Download Effect of parameters of traveling wave-like blowing and

10th International Symposium on Turbulence and Shear Flow Phenomena (TSFP10), Chicago, USA, July, 2017
Effect of parameters of traveling wave-like blowing and suction on
skin-friction drag reduction and heat transfer enhancement in turbulent
channel flow
Hiroya Mamori1∗ , Naoya Fukushima1 , Makoto Yamamoto1
1: Department of mechanical enegineering
Tokyo University of Science
6-3-1, Niijyuku, Katsushika, Tokyo, Japan, 125-8585
∗ Correspondent author: [email protected]
Flow control to decrease skin-friction drag in turbulent flows is of importance in mitigating the environmental impact and
many control techniques are examined numerically and experimentally. In addition, the heat transfer enhancement is also important in heat transfer devices, for example, while simultaneous achievement of drag reduction and heat transfer enhancement is
usually difficult due to strong analogy between momentum and heat transfer. In this study, we perform direct numerical simulations of the turbulent flows controlled by the traveling wave-like blowing and suction and investigate the drag reduction and heat
transfer performance. The parametric study is conducted to show the effect of the parameter on the control performance.
Figure 1 shows a schematic of the channel flow. The control parameters are amplitude of the wave a, the wavelength λ ,
and the wavespeed c. All simulations are conducted under the constant the mean pressure gradient. The skin-friction Reynolds
number is set to be Reτ = 180 and the Prandlt number is set to be Pr = 1.0. Three different boundary conditions are examined:
the constant temperature difference, the uniform heat flux, and the uniform heat generation. Figure 2 shows maps of the Stanton
number St. We observed not only the skin-friction drag reduction by the the upstream traveling wave (c < ubulk ), but also relaminarization phenomena by the downstream traveling wave case (c > ubulk ) (not shown here). The Stanton number distribution is
similar to that of c f : St/St0 is larger than one when the wave travels in the upstream direction (c/ubulk < 0). The major difference
among different thermal boundary condition is not observed.
In the wall deformation wave case (Uchino et al., 2017), both the skin-friction drag and heat transfer increase and the analogy
factor is larger than unity at the CTD case and no improvement in the analogy factor was confirmed at the uniform heat generation
case. In contrast, the traveling wave-like blowing and suction reduces the skin-friction drag whereas it increases the heat transfer.
This is likely due to the difference between the wall-deformation and blowing and suction.
In the full paper, we chose parameter set of c/ubulk = −1.0 and λ + = 226 and discuss the Reynolds shear stress (RSS) and
the turbulent heat flux profiles. In this case, the skin-friction drag reduction and the heat transfer enhancement are obtained
simultaneously i.e., c f /c f 0 = 0.90 and St/St0 = 1.24. We observed negative Reynolds shear stress and positive turbulent heat
flux in the region near the wall and these are responsible to the simultaneous achievement of the heat transfer enhancement and
the drag reduction.
REFERENCES
Uchino, K., Mamori, H. & Fukagata, K. 2017 Heat transfer in fully developed turbulent channel flow with streamwise
traveling wave-like wall deformation. J. Thermal Sci. Tech. 12, JTST0003, 11 pp.
Figure 1. Traveling wave-like blowing and suction from
walls in the channel flow.
Figure 2. Map of the normalized Stanton number as a
function of wavespeed and wavelength.