论文部分内容阅读
描述了棒束子通道内流速分布,壁面剪应力分布和湍流雷诺应力张量分布的实验研究。由四根棒组成的棒束平行对称地布置在一个矩形流道内。试验棒的中心距与棒直径之比为:P/D=1.148,而壁距与棒直径之比分别为W_1/D=1.045和W_2/D=1.074。两种不同几何条件下,实验中雷诺数分别为6.11×10~4和7.0×10~4。实验结果表明,棒束子通道内的湍流结构与圆管内的湍流结构有很大差别。特别是在棒和通道壁之间的窄缝区存在着相当强的轴向和周向湍流强度,因而那里也有相当强的湍流动能,这显然是由于通过棒-壁窄缝处强烈的湍流脉动流所造成的。和过去进行的非对称布置的子通道实验(子通道内有相同几何参数P/D及W/D,但与相邻子通道几何非对称地布置于同一矩形通道内)相比,发现对称子通道情况下子通道之间通过棒-棒窄缝处的湍流动量迁移例很小,可以忽略不计。壁面剪应力分布的实验值和用VELASCO程序计算结果相对比,发现两者之间有明显的差异,尤其是在棒—壁窄缝区,差异更大。建议有必要发展比现有程序更为完善的分析计算程序,以便提高对棒束子通道湍流流动的计算精度。
The experimental study on velocity distribution, wall shear stress distribution and turbulence Reynolds stress distribution in the bundle channel is described. A bundle of four rods is arranged symmetrically in a rectangular flow path. The ratio of center distance to rod diameter was P / D = 1.148, and the ratio of wall distance to rod diameter was W_1 / D = 1.045 and W_2 / D = 1.074, respectively. Under two different geometric conditions, the Reynolds numbers were 6.11 × 10 ~ 4 and 7.0 × 10 ~ 4 respectively. The experimental results show that the turbulent structure in the bundle channel is quite different from the turbulent structure in the tube. In particular, there is considerable strong axial and circumferential turbulence intensity at the narrowed zone between the rod and the passage wall, so that there is also considerable turbulent kinetic energy there, apparently due to the intense turbulent pulsation through the rod-wall slit Caused by the flow Compared with the asymmetric arrangement of subchannel experiments (the same geometric parameters P / D and W / D in the subchannels, but the geometric arrangement of the adjacent subchannels in the same rectangular channel) In the case of channels, there is very small, negligible, example of turbulent momentum transfer between the subchannels through the rod-bar slit. The experimental results of wall shear stress distribution are compared with those calculated by VELASCO program. There are obvious differences between the two, especially in the rod-wall narrow gap. It is suggested that it is necessary to develop a more complete analysis and calculation program than the existing one in order to improve the calculation accuracy of the turbulent flow in the bundle channel.