I am working on a small scale SB-VAWT and I am validating with a pre-published experimental data. All the results were satisfying and the overestimation between the numerical and the experimental results was very acceptable and the power coefficient curves were also quite good except for the aerodynamic forces at the maximum local power coefficient.
The main problem was that when the aerofoil reaches the upwind position (nearly 90 azimuthal degrees) where the maximum local power coefficient occurs, the blade encounters the highest Drag coefficient with a relatively low lift coefficient although the SB-VAWT is a lift based turbine.
Is this due to a misleading choice in the computational method whether mesh or physics which lead to inaccuracy in results or is it due to a further physical phenomenon?
I am using the SST K-omega model with a transient pressure based segregated, the COUPLE algorithm for the pressure-velocity coupling and 2nd-order discretization. Y+ check was made during the simulation to assure it is < 2.
I have done a rough mesh independence test with results:
(Number of elements - Cm)
1st: 19000 - 0.15
2nd: 38000 - 0.13
3rd: 102000 - 0.126
and I settled on the 2nd case.
DEAR DOCTOR
Please see the following paper:
Article Experimental and theoretical investigation of the effect of ...
There could be many reasons why you are getting the results, including problems with the CFD code itself.
Did you write the code yourself?
Does your problem occur at all tipspeed ratios (TSR)?
At moderate to high tipspeed ratios, say TSR > 3, the blade might be passing through the wake it shed on the previous rotation, or through the wakes of other blades.
Looking from above a turbine, at TSR = 1, the vortex sheet shed from the trailing edge of a blade (in potential flow) looks like a sequence of repeating cycloids.
For TSR > 1, small "loops" appear at the cusps of the cycloidal vortex sheet, and they travel downwind quite easily and quickly.
For larger TSR, those "loops" begin to roll up, and don't travel downwind very quickly.
At even higher TSR the sheet can become trapped inside the circular blade trajectory.
A blade travelling through that messy flow is not likely to be developing lift very efficiently.
Vorticity contours are shown in Fig. 17 of this paper which used Fluent.
https://www.researchgate.net/profile/Haris_Mian/publication/256463304_A_detailed_Aerodynamic_Design_and_analysis_of_a_2D_vertical_axis_wind_turbine_using_sliding_mesh_in_CFD/links/53e5a3ba0cf25d674e9c29a2.pdf
Good luck with your research!
Conference Paper A detailed Aerodynamic Design and analysis of a 2D vertical ...
Following the answer given by dear Leo Lazauskas,
You can also check this paper:
Article A Numerical Study on the Aerodynamic Performance and the Sel...
DEAR DOCTOR
Please see the following paper:
Article Experimental and theoretical investigation of the effect of ...
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