open TELEMAC-MASCARET The mathematically superior suite of solvers

Apologies, heres the steering file as well.

Hello,

Well as soon as you have set VERTICAL STRUCTURES = YES, the subroutine is called so it should have an effect. You can have a look at the test case called dragforce, where the effect is clearly visible. In your case the domain is probably large and the effect rather small, you can at least check that FUDRAG and FVDRAG at the end of your subroutine are not 0.

Regards,

Jean-Michel Hervouet

Thanks Jean-Michel, I checked the FUDRAG and FVDRAG and they were 0. The CT value wasn't working properly meaning subsequent steps were being calculated as 0. Problme solved. Thank you.

I'm trying to modify the subroutine so that the turbine can yaw, this I can acheive. However, when I try to resolve the drag force so that it can be determined for any direction, I have problems. I'm determining a yaw error, simple trigonometry, and when I include this yaw correction (trig function) in both FUDRAG and FVDRAG the loop starts returning my angle of attack as NaN and the U and V as zero. However, if I include this yaw correction in either FUDRAG or FVDRAG the whole subroutine works fine. Any suggestions?

Hello,

Beware the use of function ATAN:

AOA=ATAN(UN%R(I)/VN%R(I))

that may cause problems if VN%R(I)=0.D0, you can use instead :

AOA=ATAN2(UN%R(I),VN%R(I)) which will return PI/2 if VN%R(I)=0.D0.

Another thing, are you sure that such things as ABS(UN%R(I)) enter in your correction ? I am not sure that it gives a "tensorial" form that would be independant of a rotation of the mesh. I would expect things like SQRT(UN%R(I)**2+VN%R(I)) but this is just a remark as I do not know what is "yaw" and what you wish to do.

Regards,

Jean-Michel Hervouet

Thanks, its working now with the ATAN2.

Yaw is where a turbine (whether a wind or tidal turbine) rotates the direction of the rotor to be perpendicular to the direction of flow in order to maximise energy capture.

In my drag equations, the drag is split between the drag caused by the structure (ie a monopile) and the drag of the rotor. The drag of the structure is uniform in any direction but the maximum drag of the rotor is when the rotor is perpendicular to the flow. Therefore, when the turbine is positioned in a location when the flow is not nicely aligned with a U or V axis, my yaw function is resolving the drag of the rotor into U and V so it can be placed anywhere in a shelf model.

I was using the absolute function as the drag is a function of U^2 but if the flow is a -ve in the U axis, by squaring it would result in a positive answer. Hence what I was trying to do was |U|*U, which should do this.