I am trying to simulate a vertical axis wind turbine of darrieus model and i am getting a negative torque. I have followed frame motion, relative to adjacent cell method, and solution method as simple, standard initialization. Can anyone please help me?
Hi Venkata Sujanth Cherukuri
first of all, if you mean that you had a minus sign behind your torque number it is ok because probably the turbine is rotating in a clockwise direction and the flow is coming to the turbine that gives negative torque automatically and you should consider it as positive(Based on right-hand rule). But if you are getting minus torque in concept, then you should check your geometry modeling. On the other hand, the flow around the vertical axis turbine is more unsteady in contrast to the horizontal axis turbine. So, be sure you are using the transient model. Besides, it better uses sliding mesh for vertical axis turbine as you can search and see it in different references. Checking the mesh quality should not be forgotten.
Are you getting negative torque for all tipspeed ratios?
It might be because the VAWT is unable to accelerate through a dead band around TSR = 1.
Use the absolute value. Your are getting a negative tswisting force (torque) because the force is oriented toward the opposite direction of the axis. Just change the orientation of your axis to obtain a positive twisting force.
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