Gradients for Thrust and Torque coefficients using Finite Differences

Daaman · July 18, 2021, 12:35

Hi,

I want to verify the gradients of thrust and torque coefficients that I have obtained using discrete adjoint, against the finite differences. But, the gradients for thrust and torque are not mentioned in the list of gradients generated on implementing finite differences. In literature, I do see that it was one of the options for Finite Differences - http://adl.stanford.edu/papers/AIAA_...Rotor_2012.pdf. I'm using v 7.1.1. How can I generate the gradients for the thrust and torque coefficients using FD?

Thanks!

Daaman · July 19, 2021, 06:46

After comparing the gradients,

Ct (Thrust coefficient) = -CFz (Coefficient of Force-Z)
Cq (Torque coefficient) = -Cmz (Coefficient of Moment-Z)

After going through the literature, I think the above convention is used in the latest version, whereas in the older versions coefficient of Force-X was used for Thrust. But this could be case-dependent based on the axis of rotation.

July 18, 2021, 12:35	Gradients for Thrust and Torque coefficients using Finite Differences	#1
Daaman Member Join Date: Jun 2020 Posts: 30 Rep Power: 6	Hi, I want to verify the gradients of thrust and torque coefficients that I have obtained using discrete adjoint, against the finite differences. But, the gradients for thrust and torque are not mentioned in the list of gradients generated on implementing finite differences. In literature, I do see that it was one of the options for Finite Differences - http://adl.stanford.edu/papers/AIAA_...Rotor_2012.pdf. I'm using v 7.1.1. How can I generate the gradients for the thrust and torque coefficients using FD? Thanks!

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July 19, 2021, 06:46		#2
Daaman Member Join Date: Jun 2020 Posts: 30 Rep Power: 6	After comparing the gradients, Ct (Thrust coefficient) = -CFz (Coefficient of Force-Z) Cq (Torque coefficient) = -Cmz (Coefficient of Moment-Z) After going through the literature, I think the above convention is used in the latest version, whereas in the older versions coefficient of Force-X was used for Thrust. But this could be case-dependent based on the axis of rotation.