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initial conditions with transient UDF

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Old   September 17, 2004, 12:30
Default initial conditions with transient UDF
  #1
Antoine Pages
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Hi.

I use a transient UDF to simulate the flow around an oscillating NACA section. But the initial conditions are different each time I run a simulation (it is as if, in the function sin(2*pi*f*t), the time t was never the same at the beginning of the simulation); as a result, when I use the data of Cl and Cd registered, I never know which angle of incidence corresponds to each time step. How can I fix this problem?

Thank you for help.
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Old   September 17, 2004, 13:50
Default Re: initial conditions with transient UDF
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Aravind
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Hi,

Each time you run the problem, you NEED to initialize it, under Solve>initialize. You can also choose to initialize the problem from a Boundary, i guess in your case you need to initialize from the inlet.

Aravind
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Old   September 18, 2004, 06:26
Default Re: initial conditions with transient UDF
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Antoine Pages
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I initialize each time from the velocity inlet, but the initial values of x and y velocities (in the "solution initalization" panel) are different each time I do it. Do you know why?

Thank you.

Antoine
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Old   September 18, 2004, 12:37
Default Re: initial conditions with transient UDF
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Aravind
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Hi,

Since your velocity is a function of time, I am guessing that the time is not being initialized to zero at the beginning of the simulation. That means, the UDF is not getting initialized. Can you tell me the procedure, as to how are you doing your problem? may be, if you compiled your function and did the simulation, it might work! (not sure).Hope this helps.
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Old   September 19, 2004, 11:51
Default Re: initial conditions with transient UDF
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Antoine Pages
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In fact I hadn't checked all the data I had registered and it seems to be all right just with the initialization; the velocity seems to be intialized on the time step where the previous calculation has been stopped, but then after a few time steps the velocity computed is the velocity expected. Sorry about that and thank you for help.

PS: the compilation of the program between each calculation doesn't change anything to the intialization.
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