numerical*/*experimental*comparison* of*ascaled*model...
TRANSCRIPT
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Numerical / Experimental Comparison of a Scaled Model Horizontal Axis Marine Hydrokine=c (MHK) Turbine
Teymour Javaherchi, Nick Stelzenmuller
Joseph Seydel and Alberto Aliseda
Northwest Na=onal Marine Renewable Energy Center University of Washington
APS -‐ DFD -‐ PiPsburg Nov/24/2013
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Mo#va#ons & Goals
Need for an experimental database to benchmark numerical methodologies to model MHK turbines.
Understand the trade offs in numerical models to simulate the flow field of MHK turbines.
Develop a validated numerical methodology to support design of full-‐scale horizontal axis MHK turbines.
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Numerical Methodology
1. Sliding Mesh Model
2. Rota#ng Reference Model
3. Blade Element Theory
4. Actuator Disk Theory
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Rota#ng Reference Frame Model Computa#onal Domain (Zoomed-‐in)
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Numerical vs. Experimental Results Efficiency (Cp) – Tip Speed Ra#o (TSR) Curves
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Limited Streamlines + Wall Shear Stress along the Blade
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Limited Streamlines + Wall Shear Stress along the Blade
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Numerical vs. Experimental Results Efficiency (Cp) – Tip Speed Ra#o (TSR) Curves
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Dynamic Fluctua#ons in Experiment at Low TSRs
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Numerical vs. Experimental Results Efficiency (Cp) – Tip Speed Ra#o (TSR) Curves
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Numerical vs. Experimental Results Reynolds Number Effect
Experimental Numerical
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Numerical Results – Velocity Field (TSR=7.16 , Re=100,000)
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Numerical vs. Experimental Results Velocity Deficit Profiles
Experimental Numerical
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Numerical vs. Experimental Results Velocity Deficit Profiles
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Numerical vs. Experimental Results Sliding Mesh Model – TSR=8.17
Efficiency [-‐]
Experiment 0.38
Sliding Mesh Model 0.38
Rotating Reference Model
0.37
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Summary & Conclusions
3D RANS numerical models are validated to characterize the performance of a scaled model MHK turbine.
The error between the measured and predicted power values was between 1% to 25%.
3D RANS predicted beder results in flow fields with high Reynolds number and not exis#ng or small flow separa#on.
Experiment shows that the wake of nacelle enhances velocity deficit recovery, but the current 3D RANS model is limited to capture this physical phenomenon.
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The idea is to render an unsteady problem in the fixed ref. frame into a steady problem in the rotating ref. frame.
RANS equa#ons are solved in the rota#ng reference frame.
Single Rota#ng Reference (SRF)
Sta=onary Rota=ng with the angular velocity “ω”
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Pressure Outlet
Velocity Inlet (flow direction)
Planes of Symmetry
Slip free surfaces
Blade wall (no slip)
Computa#onal Domain
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Lig/Drag Coefficients and AOA along the Blade Span (TSR=7.16)
* 3D CFD RANS O BEM Theory