BFC for Dam break problem

Mehdi BEN ELHADJ

Consider a horizontal and frictionless channel, which is 1000 m in lenght. A dam site is located at 500 m. The initial upstream-water depth is 10 m, and the vertical dimension of gaz layer is 3m. At time t=0, the dam is broken instantaneously.

I use a space steps of 5 m (200 cells ) in horizontal direction ; 0,5 m (20 cells in upstream-water) in vertical direction and 3 cells in gaz layer in vertical direction. A time step is (20/100) s.

I work with a (2-D) model and using implicit scheme for time and hybrid scheme for convection terms. I use SEM method (Scalar Equation Method) in PHOENICS code.

So, If I simulate this case with a fixe cartesian mesh in BFC and with in BFC, I don't find the same results.

**With BFC**

TALK=T;RUN( 1, 1);VDU=x11-term

GROUP 1. Run title and other preliminaries

TEXT(Dam break : SEM)

INTEGER(NY1,NY2,NZ1,NZ2)

NX=1;NY1=100;NY2=100;NZ1=20;NZ2=3

NY=NY1+NY2

NZ=NZ1+NZ2

REAL(L1,L2,L3)

L1=500.0

L2=500.0

L3=L2+L1

GROUP 2. Transience; time-step specification

STEADY=F;

LSTEP=100 ;TLAST=20

GRDPWR(T,LSTEP,TLAST,1.0)

GROUP 3. X-direction grid specification

NREGX=1

IREGX=1;GRDPWR(X,NX,1,1.0);

GROUP 4. Y-direction grid specification

NREGY=2

IREGY=1;GRDPWR(Y,NY1,L1,1.0);

IREGY=2;GRDPWR(Y,NY2,L2,1.0);

GROUP 5. Z-direction grid specification

NREGZ=2;

IREGZ=1;GRDPWR(Z,NZ1,10,1.0);

IREGZ=2;GRDPWR(Z,NZ2,3,1.0);

GROUP 6. Body-fitted coordinates or grid distortion

BFC=T;SETBFC=T;MOVBFC=T

GROUP 7. Variables stored, solved & named

STORE(VOLU,CONI,CONJ,CONK)

STORE(DEN1,PRPS);

SOLVE(VFOL,SURN)

SOLUTN(P1,Y,Y,Y,N,N,N)

SOLUTN(V1,Y,Y,N,N,N,N)

SOLUTN(W1,Y,Y,N,N,N,N)

GROUP 8. Terms (in differential equations) & devices

** activate the "gas-and-liquid algorithm", ie volumetric

continuity equation, and allow convection fluxes to be

modified in GROUND

GALA=T;

TERMS(VFOL,N,N,N,N,P,P)

TERMS(SURN,N,N,N,N,P,P)

DIFCUT=0.0

UCONV=T

GROUP 9. Properties of the medium (or media)

** signal that density is to be computed by the HOL method

and set the densities of the liquid and gas respectively

RHO1=GRND10

ENUL=GRND10

GROUP 11. Initialization of variable or porosity fields

FIINIT(CONI)=0.0;FIINIT(CONJ)=0.0;FIINIT(CONK)=0.0

FIINIT(P1)=0.0;FIINIT(V1)=0.0;FIINIT(W1)=0.0;

FIINIT(SURN)=0.0; FIINIT(PRPS)=0.

FIINIT(DEN1)=1.189;

INIADD=F

PATCH(LIQUID,INIVAL,1,NX,1,NY1,1,NZ1,1,1)

init(LIQUID,SURN,ZERO,1)

init(LIQUID,VFOL,ZERO,1)

init(LIQUID,PRPS,ZERO,67)

init(LIQUID,DEN1,ZERO,1000.5)

GROUP 13. Boundary conditions and special sources ** the pressure is held to zero along the open top boundary

PATCH(REFP,CELL,1,NX,1,NY,NZ,NZ,1,LSTEP)

COVAL(REFP,P1,FIXVAL,ZERO)

** provide for the gravity-force source of w1

PATCH(GRAV,PHASEM,1,NX,1,NY,1,NZ,1,LSTEP)

COVAL(GRAV,W1,FIXFLU,-9.81)

GROUP 15. Termination of sweeps

LSWEEP=50;

LITER(SURN)=1

GROUP 16. Termination of iterations

SELREF=T;RESFAC=0.01

GROUP 17. Under-relaxation devices

RELAX(P1,LINRLX,0.7)

RELAX(V1,FALSDT,0.1)

RELAX(W1,FALSDT,0.1)

GROUP 19. Data communicated by satellite to GROUND ** provide for the dumping of field data at each time

step, for us by PHOTON

USEGRX=T;USEGRD=F;LSG60=T

IDISPA=1;IDISPB=1;IDISPC=LSTEP;CSG1=W

CSG2=XYZ

IPRPSA=67;IPRPSB=0;

SURF=T;

RLOLIM=0.4;RUPLIM=0.6

VARMIN(SURN)=0.0; VARMAX(SURN)=1.0

ISG1=1

RSG1=0.0;RSG2=1.0

RSG3=0.0;RSG4=L3

RSG5=0.0;RSG6=13

RSG7=1.0;RSG8=1.0;

RSG9=1.0;RSG10=1.0;

