Insights into the particle-free and particle-laden turbulent flow statistics in sharply bent channels

Turbulence in canonical wall-bounded and particle-laden flows shows a wide range of regimes due to considerable interaction between scales. Reynolds number is primarily used to characterize the fluid dynamics and particle-laden fluid corresponding to single phase and particle-laden channel flows. Nonetheless, different flow behaviour exists in curved channels even at a fixed Reynolds number, as delineated by Geert Brethouwer (J. Fluid Mech., vol. 931, 2022, pp. A21). In our study, we show the behavior of wall-bounded turbulent flows with and without particles in sharply bent channels by exploring the time averaged velocity profiles at various channel cross-section. The well-known logarithmic behaviour of the time averaged normalized velocity profile is found to be retained, where the von Kármán and the additive constants assume altered values depending on the bend angle. An enhanced near-wall fluctuations at the bend is obtained owing to the diffusion of counter rotating vortices that led to increased turbulent activity in case of particle-free as well as in particle-laden turbulent channel flows. Turbulent kinetic energy (TKE) budget for particle-free and particle-laden cases are elaborated for various bend inclinations at different sections of the channel, which establish that TKE is modulated at the bend with an overall attenuation on loading the channel with particles.