Vertical coherence and phase delay between wind components in strong winds below 20 m

Abstract

Vertical coherence and phase delay between wind components in strong winds in the lowest 20 m over uniform terrain in New Zealand have been analysed. The vertical decay constants and slopes for the horizontal wind components could be described as linear functions of the ratio of vertical spacing to mean height (AZ/~), with relatively little scatter. The decay constants for the lateral were smaller than for the lon~tudinal components, the slopes larger for the lateral components, as found previously.The coherence of vertical velocity is best described by exponential decay functions multiplied by a parameter which decreases linearly from 1 (for AZ/Z = 0) to 0.5 (for AZ/Z = 1). The decay constants increased linearly with AZ/Z, as in the case of the horizontal components. There were no significant phase differences for the vertical components.Lateral and vertical decay constants for the longitudinal wind component could be fitted to identical functions of Ay/z and AZ/Z, respectively.

Measurements of Surface-Layer Turbulence in a Wide Norwegian Fjord Using Synchronized Long-Range Doppler Wind Lidars

“…The function is an idealized representation of the lateral coherence of the along-wind turbulence near the ground. Bowen et al [55] arrive, for example, at b 1 = 12 and b 2 = 11. In the present case, b 1 and b 2 are determined using a least-square fit to the measured co-coherence.…”

“…The more complex dependency of the measured co-coherence on the lateral separation may be modelled using Bowen's coherence model [55], which is derived from the Davenport coherence model, except that the decay parameter C y u has the following form:…”

“…The low dependency of the estimated co-coherence on d y at large crosswind separations is reflected in the negative value of b 2 that counterbalances b 1 , as shown in the right panel of Figure 16. Figure 13, except that the solid and dashed lines correspond to the coherence model derived from Bowen et al [55].…”

A Study on the Turbulence Length Scales in von Karman Model by Using Offshore Wind Field Measurement

“…, Panofsky et al (1974) 16) , Kanda and Royles (1978) 17) , Shiotani and Iwatani(1979) 18) , Bowen et al (1983) 19) 等によって無次元化パラメータであるディケ イファクターが評価されている。一方，カルマンモデ ルのコヒーレンスモデルによる結果を示した例として Duchene-Marullaz (1977) 20) および前田ら(1981) 21) …”

Numerical investigation of the aerodynamic characteristics of a flat plate in an oscillating freestream.

“…Also discussed is the possibility that the numerical simulations are and by the surface frictional effect (Watkins et al 2006). Long term studies of the an Australian city at a height of 10 meters suggests the average wind speed is approximately 4 m/s (Bowen et al, 1983). Environments with terrain roughness between 4 (areas such as villages, suburban terrain or permanent forests) and 7 (an area with at least 15% of the area covered by objects with an average height exceeding 15m) have a general turbulence range between 15% and 35% of the mean flow speed and spectra ranges between 0.25 and 2.5 Hz (Watkins et al, 2003) with the peaks in turbulence occurring around a gust frequency of 1 Hz.…”