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Aerodynamic interaction between wing and truss in transonic flow

Siemons, S.K. (2015) Aerodynamic interaction between wing and truss in transonic flow.

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Abstract:Two-dimensional calculations on biplanes in transonic flow are presented. The effect of stagger was investigated on biplanes with equal chord length and angle of attack, with the gap equal to the chord length. A finite volume method was used to solve the Euler equations on a quadtree Cartesian grid. A multi-level approach to solution-based grid refinement is presented to refine the grid at shockwaves. The airfoils under study are the symmetric NACA0012 and the supercritical RAE2822. For these airfoils the flow was calculated for the free stream Mach numbers M = 0.4, 0.5, 0.6, 0.7, 0.8 and angle of attack AoA = 0, 2, 4, 6, 8 degrees. It was observed that the flow chokes when the airfoils are positioned such that a duct is formed by the overlapping surfaces. The duct than has a geometry similar to a convergent-divergent nozzle. The transition from subcritical flow to supercritical flow, i.e. choked flow, occurs at subcritical flow conditions of the single airfoil. At higher free stream velocity the choked flow changed into to another flow pattern for positive staggered configurations only. The new flow pattern is characterised by an upward angled oblique shockwave at the trailing edge of the upper airfoil followed by a detached normal shockwave. The normal shock connects to the upper surface of the lower airfoil. In case of choked flow the lift and drag are effected in two distinct ways. Firstly, the early transition to supercritical flow increases the drag in comparison with the single airfoil and other biplane configurations. Secondly, the lifting capabilities of both airfoils is decreased because the flow in the duct is almost symmetrical with respect to the upper and lower walls of the duct. The transition from choked flow to a detached normal shock is not observed in the drag polar.
Item Type:Internship Report (Master)
University of Tokyo, Japan
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:transonic flow, biplane, stagger, solution-based grid refinement, choked flow
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