Evaluation of Integral Length Scales in Wind Tunnel Simulation and Field Study

Abstract eng:
In this paper, a brief description of the measurement in wind tunnel and the Wind Engineering Research Field Laboratory (WERFL) at Texas Tech University is presented, followed by analytical procedures used to estimate integral scales. The scales of the u, v, and w velocity components for separation in the x, y and z directions are described. These scales were obtained using three techniques: direct integration, exponential fit and spectral fit. In most cases, the scales displayed a strong dependence on the technique used. Generally exponential fit gives more consistent results than direct integration, which is seriously affected by non-stationarities of the turbulence. Spectral fit sometimes suffers from the difficulties of fitting the von Karman model curve to the measured spectrum by eye. Considerable run to run variability of scales is observed for all three techniques. It also can be concluded that the scales are strongly influenced by the specific features of upstream terrain. Generally the scales increase with increasing height up to the gradient height. Averaged values of integral length scale were in reasonable agreement with similar available atmospheric observations and with most of the predictions of the ESDU model. Results of this study can be used to enrich our understanding of wind flow characteristics as well as to assist in the wind tunnel simulation.

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