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It observers that an object is submerged in a liquid, more pressure is applied to its bottom surface than its top surface, as a result pressure rises within depth of fluids. A buoyancy force is generated due to the pressure difference. In the current investigation, the mathematical formulation of bio-convective stagnation point flow of a radiative Maxwell fluid with multiple slip effect on an exponentially porous stretching surface is analyzed thoroughly. The buoyancy assisting and opposing conditions with magnetic field are discussed in the current investigation. Moreover, the energy and concertation equations are formulated by the utilization of Cattaneo–Christov theory and non-uniform heat source/sink. The flow model is developed in the form of partial derivatives, then use the similarity variables to convert the physical system into nonlinear ordinary derivative. The nonlinear system is tackled numerically with the help of Bvp4c approach on the MATLAB. The graphical upshots for various emerging parameter are observed with two aspects: buoyancy assisting λ > 0 and buoyancy opposing λ < 0 . The observation shows that the greater values of mixed convection parameter improves the fluid velocity for assisting flow λ > 0 , while declining trend is noticing for opposing flow situation λ > 0 . Further, it is worth noticing that stronger inputs of thermal and concentration relaxation parameter yield lesser thermal and concentration diffusivity, which reduces the temperature and nanoparticles concentration. [ABSTRACT FROM AUTHOR]

We investigate the influence of cross thermal buoyancy to initiate the vortex shedding process around two side-by-side circular cylinders kept in a free stream flow. The critical buoyancy parameter is assessed for the Reynolds number in the range 10–40. In the stated range, a steady separated flow evolves under the pure forced convective condition. However, with the introduction of thermal buoyancy, instability grows and at a specific value of the buoyancy parameter, the flow turns into unsteady periodic with the formation of vortex shedding. The above phenomena have been examined numerically by a two dimensional simulation based on a finite volume method for a fixed gap spacing between the cylinders and considering air as the working medium. It is observed that the strength of the buoyancy could be a decisive factor in demarcating various flow regimes. The critical strengths of buoyancy where the flow transforms into unsteady periodic from the steady pattern are estimated for the Reynolds number range. It shows a decreasing pattern with increasing Reynolds number. The flow transition is visualized through the vorticity, isotherm contours, lift signals and phase diagrams. Furthermore, a regime diagram is constructed to clearly depict various zones of hydrodynamic behavior. [ABSTRACT FROM AUTHOR]

In the present study, the exact solution of a nanofluid flow and mixed convection within a vertical cylindrical annulus with suction/injection, which is adjacent to the radial magnetic field, is presented with regard to the motion of cylinders' walls. The impact of Brownian motion and shape factor on the thermal state of CuO–water nanofluid is also considered. The influence of such parameters as Hartmann number, mixed convection parameter, suction/injection, volume fraction of nanoparticles and motion of cylinders' walls on flow and heat transfer is probed. The results show that the shape of the nanoparticles could change the thermal behavior of the nanofluid and when the nanoparticles are used in the shape of a platelet, the highest Nusselt number is obtained (about 2.5% increasement of Nusselt number on internal cylinders' wall comparison to spherical shape). The results shed light on the fact that if, for example, the external cylinder is stationary and the internal cylinder moves in the direction of z axis, the maximum and minimum heat transfer take place on the walls of internal and external cylinders, respectively (for η = 300, about 15% increasement of Nusselt number on internal cylinders' wall). Furthermore, the enhancement of radius ratio between two cylinders increases the rate of heat transfer and decreases the shear stress on the internal cylinder's wall. [ABSTRACT FROM AUTHOR]