Hostname: page-component-78c5997874-4rdpn Total loading time: 0 Render date: 2024-11-10T07:40:54.377Z Has data issue: false hasContentIssue false
  • English
  • Français

Turbulent penetration of a thermally stratified interfacial layer in a wind tunnel

Published online by Cambridge University Press:  26 April 2006

Jayesh  and
Z. Warhaft
Jayesh
Affiliation:
Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USA
Z. Warhaft
Affiliation:
Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USA
Get access Rights & Permissions [Opens in a new window]

Abstract

A stably stratified interface, with strong turbulence below and quiescent air above, is studied in a wind tunnel with the aim of simulating the conditions at the inversion cap at the top of the atmospheric boundary layer. The interfacial layer was generated by means of a composite grid, with small mesh size above and a large one below (Veeravalli & Warhaft 1989). A temperature step generated in the plenum of the wind tunnel, was located at the centre of the layer. There is no shear and thus turbulence interactions, usually masked by turbulent production in traditional mixing layers, are highlighted. Close to the grid where the velocity fluctuations are strong, buoyancy effects are insignificant, but as the turbulence decays they become dominant. The bulk Richardson number, N2B/(〈u2〉2/L2u), where NB is the Brunt—Väisälä frequency across the layer, and 〈u2〉2 and Lu are the velocity variance and integral lengthscale, respectively, of the turbulence on the lower side of the layer, varied from approximately zero close to the grid to 80 far downstream. The stratification inhibited the turbulent penetration into the layer, reducing the high skewness and kurtosis of the velocity field for the neutral case, to Gaussian values. The layer, which initially thickened with downstream distance, thinned when buoyancy became pronounced, owing to the collapse of the heat flux. Significant regions of countergradient heat flux, and reversals in sign of the triple moment transport terms were observed in the upper part of the layer. An analysis of the value of the heat flux conditioned on the temperature fluctuations, showed that the large temperature fluctuations associated with weak turbulence became affected by stratification first. Cospectral analysis shows that these fluctuations are associated with large scales. We also show that although the joint normal approximation between velocity and temperature fluctuations is sound for a passive scalar field, it becomes less good with the onset of stratification, failing completely when the stratification is strong.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 277 , 25 October 1994 , pp. 23 - 54
Copyright
© 1994 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Aleksenko, N. V., Bukreev, V. I. & Kostomakha, V. A. 1985 Interaction of two isotropic turbulent fields without shear. Zh. Prikl. Mekh. Tekh. Fiz. 1, 57–62.Google Scholar
André, J. C., DeMoor, F., Lacerure, P., Therry, G. & DuVachat, R. 1978 Modeling the 24-hour evolution of the mean and turbulent structures of the planetary boundary layer. J. Atmos. Sci. 35, 1861–1883.Google Scholar
Britter, R. E., Hunt, J. C. R., Marsh, G. L. & Snyder, W. H. 1983 The effect of stable stratification on turbulent diffusion and decay of grid turbulence. J. Fluid Mech. 127, 27–44.Google Scholar
Browand, F. K. & Hopfinger, E. J. 1985 The inhibition of vertical turbulent scale by stable stratification. In Turbulence and Diffusion in Stable Environments (ed. J. C. R. Hunt), pp. 15–27. Oxford University Press.
Caughey, S. J. 1982 Observed characteristics of the atmospheric boundary layer. In Atmospheric Turbulence and Air Pollution Modelling (ed. F. T. M. Nieuwstadt & H. van Dop), pp. 107–158. Reidel.
Champagne, F. H. & Sleicher, C. A 1967 Turbulence measurement with inclined hot wire. Part 2. J. Fluid Mech. 28, 177–182 (and Corrigendum 31, 1968, 416).Google Scholar
Crapper, P. F. & Linden, P. F 1974 The structure of turbulent density interfaces. J. Fluid Mech. 65, 45–63.Google Scholar
Deardorff, J. W. 1966 The counter-gradient heat flux in the lower atmosphere and in the laboratory. J. Atmos. Sci. 23, 503–506.Google Scholar
Dickey, T. D. & Mellor, G. L. 1980 Decaying turbulence in neutral and stratified fluids. J. Fluid Mech. 99, 13–31.Google Scholar
