Self Sustained Low Frequency Resonance in Low-Mach-Number Gas Flow Through Pipe-Lines with Side-Branch Cavities: A Semi-Empirical Model

This paper examines the energy conversion mechanisms which govern the emission of low frequency sound from an axisymmetric jet pipe of arbitrary nozzle contraction ratio in the case of low Mach number nozzle flow. The incident acoustic energy which escapes from the nozzle is partitioned between two distinct disturbances in the exterior fluid. The first of these is the free-space radiation, whose directivity is equivalent to that produced by monopole and dipole sources. Second, essentially incompressible vortex waves are excited by the shedding of vorticity from the nozzle lip, and may be associated with the large-scale instabilities of the jet. Two linearized theoretical models are discussed. One of these is an exact linear theory in which the boundary of the jet is treated as an unstable vortex sheet. The second assumes that the finite width of the mean shear layer of the real jet cannot be neglected. The analytical results are shown to compare favourably with recent attenuation measurements.

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Velocity measurement in low Reynolds and low Mach number slip flow through a tube

Experimental Thermal and Fluid Science ◽

10.1016/j.expthermflusci.2014.10.001 ◽

2015 ◽

Vol 60 ◽

pp. 284-289 ◽

Cited By ~ 2

Author(s):

Vijay Varade ◽

Amit Agrawal ◽

S.V. Prabhu ◽

A.M. Pradeep

Keyword(s):

Mach Number ◽

Velocity Measurement ◽

Slip Flow ◽

Low Mach Number ◽

Flow Through ◽

Low Reynolds

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The generation of combustion noise by chemical inhomogeneities in steady, low-Mach-number duct flows

Journal of Fluid Mechanics ◽

10.1017/s0022112080000663 ◽

1980 ◽

Vol 99 (2) ◽

pp. 383-397 ◽

Cited By ~ 10

Author(s):

Y. L. Sinai

Keyword(s):

Heat Transfer ◽

Mach Number ◽

Turbulent Flows ◽

Low Frequency ◽

Combustion Noise ◽

Low Mach Number ◽

First Order ◽

Specific Heats ◽

Chemically Reacting ◽

Frequency Character

The low-frequency character of two model problems is exploited in order to illustrate the acoustic consequences of the interactions between chemically reacting (or relaxing) inhomogeneities and flames or constrictions in ducts. The monopole of the former is associated with heat transfer in a fluid which exhibits variations in its specific heats, while in the latter there is an extension of the classical phenomenon associated with the pulsations of an inhomogeneity of the fluid compressibility. This second mechanism is found to be insignificant, but the heat-conduction source is considered to be very powerful at sufficiently low Mach numbers; in fact, to first order it is independent of the flow Mach number for laminar, as well as a certain class of turbulent, flows.

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Nonideal Isentropic Gas Flow Through Converging-Diverging Nozzles

Journal of Fluids Engineering ◽

10.1115/1.2909425 ◽

1990 ◽

Vol 112 (4) ◽

pp. 455-460 ◽

Cited By ~ 12

Author(s):

W. Bober ◽

W. L. Chow

Keyword(s):

Mach Number ◽

Gas Flow ◽

Accurate Solution ◽

Gas Flows ◽

Kutta Method ◽

Runge Kutta Method ◽

Nonideal Gas ◽

Reservoir Conditions ◽

Flow Through ◽

Isentropic Gas

A method for treating nonideal gas flows through converging-diverging nozzles is described. The method incorporates the Redlich-Kwong equation of state. The Runge-Kutta method is used to obtain a solution. Numerical results were obtained for methane gas. Typical plots of pressure, temperature, and area ratios as functions of Mach number are given. From the plots, it can be seen that there exists a range of reservoir conditions that require the gas to be treated as nonideal if an accurate solution is to be obtained.

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