# Can I simulate multiple velocities at same time step in transient simulation?

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 View Poll Results: Can we control change any parameter such as velocity at each time step in transient? yes 1 100.00% no 0 0% Voters: 1. You may not vote on this poll

 March 13, 2021, 20:37 Can I simulate multiple velocities at same time step in transient simulation? #1 New Member   Muhammad Atif Join Date: Jul 2019 Posts: 2 Rep Power: 0 Hello, I am running a transient simulation (using ANSYS2020R2) to study the effect of deflector position on the drag force of a tractor-trailer. I have written a UDF with CG_MOTION macro to rotate the deflector up and down which is working fine so far. My next task is to rotate the deflector lets say, 1 degree (1st-time step) and before moving it to 2 degrees, I want to see the effect of different velocities (e.g 40 to 60mph) at this time step. I also want to see the effect of changing the yaw angle (0,10,20,30 degree etc.) when deflector is at 1 degree. Once all the yaw angles and velocities are solved for the first-time step then I want to change the angle of the deflector to 2 degrees (by changing to the next time step) and perform the same calculations again. One way of doing is creating a separate project for each yaw angle and run multiple analysis which is a very hectic and time-consuming process. I was wondering if there is a way to do it with UDF. Take one velocity and run a defined number of iteration to reach convergence then change velocity for the same time step and deflector position, and iterate again. once all velocities are done, change time to the next time step (which will change deflector to 2 degrees) and perform same velocity calculations again. Any suggestion on how this can be achieved? Can we actually change velocity at a one-time step and iterate it again and again for different 3 4 velocities and then move to the next time step and repeat same calculations? I hope my question is making sense to you.

 May 12, 2021, 05:08 #2 New Member   Join Date: May 2019 Location: I'm a Queenslander Posts: 19 Rep Power: 4 makes sense to me.... if you figure it out Id be interested

 May 13, 2021, 02:01 #3 Senior Member   Alexander Join Date: Apr 2013 Posts: 1,760 Rep Power: 28 Code: `Can we actually change velocity at a one-time step and iterate it again and again for different 3 4 velocities and then move to the next time step and repeat same calculations?` this is not possible as far as I know (within one timestep) __________________ best regards ****************************** press LIKE if this message was helpful

 Tags coding, fluent, iteration, time step, udf