Download or read book Computational Study of Vortex Shedding about Slender Bodies written by Scott M. Murman and published by . This book was released on 1999 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theoretical Study of Vortex Shedding from Bodies of Revolution Undergoing Coning Motion written by Gary D. Kuhn and published by . This book was released on 1969 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report investigates a flow model for vortex shedding from slender body in coning motion.
Download or read book Computational Modelling of Bifurcations and Instabilities in Fluid Dynamics written by Alexander Gelfgat and published by Springer. This book was released on 2018-07-06 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt: Instabilities of fluid flows and the associated transitions between different possible flow states provide a fascinating set of problems that have attracted researchers for over a hundred years. This book addresses state-of-the-art developments in numerical techniques for computational modelling of fluid instabilities and related bifurcation structures, as well as providing comprehensive reviews of recently solved challenging problems in the field.
Download or read book The Turbulent Wake of Slender Bodies and the Effects of Density Stratification written by Jose Luis Ortiz Tarin and published by . This book was released on 2021 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since slender bodies have low drag coefficients, they are widely used in naval applications. As they move in the ocean, submersibles leave a trail of turbulence and waves that can persist for a long time in the water. Studying these wakes is challenging as it entails resolving a high-speed flow past a long body, and measuring weak fluctuations in large domains during prolonged times. This thesis is devoted to the computational study of these slender-body wakes. The slender-body wake is thin, slowly-developing and, at high Reynolds numbers, does not exhibit strong vortex shedding. In this work, these particularities are shown to affect the decay of the far wake and the results call into question the notion of universality--the idea that, far from the body, the turbulent flow 'forgets' its initial conditions. In a stratified environment like the ocean, buoyancy effects play a fundamental role in the wake evolution. Buoyancy enhances the mean lifetime of the wake, enables the radiation of internal gravity waves, and triggers the appearance of coherent structures. Understanding these processes is relevant not only to naval applications but also to other problems like the influence of topography in climate models and the navigation of sea animals. Here, highly resolved large-eddy simulations are used to study neutral and stratified slender-body wakes. First, the influence of stratification in the near wake of a prolate spheroid is described. Particular attention is given to the generation of lee waves and the role they play in flow separation. Then, a hybrid method that combines a body-inclusive and a body-exclusive simulation is adopted to enable the first high-Reynolds slender-body far wake study. Contrary to what previous experiments had suggested, the flow in a neutral environment does not conform with classical theory and the dominance of a large-scale helical structure alters the scaling of turbulent dissipation. Finally, comparison with a bluff-body wake reveals that the onset of buoyancy effects depends strongly on the features of the wake generator. This suggests that a parametrization based on local non-dimensional numbers might be necessary to predict the transition between different stratified wake regimes.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1572 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Three dimensional Vortex body Interaction in a Viscous Fluid written by Jeffrey S. Marshall and published by . This book was released on 1999 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental and computational study of the impact of a vortex with a body oriented normal to the vortex axis was performed. Particular focus was placed on understanding characteristics of the secondary vorticity ejected from the body and the interaction of the secondary vorticity with the primary vortex. Since both onset of boundary layer separation and the form of the secondary vorticity structures are sensitive to variation of the velocity normal to the body axis, the effect of normal velocity on vortex-body interaction was carefully examined. The physical features of the flow evolution were categorized in terms of an impact parameter and a thickness parameter, which respectively represent ratios of velocity and length scales associated with the vortex to those associated with the flow in the absence of the vortex. Experiments were performed using a combination of laser-induced fluorescence (LIF) flow visualization and particle-image velocimetry (PIV) in a water tank to examine the form of the secondary vorticity structures with both "high" and "low" values of the impact parameter for normal vortex interaction with a circular cylinder and with a thin blade. A new type of Lagrangian vorticity method based on a tetrahedral mesh was developed and applied to compute the secondary vorticity evolution during vortex-cylinder interaction. Computations were also performed for model problems to examine in detail wrapping of a vortex loop around a columnar vortex and impulsive cutting of a columnar vortex with finite axial flow.
