Direct numerical simulation of spatially developing turbulent boundary layers with uniform blowing or suction

Abstract

Direct numerical simulation (DNS) of spatially developing turbulent boundary layer with uniform blowing (UB) or uniform suction (US) is performed aiming at skin friction drag reduction. The Reynolds number based on the free stream velocity and the 99 % boundary layer thickness at the inlet is set to be 3000. A constant wall-normal velocity is applied on the wall in the range, −0.01U ∞ 6 V ctr 6 0.01U ∞ . The DNS results show that UB reduces the skin friction drag, while US increases it. The turbulent fluctuations exhibit the opposite trend: UB enhances the turbulence, while US suppresses it. Dynamical decomposition of the local skin friction coefficient c f using the identity equation (FIK identity) (Fukagata, Iwamoto & Kasagi, Phys. Fluids, vol. 14, 2002, pp. L73-L76) reveals that the mean convection term in UB case works as a strong drag reduction factor, while that in US case works as a strong drag augmentation factor: in both cases, the contribution of mean convection on the friction drag overwhelms the turbulent contribution. It is also found that the control efficiency of UB is much higher than that of the advanced active control methods proposed for channel flows.

Effect of uniform blowing or suction on hypersonic spatially developing turbulent boundary layers

“…This indicates that uniform blowing enhances the turbulence intensities, whereas uniform suction suppresses the turbulence intensities. These opposite effects are similar to those observed in incompressible flow [4]. In addition, uniform blowing reduces the mean density and increases the mean temperature, whereas uniform suction increases the mean density and reduces the mean temperature.…”

“…Direct numerical simulations (DNSs) provide accurate data that can be used to study the underlying physics of drag reduction. In a recent DNS [4] of an incompressible spatially developing turbulent boundary layer with uniform blowing or suction applied on the wall, the drag reduction mechanism was quantitatively explained by the Fukagata, Iwamoto and Kasagi (FIK) identity [5]. Compared with incompressible flows, far fewer studies have been reported for high-speed (hypersonic) flows.…”

A Linearized $$k-\epsilon $$ k - ϵ Model of Forest Canopies and Clearings

“…The second-order accurate finite difference method is used in the LES code, which is based on the direct numerical simulation (DNS) code of Kametani and Fukagata (2011). A staggered grid system, where the velocities are defined on the cell surface, while the pressure and the eddy viscosity are located at the cell centre, is used in the present model.…”

“…The flow field of a turbulent boundary layer at a low Reynolds number (with friction Reynolds number of Re τ = u τ δ/ν ≈ 180, which corresponds to Re = U ∞ δ/ν ≈ 3000), originally used in the DNS code of Kametani and Fukagata (2011), was used as the initial field. The non-dimensional timestep tU ∞ /δ was set to be 1×10 −3 .…”

Friction drag reduction of a spatially developing boundary layer using a combined uniform suction and blowing

“…The uniform suction improves the stability of the laminar boundary layer: the transition will be delayed and the overall friction drag will be reduced due to the extended laminar region (Joslin, 1998). In contrast, the uniform blowing is known to reduce the drag in the fully-turbulent regime, as studied, e.g., by Kametani and Fukagata (2011). Therefore, a combination of suction and blowing is expected to be effective for flows involving laminar-turbulent transition, such as the flow around an airfoil, by delaying the transition near the trailing edge and by reducing the turbulent drag in the post-transition (i.e., fully-turbulent) region (Liu et al, 2010).…”