DNS study on the development of boundary layer with heat transfer under the effects of external and internal disturbances

Abstract

The effects of external and internal disturbances on the development of boundary layer with heat transfer are investigated by means of direct numerical simulation (DNS) based on the finite difference scheme. The fractional step method is used to solve the governing equations. The external disturbance is generated by a regular turbulence-generating grid, while the internal disturbance is generated by a tripping object mounted on the wall. In order to clarify the momentum and heat transfer mechanism in a boundary layer under these effects, the instantaneous and statistical characteristics of velocity and temperature fields are presented and discussed along with their interactions. The results show that the boundary layer in the case with grid turbulence becomes turbulent even though the Reynolds number based on the momentum thickness is low. On the other hand, in the case with the tripping object, only low-amplitude fluctuations are generated in the vicinity of the tripping object and the boundary layer does not fully developed. The grid increases the skin friction and enhances heat transfer more significantly than the tripping object. It is also found that strong strain in the viscous sublayer, which is induced by the vortical motion in the buffer layer, contributes to the enhancement of heat transfer.

Response of the temporal turbulent boundary layer to decaying free-stream turbulence

“…Previous numerical investigations have generally made use of either large-eddy simulation (e.g. Li, Schlatter & Henningson 2010;Péneau, Boisson & Djilali 2000) or DNS with modest Reynolds numbers (the study of Xia et al (2014) achieved a final momentum thickness Reynolds number Re θ ≈ 250). Yet there have been many studies considering the transition of an incoming laminar boundary layer under FST (Brandt, Schlatter & Henningson 2004;Hack & Zaki 2014;Kreilos et al 2016).…”

Numerical study on a boundary layer with heat transfer affected by a wake of a square bar

“…There are many studies on a boundary layer with heat transfer under such influence (e.g., Moffat, 1992a, 1992b;Péneau, et al, 2000;Kondjoyan, et al, 2002;Li, et al, 2010;Nagata, et al, 2011). Our previous research has also focused on this subject (Xia, et al, 2014). It has been clarified that heat transfer in the boundary layer becomes more active with increasing turbulence intensity in a free-stream.…”