Convective heat transfer in magnetized flow of nanofluids between two rotating parallel disks

Inspired by several implementations (metal mining, turbine disc, spinning disk, mechanical engineering and drawing of plastic film) of nanoliquid flow between rotating disks, we have reported a theoretical analysis on magnetohydrodynamic flow of kerosene base liquid containing three different nanoparticles namely manganese-zinc ferrite, cobalt ferrite and nickel-zinc ferrite between two parallel rotating-disks. Thermal radiation and convection thermal-conditions are considered. Furthermore, the significant properties of induced magnetic field are accounted to control the flow and thermal transport phenomenon. Furthermore, the temperature distribution is improved by employing Cattaneo-Christov heat flux. This communication is critical in the engineering sector due to different implementations including power technology, cooling reactors, fuel cells etc. The system of nonlinear higher order dimensionless equations is found by applying appropriate similarities-transformations. The exact solution of such strong nonlinear equations is not possible therefore we construct the numerical solution by employing bvp4c (shooting approach) in the MATLAB. Physical trends of velocities, pressure and thermal fields are discussed in detail. The outcomes indicate that stretching parameter of lower disk causes improvement in axial and radial fluid velocity. Fluid radial velocity near the lower disk is improved for growing Reynolds number. Moreover, the thermal field is enhanced for growing thermal Biot parameter at lower disk.

INVESTIGATION OF THE SPEED OF MOVEMENT OF COLD GAS DYNAMIC SPRAYING POWDER PARTICLES

The article shows the results of the study of the velocity of the sprayed powder particles on the example of cold gas-dynamic spraying of copper powder C01-11. Features and advantages of gas-dynamic spraying before other gas-thermal coating methods are given. The importance of the speed regime of coating and its influence on the formation of the coating is analyzed. A computational experimental method for determining the velocity of sprayed particles is proposed, as well as an experimental setup with the help of which it is possible to obtain objective data on the velocity regime of cold gas-dynamic coating. The design of the applied gas-dynamic spraying device is shown, which contains an electric heater of the compressed air flow and an accelerator of the heated compressed air into which the sprayed metal powder is driven due to the ejection effect. An experimental setup was used for the study, which contained two rotating disks mounted at a distance of 20 mm from each other on the shaft of a high-speed electric motor, with holes in the upper disk through which spraying occurs on the surface of the lower disk. Due to the fact that the disks with the spraying process rotate at a speed of 10587 rpm is the displacement of the sputtering figure on the lower disk relative to the projection of the hole of the upper disk on the lower disk. The magnitude of this displacement is calculated by the velocity of the particles of the sprayed powder, according to the above method. The parameters that are taken into account when calculating the speed of the spray particles of the powder is the diameter of the nozzle of the spray device 5 mm. The distance from the nozzle cut to the upper disk is 10 mm. The distance from the nozzle cut to the lower disk is 32 mm. The distance between the disks a = 22 mm. The radius on which the nozzle of the spray device is installed is 90 mm. As a result of the experiments, it was found that when spraying copper powder C01-11 at a temperature of 20 ºC, the spraying speed is 232.2 m / s, which does not provide conditions for coating, and at elevated temperatures to 285 ºC quality coating was formed. The spraying speed was from 302.7 to 359.2 m / s for critical sections of 2.5 and 3.01 mm2, and the spraying area at higher speeds was approximately 20% higher than at lower speeds. This makes it possible for researchers to determine the velocity modes of spraying and, accordingly, to more accurately assign the optimal technological parameters to achieve the highest quality results of creating functional coatings.

The effects of Coriolis force and radial stretch on the convective instability characteristics of the Bödewadt flow

The Bödewadt boundary-layer flow is induced by the rotation of a viscous fluid rotating with a constant angular velocity over a stationary disk. In this paper, the Bödewadt boundary-layer flow has been studied in the presence of the Coriolis force to observe the effect of radial stretch of the lower disk on the flow. For the first time in the literature, a numerical investigation of the effects of both stretching mechanism and the Coriolis force on the flow behaviour and on the convective instability characteristics of the above flow has been carried out. In this paper, the Kármán similarity transformations have been considered in order to convert the system of PDEs representing the momentum equations of the flow into a system of highly non-linear coupled ODEs and solved numerically to obtain the velocity profiles of the Bödewadt flow. Then, a convective instability analysis has been performed by using the Chebyshev collocation method in order to obtain the neutral curves. From the neutral curves it is observed that radial stretch has a globally stabilising effect on both the inviscid Type-I and the viscous Type-II instability modes. This underlying physical phenomena has been verified by performing an energy analysis of the flow. The results obtained excellently supports the previous works and will be prominently treated as a benchmark for our future studies.

