Motile Gyrotactic Microorganisms Research Articles

Settling of bidispersed small solid particles in a dilute suspension containing gyrotactic micro-organisms

The motivation of this research is to investigate the feasibility of utilizing bioconvection for enhancing mixing in a suspension of small solid particles. This may be important in micro-fluidic applications relevant to biotechnology and medicine, such as analyses of DNA or drugs, screening of patients, and combinatorial synthesis. Traditionally, the mixing of fluids in micro-volumes has been limited to diffusion. Due to the microscopic size of the organisms involved in bioconvection, bioconvective flows are a prospective and novel alternative for micro-fluidic mixing. This paper considers a bidispersed suspension of small solid particles that have different densities and settling velocities in a fluid that contains motile gyrotactic micro-organisms. The particles are assumed to be sufficiently small so that their Brownian diffusion is not negligible. It is found that the number density distribution of solid particles of one type impacts that of particles of the other type as well as that of micro-organisms.

The onset of bioconvection in a suspension of gyrotactic microorganisms in a fluid layer of finite depth heated from below

The aim of this paper is to investigate the effect of heating from below on the stability of a suspension of motile gyrotactic microorganisms in a fluid layer of finite depth. This problem is relevant to a number of geophysical applications, such as investigation of the dynamics of some species of thermophiles (heat-loving microorganisms) living in hot springs. It is established that heating from below makes the system more unstable and helps the development of bioconvection. By performing a linear stability analysis, a correlation for the critical bioconvection Rayleigh number is obtained.

Stability of a suspension of gyrotactic microorganisms in superimposed fluid and porous layers

The aim of this paper is to investigate the stability of a suspension of motile gyrotactic microorganisms in a system that consists of superimposed fluid and porous layers. This is relevant to many biological applications, such as growing motile microorganisms in Petri dishes. By performing a linear stability analysis a correlation for the critical Rayleigh number is obtained.

EFFECT OF SMALL SOLID PARTICLES ON THE DEVELOPMENT OF BIOCONVECTION PLUMES

We investigate numerically the impact of small solid particles on the steady-state bioconvection plume caused by up-swimming of motile gyrotactic micro-organisms. Small solid particles that are heavier than water are added into the upper fluid layer when bioconvection has already attained its steady-state. As sedimentation process goes on, solid particles get involved in convection. They impact the fluid flow and cause the transition of the bioconvection plume to a different steady-state

Effect of small particles on this stability of bioconvection in a suspension of gyrotactic microorganisms in a layer of finite depth

We investigate the effect of small particles that are heavier than water on the stability of a suspension of motile gyrotactic microorganisms in a horizontal fluid layer of finite depth. If bioconvection develops, it enhances mixing and slows down the settling of the particles, which may be important in pharmaceutical applications. A linear stability analysis is utilized to investigate this problem. It is established that the critical Rayleigh number increases with the increase of the average number density of small particles, which means that the particles make the suspension more stable

A 2D analysis of stability of bioconvection in a fluid saturated porous medium — estimation of the critical permeability value

The main purpose of this paper is to perform a 2D stability analysis of bioconvection in a suspension of motile gyrotactic microorganisms in a fluid saturated porous medium and to obtain an analytical expression for the critical permeability of the porous medium. Recent numerical investigation by Kuznetsov and Jiang [1] suggests that permeability is a very important parameter for bioconvection in porous media. Their numerical results indicate that for small permeability bioconvection is stable (the microorganisms swim in the upward direction), while for large permeability it is unstable (variations of density are enhanced and macroscopic fluid circulation is induced). In the present investigation, a simple but elegant criterion of stability of the bioconvection is obtained. This criterion gives the critical permeability of the porous medium through the cell eccentricity, average swimming velocity, fluid viscosity, and other relevant parameters.

Thermal conductivity of nickel-zinc-copper-iron ferrites: S.A. Olafa et al (Tanta University, Egypt) Science of Sintering, vol 24, no 2, 1992, 117–123

An enhancement in heat transfer due to nanofluids is essentially required in various thermal systems. Hybrid nanofluids possess high thermal conductivity and, have ability to embellish and enhance the thermal strength of common fluids. Our concern in this paper is to examine the innovative attributes of hybrid nanofluids like Manganese zinc ferrite (MnZnFe2O4) and Nickel zinc ferrite (NiZnFe2O4) in the bio-convective flow of motile gyrotactic microorganisms subject to Darcy Forchheimer medium. The effect of activation energy has also been taken into account. Mathematical treatment is carried out via MATLAB software. The use of MnZnFe2O4 - NiZnFe2O4/H2O exhibits improved thermal characteristics which desirably enhance the volume fraction of hybrid nanoparticles. A comparison is provided in order to appraise the efficiency of code. The numerical results are interpreted by means of graphs and tables. The hybrid composition of zinc ferrites in the base fluid together with motile microorganisms substantially improved the heat transfer rate. It can be deduced from the culminations of the present work that the Forchheimer parameter and the bioconvection Peclet number cause a reduction in the velocity of fluid and density distribution of motile gyrotactic microorganisms respectively.