Download or read book Vortical Flows Over Delta Wings and Numerical Prediction of Vortex Breakdown written by John A. Ekaterinaris and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Time Accurate Euler Calculations of Vortical Flow Over a Delta Wing in Rolling Motion written by and published by . This book was released on 2003 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents the results of research conducted by Alenia (Italy), Dasa (Germany), DERA (United Kingdom), NLR (The Netherlands), and DLR (Goettingen, Germany) as part of the Western European Armaments Group (WEAG) TA15 program, Common Exercise V. The WEAG TA15 program was a collaborative program concerned with the investigation of steady and unsteady vortical flows over military aircraft configurations. An important component of the program were the Common Exercises (CE), which promoted the exchange of knowledge between the participating nations and aided the development of computational methods to predict vortical flows. As the analysis of flow fields about rolling delta wings is of high interest, the last CE of this group concentrated on the numerical and experimental investigation of unsteady flow over a 65 degree swept delta wing in rolling motion at transonic speed. Guided by previous work on unsteady motions, the numerical investigation was again restricted to unsteady Euler methods. Each participant for the numerical calculations was asked to perform unsteady Euler calculations for given test cases using a mandatory grid and a given number of physical time steps per period. Numerical calculations with different unsteady Euler methods using a common grid were performed at a constant rolling rate of omega(r)=0.0762 for different angles of incidence: alpha(sub 0)=0 degrees, alpha(sub 0)=10 degrees, and alpha(sub 0)=17 degrees. The numerical results reveal that the different spatial discretizations lead to characteristic differences mainly in the magnitudes of the vortex-induced suction peaks in the unsteady pressure distributions and in the prediction of vortex breakdown. The results should finally result in the development of a data base for further code validation. (13 figures, 14 refs.).

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 Numerical Simulation of Transient Vortex Breakdown Above a Pitching Delta Wing written by and published by . This book was released on 1994 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational results are presented for transient vortex breakdown above a delta wing subject to a pitch-and-hold maneuver to high angle of attack. The flows are simulated by solving the full three-dimensional Navier-Stokes equations on a moving grid using the implicit Beam-Warming algorithm. An assessment of the effects of numerical resolution, and favorable comparison with experimental data suggest the computational approach captures the basic dynamics of this transient breakdown. The pressure gradient along the vortex axis is found to play a dominant role in the initiation of breakdown. A description of the three-dimensional instantaneous structure of the flow field is provided for the first time using critical-point theory. The reversed-flow region in the vortex core is associated with pairs of opposite spiral/saddle critical points. At its onset, the vortex breakdown is fairly axisymmetric; however, as it proceeds upstream and a stronger transition takes place along the axis, asymmetric effects become important and result in the formation of a bubble-type breakdown. This bubble structure is open and contains within itself a pair of stagnation points which are diametrically opposed and which rotate in the same sense as the base flow. Vortex breakdown, Delta wings, Unsteady aerodynamics, Computational fluid dynamics.

Download or read book Prediction of Transonic Vortex Flows Using Linear and Nonlinear Turbulent Eddy Viscosity Models written by Robert E. Bartels and published by . This book was released on 2000 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Threee-dimensional transonic flow over a delta wing is investigated with a focus on the effect of transition and influence of turbulence stress anisotropies. The performance of linear eddy viscosity models and an explicit algebraic stress model is assessed at the start of the vortex flow, and the results compared with experimental data. To assess the effect of transition location, computations that either fix transition or are fully turbulent are performed. To assess the effect of the turbulent stress ansiotropy, comparisons are made between predictions from the algebraic stress model and the linear eddy viscosity models. Both transition location and turbulent stress anisotropy significantly affect the 3D flow field. The most significant effect is found to be the modeling of transition location. At a Mach number of 0.90, the computed solution changes character from steady to unsteady depending on transition onset. Accounting for the anisotropies in the turbulent stresses also considerably impacts the flow, most notably in the outboard region of flow separation.

