39 Result(s)
within
English
Engineering
Acoustics
Automotive Engineering
Classical Mechanics
Mathematical and Computational Engineering
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Chapter and Conference Paper
Measurements of Rotor Tip Vortices Using Laser Doppler Velocimetry
A helicopter rotor wake is dominated by strong vortices that form at each blade tip, e.g. Refs. [1]–[8]. When the helicopter is descending or maneuvering, the blades may closely intersect the tip vortices resu...
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Chapter and Conference Paper
Asymptotic Theory of Slender Vortex Filaments — Old and New
We give a brief review of the asymptotic theory of slender vortex filaments to emphasize i) the choices of scalings, small parameters and the distinguished limit, ii) the consistency conditions, iii) the optim...
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Chapter and Conference Paper
Numerical Simulation of Nonlinear Interactions in Subsonic and Supersonic Free Shear Layers
A free shear layer (or a mixing layer) is a flow formed by mixing of two parallel flows of fluid moving with different velocities. The mechanisms leading to its instability and transition to turbulence play al...
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Chapter and Conference Paper
Recent Development in the Asymptotic Theory of Vortex Breakdown
Slender vortex dynamics is dominated by two very different sources of nonlinearity. There is first the nonlinearity inherent in the motion of a vortex filament due to nonlocal self-induction and local curvatur...
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Chapter and Conference Paper
Dynamics of Slender Vortices Near the Wall in a Turbulent Boundary Layer
It is now well-established that the enhanced drag and heat transfer of turbulent boundary layers are dominated by slender longitudinal vortices near the wall. Despite their immense practical significance, the ...
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Chapter and Conference Paper
Self-Induced Motion of Helical Vortices
The self-induced velocity of helical vortices in an infinite space as well as in a cylindrical tube is studied. Investigation was based on an analysis of the formula for determination of the self-induced veloc...
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Chapter and Conference Paper
Genesis of Longitudinal Vortices in Near-Wall Turbulence
Using direct numerical simulations of turbulent channel flow, we present new insight into the formation mechanism of near-wall longitudinal vortices. Instability of lifted, vortex-free low-speed streaks is sho...
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Chapter and Conference Paper
Optimized Vortex Element Schemes for Slender Vortex Simulations
Vortex element schemes are designed for application to flows with highly concentrated vorticity. These schemes are based on discretization of the vorticity field into spherically smoothed Lagrangian elements o...
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Chapter and Conference Paper
Interaction of Two Vortex Tubes and the Singularity Formation
Are there any three-dimensional velocity field of inviscid fluid with finite energy such that the velocity field becomes singular within a finite time T? This is a challenging problem in the mathematical theor...
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Chapter and Conference Paper
The Influence of the Swirl Velocity Ratio on the Nature of the Dominant Helical Structures in a Swirling Jet Model
The nonlinear evolution of helical perturbations is investigated in a swirling jet model, consisting of a line vortex along the jet centerline surrounded by a jet shear layer with both azimuthal and streamwise...
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Chapter and Conference Paper
Simulation of Vortex Ring Interaction
A numerical solution of the Navier-Stokes equations for incompressible flows is used to simulate the interaction of isolated vortex rings in unbounded domains. The algorithm is based on a pressure correction s...
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Chapter and Conference Paper
Long-Wavelength Instability and Reconnection of a Vortex Pair
The dynamics of a pair of parallel counter-rotating vortices has been the object of a large number of studies in the last three decades. The continued interest in this flow is, to a great extent, due to its re...
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Chapter and Conference Paper
Instabilities and Vortex Breakdown in Swirling Jets and Wakes
The convective/absolute nature of the instability is determined for two distinct families of swirling wake/jet flows: the Batchelor vortex with external axial flow and the Rankine vortex with plug-flow velocit...
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Chapter and Conference Paper
Vortex Breakdown as a Catastrophe
By studying swirling viscous jets, we develop a new explanation of vortex breakdown, show how solution non-uniqueness appears through cusp and fold catastrophes as the Reynolds number Re increases, and obtain ana...
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Chapter and Conference Paper
Breakdown of Spinning Tube Flows
Breakdown of the turbulent flow in a spinning tube with a diffuser at the end was studied by flow visualization and Digital Particle-Image-Velocimetry (DPIV). The swirl of the flow was introduced at the entran...
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Chapter and Conference Paper
Noise Emission Due to Slender Vortex Solid Body Interactions
Interactions of a slender vortex ring with and a stationary rigid sphere are analyzed using a 3D, Lagrangian vortex element scheme which discretizes and tracks the filament centerline using smoothed vortex ele...
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Chapter and Conference Paper
Sound Generation by Interactions of Two Vortex Rings
Vortex sound from collision of two vortex rings at 16 different angles between head-on and perpendicular collisions is numerically analyzed using an aerodynamic sound theory for the far-field acoustic pressure...
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Chapter and Conference Paper
Vortex Dynamics in Nonuniform Compressible Flow
The convection of vortices in convergent nozzles and Laval nozzles is investigated experimentally and numerically. All studies are done for the plane case. The experiments are performed in a transonic wind tun...
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Chapter and Conference Paper
Interaction of Wing Vortices and Plumes in Supersonic Flight
A model of the wake of an aircraft cruising at high speed in the stratosphere is presented. The two major components of the flow field are the trailing vortex wake and the jet exhaust plumes. The prospect of l...
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Chapter and Conference Paper
Modifications of the Tip Vortex Structure from a Hovering Rotor Using Spoilers
Numerical studies of the tip vortex structure from a hovering rotor with and without various spoilers are presented. A general multizone unsteady three-dimensional Navier-Stokes solver is developed to determin...
