****** TO LOAD CASE 108:TYPE L(N108) *****
GROUP 1. Run title and other preliminaries
TEXT(2D LAMINAR FLOW OVER A FENCE: N108
TITLE
mesg(PC486/50 time last reported as appx. 16 min
DISPLAY
The case considered is 2d laminar incompressible flow over a
thin fence of height H located in a planar channel with a
blockage ratio S/H=0.75. The flow Reynolds number is 82.5 based
on fence height S and inlet bulk velocity Uin. This situation
has been studied experimentally and numerically by Carvalho et
al (Appl.Math.Modelling, Vol.11, p23, (1987) ). The boundary
conditions correspond to an inlet flow of fully-developed
parabolic velocity profile located at 8 fence heights upstream
of the fence, and an outlet condition of fixed pressure at 15
fence heights downstream of the fence, and no-slip conditions
at the walls. In practice the fence thickness is t/H=0.133,
but in the calculations it is taken as zero.
The present calculation is performed in all six planes as a
consistency test. The default calculation is made with the
linear-upwind scheme (LUS) for momentum, and the option exists
to make the calculation with the HYBRID scheme. A mesh of 24
vertical by 48 horizontal cells has been used in the
calculations.
ENDDIS
Experiments indicate that a primary recirculation zone develops
behind the fence with a reattachment length of X1/S=4.4, as
measured from the fence. An additional separation cell forms on
the upper wall of the channel with the separation point located
at X2/S=4.0 and the reattachment point at X3/S=6.0, yielding a
separation length of DX/S=2.0. The main results may be summarised
as follows:
Data Hybrid Linear-Upwind
X1/S 4.4 5.56 4.96
X2/S 4.0 4.21 3.85
X3/S 6.0 6.72 8.62
DX/S 2.0 2.51 4.77
Although no grid-refinement studies have been performed, the
results are in reasonable agreement with the data.
PHOTON USE
P
0.20443E+04 0.15633E+04 CR
GR OU Z 1;GR Z 1 COL 3;GR X 13 13 Y 1 12 COL 15
STREAM 2D Z 1 X 4 35 Y 1 M
-.199E-2 .642E-3 10
set order
1
4
5
2
6
7
3
MAG GR 2
0.16213E+04 0.17326E+04 CR
msg Streamlines
msg press
pause
stream off;grid off 2;redr
msg vectors
vec z 1 sh
msg press and then to end
pause
ENDUSE
AUTOPLOT USE
file
phi 5
d 1 u1 y 1;d 1 u1 y m;div x 7.5e-3 1 2;shift x -8 1 2
col3 1;colf 2;level y 0;scale x 0 10;scale y -.3 .25;
msg horizontal velocity along bottom & top walls behind fence
msg separation & reattachment points when U1 passes through zero
msg blue line - U1 along bottom wall
msg red line - U1 along top wall
msg press to continue
msg press to end
ENDUSE
REAL(YG,YFP,YFM,CWID2,DTF,CWID,CDOWN,CUP,CLEN,SFENCE,REYNO)
REAL(UBIN,UIN,SBLOCK)
INTEGER(NVFENC,NVGAP,NHUP,NHDOWN)
CHAR(SCHM,DIRV,DIRH,VELV,VELH,PLANE)
** Calculation of domain specifications
CWID=0.01;SBLOCK=0.75;SFENCE=SBLOCK*CWID;CUP=8.*SFENCE
CDOWN=15.*SFENCE;CLEN=CUP+CDOWN;REYNO=82.5
NVFENC=10+2;NVGAP=10+2;NHUP=12;NHDOWN=28;nhdown=36
