[seyedashraf]

Originally Posted by cleoo

what if you don't know the velocity?

Then you may have the pressure. in that case try bernoulli's principle.

[ViLaks]

Dear All,

Sorry for restarting the thread, I just need to know the total time my transcient simulation ran in Fluent. Following are the parametrs I gave as input:

Time Stepping Method: Fixed
Time Step Size (s) : 0.5
No: of Time Steps : 200
Max Itr/Time Step: 20

Is it right that my simulation has run for (200*0.5) 100 s ??

If yes, then my simulation is wrong. I am simulating natural convection inside a deep freezer whose walls are at -20 deg celsius and air inside is at 43 degree celsius. I need to calculate time needed for air to cool down to -18 deg celsius. If the simulation is run for 100 s, I get the result. But it is wrong right. 43 to -18 deg celsius in just 1.5 mins?

Thanks and Regards
Vignesh

[AlexanderZ]

(200*0.5s) = 100s

Best regards

[erfanpournasiri]

hi i have problem to find non dimensional time step
this formul is ut/D and D=0.04 , U According to Re=100 dansity=1000 and viscosity=0.001002
it will be obtained U=0.0025m/s non dimensional time will bw obtained 77 how can do it?

[waseeqsiddiqui]

If we have the smallest grid size at high Mach approximately in the magnitude 10^7 (y plus), then the time step size would be even lower (~10^10) and Courant would be crazy high, according to the formulation described above. Am I right?

[duri]

Courant number is a scaling factor. T=C X/abs(u)+a C is 1 is the fastest wave travels a distance of X.

[Lok]

HI,
I am new to ansys, i am simulating a liquid piston compressor i.e. water is used to compress gas inside cylinder. i am applying velocity inlet boundary condition with gauge pressure (30 bar) (the inlet is water completely), inside the gas is at 7 bar. I want the simulation to stop when pressure of air gets equal to water pressure i.e. 30 bar. how to set up boundary condition??
Also how to choose number of iteration and time steps??

Thanks in advance