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Windkessel boundary implementation

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Old   November 7, 2024, 12:04
Default Windkessel boundary implementation
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Filippo
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Hi foamers

I simulated the flow through a thoracic aorta with a modify pimple, in particular pimpleWKFoam:
Openfoam solver for Windkessel boundary conditions


Now i want to simulate fluid-structure interaction with solids4Foam, so i want to implement a three-element Windkessel boundary condition that is more simple to use for this scope.
In my.C file, I have to utilize 'phi' to compute the flux and estimate the new pressure value from the equation:(1+\frac{Z}{R})*Q+C*Z*\frac{dQ}{dt}=\frac{P}{R}+C*\frac{dP}{dt}
where 'P' is the pressure, 'Q' the flow rate, Z, R and C is the equivalent of impedance, resistance and capacity.


Following this brief introduction, the question is whether it is possible to calculate 'phi' from the previous time-step directly from the boundary using this code?:
Code:
       

const fvsPatchField<scalar>& phi_old =
        db().lookupObject<surfaceScalarField>
        (
            phiName_
        ).oldTime().boundaryField()[patch().index()];
I could not find any existing boundary codition that calculates the ‘phi’ of the previous time step.


If I check the flux out of my boundary with some 'Info' and compare it to the output of pimpleFoam (adjusted with certain information), I get this for the first time-step:
Time = 1e-06

