Coaxial Disks Research Articles

Darcy-Forchheimer magnetohydrodynamic flow of non-Newtonian Reiner-Rivlin hybrid nanofluid bounded by double-revolving disks

The applications of fluid flow and heat transfer between coaxial double-revolving disks are diverse and can be found in various engineering and scientific domains. In general, the utilization of engine oil ( EO) mixed with hybrid nanoparticles serves various purposes in engine cooling, such as maintaining viscosity-temperature properties, preventing corrosion, and achieving other cooling-related objectives. This investigation focuses on the Darcy-Forchheimer flow of a non-Newtonian Reiner-Rivlin hybrid nanofluid confined between double-revolving disks. The hybrid nanoparticles used include cadmium telluride ( CdTe) and titanium dioxide ( TiO2), combined with the base fluid engine oil. The dimensional flow equations are converted into dimensionless forms using suitable similarity transformations. Subsequently, a semi-analytical methodology known as the homotopy analysis method ( HAM) is utilized to tackle this problem. Graphs are used to determine the effects of the various flow parameters of the hybrid nanofluids on the velocities, temperature, skin friction coefficient, and the Nusselt number. After validating the findings against previous research, an attractive agreement was observed. Some major outcomes from this present problem are that axial, radial, and temperature profiles increase with the rise of the cross-viscosity parameter while the tangential velocity decreases. Radial velocity increased, and tangential velocity diminished with an enhanced magnetic field parameter. Radial velocity is increased for higher values of the dimensionless forced parameter. For higher values of the porosity parameter, the temperature profile improved. Also, the exploration of the Nusselt number and skin friction for the disks, incorporating the effects of a magnetic field and porous medium, reveals that skin friction for both disks increase with the rising Reynolds number and volume fraction of the cadmium telluride nanoparticles.

The effects of magnetic/nonmagnetic hybrid nanoparticles on the dynamic of Boger fluid over a coaxial disk

The effects of magnetic/nonmagnetic hybrid nanoparticles on the dynamic of Boger fluid over a coaxial disk

Exploring the influence of morphology on magnetized Ree–Eyring tri‐hybrid nanofluid flow between orthogonally moving coaxial disks using artificial neural networks with Levenberg–Marquardt scheme

AbstractThe present study presents an analysis of Ree–Eyring tri‐hybrid nanofluid flow between two expanding/contracting disks with permeable walls by applying the computing power of Levenberg–Marquardt supervised neural networks (LM‐SNNs). The effects of thermal radiation, Brownian motion, and thermophoresis were also thoroughly examined. The results are presented for tri‐hybrid nanofluid with SWCNT and MWCNT and Fe2O3 and H2O base fluid. The coupled non‐linear PDE system is transformed into a system of ODE associated with convective boundary conditions by applying the appropriate transformations. This is then accomplished numerically by using the finite difference‐based BVP‐4c MATLAB code that implements the three‐stage Lobatto IIIA formula. The results are novel and have been validated with LM‐SNNs outcomes. It has been observed that both numerical outcomes and LM‐SNNs produce equivalent results, and both approaches exhibit a drop in the velocity profile for the magnetic field near the lower plate and a rise near the upper plate. The skin friction against the Prandtl number increases, whereas the Nusselt number decreases at the upper disc. Compared to BVP‐4c numerical approaches, the given LM‐SNNs model is more dependable, efficient, and time‐saving because it requires less work and produces results quickly.

