Abstract
The present work has been aimed at gaining some new insights into instability phenomena arising when an air jet impinges on a flat plate under certain conditions. At a critical Mach number, depending on the impingement distance, the jet loses its circumferential appearance with the formation of evenly equidistant azimuthal structures, whose number and location depend on the nozzle geometry and on the flow conditions. The instability is investigated in terms of pressure and adiabatic wall temperature; the latter is measured by means of an infrared scanning radiometer. Entrainment effects are found to play a key role in the priming and evolution of the instability.
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Abbreviations
- C 1, C 2, C 3 :
-
circumferences over which structures are located
- D :
-
nozzle exit diameter [m or mm]
- L :
-
distance from plate to nozzle supporting flange [m]
- M :
-
Mach number
- n :
-
number of structures
- p :
-
local pressure [N m-2]
- r :
-
recovery factor
- R :
-
radial distance from jet center [m]
- R e :
-
Reynolds number, based on nozzle diameter, VD/v
- T :
-
temperature [K]
- T aw :
-
adiabatic wall temperature [K]
- T j :
-
jet static temperature [K]
- V :
-
velocity at nozzle exit [m s-1]
- Z :
-
nozzle-to-plate distance [m]
- ɛ:
-
emissivity coefficient
- ν:
-
kinematic viscosity [m2 s-1]
- a :
-
ambient
- c :
-
plate center
- o :
-
stagnation conditions
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The authors wish to thank Mr. V. Rottino and Mr. A. Sicardi whose technical assistance in setting up the experimental arrangement was greatly appreciated.
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Meola, C., de Luca, L. & Carlomagno, G.M. Azimuthal instability in an impinging jet: adiabatic wall temperature distribution. Experiments in Fluids 18, 303–310 (1995). https://doi.org/10.1007/BF00211385
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DOI: https://doi.org/10.1007/BF00211385