PIMPLE: iteration 1
smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 4.456366458e-05, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 1, Final residual = 4.481724285e-05, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 1, Final residual = 4.495236994e-05, No Iterations 1
Boundary patch: inlet - Phi = -2.788e-05
Boundary patch: inlet - Phi_old = -2.788e-05
Boundary patch: outlet - Phi = 0
Boundary patch: outlet - Phi_old = 0
Boundary patch: outlet_LSA - Phi = 0
Boundary patch: outlet_LSA - Phi_old = 0
Boundary patch: outlet_LCCA - Phi = 0
Boundary patch: outlet_LCCA - Phi_old = 0
Boundary patch: outlet_RCCA - Phi = 0
Boundary patch: outlet_RCCA - Phi_old = 0
Boundary patch: outlet_RSA - Phi = 0
Boundary patch: outlet_RSA - Phi_old = 0
Boundary patch: walls - Phi = 0
Boundary patch: walls - Phi_old = 0
outlet n. =0 pressureNew = 0 pressure_tm1 = 0
impedence Z =91300000resistence R 30300000compliance C 1.74e-08
volFlowRate =0 volFlowRate_tm1 = 0
outlet n. =2 pressureNew = 0 pressure_tm1 = 0
impedence Z =524000000resistence R 174000000compliance C 3.04e-09
volFlowRate =0 volFlowRate_tm1 = 0
outlet n. =1 pressureNew = 0 pressure_tm1 = 0
impedence Z =658000000resistence R 218000000compliance C 2.42e-09
volFlowRate =0 volFlowRate_tm1 = 0
outlet n. =3 pressureNew = 0 pressure_tm1 = 0
impedence Z =514000000resistence R 171000000compliance C 3.09e-09
volFlowRate =0 volFlowRate_tm1 = 0
outlet n. =4 pressureNew = 0 pressure_tm1 = 0
impedence Z =398000000resistence R 132000000compliance C 4e-09
volFlowRate =0 volFlowRate_tm1 = 0
GAMG: Solving for p, Initial residual = 1, Final residual = 4.664607714e-07, No Iterations 48
outlet n. =0 pressureNew = 0 pressure_tm1 = 0
impedence Z =91300000resistence R 30300000compliance C 1.74e-08
volFlowRate =0 volFlowRate_tm1 = 0
outlet n. =2 pressureNew = 0 pressure_tm1 = 0
impedence Z =524000000resistence R 174000000compliance C 3.04e-09
volFlowRate =0 volFlowRate_tm1 = 0
outlet n. =1 pressureNew = 0 pressure_tm1 = 0
impedence Z =658000000resistence R 218000000compliance C 2.42e-09
volFlowRate =0 volFlowRate_tm1 = 0
outlet n. =3 pressureNew = 0 pressure_tm1 = 0
impedence Z =514000000resistence R 171000000compliance C 3.09e-09
volFlowRate =0 volFlowRate_tm1 = 0
outlet n. =4 pressureNew = 0 pressure_tm1 = 0
impedence Z =398000000resistence R 132000000compliance C 4e-09
volFlowRate =0 volFlowRate_tm1 = 0
time step continuity errors : sum local = 9.572685965e-14, global = -8.626285041e-15, cumulative = -8.626285041e-15
PIMPLE: iteration 2
smoothSolver: Solving for Ux, Initial residual = 4.955976818e-05, Final residual = 9.553384395e-09, No Iterations 1
smoothSolver: Solving for Uy, Initial residual = 4.613423638e-05, Final residual = 6.685566471e-09, No Iterations 1
smoothSolver: Solving for Uz, Initial residual = 4.299007742e-05, Final residual = 6.516350192e-09, No Iterations 1
Boundary patch: inlet - Phi = -2.788074286e-05
Boundary patch: inlet - Phi_old = -2.788e-05
Boundary patch: outlet - Phi = 8.783959471e-06
Boundary patch: outlet - Phi_old = 0
Boundary patch: outlet_LSA - Phi = 5.742673988e-06
Boundary patch: outlet_LSA - Phi_old = 0
Boundary patch: outlet_LCCA - Phi = 3.60309519e-06
Boundary patch: outlet_LCCA - Phi_old = 0
Boundary patch: outlet_RCCA - Phi = 3.535694883e-06
Boundary patch: outlet_RCCA - Phi_old = 0
Boundary patch: outlet_RSA - Phi = 6.215318152e-06
Boundary patch: outlet_RSA - Phi_old = 0
Boundary patch: walls - Phi = 0
Boundary patch: walls - Phi_old = 0
outlet n. =0 pressureNew = 801.9760046 pressure_tm1 = 0
impedence Z =91300000resistence R 30300000compliance C 1.74e-08
volFlowRate =8.783959471e-06 volFlowRate_tm1 = 0
outlet n. =2 pressureNew = 3009.163059 pressure_tm1 = 0
impedence Z =524000000resistence R 174000000compliance C 3.04e-09
volFlowRate =5.742673988e-06 volFlowRate_tm1 = 0
outlet n. =1 pressureNew = 2370.838124 pressure_tm1 = 0
impedence Z =658000000resistence R 218000000compliance C 2.42e-09
volFlowRate =3.60309519e-06 volFlowRate_tm1 = 0
outlet n. =3 pressureNew = 1817.348314 pressure_tm1 = 0
impedence Z =514000000resistence R 171000000compliance C 3.09e-09
volFlowRate =3.535694883e-06 volFlowRate_tm1 = 0
outlet n. =4 pressureNew = 2473.698179 pressure_tm1 = 0
impedence Z =398000000resistence R 132000000compliance C 4e-09
volFlowRate =6.215318152e-06 volFlowRate_tm1 = 0
GAMG: Solving for p, Initial residual = 0.1266545562, Final residual = 6.283600403e-07, No Iterations 21
outlet n. =0 pressureNew = 801.9760046 pressure_tm1 = 0
impedence Z =91300000resistence R 30300000compliance C 1.74e-08
volFlowRate =8.783959471e-06 volFlowRate_tm1 = 0
outlet n. =2 pressureNew = 3009.163059 pressure_tm1 = 0
impedence Z =524000000resistence R 174000000compliance C 3.04e-09
volFlowRate =5.742673988e-06 volFlowRate_tm1 = 0
outlet n. =1 pressureNew = 2370.838124 pressure_tm1 = 0
impedence Z =658000000resistence R 218000000compliance C 2.42e-09
volFlowRate =3.60309519e-06 volFlowRate_tm1 = 0
outlet n. =3 pressureNew = 1817.348314 pressure_tm1 = 0
impedence Z =514000000resistence R 171000000compliance C 3.09e-09
volFlowRate =3.535694883e-06 volFlowRate_tm1 = 0
outlet n. =4 pressureNew = 2473.698179 pressure_tm1 = 0
impedence Z =398000000resistence R 132000000compliance C 4e-09
volFlowRate =6.215318152e-06 volFlowRate_tm1 = 0
time step continuity errors : sum local = 1.04852787e-10, global = 1.125593907e-11, cumulative = 1.124731279e-11
smoothSolver: Solving for nuTilda, Initial residual = 0, Final residual = 0, No Iterations 0
Boundary patch: inlet - Phi = -2.788074286e-05
Boundary patch: inlet - Phi_old = -2.788e-05
Boundary patch: outlet - Phi = 9.900847563e-06
Boundary patch: outlet - Phi_old = 0
Boundary patch: outlet_LSA - Phi = 5.02871383e-06
Boundary patch: outlet_LSA - Phi_old = 0
Boundary patch: outlet_LCCA - Phi = 3.426890827e-06
Boundary patch: outlet_LCCA - Phi_old = 0
Boundary patch: outlet_RCCA - Phi = 3.787690118e-06
Boundary patch: outlet_RCCA - Phi_old = 0
Boundary patch: outlet_RSA - Phi = 5.73812973e-06
Boundary patch: outlet_RSA - Phi_old = 0
Boundary patch: walls - Phi = 0
Boundary patch: walls - Phi_old = 0
ExecutionTime = 15.11 s ClockTime = 15 s



I have 8.78e-06 [m^3/s] for outlet 0 for the second pimple iteration, which is equivalent to Boundary patch: outlet - Phi = 8.78e-06 [m^3/s](outlet 0 is equivalent to boundary patch: outlet). This value changes to Boundary patch: outlet - Phi = 9.90e-06 [m^3/s] at the end of the pimple cycle. Why did I get this? Before and after the pressure equation, I placed the 'Info' to see if the values were the same. No lines of code need to run after the second 'Info' in my pimpleFoamInfo.


These are my .C boundary code(WK1FvPatchScalarField.C) and my pimpleFoamInfo:
-WK1FvPatchScalarField.C
-pimpleFoamInfo.C

I use openfoam2012.

Apologies for the length of the message, this is my first time posting in the forum, unfortunately I initially made a mistake in posting the Thread and therefore had to do a quick repost. I also apologise in advance for any misunderstandings in the code, this is the first experience as programming in openfoam.
Thanks in advance to anyone who replies.
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