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?
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.
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.
