UDF at pressure inlet[pleas help me!!]
Hello All,
I would like to increase pressure and temperature at pressure inlet boundary. As like this, 1~1000 iteration : pressure - 101325 pa, temperature - 250K 1001~2000 iteration : pressure - 101325* 2 , temperature - 500K How do i do complete my goal? I could compile and hook, but it is all!! I try to code UDF to find a solution by myself. but it does not work!! |
Kokoory,
A few things: 1) Are you really trying to change boundary conditions on a per-iteration basis? Is this a steady state or a transient problem? If you're actually trying to do a steady state simulation and you want to change inlet conditions after a specified number of iterations, don't. Simply put your boundary conditions to what you want them to be at t=infinity and let the simulation solve. 2) If you're trying to solve a transient case, and by iterations you mean "time steps" or "simulation time, in seconds" have a look at this Time dependent flows in Fluent with UDFs 3) Finally, more of a numerics issue...The changes you're imposing are fairly dramatic over what, presumably, will be a short period of time. This often causes convergence difficulties, and rightfully so -- the physics you're trying to impose are almost non-physical. In one timestep (very short) the pressure and temperature across an entire face double. Typically, one would impose a slightly more gentle ramp than a step change, and take fractional timesteps in the "in between" part to allow the solver to get to a more stable answer. I hope this helps! ComputerGuy |
Thanks, ComputerGuy.
I refer your opinion for the model. So, I use the below code for pressure and temperature. Code:
#include "udf.h" Code:
#include "udf.h" For pressure code, I hook to Gauge total pressure and for temperaturee code, to temperature. Next, I set the time step size = 0.001 and number of time steps = 10000 and Max iterations per step = 1. Because I would like to increase the pressure at 1013250 and the temperature at 2500K after all calculating. Is it OK what I thought to be? |
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