Fernando, H. J. S. 1992 Mixing in stratified fluids. Ann. Rev. Fluid Mech. 23, 455–493.Google Scholar
Finger, J. E. & Schmidt, H. 1986 On the efficiency of different higher order turbulence models simulating the convective boundary layer. Beitr. Z. Phys. Atmos. 59, 505–513.Google Scholar
Gilbert, B. 1980 Diffusion mixing in grid turbulence without mean shear. J. Fluid Mech. 100, 349–365.Google Scholar
Haughdal, J. & Lienhard, V. J. H. 1988 A low cost high performance cold wire bridge. J. Phys. E 21, 167.Google Scholar
Hopfinger, E. J. 1987 Turbulence in stratified fluids: A review. J. Geophys. Res. 92, 5287–5303.Google Scholar
Hunt, J. C. R. 1985 Diffusion in the stably stratified atmospheric boundary layer. J. Climate Appl. Met. 24, 1187–1195.Google Scholar
Jayesh, Yoon, K. & Warhaft, Z. 1991 Turbulent mixing and transport in a thermally stratified interfacial layer in decaying grid turbulence. Phys. Fluids A 3, 1143–1155.Google Scholar
Jayesh & Warhaft, Z. 1992 Probability distribution, conditional dissipation, and transport of passive temperature fluctuations in grid-generated turbulence. Phys. Fluids A 4, 2292–2307.Google Scholar
Komori, S. & Ueda, H. 1983 Turbulence structure in stably stratified open-channel flow. J. Fluid Mech. 130, 13–26.Google Scholar
Linden, P. F. 1979 Mixing in stratified fluids. Geophys. Astrophys. Fluid Dyn. 13, 3–23.Google Scholar
Ma, B.-K. & Warhaft, Z. 1986 Some aspects of the thermal mixing layer in grid turbulence. Phys. Fluids 29, 3114–3120.Google Scholar
Nieuwstadt, F. T. M. & Van Dop, H. (ed.) 1982 Atmospheric Turbulence and Air Pollution Modelling. Reidel.
Phillips, O. M. 1972 Turbulence in a strongly stratified fluid — is it unstable? Deep-Sea Res. 19, 79–81.Google Scholar
Posmentier, E. S. 1977 The generation of salinity finestructure by vertical diffusion. J. Phys. Oceanogr. 7, 298–300.Google Scholar
Riley, J. J., Metcalfe, R. W. & Weissmann, M. A. 1981 Direct numerical simulation of homogeneous turbulence in density-stratified fluids. In Nonlinear Properties of Internal Waves (ed. B. J. West). AIP Conf. Proc. vol. 76, pp. 79–112.
Ross, S. 1988 A First Course in Probability. Macmillan.
Ruddick, B. R., Mcdougall, T. J. & Turner, J. S. 1989 The formation of layers in a uniformly stirred density gradient. Deep-Sea Res. 36, 597–609.Google Scholar
Schumann, U. 1987 The countergradient heat flux in turbulent stratified flows. Nucl. Engng Design 100, 255–262.Google Scholar
Stillinger, D. C., Helland, K. N. & Van Atta, C. W. 1983 Experiments on the transition of homogeneous turbulence to internal waves in a stratified fluid. J. Fluid Mech. 131, 91–122.Google Scholar
Tavoularis, S. & Corrsin, S. 1981 Experiments in nearly homogeneous turbulent shear flow with a uniform mean temperature gradient. Part 1. J. Fluid Mech. 104, 311–347.Google Scholar
Thoroddsen, S. T. & Van Atta, C. W. 1992 Experimental tails and skewness of density-gradient probability density functions in stably stratified turbulence. J. Fluid Mech. 244, 547–566.Google Scholar
Thoroddsen, S. T. & Van Atta, C. W. 1993 Experimental study of the effects of grid configuration on stably stratified grid-turbulence. Dyn. Atmos. Oceans.Google Scholar
Townsend, A. A. 1976 The Structure of Turbulent Shear Flow. Cambridge University Press.
Turner, J. S. 1973 Buoyancy Effects in Fluids. Cambridge University Press.
Veeravalli, S. & Warhaft, Z. 1989 The shearless turbulence mixing layer. J. Fluid Mech. 207, 191–229.Google Scholar
Veeravalli, S. & Warhaft, Z. 1990 Thermal dispersion from a line source in the shearless turbulence mixing layer. J. Fluid Mech. 216, 35–70.Google Scholar
Venkatram, A. & Wyngaard, J. C. (ed.) 1988 Air Pollution Modeling. American Meteorological Society, Boston.
Wyngaard, J. C. 1973 On surface layer turbulence. In Workshop on Micrometeorology (ed. D. A. Haugen), pp. 101–149.
Yoon, K. & Warhaft, Z. 1990 The evolution of grid-generated turbulence under conditions of stable thermal stratification. J. Fluid Mech. 215, 601–638.Google Scholar
Zeman, O. & Lumley, J. L. 1976 Modeling buoyancy driven mixed layers. J. Atmos. Sci. 33, 1974–1988.Google Scholar
Zeman, O. & Tennekes, H. 1977 Parameterization of the turbulent energy budget at the top of the daytime atmospheric boundary layer. J. Atmos. Sci. 34, 111–123.Google Scholar