A nanofluid MHD flow with heat and mass transfers over a sheet by nonlinear boundary conditions: Heat and mass transfers enhancement

In this paper, we have numerically examined the steady boundary layer of a viscous incompressible nanofluid and its heat and mass transfers above a horizontal flat sheet. The boundary conditions considered were a nonlinear magnetic field, a nonlinear velocity and convection. Such nonlinearity in hydrodynamic and heat transfer boundary conditions and also in the magnetic field has not been addressed with the great details in the literature. In this investigation, both the Brownian motion and thermophoretic diffusion have been considered. A similarity solution is achieved and the resulting ordinary differential equations (nonlinear) are worked numerically out. Upon validation, the following hydrodynamic and heat and mass transfers parameters were found: the reduced Sherwood and Nusselt numbers, the reduced skin friction coefficient, and the temperature and nanoparticle volume fraction profiles. All these parameters are found affected by the Lewis, Biot and Prandtl numbers, the stretching, thermophoretic diffusion, Brownian motion and magnetic parameters. The detailed trends observed in this paper are carefully analyzed to provide useful design suggestions.摘要对黏性不可压缩的纳米流体在水平薄板上的稳定边界层及传热传质进行了数值研究。研究过程 中, 建立了非线性磁场、非线性速度和对流的非线性边界条件。然而, 在水动力和热边界条件及磁场 中的非线性问题尚未见研究报道。本研究中, 同时考虑了布朗运动和热泳扩散, 获得了一种相似的解 决方案并求解了该常微分方程(非线性)。通过验证找到了影响流体动力学、传热和传质的参数: 减少 舍伍德和努塞尔数, 可降低表面摩擦系数, 以及温度和纳米颗粒体积分数的分布。所有这些参数都受 到 Lewis 数、Biot 数和Prandtl 数, 以及拉伸、热泳扩散、布朗运动和磁场参数的影响。详细分析了所 观察到的现象, 并提出了有用的建议。