UDF for Pitching Wing

artkingjw · April 26, 2015, 10:34

Hello everyone!

I'm was wondering if you could simulate a changing angle of attack on a wing, without dynamic meshing - by simply changing the components of velocity to the inlet of the domain over time.

Unlike this thread, I am to study the effects of pitching/plunging motion on the airfoil. I have been told by my tutors that a UDF to vary the inlet velocity should do the trick, but I haven't found anything useful so far - mainly there is a lot of stuff on the velocity profile at the inlet, but not the direction.

I would appreciate any sort of guidance, thank you!

`e` · April 27, 2015, 04:40

Velocity is a vector quantity and therefore a velocity profile has both a speed and a direction. You'll need to have your inlet of type "velocity-inlet" and specify a velocity with components (each component, x, y and z has its own profile). Your simulation is transient and your inlet velocity is a function of time, therefore use the CURRENT_TIME macro to return the real current flow time [s]. Sounds like fun, let us know how you get on and if your results agree with literature!

artkingjw · April 27, 2015, 12:44

Quote:

Originally Posted by `e`

Velocity is a vector quantity and therefore a velocity profile has both a speed and a direction. You'll need to have your inlet of type "velocity-inlet" and specify a velocity with components (each component, x, y and z has its own profile). Your simulation is transient and your inlet velocity is a function of time, therefore use the CURRENT_TIME macro to return the real current flow time [s]. Sounds like fun, let us know how you get on and if your results agree with literature!

Oh i didn't know that. I always thought that the velocity profile function was intended to prescribe a weird profile of velocity to your inlet? (Example of what I mean... ) As opposed to be able to do what I want... Interesting! I'll look deeper.

`e` · April 28, 2015, 01:23

A profile used for boundary conditions (e.g. velocity profile) simply prescribes a value for each face of the boundary; this profile could be constant or otherwise a function of space or time. Your example of the pipe flow profile only has a nonzero speed in the axial direction (u) and therefore only requires an x-component velocity profile or a profile normal to the inlet boundary (parallel to the x-direction in your case).

artkingjw · May 5, 2015, 00:50

Update: I've changed my method, to instead use a UDF to define the angle of my airfoil. My airfoil is in a rotating mesh region, with an interface to a 'static' mesh. I seem to get it to work with constant angular displacement, but haven't got it running the way i wanted it to, with a driving function instead.

Varying the inlet velocity meant that my flow was hitting the walll - the wall effects were never really going away, so I had to find another way

How would you recommend doing the UDF of the rotating mesh then? what class of DEFINE_??? would that be? I'm thinking it would be an ADJUST one, with a CURRENT_TIME macro to check the time?

April 26, 2015, 10:34	UDF for Pitching Wing	#1
artkingjw Member Arthur Join Date: Apr 2015 Posts: 34 Rep Power: 11	Hello everyone! I'm was wondering if you could simulate a changing angle of attack on a wing, without dynamic meshing - by simply changing the components of velocity to the inlet of the domain over time. Unlike this thread, I am to study the effects of pitching/plunging motion on the airfoil. I have been told by my tutors that a UDF to vary the inlet velocity should do the trick, but I haven't found anything useful so far - mainly there is a lot of stuff on the velocity profile at the inlet, but not the direction. I would appreciate any sort of guidance, thank you!

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April 27, 2015, 04:40		#2
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	Velocity is a vector quantity and therefore a velocity profile has both a speed and a direction. You'll need to have your inlet of type "velocity-inlet" and specify a velocity with components (each component, x, y and z has its own profile). Your simulation is transient and your inlet velocity is a function of time, therefore use the CURRENT_TIME macro to return the real current flow time [s]. Sounds like fun, let us know how you get on and if your results agree with literature!

April 28, 2015, 01:23		#4
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	A profile used for boundary conditions (e.g. velocity profile) simply prescribes a value for each face of the boundary; this profile could be constant or otherwise a function of space or time. Your example of the pipe flow profile only has a nonzero speed in the axial direction (u) and therefore only requires an x-component velocity profile or a profile normal to the inlet boundary (parallel to the x-direction in your case).

May 5, 2015, 00:50		#5
artkingjw Member Arthur Join Date: Apr 2015 Posts: 34 Rep Power: 11	Update: I've changed my method, to instead use a UDF to define the angle of my airfoil. My airfoil is in a rotating mesh region, with an interface to a 'static' mesh. I seem to get it to work with constant angular displacement, but haven't got it running the way i wanted it to, with a driving function instead. Varying the inlet velocity meant that my flow was hitting the walll - the wall effects were never really going away, so I had to find another way How would you recommend doing the UDF of the rotating mesh then? what class of DEFINE_??? would that be? I'm thinking it would be an ADJUST one, with a CURRENT_TIME macro to check the time?