for computation: latticeNu=0.02rnRelaxation time: tau=0.56rnRelaxation frequency: omega=1.78571rn======================================================================rnrnconversion factorsrn———————————————————————-rnlatticeL(m): latticeL=0.005rnTime step (s): physTime=0.0005rnVelocity factor(m/s): physVelocity=10rnFlowRate factor(m^d/s): physFlowRate=0.05rnMass factor(kg): physMass=2.5e-05rnForce factor(N): physForce=0.5rnForce factor massless(N/kg): physMasslessForce=20000rnPressure factor(Pa): physPressure=100rnlatticePressure: latticeP=0.01

rnrnCan anybody explain why is latticeNu calculated this way?rnrnlatticeNu=charNu*latticeU/charU/latticeLrnrnBesides that, I was wondering how could I implement the LBconverter once in my example I have two different fluid? Would I have to implement two different ones? If so, how?rnrnrnBest regards,rnrnIvan

#2446
ivan
Member

Hello, everybody,rnrnCurrently I am working with the example Multicomponent2D and by changing some geometry and force aspects I was able to turn it into a simulation of a rising bubble of a lighter fluid in a heavier one, as explained in the topic “”Simulation of a Raising Droplet in a Channel- Help””, and now I would like to convert the whole simulation into physical units. My first thought was to implement an LBConverter class, so I got the archive “”cylinder2d.dat”” to have a look and a doubt came up:rnrn

Code:
LBconverter informationrnrncharacteristical valuesrn———————————————————————-rnDimension(d): dim=2rnCharacteristical length(m): charL=0.1rnCharacteristical speed(m/s): charU=0.2rnCharacteristical time(s): charT=0.5rnDensity factor(kg/m^d): charRho=1rnCharacterestical mass(kg): charMass=0.01rnCharacterestical force(N): charForce=0.004rnCharacterestical pressure(Pa): charPressure=0.04rnPressure level(Pa): pressureLevel=0rnPhys. kinematic viscosity(m^2/s): charNu=0.001rnPhys. dynamic viscosity(N*s/m^2): dynVisco=0.001rn======================================================================rnrnlattice valuesrn———————————————————————-rnDeltaX: deltaX=0.05rnLattice velocity: latticeU=0.02rnDeltaT: deltaT=0.001rnReynolds number: Re=20rnDimlessNu: dNu=0.05rnViscosity for computation: latticeNu=0.02rnRelaxation time: tau=0.56rnRelaxation frequency: omega=1.78571rn======================================================================rnrnconversion factorsrn———————————————————————-rnlatticeL(m): latticeL=0.005rnTime step (s): physTime=0.0005rnVelocity factor(m/s): physVelocity=10rnFlowRate factor(m^d/s): physFlowRate=0.05rnMass factor(kg): physMass=2.5e-05rnForce factor(N): physForce=0.5rnForce factor massless(N/kg): physMasslessForce=20000rnPressure factor(Pa): physPressure=100rnlatticePressure: latticeP=0.01

rnrnCan anybody explain why is latticeNu calculated this way?rnrnlatticeNu=charNu*latticeU/charU/latticeLrnrnBesides that, I was wondering how could I implement the LBconverter once in my example I have two different fluid? Would I have to implement two different ones? If so, how?rnrnrnBest regards,rnrnIvan

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