A recent formula for the lift force on a low speed wing of circular arc cross-section [<span style="font-family:Verdana;"><span style="font-family:Verdana;"><b><span style=&quo...A recent formula for the lift force on a low speed wing of circular arc cross-section [<span style="font-family:Verdana;"><span style="font-family:Verdana;"><b><span style="font-family:Verdana;"><a href="#ref1">1</a></span></b></span></span><span><span></span></span><span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">] is adapted to the upward pressure force on the crests of a surface gravity wave propagating in the wind. In both cases</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> the main feature is the utilization of the air’s compressibility. At and near a wave crest</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> it is predicted that the air density is increased over the ambient value and that the air density decreases inversely as the square of the upward distance from the radius of curvature of the crest. As a consequence</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the air pressure also decreases upward inversely as the square of the same distance. Therefore, an upward pressure force on each crest occurs which presumably will make the crests grow. Growth rates are largest for small </span><span style="font-family:Verdana;">wavelengths and large mean slopes of the wave surface. Contrary winds should produce </span><span style="font-family:Verdana;">wave growth (not damping) as well as no wind at all.</span></span></span></span>展开更多
文摘A recent formula for the lift force on a low speed wing of circular arc cross-section [<span style="font-family:Verdana;"><span style="font-family:Verdana;"><b><span style="font-family:Verdana;"><a href="#ref1">1</a></span></b></span></span><span><span></span></span><span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">] is adapted to the upward pressure force on the crests of a surface gravity wave propagating in the wind. In both cases</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> the main feature is the utilization of the air’s compressibility. At and near a wave crest</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> it is predicted that the air density is increased over the ambient value and that the air density decreases inversely as the square of the upward distance from the radius of curvature of the crest. As a consequence</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">,</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the air pressure also decreases upward inversely as the square of the same distance. Therefore, an upward pressure force on each crest occurs which presumably will make the crests grow. Growth rates are largest for small </span><span style="font-family:Verdana;">wavelengths and large mean slopes of the wave surface. Contrary winds should produce </span><span style="font-family:Verdana;">wave growth (not damping) as well as no wind at all.</span></span></span></span>
