Abstract
The flow within the intermixing region behind circular cylinders with stepwise change of the diameter of diameter ratio d/D of 0.5 has been examined. Based on the statistical analysis and conditional sampling of the velocity fluctuations and of flow visualization, the vortex wakes associated with the big and small cylinders have been established. Both wakes are found under the dominant primary mode, which corresponds to the vortex shedding Strouhal number of two dimensional cylinder, and the less dominant secondary mode. The Strouhal number of the secondary mode of the big vortex wake is higher than that of the primary mode and the opposite is found for the small vortex wake. Both vortex wakes and their modes are found convecting downstream and into region behind the other cylinder. Both wakes are observed to be different from that of two dimensional cylinder.
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Abbreviations
- D, d :
-
diameter of big and small cylinder
- f :
-
frequency
- R 12 (f):
-
cross-power spectral function
- R 11, R 22 :
-
auto-power functions
- Re D, Red :
-
Reynolds numbers U 0 D/v, U 0 d/v
- t :
-
time relative to triggering instant
- U 0 :
-
freestream mean velocity
- U, V, W :
-
streamwise, lateral and spanwise mean velocity, respectively
- u, v, w :
-
streamwise, lateral and spanwise velocity fluctuations, respectively
- U f :
-
phase velocity
- U T :
-
convection velocity
- u R, vr :
-
recovered u and v velocity fluctuations
- uv :
-
Reynolds stress
- x, y, z :
-
streamwise, lateral, and spanwise coordinates, respectively
- ξ :
-
separation
- γ 12 2 (f):
-
coherence function
- ΏR :
-
recovered coherent vorticity fluctuation
- ψ :
-
phase
- ψ 12 (f):
-
phase spectral function
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Ko, N.W.M., Chan, A.S.K. In the intermixing region behind circular cylinders with stepwise change of the diameter. Experiments in Fluids 9, 213–221 (1990). https://doi.org/10.1007/BF00190422
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DOI: https://doi.org/10.1007/BF00190422