Vortex/body interaction and sound generation in low-speed flow

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National Aeronautics and Space Administration, Lewis Research Center, National Technical Information Service, distributor , [Cleveland, Ohio], [Springfield, Va
Vortices., Sound generators., Background n
Other titlesVortex body interaction and sound generation in low-speed flow.
StatementHsiao C. Kao.
SeriesNASA/TM -- 1998-208403., NASA technical memorandum -- 208403.
ContributionsLewis Research Center.
The Physical Object
FormatMicroform
Pagination1 v.
ID Numbers
Open LibraryOL15560470M

Vortex/body interaction and sound generation in low-speed flow (OCoLC) Online version: Kao, H.C. (Hsiao C.). Vortex/body interaction and sound generation in low-speed flow (OCoLC) Material Type: Government publication, National government publication: Document Type: Book: All Authors / Contributors: Hsiao C Kao; Lewis Research.

Vortex/body interaction and sound generation in low-speed flow (OCoLC) Microfiche version: Kao, Hsiao C. Vortex/body interaction and sound generation in low-speed flow (OCoLC) Material Type: Document, Government publication, National government publication, Internet resource: Document Type: Internet Resource, Computer File.

Vortex/Body Interaction and Sound Generation in Low-Speed Flow. By Hsiao C. Kao. Abstract. The problem of sound generation by vortices interacting with an arbitrary body in a low-speed flow has been investigated by the method of matched asymptotic expansions. For the purpose of this report, it is convenient to divide the problem into three : Hsiao C.

Kao. Vortex/Body Interaction and Sound Generation in Low-Speed Flow The problem of sound generation by vortices interacting with an arbitrary body in a low-speed flow has been investigated by the method of matched asymptotic expansions.

For the purpose of this report, it is convenient to divide the problem into three parts. In numerical simulation of sound generation caused by vortex–body interaction, the vortex core R c has typically been assumed to be the characteristic length scale.

However, another length scale can be formed using the total circulation of the vortex, Γ=∫Ω d A (where Ω is the vorticity in the 2-D flow and the integration is performed Cited by: 6. Interaction of a vortex, or combinations of them, with a cylinder, blade, or foil may involve both rapid distortion of the incident vorticity field and shedding of vorticity from the surface of the body.

This review focuses on the underlying flow physics, with the aim of clarifying the origin of the induced loading. In the case of near or direct encounter of the incident vortex, the relation. The interaction of vortex with a solid body is of importance in the study of flow-induced vibration and sound generation.

The case whereby a body follows in the wake of another is of.

Description Vortex/body interaction and sound generation in low-speed flow EPUB

Vortex-body interaction The presented theory can also be generalized to account for effects of compact bodies within the hydrodynamic flow region on aerodynamic sound generation (Obermeier ). For that purpose we start with the integral representation eq. (8) where, however, the ordinary free field Green's function has to be replaced by one.

Body-Vortex Interaction, Sound Generation, and Destructive Interference. Hsiao C. Kao ; Effects of reynolds stress on flow noise from vortex/hydrofoil interactions. Journal of Vortex/body interaction and sound generation in low-speed flow book, Ser.

B, Vol. 18, No. 3 Sound generation by rotor-vortex interaction in low Mach number flow. Impulse Theory of Vortex Sound Problems 5 6 Vortex–Surface Interaction Noise in Two Dimensions Compact Green’s Function in Two Dimensions Sound Generated by a Line Vortex Interacting with a Cylindrical Body Influence of Vortex Shedding Blade–Vortex Interaction Noise in Two Dimensions   This site uses cookies.

By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy. The accelerations and decelerations of the vortex filament are shown to be the major mechanisms of sound generation.

The sound so produced has a large low-frequency content such that the change in the flow impedance affects only the sound generation process but not the subsequent sound propagation to the far field.

The acoustic field induced by an unsteady vortical flow is analyzed.

Details Vortex/body interaction and sound generation in low-speed flow PDF

In particular, the limit where the reference length scale l of the vortical flow is much smaller than the reference length scale of the acoustic field is considered. At low Mach number M the leading-order solution of the vortical flow is an incompressible viscous flow.

The far field behavior of the flow is matched to the five. The solutions show that as the turbulence intensity increases, the sound radiated by the vortex–body interaction is strengthened while the effect of the mean flow speed on the sound waves weakens.

the mechanism of sound generation in the interaction between a shock wave and a single planar vortex [14], a pair of planar vortices [15, 16] or a longitudinal vortex [17] through direct numerical simulation (DNS) for the two and three dimensional unsteady compressible.

Sound generation by interaction of two inviscid two-dimensional vortices The Journal of the Acoustical Society of America, Vol.No. 3 Upwind Scheme for Acoustic Disturbances Generated by Low-Speed. A study of the interaction between an initially columnar intake vortex (hereinafter referred to as the primary vortex) and vortex structures in the wake of a single sphere (hereinafter referred to as secondary vortices) is performed using a series of flow visualization experiments, in which a sphere is towed toward a stationary vortex with ambient axial flow and gradually decelerated to rest.

