Velocity measurements close to a rough plate oscillating in its own plane
Velocity measurements close to a rough plate oscillating in its own plane
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接近在其自身平面内振荡的粗糙板的速度测量
DOI：
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发表时间：
1976
影响因子：
3.7
通讯作者：
J. Sleath
中科院分区：
文献类型：
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作者：
D. Keiller;J. Sleath
测量描述的流体速度接近粗糙床振荡在自己的平面。获得的大多数结果的粗糙度由紧密堆积在六边形结构中的光滑球体组成。对于砾石层也给出了一些结果。床在静止空气中以简谐运动振荡，并且用热线风速计进行测量。非常接近光滑球体床的测量结果显示，在每个半周期内，速度分布有两个最大值。一个最大值对应于随时间近似正弦变化的速度分量。第二个形成了一个相当尖锐的峰值，并发生在ωt = 90°，270°附近，其中ω是振荡的角频率，t是从板的最大速度的瞬间测量的时间。该峰值出现的相位随离床的距离变化很小。对于βD > 3·0的值，其中β =（ω/2ν）1/2，ν是运动粘度，D是球体直径，在每个半周期期间，在离床的至少一定距离范围内的该峰值处发现最大速度。近似正弦的速度分量随高度的变化与Stokes（1851）给出的平板解十分接近。然而，在ωt = 90°，270°处的峰值从床处的零开始上升，在距波峰约八分之一球径处达到最大值，然后福尔斯再次下降。对砾石层的测量表明，速度的变化与Kalkanis（1957，1964）和Sleath（1970）观察到的相似。由于表面的不规则性，很难对床面附近的水流得出明确的结论。为了确定速度积uw，用一根与球床成45°倾斜的金属丝对球床进行了许多试验。
Measurements are described of the fluid velocities close to rough beds oscillating in their own plane. The roughness with which most of the results were obtained consisted of smooth spheres closely packed in hexagonal formation. Some results are also given for beds of gravel. The beds were oscillated with simple harmonic motion in still air and the measurements were made with a hot-wire anemometer. The measurements very close to the beds of smooth spheres show two maxima in the velocity profile during each half-cycle. One maximum corresponds to a component of velocity which varies nearly sinusoidally with time. The second forms quite a sharp peak and occurs close to ωt = 90°, 270°, where ω is the angular frequency of oscillation and t is time measured from the instant of maximum velocity of the plate. The phase at which this peak occurs shows little variation with distance from the bed. For values of βD > 3·0, where β = (ω/2ν)½, ν is the kinematic viscosity and D is the sphere diameter, the maximum velocity during each half-cycle is found at this peak over at least a certain range of distances from the bed. The variation with height of the nearly sinusoidal component of velocity is quite close to that given by Stokes’ (1851) solution for a flat plate. The peak at ωt = 90°, 270°, however, rises from zero at the bed to a maximum at a distance of about one-eighth of a sphere diameter above the crests and then falls off again. The measurements with beds of gravel show a variation in velocity similar to that observed by Kalkanis (1957, 1964) and Sleath (1970). Because of the irregularity of the surface it is difficult to draw definite conclusions about the flow in the immediate vicinity of the bed. A number of tests were carried out, with the beds of spheres, using a wire slanted at 45° to the bed in order to determine the velocity product uw.