GROUP 1. Run title and other preliminaries TEXT(REALISABLE KE_3D FLOW PAST A CUBE IN A CHANNEL: T308 TITLE DISPLAY The case considered is 3D, steady, incompressible, turbulent flow past a surface-mounted cube in a channel. The flow separates in front of the cube to form a primary and secondary vortex, and the main vortex wraps as a horse-shoe vortex around the cube into the wake. The flow separates at the front corners of the cube on the roof and the side walls; the reattaches on the side walls but not on the roof. A large separation region develops behind the cube which interacts with the horseshoe vortex. In the experiments vortex shedding as observed from the side walls, and due to momentum exchange with the wake, this will lead to a shorter separation length than is reported here for a steady simulation. The height of the cube is 50% of that of the channel. The flow Reynolds number based on channel bulk velocity and cube height H is 40,000. The inlet plane is located 7H upstream of the cube, and the outlet plane 10H downstream of the cube. Because of symmetry conditions, only half of the width of the flow is calculated. A fixed-pressure boundary condition is applied at the outlet, and uniform flow profiles are specified at the inlet. The case is set up to run any one of 6 variants of the k-e model with scalable wall functions, namely the standard model and the MMK, Kato-Launder, RNG, Chen-Kim and realisable variants. An option is provided to also run the standard k-w model. The case has been studied experimentally by Martinuzzi & Tropea [J.Fluids Engng, 115, p85-92,1993] and numerically by Lakehal & Rodi [J.Wind Eng. Ind.Aerodyn, 67 & 68, p65-78, 1997]. For this case, the main parameters that characterise separation are the frontal stagnation point Ys/H, the primary upstream separation point Zf/H, the roof reattachment point Zr/H and the length of the separation zone behind the cube Zb/H. The experimental and computed results for Zb are given below: K-E KL MMK RKE CHEN RNG KO EXPT Zb/H = 2.08 2.72 2.81 2.46 3.1 2.92 1.70 1.61 These results are not grid independent, and the mesh is not fine enough to resolve the expected separation on the roof nor to capture adequately the upstream and downstream separation regions. For this rather coarse mesh, all the k-e models overpredict Zb, and the standard k-w model gives close agreement with the data. The standard k-e model is known to produce too small a separation on the roof with unrealistic roof reattachment. The modified k-e models produce longer separation regions and no reattachment, which is in agreement with the data. However, the present computations employ insufficient mesh resolution to exemplify these benefits. However, it is likely that more mesh and the inclusion of unsteady effects are required for a much improved prediction of the separation length