PATCH(SOUTHWAL,SWALL,1,NX,1,1,1,NZ,1,LSTEP)
IF(NX.GT.1) THEN
 COVAL(SOUTHWAL,U1,1.0,0.0)
ENDIF   
IF(NZ.GT.1) THEN
 COVAL(SOUTHWAL,W1,1.0,0.0)
ENDIF