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Monday, July 13, 2020 | History

3 edition of Controlled excitation of a cold turbulent swirling free jet found in the catalog.

Controlled excitation of a cold turbulent swirling free jet

Controlled excitation of a cold turbulent swirling free jet

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  • 15 Currently reading

Published by National Aeronautics and Space Administration, For sale by the National Technical Information Service in [Washington, DC], [Springfield, Va .
Written in English

    Subjects:
  • Fluid dynamics.

  • Edition Notes

    StatementR. Taghavi, E.J. Rice, and S. Farokhi.
    SeriesNASA technical memorandum -- 100173
    ContributionsRice, Edward J., Farokhi, Saeed., United States. National Aeronautics and Space Administration.
    The Physical Object
    FormatMicroform
    Pagination1 v.
    ID Numbers
    Open LibraryOL17099727M

    Shear flow control of cold and heated rectangular jets by mechanical tabs. Volume 1: Results and discussion @inproceedings{BrownShearFC, title={Shear flow control of cold and heated rectangular jets by mechanical tabs. Volume 1: Results and discussion}, author={William Howard Brown and Krishan K. Ahuja}, year={} }. characteristics of a swirling jet Paper 2. On the passive control of the near-field of coaxial jets by means of vortex shedding Paper 3. Preliminary studies on acoustic excitation in axisymmetric transitional jet flows Paper 4. Low Reynolds number Zero Pressure-Gradient Equilibrium Turbulent Boundary-Layer Experiments Paper 5.

    Observations suitably averaged over the many turbulent fluctuations (Figures and ) reveal that the velocity in the jet obeys a law of similarity: All cross-sections appear identical, except for a stretching factor, and the velocity profile across the jet exhibits a nearly Gaussian shape (bell curve). Therefore, we can write: u(x,r. At Mach jet case, the most efficient strategy for jet control was obtained by using a flapping excitation at the second sub-harmonic frequency with a core length reduction of 28%. This was interpreted to cause a quick transition to turbulence and lead to the more enhanced mixing rate of the jet.

    This thesis deals with the description and development of two classical turbulent shear flows, namely free jet and flat plate turbulent boundary layer flows. In both cases new experimental data has. Turbulence Control. Separation control in an axisymmetric diffuser flow by periodic excitation (A. Brunn, W. Nitsche). Fine structure of the impinging turbulent jet (S. Alekseenko et al.). Active control for drag reduction in turbulent pipe flow (K. Fukagata, N. Kasagi).


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Controlled excitation of a cold turbulent swirling free jet Download PDF EPUB FB2

Excitation on a swirling jet. with a swirl number of is excited internally by plane acoustic waves and the results are compared with a similar jet without swirl. kept constant in the two cases. Only experimental results are presented in this paper and further studies are needed to understand the mechanism of interaction.

As a first step, a free swirling turbulent jet. Abstract Experimental results from acoustic excitation of a cold free turbulent jet with and without swirl are presented. A flow with a swirl number of (i.e., moderate swirl) is excited.

Get this from a library. Controlled excitation of a cold turbulent swirling free jet. [R Taghavi; Edward J Rice; S Farokhi; United States. National Aeronautics and Space Administration.]. Experimental results from acoustic excitation of a cold free turbulent jet with and without swirl are presented.

A flow with a swirl number of (i.e., moderate swirl) is excited internally by plane acoustic waves at a constant sound pressure level and at various by: Abstract Experimental results from acoustic excitation of a cold free turbulent jet with and without swirl are presented.

A flow with a swirl number of (i.e., moderate swirl) is excited internally by plane acoustic waves at a constant sound pressure level and at various : E.

Rice, R. Taghavi and S. Farokhi. The benchmark case of turbulent impinging jet with out swirl and excitation, recommended by ERCOFTAC, is simulated first. In all investigations the jet’s Reynolds number (Re) is and jet outlet-to-target wall distance (H/D) is 2.

The simplest of such cases is the case of jet issue from a receiver (Fig.a) that is a resonator with resonance frequencies belonging to the range of the jet sensitivity to periodical excitation. Here the jet is excited without any outer sound sources []. Effect of acoustic excitation on flames of swirling dual-disk double-concentric jets Experimental Thermal and Fluid Science, Vol.

