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Boeing Mod-2



Dr. (Peter) H.-T. Liu
StereoVision Engineering

Fig. 1 Boeing 2.5MW MOD 2 wind turbine at Goodnoe Hill Test Site.

Fig. 2 Three stages of vortex instability (looking downwind): forward, reversing, and reversed spouts.

Fig. 3 Time lapsed photographs of reversed spout.

A full-scale wind turbine test site at Goodnoe Hill near Goldendale, Washington was established in 1979 by the Department of Energy to understand the performance of large wind turbines in a full-scale environment. The site consisted of a cluster of 3 2.5 MW Boeing MOD-2 wind turbines with a 94-m rotor diameter and a 61-m tall tower (Fig. 1). Flow-visualization experiments were conducted to investigate

several wake phenomena [1, 2]. In one of the experiments, smoke was released downstream of the rotating blade tips from a tethered generator to visualize the evolution of the rotor-tip vortices.

The smoke generator released a large volume of smoke continuously for several minutes. When the rotor blades cut in front of the smoke trail, a section of the helical vortex generated locally became visible as smoke was entrained and trapped in the low-pressure core. The vortex became unstable when it passed through the wake of the turbine tower. The vortex reversed its course forming a long "spout" shooting at high speeds away from the turbine wake (Figs. 2 and 3). As the vortex swept across the relatively narrow tower wake,

it experienced a sudden increase and then decreased in the ambient pressure. It is believed that the vortex reversal, a form of instability, is triggered by the above vortex-wake interaction.

[1] Liu, H.-T., Hiester, T. R., Waite, J. W., Tacheron, P. H., and Srnsky, R. A. (1983) "Flow Visualization Study of a MOD-2 Turbine Wake," Pacific Northwest Laboratory Technical Report PNL-4535, UC-60, June.

[2] Hiester, T. R., Liu, H.-T., and Waite, J. W. (1983) "Results of MOD-2 Wake Flow Visualization," presented at 1983 American Solar Energy Society Meeting, June 1-3.

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