Cavitation Onset In Counter-Rotating Vortices From Diverging Disks

Cavitation occurs when the local pressure, induced by high local velocities, drops below the vapor pressure, leading to the formation of vapor bubbles. The subsequent collapse of these bubbles can cause noise, erosion, and vibrations. Recent studies show that cavitation is sensitive to water quality, i.e., the nuclei populations, the chemical composition of water, and the presence of particles. Motivated by investigating the effects of water quality on cavitation, experiments are performed in a dedicated experimental facility. This consists in two co-axial disks that are initially at rest and mutually in contact, in a tank filled with water. The fast diverging movement of the top disk with respect to the bottom one produces a jet flow inside the gap between the disks, which leads to the formation of two counter-rotating vortices. The local pressure drop induced by high flow velocities leads to a phase change. To characterize the phenomenon, two optical techniques are applied, i.e., shadowgraphy and particle image velocimetry (PIV). In performing PIV reconstruction, the sum of correlation enhances the spatial resolution of the velocity vector fields. The pressure field in the region where the vortices occur is obtained from velocity data. The water quality effects on cavitation are investigated by adding salt and using water with an abundance of nuclei inside the tank.

Calculation of the Flow Around an Oscillating Cylinder with a Coaxial Disk in the Head at Low Reynolds Numbers

Calculation of the Flow Around an Oscillating Cylinder with a Coaxial Disk in the Head at Low Reynolds Numbers

Damping Oscillations of a Cylinder with a Coaxial Disk and a Stabilizer

Damping Oscillations of a Cylinder with a Coaxial Disk and a Stabilizer

Stability of buoyancy–thermocapillary convection in molten silicon liquid bridge between two disks with different radii under gravity

By employing a linear stability analysis based on the spectral element method, we investigated the impact of radius ratio (Γr) on the stability of buoyancy–thermocapillary convection in a molten silicon liquid bridge (Pr = 0.011). This liquid bridge was located between two coaxial disks with different radii under the influence of gravity. The aspect ratio of the liquid bridge was maintained at Γ = 1, with a volume ratio Γv = 1 and a fixed height. To explore the physical mechanisms behind convection instability, a perturbation energy analysis was adopted. The free surface shape was determined using the Young–Laplace equation, and two distinct heating strategies were employed. In a top-heated liquid bridge, the convection stability under gravity is always stronger than under zero-gravity. However, in a bottom-heated liquid bridge, the convection stability under gravity is not consistently stronger than under zero-gravity; specifically, when 0.522 < Γr < 0.673, the convection stability under gravity is weaker than under zero-gravity. Despite the small height of the liquid bridge (approximately 2 mm), the maximum relative difference of the critical Marangoni number (Mac) between gravity and zero-gravity conditions reaches as high as 227.8%. In a bottom-heated liquid bridge, oscillatory instability occurs at larger radius ratios (Γr = 0.8) compared to the zero-gravity condition. Furthermore, all instabilities for various radius ratios and heating strategies were found to be of hydrodynamic in nature.

Damping oscillations of a cylinder with a coaxial disc and a stabilizer

The damped rotational oscillations of the cylinder, which is equipped with a coaxial disk in the head part, and has a stabilizer in the tail part, are studied. The elongation of the cylinder (the ratio of length to diameter) is nine. The cylinder is mounted in the test section of the low velocities wind tunnel with a wire suspension containing steel springs. In the equilibrium position, the axis of the cylinder is horizontal and parallel to the velocity vector of the incoming flow. Under the action of the air flow, the attenuation of rotational oscillations of the cylinder changes. A semiconductor strain gauge is attached to one of the suspension springs, which measures the dependence of spring tension on time during oscillations. The voltage at the output of the strain gauge is transmitted to the PC oscilloscope. The digital signal of the oscilloscope is transmitted to the computer. After calibration of the device, the frequency and amplitude of damped rotational oscillations around a horizontal axis passing through the center of the cylinder and perpendicular to the velocity vector of the incoming flow are determined. The effect of the air flow is described by analogues of rotational derivatives, which in the case of bluff bodies depend on the amplitude of the oscillations of the angle of inclination of the body and on the amplitude of the angular velocity. A simple model of the stabilizer’s effect on rotational derivatives is proposed.

