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Author : Piergiovanni Renzoni
Publisher :
ISBN 13 :
Total Pages : 252 pages
Book Rating : 4.:/5 (115 download)
Download or read book Discrete Vortex Modeling of a Blade-vortex Interaction written by Piergiovanni Renzoni and published by . This book was released on 1987 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Henry E. Jones
Publisher :
ISBN 13 :
Total Pages : 96 pages
Book Rating : 4.:/5 (317 download)
Download or read book Full-Potential Modeling of Blade-Vortex Interactions written by Henry E. Jones and published by . This book was released on 1997 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study of the full-potential modeling of a blade-vortex interaction was made. A primary goal of this study was to investigate the effectiveness of the various methods of modeling the vortex. The model problem restricts the interaction to that of an infinite wing with an infinite line vortex moving parallel to its leading edge. This problem provides a convenient testing ground for the various methods of modeling the vortex while retaining the essential physics of the full three-dimensional interaction. A full-potential algorithm specifically tailored to solve the blade-vortex interaction (BVI) was developed to solve this problem. The basic algorithm was modified to include the effect of a vortex passing near the airfoil. Four different methods of modeling the vortex were used: (1) the angle-of-attack methods, (2) the lifting-surface method, (3) the branch-cut method, and (4) the split-potential method. A side-by-side comparison of the four models was conducted. these comparisons included comparing generated velocity fields, a subcritical interaction, and a critical interaction. The subcritical and critical interactions are compared with experimentally generate results. The split-potential model was used to make a survey of some of the more critical parameters which affect the BVI.
Author :
Publisher :
ISBN 13 :
Total Pages : 18 pages
Book Rating : 4.:/5 (227 download)
Download or read book The Effects of Vortex Modeling on Blade-Vortex Interaction Noise Prediction written by and published by . This book was released on 1995 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of a blade vortex interaction noise prediction scheme, based on CAMRAD/JA, FPR and RAPP, quantifies the effects of errors and assumptions in the modeling of the helicopter's shed vortex on the acoustic predictions. CAMRAD/JA computes the wake geometry and inflow angles that are used in FPR to solve for the aerodynamic surface pressures. RAPP uses these surface pressures to predict the acoustic pressure. Both CAMRAD/JA and FPR utilize the Biot-Savart Law to determine the influence of the vortical velocities on the blade loading and both codes use an algebraic vortex model for the solid body rotation of the vortex core. Large changes in the specification of the vortex core size do not change the inplane wake geometry calculated by CAMRAD/JA and only slighty affect the out-of-plane wake geometry. However, the aerodynamic surface pressure calculated by FPR changes in both magnitude and character with small changes to the core size used by the FPR calculations. This in turn affects the acoustic predictions. Shifting the CAMRAD/JA wake geometry away from the rotor plane by 1/4 chord produces drastic changes in the acoustic predictions indicating that the prediction of acoustic pressure is extremely sensitive to the miss distance between the vortex and the blade and that this distance must be calulated as accurately as possible for acceptable noise predictions. The inclusion or exclusion of a vortex in the FPR-RAPP calculation allows for the determination of the relative importance of that vortex as a BVI noise source. (AN).
Author : Earl R. Booth
Publisher :
ISBN 13 :
Total Pages : 32 pages
Book Rating : 4.:/5 (31 download)
Download or read book New Technique for Experimental Generation of Two-dimensional Blade-vortex Interaction at Low Reynolds Numbers written by Earl R. Booth and published by . This book was released on 1986 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 32 pages
Book Rating : 4.:/5 (317 download)
Download or read book New Techniques for Experimental Generation of Two-dimensional Blade-vortex Interaction at Low Reynolds Numbers written by and published by . This book was released on 1986 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Zambri Harun
Publisher : BoD – Books on Demand
ISBN 13 : 183962616X
Total Pages : 236 pages
Book Rating : 4.8/5 (396 download)
Download or read book Vortex Dynamics Theories and Applications written by Zambri Harun and published by BoD – Books on Demand. This book was released on 2020-12-09 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book comprises of different areas in which vortex dynamics is important, its generation, evolution, interactions with other motions, and finally the ways it can be controlled. Vortex characteristics are important in many aspects of our lives, from blood circulation in the arteries to the high-speed jet. Flow control and manipulation of vortices have been used to reduce drag for large tankers resulting in billions of dollars in savings. An effective smoke management system must be put in place for critical areas to ensure the safety of people, for example in a very large shopping complex or a large airport. Advanced computational and cloud-computing facilities have contributed significantly to large-scale simulation projects. Therefore, validations could be performed for larger windows of study so that it can now cover the entire e.g. central business district (CBD) for urban heat island (UHI) study or land-ocean interactions.
