Mixed Convective Transport around Counter Rotating Tandem Cylinders at Low Reynolds Number

Abstract

Rotating an object in a flowing fluid brings stability to the flow around the object. Consequently, an inherently unsteady flow may be degenerated into a steady pattern. On the contrary, cross thermal buoyancy brings instability to the flow causing triggering of vortex shedding even at relatively low Reynolds numbers. Hence, rotation and cross buoyancy produces opposing effects in this context. Furthermore, multiple objects in a flowing fluid develop intriguing wake dynamics following their interference effects. When tandem cylinders are placed in a flowing stream, depending on the gap between them, the vortex shedding may get triggered. These physical behaviors are coupled in this work to understand the simultaneous effect of rotation, cross thermal buoyancy (Richardson number, 0–1) and cylinder gap spacing (0.2–3) on the wake dynamics around tandem circular cylinders at Reynolds number 100 and Prandtl number 0.71. It is observed that at a critical rotational speed, the unsteady periodic flow is transfigured to a steady pattern. At smaller gap spacings (0.2, 0.7), a higher rotational speed is required particularly at higher strengths of buoyancy (0.5, 1) to control the flow instabilities and suppress the vortex shedding. The critical rotational speed is maximum at gap spacing of 0.2 for the highest buoyancy strength. Furthermore, the critical rotational speed reduces as the gap spacing increases.

Acknowledgement

N. V. V. Krishna Chaitanya gratefully acknowledges the financial support from Council of Scientific and Industrial Research (CSIR-HRDG), India through CSIR – Senior Research Fellowship with award no. 31/0019(11395)/2021-EMR-I.

Additional information

Notes on contributors

Nallacheruvu Venkata Vijaya Krishna Chaitanya

Nallacheruvu Venkata Vijaya Krishna Chaitanya is currently working as a research fellow under the guidance of Dr. Dipankar Chatterjee at Academy of Scientific and Innovative Research associated with Central Mechanical Engineering Research Institute, India. He received his M.Tech degree in computational fluid dynamics from University of Petroleum and Energy Studies, India and B.Tech degree in Mechanical Engineering from K L University, India. His present research includes wake vortex dynamics and control of instabilities around bluff bodies under forced and mixed convective transport.

Dipankar Chatterjee

Dipankar Chatterjee is a Senior Principal Scientist at CSIR-Central Mechanical Engineering Research Institute, India and Professor in Academy of Scientific and Innovative Research, India. Earlier he was associated with LPMI, Arts et Métiers Paris Tech, France as a post-doctoral researcher. He received his PhD from the Department of Aerospace Engineering, Indian Institute of Technology Kharagpur, India. He has published more than 100 international journal papers. His main interests are computational modeling of fluid flow and heat transfer over bluff objects, turbulence, phase change and reactive flow process modeling, lattice Boltzmann modeling and electromagnetohydrodynamic interactions in macro and micro flows.