Liu H, Winoto S H, Shah D A
Department of Mechanical and Production Engineering, National University of Singapore, Republic of Singapore.
Ann Biomed Eng. 1997 Nov-Dec;25(6):939-48.
An expression for centerline mean velocity distributions for circular and noncircular confined turbulent jets has been obtained by assuming self-preservation of flow downstream of the jet potential core. It was assumed that the velocity decay was not only dependent on the streamwise distance x in terms of x/d, as in the case of free jets, but also on the ratio of the orifice diameter d to the confining pipe diameter D. To validate the expression and to determine the empirical constants, measurements of the centerline velocities within the confined jets issuing from different size circular orifices and various noncircular orifices of different shapes were conducted. The results indicate that the validity of the expression is restricted to d/D < or =0.25 and is weakly dependent on the particular orifice shape. It is suggested that, as for the case of free turbulent jets reported earlier, that this expression may be used potentially to predict the valvular lesion size or to estimate the volume of valvular regurgitation for confined jets provided the value of D, which corresponds to the "atrial diameter," is known or statistically available.
通过假设射流势核下游流动的自相似性，得出了圆形和非圆形受限湍流射流中心线平均速度分布的表达式。假设速度衰减不仅像自由射流那样，取决于以x/d表示的沿程距离x，还取决于孔口直径d与限制管道直径D的比值。为了验证该表达式并确定经验常数，对从不同尺寸圆形孔口和各种不同形状非圆形孔口喷出的受限射流内的中心线速度进行了测量。结果表明，该表达式的有效性仅限于d/D≤0.25，并且对特定孔口形状的依赖性较弱。建议与之前报道的自由湍流射流情况一样，只要知道或通过统计得到对应于“心房直径”的D值，该表达式可能潜在地用于预测瓣膜病变大小或估计受限射流的瓣膜反流体积。