ENUL=1.8E-5;RHO1=1.2;UBIN=REYNO*ENUL/SFENCE
CWID2=CWID*CWID
MESG( Enter required vertical coordinate X,Y or Z
MESG( Default: Y
READVDU(DIRV,CHAR,Y)
CASE :DIRV: OF
WHEN X,1
+ NREGX=2;VELV=U1
WHEN Y,1
+ NREGY=2;VELV=V1
WHEN Z,1
+ NREGZ=2;VELV=W1
ENDCASE
MESG( Enter required horizontal coordinate X,Y or Z
MESG( Default: X
READVDU(DIRH,CHAR,X)
CASE :DIRH: OF
WHEN X,1
+ NREGX=2;VELH=U1
WHEN Y,1
+ NREGY=2;VELH=V1
WHEN Z,1
+ NREGZ=2;VELH=W1
ENDCASE
PLANE=:DIRV::DIRH:
TEXT(2D:PLANE: LAMINAR FLOW OVER A FENCE: N108
GROUP 3. X-direction grid specification
GROUP 4. Y-direction grid specification
** channel length = 0.762 & channel width = 0.1143
IREG:DIRH:=1;GRDPWR(:DIRH:,NHUP,CUP,-1.2)
IREG:DIRH:=2;GRDPWR(:DIRH:,NHDOWN,CDOWN,1.3)
IREG:DIRV:=1;GRDPWR(:DIRV:,NVFENC,SFENCE,-1.2)
IREG:DIRV:=2;GRDPWR(:DIRV:,NVGAP,CWID-SFENCE,-1.3)
GROUP 7. Variables stored, solved & named
SOLVE(P1,:VELH:,:VELV:);SOLUTN(P1,Y,Y,Y,P,P,P)
GROUP 8. Terms (in differential equations) & devices
MESG( Enter required convection scheme
MESG( Default: LUS - Linear upwind for momentum Scheme
MESG( The alternative is:
MESG( HYB - Hybrid Differencing Scheme for all variables
READVDU(SCHM,CHAR,LUS)
CASE :SCHM: OF
WHEN HYB,3
+ MESG(Hybrid-differencing scheme
+ DIFCUT=0.5;DTF=CLEN/UBIN
+ LSWEEP=800
WHEN LUS,3
+ MESG(Linear upwind scheme for momentum
+ SCHEME(LUS,:VELH:,:VELV:)
+ DTF=0.06*CLEN/(UBIN*N:DIRH:)
+ LSWEEP=1600
ENDCASE
GROUP 9. Properties of the medium (or media)
GROUP 11. Initialization of variable or porosity fields
FIINIT(:VELH:)=UBIN;FIINIT(:VELV:)=0.1*UBIN
GROUP 13. Boundary conditions and special sources
IF(:PLANE:.EQ.YX) THEN
+ CONPOR(FENCE,0.0,EAST,-%1,-%1,-#1,-#1,#1,#1)
+ PATCH(OUTLET,EAST,#NREGX,#NREGX,#1,#NREGY,#1,#1,1,1)
+ WALL (TOP,NORTH,#1,#NREGX,#NREGY,#NREGY,#1,#1,1,1)
+ WALL (BOT,SOUTH,#1,#NREGX,#1,#1,#1,#1,1,1)
** Inlet velocity profile: u(y)/uav = {6y(cwid-y)}/cwid**2
umax/uav=1.5 at y=cwid/2.
+ YFM=0.
DO JJ=1,NY
+ YFP=YFRAC(JJ)*YVLAST;YG=0.5*(YFP+YFM)
+ UIN=6.0*UBIN*YG*(CWID-YG)/CWID2;YFM=YFP
+ PATCH(IN:JJ:,WEST,1,1,JJ,JJ,1,NZ,1,LSTEP)
+ COVAL(IN:JJ:,P1,FIXFLU,RHO1*UIN)
+ COVAL(IN:JJ:,U1,ONLYMS,UIN);COVAL(IN:JJ:,V1,ONLYMS,0.0)
ENDDO
ENDIF
IF(:PLANE:.EQ.XY) THEN
+ CONPOR(FENCE,0.0,NORTH,-#1,-#1,-%1,-%1,#1,#1)
+ PATCH(OUTLET,NORTH,#1,#NREGX,#NREGY,#NREGY,#1,#1,1,1)
+ WALL (TOP,EAST,#NREGX,#NREGX,#1,#NREGY,#1,#1,1,1)
+ WALL (BOT,WEST,#1,#1,#1,#NREGY,#1,#1,1,1)
+ YFM=0.
DO JJ=1,NX
+ YFP=XFRAC(JJ)*XULAST;YG=0.5*(YFP+YFM)
+ UIN=6.0*UBIN*YG*(CWID-YG)/CWID2;YFM=YFP
+ PATCH(IN:JJ:,SOUTH,JJ,JJ,1,1,1,NZ,1,LSTEP)
+ COVAL(IN:JJ:,P1,FIXFLU,RHO1*UIN)
+ COVAL(IN:JJ:,U1,ONLYMS,0.0);COVAL(IN:JJ:,V1,ONLYMS,UIN)
ENDDO
ENDIF
IF(:PLANE:.EQ.YZ) THEN
+ CONPOR(FENCE,0.0,HIGH,#1,#1,-#1,-#1,-%1,-%1)
+ PATCH(OUTLET,HIGH,1,1,#1,#NREGY,#NREGZ,#NREGZ,1,1)
+ WALL (TOP,NORTH,1,1,#NREGY,#NREGY,#1,#NREGZ,1,1)
+ WALL (BOT,SOUTH,1,1,#1,#1,#1,#NREGZ,1,1)
+ YFM=0.
