Stagnation Point Flow of Hybrid Nanofluid over a Permeable Vertical Stretching/Shrinking Cylinder with Thermal Stratification Effect

Abstract

Hybrid nanofluid is invented to improve the heat transfer performance of traditional

working fluids (water, traditional nanofluid) in many engineering applications. The

present study highlights the numerical solutions and stability analysis of stagnation

point flow using hybrid nanofluid over a permeable stretching/shrinking cylinder. The

combination of copper (Cu) and alumina (Al2O3) nanoparticles with water as the base

fluid is analytically modeled using the single phase model and modified thermophysical

properties. A set of transformation is adopted to reduce the complexity of the

governing model and then, numerically computed using the bvp4c solver in Matlab

software. Suction parameter is vital to generate dual similarity solutions in shrinking

cylinder case while no solution is found if the surface is impermeable. Two solutions

are possible for the assisting and opposing flow within a specific value of the buoyancy

parameter. For the shrinking cylinder, Al2O3-water nanofluid has the lowest heat

transfer rate than Cu-water and hybrid Cu-Al2O3/water nanofluids. A suitable

combination of alumina and copper nanoparticles volumetric concentration in hybrid

nanofluid can produce higher heat transfer rate than the Cu-water nanofluid. The

execution of stability analysis reveals that the first solution is more realistic than

second solution. However, the present results are only fixed to the combination of

copper and alumina nanoparticles only and the other kind of hybrid nanofluid may

have different outcomes.