Purpose

This study aims to investigate thermo-bioconvection of oxytactic microorganisms occurring in a nanofluid-saturated porous lid-driven cavity in the presence of the magnetic field. The heating is provided through a bell-shaped curved bottom wall heated isothermally. The effects of the peak height of the curved bottom wall, bioconvection Rayleigh number (Rb), Darcy number (Da), Hartmann number (Ha), Peclet number (Pe), Lewis number (Le) and Grashof number (Gr) on the flow structure, temperature and the iso-concentrations of oxygen and microorganisms are examined and explained systematically. The local and global, characteristics of heat transfer and oxygen concentration, are estimated through the Nusselt number (Nu) and Sherwood number (Sh), respectively.

Design/methodology/approach

The governing equations of continuity, momentum, energy and additionally consisting of species transport equations for oxygen concentration and population density of microorganisms, are discretized by the finite volume method. The evolved linearized algebraic equations are solved iteratively through the alternate direction implicit scheme and the tri-diagonal matrix algorithm. The computation domain has meshed in non-uniform staggered grids. The entire computations are carried out through an in-house developed code written in FORTRAN following the SIMPLE algorithm. The third-order upwind and second-order central difference schemes are used for handling the advection and diffusion terms, respectively. The convergence criterion for the iterative process of achieving the final solution is set as 10–8 and 10–10, respectively, for the maximum residuals and the mass defect.

Findings

The results show that the flow and temperature distribution along with the iso-concentrations of oxygen and microorganisms are markedly affected by the curvature of the bottom wall. A secondary circulation is developed in the cavity that changes the flow physics significantly. The Nu increases with the peak height of the curved bottom wall and Da; however, it decreases with Ha and Rb. The Sh increases with Da but decreases with Ha and the peak height of the curved wall.

Research limitations/implications

A similar study of bioconvection could be extended further considering thermal radiation, chemical attraction, gravity, light, etc.

Practical implications

The outcomes of this investigation could be used in diverse fields of multi-physical applications such as in food industries, chemical processing equipment, fuel cell technology and enhanced oil recovery.

Originality/value

The insights of bioconvection of oxytactic microorganisms using a curved bottom surface along with other physical issues such as nanofluid, porous substance and magnetic field are addressed systematically and thoroughly.

中文翻译：

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钟形弯曲底部加热的纳米流体饱和多孔腔中催产微生物的磁流体动力学混合生物对流

目的

本研究旨在研究在磁场存在下纳米流体饱和的多孔盖驱动腔中发生的催产微生物的热生物对流。通过等温加热的钟形弯曲底壁提供加热。弯曲底壁峰高、生物对流瑞利数 (Rb)、达西数 (Da)、哈特曼数 (Ha)、佩克莱数 (Pe)、刘易斯数 (Le) 和格拉肖夫数 (Gr) 的影响系统地检查和解释了流动结构、温度以及氧气和微生物的等浓度。局部和全局的传热特征和氧气浓度分别通过努塞尔数 (Nu) 和舍伍德数 (Sh) 进行估计。

设计/方法/方法

连续性、动量、能量的控制方程以及由氧浓度和微生物种群密度的物种输运方程组成的控制方程，通过有限体积法离散化。进化出的线性代数方程通过交替方向隐式方案和三对角矩阵算法进行迭代求解。计算域已在非均匀交错网格中进行网格划分。整个计算是通过内部开发的代码按照 SIMPLE 算法用 FORTRAN 编写的。三阶迎风和二阶中心差分格式分别用于处理对流和扩散项。迭代过程达到最终解的收敛标准分别设置为10-8和10-10，

发现

结果表明，底壁的曲率显着影响了流动和温度分布以及氧气和微生物的等浓度。腔内形成了二次循环，显着改变了流动物理。Nu 随弯曲底壁峰高和 Da 的增加而增加；然而，它随着 Ha 和 Rb 下降。Sh 随 Da 增加，但随 Ha 和弯曲壁的峰高而减小。

研究限制/影响

考虑到热辐射、化学引力、重力、光等，可以进一步扩展对生物对流的类似研究。

实际影响

这项调查的结果可用于多物理应用的不同领域，例如食品工业、化学加工设备、燃料电池技术和提高石油采收率。

原创性/价值

系统和彻底地解决了使用弯曲底面的催产微生物生物对流以及纳米流体、多孔物质和磁场等其他物理问题的见解。