# Aleksandra Aleksandrovna BozhkoPerm State University · General Physics

Aleksandra Aleksandrovna Bozhko

Doctor of Physical and Mathematical Sciences

## About

42

Publications

3,392

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297

Citations

Citations since 2016

## Publications

Publications (42)

Specific features of thermogravitational instability and thermogravitational flows arising in ferrofluids are discussed. It is shown that in contrast to ordinary fluids, the characteristics of convection setting in ferrofluids depend on the history of its storage and the conditions of experiment. This is found to be due to a complex composition of...

In this chapter the equations describing flows of non-isothermal ferrofluids and the corresponding boundary conditions are summarised. The main physical assumptions under which these equations are valid are discussed, and references to further reading are given. The constitutive equations for ferrofluid magnetisation are also reviewed. It is emphas...

A brief history and an overview of the current state of knowledge of ferrofluids (also known as ferrocolloids or ferro-nanofluids) are given. Applications of ferrofluids as advanced heat carrier media in heat management systems are emphasised. It is discussed that in the absence of a magnetic field, ferrofluids can be considered as a type of synthe...

The methodology of experimental investigation of thermogravitational and thermomagnetic convection in ferrofluids is discussed. The necessary physical conditions for the observation of thermomagnetic convection in external uniform magnetic field are identified. The methods of registering heat fluxes and visualising convection flow patterns in nontr...

The thermomagnetic mechanism of convection is considered at various orientations of the applied uniform magnetic field with respect to the temperature gradient and of the fluid layer with respect to the gravity. Its interaction with the thermogravitational mechanism is discussed. Experimental maps of stability convection-free states are obtained. H...

The chapter discusses results of hydrodynamic stability analysis of non-isothermal ferrofluid flow arising between two parallel infinite plates maintained at different temperatures and placed in a uniform external magnetic field of various orientations. To distinguish between gravitational and magnetic buoyancy effects in the most straightforward w...

The comparative experiments on conduction/convection in a ferro-nanofluid (Prandtl number 700) and its organic base, transformer oil (Prandtl number 300), are performed in a spherical cavity heated from above/below. The experiments show that the conductivity of a ferro-nanofluid increases compared to that of its base. However convection and the ass...

Stability of a mechanical equilibrium of ferromagnetic nanofluid and transformer oil in a spherical cavity carved inside a Plexiglas block heated from below is investigated experimentally. It is shown that in a fluid left at rest prior to the start of experiment the onset of convection is delayed and the convective motion arises abruptly acquiring...

The onset and decay of convection in a spherical cavity filled with ferromagnetic nanofluid and heated from below are investigated experimentally. It is found that, unlike in a single-component Newtonian fluid where stationary convection sets in as a result of supercritical bifurcation and where convection intensity increases continuously with the...

Infrared camera visualisation of convective flows in differentially heated vertical layers with the height-to-thickness ratios of 30 and 62.5 was used to demonstrate the influence of concentration stratification caused by gravitational sedimentation of magnetic particles and aggregates on the structure of convective motion. It is found that when a...

The influence of a uniform external magnetic field on convection flow instability and heat exchange in a spherical cavity filled with a magnetic fluid and heated from below is investigated experimentally. It is shown that a horizontal field orients the axis of a convection vortex along the vector of field intensity. It is also shown that the increa...

Flow patterns arising in a vertical differentially heated layer of nonconducting ferromagnetic fluid placed in an external uniform transverse magnetic field are studied experimentally and discussed from the point of view of the perturbation energy balance. A quantitative criterion for detecting the parametric point where the dominant role in genera...

Mixed thermo-gravitational and thermo-magnetic convection in a vertical layer of non-conducting magnetic fluid is investigated. Various convection patterns found computationally are confirmed experimentally.

Regimes of irregular convection in a spherical cavity filled with magnetic fluid and heated from below are detected near the convection threshold. The temperature oscillations during long experimental runs (ranging from one to several weeks) are due to the concentration heterogeneity caused by the barometric and thermal diffusion effects.

Magnetic colloids are relatively new man-made nanomaterials whose magnetic susceptibility is several orders of magnitude larger
than that of natural substances. Experiments conducted in magnetic fluids show that strengthening or weakening of thermal
convection in colloids is dictated by a competition between the gravitational and magnetic mechanism...

We propose a comprehensive theoretical and experimental investigation (including ground-based studies and experiments conducted on board of the International Space Station) with the aim of understanding and quantifying transport properties of nonconducting ferroluids and physics of their flows. The specific emphasis is on using such fluids for safe...

The instability of convection patterns representing a combination of vertical Rayleigh rolls and horizontal rolls resulting from longitudinal horizontal magnetic field is investigated in an inclined layer of magnetic colloid by experiments and numerical simulations. Visualization of convection patterns is provided by a temperature-sensitive liquid...

