Abstract
The velocities in the mixing region of a cross flow jet injected into a freestream were studied in detail with a laser velocimeter. Three jet to freestream momentum ratios were used (3.1, 8.1, 16.2). By purposely seeding the jet and freestream separately (as well as both simultaneously), “marking” the fluid was feasible. Thus, determining the velocities that emanated from the different streams was possible. By methodically analyzing the three sets of dependent data, the size and location of the mixing region was determined. The mixing regions for the three momentum ratios were found to be of different sizes and at different locations. By proper scaling, however, the regions for the three momentum ratios were found to collapse to one scaled region. Because of the intermittent behavior of the mixing, conventional turbulence models for such mixing may not be applicable; however, detailed velocities and turbulence quantities are included for “benchmarking” predictions.
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Abbreviations
- B :
-
slot width
- H :
-
channel height
- MR :
-
momentum ratio, jet to free stream = ϱ j V j 2/ϱ ∞ U ∞ 2
- Re H :
-
Reynolds number, U ∞ H/v ∞
- U ∞ :
-
free stream velocity
- u :
-
axial velocity
- u′:
-
rms of axial velocity fluctuation
- v :
-
transverse velocity
- v′:
-
rms of transverse velocity fluctuation
- V j :
-
slot exit transverse velocity
- x :
-
axial direction (Fig. 3)
- x c :
-
x-center of mixing region
- \(\bar x\) :
-
scaled value of x, \(\bar x\) = x/B
- y :
-
transverse direction (Fig. 3)
- y c :
-
y-center of mixing region
- \(\bar y\) :
-
scaled value of y, \(\bar y\) = y/ √MRB
- δ x :
-
mixing region width in x-direction
- δ y :
-
mixing region width in y-direction
- \(\bar \delta _x\) :
-
scaled mixing region width in x-direction, \(\bar \delta _x\) = δ x /B
- \(\bar \delta _y\) :
-
scaled mixing region width in y-direction, \(\bar \delta _y\) = δ y / √MRB
- ϱ ∞ :
-
free stream density
- ϱ j :
-
slot exit density
- v ∞ :
-
kinematic viscosity of freestream
References
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This research was sponsored in part by the Fulbright Commission (Bonn, Germany), the Institut für Thermische Strömungsmaschinen, Universität Karlsruhe (Karlsruhe, Germany), and the Rotating Machinery and Controls Industrial Research Program, University of Virginia (Charlottesville, VA, USA)
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Flack, R., Dullenkopf, K. & Scherer, V. Constituency measurements in the mixing region of a cross flow jet using a laser velocimeter. Experiments in Fluids 17, 198–204 (1994). https://doi.org/10.1007/BF00190917
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DOI: https://doi.org/10.1007/BF00190917