CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   CFX (http://www.cfd-online.com/Forums/cfx/)
-   -   actuator disk (http://www.cfd-online.com/Forums/cfx/18773-actuator-disk.html)

Atit December 31, 2001 03:50

actuator disk
 
Dear sir, I use CFX 5.4.1. I would like to add the actuator disk in my flow field. The concept of actuator disk is just the disk that has no thickness. For example, my problem is that the flow is passed the actuator disk and then the total engergy of the main flow is reduced because the flow did some work on the disk. It like flow pass the turbine, but this turbine has no thickness. In modeling sense, I think that it just like the flow pass one plane and then the energy decrease. However I have no idea how to create such thing in CFX. Could you please sugest me how to create the actuator disk in CFX? Thank you very much sir. Atit

lawrence January 10, 2002 01:03

Re: actuator disk
 
Hello. I am not very sure what's your meaning of actuator disk. But if you mean that it is a single disk with zero thickness put in the flow field which can hold up the flow, I suggest the following: 1. In the CFX5, Creat a solid that includes the whole computational field as domain. 2. Creat a solid, on which there is one surface as the actuator disk, as an subdomain. 3. In boundary conditions, select one subdomain surface(which is also the actuator disk) as wall, the TYPE is THINSURFACE.

Hope this will be hopeful to you


Atit January 10, 2002 04:27

Re: actuator disk
 
Thank you for your suggestion. But I afraid that the concept of actuator disk may differ from your suggestion. The actuator disk is not a wall. It like a fan or the turbine. When the fluid flow through an actuator disk, it like the fluid flow through the turbine. The flow will lost energy, because it do work on the disk. However, because the disk has no thickness, no part of the disk will disrupt the flow. Then the particle of the fluid that pass through the disk will have the same order as it be before it pass the disk.

stuart January 16, 2002 08:44

Re: actuator disk
 
Hi Atit, I've herd of people modelling wind turbines where they do not model the blades explicitly. What they do is model the blads as a pressure drop. To do this in CFX541 I think the only way would be to set up a subdomain (all be it this) and then apply a resistance term to the subdomain to give you the pressure drop across the blades. Hope this helps Stuart

OPQ March 2, 2002 02:20

Re: actuator disk
 
Hi,Atit,

I know your problem quite well because i am now dedicated on the aerodynamic calculation of turbomachinery by use of actuator disk theory.

I don't think CFX is adaptable while you solve your problems using acutator disk theory.

I think it's easy to programme by yourself with the actuator disk theory. If you have any problem, mail me.

c120613 April 26, 2010 07:09

Actuator disk
 
Quote:

Originally Posted by OPQ
;63499
Hi,Atit,

I know your problem quite well because i am now dedicated on the aerodynamic calculation of turbomachinery by use of actuator disk theory.

I don't think CFX is adaptable while you solve your problems using acutator disk theory.

I think it's easy to programme by yourself with the actuator disk theory. If you have any problem, mail me.

Hi guys,

me too I have the same problem because I'm modelling an aero-engine intake and at the outlet section I'd like to introduce an actuator disk in order to introduce the effect of the fan compressor. I'm doing everything with ANSYS CFX. is it possible to introduce the actuator disk model inside of the CFX PRE as well?

Kind regards

Domenico

Aero75 May 4, 2010 03:53

Hi Atit,

I just want to share with you that actuator disc modelling can be done in CFX.

I have done this before. As I work for a commercial company, I can't share the details.

In order to solve the problem, you should not use the porous material approach as suggested, as I don't believe it will give you enough control of the problem. You should rather think of it as this: If you know the size of the aerodynamics forces on the subject you want to model with the disc (you may not, but if you don't, actuator disc methods are not what you should use...), you can use this knowledge to calculate the opposite counteracting volume forces working on the fluid. These forces can be applied through momentum source terms in a sub-domain. If you want to make a cool model, you find a way to estimate these forces (the actuator disc theory) based on the modelled flow field, which is again based on the applied forces - i.e. the right forces and thus the right corresponding flow field are found in an iterative manner.

As stated above, it can be done, but it requires you to look further into the theory of actuator discs. Once you have this set, you can actually extend your concept to actuator 'lines'

Good luck with your model,

Aero75

Rkeck July 5, 2013 14:06

Actuator disc in CFX is by CEL
 
The easiest (and most computationally effective) way to implement an actuator disc model in CFX is by programming it in the CEL language in the solver. That way no extra domains or sliding mesh considerations are needed.

I have published an academic paper that describes how to implement an actuator disc (& line) model in CFX using CEL language. See link:
http://www.sciencedirect.com/science...60148112002455

liladhar November 6, 2013 05:10

actuator disk
 
dear Rkeck
thaks for your valuable suggestions. I read your paper. i got some light still i could not understand it fully. I created a variable called "StepRotor". i imported the axial and rotational velocities as functions. But didnt understood how to get FN(r). can u suggest me how to get that?


All times are GMT -4. The time now is 13:42.