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 γ and nanoparticles volumetric concentration ϕ1 for alumina, while for copper ϕ2. The stability analysis is also designed to justify the particular solutions’ stability. Additionally, the idea to obtain the solution for large value of λ and γ is also presented in this paper.

Findings

Two solutions exist in opposing and assisting flows up to a critical value λc where λc 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 λ and γ.

中文翻译：

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混合纳米流体向垂直圆柱体的混合对流驻点流动

目的

本文的目的是数值分析Cu-Al2O3/水混合纳米流体通过平板和圆柱体的混合对流的驻点流动。

设计/方法/方法

使用 bvp4c 求解器求解从边界层和能量方程减少的相似方程。在控制参数的特定范围内观察到解的对偶性，即混合对流参数λ、曲率参数 γ 和纳米颗粒体积浓度 φ1 对于氧化铝，而对于铜 φ2. 稳定性分析还旨在证明特定解决方案的稳定性。此外，获得大值的解决方案的想法 λ 和 γ 在本文中也有介绍。

发现

存在两种解决方案来反对和协助流量达到临界值 λC 在哪里 λC位于对面区域。曲率参数的升高往往会扩大临界值（延迟分离过程），同时提高工作流体的传热性能。同时，混合Cu-Al2O3/水纳米流体的应用还可以减缓层流边界层流的分离，并产生比Cu-水纳米流体和纯水更高的传热率。

原创性/价值

结果是新的和原始的。这项研究使其他研究人员受益，特别是在观察混合纳米流体的流体流动特性和传热率方面。此外，本文还提供了具有大值的解决方案的数学公式 λ 和 γ.