Abstract
In this paper, 3D numerical simulations have been carried out to enhance the understanding of a flow over a passive control device composed of micro cylinder with, d/c = 1.34% placed in the vicinity of NACA0012 aerofoil wing, by means of γ–Reθt transition sensitive turbulence model meant to predict the separation induced by transition achieved for aerofoils operating at moderate Reynolds number (Re = 4.45×105). Results show that the separation of the boundary layer has been eliminated by the passive static vortex generator at stall regime due to the injection of free-stream momentum to the boundary layer. The early transition to turbulent state overcomes the local flow deceleration of an adverse pressure gradient and remains sticked to the wall the boundary layer. Furthermore, the wing aerodynamic performance are improved as drag is reduced and lift is enhanced which is straight forward linked to the lift to drag ratio gain that varies from 22.68% to 134.17% at post stall angles of attack.
Highlights
In recent decades, controlling flows has sparked lots of attention in fluid mechanics given its positive impact on industrial applications
For α > 5°, a return flow zone begins to appear at the trailing edge going towards the leading edge with as α increased. This area is indicated by negative average velocity. This reveals that the turbulent separation of the boundary layer occurs gradually as it moves towards the leading edge
Figure.3.b, shows the average speed taken on the center line of the wingspan at suction side for the controlled case, in the presence of the off surface vortex generator in form of cylinder of dimension, d/c = 1.34% located at 3×d from the leading edge to its centerline
Summary
In recent decades, controlling flows has sparked lots of attention in fluid mechanics given its positive impact on industrial applications. Airfoils are one of the most fundamental components of aircraft and UAVs, and its aerodynamic performance has a direct impact on their efficiency. Passive flow control techniques are focused to accelerate boundary layer transition from laminar to turbulent state, mainly by modifying geometrical shape of bodies. Improving wing performance doesn’t require to inject an external energy to assist the flow. These techniques are inspired from nature so that several impressive control mechanisms can be observed as vortex generators such as, fish skin and flippers, bird wings, insect bodies, groovs, roughness elements slots and more. Which are steady integrated to the body (on-surface) itself to alter natural flow state to the desirable condition
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