PHOTON USE p; parphi; 1 1 500 gr ou y 1 msg pressure; distance is vertical, time horizontal con p1 y 1 fi;1 msg Pressto continue pause;con off;red msg velocity; distance is vertical, time horizontal con u1 y 1 fi;1 enduse GROUP 1. Run title and other preliminaries TEXT(Pressure Waves From Valve Closure TITLE DISPLAY Air is moving steadily along a pipe. Valves are suddenly closed at each end, bringing the air to rest there. The subsequent distributions of velocity and pressure in the pipe are to be predicted. The analysis is one-dimensional, and the process is supposd to be isentropic, ie without either friction or heat transfer. ENDDIS GROUP 2 and 3 STEADY=F; tlast=0.01; lstep=100; xulast=2.0; nx=100 l(unigrid GROUP 7. Variables stored, solved & named SOLVE(P1,U1); STORE(RHO1) GROUP 8. Terms (in differential equations) & devices ** De-activate the diffusion term in the U1 equation TERMS(U1,Y,Y,N,Y,Y,Y) GROUP 9. Properties of the medium (or media) #FLUIDMAT SETPRPS(1,AIRISENT) REAL(REFPRE,REFRHO);REFPRE=1.E5;REFRHO=1.0 MESG(Isentropic Air, Refrho=:REFRHO:, Refpre=:REFPRE: RHO1A=REFRHO*(1.0/REFPRE)**RHO1B GROUP 11. Initialization of variable or porosity fields FIINIT(P1)=REFPRE; FIINIT(U1)=1.0; FIINIT(RHO1)=REFRHO GROUP 15. Termination of sweeps LSWEEP=10 GROUP 22. Spot-value print-out IXMON=NX/2; TSTSWP=-1 SPEDAT(SET,GXMONI,TRANSIENT,L,F) GROUP 23. Field print-out and plot control NTPRIN=LSTEP/5;NXPRIN=NX/5 PATCH(ALLX,PROFIL,1,NX,1,1,1,1,1,LSTEP) PLOT(ALLX,P1,0.0,0.0); PLOT(ALLX,U1,0.0,0.0) PATCH(TIMEPLOT,PROFIL,NX/2,NX/2,1,1,1,1,1,LSTEP) PLOT(TIMEPLOT,P1,0.0,0.0); PLOT(TIMEPLOT,U1,0.0,0.0) create parphi file for display via PHOTON IDISPA=1;IDISPB=1;IDISPC=LSTEP