An Experimental Investigation of Leading Edge Vortical Flow about a Delta Wing During Wing Rock PDF Download
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Author: Michael Denis Nelson
Publisher:
ISBN:
Category : Oscillating wings (Aerodynamics)
Languages : en
Pages : 368
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Book Description
Author: Michael Denis Nelson
Publisher:
ISBN:
Category : Oscillating wings (Aerodynamics)
Languages : en
Pages : 368
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Author: National Aeronautics and Space Adm Nasa
Publisher:
ISBN: 9781731351593
Category :
Languages : en
Pages : 162
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Book Description
The vortical flow over a delta wing contributes an important part of the lift - the so called nonlinear lift. Controlling this vortical flow with its favorable influence would enhance aircraft maneuverability at high angle of attack. Several previous studies have shown that control of the vortical flow field is possible through the use of blowing jets. The present experimental research studies vortical flow control by applying a new blowing scheme to the rounded leading edge of a delta wing; this blowing scheme is called Tangential Leading Edge Blowing (TLEB). Vortical flow response both to steady blowing and to unsteady blowing is investigated. It is found that TLEB can redevelop stable, strong vortices even in the post-stall angle of attack regime. Analysis of the steady data shows that the effect of leading edge blowing can be interpreted as an effective change in angle of attack. The examination of the fundamental time scales for vortical flow re-organization after the application of blowing for different initial states of the flow field is studied. Different time scales for flow re-organization are shown to depend upon the effective angle of attack. A faster response time can be achieved at angles of attack beyond stall by a suitable choice of the initial blowing momentum strength. Consequently, TLEB shows the potential of controlling the vortical flow over a wide range of angles of attack; i.e., in both for pre-stall and post-stall conditions. Lee, K. T. and Roberts, Leonard BLOWING; DELTA WINGS; FLOW DISTRIBUTION; LEADING EDGES; VORTICES; AIRCRAFT MANEUVERS; ANGLE OF ATTACK; MOMENTUM; NONLINEARITY; STABILITY...
Author: William H. Wentz (Jr.)
Publisher:
ISBN:
Category : Delta wing airplanes
Languages : en
Pages : 160
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Author: Muneeb Dogar
Publisher:
ISBN:
Category :
Languages : en
Pages :
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"The leading-edge vortical flow structure over a 65 slender (DW65) and a 50 non-slender (DW50) delta wing was investigated at Reynolds number of order 105. Particular emphasis was placed in the variation of vortex flow quantities and critical flow parameters with change in angle of attack and chordwise distance. In addition, the progression of vortex breakdown with angle of attack was documented based on pressure and three-dimensional velocity information. A glimpse of wake-vortex evolution was also discussed. Moreover, aerodynamic lift and drag forces were evaluated based on wake survey analyses and compared with direct force balance measurements. Special attention was focused on drag characterization based on lift dependency where Maskell formulation was adopted for the estimation of induced drag. The results showed that the flow over DW65 and DW50 has some qualitative resemblances but quantitatively they are two contrasting flows. Prior to the breakdown, in the case of DW65, the vortical flow is near-axisymmetric but in the case of DW50, the vortex and axial core never matches and even the definition of distinctive vortex center is often ambiguous except at higher angles of attack, moreover the axial core was always accompanied by large momentum deficit. The variation of vortex flow quantities in streamwise direction showed self-similar behavior when plotted against radial distance scaled by local semi-span while interestingly for DW50 self-similar behavior was showed only by the variation of total pressure loss about the pressure core. It was established that the flow over DW50 was marred by an active interaction of vortical and boundary layer flow due to the close proximity of vortex to the wing surface. For the first time the progression of vortex breakdown over the wing surface was reported on the basis of three-dimensional flow information which elucidated the respective indicators of breakdown for slender and non-slender delta wings. Lastly, wake survey analyses were carried and comparison of different lift computational models and direct measurement were presented. Moreover, the estimation of profile drag is sensitive to the definition of wake region whereas vortex breakdown upstream of trailing-edge resulted in underestimation and overestimation of induced drag and CL, respectively. For all the cases of slender wing and high angle of attack cases of non-slender delta wing showed that the induced drag always constituted more than 50% of the total drag. The results provided here provided a deepened and extended insight on vortical and aerodynamics characteristics of slender and non-slender delta wing. " --
Author: N. G. Verhaagen
Publisher:
ISBN:
Category :
Languages : en
Pages : 16
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A wind-tunnel investigation was performed to study, by employing a laserlight-sheet and oil-flow visualization technique, the flow above and behind a sharp-edge 76 deg, delta wing and two sharp-edged double-delta wing models (76/60 and 76/40 deg., kink at midcord). In addition, balance measurements were performed to determine lift, drag and pitching moment. The tests were carried out for angles of attack from 5 to 25 deg. and at a free-stream velocity of 30 m/sec, corresponding to a Reynolds number of 1400000 x 10 to the 6th power, based on centerline chord. Above both double-delta wings a single-branched strake vortex is formed fed by vorticity from the strake leading edge. Downstream of the leading-edge kink a wing vortex is formed which is conjectured to be single-branched at about 5 deg, angle of attack and double branched at angles of 10 deg., an beyond. The flow pattern downstream of the trailing edge of the 76/60 deg. double-delta wing has been observed to be similar to that behind the delta wing. Above the 76/40 deg. double-delta wing breakdown of both the wing and strake vortices took place ahead of the trailing edge. (Author).
Author: Thomas G. Gainer
Publisher:
ISBN:
Category : Aerodynamic measurements
Languages : en
Pages : 82
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Author: W. H. Wentz
Publisher:
ISBN:
Category : Aerodynamic load
Languages : en
Pages : 140
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Author: Joint Institute for Aeronautics and Acoustics. Joint Institute for Aeronautics and Acoustics
Publisher:
ISBN:
Category :
Languages : en
Pages : 48
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Author: Steven Lynn Morris
Publisher:
ISBN:
Category : Oscillating wings (Aerodynamics)
Languages : en
Pages : 474
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Book Description
This research developed a definitive theory on the cause of wing rock. The study was based on dynamic measurements in both a water tunnel and a wind tunnel on a sharp-edged delta wing with an 80 deg. leading-edge sweep angle. Experimental data were compared with analytical results from a mathematical model and a fourth order Runge-Kutta integration. In the water tunnel tests, conducted at alpha = 35 deg. and Reynolds numbers from 30000/ft to 75000/ft, the movement of the leading-edge vortices and the model motion were simultaneously tracked and analyzed using a video-based motion analysis system, ExpertVision. The initial phase of the study validated ExpertVision accuracy using stationary and forced oscillation tests on 70 deg. and 80 deg. delta wings. Vortex trajectory, core velocity, and burst point results from stationary tests were in good agreement with published data. Forced oscillation tests proved that ExpertVision could simultaneously track and analyze the movement of leading-edge vortices and model motion. Wing rock is caused by the dynamic behavior of the leading edge vortices. The alternate lift-off and reattachment of the vortices generate an asymmetry in vortex lift and cause changes in rolling moment that initiate and sustain roll oscillations. Wing rock dynamics were significantly different water tunnel and wind tunnel experiments. Apparent mass terms must be included in the equations of motion when converting water tunnel acceleration data to rolling moment coefficients; with no apparent mass correction, C sub l calculated from accelerations in the water tunnel were about 15 times greater than those from the wind tunnel. Theses. (JHD).
