Laser Doppler velocimetry investigation of near wall turbulence reduction in Couette‑Modified Poiseuille Flow in a Square Duct

Couette–Poiseuille flow represents a fundamental fluid dynamic scenario characterized by simultaneous pressure-driven flow (Poiseuille component) and boundary-driven flow (Couette component).

There is a lack of comprehensive understanding of turbulence control in pressure-driven flow with moving walls in the current literature. Prior research on similar configurations was mainly based on numerical approaches, with limited experimental validation. Owolabi et al. (2019) analysed laminar flow in a square duct and explained the significant role of wall motion in the flow profile but did not include the consideration of turbulent conditions in their study. Thurlow et al. (2000) analysed Couette–Poiseuille flow in a planar duct where wall motion created significant changes in the velocity profiles. The research of Thurlow et al. (2000) was based on low relative wall speed experiments, in which slight decreases in near-wall turbulence were observed without considering the effects of high relative wall motions.

In an effort to address the current knowledge gap, the current research investigates experimentally the effects of a moving wall (Couette component) with a substantial relative speed on the production of turbulence in pressure-driven water flow through a square duct using the technique of laser Doppler velocimetry (LDV) measurements. Velocity and turbulence intensity profiles were measured in the vertical and in the horizontal duct cross-section at different wall velocities in comparison with the centreline flow velocity. It was observed that the reduction in turbulence intensity near the moving wall is significant, especially for wall velocity close to the centreline flow velocity. This mitigation of turbulence is attributed to the removal of mean shear as a turbulence production mechanism caused by the moving wall.



Thurlow, E.M. and Klewicki, J.C. (2000) ‘Experimental study of turbulent Poiseuille–couette flow’, Physics of Fluids, 12(4), pp. 865–875. doi:10.1063/1.870341.

Owolabi, B.E., Dennis, D.J. and Poole, R.J. (2019) ‘Entry length requirements for two- and three-dimensional laminar couette–Poiseuille flows’, Journal of Fluids Engineering, 141(12). doi:10.1115/1.4043986.