The Influence of a Low Reynolds Number on an Impinging Round Jet
An impinging round jet is studied experimentally in a range of nozzle Reynolds number stretching from 5 500 to 44 000, and for an impact distance of 6 diameters. The turbulent structures in the free jet region and in the wall jet region is described by mean of conventional measurements (average, rms and power spectrum of the streamwise turbulent fluctuation), intermittent information and optical visualizations. For the present experimental conditions, the impact proves to have a significant influence on the free jet region; but the main result is the effect of the Reynolds number Re. The upstream and downstream behaviors exhibit the same trends. A decrease of Re provides an increase of the lateral spreading. This is best shown on the mean velocity and intermittency profiles. At low Re the rms of fluctuating velocity increases and we observe two peaks in the spectral distribution which are separated by a factor two in frequency. This fact can be interpreted as the result of successive pairings which is linked to the spreading process.
KeywordsLateral Spreading Successive Pairing Turbulent Shear Flow Fluctuate Velocity Increase Intermittency Profile
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- 1.Wyatt, L.A.: Test on the loss of vertical jet thrust due to ground effect on two simple VTOL. Planforms, with particular reference to the short SCI: Aircraft - Aero. Res. Council. R & M (1963), n° 3313.Google Scholar
- 3.Bradbury, L.J.S.: The impact of an axisymmetric jet into a normal ground. Aero, quartely, May (1972), pp. 141–147.Google Scholar
- 5.Costello, F.A.: Velocity field for a gaussian circular jet with normal impingement. J. of Applied Mechanics, Dec. (1976).Google Scholar
- 7.Leister, P.: Experimental investigation on the turbulence structure of an impinging pulsating jet in first turbulent shear flow, Pennstate (1977).Google Scholar
- 8.Boldman, D.R.; Brinich, P.F.: Mean velocity, turbulence intensity and scale in a subsonic turbulent jet impinging normal to a large flat plate. Nasa tech. (1977), B 1037.Google Scholar
- 12.Ho, C.M.; Nosseir, N.S.: Large coherent structures in an impinging jet. In turbulent shear flows 2, London, July (1979).Google Scholar
- 13.Gutmark, Y.; Haimovitch, Y.; Wolfshtein, M.: Heat transfer augmentation in turbulent impinging jets. In turbulent shear flows 2, London, July (1979).Google Scholar
- 13′.Yokobori, S.; Kasagi, N.; Hirata, M.; Nakamaru, M.; Haramura, Y.: Characteristics behaviour of turbulence and transport phenomena at the stagnation region Of an axisymmetrical impinging jet. In second turbulent shear flows, London (1979).Google Scholar
- 14.Bower, W.W.; Peters, G.R.: A Navier Stokes for the calculation of three dimensional impinging jet flows. In turbulent shear flows, July (1979).Google Scholar
- 15.Yen, K.T.: On the vertical momentum of the fountain produced by multi-jet vertical impingement on a flat ground plate. NADC 79273-60, nov. (1979), AD 082765.Google Scholar
- 17.Mejean, P.; Ayrault, M.; Schon, J.P.; Morel, R.: Effect of complex terrain on turbulent diffusion. Marseille (1982).Google Scholar
- 18.Codazzi, D.; Teitgen, R.; Burnage, H.: Etude expérimentale d’un jet pariétal turbulent plan axisymétrique. Distribution des vitesses moyennes et des tensions de Reynolds. 5ème congrès français de Mécanique, Marseille, 7–11 sept. (1981).Google Scholar