Mixed convective stagnation point flow of a hybrid nanofluid toward a vertical cylinder
Najiyah Safwa Khashi’ie, Norihan Md Arifin, J. H. Merkin, Rusya Iryanti Yahaya, Ioan Pop
Abstract
Purpose The purpose of this paper is to numerically analyze the stagnation point flow of Cu-Al2O3/water hybrid nanofluid with mixed convection past a flat plate and circular cylinder. Design/methodology/approach The similarity equations that reduced from the boundary layer and energy equations are solved using the bvp4c solver. The duality of solutions is observed within the specific range of the control parameters, namely, mixed convection parameter λ , curvature parameter <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>γ</m:mi></m:math> and nanoparticles volumetric concentration <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mrow><m:msub><m:mi>ϕ</m:mi><m:mn>1</m:mn></m:msub></m:mrow></m:math> for alumina, while for copper <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mrow><m:msub><m:mi>ϕ</m:mi><m:mn>2</m:mn></m:msub></m:mrow></m:math> . The stability analysis is also designed to justify the particular solutions’ stability. Additionally, the idea to obtain the solution for large value of <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>λ</m:mi></m:math> and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>γ</m:mi></m:math> is also presented in this paper. Findings Two solutions exist in opposing and assisting flows up to a critical value <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mrow><m:msub><m:mi>λ</m:mi><m:mi>c</m:mi></m:msub></m:mrow></m:math> where <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mrow><m:msub><m:mi>λ</m:mi><m:mi>c</m:mi></m:msub></m:mrow></m:math> lies in the opposing region. An upsurge of the curvature parameter tends to extend the critical value (delay the separation process), whilst increase the heat transfer performance of the working fluid. Meanwhile, the application of hybrid Cu-Al2O3/water nanofluid also can decelerate the separation of laminar boundary layer flow and produce higher heat transfer rate than the Cu–water nanofluid and pure water. Originality/value The results are new and original. This study benefits to the other researchers, specifically in the observation of the fluid flow characteristics and heat transfer rate of the hybrid nanofluid. Also, this paper features with the mathematical formulation for the solution with large values of <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>λ</m:mi></m:math> and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>γ</m:mi></m:math> .