Download or read book Numerical Investigation Into Vortical Flow about a Delta wing Configuration Up Ti 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 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 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 Fluid Vortices written by Sheldon Green and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 905 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid Vortices is a comprehensive, up-to-date, research-level overview covering all salient flows in which fluid vortices play a significant role. The various chapters have been written by specialists from North America, Europe and Asia, making for unsurpassed depth and breadth of coverage. Topics addressed include fundamental vortex flows (mixing layer vortices, vortex rings, wake vortices, vortex stability, etc.), industrial and environmental vortex flows (aero-propulsion system vortices, vortex-structure interaction, atmospheric vortices, computational methods with vortices, etc.), and multiphase vortex flows (free-surface effects, vortex cavitation, and bubble and particle interactions with vortices). The book can also be recommended as an advanced graduate-level supplementary textbook. The first nine chapters of the book are suitable for a one-term course; chapters 10--19 form the basis for a second one-term course.

Download or read book Aerodynamics written by Theodore Von Kármán and published by Courier Corporation. This book was released on 2004-01-01 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Charming, reader-friendly chronicle by a famous pioneer in aerodynamic research traces the development of dynamic flight from the time of Newton through the 20th century. It recounts struggles of engineers and physicists with problems associated with lift, drag, stability, aeroelasticity, and the sound barrier. 72 figures. 1957 edition.

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 Separated and Vortical Flow in Aircraft Wing Aerodynamics written by Ernst Heinrich Hirschel and published by Springer Nature. This book was released on 2020-10-04 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid mechanical aspects of separated and vortical flow in aircraft wing aerodynamics are treated. The focus is on two wing classes: (1) large aspect-ratio wings and (2) small aspect-ratio delta-type wings. Aerodynamic design issues in general are not dealt with. Discrete numerical simulation methods play a progressively larger role in aircraft design and development. Accordingly, in the introduction to the book the different mathematical models are considered, which underlie the aerodynamic computation methods (panel methods, RANS and scale-resolving methods). Special methods are the Euler methods, which as rather inexpensive methods embrace compressibility effects and also permit to describe lifting-wing flow. The concept of the kinematically active and inactive vorticity content of shear layers gives insight into many flow phenomena, but also, with the second break of symmetry---the first one is due to the Kutta condition---an explanation of lifting-wing flow fields. The prerequisite is an extended definition of separation: “flow-off separation” at sharp trailing edges of class (1) wings and at sharp leading edges of class (2) wings. The vorticity-content concept, with a compatibility condition for flow-off separation at sharp edges, permits to understand the properties of the evolving trailing vortex layer and the resulting pair of trailing vortices of class (1) wings. The concept also shows that Euler methods at sharp delta or strake leading edges of class (2) wings can give reliable results. Three main topics are treated: 1) Basic Principles are considered first: boundary-layer flow, vortex theory, the vorticity content of shear layers, Euler solutions for lifting wings, the Kutta condition in reality and the topology of skin-friction and velocity fields. 2) Unit Problems treat isolated flow phenomena of the two wing classes. Capabilities of panel and Euler methods are investigated. One Unit Problem is the flow past the wing of the NASA Common Research Model. Other Unit Problems concern the lee-side vortex system appearing at the Vortex-Flow Experiment 1 and 2 sharp- and blunt-edged delta configurations, at a delta wing with partly round leading edges, and also at the Blunt Delta Wing at hypersonic speed. 3) Selected Flow Problems of the two wing classes. In short sections practical design problems are discussed. The treatment of flow past fuselages, although desirable, was not possible in the frame of this book.

Download or read book Conical Euler Analysis and Active Roll Suppression for Unsteady Vortical Flows about Rolling Delta Wings written by Elizabeth M. Lee-Rausch and published by . This book was released on 1993 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Prediction of Vortex Breakdown in Leading Edge Vortices Above Slender Delta Wings written by Z. Rusak and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Flow Control of Vortical Structures and Vortex Breakdown Over Slender Delta Wings written by and published by . This book was released on 2003 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Spiral Vortex Breakdown Above a Delta Wing written by Miguel R. Visbal and published by . This book was released on 1995 with total page 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...