UDF for Pitching Wing

artkingjw · April 26, 2015, 11:34

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, 05:40

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, 13:44

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, 02:23

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, 01:50

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, 11:34	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!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Use UDF to change the attack angle of flow over 3D wing	nvtrieu	Fluent UDF and Scheme Programming	8	June 26, 2016 06:53
UDF Compilation Error - Loading Library - COMMON Problem! Help!	robtheslob	Fluent UDF and Scheme Programming	8	July 24, 2015 01:53
flapping wing UDF code	yahya_azizi	Fluent UDF and Scheme Programming	1	July 24, 2012 07:24
DEFINE_CG_MOTION for flapping wing UDF	xyzch001	Fluent UDF and Scheme Programming	0	December 14, 2011 09:39
DEFINE_GEOM UDF Problems	Pat	FLUENT	0	August 14, 2003 14:16

April 27, 2015, 05:40		#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, 02:23		#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, 01:50		#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?