coupling 3d simulations with 1d simulations (the water hammer …hani/kurser/os_cfd_2016/... ·...

Background Water Hammer 3D CFD Domain Preparations New Boundary Conditions Testing Coupled Simulations

Coupling 3D Simulations with 1D Simulations(The Water Hammer Effect)

Sudharsan Vasudevan

Department of Applied Mechanics,Chalmers University of Technology,

Gothenburg, Sweden

05 Dec 2016

Sudharsan Vasudevan Coupling 1D 3D Simulations 5 Dec 2016 1 / 29


Outline

1 Background

2 Water Hammer

3 3D CFD

4 Domain

5 Preparations

6 New Boundary Conditions

7 Testing

8 Coupled Simulations



Coupling 1D and 3D Simulations

Why Coupled Simulations?

1D Simulations 3D Simulations

+ Computationally efficient+ Model complex systems

+ Resolve complex flow structuresin space and time

This Study: 1D Simulink + 3D OpenFOAM



Water Hammer Effect

The differential pressure induced in a fluid due to sudden change inmomentum

Joukowsky equation

dp

dt= ρa

dv

dt[a =

√K

ρ; K = ρ

dp

dρ

]a - Speed of sound in fluiddρdp - Compressibility of the fluid



sonicLiquidFoam

1 Begin computation for a time step

2 Solve for the continuity equation

3 Begin PIMPLE loop

4 Solve for the momentum equation

5 Begin pressure corrector loop

6 Perform pressure correction until ’nCorrectors’

7 Repeat steps 4 - 6 until ’nOuterCorrectrs’ or until conditions specifiedin residualControl; which ever is earlier.

8 Linearize the variation in density according to :

ρ = ρ0 + ψ(p− p0) ; ψ =∂ρ

∂p

9 Proceed to next time step



Computational Domain

Mesh : Hexaheadral 200 x 10 x 10

Inlet : Reservoir (Constant Pressure)

Outlet : Valve (Varying Velocity)

Walls : Symmetry (No friction)



Boundary Conditions

Boundary Pressure VelocityInlet fixedValue zeroGradient

Outlet zeroGradient uniformFixedValue

Walls symmetryPlane symmetryPlane

Coupled Simulations [At the outlet]

Velocity : timeVaryingFromMatlab

Pressure : timeVaryingFromMatlabScalar



Preparations

Compatibility Issues..!!The gcc version and Matlab version must be compatible..!!gcc: gcc-4.8.5 ; Matlab : R2015bRefer: se.mathworks.com/support/sysreq/previous_releases.html

ssh -X <CID>@remote12.chalmers.se

#(Enter Password)

echo ". /chalmers/sw/unsup64/OpenFOAM/addToBashrc" >> $HOME/.bashrc

ln -s ~/.bashrc ~/.profile

gnome-terminal & #Open New Terminal

OF4x

mkdir -p $WM_PROJECT_USER_DIR/{run,applications,src}


se.mathworks.com/support/sysreq/previous_releases.html


Preparations

tar xzf SudharsanV.tgz

scp -r ./SudharsanV <cid>@remote12.chalmers.se:/chalmers/users/<cid>

#(Enter Password)

#(Login to Chalmers Account with ssh)

OF4x

cp -r SudharsanV/MatlabBC/externalPipe $WM_PROJECT_USER_DIR/src

cp -r SudharsanV/MatlabBC/timeVaryingFromMatlabScalar $WM_PROJECT_USER_DIR/src

cp -r SudharsanV/mySonicLiquidFoam $WM_PROJECT_USER_DIR/applications

cp -r SudharsanV/Cases/1_OF_SimulinkBC $FOAM_RUN



The OpenFOAM Matlab Link

cd $WM_PROJECT_USER_DIR/src/externalPipe

Class : myFirstMatlabPipeMember Function : matlabCallScript1()

double myFirstMatlabPipe::matlabCallScript1

(const char* matlabFilename,double inputArg1) const

{}

Multiple input and output arguments

double* myFirstMatlabPipe::matlabCallScript1

(const char* matlabFilename,double inputArg1,

double inputArg2, double inputArg3) const

{}

Compile

wmake libso



How do the New BC’s work?

