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Mixing due to grid-generated turbulence of a two-layer scalar profile

Published online by Cambridge University Press:  26 April 2006

Pablo Huq  and
Rex E. Britter
Pablo Huq
Affiliation:
College of Marine Studies, University of Delaware, Newark, Delaware 19716, USA
Rex E. Britter
Affiliation:
Department of Engineering, University of Cambridge, Cambridge CB2 1PZ, UK
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Abstract

In this experimental study the mixing of passive scalars that arises from shear-free decaying grid-generated turbulence is examined. The flow configuration consists of two homogeneous layers of equal density separated by a sharp interface between different mean concentrations of passive scalar. Both layers flow through a turbulence-generating grid. To determine the effect of diffusivity the scalar was heat in one experiment and salt in a second. The Schmidt number – the ratio of momentum to species diffusivity – was 7 and 700 for heat and salt respectively. Velocity, scalar and flux fields were mapped and flow visualization was undertaken to study the flows.

Integral lengthscales and (scalar) flux were determined to be independent of diffusivity, whereas the scalar Taylor microscales varied with Schmidt number, Sc, thus illustrating the disparate effects of diffusivity on large and small scales. The time series of signals showed a correspondence between locations of wθ extrema and uw extrema. Flux wθ arose from intermittent events; and the magnitude of the time-averaged flux $\overline{w\theta}$ was found to depend on the frequency, rather than on variations in the amplitude of wθ events.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 285 , 25 February 1995 , pp. 17 - 40
Copyright
© 1995 Cambridge University Press

