Experimental Investigation on Boundary Layer Flow Under the Effect of Temperature Gradient in a Smooth Rotating Channel Using Hot-Wire

Abstract

This experiment measures the temperature and the velocity field synchronously in the boundary layer in a rotating smooth, wall-heated channel using hot-wire. The Reynolds number based on the bulk mean velocity and hydraulic diameter is 19000 and the rotation numbers are 0, 0.07, 0.14, 0.21, 0.28 and 0.35. Four streamwise stations (X/D = 4.06, 5.31, 6.56, 7.81) were investigated. To calibrate the parallel-array hot-wire probe, a heating section is added to the original wind tunnel that could only calibrate the hot-wire at room temperature. Different gas temperatures at the outlet could be obtained by changing the heating power of the heating section. The velocity profiles and the temperature profiles are obtained. It can be seen that the viscous sublayer also exists when the wall is heated, thus the viscous sublayer profile method is also valid when the wall is heated. It is found that the velocity profile near the leading side is more sensitive to the change of rotation number and X/D than the velocity profile near the trailing edge. The critical rotation number phenomenon of velocity profile has also been found in present work. By comparing with the previous work without the wall heated, the influence of both kinds of buoyancy under this condition is discussed. Some explanations are given for the experimental results.

Experimental Investigation on Velocity and Temperature Field in a Rotating Non-isothermal Turbulent Boundary Layer using Hot-wire

“…The largest difference can reach 14.6%. This is similar to the critical rotation number phenomenon of the leading side velocity profiles in our previous study 19 . The influence of Coriolis force at the downstream will be weakened under certain circumstances.…”

“…However, its measurement of temperature is affected by changes in velocity, which makes it different from conventional temperature sensitive resistance. In our previous article 19 , the arrangement of the probe has been introduced in details as shown in Fig. 4b.…”

“…For parallel-array hot-wire probe, the first thing to verify is the influence between the two hot-wire probes. This part of the verification process has been detailed in our previous article 19 . It suggests that the impact of the two hot-wire probes is acceptable and the apparatus has high spatial resolution in the measurement process.…”

A review of the research progress of boundary layer theory

“…根据边界 层速度分布的测量结果, 提出了新的科氏力入侵边界 层深度极限的判断方法. Li等人 [146] 利用热线同步测量 了旋转直通道加热壁面边界层内的温度场和速度场, 发现吸力面的速度分布比压力面的速度分布对旋转数 和流向位置的变化更为敏感. 此外还发现了速度剖面 的临界转数现象, 通过与未加热壁面情况的比较, 讨 论了壁面加热情况下浮升力的影响.…”