We study convection in a vertical layer of ferro-magnetic fluid heated from the side and subject to a transverse magnetic field. It is found that the subse-quent fluid motion is caused by interacting thermo-gravitational and thermo-magnetic mechanisms. Our experiments and computations show that the excitation of magneto-convection leads to the form...

The stability of buoyancy-driven shear flow in an inclined layer of a ferrocolloid is investigated for different values of inclinations and homogeneous longitudinal magnetic fields. Near the onset of Rayleigh convection of ferrofluid layer inclined with respect to gravity, the wave oscillatory regimes were observed in experiments and numerical simu...

Experimental studies and numerical simulations of stability of buoyancy-driven flows in a ferrocolloid for the cases of horizontal and inclined vertical orientation of a thin cylindrical cavity are performed. The influence of a homogeneous longitudinal magnetic field on convective instability and spatio-temporal patterns were also investigated. In...

The gravity convection in a plane horizontal colloid layer heated from below has been investigated experimentally and numerically.
The temperatures and heat fluxes were measured using thermocouples. The flows were visualized using a thermosensitive liquid-crystal
film. The Fourier and wavelet spectra of the thermal signals have been calculated. The...

The experimental and numerical studies of Rayleigh convection in a thin cylindrical layer have been conducted for a ferrofluid containing magnetite particles suspended in kerosene carrier liquid. Near the onset of convection, the wave oscillatory convection was observed both in the experiments and in the numerical finite volume simulations. Time pe...

The experiments have been performed on the stability of buoyancy-driven flows of a ferrofluid for the cases of an inclined and vertical orientation of thin cylindrical encloser. Visualization of flow patterns is provided by a temperature-sensitive liquid crystal sheet which serves as the lower surface of a transparent heat exchanger. The local temp...

As known magnetothermal mechanism of convection allows the creation of a
virtually arbitrary controllable body force distribution in
nonconducting diamagnetic and paramagnetic materials It is actively
investigated last years due to its uses in the field of materials
processing e g crystal growth from protein solution and paramagnetic
melts 1-3 The...

Experiments were performed to examine the influence of external homogeneous magnetic field on ferrofluid convection in thin cylindrical layer heated from one wide sidewall and cooled from another. Gravitational and magnetic mechanisms of convection as well as the influence of gravitational sedimentation of particles and their aggregates on stabilit...

In this study the effect of gravity sedimentation on ferrofluid convection has been studied both by experiments and numerical simulations. To take into account the sedimentation density gradient a two-phase mixture model was used in the simulations. Temperature difference across the layer and concentration of magnetic phase were varied in order to...

Introduction. Experimental studies of Rayleigh convection in a shallow disk have been conducted for a ferrofluid containing magnetite particles suspended in a kerosene carrier liquid. The oscillatory convection was observed in the entire investigated temperature region. The spiral and other wave regimes were revealed. In zero magnetic fields and in...

The interplay of buoyancy and thermo-magnetic convection mechanisms are investigated in a horizontal ferrofluid layer heated from one wide side and cooled from another in the presence of external uniform transversal magnetic field. The influence of gravitational settling of magnetic particles and their aggregates on heat transfer and convection ins...

Experiments were performed to examine the influence of an external homogeneous magnetic field - transversal or longitudinal - on ferrofluid convection in horizontal, inclined and vertical layers. The integral and local temperature sensors were used for measuring the heat transport across the layer. The flow patterns were visualized by a temperature...

The results of an experimental study of heat transfer in plane layers of ferrocolloids in the presence and absence of an outer uniform magnetic field are presented. The stability of mechanic equilibrium of a magnetic fluid for the cases when the strength vector is directed perpendicular or parallel to the layer is considered. The dependence of the...

A study is made of the effect of the temperature dependence of magnetization on convection and heat trqnsfer in a ferrocolloid in a homogeneous external magnetic field. The stability of the equilibrium and convective flow in plane layers is analyzed for the cases where the field intensity vector is normal or parallel to the layer. The interaction b...

Introduction. The study of ferrofluid convection in a spherical cavity is very interesting for understanding the uniform external magnetic field action on convective instability, flows and heat transfer. This geometry also allows to un- derstand magneto-viscous, concentration and induction effects. The present in- vestigations were performed to exa...

The investigation of Rayleigh convection in a thin cylindrical layer has been conducted for a ferrofluid containing magnetite single domain particles suspended in kerosene carrier liquid. Near the onset of convection the wave oscillatory convection was observed in experiments and numerical simulations using a two-phase mixture model. The influence...

Interest towards studying convective motion in magnetic suspensions is two-fold. On one hand, this is an investigation of magneto-convection arising in artificial non-conducting magnetic fluids whose magnetization in externally applied magnetic fields is many orders of magnitude higher than that in natural fluids [1]. On the other hand, it is impor...

## Projects

Project (1)

Non-linear spatio-temporal hydrodynamic stability analysis of thermomagnetic and magnetogravitational convection.