| Biography | |
|---|---|
 Prof. Jinjia Wei Xi’an Jiaotong University, China |
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| Title: Direct Numerical Simulation of Surfactant Drag Reducing Flow in Grooved Channel | |
| Abstract: The turbulent flow of surfactant solution in the smooth and wide-rib rectangular grooved channels was studied by the direct numerical simulation (DNS) method. Moreover, the variations of near-wall streamwise vortices with time were discussed and the distributions of streamwise vortex radius, swirling strength and density were quantitatively investigated by using the two-dimensional swirling-strength criterion. It was found that the difference of vortex radii for grooved channels mainly occur within the buffer layer, indicating that the influence of microgrooves on the fluid also mainly occurs within the buffer layer. The vortex density presents the peak value within the grooved valley for all grooved cases, indicating that microgrooves can induce numerous streamwise vortices with small size and swirling strength within the grooved valleys. The drag-reducing enhancement mechanism of microgroove in the surfactant solution could be mainly considered as the result competing between the “restriction effect” and the “tip effect” of microgroove, and the essential factor of the drag reduction by microgroove should be the numerous secondary streamwise vortices with small size and swirling strength within the grooved valleys, which are induced by microgrooves and can prevent the near-wall small vortices intruding into the grooved valleys. Furthermore, a predicted method for the optimal drag-reducing size of microgroove is proposed, and the prediction values about the optimal drag-reducing size of microgroove in the surfactant solution are  and  respectively, which agree well with the numerical results. | |
| Biography: Jin-Jia WEI is a professor of Xi’an Jiaotong University and the dean of School of Chemical Engineering and Technology. He is the council member of Chinese Society of Engineering Thermophysics and is also the editorial member of 5 international journals. He got degree of Dr. Eng. from Xi’an Jiaotogn University in 1998 and PhD from Kyushu University in 2002. His research interests include two-phase/drag-reducing flow and heat transfer, enhancement of boiling heat transfer for ground and space application, solar thermal utilization and solar voltaic/thermal hybrid utilization. He published more than 200 papers, gave more than 20 invited talks in international conferences, and got two first-grade ministerial or provincial level science and technology awards and an Excellent Young Scholar Award of WU Zhong-Hua Fund from Chinese Society of Engineering Thermophysics. He is the Cheung Kong scholar chair professor of Ministry of Education, the winner of national natural science fund for distinguished scholars, and also scientific and technological innovation leading talent of National Ten thousand plan. | |