Entropy generation and heat transfer analysis for ferrofluid flow between two rotating disks with variable conductivity

Present model analyze the flow and heat transfer of water-based carbon nanotubes (CNTs) [Formula: see text] ferrofluid flow between two radially stretchable rotating disks in the presence of a uniform magnetic field. A study for entropy generation analysis is carried out to measure the irreversibility of the system. Using similarity transformation, the governing equations in the model are transformed into a set of nonlinear coupled differential equations in non-dimensional form. The nonlinear coupled differential equations are solved numerically through the finite element method. Variable viscosity, variable thermal conductivity, thermal radiation, and volume concentration have a crucial role in heat transfer enhancement. The results for the entropy generation rate, velocity distributions, and temperature distribution are graphically presented in the presence of physical and geometrical parameters of the flow. Increasing the values of ferromagnetic interaction number, Reynolds number, and temperature-dependent viscosity enhances the skin friction coefficients on the surface and wall of the lower disk. The local heat transfer rate near the lower disk is reduced in the presence of Harman number, Reynolds number, and Prandtl number. The ferrohydrodynamic flow between two rotating disks might be useful to optimize the use of hybrid nanofluid for liquid seals in rotating machinery.

INVESTIGATION OF THE SPEED OF MOVEMENT OF POWDER PARTICLES OF COLD GAS DYNAMIC SPRAYING

The article shows the results of the study of the velocity of the sprayed powder particles on the example of cold gas-dynamic spraying of copper powder C01-11. Features and advantages of gas-dynamic spraying before other gas-thermal coating methods are given. The importance of the speed regime of coating and its influence on the formation of the coating is analyzed. A computational experimental method for determining the velocity of sprayed particles is proposed, as well as an experimental setup with the help of which it is possible to obtain objective data on the velocity regime of cold gas-dynamic coating. The design of the applied gas-dynamic spraying device is shown, which contains an electric heater of the compressed air flow and an accelerator of the heated compressed air into which the sprayed metal powder is driven due to the ejection effect. An experimental setup was used for the study, which contained two rotating disks mounted at a distance of 20 mm from each other on the shaft of a high-speed electric motor, with holes in the upper disk through which spraying occurs on the surface of the lower disk. Due to the fact that the disks with the spraying process rotate at a speed of 10587 rpm is the displacement of the sputtering figure on the lower disk relative to the projection of the hole of the upper disk on the lower disk. The magnitude of this displacement is calculated by the velocity of the particles of the sprayed powder, according to the above method. The parameters that are taken into account when calculating the speed of the spray particles of the powder is the diameter of the nozzle of the spray device 5 mm. The distance from the nozzle cut to the upper disk is 10 mm. The distance from the nozzle cut to the lower disk is 32 mm. The distance between the disks a = 22 mm. The radius on which the nozzle of the spray device is installed is 90 mm. As a result of the experiments, it was found that when spraying copper powder C01-11 at a temperature of 20 ºC, the spraying speed is 232.2 m / s, which does not provide conditions for coating, and at elevated temperatures to 285 ºC quality coating was formed. The spraying speed was from 302.7 to 359.2 m / s for critical sections of 2.5 and 3.01 mm2, and the spraying area at higher speeds was approximately 20% higher than at lower speeds. This makes it possible for researchers to determine the velocity modes of spraying and, accordingly, to more accurately assign the optimal technological parameters to achieve the highest quality results of creating functional coatings.

Development of Dynamic Model and Analytical Analysis for the Diffusion of Different Species in Non-Newtonian Nanofluid Swirling Flow

The analysis is carried out to analyze the flow through double stretchable rotating disks with the theory of radiative Cross nanofluid under the influence of variable thermal conductivity, the Hall current, Arrhenius activation energy, and binary chemical reactions. The Buongiorno nanofluid model is adopted for the governing equations of the problem which are transformed into ordinary differential equations through similarity transformations and then solved using the homotopy analysis method. The impact of dimensionless parameters on all profiles and physical quantities is presented and discussed. The radial velocity of the two disks increases with their corresponding ratio stretching rate parameter and decreases with the Hall parameter and the bioconvection Rayleigh number. The heat transfer at the lower disk enhances with the variable thermal conductivity parameter, while at the upper disk, opposite trend is observed. Mass transfer increases with the chemical reactions and temperature difference parameters at the lower disk and decreases with Arrhenius activation energy, whereas an opposite trend is observed at the upper disk. The local density number is enhanced for the larger values of Peclet and Lewis numbers. The comparison of the present work with the published literature authenticates the validation of the present work.

