Comparison between graphene-water and graphene oxide-water nanofluid flows over exponential shrinking sheet in porous medium: Dual solutions and stability analysis

Abstract

To achieve ultra-high cooling rate requirement of modern-day industries the combined use of nanofluid and porous medium in several engineering and industrial processes provides excellent outcomes. In present analysis, the comparison between the flows of Gr-w and GO-w nanofluids over exponential shrinking sheet inside porous medium is investigated. Governing coupled PDEs are changed into ODEs by appropriate transformations which are solved numerically with the help of shooting method with RK4; and obtained dual solutions of Darcy flow for certain enforced mass suction exist and consequently, a stability analysis is performed to test physical stability of both solutions which proves physical stability of upper solution branch and instability of lower solution branch. The impacts of several physical parameters are presented in graphical modes along with a tabular comparison. The study reveals that Gr-w nanofluid delays the boundary layer flow separation more in comparison with GO-w nanofluid and hence, the requirement of mass suction for existence of Gr-w nanofluid flow is of lower amount. Also, consideration of porous material as flow medium defers the separation phenomenon. The rise of surface-drag force is witnessed for porous medium and mass suction and it is relatively larger for Gr-w nanofluid than GO-w nanofluid in case of upper branch solution and the surface cooling rate is larger for Gr-w nanofluid in comparison with GO-w nanofluid.

Keywords

• Nanofluid
• Graphene/graphene oxide nanoparticles
• Exponential shrinking sheet
• Porous medium
• Dual solutions
• Stability analysis