Numerical Studies of Interference of Vortex Generator and a Wing with Air Propeller

Аuthors

Baghdadi M. K.

Moscow Institute of Physics and Technology (National Research University), 9, Institutskiy per., Dolgoprudny, Moscow region, 141701, Russia

e-mail: m.khir.baghdadi@gmail.com

Abstract

Local aerodynamics plays an important role in aviation. Even small changes in the geometric shape of the aircraft separate structural elements in the area of vortex bundles forming affect significantly the vortex structure, its interaction with the aircraft elements and, eventually, its aerodynamic characteristics.
As of today, vortex generators are increasingly applied in aerodynamics to improve the wing flow-around and strife the boundary layer separation. Typically, the vortex generator represents a small elongation wing set normal to the surface at the certain angle of attack to the incoming flow direction to form a longitudinal tip vortex. Vortex generators application relates to the passive methods of flow control and leads to a slowdown or complete elimination of flow disruption due to redistribution of the longitudinal momentum of the moving medium.
With optimal arrangement of the vortex generators, the boundary layer separation from the wing surface may be significantly reduced. However, in real flight, especially in conditions of separation flow, the incoming flow to the vortex generator ensuring at the desired angle is rather difficult. It should be noted herewith that the vortex generator smooth operation ensuring requires a certain angle of attack and its stable flow-around by the airflow.
The article presents a numerical study on the effect on the vortex generator separation zone and the hinge moments of the deflected flap. The authors proposed installing the vortex generator in the airflow behind the air propeller to sustain constant flow-around of the vortex generator 
The computational model under study is a straight wing with a symmetrical NACA 642A015 profile, with two flaps and a puller propeller of a 0.23 m diameter installed in its mid-length. The computations were performed at the propeller rotation at 10,000 rpm. The relative pitch ratio the propeller is J = 1. 
To ensure stable operation of the vortex generator, it was placed behind the propeller on the wing upper surface at an angle of 45° to the incoming flow, which was selected according to the design specifics of the model and installation angle of the propeller blades.
The computations were performed on a structured grid containing about 20 million cells. To compute the air movement, two zones were built: the first zone with translational air movement impinging on the wing model under study at the speed of V = 40 m/s, and the second computational zone with rotational air movement around the rotor blades. 
The numerical study was accomplished by the program based on solving the Reynolds-averaged Navier–Stokes equations, under experimental conditions in a wind tunnel with a wing elongation of λ = 2.8, as well as in free air flow with a wing elongation of λ = 5 at numbers M = 0.12 and Re = 0.7106 within the range of angle of attack of –20° ≤ AoA ≤ 20°.
Numerical studies of the wing interference with a propeller and a vortex generator revealed that a vortex generator might be applied to reduce the separation zone on the wing, the drag, as well as the hinge torque of the deflected wing mechanization.
The article demonstrates the practicability of the vortex generator placement behind the air propeller, which ensures a certain angle of airflow and necessary velocity of the incoming flow, to ensure favorable interference.

Keywords:

aerodynamic characteristics, straight wing, vortex generator, pulling propeller, flow disruption from the wing, hinge moments, CFD-methods

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