Download or read book Geometric Perturbations and Asymmetric Vortex Shedding about Slender Pointed Bodies written by Scott M. Murman and published by BiblioGov. This book was released on 2013-08 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flow about slender, pointed bodies can be characterized by different states with angle of attack. At moderate-to-high angles of attack (alpha approx. = 40 deg.), a steady, asymmetric vortex pattern develops along the body, leading to a net lateral force. At higher angles of attack (alpha approx. = 60 deg.), the aft-end of the body develops an unsteady von Karman shedding. As the angle of attack approaches 90 deg., the entire body length exhibits a time-dependent vortex shedding pattern. The current work uses three-dimensional, thin-layer Navier-Stokes simulations to investigate the physical mechanisms of asymmetric vortex shedding at alpha = 40 deg. and alpha = 60 deg. The development of an asymmetric vortex pattern via a convective instability mechanism is investigated using tip bumps, surface roughness, and tip curvature. It's found that surface roughness simulations can incite an asymmetric vortex state at alpha = 60 deg. which is consistent with the application of a tip bump, and the experimentally observed flowfield. The unsteady von Karman vortex shedding on the aft. portion of the body is also well resolved. The use of surface roughness did not incite a flow asymmetry at alpha = 40 deg., and it was necessary to simulate tip curvature at this angle of attack in order to generate an asymmetric vortex state.
Download or read book NASA SP written by and published by . This book was released on 1993 with total page 590 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1989 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fluid Structure Interaction V written by C. A. Brebbia and published by WIT Press. This book was released on 2009 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt: Encompassing a wide range of topics within fluid structure interaction, this volume features contributions on topics such as hydrodynamic forces, offshore structure and ship dynamics, structure response to severe shock and blast loading, and the mechanics of cables, risers and moorings.
Download or read book NASA Tech Briefs written by and published by . This book was released on 1992-05 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Control and Suppression of Laminar Vortex Shedding Off Two dimensional Bluff Bodies written by Andre Sirilutporn Chan and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The focus of this research is on the control and suppression of vortex shedding of flow past bluff bodies. The motivation of this research stems from the aerodynamic problems encountered in the design and development of hard disk drives (HDD's). Two different computational fluid dynamic methods have been used in this research-- the Semi-Implicit Method for Pressure Linked Equation (SIMPLE), that is widely employed in today's commercial incompressible flow solvers, and the high-order spectral difference (SD) method, recently developed for compressible flow solution. In addition to numerical simulation and verification, complementary experimental measurements have been performed to further validate the results. This research leads to two very different suppression techniques: 1) a passive control using a thin splitter plate positioned downstream of the bluff body; 2) an active control by way of counter rotating a cylinder pair. The passive suppression technique places a thin splitter plate downstream of the bluff body in order to interfere with the vortex wakes and thereby suppress the vortexinduced forces on the bluff body itself. The present investigation examines the suppression of wake instabilities in the laminar shedding regime. Both bounded and unbounded flow conditions are examined. It is found that in the bounded flow condition, the channel walls have an additional stabilizing effect on the shedding control. With proper positioning of the splitter plate, vortex shedding is completely suppressed in a bounded flow with moderate blockage factor. Wind tunnel empirical experiments have also confirmed the effectiveness of a splitter plate in a bounded flow. Active flow control by counter-rotating a pair of cylinders has been numerically investigated. It has also been investigated experimentally in partnership with the Gas Dynamics Laboratory at Princeton University. It is demonstrated that it is possible to suppress unsteady vortex shedding for gap sizes from one to five cylinder diameters, at Reynolds numbers from 100 to 200. The degree of unsteady wake suppression is proportional to the speed and the direction of rotation, and there is a critical rotation rate where a complete suppression of flow unsteadiness can be achieved. In the doublet-like configuration at higher rotational speeds, a virtual elliptic body that resembles a potential doublet is formed, and the drag is reduced to zero. The shape of the elliptic body primarily depends on the gap between the two cylinders and the speed of rotation. Prior to the formation of the elliptic body, a second instability region is observed, similar to that seen in studies of rotating single cylinders. It is also shown that the unsteady wake suppression can be achieved by rotating each cylinder in the opposite direction, that is, in a reverse doublet-like configuration. This tends to minimize the wake interaction of the cylinder pair and the second instability did not make an appearance over the range of speeds investigated here.
Download or read book Aeronautical Engineering written by and published by . This book was released on 1991 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Research and Technology 1989 written by and published by . This book was released on 1990 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Crosswind stability of vehicles under nonstationary wind excitation written by Zhang, Xiaoyu and published by KIT Scientific Publishing. This book was released on 2015-05-13 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work has studied the crosswind stability of vehicles under nonstationary wind excitation in various scenarios. Railway vehicles running on curved and straight track with varying vehicle speed are studied. Road vehicles are classified into different categories. For each vehicle class, a corresponding worst-case vehicle model has been built. As the wind excitation on the vehicle is a stochastic process, a risk analysis has to be carried out and failure probabilities are computed and analyzed.
Download or read book An Evaluation of Vortex Shedding Over Slender Structures Using Large eddy Simulation written by Steven J. Daniels and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
