TEXT(2S K-E MODEL_BKWRD FACING STEP Y-X :T405 TITLE DISPLAY This simulation concerns incompressible, turbulent flow over a backward-facing step in a two-dimensional closed channel, as described fully in library case T103. For this case, the standard form of the k-e turbulence model is known to underpredict the reattachment length XR by about 14%. Calculations may be made with the high-Re form of the standard k-e model or the 2-scale k-e model, which is selected by putting TSKE=T. ENDDIS The fine-grid calculation employs a non-uniform mesh of NY=50 by NX=60 for which the standard k-e model predicts XR/H=5.8 and the 2-scale k-e model predicts XR/H=7.6. For a grid-independent solution these models should produce XR/H=6.1 and 7.4 respectively. The measurements indicate that XR/H=7.1. This mesh, which requires 1200 sweeps for a converged solution, is not fine enough around the vicinity of the step to resolve the experimentally-observed secondary-separation region in the corner just downstream of the step. For speed of computation, the calculation is set up to run for 20 sweeps on a coarse mesh of NY=20 by NX=25. About 400 sweeps are required for complete convergence. photon use p msg longitudinal velocity profiles and vectors con u1 z 1 fi;0.001 vec z 1 msg msg Press e to END enduse INTEGER(NYS,NXS);BOOLEAN(TSKE,FINEG);TSKE=T;FINEG=F REAL(HEIGHT,WIDTH,CLEN,SLEN,REYNO,UIN,TKEIN,EPSIN,GENUT) REAL(FRIC,MIXL);FRIC=0.018 ** Calculation of domain specifications HEIGHT=0.0381;WIDTH=3.*HEIGHT SLEN=4.*HEIGHT;CLEN=20.*HEIGHT; REYNO=4.5E4;UIN=13. GROUP 3. X-direction grid specification GROUP 4. Y-direction grid specification ** channel length = 0.762 & channel width = 0.1143 IF(FINEG) THEN + NXS=10;NYS=20;NREGX=2 + IREGX=1;GRDPWR(X,NXS,SLEN,1.0) + IREGX=2;GRDPWR(X,50,CLEN-SLEN,1.1) + NREGY=2 + IREGY=1;GRDPWR(Y,-NYS,HEIGHT,1.3) + IREGY=2;GRDPWR(Y,-30,WIDTH-HEIGHT,1.4) ELSE + NXS=5;NYS=10;NREGX=2 + IREGX=1;GRDPWR(X,NXS,SLEN,1.0) + IREGX=2;GRDPWR(X,20,CLEN-SLEN,1.1) + NREGY=2 + IREGY=1;GRDPWR(Y,-NYS,HEIGHT,1.3) + IREGY=2;GRDPWR(Y,-10,WIDTH-HEIGHT,1.4) ENDIF GROUP 7. Variables stored, solved & named SOLVE(P1,U1,V1);SOLUTN(P1,Y,Y,Y,N,N,N);STORE(ENUT) IF(TSKE) THEN + TURMOD(TSKEMO) ELSE + TURMOD(KEMODL) ENDIF GROUP 8. Terms (in differential equations) & devices GROUP 9. Properties of the medium (or media) RHO1=1.0;ENUL=UIN*HEIGHT/REYNO GROUP 11. Initialization of variable or porosity fields ** Calculation of KE (where fric=0.018)... TKEIN=0.25*UIN*UIN*FRIC;MIXL=0.09*HEIGHT EPSIN=0.1643*TKEIN**1.5/MIXL FIINIT(U1)=UIN;FIINIT(P1)=1.3E-4;FIINIT(U1)=0.001*UIN FIINIT(KE)=TKEIN;FIINIT(EP)=EPSIN;FIINIT(V1)=0.001*UIN FIINIT(ENUT)=TKEIN**2/EPSIN IF(TSKE) THEN + REAL(KTDKP);KTDKP=0.25 + FIINIT(ET)=EPSIN;FIINIT(KP)=TKEIN/(1.+KTDKP) + FIINIT(KT)=KTDKP*FIINIT(KP) ENDIF ** Initialization of variables in blocked region ** do not trigger CONPOR to set wall patches as harmonic-avereging will be hard-wired for all variables and convergence deteriorates plus profiles become non smooth CONPOR(STEP,0.0,CELL,#1,#1,#1,#1,#1,#1) GROUP 13. Boundary conditions and special sources INLET(INLET,WEST,#1,#1,#2,#NREGY,#1,#1,1,1) VALUE(INLET,P1,UIN);VALUE(INLET,U1,UIN) VALUE(INLET,EP,EPSIN) IF(TSKE) THEN + VALUE(INLET,KP,FIINIT(KP));VALUE(INLET,KT,FIINIT(KT)) + VALUE(INLET,ET,EPSIN) ELSE + VALUE(INLET,KE,TKEIN) ENDIF PATCH(OUTLET,EAST,#NREGX,#NREGX,#1,#NREGY,#1,#1,1,1) COVAL(OUTLET,P1,1.0E5,0.0) COVAL(OUTLET,U1,ONLYMS,0.0);COVAL(OUTLET,V1,ONLYMS,0.0) COVAL(OUTLET,EP,ONLYMS,0.0) ** N-wall WALL(WFNN,NORTH,1,NX,NY,NY,1,1,1,1) ** S2-wall WALL(WFNS,SOUTH,NXS+1,NX,1,1,1,1,1,1) PATCH(STEP-WW,WWALL,NXS+1,NXS+1,1,NYS,1,1,1,1) COVAL(STEP-WW,V1,LOGLAW,0.0);COVAL(STEP-WW,EP,LOGLAW,LOGLAW) PATCH(STEP-SW,SWALL,1,NXS,NYS+1,NYS+1,1,1,1,1) COVAL(STEP-SW,U1,LOGLAW,0.0);COVAL(STEP-SW,EP,LOGLAW,LOGLAW) IF(TSKE) THEN + COVAL(STEP-WW,KP,LOGLAW,LOGLAW);COVAL(STEP-WW,KT,LOGLAW,LOGLAW) + COVAL(STEP-WW,ET,LOGLAW,LOGLAW) + COVAL(STEP-SW,KP,LOGLAW,LOGLAW);COVAL(STEP-SW,KT,LOGLAW,LOGLAW) + COVAL(STEP-SW,ET,LOGLAW,LOGLAW) + COVAL(OUTLET,KP,ONLYMS,0.0);COVAL(OUTLET,KT,ONLYMS,0.0) + COVAL(OUTLET,ET,ONLYMS,0.0) ELSE + COVAL(STEP-WW,KE,LOGLAW,LOGLAW);COVAL(STEP-SW,KE,LOGLAW,LOGLAW) + COVAL(OUTLET,KE,ONLYMS,0.0) ENDIF GROUP 15. Termination of sweeps LSWEEP=100 GROUP 16. Termination of iterations SELREF=T; RESFAC=0.1 GROUP 17. Under-relaxation devices REAL(DTF) DTF=XULAST/UIN/NX; RELAX(U1,FALSDT,DTF*NX); RELAX(V1,FALSDT,DTF*NX) RELAX(EP,LINRLX,0.5); RELAX(ENUT,LINRLX,0.5) IF(TSKE) THEN + RELAX(KP,LINRLX,0.5); RELAX(EP,LINRLX,0.5) + RELAX(KT,LINRLX,0.5); RELAX(ET,LINRLX,0.5) ELSE + RELAX(KE,LINRLX,0.5) ENDIF GROUP 22. Monitor print-out IYMON=NYS-2;IXMON=NXS+2;NPRMON=100 GROUP 23. Field print-out and plot control NPLT=10;TSTSWP=-1 YPLS=T;LITER(EP)=5 IF(TSKE) THEN + LITER(KP)=5;LITER(KT)=5;LITER(ET)=5 ELSE + LITER(KE)=5 ENDIF