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Visualization of Mechanical Processes: An International Online Journal


ISSN Online: 2152-209X

Visualization of Mechanical Processes: An International Online Journal

DOI: 10.1615/VisMechProc.v2.i1.30

VORTICAL STRUCTURE DYNAMICS OF SEPARATED CHANNEL FLOW BEHIND A SEMICYLINDRICAL RIB AT LATE STAGES OF LAMINAR-TURBULENT TRANSITION

Valery M. Molochnikov
Hydrodynamics and Heat Transfer Laboratory, Research Center for Power Engineering Problems, Kazan Scientific Center of the Russian Academy of Sciences, 2/31 Lobachevsky st., Kazan 420111, Russia
Olga A. Dushina
Hydrodynamics and Heat Transfer Laboratory, Research Center for Power Engineering Problems, Kazan Scientific Center of the Russian Academy of Sciences, 2/31 Lobachevsky st., Kazan 420111, Russia
Anton A. Paereliy
Hydrodynamics and Heat Transfer Laboratory, Research Center for Power Engineering Problems, Kazan Scientific Center of the Russian Academy of Sciences, 2/31 Lobachevsky st., Kazan 420111, Russia

ABSTRACT

Results of visual research of the flow structure dynamics in the region of flow separation behind a semicylindrical rib in a channel at transitional flow regimes are presented. Smoke-wire flow visualization was recorded by a high-speed camera. Experiments were conducted in the range of Reynolds numbers 370−4200 calculated using the channel height. Successive stages of the shear layer stability loss behind the rib and generation of spanwise vortices were observed. Reynolds numbers corresponding to the shear layer instability onset were defined. Some features of dynamics of the vortex generation onset region were described. Most probable scenarios of vortex evolution in the flow reattachment region were revealed. Large-scale vortex generation frequencies depending on Reynolds number were estimated. Possible mechanism of vortex generation at the late stages of transition to turbulence in separated flows was described.

REFERENCES

  1. Boiko, A.V. et al., Turbulence Origination in Near-Wall Flows (in Russian), Nauka, Novosibirsk, 1999.

  2. Dovgal, A.V. and Sorokin, A.M., Instability of flow in the region of laminar boundary layer separation against regular vortex shedding, Teplofiz. Aeromekh. (in Russian), vol. 8, no. 2, pp. 189-197, 2001.

  3. Dovgal, A.V. and Sorokin, A.M., Experimental simulation of regular vortex shedding in separated flow behind a surface step, Teplofiz. Aeromekh. (in Russian), vol. 9, no. 2, pp. 193-200, 2002.

  4. Gortyshov, Yu.F. et al., Heat Transfer and Hydraulic Efficiency of Promising Ways of Heat Transfer Enhancement in Heat Exchangers (in Russian), Center of Innovative Technology, Kazan, 2009.

  5. Hasan, M.A.Z., The flow over a backward-facing step under controlled perturbation: Laminar separation, J. Fluid Mech., vol. 238, pp. 73-96, 1992. DOI: 10.1017/S0022112092001642

  6. Nazmeev, Yu.G., Heat Transfer in Laminar Fluid Flows in Channels with Discrete Roughness Elements (in Russian), Energoatomizdat, Moscow, 1998.

  7. Roos, F.W. and Kegelman, J.T., Control of coherent structures in reattaching laminar and turbulent shear layers, AIAA J., vol. 24, pp. 1956-1963, 1986. DOI: 10.2514/3.9553