Experiments in Fluids

, Volume 15, Issue 2, pp 117–129 | Cite as

On the analysis of an impinging jet on ground effects

  • J. M. M. Barata
  • D. F. G. Durão
  • M. V. Heitor
  • J. J. McGuirk
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Accepted:

Abstract

Laser Doppler measurements and flow visualization are presented for a turbulent circular jet emerging into a low-velocity cross-stream and, then, impinging on a flat surface perpendicular to the jet-nozzle axis. The experiments were performed for a Reynolds number based on the jet-exit conditions of 6 × 104, a jet-to-crossflow velocity ratio of 30 and for an impingement height of 5 jet diameters and include mean and turbulent velocity characteristics along the two normal directions contained in planes parallel to the nozzle axis. The results, which have relevance to flows found beneath VSTOL aircraft in ground effect, show the presence of a complex 3-D scarf vortex formed around the impinging jet. In zones where measurement data are not available, the flow details are numerically-visualized using a solution of the finite difference form of the fully threedimensional Reynolds-averaged Navier-Stokes equations, incorporating the turbulence viscosity concept.

The turbulent structure of the flow is affected by flow distortion at the impinging zone, which results in an unconventional behaviour of the dimensionless structure parameters that determine the empirical constants in engineering models of turbulence. The relative magnitude of the terms involved in the transport equations for the turbulent stresses is quantified from the experimental data in order to assess the importance of these effects and show the extent to which the turbulent structure of the impingement zone is affected by extra rates of strain.

Keywords

Turbulent Structure Ground Effect Nozzle Axis Flow Distortion Finite Difference Form 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

D

Diameter of jet

H

Height of crossflow tunnel

k

Turbulent kinetic energy

Re

Reynolds number

Ruv

Shear stress correlation coefficient

U

Horizontal velocity component, U=Ū+u′

V

Vertical velocity component, V=V+v′

X

Horizontal coordinate

Y

Vertical coordinate

Z

Transverse coordinate

vT

Turbulent viscosity

Subscripts

j

Jet-exit value

o

Crossflow value

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Copyright information

© Springer-Verlag 1993

Authors and Affiliations

  • J. M. M. Barata
    • 1
  • D. F. G. Durão
    • 1
  • M. V. Heitor
    • 1
  • J. J. McGuirk
    • 2
  1. 1.Mechanical Engineering Dept.Instituto Superior Técnico, Technical University of LisbonLisboa CodexPortugal
  2. 2.Dept. of Transport TechnologyUniversity of Technology of LoughboroughLeicestershireEngland

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