Streamwise-varying steady transpiration control in turbulent pipe flow

Abstract

The effect of streamwise-varying steady transpiration on turbulent pipe flow is examined using direct numerical simulation at fixed friction Reynolds number Re τ = 314. The streamwise momentum equation reveals three physical mechanisms caused by transpiration acting in the flow: modification of Reynolds shear stress, steady streaming and generation of non-zero mean streamwise gradients. The influence of these mechanisms has been examined by means of a parameter sweep involving transpiration amplitude and wavelength. The observed trends have permitted identification of wall transpiration configurations able to reduce or increase the overall flow rate −36.1% and 19.3% respectively. Energetics associated with these modifications are presented.A novel resolvent formulation has been developed to investigate the dynamics of pipe flows with a constant cross-section but with time-mean spatial periodicity induced by changes in boundary conditions. This formulation, based on a triple decomposition, paves the way for understanding turbulence in such flows using only the mean velocity profile. Resolvent analysis based on the time-mean flow and dynamic mode decomposition based on simulation data snapshots have both been used to obtain a description of the reorganization of the flow structures caused by the transpiration. We show that the pipe flows dynamics are dominated by a critical-layer mechanism and the waviness induced in the flow structures plays a role on the streamwise momentum balance by generating additional terms.

On the use of transpiration patterns for reduction of pressure losses

“…It is known that short wavelength longitudinal grooves (riblets) can reduce drag by forcing the stream to lift above the grooves (Walsh 1980, 1983). It is also known that long wavelength longitudinal grooves can lead to drag reduction through changes in the distribution of the bulk flow (Szumbarski, Blonski & Kowalewski 2011, Moradi & Floryan 2013; Mohammadi & Floryan 2013 a , 2014, 2015; Mohammadi, Moradi & Floryan 2015, Chen et al. 2016; DeGroot, Wang & Floryan 2016; Raayai-Ardakani & McKinley 2017; Yadav, Gepner & Szumbarski 2017, 2018).…”

Resolvent analysis of turbulent channel flow with manipulated mean velocity profile

“…The usefulness of resolvent analysis has been confirmed for various manipulated turbulent flows, e.g., opposition control (Luhar et al, 2014), suboptimal control (Nakashima et al, 2017), streamwise-varying steady transpiration (Gómez et al, 2016), and a channel flow under spanwise rotation (Nakashima et al, 2019). In paticular, resolvent analysis reveals which mode is amplified or suppressed in the spectral space when a specific control is applied.…”

Similarity laws for transpired turbulent flows subjected to pressure gradients, separation and wall heat transfer

“…DNS of a spatially developing turbulent boundary layer with uniform blowing and uniform suction was performed by KAMETANI & FUKAGATA (2011) and of a Couette flow with wall transpiration by KRAHEBERGER et al (2018KRAHEBERGER et al ( , 2017. There are also many works where DNS were used to explore the effects of unconventional distributions of the transpiration velocity or the surface permeability in flow control and drag reduction schemes (CHOI et al, 1994;G ÓMEZ et al, 2016;JIM ÉNEZ et al, 2001;MIN et al, 2006;QUADRIO et al, 2007;ROSTI et al, 2015).…”