Abstract
The present paper gets together problems about unsteady boundary layers with industrial applications. We can enumerate some examples of applications as the flow over a flying helicopter, the fluid flow over the surface of turbines’ blades and compressors, the fluid flow over the aerodynamic surfaces of flying vehicles, etc. The unsteadiness in the flow field is due to the external flux (or the surface of the body) or by external factors of stream (or the body surface). When the fluid movement close to a surface is created nonuniform, the inviscid flow in the region of that surface appear instantaneously but the viscous layer near the body is slowly created and, in time, it reaches fully-developed steady-state. This review paper deals with the unsteady boundary layer flow of nanofluids, hybrid nanofluids, micropolar fluids, and porous media. It is shown how the set of the governing partial differential models of the considered problems are formulated into nonlinear coupled ordinary differential equations using suitable similarity transformations. The problems are fully specified in terms of characterizing parameters, known as fluid nanofluids and hybrid particle interaction parameters, mass transfer parameters (suction and injection), micropolar parameters, mixed convection parameters, local Nusselt number, etc. The effects of these parameters on the velocity and temperature fields, the skin friction coefficient, and the local Nusselt number are presented using figures and tables, respectively. We emphasize that such a review of unsteady boundary layer flow has not presented before. It is well known that nanofluids have a determinant role in heat transfer problems, getting an augmentation of thermal conductivity by controlling their characteristics as per requirements. Nanofluids and hybrid nanofluids possess unique characteristics that have attracted many researchers over the past several decades to design new thermal systems for different engineering applications. Therefore, this review synthesizes the actual investigations on unsteady boundary layer papers, their thermo-physical properties, thermodynamic and hydrodynamic behaviours published by researcher.
Published Version
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