Sound generated by the pairing of two coaxial vortex rings in the presence of a background axisymmetric potential flow was studied numerically. Results show that the background flow substantially affects the sound generation process in the beginning of the vortex ring interaction.

Presentation Notes: This figure is a plot showing the Strouhal number (St, St=Dfvs/U) versus the Reynolds number (Re, Re=UD/ν).The variation of St with Re is discussed so that the audience has an understanding of what flow features. influence St, i.e., the vortex shedding frequency, and.

Compressibility of the background mean flow and the vortex are taken into account and its effect on amplification of acoustic pressure is discussed. Generation of sound by stretching of vorticity dipole leads to formation of a three-spot wave with maximum acoustic pressure at the centerline.

Michael S. Howe, Lectures on the Theory of Vortex-Sound, Sound-Flow Interactions, /_2, (), (). Crossref Andreas Meister, Jens Struckmeier, Andreas Meister, Jens Struckmeier, Computational Fluid Dynamics and Aeroacoustics for Low Mach Number Flow, Hyperbolic Partial Differential Equations, / This flow phenomenon moves relative to the rotor blades and causes periodic vortex separations at the blade tips and an axial reversed flow through the tip clearance of the rotor blades.

The paper describes experimental investigations of RIs in the Dresden Low-Speed Research Compressor (LSRC). VORTEX-BODY INTERACTIONS VORTEX-BODY INTERACTIONS Rockwell, Donald Abstract Interaction of a vortex, or combinations of them, with a cylinder, blade, or foil may involve both rapid distortion of the incident vorticity field and shedding of vorticity from the surface of the body.

This review focuses on the underlying flow physics, with the aim of clarifying the origin of the. Part of the Fluid Mechanics and Its Applications book series (FMIA, volume 44) () On vortical flow and sound generation, SIAM J.

Appl. Math. 50, pp. – MathSciNet zbMATH CrossRef Google Scholar. Weiss, P Noise Emission Due to Slender Vortex Solid Body Interactions. In: Krause E., Gersten K.

(eds) IUTAM Symposium on Dynamics. the mechanism of sound generation due to unsteady be- havior of vortex flow of fan internal flow field. Actually fan’s internal flow field has a great influence on aerody- namic noise [].

Powell [4] proposed vortex sound theory reveal the relationship between vortex of the in- ternal flow field and sound, and point out that sound. Each vortex creates a circular (ring) flow field whose axis varies slightly from the vertical as it passes.

The figure suggests that the main component of the force on the physical ring is in the direction of the jet flow. If the vortex is a true ring (all parts are in phase), a dipole sound field directed along the jet axis is. Occurrences of Noise Induced by Flow Fluid-Body Interactions for Sound Production Dimensional Analysis of Sound Generation Signal Analysis Tools of Vibration and Sound Representations of Measured Sound Mathematical Refresher References 2 Theory of Sound and Its Generation by Flow Fundamentals of Linear Acoustics Theory.

In this chapter, we simulate the flow around the rod-airfoil model and the noise generated by the wake-body interaction or body-vortex interaction for the cases of L/d = 2 and 10 at a Reynolds number based on the rod diameter (d = 6 mm) 28, (, based on the airfoil chord, c) by the coupling method using commercial CFD and acoustic BEM.

studies on their dynamics and interactions have been conducted.9 One important mechanism of vorticity generation results from the interaction between variable density and pressure fields.

In their original work on shock enhanced hypersonic mixing, Marble, Hendricks, and Zukoski10 proposed the possibility of generating streamwise vorticity. (a) Conformal mapping. The mathematical analysis for sound due to a vortex passing round an inclined fibre (cf. figure 2) follows from the procedure outlined by Howe [] for a vortex passing over a rigid, upright spoiler in a background mean flow, which was extended for arbitrary angles of inclination θ∈(0, 1) by Clark et al.[] and whose surface geometry appears in Lighthill [] in the.

Sound Generated by a Line Vortex Interacting with a Cylindrical Body Influence of Vortex Shedding Blade–Vortex Interaction Noise in Two Dimensions Problems 6 7 ProblemsinThreeDimensions Linear Theory of Vortex–Airfoil Interaction Noise Blade–Vortex Interactions in Three Dimensions a more detailed representation of each of the vortex-wake patterns.

Figure 9: Map of vortex synchronization patterns near the fundamental lock-in region. 13 The critical curve marks the transition from one mode of vortex formation to another.

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I, II are the curves where the forces on the body show a sharp “jump”; from Bishop and Hassan {3}. I is.numbers they decay slowly. The generation, formation, evolution, and interactions of vortex rings have been the subject of numerous investigations (see, e.g. Shariff and Leonard, and the references therein).

In this study, we focus our attention on a specific characteristic of vortex ring formation; namely the impulse extremization in.