Author : Michael Rex Maixner
Publisher :
ISBN 13 :
Total Pages : 278 pages
Book Rating : 4.:/5 (64 download)
Download or read book Vortex Element Analysis of Selected Time-dependent Flows written by Michael Rex Maixner and published by . This book was released on 1994 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previous investigations of oscillating (harmonic) flow past circular cylinders via the discrete vortex method have met with limited success due to a variety of reasons. These assumptions have proven to be too severe, and cannot allow the prediction of the kinematics and dynamics of the oscillating flow about bluff bodies in general and about a circular cylinder in particular. In the current analysis, the ambient velocity was given by U = Um sin wt, and the velocity distribution and the boundary layer were calculated about the cylinder at suitable time intervals. Several methods were implemented to predict separation, all of which required a minimum of arbitrary assumptions. Nascent vortices were placed at the separation points in such a manner that the Kutta condition was satisfied. Several functional forms of dissipation were investigated, but it was found not to be of overriding influence in the flow kinematics. Counter vortices were found to be a necessary aspect of the analysis, providing continuity from one half cycle to the next. Flow visualization experiments were conducted for a Keulegan-Carpenter number of 10 as a basis for comparison. The kinematics obtained from the numerical model produced a vortex shedding pattern which was typical of those observed experimentally for higher Keulegan-Carpenter numbers. Significant problems were encountered in the prediction of boundary layer separation. At this point, it was obvious that the interaction of a vortex with a boundary layer warranted analysis in a much simpler flow situation; the blade-vortex interaction (BVI) problem proved to be ideal.
Author :
Publisher :
ISBN 13 :
Total Pages : 38 pages
Book Rating : 4.:/5 (317 download)
Download or read book Finite Difference Modeling of Rotor Flows Including Wake Effects written by and published by . This book was released on 1982 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper gives a brief consideration of rotary wing finite difference methods. The main concern is the specification of boundary conditions to properly account for the effect of the wake on the blade. Examples are given of an approach where wake effects are introduced by specifying an equivalent angle of attack. An alternate approach is also given where discrete vortices are introduced into the finite difference grid. The resulting computations of hovering and high advance-ratio cases compare well with experiment. Some consideration is also given to the modeling of low-to-moderate advance-ratio flows. (Author).
Author : Amer Hussain Sheikh
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (99 download)
Download or read book The numerical simulation of blade-vortex interaction written by Amer Hussain Sheikh and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Amer Hussain Sheikh
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (591 download)
Download or read book The Numerical Simulation of Compressible Blade Vortex Interaction written by Amer Hussain Sheikh and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 28 pages
Book Rating : 4.:/5 (317 download)
Download or read book Prediction of Blade-vortex Interaction Noise from Measured Blade Pressure written by and published by . This book was released on 1981 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 40 pages
Book Rating : 4.:/5 (317 download)
Download or read book An Experimental Investigation of the Parallel Blade-vortex Interaction written by and published by . This book was released on 1984 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Erkan Yildirim
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (847 download)
Download or read book Computational Study of High Speed Blade-vortex Interaction written by Erkan Yildirim and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents inviscid compressible simulations for the orthogonal blade-vortex interaction. A numerical model between the tail rotor of a helicopter and the trailing vortex system formed by the main rotor blades is assumed. The study takes a 'building-block' approach to investigating this problem. Firstly, the impulsive instantaneous blocking of the axial core flow by a flat plate is considered. In the second step, the three-dimensional gradual cutting of the vortex by a sharp flat-plate that moves at a finite speed through the vortex is performed. Finally the chopping of the vortex by a blunt leading edge aerofoil, which incorporates both the blocking effect and also the stretching and distortion of the vortex lines is studied. The solutions reveal that the compressibility effects are strong when the axial core flow of the vortex is impulsively blocked. This generates a weak shock-expansion structure propagating along the vortex core on opposite sides of the cutting surface. The shock and expansion waves are identified as the prominent acoustic signatures in the interaction. In a simplified, two-dimensional axisymmetric model, the modelling of the physical evolution of the vortex, including the evolution of the complex vortical structures that controls the vortex core size near the cutting surface, are studied. Furthermore, the three dimensional simulations revealed that there is a secondary and a tertiary noise sources due to compressibility effects at the blade leading edge and due to the shock-vortex interaction taking place on the blade, which is exposed to a transonic free-stream flow.
