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Velocity measurement with a new probe in inhomogeneous turbulent jets


Tombach, Ivar Harald (1969) Velocity measurement with a new probe in inhomogeneous turbulent jets. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/V2CR-0Q19.


Velocity profiles have been measured in subsonic, inhomogeneous, axisymmetric turbulent jets, using a new velocity measuring probe. This probe creates a train of heat pulses at one point in the flow and measures the time interval between the time a pulse is created and the time at which it is convected by the flow past a sensing wire a short distance downstream. In a turbulent flow the detected pulses are highly disturbed, but reconstruction of a mean pulse, by a digital computer, from several hundred pulses enabled calculation of a mean velocity and a velocity fluctuation level.

Measurements were made with this probe from near the nozzle to 48 diameters downstream in several combinations of jet gas and ambient gas (air-air, air-He, He-air, and He-SF[subfield 6]) having a range of jet/ambient density ratios from 0.03 to 7.25. Axial profiles of the variation with the density ratio of the jet width, mean velocity, and turbulence level were obtained from these measurements, showing the entrainment and approach to homogeneity of the inhomogeneous jet. A jet which is less dense than the ambient fluid is seen to entrain the ambient fluid more vigorously than the denser jet, as is demonstrated by its higher turbulence levels, more rapid growth, and more rapid axial decay of the mean velocity.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Aeronautics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Roshko, Anatol
Thesis Committee:
  • Roshko, Anatol (chair)
  • Coles, Donald Earl
Defense Date:20 May 1969
Record Number:CaltechETD:etd-03312009-110134
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1231
Deposited By: Imported from ETD-db
Deposited On:01 Apr 2009
Last Modified:20 Dec 2019 19:43

Thesis Files

PDF (Tombach_ih_1969.pdf) - Final Version
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