Download or read book A Digital Particle Image Velocimetry Investigation of Delta Wing Vortex Flow and Vortex Breakdown written by Jeremy David Wimer and published by . This book was released on 2003-01-01 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vortical flow over the suction side of a 650 sweep delta wing at high angles of attack is investigated in the University of Washington water tunnel using digital particle image velocimetry (DPIV). The method is first validated and then used to qualitatively and quantitatively describe the development of the leading edge vortex (LEV) both upstream and downstream of vortex breakdown. The circulation and azimuthal velocity profile in the vortex are measured and reveal that the maximum circulation of the LEV increases nearly linearly in the downstream direction up to the point of vortex breakdown. Circulation and velocity measurements in the solid-body rotational part of the LEV core, however, reveal that once the core is formed near the apex of the wing, the circulation there remains constant until just prior to breakdown, and no further vorticity is added to the core from the shear layer. The secondary vortex is found to be the key player in separating the primary vortex core from the shear layer. This model of the flow field contradicts the generally accepted conical nature of delta wing flow. Current vortex breakdown suppression methods are analyzed in light of this new model. A numerical simulation based on the vortex filament method is also used to further the self-induction theory of vortex breakdown.
Download or read book A Study of the Reverse Delta Wing Using Particle Image Velocimetry PIV written by Afaq Altaf and published by . This book was released on 2011 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: Particle Image Velocimetry was used in a low speed wind tunnel to investigate the vortex structures of a slender reverse delta wing at various angles of attack and roll. This work investigates the characteristics of the vortices generated downstream in planes perpendicular to the free stream direction and their dependence on angles of attack and roll at chord-based Reynolds number of Rec=3.82×105. The peak tangential velocities show a trend similar to a delta wing. A six component force balance was used to obtain the aerodynamic coefficients for a reverse delta wing and a delta wing. A qualitative comparison with existing computational results is executed for velocity vectors and surface pressure contours; whereby the computational results of surface pressure contours agree with the six component force balance results, revealing that a regular delta wing exhibits a higher CL than a reverse delta wing. It can be concluded that a regular delta wing vortex at a particular angle of attack exhibits a tangential velocity magnitude twice that of a reverse delta wing; exhibits higher circulation and vorticity than a reverse delta wing vortex.
Download or read book Vortex flow and vortex breakdown above a delta wing in high supersonic flow written by Sharon Rose Donohoe and published by . This book was released on 1996 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of the Vortex Flow Over Delta and Double Delta Wings at Low Speed written by N. G. Verhaagen and published by . This book was released on 1983 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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).
Download or read book Laser Velocimetry Measurements of Vortex Flows on a Delta Wing at Mach 1 9 written by Linda G. Smith and published by . This book was released on 1993 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Off-body flow visualizations and fluid velocity measurements are conducted in a supersonic vortex flow. Three-dimensional laser velocimetry measurements are made in the leeward flowfield over a simple sharp-edged delta wing with 75 degree sweep angle. Tests are conducted at Mach 1.9 and Reynolds number of 2.4 x 10(exp 6) based on model root chord. Measurements are made at 40% and 80% chord positions for 20 and 30 degree angles of attack and at 40% chord for 35 degrees. Mean velocities and turbulence intensities are measured on the five planes. Measurement accuracy is discussed in detail. The measurements define the location of the vortex core and provide the flowfield velocities surrounding the vortex. The difficulties inherent with seeding high velocity vortex flows are discussed ... Laser Velocimetry Measurement of Vortical Flowfields.
Download or read book An Experimental Investigation of Leading Edge Vortices and Passage to Stall of Nonslender Delta Wings written by and published by . This book was released on 2003 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Comprehensive Study of Vortex Breakdown Flow Mechanisms Computational Investigation and Preliminary Control written by and published by . This book was released on 2004 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: A modified vortex filament method is used to simulate the evolution of the transient formation of vortex breakdown. The method supports previous studies, illustrating that vortex breakdown. The method supports previous studies, illustrating that vortex breakdown is initiated by a negative vorticity gradient which triggers an inviscid self-induction feedback mechanism and when subsequently subjected to viscous effects, results in steady state vortex breakdown. The results of the method are first validated experimentally with numerous past dye flow visualization and particle image velocimetry investigations, and then used to qualitatively investigate the self-induction flow mechanisms during the formative stages of stages of transient breakdown. As a complement to the qualitative investigation, a quantitative analysis is performed, which yields a local and dynamical relationship relating the azimuthal vorticity gradient at a particular location to the curvature of the instantaneous streamline, projected onto the meridional plane, at the same location. This relationship further shows that once radial expansion commences in the region of negative azimuthal vorticity, it continues to expand such that the meridional streamline becomes more curved with time, supporting that the negative vorticity gradient not only initiates the radial expansion, but also, feeds its subsequent growth. On the contrary, in the region of a positive gradient, the streamline continues to flatten fostering radial contraction of the vortex tube, which provides a closure to expansion. In attempt to suppress breakdown in two preliminary control simulations, this positive azimuthal vorticity gradient is then introduced to the vortex flow just prior to breakdown. Results from these control simulations illustrated a temporal and spatial delay in breakdown as well as exhibiting flow behavior associated with complete elimination of breakdown.
