TEXT(RNG K-E FLOW IN TURNAROUND DUCT :T106 TITLE DISPLAY This case concerns plane, two-dimensional, incompressible flow through a 180 degree turnaround duct. The flow exhibits large streamline curvature together with flow separation near the bend exit next to the inner surface of the duct. Calculations are made with the high-re k-e model and the high-Re RNG k-e model. The latter is selected by setting RNGM=T in the Q1 file. The fine-mesh calculation employs a non-uniform mesh of NY=25 and NZ=80, for which the solution is not as yet grid independent. However, the results of this calculation demonstrate that the RNG model predicts flow separation whereas the standard k-e model does not. Even calculations with a mesh of NY=40 and NZ=180 indicate that grid independence has not yet been achieved. For speed of computation, this library case has been set up to run for 20 sweeps only on a coarse mesh of NY=20 by NZ=40. About 250 sweeps are required for complete convergence. ENDDIS This AUTOPLOT USE file produces a cross stream plot of the W1 velocity resolute just downstream of the bend exit. The blue line is the RNG solution, which shows backflow near the inner wall, and the red line is the solution obtained with the standard k-e model, which shows no backflow. AUTOPLOT USE file phi 5 xyz da 1 w1 z 51 col3 1 level y 0 msg Velocity (W1) profile msg Press e to END ENDUSE GROUP 1. Run title CHAR(CTURB,TLSC);BOOLEAN(FINEG);FINEG=F REAL(REYNO,WIN,TKEIN,EPSIN,WIDTH,LENGTH,YAXIS) REYNO=1.E5;WIDTH=.0381;WIN=26.25;YAXIS=1.5*WIDTH;LENGTH=3.5*WIDTH TKEIN=(0.05*WIN)**2;EPSIN=TKEIN**1.5*0.1643/(0.09*WIDTH) GROUP 6. Body-fitted coordinates or grid distortion BFC=T;NONORT=T;NX=1 IF(FINEG) THEN + NY=25;NZ=80 + GSET(D,NX,NY,NZ,1.0,WIDTH,LENGTH) + GSET(P,A,0.0,0.0,LENGTH);GSET(P,B,0.0,WIDTH,LENGTH) + GSET(P,C,1.0,0.0,LENGTH);GSET(P,D,1.0,WIDTH,LENGTH) + GSET(L,LAB,A,B,NY,S1.7);GSET(L,LBD,B,D,NX,1.0) + GSET(L,LCD,C,D,NY,S1.7);GSET(L,LCA,C,A,NX,1.0) + GSET(F,FABCD,A,-,B,-,D,-,C,-) + GSET(M,FABCD,+J+I,1,1,1,TRANS) + GSET(C,K81,F,K1,+,0.0,0.0,0.0) + GSET(C,K81,F,K81,+,0.0,(YAXIS+0.5*WIDTH),0.0) ** k71-k51 cells in the outlet length + GSET(C,K51,F,K81,+,0.0,0.0,-LENGTH,INC,0.8) ** k51-k21 cells in the bend + GSET(C,K21,F,K51,RX,-3.14159,YAXIS,0.0,INC,1.0) ** k21-k1 cells in the inlet length + GSET(C,K1,F,K21,+,0.0,0.0,LENGTH,INC,1.2) ELSE + NY=20;NZ=40 + GSET(D,NX,NY,NZ,1.0,WIDTH,LENGTH) + GSET(P,A,0.0,0.0,LENGTH);GSET(P,B,0.0,WIDTH,LENGTH) + GSET(P,C,1.0,0.0,LENGTH);GSET(P,D,1.0,WIDTH,LENGTH) + GSET(L,LAB,A,B,NY,S1.7);GSET(L,LBD,B,D,NX,1.0) + GSET(L,LCD,C,D,NY,S1.7);GSET(L,LCA,C,A,NX,1.0) + GSET(F,FABCD,A,-,B,-,D,-,C,-) + GSET(M,FABCD,+J+I,1,1,1,TRANS) + GSET(C,K41,F,K1,+,0.0,0.0,0.0) + GSET(C,K41,F,K41,+,0.0,(YAXIS+0.5*WIDTH),0.0) ** k41-k31 