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Query on Aerodynamic Forces/Moments Directions
Dear all,
I’m trying to perform co-simulation between QBlade and other software whereby aerodynamic forces/moments from the rotor is transferred to another software, but I am unsure about the coordinate system that the aerodynamic forces/moments are reported in. My doubts are as follows:
- What is the reference coordinate system for “Aerodynamic Thrust” & “Aerodynamic Torque”?
- Is “Aerodynamic Force/Moment in Hub X_g/Y_g/Z_g Direction” reported with respect to the global axis?
My doubts arise when I try to perform simulation of 2 similar turbines in which the orientation of the turbine and the inflow wind is rotated by 180°. I was expecting that the “Aerodynamic Moment in Hub X_g Direction” would be reversed as the rotor is rotating in opposite direction with respect to global coordinate system. However, the simulations seem to be reporting the same Aerodynamic Moment. Simulation files are attached for reference.
Thanks in advance!
Regards,
Andhi
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Hi Andhi,
thats a typo in the variable name. It should be Aerodynamic Force/Moment in Hub X_h/Y_h/Z_h, which is the local fixed hub coordinate system. This system is attached to the turbine, so it rotates with it.
The variable name is fixed now…
Best regards,
David
Hello David,
Thank you very much for your response.
Does that mean that the hub local y & z axes also rotate together with the turbine about the local x-axis?
Could we possibly obtain the hub forces/moments about a stationary hub axes system that doesn’t rotate along the hub x-axis?
Thanks & regards,
Andhi
Hi Andi,
The fixed hub coordinate system does not rotate with the rotor.
It is attached to the turbine, meaning it translates and rotates with the turbine when the turbine’s position changes, but it remains unaffected by the rotor’s rotation.
For reference, here’s the documentation:
https://docs.qblade.org/src/user/coordinates/coordinates.html#local-sensor-coordinate-systems
Best regards,
David
Hello David,
Thank you for the information.
Could you further clarify how is “Aerodynamic Force in Hub Y_h Direction” different from “Y_h For. Hub Const.”?
Thanks & regards,
Andhi
Hi Andhi,
The variable “Aerodynamic Force in Hub Y_h Direction” is found in the aerodynamic time graph and shows the projection of aerodynamic forces along the fixed hub coordinate system.
The variable “Y_h For. Hub Const.” is found in the structural time graph and shows the total force (aerodynamic + inertia + elastic) measured at the hub constraint and projected into the fixed hub coordinate system.
Its possible that both sensors show the same or very similar values. The latter variable (Y_h For. Hub Const.) also is only available when a structural model is included.
Best regards,
David
Hi David,
If I understand you correctly, Aerodynamic forces only capture the forces due to moving currents on the MHK turbine and not other effects like inertia & blade elasticity effect.
I am attempting to co-simulate MHK turbine in QBlade with other hydrodynamic/mooring solver (OrcaFlex) using the SIL interface, and my goal is to transfer the turbine forces and moments to OrcaFlex which could not reliably simulate underwater turbine. Which of the two parameters would you recommend to be transferred over the SIL interface that could capture all the relevant effects on the rotating turbine (e.g. hydrodynamic, added mass, inertia, elastic)?
Also, could you confirm that the directions of hub local coordinate system remains fixed and does not rotate along with rotor (as suggested in the snapshots of GUI attached)?
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Hi Andhi,
The aerodynamic force output only accounts for the forces generated by aerodynamic lift, drag, and moment acting on the blades.
For cosimulation, I recommend building a QBlade model that represents only the structural and aero/hydro-dynamic components you wish QBlade to handle. Any components modeled outside QBlade should be excluded from this model.
The cosimulation framework then exchanges data in a staggered manner:
Positions are passed from Orcaflex to QBlade.
Forces and moments are passed from QBlade to Orcaflex.
To implement this, you can use the functions setTurbinePosition_at_num() and getTowerBottomLoads_at_num() from the SIL interface (see: QBlade documentation).
May I ask why you are planning to model parts of the system in Orcaflex instead of using QBlade for the entire setup? Are you perhaps missing certain functionalities or features in QBlade that are essential for your application, or is there another reason for splitting the model between the two tools?
Best regards,
David
Hello David,
Thank you for your quick response as always, and thanks for directing me to the SIL interface guide.
There are a few reasons why I am attempting this co-simulation, like complexity of the mooring system that I am researching on, as well as the format of the potential flow file that I have to work with (derived from OrcaWave).
Regards,
Andhi