DO JJ=1,NY
+ YFP=YFRAC(JJ)*YVLAST;YG=0.5*(YFP+YFM)
+ UIN=6.0*UBIN*YG*(CWID-YG)/CWID2;YFM=YFP
+ PATCH(IN:JJ:,LOW,1,NX,JJ,JJ,1,1,1,LSTEP)
+ COVAL(IN:JJ:,P1,FIXFLU,RHO1*UIN)
+ COVAL(IN:JJ:,W1,ONLYMS,UIN);COVAL(IN:JJ:,V1,ONLYMS,0.0)
ENDDO
ENDIF
IF(:PLANE:.EQ.ZY) THEN
+ CONPOR(FENCE,0.0,NORTH,#1,#1,-%1,-%1,-#1,-#1)
+ PATCH(OUTLET,NORTH,1,1,#NREGY,#NREGY,#1,#NREGZ,1,1)
+ WALL (TOP,HIGH,1,1,#1,#NREGY,#NREGZ,#NREGZ,1,1)
+ WALL (BOT,LOW,1,1,#1,#NREGY,#1,#1,1,1)
+ YFM=0.
DO JJ=1,NZ
+ YFP=ZFRAC(JJ)*ZWLAST;YG=0.5*(YFP+YFM)
+ UIN=6.0*UBIN*YG*(CWID-YG)/CWID2;YFM=YFP
+ PATCH(IN:JJ:,SOUTH,1,1,1,1,JJ,JJ,1,LSTEP)
+ COVAL(IN:JJ:,P1,FIXFLU,RHO1*UIN)
+ COVAL(IN:JJ:,V1,ONLYMS,UIN);COVAL(IN:JJ:,W1,ONLYMS,0.0)
ENDDO
ENDIF
IF(:PLANE:.EQ.XZ) THEN
+ CONPOR(FENCE,0.0,HIGH,-#1,-#1,#1,#1,-%1,-%1)
+ PATCH(OUTLET,HIGH,#1,#NREGX,1,1,#NREGZ,#NREGZ,1,1)
+ WALL (TOP,EAST,#NREGX,#NREGX,1,1,#1,#NREGZ,1,1)
+ WALL (BOT,WEST,#1,#1,1,1,#1,#NREGZ,1,1)
+ YFM=0.
DO JJ=1,NX
+ YFP=XFRAC(JJ)*XULAST;YG=0.5*(YFP+YFM)
+ UIN=6.0*UBIN*YG*(CWID-YG)/CWID2;YFM=YFP
+ PATCH(IN:JJ:,LOW,JJ,JJ,1,NY,1,1,1,LSTEP)
+ COVAL(IN:JJ:,P1,FIXFLU,RHO1*UIN)
+ COVAL(IN:JJ:,W1,ONLYMS,UIN);COVAL(IN:JJ:,U1,ONLYMS,0.0)
ENDDO
ENDIF
IF(:PLANE:.EQ.ZX) THEN
+ CONPOR(FENCE,0.0,EAST,-%1,-%1,#1,#1,-#1,-#1)
+ PATCH(OUTLET,EAST,#NREGX,#NREGX,1,1,#1,#NREGZ,1,1)
+ WALL (TOP,HIGH,#1,#NREGX,1,1,#NREGZ,#NREGZ,1,1)
+ WALL (BOT,LOW,#1,#NREGX,1,1,#1,#1,1,1)
+ YFM=0.
DO JJ=1,NZ
+ YFP=ZFRAC(JJ)*ZWLAST;YG=0.5*(YFP+YFM)
+ UIN=6.0*UBIN*YG*(CWID-YG)/CWID2;YFM=YFP
+ PATCH(IN:JJ:,WEST,1,1,1,NY,JJ,JJ,1,LSTEP)
+ COVAL(IN:JJ:,P1,FIXFLU,RHO1*UIN)
+ COVAL(IN:JJ:,U1,ONLYMS,UIN);COVAL(IN:JJ:,W1,ONLYMS,0.0)
ENDDO
ENDIF
COVAL(OUTLET,P1,1.E3,0.0)
COVAL(OUTLET,:VELH:,ONLYMS,0.0);COVAL(OUTLET,:VELV:,ONLYMS,0.0)
GROUP 17. Under-relaxation devices
RELAX(:VELH:,FALSDT,DTF);RELAX(:VELV:,FALSDT,DTF)
I:DIRV:MON=NVFENC-2;I:DIRH:MON=NHUP+12;NPRMON=100
GROUP 23. Field print-out and plot control
TSTSWP=-1;ITABL=3;NPLT=20;IPLTL=LSWEEP
NSAVE=PH:PLANE: