Integrating torque/force on boundary surface

rknop · March 10, 2016, 11:29

I'm new to SU2, so apologies if there's a quick and easy way to do this. I haven't been able to figure it out from the documentation.

I have a flow on an object. I've got an outer boundary (which is the steady-state flow), and an inner boundary (which is the one set with MARKER_MONITORING) in the config file.

The output files include surface_flow.csv, which gives me pressure, pressure coefficient, and skin friction coefficient for various x, y, z.

What I want to do is integrate these up to get the net force and net torque on the inner surface. However, surface_flow.csv doesn't include the effective areas that go with each x, y, z. As best I can determine, I will need to parse the mesh file to figure out both what area and what normal vector goes with each point given in the surface_flow.csv file if I want to get net torque and force on the inner boundary.

Does one of the other SU2 executables do this sort of thing for me? If so, which one, and where is it documented?

hlk · March 15, 2016, 20:33

Quote:

Originally Posted by rknop

I'm new to SU2, so apologies if there's a quick and easy way to do this. I haven't been able to figure it out from the documentation.

I have a flow on an object. I've got an outer boundary (which is the steady-state flow), and an inner boundary (which is the one set with MARKER_MONITORING) in the config file.

The output files include surface_flow.csv, which gives me pressure, pressure coefficient, and skin friction coefficient for various x, y, z.

What I want to do is integrate these up to get the net force and net torque on the inner surface. However, surface_flow.csv doesn't include the effective areas that go with each x, y, z. As best I can determine, I will need to parse the mesh file to figure out both what area and what normal vector goes with each point given in the surface_flow.csv file if I want to get net torque and force on the inner boundary.

Does one of the other SU2 executables do this sort of thing for me? If so, which one, and where is it documented?

Thanks for the question
The values you are asking about are output to the history file, you don't need to compute these yourself.

rknop · March 16, 2016, 13:14

Oh! Heh. Duh. I feel kind of stupid now; I didn't think to look at the history file.

I also discovered that putting in the right few filters into paraview can accomplish this integral.

rknop · March 16, 2016, 14:39

Are the definitions of these values documented anywhere? I see variables called "CFx", "CMx", and so forth. I'm *guessing* that these are the net forces, i.e. the surface integral of the pressure times the normal unit vector. Is that in fact what they are? Or are they scaled to something else somewhere in the problem?

The number also doesn't match what I'm getting doing the integral in Paraview, which means I'm almost certainly doing something wrong.

March 10, 2016, 11:29	Integrating torque/force on boundary surface	#1
rknop New Member Rob Knop Join Date: Mar 2016 Location: Western PA Posts: 5 Rep Power: 10	I'm new to SU2, so apologies if there's a quick and easy way to do this. I haven't been able to figure it out from the documentation. I have a flow on an object. I've got an outer boundary (which is the steady-state flow), and an inner boundary (which is the one set with MARKER_MONITORING) in the config file. The output files include surface_flow.csv, which gives me pressure, pressure coefficient, and skin friction coefficient for various x, y, z. What I want to do is integrate these up to get the net force and net torque on the inner surface. However, surface_flow.csv doesn't include the effective areas that go with each x, y, z. As best I can determine, I will need to parse the mesh file to figure out both what area and what normal vector goes with each point given in the surface_flow.csv file if I want to get net torque and force on the inner boundary. Does one of the other SU2 executables do this sort of thing for me? If so, which one, and where is it documented?

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March 16, 2016, 13:14		#3
rknop New Member Rob Knop Join Date: Mar 2016 Location: Western PA Posts: 5 Rep Power: 10	Oh! Heh. Duh. I feel kind of stupid now; I didn't think to look at the history file. I also discovered that putting in the right few filters into paraview can accomplish this integral.

March 16, 2016, 14:39		#4
rknop New Member Rob Knop Join Date: Mar 2016 Location: Western PA Posts: 5 Rep Power: 10	Are the definitions of these values documented anywhere? I see variables called "CFx", "CMx", and so forth. I'm guessing that these are the net forces, i.e. the surface integral of the pressure times the normal unit vector. Is that in fact what they are? Or are they scaled to something else somewhere in the problem? The number also doesn't match what I'm getting doing the integral in Paraview, which means I'm almost certainly doing something wrong.