Volume 55

Flow Structure and Heat Transfer in a Channel With the Streamwise Ribs Arranged in the Buffer Layer Jiarui Gong, Jiansheng Wang, Xueling Liu, Jintao Niu, Xuqing Wang

Abstract

In the present study, the streamwise ribs are arranged in the buffer layer without destroying the viscous sublayer of the turbulent boundary layer in the rectangular channel, which aim to achieve the drag reduction and maintain the heat transfer performance simultaneously. The numerical calculation is carried out at Re = 3745, 4745, and 5745. The ribs induce plenty of small-scale secondary vortices in the viscous sublayer and the buffer layer. These vortices can suppress the sweep motions of the high-speed fluid carried by large-scale vortices. The friction loss on the bottom of the channel significantly decreases and the drag reduction efficiency can be up to 26.282% at Re = 5745. Meanwhile, the sweeping motion of the fluid between the adjacent ribs destroys the temperature boundary layer and the heat transfer performance is intensified. The excess heat transfer can compensate the local heat loss below the ribs so that the heat transfer performance maintains at the original level at Re =3745. The Nusselt number on the bottom even increases at higher Re. The maximum comprehensive performance coefficient is up to 1.112.

Keywords Heat transfer, flow control, turbulent flow, drag reduction, streamwise rib