Meseauring torque-energy in a sheet of material (air)

Using SimScale
1

I want to get an idea of the (plausible) torque-energy that is within a (circular) sheet within the material (air). So SIMSCALE calculated the velocities of air behind a tree and I want to get an idea of the amount of energy a rotating device could pick up in a (circular) sheet. Is there a way to calculate this?

I don’t want to simulate the rotating device (say a traditional wind mill sails; as a rotating volume), but I just want to get a reasonable (for comparative analysis) idea of the torque energy that could be generated (knowing the Ct [torque coefficient formula, which depends on the wind speed and an (pre)assumed rotation speed [rad/sec] around the center of this ciruclar sheet]).

Any hints how to calculate this from the present results of a Run?
I could grab a gray-scale velocities picture from the screen, determine the speeds in that grab for the circular sheet and then calculate for each dot the torque-energy from the center point of the circular sheet. But this is quite cumbersome. So is there a better/easier way in SIMSCALE?

Any hint, literature, example is welcome.

All the best,

Victor

2

Hello @molen_victor , that sounds a bit tricky.

What I would like to understand is that how can you directly relate air speed vs thrust coefficient without putting any geometrical information? Do you have some sort of empirical formula for a specific rotating device that presents a graph, or something else?

I think, rather than looking at velocity contours, creating probe points and obtaining velocity magnitudes should be more helpful.

3

Thanks for your reaction.

The geometric information is in this ‘circulair sheet’ (or rotational sheet, although SIMSCALE does not sup[port the idea of sheet…). It is like a ‘rotation volume’ but with thickness zero. The centre of the rotation sheet is the rotation point.
The user provides a torque coefficient (Ct=f(ucell/vcell)) depending on the rotationspeed (ucell) at a certain cell on this disc (at distance Rcell) and the windspeed (vcell).
So vcell at a location is calculated by SIMSCALE and ucell is de rotational speed of that cell depending on the distance from the rotation point (ohmegaRcell: ohmega is a user given rotation speed [rad/sec]).
So the torque is now the summation/integration of the torque of every cell in that rotational sheet:
torque = sum(over all cells in sheet) {Ct(ucell/vcell)AcellRcell(0.5rhovcell^2)}

rho = density medium (air)
Acell=area of the cell

So the user needs to give a formula for Ct(ucell/vcell) and a value for ohmega [rad/sec].

I understand this is perhaps not 100% scientific, but for comparisons between results of different parameters/media is might be enough.

Hope this explains my thoughts. Thanks for your feedback.