Velocity BC gets velocity and pressure field at that time step.

Averaged and given as input to Matlab along with current time.

Velocity and Pressure are obtained from Matlab

Velocity BC sets velocity field at patch

The pressure BC obtains pressure from the velocity BC and sets thepressure field at the patch.



Velocity BC : timeVaryingFromMatlabCreating a vector field BC

cd $WM_PROJECT_USER_DIR/src

foamNewBC -f -v timeVaryingFromMatlab

cd timeVaryingFromMatlab

File Name: timeVaryingFromMatlabFvPatchVectorField.HRemove the mapping Functions

#include "myFirstMatlabPipe.H"

.

string matlabFile_;

myFirstMatlabPipe mlObj;

vector vel_;

label curTimeIndex_;

scalar t() const;

scalar prs_;

.

vector& vel()

{

return vel_;

}

scalar prs() const

{

return prs_;

}



timeVaryingFromMatlab continued..

File Name: timeVaryingFromMatlabFvPatchVectorField.CConstructor 1

fixedValueFvPatchVectorField(p, iF),

matlabFile_("MyScript;"),

vel_(0,0,0),

curTimeIndex_(-1),

prs_(0.0)

Constructor 2

fixedValueFvPatchVectorField(p, iF),

matlabFile_("MyScript;"),//matlabFile_(dict.lookup("matlabFile")),

vel_(0,0,0),

curTimeIndex_(-1),

prs_(0.0)



timeVaryingFromMatlab continued..Constructor 3

fixedValueFvPatchVectorField(ptf, p, iF, mapper),

vel_(ptf.vel_),

curTimeIndex_(-1),

prs_(ptf.prs_)

Constructor 4

fixedValueFvPatchVectorField(ptf),

vel_(ptf.vel_),

curTimeIndex_(-1),

prs_(ptf.prs_)

Constructor 5

fixedValueFvPatchVectorField(ptf, iF),

vel_(ptf.vel_),

curTimeIndex_(-1),

prs_(ptf.prs_)




Remove the Mapping Functions.Replace the function definition of updateCoeffs() with the following

if (updated())

{

return;

}

if (curTimeIndex_ != this->db().time().timeIndex())

{

if (t()>0.0)

{

..//}

//}




File Name: timeVaryingFromMatlabFvPatchVectorField.CMember Function: updateCoeffs()

const fvPatchField<vector>& UPatch1 =

patch().lookupPatchField<volVectorField, vector>("U");

scalar meanVelocity=gSum(UPatch1.patchInternalField()*

mag(patch().Sf())).y() / gSum(mag(patch().Sf()));

double UPatch = meanVelocity;

Info<<"U_out to Matlab:"<<UPatch<<endl;

const fvPatchField<scalar>& pPatch2 =

patch().lookupPatchField<volScalarField, scalar>("p");

scalar pPatchInternalAverage = gAverage(pPatch2.patchInternalField());

double pPatch=pPatchInternalAverage;

Info<<"P_out to Matlab:"<<pPatch<<endl;





//{..

const char *script=matlabFile_.c_str();

double* output = mlObj.matlabCallScript1(script,t(),UPatch,pPatch);

vel_.y()=output[0];

Info<<"U_in from Matlab"<<output[0]<<endl;

prs_=output[1];

Info<<"P_in from Matlab"<<output[1]<<endl;

fixedValueFvPatchField::operator==(vel_);

}





//{..

else

{

const char *script=matlabFile_.c_str();

double* output = mlObj.matlabCallScript1(script,t(),0,0);

vel_.y()=output[0];

prs_=output[1];

fixedValueFvPatchField::operator==(vel_);

}

curTimeIndex_ = this->db().time().timeIndex();