Flame Structure and Combustion Capability of Non-Premixed Rifled Nozzles. Controlled Excitation of a Cold Turbulent Swirling Free Jet J. Vib., Acoust., Stress, and Reliab (April, ) Effects of Acoustic Excitation on a Swirling Diffusion Flame. Instabilities present in a swirling jet in the Reynolds number range from 20 to 60 and a nominal swirl number of were studied experimentally, using smoke visualization, hot‐wire anemometry and acoustic excitation.

Flow visualization photographs of the natural jet show vortex breakdown at the core and rolling up of the shear layer around the jet into weak, irregular, large‐scale.

Turbulent Jets: Laboratory Observations The turbulent jet can de described by only two input variables: The diameter d of the orifice, and The velocity U J of the exiting fluid.

When the viscosity of the fluid is included, the three variables can be gathered into a single. Second, on the active control front, turbulent swirling jets were excited via plane acoustic waves. At the preferred Strouhal number and larger forcing amplitude, a mixing of a swirling jet (i.e., its rate of spread) was enhanced by using plane acoustic waves.

The results showed that forcing non-swirling jets at some excitation Strouhal numbers results in an increased generation of turbulent kinetic energy.

Huang et al. [17] studied the flow and mixing characteristics of swirling double-concentric jets subject to acoustic excitation. Active Control of Swirling Coaxial Jet Mixing with Manipulation of Large-Scale Vortical Structures 16 July | Flow, Turbulence and Combustion, Vol.

86, No. Characteristics of annular impinging jets with/without swirling flow by short guide vanes. Turbulence suppression in the near field of a free shear flow under controlled excitation is investigated in four circular jets, a plane jet, and a plane mixing layer.

Free swirling jets often occur in various mechanical, power-producing and chemical devices. They are used to control flames in combustion chambers and have also been applied in different types of spray guns and burners. One of the first attempts at a theoretical description of a laminar free swirling jet was undertaken by Loytsyanskii ().

Taghavi R, Rice EJ, Farokhi S () Controlled excitation of a cold turbulent swirling free jet. J Vib Acoust Stress Reliability Des Trans ASME– Google Scholar Zhu M, Dowling AP, Bray KNC () Self excited oscillations in combustors with spray atomizers.

An experimental study of compressible turbulent mixing enhancement in swirling jets, Hussain, A.K.M.F. and Husain, H.S. Controlled excitation of elliptic jets, Empirical scaling analysis of supersonic jet control using steady fluidic injection.

Physics of Fluids, Vol. 31, Issue. 5, p. Turbulent swirling jets with exitation [microform] / Rahmat Taghavi and Saeed Farokhi; Large amplitude acoustic excitation of swirling turbulent jets [microform] / R. Taghavi, E.J.

Rice, S. F Controlled excitation of a cold turbulent swirling free jet [microform] / R. Taghavi, E.J. Rice, and S. Mixing enhancement and control of swirling flows are of interest, The recent study of the controlled excitation of a cold turbulent swirling jet by the authors (refs.

10 to 12), was the first experimental attempt towards basic understanding of this phenomenon. flow with swirl number of (defined as the ratio of the flux of angular. Abstract Passive and active control of swirling turbulent jets is experimentally investigated.

Initial swirl distribution is shown to dominate the free jet evolution in the passive mode. Vortex breakdown, a manifestation of high intensity swirl, was achieved at below critical swirl number (S = ) by reducing the vortex core diameter.The author's first monograph on turbulent jets, indealt solely with a free submerged jet.

Since that time, the theory of the turbulent jet has been developed in many published works both in the USSR and abroad: it has been enriched with a large amount of experimental material and has been applied in many new fields of engineering.

In the last 10 years very substantial progress has been.Turbulent Jets: Theory and Models Environmental Hydraulics Definitions Jet = boundary layer flow originating from a source of momentum Plume = boundary layer flow originating from a source of buoyancy Buoyant jet (forced plume) = boundary layer flow originating from a source of momentum and buoyancy Boundary layer: high rate of change across some.