Effects of Perturbation on the Flow over Nonslender Delta Wings

Abstract

An experimental investigation is presented to reveal the flow physics and turbulence statistics of nonslender delta and diamond wings with a sweep angle of  = 40 under perturbation condition with the amplitude of α =  +αsinet = ±0.5 during Te=2/e= 0.5s. The experiments are carried out using the techniques of dye visualization and Stereoscopic Particle Image Velocimetry (stereo-PIV) on the plan view and cross flow plane for the cases of stationary and perturbed wing as the angle of attack is varied within 7 o ≤≤17 o . In order to perform a comparison based on the wing planform, diamond wing is designed from the composition of same shape of the delta wing and an attachment part mounted on its trailing edge. This study also provides information about effects of trailing edge attachment mounted on a generic nonslender delta wing under current test conditions. It can be concluded that perturbation is beneficial in the control of flow over both wings at relatively high angles of attack, .The duration required for occurrence of flow control increases for the current period and time of perturbation, when the trailing edge attachment (diamond wing case) is employed. Beyond this, trailing edge attachment takes role in attenuation of turbulence statistics, where leading edge vortex breaks down. Nomenclature  = angle of attack, deg  = mean angle of attack, deg e = angular velocity of wing perturbation, rad/s Te = period of wing perturbation, s fe = perturbation frequency of the wing, s a(t) = dynamic angle of attack of the wings, deg U = free stream flow velocity, mm/s C' = chord of delta wing, mm C = chord of diamond wing, mm Λ = sweep angle, deg Ψ = stream function ω = vorticity 1 *Assist. Professor, 2 t = time (s) TKE = turbulence kinetic energy wRMS = RMS of vertical velocity fluctuation Re = Reynolds number based on chords of the wings <> = time-averaged quantitiy x= distance from the wing apex measured in the free-stream flow direction y = distance from the chord axis in transverse direction

Salınım hareketinin sapma açısı altındaki bir delta kanada etkileri

“…Canpolat et al [28] studied the turbulence statistics experimentally, and the structure of leading-edge vortices over 40° swept diamond and delta wings. The wings were exposed to perturbation with the amplitude of α0=±0.5º and oscillation period of Te=0.5s.…”

“…The patterns of time-averaged vorticity and transverse velocity components for the delta wing under perturbed and static conditions at a mean angle of attack, αm=10° [28].…”

Flow Behavior in Side-View Plane of Pitching Delta Wing

“…[8] defined flow separation and integration on the surface of wing via numerical methods for the delta wings having sweep angles, Λ of 65° and 76°/40°. [9] experimentally investigated the flow structure and turbulence statistics of non-slender delta and diamond wings having sweep angle, of Λ=40°. As shown in Figure 3, wings are subjected to perturbation with the amplitude of α o =±0.5° and oscillating period of T e =0.5s.…”

“…Patterns of time-averaged vorticity, <> and contours of transverse velocity components, <V/U> of the delta wing under static and perturbed conditions having the mean angle of attack, α=10°[9] …”