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References

Alexopoulos, C. C. & Keffer, J. F. 1971 Turbulent wake in a passively stratified field. Phys. Fluids 14, 216–224.Google Scholar
Antonia, R. A., Chambers, A. J., Van Atta, C. W., Friehe, C. A. & Helland, K. N. 1978 Skewness of temperature derivative in a heated grid flow. Phys. Fluids 21, 509–510.Google Scholar
Batchelor, G. K. 1953 The Theory of Homogeneous Turbulence. Cambridge University Press.Google Scholar
Batchelor, G. K. 1959 Small-scale variation of convected quantities like temperature in turbulent fluid. Part 1. General discussion and the case of small conductivity. J. Fluid Mech. 5, 113–133.CrossRefGoogle Scholar
Batchelor, G. K., Howells, I. D. & Townsend, A. A. 1959 Small-scale variation of convected quantities like temperature in turbulent fluid. Part 2. The case of large conductivity. J. Fluid Mech. 5, 134–139.CrossRefGoogle Scholar
Batchelor, G. K. & Townsend, A. A. 1956 Turbulent diffusion. In Surveys in Mechanics (ed. G. K. Batchelor & R. M. Davis). Cambridge University Press.Google Scholar
Bevilaqua, P. M. & Lykoudis, P. S. 1977 Some observations on the mechanism of entrainment. AIAA J. 15, 1194–1196.Google Scholar
Bidokhti, A. & Britter, R. E. 1987 Development of a stratified shear flow facility. Report to Topexpress Ltd., UK.Google Scholar
Bradshaw, P. 1971 An Introduction to Turbulence and Its Measurement. Pergamon.Google Scholar
Breidenthal, R. E. 1981 Structure in turbulent mixing layers and wakes using a chemical reaction. J. Fluid Mech. 109, 1–24.Google Scholar
Budwig, R., Tavoularis, S. & Corrsin, S. 1985 Temperature fluctuations and heat flux in grid-generated isotropic turbulence with streamwise and transverse mean-temperature gradient. J. Fluid Mech. 153, 441–460.Google Scholar
Champagne, F. H. & Sleicher, C. A. 1967 Turbulence measurements with inclined hot wires. J. Fluid Mech. 28, 177–182.Google Scholar
Corrsin, S. 1951 The decay of isotropic temperature fluctuations in an isotropic turbulence. J. Aeronaut. Sci. 18, 417–423.Google Scholar
Danckwerts, P. V. 1953 The definition and measurement of some characteristics of mixtures. Appl. Sci. Res. A 3, 279–296.Google Scholar
Dimotakis, P. E. 1987 Turbulent shear layer mixing with fast chemical reactions. GALCIT Rep. FM87-1.Google Scholar
Huq, P. 1990 Turbulence and mixing in stratified fluids. PhD Dissertation, University of Cambridge.Google Scholar
Jones, W. P. & Musonge, P. 1988 Closure of the Reynolds stress and scalar flux equations. Phys. Fluids 31, 3589–3604.Google Scholar
Keffer, J. F., Olsen, G. J. & Kawall, J. G. 1977 Intermittency in a thermal mixing layer. J. Fluid Mech. 79, 595–607.Google Scholar
Koochesfahani, M. M. & Dimotakis, P. E. 1986 Mixing and chemical reactions in a turbulent liquid mixing layer. J. Fluid Mech. 170, 83–122.Google Scholar
Larue, J. C. & Libby, P. A. 1981 Thermal mixing layer downstream of a half-heated turbulence grid. Phys. Fluids 24, 597–603.Google Scholar
Larue, J. C., Libby, P. A. & Seshadri, D. V. R. 1981 Further results on the thermal mixing layer downstream of a turbulence grid. In 3rd Symp. on Turbulent Shear Flows, Davis.CrossRefGoogle Scholar
Lawson, R. E. & Britter, R. E. 1983 A note on the measurements of transverse velocity fluctuations with heated cylindrical sensors at small mean velocities. J. Phys. E: Sci. Instrum. 16, 563–567.Google Scholar
Libby, P. A. 1975 Diffusion of heat downstream of a turbulence grid. Acta Astronautica 2, 867–878.Google Scholar
Lin, C. C. (ed.) 1959 High Speed Aerodynamics and Jet Propulsion Series, vol. 5. Princeton University Press.Google Scholar
Macinnes, J. M. 1985 Numerical simulation of the thermal turbulent mixing layer. Phys. Fluids 28, 1013–1014.Google Scholar
Newman, G., Launder, B. E. & Lumley, J. L. 1980 Modelling the behaviour of homogeneous scalar turbulence. J. Fluid Mech. 111, 217–232.Google Scholar
Shirani, E., Ferziger, J. H. & Reynolds, W. C. 1981 Mixing of a passive scalar in isotropic and sheared homogeneous turbulence. Stanford Thermosci. Div. Tech. Rep. TF-15.Google Scholar
Sirivat, A. & Warhaft, Z. 1983 The effect of passive cross-stream temperature gradient on the evolution of temperature variance and heat flux in grid turbulence. J. Fluid Mech. 128, 323–346.CrossRefGoogle Scholar
Sreenivasan, K. R., Tavoularis, S., Henry, R. & Corrsin, S. 1980 Temperature fluctuations and scales in grid-generated turbulence. J. Fluid Mech. 100, 597–621.Google Scholar
Taylor, G. I. 1921 Diffusion by continuous movements. Proc. Lond. Math. Soc. 20, 196–212.Google Scholar
Tennekes, H. & Lumley, J. L. 1982 A First Course in Turbulence, 2nd Edn. MIT Press.Google Scholar
Townsend, A. A. 1976 The Structure of Turbulent Shear Flow, 2nd Edn. Cambridge University Press.Google Scholar
Venkataramani, K. S. & Chevray, R. 1978 Statistical features of heat transfer in grid-generated turbulence: constant-gradient case. J. Fluid Mech. 86, 513–543.Google Scholar
Warhaft, Z. & Lumley, J. L. 1978 An experimental study of the decay of temperature fluctuations in grid-generated turbulence. J. Fluid Mech. 88, 659–684.Google Scholar
Watt, W. E. & Baines, W. D. 1973 The turbulent temperature mixing layer. J. Hydr. Res. 11, 157–166.Google Scholar
Wiskind, H. K. 1962 A uniform gradient turbulent transport experiment. J. Geophys. Res. 67, 3033–3048.Google Scholar
Yeh, T. 1971 Scalar spectral transfer and higher order correlations of velocity and temperature fluctuations in heated grid turbulence. PhD dissertation, University of California (San Diego).Google Scholar
Yeh, T. & Van Atta, C. W. 1973 Spectral transfer of scalar and velocity fields in heated-grid turbulence. J. Fluid Mech. 58, 233–261.Google Scholar