}

fixedValueFvPatchField::updateCoeffs();



timeVaryingFromMatlab continued..Member Function : write()Change the definition of the write() function to:

fvPatchVectorField::write(os);

os.writeKeyword("Velocity") << vel_ << token::END_STATEMENT << nl;

writeEntry("value", os);

File Name: Make/options

EXE_INC = \

-I$(LIB_SRC)/finiteVolume/lnInclude \

-I$(LIB_SRC)/meshTools/lnInclude \

-Wl,-rpath,/chalmers/sw/sup64/matlab-2015b/bin/glnxa64 \

-I/chalmers/sw/sup64/matlab-2015b/extern/include \

-I$(WM_PROJECT_USER_DIR)/src/externalPipe/myFirstMatlabPipe

LIB_LIBS = \

-lfiniteVolume \

-lmeshTools \

-L/chalmers/sw/unsup64/OpenFOAM/ThirdParty-4.x/platforms/linux64/gcc-4.8.5/lib64 \

-lstdc++ \

-L/chalmers/sw/sup64/matlab-2015b/bin/glnxa64 \

-leng \

-lmx \

-L$(FOAM_USER_LIBBIN) \

-lexternalMatlabPipes

Complile the BC

wmake libso



Pressure BC : timeVaryingFromMatlabScalar

Creating a scalar field BC

cd $WM_PROJECT_USER_DIR/src

foamNewBC -f -s timeVaryingFromMatlabScalar

cd $WM_PROJECT_USER_DIR/src/timeVaryingFromMatlabScalar

File Name: timeVaryingFromMatlabScalarFvPatchScalarField.H

.

//pressure

scalar pr_;

//current time index

label curTimeIndex_;

.



timeVaryingFromMatlabScalar continued..

File Name: timeVaryingFromMatlabScalarFvPatchScalarField.CMember Function: updateCoeffs()

//Obtaining Pressure from velocity BC**

const fvPatchField<vector>& UPatch1 =

this->patch().template lookupPatchField<volVectorField, vector>("U");

const timeVaryingFromMatlabFvPatchVectorField& UPatch2 =

refCast<const timeVaryingFromMatlabFvPatchVectorField>(UPatch1);

scalar pr;

pr = UPatch2.prs();

pr_=pr;

//Set Pressure field at outlet**

fixedValueFvPatchField::operator==(pr_);

curTimeIndex_ = this->db().time().timeIndex();

Compiling the BC

wmake libso



mySonicLiquidFoam

Swap the order in initialization of Velocity and Pressure field increateFields.H

cd $WM_PROJECT_USER_DIR/applications/mySonicLiquidFoam

wmake



Test Case

cd $FOAM_RUN/1_OF_SimulinkBC

0/U

outlet

{

type timeVaryingFromMatlab;

}

0/p

outlet

{

type timeVaryingFromMatlabScalar;

}

system/controlDict

libs ("libtimeVaryingFromMatlab.so");

libs ("libtimeVaryingFromMatlabScalar.so");



Testing continued..

Run the case

blockMesh

checkMesh

mySonicLiquidFoam >& log&

To Visualize in paraFoam

paraFoam -builtin



Results



Coupling 1D and 3D Simulations

Valve Signal

Length : 25 m

Diameter : 0.03m

Time : 3s



Continued ...

3D Simulation 1D Simulationρ0 = 1000 kg/m3

p0 = 101325 Paψ = 1e-6 s2/m2

a = 1000 m/sµ = 0.001 kg/m.s

ρ=1000 kg/m3

K =1e9 Paν =1e-6 m2/sa = 1000m/s

No Friction(symmetric BC at walls)

No Friction(Pipe settings)

Length : 10 m Length : 15 m



Continued ...

Results(Time History of Pressure)

Sources of errors:

1 The effect of time interval andloss of data

2 No. of pipe segments andprobing

3 Block parameters initialization



Questions?Thank You


coupling 3d simulations with 1d simulations (the water hammer …hani/kurser/os_cfd_2016/... ·...

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