GROUP 1. Run title L(W900) TEXT(STRATIFIED FLOW, CASE 2 PIPE : W901 TITLE GROUP 13. Boundary conditions and special sources ** Force along pipe resulting from gravity at right angles The next three entries introduce a momentum source into the equation for the second-phase velocity which is equal to the difference of hydrostatic pressure caused by a difference in volume fraction from one computational cell to the next. HGSOA is simply an iteration-cut-off criterion, used in a sequence which calculates the cross-sectional area of the water-filled part of the pipe from the volume fraction. BUOYA carries the gravitational acceleration; HGSOB carries the density difference; and YVLAST represents the pipe radius. PATCH(LATG,CELL,1,NX,1,1,1,1,1,LSTEP) COVAL(LATG,2U,FIXFLU,GRND10) HGSOA=0.0001;BUOYA=9.81;HGSOB=RHO1-RHO2;YVLAST=0.5;IROTAA=3