behind the cube. ENDDIS This AUTOPLOT sequence provides a plot of the axial velocity W1 at the symmetry plane and along the bottom surface of the solution domain versus normalised axial distance X. The axial coordinate 0.0 corresponds to the rear surface of the cube. The reattachment point behind the cube corresponds the axial location where W1 changes from negative to positive. AUTOPLOT USE file phida 3 d 1 w1 y 1 x 1 plot redr shift x -8 1 scale level y 0 scale x 0 5 ENDUSE CHAR(CTURB) REAL(HCUBE,CLUP,CLDOWN,CHIGHT,CWIDTH) REAL(REYNO,UIN,TKEIN,EPSIN,MIXL,FRIC,OMIN) INTEGER(NYC,NZC,NZUP,NZDOWN,NYUP,NXC,NXUP,JKO) JKO=0 ** Calculation of domain specifications HCUBE=1.0;UIN=1.0 CHIGHT=2.*HCUBE;CLUP=7.0*HCUBE;CLDOWN=10.*HCUBE CWIDTH=4.5*HCUBE REYNO=4.E4 FRIC=0.018;TKEIN=0.25*UIN*UIN*FRIC MIXL=0.09*CHIGHT;EPSIN=0.1643*TKEIN**1.5/MIXL NXC=12;NXUP=26 NYC=18;NYUP=18 NZUP=38;NZC=12;NZDOWN=34 GROUP 3. X-direction grid specification NREGX=2 IREGX=1;GRDPWR(X,NXC,0.5*HCUBE,1.0) IREGX=2;GRDPWR(X,NXUP,-(CWIDTH-0.5*HCUBE),1.08) GROUP 4. Y-direction grid specification NREGY=2 IREGY=1;GRDPWR(Y,NYC,-HCUBE,-1.06) IREGY=2;GRDPWR(Y,NYUP,-(CHIGHT-HCUBE),1.06) GROUP 5. Z-direction grid specification NREGZ=3 IREGZ=1;GRDPWR(Z,NZUP,-CLUP,-1.05) IREGZ=2;GRDPWR(Z,NZC,HCUBE,1.0) IREGZ=3;GRDPWR(Z,NZDOWN,-CLDOWN,1.07) GROUP 7. Variables stored, solved & named SOLVE(P1,U1,V1,W1);SOLUTN(P1,Y,Y,Y,N,N,N);STORE(ENUT) SOLUTN(U1,P,P,P,P,P,N);SOLUTN(V1,P,P,P,P,P,N) SOLUTN(W1,P,P,P,P,P,N) MESG( Enter the required turbulence model: MESG( KEM - Standard k-e model MESG( CHEN - Chen-Kim k-e model MESG( RNG - RNG k-e model MESG( MMK - MMK k-e model MESG( KLM - KL k-e model MESG( KO - k-omega model MESG( RKE - Realisable k-e model (default) MESG( READVDU(CTURB,CHAR,RKE) CASE :CTURB: OF WHEN KEM,3 + TEXT(K-E SURFACE-MOUNTED CUBE FLOW :T308 + MESG(Standard k-e model + TURMOD(KEMODL) WHEN CHEN,4 + TEXT(CHEN KE SURFACE-MOUNTED CUBE FLOW :T308 + MESG(Chen k-e model + TURMOD(KECHEN) WHEN RNG,3 + TEXT(RNG KE SURFACE-MOUNTED CUBE FLOW :T308 + MESG(RNG k-e model + TURMOD(KERNG) WHEN MMK,3 + TEXT(MMK K-E SURFACE-MOUNTED CUBE FLOW :T308 + MESG(MMK k-e model + TURMOD(KEMMK) WHEN KLM,3 + TEXT(KL K-E SURFACE-MOUNTED CUBE FLOW :T308 + MESG(KL k-e model + TURMOD(KEKL) WHEN RKE,3 + TEXT(RK K-E SURFACE-MOUNTED CUBE FLOW :T308 + MESG(RK k-e model + TURMOD(KEREAL);STORE(C1E) WHEN KO,2 + TEXT(K-O SURFACE-MOUNTED CUBE FLOW :T308 + MESG(Standard k-w model + TURMOD(KOMODL);STORE(EP) + JKO=1;OMIN=EPSIN/(0.09*TKEIN) ENDCASE STORE(YPLS) SCALWF=T ! Scalable wall functions GROUP 8. Terms (in differential equations) & devices GROUP 9. Properties of the medium (or media) RHO1=1.0;ENUL=UIN*HCUBE/REYNO GROUP 11. Initialization of variable or porosity fields FIINIT(W1)=UIN;FIINIT(P1)=1.3E-4 FIINIT(KE)=TKEIN;FIINIT(EP)=EPSIN;FIINIT(V1)=0.001*UIN IF(JKO.EQ.1) THEN + FIINIT(OMEG)=OMIN ENDIF ** Initialization of variables in blocked region CONPOR(CUBE,0.0,CELL,-#1,-#1,-#1,-#1,-#2,-#2) GROUP 13. Boundary conditions and special sources INLET(INLET,LOW,#1,#NREGX,#1,#NREGY,#1,#1,1,1) VALUE(INLET,P1,UIN);VALUE(INLET,W1,UIN) VALUE(INLET,KE,TKEIN);VALUE(INLET,EP,EPSIN) PATCH(OUTL,HIGH,#1,#NREGX,#1,#NREGY,#NREGZ,#NREGZ,1,1) COVAL(OUTL,P1,1.0E3,0.0) COVAL(OUTL,W1,ONLYMS,0.0);COVAL(OUTL,V1,ONLYMS,0.0) COVAL(OUTL,KE,ONLYMS,0.0);COVAL(OUTL,EP,ONLYMS,0.0) WALL(WALLN,NORTH,#1,#NREGX,#NREGY,#NREGY,#1,#NREGZ,1,1) WALL(WALLS,SOUTH,#1,#NREGX,#1,#1,#1,#NREGZ,1,1) IF(JKO.EQ.1) THEN + VALUE(INLET,OMEG,OMIN) ENDIF GROUP 15. Termination of sweeps LSWEEP=1000 GROUP 16. Termination of iterations SELREF=T LITER(P1)=50;LITER(KE)=5;LITER(EP)=5 GROUP 17. Under-relaxation devices REAL(DTF);DTF=ZWLAST/UIN/NZ/2 RELAX(W1,FALSDT,DTF);RELAX(V1,FALSDT,DTF) RELAX(U1,FALSDT,DTF) RELAX(KE,FALSDT,DTF); RELAX(EP,FALSDT,DTF) IF(JKO.EQ.1) THEN + RELAX(OMEG,FALSDT,DTF) ENDIF IYMON=NY-4;IXMON=1;IZMON=NZ-4;NPRMON=100 GROUP 23. Field print-out and plot control ITABL=3;NPLT=10;IPLTL=LSWEEP;NZPRIN=2;NYPRIN=2 TSTSWP=-1 DISTIL=T STORE(PRPS); EX(PRPS)=9.774E-01; EX(VPOR)=9.774E-01 CASE :CTURB: OF WHEN CHEN,4 + EX(P1 )=6.623E-02;EX(U1 )=3.166E-02 + EX(V1 )=2.526E-02;EX(W1 )=9.512E-01 + EX(KE )=5.345E-03;EX(EP )=1.880E-03 + EX(YPLS)=4.930E+00;EX(ENUT)=4.175E-03 WHEN MMK,3 + EX(P1 )=6.158E-02;EX(U1 )=2.959E-02 + EX(V1 )=2.309E-02;EX(W1 )=9.529E-01 + EX(KE )=5.234E-03;EX(EP )=1.703E-03 + EX(YPLS)=4.916E+00;EX(DWDY)=3.226E-01 + EX(DWDX)=1.439E-01;EX(DVDZ)=3.854E-02 + EX(DVDX)=3.064E-02;EX(DUDZ)=3.872E-02 + EX(DUDY)=3.584E-02;EX(FOMG)=4.360E-01 + EX(ENUT)=1.407E-03 WHEN KLM,3 + EX(P1 )=6.087E-02;EX(U1 )=2.910E-02 + EX(V1 )=2.268E-02;EX(W1 )=9.531E-01 + EX(KE )=5.307E-03;EX(EP )=1.759E-03 + EX(YPLS)=4.917E+00;EX(DWDY)=3.190E-01 + EX(DWDX)=1.432E-01;EX(DVDZ)=3.824E-02 + EX(DVDX)=2.999E-02;EX(DUDZ)=3.867E-02 + EX(DUDY)=3.519E-02;EX(FOMG)=4.458E-01 + EX(ENUT)=4.466E-03 WHEN KEM,3 +EX(P1 )=5.786E-02;EX(U1 )=2.727E-02 +EX(V1 )=2.217E-02;EX(W1 )=9.572E-01 +EX(KE )=8.058E-03;EX(EP )=3.191E-03 +EX(YPLS)=4.973E+00;EX(ENUT)=5.034E-03 WHEN KO,2 +EX(P1 )=5.701E-02;EX(U1 )=2.619E-02 +EX(V1 )=2.080E-02;EX(W1 )=9.569E-01 +EX(KE )=1.372E-02;EX(EP )=4.705E-03 +EX(YPLS)=5.111E+00;EX(OMEG)=1.820E+00 +EX(ENUT)=7.999E-03 WHEN RNG,3 +EX(P1 )=6.545E-02;EX(U1 )=3.136E-02 +EX(V1 )=2.533E-02;EX(W1 )=9.524E-01 +EX(KE )=5.400E-03;EX(EP )=1.857E-03 +EX(YPLS)=4.888E+00;EX(ENUT)=3.650E-03 WHEN RKE,3 +EX(P1 )=6.155E-02;EX(U1 )=2.941E-02 +EX(V1 )=2.435E-02;EX(W1 )=9.567E-01 +EX(KE )=6.595E-03;EX(EP )=2.144E-03 +EX(YPLS)=4.925E+00;EX(C1E )=4.491E-01 +EX(DWDZ)=7.234E-02;EX(DWDY)=3.142E-01 +EX(DWDX)=1.289E-01;EX(DVDZ)=4.032E-02 +EX(DVDY)=5.053E-02;EX(DVDX)=3.186E-02 +EX(DUDZ)=3.929E-02;EX(DUDY)=3.484E-02 +EX(DUDX)=5.655E-02;EX(EPKE)=1.823E-01 +EX(CMU )=1.496E-01;EX(ENUT)=7.406E-03 ENDCASE