# How to add X and Y forces at a point

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 February 9, 2015, 13:29 How to add X and Y forces at a point #1 New Member   Join Date: Mar 2014 Posts: 5 Rep Power: 4 Hello, I am trying simulate a plasma actuator on an airfoil. To do so, I need to add a force in the x and y directions to specific points in the domain. I am currently trying to add the force in "numerics_direct_mean.cpp". When the code passes through a certain array of points, I add the following to each location: val_residual[1] = Volume * fx; val_residual[2] = Volume * fy; However, I am not getting the results I expect. Do val_residual [1] and [2] add forces to the x and y directions, respectively? Or is there another way to add the forces? The simulations use Euler equations with a NACA0012 airfoil at a 10 degree angle of attack. Thank you

February 10, 2015, 22:06
#2
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Heather Kline
Join Date: Jun 2013
Posts: 246
Rep Power: 6
Quote:
 Originally Posted by cgusty01 Hello, I am trying simulate a plasma actuator on an airfoil. To do so, I need to add a force in the x and y directions to specific points in the domain. I am currently trying to add the force in "numerics_direct_mean.cpp". When the code passes through a certain array of points, I add the following to each location: val_residual[1] = Volume * fx; val_residual[2] = Volume * fy; However, I am not getting the results I expect. Do val_residual [1] and [2] add forces to the x and y directions, respectively? Or is there another way to add the forces? The simulations use Euler equations with a NACA0012 airfoil at a 10 degree angle of attack. Thank you
Review the discretization of the Euler equations to make sure that setting the residual of the momentum flux to force*volume is actually what you want to do here. A good source is Numerical Computation of Internal & External Flows by Hirsch. Check that the residual is being updated in the linear system through a LinSysRes method, and review the other boundary conditions to see how these things are handled elsewhere in the code - there are often additional steps beyond setting a residual. It may be better to created a new boundary condition for what you are trying to do.

 February 12, 2015, 15:16 #3 New Member   Join Date: Mar 2014 Posts: 5 Rep Power: 4 Thank you for your answer. I am trying to add a volumetric force, not a boundary force. I do call LinSysRes. My question is if elements 1 and 2 in val_residual[] correspond to the x- and y- momentum equations.

 February 18, 2015, 05:18 #4 New Member   Matt Wright Join Date: Feb 2015 Posts: 5 Rep Power: 3 Hi, Have you managed to get much further with this? I'm trying to do a similar thing for my 3rd year project without success. Would it be possible if you could post your code up? Many Thanks

 February 18, 2015, 14:17 #5 Super Moderator   Francisco Palacios Join Date: Jan 2013 Location: Long Beach, CA Posts: 342 Rep Power: 6 Hi all, My recommendation is to take a look at void CEulerSolver::Source_Residual(CGeometry *geometry, CSolver **solver_container, CNumerics *numerics, CNumerics *second_numerics, CConfig *config, unsigned short iMesh) there are several examples there and, depending of the complexity of the source term, we directly compute the residual at that subroutine or we use the numerics structure. In particular the free surface or time_spectral examples are quite clear. Thanks for using SU2, Best Francisco Palacios SU2 lead developer

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