Download or read book A Comprehensive Study of Vortex Breakdown Flow Mechanisms written by William Frederick Johnson and published by . This book was released on 2004 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Fluid Dynamics Investigation of Vortex Breakdown for a Delta Wing at High Angle of Attack written by Jacob A. Freeman and published by . This book was released on 2003-03-01 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: Using the commercially available FLUENT 3-D flow field solver, this research effort investigated vortex breakdown over a delta wing at high angle of attack (a) in preparation for investigation of active control of vortex breakdown using steady, along- core blowing A flat delta-shaped half-wing with sharp leading edge and sweep angle of 600 was modeled at a 180 in a wind tunnel at Mach 0,04 and Reynolds number of 3,4 x 10(sub 5). A hybrid (combination of structured and unstructured) numerical mesh was generated to accommodate blowing ports on the wing surface. Results for cases without and with along-core blowing included comparison of various turbulence models for predicting both flow field physics and quantitative flow characteristics, FLUENT turbulence models included Spalart-Allmaras (S-A), Renormalization Group k-e, Reynolds Stress (RSM), and Large Eddy Simulation (LES), as well as comparison with laminar and inviscid models. Mesh independence was also investigated, and solutions were compared with experimentally determined results and theoretical prediction, These research results show that, excepting the LES model for which the computational mesh was insufficiently refined and which was not extensively investigated, none of the turbulence models above, as implemented with the given numerical grid, generated a solution which was suitably comparable to the experimental data. Much more work is required to find a suitable combination of numerical grid and turbulence model.
Download or read book A Study of the Vortex Flow Over 76 40 deg Double delta Wing written by N. G. Verhaagen and published by . This book was released on 1995 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Measurement of Vortex Breakdown Over a Delta Wing Using a Laser Anemometer written by and published by . This book was released on 1974 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unsteady Three Dimensional Aerodynamic Flow written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall objective of this program is to determine the instantaneous flow structure on delta wings at high angle-of-attack, as well as from cylindrical bodies, which are subjected to basic classes of motion. New techniques of high-image density particle image velocimetry provide the instantaneous vorticity fields and streamline patterns, thereby allowing interpretation of the underlying physics using critical point theory. This type of quantitative interpretation of the flow structure is crucial for performing vorticity balances on wings and bodies and thereby optimization of overall performance characteristics. Furthermore, for the case of the delta wing at high angle-of-attack, local control techniques are applied simultaneously at leading and trailing-edges of the wing, in order to alter the crucial features of vortex breakdown and subsequent large-scale stall. Such control techniques have application to a wide variety of separated flows from wings and cylindrical bodies.
Download or read book Numerical Investigation Into Vortical Flow about a Delta wing Configuration Up to Incidences at which Vortex Breakdown Occurs in Experiment written by J. I. van den Berg and published by . This book was released on 1994 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of the Vortex Flow Over 76 40 Deg Double Delta Wing written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-10-22 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: A low-speed wind-tunnel study of the flow about a 76/40-deg double-delta wing is described for angles of attack ranging from -10 to 25 deg and Reynolds numbers ranging from 0.5 to 1.5 Million. The study was conducted to provide data for the purpose of understanding the vortical flow behavior and for validating Computational Fluid Dynamics methods. Flow visualization tests have provided insight into the effect of the angle of attack and Reynolds number of the vortex-dominated flow both on and off of the surface of the double-delta wing. Upper surface pressure recordings from pressure orifices and Pressure Sensitive Paint have provided data on the pressures induced by the vortices. Flowfield surveys were carried out at an angle of attack of 10 deg by using a thin 5-hole probe. Numerical solutions of the compressible thin-layer Navier-Stokes equations were conducted and compared to the experimental data. Verhaagen, N. G. and Jenkins, L. N. and Kern, S. B. and Washburn, A. E. Langley Research Center NAS1-19480; RTOP 505-90-52-01...
Download or read book Characterization and Control of Vortex Breakdown Over a Delta Wing at High Angles of Attack written by Anthony M. Mitchell and published by . This book was released on 2000-08-01 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: Demands for more maneuverable and stealthy air vehicles have encouraged the development of new control concepts for separated flows. The goalof this research is the control of leading-edge vortex breakdown by open-loop, along-the-core blowing near the apex of a delta wing to improve lift and maneuverability at high angles of attack. Control is dependent on the knowledge of and the ability to detect principle characteristics of the phenomena. Therefore, an experimental study of a 700 delta wing was accomplished to better understand the physical properties of the vortical flow and the vortex breakdownphenomena. Multiple experimental methods were used to characterize the flow field and its influence on the model's surfaces as well as to identify parameters for closed-loop feedback control.
Download or read book Vortex Flow Behavior Over Slender Delta Wing Configurations written by Xing Z. Huang and published by Springer Verlag. This book was released on 2008-10-01 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book discusses the behavior of vortices over sharp and highly swept wing configurations used for current and future military aircraft. Special attention is paid to the effects of critical flow phenomenon such as vortex breakdown occuring at high angles of attack or high angular rates. The wind tunnel experiments conducted on delta-wing configurations in wind tunnels in Canada, Europe, Russia and the United States are given in eight chapters. The experiments provide an extended data base that gives insight into the effects of the angle of attack, angular rate, Reynolds number and Mach number on the behavior of vortices over several slender delta wings in stationary and instationary flights. A critical assessment is given in a separated chapter of the available experimental data bases and out of these data, one and the same data set is selected for the validation and verification of analytical and numerical solutions.Comprehansive computational results are given in another ten chapters. Steady-state and time-accurate solutions for the steady and unsteady flow over the selected delta-wing configuration are discussed. These solutions are generated using structured and unstructured grid methods.The analytical solutions for the flow over a delta wing are discussed and compared with experimental data in three more chapters.In the final chapter a validation and verification of the analytical and CFD solutions is given.
Download or read book Investigation of the Vortex Flow Over a Sharp edged Delta Wing in the Transonic Speed Regime written by W. J. Bannink and published by . This book was released on 1989 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt:
