Thesis supervisor: László Baranyi
Location of studies (in Hungarian): Department of Fluid and Heat Engineering Abbreviation of location of studies: ÁHT

Description of the research topic:

The presence of solid objects in fluid streams affects the flow patterns and consequently the pressure/viscous load on the bluff body. Sometimes vortices are shed from the object and this can lead to vibration of the body that can result in fluid-structure-interaction (FSI). Naturally, the heat transfer between the object and fluid can also be a vital issue which is strongly influenced by the flow. Free stream flows are often modelled assuming a two-dimensional uniform flow. If the short-term variations in the velocity field can be neglected this assumption can lead to realistic results. However, in real-life situations often there are complex short-term variations in the velocity field of the free stream. In this case the assumption of uniform free stream approach is not acceptable. The dynamic response of systems with or without uniform free stream depends on the shape of the body and also on a very important similarity number, the Reynolds number Re=UL/ν, where U is the free stream velocity (velocity scale), L is a characteristic length of the body and ν is the kinematic viscosity of the fluid. In some industrial applications the rotation of the bluff body can be vital, for example in the case of drilling. In that case another important dimensionless number is the velocity ratio α=U/(R*ω), where R is the radius of the cylinder and ω is its angular velocity.

This research topic aims to investigate numerically the incompressible Newtonian fluid flow around and heat transfer from a rotating and heated circular cylinder placed in a uniform stream or in shear flow. This is then varied by introducing a disturbance in the uniform stream or shear flow to investigate its effects.

The main steps involved are:
• Carrying out a detailed literature survey. Since the absolute majority of the related papers are written in English, a good command of the English language is strongly recommended.
• Becoming familiar with numerical simulation. Choosing whether to develop a new code, extend an existing finite difference in-house code, or utilise a commercial CFD package (Ansys Fluent) for numerical simulations. Preferably two methods would be used and compared.
• For all computational cases, numerical investigation is needed to determine the parameters for computational domain-, grid- and time step independent solutions. Computational results should be compared with experimental and computational results available in the literature, e.g., lift and drag coefficients, Strouhal number and Nusselt number.
• Carrying out initial computations for the simplest case (a stationary cylinder in uniform flow) at different Reynolds numbers. After validation, increasing the complexity of the problem: rotating cylinder in uniform flow, rotating cylinder in shear flow, heated stationary cylinder (forced and mixed convection) in uniform and shear flows, etc. After establishing flow behaviour and heat transfer values, perturbed flow can be investigated by disturbing the uniform or shear flow using different short-term velocity profiles. Computations can be repeated to investigate the effect of Prandtl number on the flow and heat transfer.
• Assessing the contributions achieved and the possibilities for application.
• Presenting the results in international conferences and publishing contributions, eventually in indexed peer-reviewed journals.

Recommended reading:

(A) General Fluid Mechanics and Heat Transfer
[1] White, F.M.: Fluid Mechanics. 4th ed., McGraw-Hill, Boston, 1999.
[2] Zdravkovich: M.M., Flow Around Circular Cylinders. Vol. 1: Fundamentals. Oxford University Press, Oxford, 1997.
[3] Sumer, B.M., Fredsoe, J.: Hydrodynamics Around Cylindrical Structures (Advanced Series on Ocean Engineering: Volume 12). World Scientific, Singapore, 1997.
[4] Özisik, M.N.: Heat Transfer. 3rd Edition, McGraw-Hill, New York, 1985.
[5] Janna, W.S.: Engineering Heat Transfer. SI Edition, Van Nostrand Reinhold, 1988.

(B) Specialised reading:
[6] Williamson, C.H.K.: Vortex dynamics in the cylinder wake. Annual Review of Fluid Mechanics 28 (1996), 477-539.
[7] Williamson, C.H.K.: Vortex-Induced vibrations. Annual Review of Fluid Mechanics 36 (2004), 413-455.
[8] Norberg, C.: Fluctuating lift on a circular cylinder: review and new measurements. Journal of Fluids and Structures 17 (2003), 57-96.
[9] Barkley, D., Henderson, R.D., Three-dimensional Floquet stability analysis of the wake of a circular cylinder. Journal of Fluid Mechanics 322 (1996) 215–241.
[10] Baranyi, L., Computation of unsteady momentum and heat transfer from a fixed circular cylinder in laminar flow. Journal of Computational and Applied Mechanics 4 (1) (2003), 13–25.
[11] Baranyi, L.: Numerical simulation of flow around an orbiting cylinder at different ellipticity values. Journal of Fluids and Structures 24(6) (2008), 883-906.
[12] Konstantinidis, E., Balabani, S., Flow structure in the locked-on wake of a circular cylinder in pulsating flow: Effect of forcing amplitude. International Journal of Heat and Fluid Flow 29 (6) (2008), 1567–1576.
[13] Stojkovic, D., Schon, P., Breuer, M., Durst, F., On the new vortex shedding mode past rotating circular cylinder. Physics of Fluids 15 (5) (2003), 1257–1260.
[14] Muhammad, S., Manzoor, S., Sheikh, N.A., Heat transfer suppression in flow around a rotating circular cylinder at high Prandtl number. Arabian Journal for Science and Engineering 39 (11) (2014), 8051–8063.
[15] Muhammad, S., Manzoor, S., Sheikh, N.A., Free stream flow and forced convection heat transfer across rotating circular cylinder in steady regime: effects of rotation, Prandtl number and thermal boundary condition. Journal of Mechanical Science and Technology 29 (4) (2015), 1781–1797.
[16] Ikhtiar, S.U., Manzoor, N.A., Sheikh, M.A., Free stream flow and forced convection heat transfer around a rotating circular cylinder subjected to a single gust impulse. International Journal of Heat and Mass Transfer 99 (2016), 851–861.
[17] Rana, K., Manzoor, S., Sheikh, N.A., Ali, M., Ali, H.M., Gust response of a rotating circular cylinder in the vortex suppression regime. International Journal of Heat and Mass Transfer. 115 (2017), 763–776.