Ruquan You

Two-dimensional heat transfer distribution in a rotating smooth rectangular channel with four surface heating boundary condition:

In this study, two-dimensional heat transfer distribution on the leading surface and trailing surface in a rotating smooth channel with typical boundary condition of four surface heating was investigated experimentally for the first time. The Reynolds number, based on channel hydraulic diameter (80 mm) and the bulk mean velocity, ranges from 15,000 to 30,000, and the highest rotation number is 0.359 with the Reynolds number of 15,000. The mean density ratio is about 0.11 in this work. The obtained result showed that rotation has an important effect on the heat transfer distribution along the span-wise direction. On the leading side, rotation-induced secondary flow makes the Nu/Nu0 at the edge area of the wall surface (Z/D = 0 and Z/D = 1) is higher than that on the middle area (Z/D = 0.5). On the trailing surface, the trend of Nu/Nu0 ratio along the span-wise direction is reversed. Along the stream-wise direction, the Nu/Nus ratio increases with the rotation number monotonously on the trailing side. However, on the leading side, with the increase in rotation number, the Nu/Nus does not decrease monotonously along the stream-wise direction, there is a slight enhancement along the stream-wise direction. The secondary flow induced by rotation enhances Nu ¯ / N u s ratio up to 1.35 on the trailing side and weakens the Nu ¯ / N u s ratio close to 0.75 on the leading side with the Re = 15,000, and Ro = 0.359. More details of two-dimensional distribution of temperature and Nu on the leading and trailing side are shown in this work.

Interaction of Secondary Flow With Developing, Turbulent Boundary Layers in a Rotating Duct

Investigations of the interaction of secondary flow with developing, turbulent boundary layer in a rotating square-section straight channel have been done in a new rotating facility with normal hot wire anemometry. The measurements are performed with Re=18391 and Ro=0, 0.116, 0.232, respectively, characterized by the channel hydraulic diameter of 80 mm and the bulk mean velocity. Measurements at five stations distributed in the streamwise direction have been done to study the turbulent boundary layer streamwise development. The mean velocity profiles in both ordinary and semi-logarithm coordinates and skin shear velocities at these test stations are obtained. On the leading side, the skin shear velocity firstly decreases, and then increases in the streamwise direction. This phenomenon is analogous to the critical rotation number phenomenon revealed in previous work with heat transfer. Based on this analogy, a new possible explanation of the critical rotation number phenomenon is given here. The semi-logarithm mean velocity profile is found to not obey the traditional log-law linear rotation correction. This suggested the need of a secondary flow strength correction of the log law with system rotation.Copyright