Velocity and Passive Scalar Characteristics in a Round Jet with Grids at the Nozzle Exit

Velocity and passive scalar (temperature) measurements have been made in the near field of a round jet with and without obstructing grids placed at the jet exit. The Reynolds number ReD (based on the exit centreline velocity and nozzle diameter) is 4.9 × 104 and the flow is incompressible, while the temperature rise does not affect the velocity behaviour. The streamwise development and radial spreading of the passive scalar are attenuated, relative to the unobstructed jet. Close to the jet outlet, the spatial similarity of the moments (up to the third-order) of velocity fluctuations is improved, when the jet is perturbed. An explanation, based on the reduced effect of the large coherent structures in the developing region, is provided.

[1]  Ari Glezer,et al.  Direct excitation of small-scale motions in free shear flows , 1998 .

[2]  S. Corrsin,et al.  The use of a contraction to improve the isotropy of grid-generated turbulence , 1966, Journal of Fluid Mechanics.

[3]  L. Chua,et al.  Calibration ofX-probes for turbulent flow measurements , 1988 .

[4]  L. Chua,et al.  The turbulent interaction region of a circular jet , 1986 .

[5]  Yang Zhang.  Experimental studies of the turbulence structures of impinging reacting jets using time-resolved particle image velocimetry visualisation, hot wire anemometry and acoustic signal processing , 2000 .

[6]  Khairul Q. Zaman,et al.  The ‘preferred mode’ of the axisymmetric jet , 1981, Journal of Fluid Mechanics.

[7]  Chih-Ming Ho,et al.  Subharmonics and vortex merging in mixing layers , 1982, Journal of Fluid Mechanics.

[8]  R. A. Antonia,et al.  Control of an axisymmetric jet using a passive ring , 2003 .

[9]  E. M. Laws,et al.  Flow Through Screens , 1978 .

[10]  S. Crow,et al.  Orderly structure in jet turbulence , 1971, Journal of Fluid Mechanics.

[11]  A. Hussain,et al.  Errors in simultaneous measurements of temperature and velocity in the outer part of a heated jet , 1980 .

[12]  A. Hussain.  Coherent structures—reality and myth , 1983 .

[13]  Zellman Warhaft,et al.  Turbulence suppression in a jet by means of a fine ring , 1994 .

[14]  S. Drobniak,et al.  The relationship between coherent structures and heat transfer processes in the initial region of a round jet , 1998 .

[15]  R. A. Antonia,et al.  Effect of initial conditions on the near-field development of a round jet , 2004 .

[16]  Khairul Q. Zaman,et al.  Vortex pairing in a circular jet under controlled excitation. Part 2. Coherent structure dynamics , 1980, Journal of Fluid Mechanics.

[17]  J. Mi,et al.  Influence of jet exit conditions on the passive scalar field of an axisymmetric free jet , 2001, Journal of Fluid Mechanics.

[18]  J. E. Ffowcs Williams,et al.  Active cancellation of pure tones in an excited jet , 1984, Journal of Fluid Mechanics.

[19]  M. Farge.  Wavelet Transforms and their Applications to Turbulence , 1992 .

[20]  R. A. Antonia,et al.  Effect of different initial conditions on a turbulent round free jet , 2002 .

[21]  R. Gould,et al.  Towards better uncertainty estimates for turbulence statistics , 1996 .

[22]  J. Eaton,et al.  Creating homogeneous and isotropic turbulence without a mean flow , 2004 .

[23]  R. Antonia,et al.  The Heated Round Jet in a Coflowing Stream , 1976 .

[24]  Brian Launder.  Heat and mass transport , 1975 .

[25]  Khairul Q. Zaman,et al.  Vortex pairing in a circular jet under controlled excitation. Part 1. General jet response , 1980, Journal of Fluid Mechanics.

[26]  B. Boersma,et al.  Simulation of the mixing of a passive scalar in a round turbulent jet , 2001 .

[27]  S. Corrsin,et al.  Further experiments on the flow and heat transfer in a heated turbulent air jet , 1947 .

[28]  S. Corrsin,et al.  Measurements of the nearly isotropic turbulence behind a uniform jet grid , 1974, Journal of Fluid Mechanics.

[29]  G. Batchelor,et al.  The theory of homogeneous turbulence , 1954 .

[30]  William K. George,et al.  Velocity measurements in a high-Reynolds-number, momentum-conserving, axisymmetric, turbulent jet , 1994, Journal of Fluid Mechanics.

[31]  Narinder K. Tutu,et al.  Intermittency and preferential transport of heat in a round jet , 1978, Journal of Fluid Mechanics.

[32]  John C. LaRue,et al.  The decay power law in grid-generated turbulence , 1990, Journal of Fluid Mechanics.

[33]  John C. LaRue,et al.  Measurement of high‐frequency turbulent temperature , 1975 .

[34]  F. Browand,et al.  The Roles of Large Scale Structures in the Initial Development of Circular Jets , 1975 .

[35]  R. W. Miksad,et al.  Implementation of the continuous wavelet transform for digital time series analysis , 1997 .

[36]  R. A. Antonia,et al.  Correction of cold-wire response for mean temperature dissipation rate measurements , 2003 .

[37]  J. Lumley,et al.  Turbulence measurements in axisymmetric jets of air and helium. Part 1. Air jet , 1993, Journal of Fluid Mechanics.

[38]  F. Hussain,et al.  Chaos control in open flows: Experiments in a circular jet , 1997 .

[39]  P. Walklate,et al.  Plane jets impinging on porous walls , 2002 .

[40]  Temporal subharmonic amplitude and phase behaviour in a jet shear layer: wavelet analysis and Hamiltonian formulation , 1999 .

[41]  Geert Brethouwer,et al.  A numerical investigation on the effect of the inflow conditions on the self-similar region of a round jet , 1998 .