Richard J.A.M. Stevens

Physics of Fluids · University of Twente

Publication 79 · Atmospheric turbulence

Effect of low-level jet on turbine aerodynamic blade loading using large-eddy simulations

S.N. Gadde, L. Liu, R.J.A.M. Stevens, J. Phys. Conf. Ser. 1934, 012001 (2021).

Main finding

The study asks how LLJ position affects near-wake vortices and external aerodynamic blade forces for one NREL 5-MW turbine. Wall-modelled Boussinesq LES uses AMD, concurrent precursor inflow, and an actuator-line representation previously compared with wind-tunnel data. Two moderately stable boundary layers use G=9 m s^-1, f=1.159e-4 s^-1, roughness lengths 0.002/0.0002 m, and cooling rates 0.25 and 0.50 K h^-1.

Near-wake vortex structures and velocity fluctuations for low-level jets above, at, and below hub height
How to read the figure. Near-wake vorticity behind a single turbine under a stable-boundary-layer low-level jet placed above, across, and below the rotor, with the streamwise velocity standard deviation for the same three cases. Tip and root vortices break down almost immediately when the jet sits above the rotor, at about two diameters when it is centred on it, and stay coherent to roughly five diameters when it sits below. The jet-above case also carries the largest near-wake turbulence. Open the full-resolution figure. Figure 2. S.N. Gadde et al. (2021). No separate licence is stated here; consult the original publication and credited source before reuse.

Why this matters

It clearly shows that where a blade crosses a jet matters.

Research context

Low ambient turbulence above the jet preserves coherent near-wake vortices, while vertical velocity shear produces azimuthal force variation. The study computes external aerodynamic forces, not structural stress histories or lifetime fatigue damage.

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