Image processing of hydrogen bubble flow visualization for determination of turbulence statistics and bursting characteristics |
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Authors: | L J Lu C R Smith |
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Institution: | (1) Department of Mechanical Engineering and Mechanics, Lehigh University, 18015 Bethlehem, Pennsylvania, USA |
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Abstract: | A technique is described which employs automated image processing of hydrogen-bubble flow visualization pictures to establish local, instantaneous velocity profile information. Hydrogen bubble flow visualization sequences are recorded using a high-speed video system and then digitized, stored, and evaluated by a VAX 11/780 computer. Employing special smoothing and gradient detection algorithms, individual bubble-lines are computer identified, which allows local velocity profiles to be constructed using time-of-flight techniques. It is demonstrated how this techniques may be used to 1) determine local velocity behavior as a function of position and time, 2) evaluate time-averaged turbulence properties, and 3) correlate probe-type turbulent burst detection techniques with the corresponding visualization data.List of symbols
Re
Reynolds number based on momentum thickness, u
/
-
t
+
nondimensional time tu
2
/
-
T
VITA variance averaging time period
-
u
shear velocity =
-
u
local instantaneous streamwise velocity,x-direction
-
u
local fluctuating streamwise velocity,x-direction
-
u
+
nondimensional streamwise velocity,
/u
-
local normal velocity,y-direction
-
w
local spanwise velocity,z-direction
-
x
+
nondimensional coordinate in streamwise direction xu
/v
-
y
+
nondimensional coordinate normal to wall, yu
/v
Greek
momentum thickness,
-
kinematic viscosity
-
w
wall shear stress
This paper was presented at the Ninth Symposium on Turbulence, University of Missouri-Rolla, October 1–3, 1984 |
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Keywords: | |
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