Direct numerical simulation of spanwise rotating turbulent channel flow with heat transfer

Abstract

SUMMARYDirect numerical simulation of spanwise rotating turbulent channel flow with heat transfer has been performed. The objective of this study is to reveal the effect of system rotation on the characteristics of turbulent flow, heat transfer, and large-scale motions in rotating turbulence. The Reynolds number is 194, the Prandtl number is 0.71, and the rotation number varies from 0 to 7.5, based on the global friction velocity, the channel half-height, and the angular speed of the spanwise rotating channel. To elucidate the effect of rotation on turbulent flow and heat transfer behaviours, some typical statistical quantities, including the mean velocity, temperature and their fluctuations, turbulent heat fluxes, and the structures of the velocity and temperature fluctuations, are analysed. The budget terms in the transport equation of turbulent heat flux are examined to deal with the effect of Coriolis force on turbulent heat transfer. Since rotational-induced Taylor-Görtler-like large-scale counter-rotating streamwise vortices (i.e. the roll cells) occur, the decomposition of the instantaneous temperature variance and turbulent heat flux is used to reveal the role of the rotational-induced structures on the thermal statistics.

Turbulent open channel flow with heat transfer subjected to the control of a spanwise travelling wave

“…[11] in our detailed test simulations [32]. Moreover, the present computational code has been verified extensively in our previous work [23][24][25][26][27]. the turbulence statistics.…”

“…Some previous work [17][18][19][20][21][22][23] indicated that the heat transfer efficiency of the turbulent open channel flow is primarily controlled by the turbulent motions very close to the wall or the free surface. In the free surface region, the flow behaviours are characterized by the surface renewal patches and the hot spots, and the generation of such turbulence structures is mainly dominated by the near-wall turbulent motions [24][25][26][27][28][29]. Based on these findings, the flow control by use of a spanwise travelling wave is thus expected to have considerable influence on the dynamics of turbulent heat transfer in the open channel flow.…”

“…The grid is uniform along the streamwise and spanwise directions. In the vertical direction, to increase the grid resolution near the free surface and the wall, the mesh is stretched with a transformation used in [23,25], so that the minimum vertical grid sizes about Dz þ min ¼ 0:1, 0.06 and 0.03 are used for Pr = 1, 10 and 100, respectively. According to Bergant and Tiselj [31], the grid system used is ensured to be capable of resolving all the essential scales of turbulence, with the smallest resolved temperature scales equal to the smallest scales of the velocity field for high-Pr calculations.…”

“…5 to examine the turbulence behaviour in response to the spanwise travelling wave. Due to the fact that the wall shear process of main flow is mainly responsible for the production of the streamwise turbulence fluctuation [24][25][26]33], the trend of the streamwise turbulence intensity (i.e., hu rms i) should be consistent with that of the shear stress in the wall region. As expected, Fig.…”

On the weak-equilibrium condition for derivation of algebraic heat flux model

“…It is true that the system rotation and streamline curvature can significantly influence the transport process in turbulent flows. This can be observed from numerous computations and experimental studies, such as Kasagi (2004), Liu and Lu (2007). Consequently, a question arises whether the usual assumption for diffusive-transport can hold in flows involving rotation and curvature effects.…”