Rotational impact on nanoscale particles Fe2O4, NiZnFe2O4, MnZnFe2O4 suspended in C2H6O2 confined between two stretchable disks: a computational study

This communication addresses the fluid and heat transfer flanked by two stretchable rotating disks influenced by the induced magnetic field. The fluid flows due to the rotation of the stretchable disks enclosing a nanofluid having nanoparticles of three distinct ferrite compounds. The mathematical formulation of the problem is performed in a cylindrical coordinate system. Similarity analysis is applied for the sake of simplification. The velocity, pressure, induced magnetic field, and temperature distributions accompanied by surface drag force and heat flux are computed numerically by employing implicit finite difference algorithm. Effects of important emerging parameters are addressed through graphs and tables. Some pivotal findings include that magnetic parameter and reciprocal magnetic Prandtl number contribute to increasing fluid pressure near the lower disk and the opposite trend is reported in the vicinity of the upper disk. The present investigation is a benchmark problem that has a promising future in geophysics, oil refinery, and the chemical processing industry.

On Darcy-Forchheimer squeezed flow of carbon nanotubes between two parallel disks

Purpose The purpose of this paper is to construct mathematical model for squeezed flow of carbon-water nanofluid between parallel disks considering Darcy–Forchheimer porous medium. Thermal conductivity of carbon nanotubes is estimated through the well-known Xue model. Such research work is not carried out in the past even in the absence of Darcy–Forchheimer porous space. Forchheimer equation is preferred here to account for both low and high velocity inertial effects. Researchers also found that dispersion of carbon nanotubes in water elevates the thermal conductivity of resulting nanofluid by 100 per cent. Design/methodology/approach Homotopy analysis method (HAM) is used for the convergent series solutions of the governing system. Findings Nusselt number at the lower disk increases when squeezing parameter Sq enlarges. This illustrates that heat transfer rate at the lower wall can be enhanced by increasing the squeezing velocity of the lower disk. The results demonstrate a decreasing trend in temperature profile for increasing volume fraction of carbon nanotubes. Moreover, improvement in heat transfer rate because of existence of carbon nanotubes is also apparent. A significant enhancement in temperature profile is depicted when inertial permeability coefficient is enhanced. Skin friction coefficients at the lower and upper disks are higher for MWCNTs in comparison to the SWCNTs. Originality/value To the best of author’s knowledge, no such consideration has been given in the literature yet.

Spring-Assisted Motorized Transmission for Efficient Hover by Four Flapping Wings

Elastic storage has been reported to help flying insects save inertial power when flapping their wings. This motivates recent research and development of elastic storage for flapping-wing micro air vehicles (fwMAVs) and their ground (tethered) flight tests. The previous designs of spring-loaded transmissions are relatively heavy or bulky; they have not yet been adopted by freely hovering prototypes of fwMAVs, especially those with four flapping wings. It is not clear if partial elastic storage can still help save power for flapping flight while not overloading the motorized transmission. Here, we developed ultralight and compact film hinges as elastic storage for four flapping wings. This spring-assisted transmission was motor driven such that the wing beat frequency was higher than the natural frequency of elastically hinged wings. Our experiments show that spring recoil helps accelerate wing closing thus generating more thrust. When powered by a 3.18 g brushless motor, this 13.4 g fwMAV prototype with spring-assisted transmission can take off by beating four flexible wings (of 240 mm span) with up to 21–22 g thrust generation at 22–23 Hz. Due to lower disk loading and high-speed reduction, indirect drive of the four elastically hinged wings can produce a thrust per unit of electrical power of up to 4.6 g/W. This electrical-power-specific thrust is comparable to that generated by direct drive of a propeller, which was recommended by the motor (AP-03 7000kv) manufacturer.

Hall and ion-slip effects on mixed convection in a chemically reacting fluid between rotating and stationary disks

A steady incompressible chemically reacting fluid between two disks under the influence of cross-diffusion, Hall and ion-slip effects is studied by assuming the lower disk is rotating and the upper disk is stationary. The system of nonlinear differential equations representing velocity, temperature and concentration is solved numerically using spectral quasi-linearisation method. The effects of chemical reaction, Hall current and ion-slip, Dufour and Soret on velocity, temperature and concentration distributions are studied. The stress, rate of heat and mass transfers are discussed for various parameters and the results are displayed in the tabular form. It is found that increasing Hall parameter decreases the temperature and concentration, and the opposite trend observed when ion-slip parameter increased. The concentration reduces with the enhance of the chemical reaction parameter and Soret number.