RSG11=1.0;RSG12=1.0

RSG13=0.0;RSG14=0.0;RSG15=0.0

GROUP 22. Spot-value print-out

TSTSWP=-1

ECHO=T

IYMON=2*NY/3;IZMON=NZ/2

GROUP 23. Field print-out and plot control

OUTPUT(P1,N,N,N,N,Y,Y);OUTPUT(V1,N,Y,N,Y,Y,Y)

OUTPUT(W1,N,N,N,N,Y,Y);OUTPUT(SURN,N,N,N,N,N,N)

OUTPUT(DEN1,N,N,N,N,N,N) OUTPUT(VFOL,Y,N,N,N,Y,Y);

OUTPUT(IMB1,N,Y,N,Y,Y,Y); OUTPUT(ENUL,N,N,N,N,Y,Y);OUTPUT(RHO1,N,N,N,N,N,N)

OUTPUT(PRPS,N,N,N,N,N,N)

NTPRIN=100

NYPRIN=1

NZPRIN=1

IPROF=2

XZPR=T

STOP

**With out BFC**

TALK=T;RUN( 1, 1);VDU=X11-TERM

GROUP 1. Run title and other preliminaries

TEXT(Dam break: SEM)

INTEGER(NY1,NY2,NZ1,NZ2)

NY1=100;NY2=100;NZ1=20;NZ2=3

NY=NY1+NY2

NZ=NZ1+NZ2

GROUP 2. Transience; time-step specification

STEADY=F;

LSTEP=100 ;TLAST=20

GRDPWR(T,LSTEP,TLAST,1.0)

GROUP 4. Y-direction grid specification

NREGY=2

IREGY=1;GRDPWR(Y,NY1,500,1.0);

IREGY=2;GRDPWR(Y,NY2,500,1.0);

GROUP 5. Z-direction grid specification

NREGZ=2;

IREGZ=1;GRDPWR(Z,NZ1,10,1.0);

IREGZ=2;GRDPWR(Z,NZ2,3,1.0);

GROUP 7. Variables stored, solved & named

STORE(DEN1,PRPS);

SOLVE(VFOL,SURN)

SOLUTN(P1,Y,Y,Y,N,N,N)

SOLUTN(V1,Y,Y,N,N,N,N)

SOLUTN(W1,Y,Y,N,N,N,N)

GROUP 8. Terms (in differential equations) & devices ** activate the "gas-and-liquid algorithm", ie volumetric

continuity equation, and allow convection fluxes to be

modified in GROUND

GALA=T;

TERMS(VFOL,N,N,N,N,P,P)

TERMS(SURN,N,N,N,N,P,P)

GROUP 9. Properties of the medium (or media) ** signal that density is to be computed by the HOL method

and set the densities of the liquid and gas respectively

RHO1=GRND10

ENUL=GRND10

GROUP 11. Initialization of variable or porosity fields

FIINIT(P1)=0.0;FIINIT(V1)=0.0;FIINIT(W1)=0.0;

FIINIT(SURN)=0.0; FIINIT(PRPS)=0.

FIINIT(DEN1)=1.189;

INIADD=F

PATCH(LIQUID,INIVAL,1,NX,1,NY1,1,NZ1,1,1)

init(LIQUID,SURN,ZERO,1)

init(LIQUID,VFOL,ZERO,1)

init(LIQUID,PRPS,ZERO,67)

init(LIQUID,DEN1,ZERO,1000.5)

GROUP 13. Boundary conditions and special sources ** the pressure is held to zero along the open top boundary

PATCH(REFP,CELL,1,NX,1,NY,NZ,NZ,1,LSTEP)

COVAL(REFP,P1,FIXVAL,ZERO)

** provide for the gravity-force source of w1

PATCH(GRAV,PHASEM,1,NX,1,NY,1,NZ,1,LSTEP)

COVAL(GRAV,W1,FIXFLU,-9.81)

GROUP 15. Termination of sweeps

LSWEEP=50;

LITER(SURN)=1

GROUP 16. Termination of iterations

SELREF=T;RESFAC=0.01

GROUP 17. Under-relaxation devices

RELAX(P1 ,LINRLX,0.7)

RELAX(V1,FALSDT,1)

RELAX(W1,FALSDT,1)

GROUP 19. Data communicated by satellite to GROUND ** provide for the dumping of field data at each time

step, for us by PHOTON

IDISPA=LSTEP;IDISPB=1;IDISPC=LSTEP;CSG1=W

IPRPSA=67;IPRPSB=0;

SURF=T;

RLOLIM=0.4;RUPLIM=0.6

VARMIN(SURN)=0.0; VARMAX(SURN)=1.0

GROUP 22. Spot-value print-out

TSTSWP=-1

ECHO=T

IYMON=2*NY/3;IZMON=NZ/2

GROUP 23. Field print-out and plot control

OUTPUT(P1,N,N,N,N,Y,Y);OUTPUT(V1,N,Y,N,Y,Y,Y)

OUTPUT(W1,N,N,N,N,Y,Y);OUTPUT(SURN,N,N,N,N,N,N)

OUTPUT(DEN1,N,N,N,N,N,N)

OUTPUT(VFOL,Y,N,N,N,Y,Y);

OUTPUT(IMB1,N,Y,N,Y,Y,Y)

OUTPUT(ENUL,N,N,N,N,Y,Y);OUTPUT(RHO1,N,N,N,N,N,N)

OUTPUT(PRPS,N,N,N,N,N,N)

NTPRIN=100

NYPRIN=1

NZPRIN=1

IPROF=2

XZPR=T

STOP