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Wind profiles over hills (in relation to wind‐power utilization)
Author(s) -
Frenkiel J.
Publication year - 1962
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49708837606
Subject(s) - wind gradient , wind speed , wind direction , wind profile power law , temperature gradient , ridge , thermal wind , geology , wind shear , prevailing winds , maximum sustained wind , meteorology , stratification (seeds) , potential temperature , wind power , atmospheric sciences , environmental science , geography , seed dormancy , paleontology , botany , germination , electrical engineering , engineering , dormancy , biology
Following a previous country‐wide wind survey, two sites – each typical of one of the following two topographical categories: (a) a hill forming a part of a mountain ridge athwart the prevailing wind direction with steep leeward slopes, and (b) an isolated peak in a valley in the general direction of prevailing winds – were chosen for detailed investigation of wind behaviour with the purpose of correlating the characteristics of the wind flow over the hill to its topography. At each site, wind vertical gradient, wind direction, and temperature vertical gradient were measured in the height interval of interest to wind‐power utilization (10 m to 40 m above the hilltop) for a period of about a year. These measurements have shown: 1. There is no close relationship between mean wind profile and mean temperature profile over hills. 2. Whilst the directional wind profiles are practically uninfluenced by wind speed, they are largely determined by: (a) the hill profile in the immediate neighbourhood of the site of measurements, and (b) the hill profile further upwind in relation to that near the measurements site. 3. The effect of thermal stratification is important for all wind speeds with the curves of wind ratio as a function of temperature gradient exhibiting a both minimum and a maximum, the location of which on the scale of temperature gradient depending on the hill profile.A classification of wind‐power sites is given based on a single criterion, i.e., mean wind vertical gradient for the height interval from 10 m to 40 m. For optimal conditions for wind‐power utilization this gradient must vanish, a flow condition resulting from: (a) small hilltop area; (b) regular and smooth slopes of about 1 in 3 1/2 in the nearest few hundred metres from the hilltop.