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本文论述了,砼表面自然颗粒糙度上产生空穴的条件,当正确的选择特征流速和特征压力值后,在光滑表面上的孤立状骨料的临界空穴数,仅取决于填充料的形状。当孤立骨料位于与其类似的填充料中间时,即在实际糙度条件下。周围填充料对所论骨料的影响有两种方式。首先由于边界层的发展,在行进段流速分布图剧烈变化。由此,在所论凸起坎上的接触流速减小。其次,该骨料落到骨料前方的附生水束中,由此进一步增强了所论凸坎上接触流速减小和行进水流紊动性的增大。上面所说的那些影响被称之为遮盖作用τ来估计。文中介绍了简单关系式,用其可完成在不同的水力条件下,确定在不同形状,尺寸的自然颗粒糙度上的初生空穴的工程计算。
In this paper, the conditions of cavitation on the natural particle surface roughness of concrete are discussed. The critical cavitation number of the isolated aggregate on a smooth surface is only determined by the choice of characteristic flow rate and characteristic pressure value shape. When the isolated aggregate is located in the middle of a similar filler, that is, under actual roughness conditions. There are two ways in which the surrounding filler affects the aggregate in question. First of all, due to the development of the boundary layer, the distribution of velocity profile in the moving section changes drastically. As a result, the contact flow rate at the raised ridge is reduced. Second, the aggregates fall into the epiphytic bundles in front of the aggregates, thereby further enhancing the reduction of the contact velocity on the tabs and the increase of turbulence of the traveling water flow. The effects mentioned above are termed the cloaking τ. In this paper, a simple relational formula is introduced, which can be used to determine the engineering calculation of primary cavities on the natural particle roughness of different shapes and sizes under different hydraulic conditions.