cells in the outlet length + GSET(C,K31,F,K41,+,0.0,0.0,-LENGTH,INC,0.8) ** k31-k11 cells in the bend + GSET(C,K11,F,K31,RX,-3.14159,YAXIS,0.0,INC,1.0) ** k11-k1 cells in the inlet length + GSET(C,K1,F,K11,+,0.0,0.0,LENGTH,INC,1.2) ENDIF ** Set wup=t to account better for the high curvature of the w resolute... WUP=T GROUP 7. Variables stored, solved & named SOLVE(P1,V1,W1);SOLUTN(P1,Y,Y,Y,N,N,N);STORE(ENUT,LEN1) SOLUTN(V1,P,P,P,P,P,N);SOLUTN(W1,P,P,P,P,P,N) MESG( Enter the required turbulence model: MESG( CHEN - Chen-Kim k-e model MESG( KE - Standard k-e model MESG( KO - Wilcox k-o model MESG( RNG - RNG k-e model (default) MESG( READVDU(CTURB,CHAR,RNG) CASE :CTURB: OF WHEN CHEN,4 + TEXT(CHEN KIM K-E FLOW IN TURNAROUND DUCT :T106 + MESG(Chen-Kim k-e model + TURMOD(KECHEN);TLSC=EP WHEN KE,2 + TEXT(K-E FLOW IN TURNAROUND DUCT :T106 + MESG(Standard k-e model + TURMOD(KEMODL);TLSC=EP WHEN KO,2 + TEXT(K-OMEGA FLOW IN TURNAROUND DUCT :T106 + MESG(k-omega model + TURMOD(KOMODL);TLSC=OMEG + STORE(EP);EPSIN=EPSIN/(0.09*TKEIN) WHEN RNG,3 + MESG(RNG k-e model (default) + TURMOD(KERNG);TLSC=EP + STORE(ETA,ALF,GEN1);KELIN=1 + OUTPUT(ALF,Y,N,P,Y,Y,Y);OUTPUT(ETA,Y,N,P,Y,Y,Y) ENDCASE GROUP 9. Properties of the medium (or media) ENUL=WIN*WIDTH/REYNO GROUP 11. Initialization of variable or porosity fields FIINIT(P1)=1.E-10;FIINIT(W1)=WIN FIINIT(KE)=TKEIN;FIINIT(:TLSC:)=EPSIN GROUP 13. Boundary conditions and special sources INLET(BFCIN,LOW,#1,#1,#1,#NREGY,#1,#1,1,1) VALUE(BFCIN,P1,GRND1);VALUE(BFCIN,W1,GRND1) VALUE(BFCIN,WCRT,-WIN);VALUE(BFCIN,KE,TKEIN) VALUE(BFCIN,:TLSC:,EPSIN) * Transfer density for GXBFC subroutine BFCA=RHO1 PATCH(OUTLET,HIGH,#1,#1,#1,#NREGY,#NREGZ,#NREGZ,1,1) COVAL(OUTLET,P1,1.E4,0.0) COVAL(OUTLET,V1,ONLYMS,0.0);COVAL(OUTLET,W1,ONLYMS,0.0) ** N-wall WALL (WFNN,NORTH,1,NX,NY,NY,1,NZ,1,1) ** S2-wall WALL (WFNS,SOUTH,1,NX,1,1,1,NZ,1,1) GROUP 15. Termination of sweeps LSWEEP=20 REAL(MASIN,DTF);MASIN=WIDTH*WIN*RHO1 RESREF(P1)=1.E-12*MASIN RESREF(W1)=RESREF(P1)*WIN; RESREF(V1)=RESREF(W1) RESREF(KE)=RESREF(P1)*TKEIN; RESREF(:TLSC:)=RESREF(P1)*EPSIN GROUP 16. Termination of iterations LITER(P1)=10 GROUP 17. Under-relaxation devices RELAX(P1,LINRLX,0.5);DTF=ZWLAST/WIN/NZ RELAX(W1,FALSDT,DTF); RELAX(V1,FALSDT,DTF) RELAX(KE,FALSDT,DTF); RELAX(:TLSC:,FALSDT,DTF) GROUP 22. Spot-value print-out IYMON=2;IZMON=56;NPRMON=LSWEEP GROUP 23. Field print-out and plot control NPRINT=LSWEEP;ITABL=3;NPLT=2 NYPRIN=1;NZPRIN=1;IZPRF=18;IZPRL=24;TSTSWP=-1 ** activate printout of near-wall y+ values WALPRN=T