Author : F. N. Coton
Publisher :
ISBN 13 :
Total Pages : 19 pages
Book Rating : 4.:/5 (11 download)
Download or read book A Three-dimensional Model of Low-speed Blade-vortex Interaction written by F. N. Coton and published by . This book was released on 1994 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Daniel Bershader
Publisher :
ISBN 13 :
Total Pages : 191 pages
Book Rating : 4.:/5 (227 download)
Download or read book Foundations of the Blade-Vortex Interaction Problem: Structure and Behavior of Travelling Compressible Vortices written by Daniel Bershader and published by . This book was released on 1988 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure of a compressible free vortex has been analyzed while undergoing convection in a quasi-uniform stream flow. Holographic interferograms several reveal radial density profiles of the vortex at different stages of its development during convection. A general mathematical expression is found which closely describes the distribution of density inside the vortex. By use of experimental data and the governing equations in an empirical/theoretical analysis, an extended physical description of the vortex is developed. The time behavior of the density, determined from the experiments, allows the solution of the Continuity Equation and a distribution of the radial component of fluid velocity relative to the vortex center is obtained. The density information, supplemented by an independent determination of pressure is the used in the Radial Momentum Equation to obtain a distribution of the circumferential component of fluid velocity relative to the vortex center, thus completing the description of the radial dependence of the velocities inside the vortex. Furthermore, the calculated velocities are used to evaluate the magnitudes of the convective and diffusive terms of the Angular Momentum Equation, thus providing insight into the question of the relative effects of compressibility and viscosity on the internal structure and behavior of the vortex in terms of the distribution and transport of angular momentum. Keywords: Blade vortex interaction, Rotary wing flight, Rotor wake, Compressible free vortex. (aw).
Author : Kyoji Kamemoto
Publisher : World Scientific
ISBN 13 : 9814493287
Total Pages : 228 pages
Book Rating : 4.8/5 (144 download)
Download or read book Vortex Methods: Selected Papers Of The First International Conference On Vortex Methods written by Kyoji Kamemoto and published by World Scientific. This book was released on 2000-05-11 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vortex methods have been developed and applied to many kinds of flows related to various problems in wide engineering and scientific fields. The purpose of the First International conference on Vortex methods was to provide an opportunity for engineers and scientists to present their achievements, exchange ideas and discuss new developments in mathematical and physical modeling techniques and engineering applications of vortex methods.
Author : Metin O. Kaya
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (85 download)
Download or read book Discrete Vortex Method Simulation of Karman Street-edge Interaction written by Metin O. Kaya and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of the present investigation is to characterize, for the first time, theintantaneous flow field Karman street-leading edge interactions, including unsteady edge surface pressure distributions. Discrete Vortex Method (DVM) Computational Fluid Dynamics (CFD) system was adapted and supported by a numerical Schwarz Christoffel transformation. Results were presented for different leading edge geometries including the elliptical edge configuration which was used as a basis to discuss the efectiveness and accuracy of the algorithm. A viscous flow past a sharp leading edge results in unsteady vortex shedding. The vorticity field composes the well known Karman Vortex Street. Alternating row vortices have a characteristic frequency of shedding. In agreement with the experimental test data, the nondimensional frequency of shedding was found to be 0.15 in this work. The accuracy of the method was tested by calculating tlıe mean and fluctuating velocity field on a fixed grid system superposed onto the flow. Both the crossstream profiles and the peak values confirm laboratory observation. Impingement of the Karman Street upon a leading edge causes vorticity field deformation in the neighborhood of the edge. This deformation occurs under the strain field effect of the edges. Vortex-street elliptical edge interaction causes splitting of the incident row vorticity field into two portions. The split vorticity field of alternating sign then merges and convects over the edge surface. Unsteady pressure fields exhibit three distinct regions of special character. Disturbance induced pressure fields were found to be suction type regardless of the sense of rotation of the vortex structures. The present investigation introduces a new model of vortex-sharp edge in teractions including secondary vortex formation. As the vortex approches the edge, due to high induced cross flow magnitudes near the tip, flow separates and a new vortex forms with opposite sense of rotation. The complex nature of secondary vortex shedding was modelled as a truelly self generating phenomena. The transient nature of the induced pressure field near the tip confirm the secondary vortex formation near the tip. Integration of the surface pressure field over the leading edge surface of every instant of Karman street-edge interaction yields instantaneous loading on the edge. It is observed that the direction of the induced force is a direct function of the approaching vorticity field. Thus, clockwise rotating upper row vortex induces force in the direction of rotation and vice versa for the lower row vortex edge interaction.
