Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Inviscid Numerical Simulations Of 2d Parallel Blade Vortex Interaction PDF full book. Access full book title Inviscid Numerical Simulations Of 2d Parallel Blade Vortex Interaction.
| Author | : Y. Tanabe |
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| Total Pages | : 17 |
| Release | : 2007 |
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| Author | : |
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| Total Pages | : 17 |
| Release | : 2007 |
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| Author | : Henry E. Jones |
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| Total Pages | : 96 |
| Release | : 1997 |
| Genre | : Unsteady flow (Aerodynamics) |
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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 | : Erkan Yildirim |
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| Release | : 2012 |
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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 | : Amer Hussain Sheikh |
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| Total Pages | : |
| Release | : 2002 |
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| Author | : Amer Hussain Sheikh |
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| Release | : 2002 |
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| Author | : G. R. Srinivasan |
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| Total Pages | : 20 |
| Release | : 1985 |
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A computational procedure and some numerical results of unsteady interaction of a helicopter rotor blade with a Lamb-like vortex of finite viscous core in subsonic and transonic flows is presented. The interaction considered here is one of the limiting cases of a more complex interaction typically encountered on helicopter rotor blade. In this limit, the interacting flow field is considered to be unsteady but two-dimensional. Accordingly, unsteady, two-dimensional, thin-layer Navier-Stokes equations are solved using a prescribed-vortex method (also called perturbation method) for the cases of stationary and moving rotor blades encountering a moving vortex passing the blades. The numerical results are compared with the recent experimental data of Caradonna et al. for the latter case. The comparison shows that for the transonic cases, the flow field is dominated by the presence of the shock waves, with strong indications of unsteady time lags in the shock-wave motions and shock-wave strengths, and of important three-dimensional effects. For subcritical-flow cases, however, the unsteady lag effects on the basic rotor blade are absent, and three-dimensional effects appear to be negligible, unlike the supercritical case. The subcritical calculations are in good agreement with the experimental data.
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| Total Pages | : 18 |
| Release | : 1990 |
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When a vortex-dominated flow interacts with a sharp density interface, the dynamics are characterized by the interaction of baroclinically generated vorticity with the already existing vorticity field. This can be seen in many natural and technology settings; examples are the interaction of a ship or submarine wake with a thermocline, the collision of a buoyant thermal with a temperature inversion, and the interaction of a vortex flow with a flame front. This problem also serves as a generic model for turbulent mixing and entrainment processes across sharp density interfaces. The interaction between vortices and a free surface, with corresponds to the case where the density jump is very large, has been studied fairly extensively, both experimentally and computationally. By comparison, the literature for the more general case of vortex pairs and rings interacting with sharp density interfaces is relatively sparse. Experiments and numerical studies have been performed, but the numerical simulations were confined primarily to vortex pairs, restricted to the inviscid case, and the effect of density variation modeled under the Boussinesq approximation. The experiments were also confined to the Boussinesq regime. In this paper, we study the motion of a vortex ring in a sharply stratified, viscous fluid via a numerical solution of the full Navier-Stokes equations with finite-amplitude density variation. both Boussinesq and non-Boussinesq flow regimes will be studied, the effect of viscosity on the interaction will be examined, and three-dimensional aspects of the motion will be addressed, such as Widnall instability of the vortex ring and vortex reconnection at the interface.
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| Total Pages | : 40 |
| Release | : 1984 |
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| Author | : Laura Katherine Brandt |
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| Total Pages | : 180 |
| Release | : 2009 |
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This work investigates fundamental two-dimensional vortex pair dynamics in unstratified and stably stratified environments through numerical and analytical techniques. The study focuses on two main topics: (i) vortex interaction and merging of co-rotating vortex pairs and (ii) internal wave generation by co-rotating and counter-rotating vortex pairs. Two-dimensional vortex merging in a viscous fluid is studied using numerical simulations. Analysis of the ideal case of two equal co-rotating vortices (symmetric pair) identifies the basic underlying physics of vortex merger. Through the interaction of the vorticity gradient and the mutually induced strain rate near the central hyperbolic point, a tilt in vorticity contours is established. This leads to core detrainment and the entrainment of core fluid into the exchange band, which transforms the flow into a single vortex. In the case of the asymmetric (unequal strength) vortex pair, the disparity in the deformation rates between the vortices alters the interaction. A critical value for a strain rate parameter characterizing the establishment of core detrainment is determined. The onset of merging is associated with the achievement of the critical strain by both vortices and a generalized merging criterion is formulated. A classification scheme of the various viscous vortex interactions is developed. Results for the symmetric, horizontally oriented vortex pair in a weakly stratified fluid provide further insight on vortex merging. The effects of weak stratification depend on the ratio of the diffusive time scale to the turnover time, i.e., the Reynolds number. A crossover Reynolds number is found, above which convective merging is accelerated with respect to unstratified flow and below which it is delayed. The generation of internal waves by {\it horizontally} orientated co-rotating and counter-rotating vortex pairs is studied. Linearized inviscid equations are derived that describe the internal wave, vorticity and energy fields. These solutions are compared with nonlinear numerical viscous simulations in moderately and strongly stratified environments. Through evaluation of the energy field, the time at which the flow reaches a steady state for strongly stratified flows is found, along with a characterization of the regimes of strongly and moderately stratified environments.
