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petebachant / CFT-Re-dep-paper

Source files for a journal article analyzing Reynolds number effects on the performance and near-wake of a vertical-axis cross-flow turbine, to be published in Energies.
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Relate foil performance to turbine performance #13

Closed petebachant closed 9 years ago

petebachant commented 9 years ago

Basically L/D ratio for a blade. Make an updated version of the old diagram I used during my MS for turbine loading with high and low L/D.

petebachant commented 9 years ago

Plot angle of attack and relative velocity squared for the upwind half of the rotation to show what the ideal Cl/Cd curve would look like. Maybe the integral weighted based on the PDF of AoA and relative velocity squared.

petebachant commented 9 years ago

Really we should be looking at tangential force coefficients. I did a simulation with XFOIL for a NACA 0020 and 4520 foil--the 4 percent camber at half-chord added to try to mimic the flow curvature.

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petebachant commented 9 years ago

Calculated max 2-D turbine torque coefficient from geometric considerations only (no induction) and XFOIL static data. I think this is a good way to predict Reynolds number dependence.

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petebachant commented 9 years ago

Note how the camber does push the Reynolds number dependence down as you had mentioned before, @wosnik, which explains why the Re-dependence is weaker for the RVAT compared to the RM2--a little preview for the next paper on that.

petebachant commented 9 years ago

These results also suggest the use of an outward (opposite blade path) camber foil to improve performance, similar to the UGE design.

wosnik commented 9 years ago

This also explains the differences we are seeing between the UNH-RVAT and the RM2.