Abstract:In the present experimental study, effects of yaw angle, β on the flow structure at high angles of attack, α with 70° sweep angle, Λ were investigated using the dye visualization technique. In the case of zero yaw angle, β a pair of leading edge vortices take place on both sides of cords axis are more or less symmetrical over the delta wing. These symmetrical vortical flow structures start deteriorating when angle yaw, β is introduced. Onset of vortex breakdown location on the windward side occurs further upst… Show more
“…It has been observed that there is no reversed flow zone at α = 25°; however, the reversed flow zone (circulations) takes place at α = 35° when β is higher than 8°. As stated by Karasu, 43 while LEV breakdown occurs at about x/c = 1 at α = 25° and β = 0°, the onset of the breakdown of LEV occurs at about x/c = 0.6 at α = 35° and β = 0°, so one can conclude that if LEV breakdown happens over the wing surface, the reaction of the flow over a delta wing against to β is higher.Figure 4.Time-averaged streamline, < Ψ >, patterns at α = 25° and 35° for β = 0°, 8°, 12°, and 20°.…”
In this study, extensive instantaneous velocity measurements were conducted within a flow area by stereo particle image velocimetry (SPIV) to investigate the influence of the yaw angle, β, on the vortical flow structure formed on a slender delta wing. This sideslip angle, β, in the yaw plane was varied from 4° up to 20° with an interval of 4° at two critical angles of attack, α = 25° and 35°, respectively. In order to reveal the influence of the yaw angle, β over the flow structure of the delta wing, time-averaged flow statistics, and instantaneous flow data obtained by the SPIV technique in the plan-view plane close to the suction surface of the delta wing were presented. It was observed that even a low yaw angle, for instance β = 8°, becomes to be effective on the flow characteristics of the delta wing, and this effect was augmented with increasing β. The influence of β is quite high on the vortical flow structure at α= 35° compared to the angle of attack of α = 25°. The flow structure that is symmetrical with respect to the centerline of the wing in the case of no yaw has disrupted with the existence β. Furthermore, the extent of the asymmetry enlarges with increasing β. The leading-edge vortex (LEV) on the windward side broken earlier and dominated the flow on the wing surface. It is concluded that this asymmetric flow structure can deteriorate the aerodynamic performance and cause other adverse effects such as unsteady loading.
“…It has been observed that there is no reversed flow zone at α = 25°; however, the reversed flow zone (circulations) takes place at α = 35° when β is higher than 8°. As stated by Karasu, 43 while LEV breakdown occurs at about x/c = 1 at α = 25° and β = 0°, the onset of the breakdown of LEV occurs at about x/c = 0.6 at α = 35° and β = 0°, so one can conclude that if LEV breakdown happens over the wing surface, the reaction of the flow over a delta wing against to β is higher.Figure 4.Time-averaged streamline, < Ψ >, patterns at α = 25° and 35° for β = 0°, 8°, 12°, and 20°.…”
In this study, extensive instantaneous velocity measurements were conducted within a flow area by stereo particle image velocimetry (SPIV) to investigate the influence of the yaw angle, β, on the vortical flow structure formed on a slender delta wing. This sideslip angle, β, in the yaw plane was varied from 4° up to 20° with an interval of 4° at two critical angles of attack, α = 25° and 35°, respectively. In order to reveal the influence of the yaw angle, β over the flow structure of the delta wing, time-averaged flow statistics, and instantaneous flow data obtained by the SPIV technique in the plan-view plane close to the suction surface of the delta wing were presented. It was observed that even a low yaw angle, for instance β = 8°, becomes to be effective on the flow characteristics of the delta wing, and this effect was augmented with increasing β. The influence of β is quite high on the vortical flow structure at α= 35° compared to the angle of attack of α = 25°. The flow structure that is symmetrical with respect to the centerline of the wing in the case of no yaw has disrupted with the existence β. Furthermore, the extent of the asymmetry enlarges with increasing β. The leading-edge vortex (LEV) on the windward side broken earlier and dominated the flow on the wing surface. It is concluded that this asymmetric flow structure can deteriorate the aerodynamic performance and cause other adverse effects such as unsteady loading.
“…Overall scene of vortex bursting close to the delta wing surface is presented in Figure 3 (Karasu et al, 2015). As seen in the figure, yaw angle, ȕ influences onset of vortex location in dramatically.…”
Section: Fig 1 Types Of Vortex Bursting In a Tubementioning
Abstract. Present investigation focuses on unsteady flow structures in end-view planes at the trailing edge of delta wing, X/C=1.0, where consequences of vortex bursting and stall phenomena vary according to angles of attack over the range of 25° Į 35° and yaw angles, ȕ over the range of 0° ȕ 20°. Basic features of counter rotating vortices in end-view planes of delta win with 70° sweep angle, ȁ are examined both qualitatively and quantitatively using Rhodamine dye and the PIV system. In the light of present experiments it is seen that with increasing yaw angle, ȕ symmetrical flow structure is disrupted continuously. Dispersed wind-ward side leading edge vortices cover a large part of flow domain, on the other hand, lee-ward side leading edge vortices cover only a small portion of flow domain.
“…In addition to other studies PIV measurement [21] is being provided hydrodynamics of flow structures, domain of the wake region, locations of the singular points, and locations of the peak values of turbul12ence quantities, such as, the concentration of vorticity, Reynolds stresses, velocity fluctuations and turbulent kinetic energy which are substantially affected by the variation of the Reynolds numbers. The presence of a reversed flow in the region of cavities magnifies the level of these flow characteristics when the Reynolds number is increased.…”
The aim of the study is to determine the flow characteristics of corrugated duct. The whole study has been conducted for Reynolds numbers, Re=4000 and 6000. The corrugated duct geometry was designed for aspect ratios, s/H=0.3 and phase shift angle, φ=180. Variations in flow characteristics of corrugated duct were investigated using the Particle Image velocimetry (PIV) technique. Time-averaged velocity distributions, patterns of streamline and corresponding turbulent statistics were determined. Augmentation of the Reynolds number leads to an increase in velocity due to the sharp corner edges of cavity. Dimensionless turbulent kinetic energy, contours indicate that the magnitude of turbulent kinetic energy, increases as a result of sharp corner edges of the cavities. High rate of momentum transfer is expected due to an increase of turbulence intensity.
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