October 2022 - Experimental base flow modification on a swept wing using plasma forcing
This work experimentally investigates plasma actuator (PA) forcing effects on the base flow and developing crossflow (CF) instabilities in a swept wing boundary layer. Spanwise-invariant plasma forcing near the leading edge is configured according to the Base Flow Modification (BFM) strategy. The results demonstrate that a PA can reduce the boundary layer CF component, whereas the control authority shows a high dependence on the momentum coefficient. The dissimilar reduction between the streamline-aligned velocity and CF component leads to a local re-orientation of the base flow. Despite the overall reduction in amplitude of stationary CF instabilities, unsteady disturbances are found to be enhanced by the PA forcing. The current results shed light into the underlying principles of BFM-based PA operation, in the context of laminar flow control.
August 2022 - Transition due to isolated roughness in a swept wing boundary layer
The present work is dedicated to the investigation of the effect of an isolated roughness element on a swept wing boundary layer. In particular, the flow modifications incurred by a single cylindrical element applied on a swept wing model are measured, toward describing the nature of the perturbations introduced in the flow field, their development in the near and far wake region, as well as their eventual breakdown. The measurements are performed using infrared thermography and hot wire anemometry.
June 2022 - Direct numerical simulation of interaction between a stationary crossflow instability and forward-facing steps
The interaction between forward-facing steps of several heights and a pre-existing critical stationary crossflow instability of a swept-wing boundary layer is analysed. Direct numerical simulations (DNS) are performed of the incompressible three-dimensional laminar base flow and the stationary distorted flow that arise from the interaction between an imposed primary stationary crossflow perturbation and the steps.
March 2022 - Unsteady interaction of crossflow instability with a forward-facing step
Experiments have been conducted on a swept wing model in a low-turbulence wind tunnel at chord Reynolds number of 2.17 million to investigate the unsteady interaction of a forward-facing step (FFS) with incoming stationary crossflow (CF) vortices. The impact of varying the FFS height on the development and growth of primary and secondary CF disturbances and the ensuing laminar–turbulent transition is quantified through detailed hot-wire anemometry and infrared thermography measurements.
March 2022 - Receptivity of crossflow instability to discrete roughness amplitude and location
The effect of discrete roughness elements on the development and breakdown of stationary crossflow instability on a swept wing is explored. Receptivity to various element heights and chordwise locations is explored using a combination of experimental and theoretical tools. Measurements are performed using infrared thermography, quantifying the transition front location, and planar particle image velocimetry. Measurements are corroborated with simulations based on nonlinear parabolised stability equations.
August 2021 - Impact of a forward-facing step on the development of crossflow instability
The impact of a forward-facing step (FFS) on the development of stationary crossflow instability is investigated on a swept wing model in a low-turbulence wind tunnel at chord Reynolds number of 2.3 million
. Infrared thermography and particle image velocimetry measurements are used to quantify the transition location and growth of the crossflow instability under the influence of FFSs with different heights. The experiments reveal a novel transition delay effect for the shortest step height investigated.