Casimir–Lifshitz Frictional Heating in a System of Parallel Metallic Plates

The Casimir–Lifshitz force of friction between neutral bodies in relative motion, along with the drag effect, causes their heating. This paper considers this frictional heating in a system of two metal plates within the framework of fluctuation electromagnetic theory. Analytical expressions for the friction force in the limiting cases of low (zero) temperature and low and high speeds, as well as general expressions describing the kinetics of heating, have been obtained. It is shown that the combination of low temperatures (T < 10 K) and velocities of 10–103 m/s provides the most favorable conditions when measuring the Casimir–Lifshitz friction force from heat measurements. In particular, the friction force of two coaxial disks of gold 10 cm in diameter and 500 nm in thickness, one of which rotates at a frequency of 10–103 rps (revolutions per second), can be measured using the heating effect of 1–2 K in less than 1 min. A possible experimental layout is discussed.

Correction to: Swirling flow analysis of Eyring–Powell fluid between coaxial disks with variable property

Correction to: Swirling flow analysis of Eyring–Powell fluid between coaxial disks with variable property

Influence of the Compressibility of an Axisymmetric Flow Around a Cylinder with Coaxial Disks of Optimum Arrangement for Its Frontal Resistance at Transsonic Flow Velocities

Influence of the Compressibility of an Axisymmetric Flow Around a Cylinder with Coaxial Disks of Optimum Arrangement for Its Frontal Resistance at Transsonic Flow Velocities

A Series of Avoided Crossings of Resonances in the System of Several Different Dielectric Resonators Results in Giant Q-Factors

On an example of a system of three/four/five/six different coupled coaxial silicon disks, we realize a series of avoided crossings of resonances (ACRs) with respect to the different morphologies for the different scales of each disk. Each next step of ACR accompanied by the optimization processes of all previous ACRs contributes almost one order of magnitude to the Q-factor. As a result, we achieve unprecedented values for the Q-factors: 6.6·104 for three, 4.8·106 for four, 8.5·107 for five and several billions for six free standing silicon disks. Comparisons to such prominent methods as whispering gallery modes or quasi bound states in the continuum to boost the Q-factor demonstrate the tremendous advantage of the present approach not only in terms of Q-factor values but also in terms of mode volumes. Multipole analysis of the final hybridized resonant mode explains such extremely large Q-factor values. The analysis shows a strong redistribution of radiation owing to the almost-exact destructive interference of the dominating complex multipole radiation amplitudes.

Thermodynamic study of hybrid nanofluid to explore synergistic effects of multiple ferromagnetic nanoparticles in co-axial disks for magnetized fluid

We Consider the physical model of two-dimensional hybrid nanofluids flow, which is time dependent, laminar, incompressible inside the two co-axial stretchable disks. The length of upper and lower disks is2s(t). The two axial and radial velocity components (u,w) depends upper the radial of disks r and normal of direction z. There exists temperature T1>T2 which is constant for upper and lower disks. The continuity, momentum and energy equations are modeled in cylindrical coordinates system. The finite element technique is used to evaluate numerical solutions. It is observed that the velocity near upper and lower disks decreases by increasing the values of magnetic parameter. Increased the values of shape factorNs of (Nanoparticles) then the thermal conductivity (HDnf) decreased. The shear stress and heat transfer rate decreased by influence α,ϕ1,ϕ2 but an opposite reaction observed when increase the values of M,Re andNs.

14‐2: Angle‐insensitive meta‐surface color filters designed by integrating genetic algorithm with artificial neural network

Next‐generation displays require tiny pixel sizes and are applied to AR/VR and holograms. Conventional color filters have limitations in miniaturization and shows poor reliability from heat, light and other environment. Meta‐surface color filters (MCFs) are one of the solutions to replace conventional color filters, suitable for high‐resolution displays. Structural design parameters are adjusted to determine the filtering properties of the MCFs. In addition, the metal based meta‐surface shows better durability cause of the intrinsic characteristics of the material. However, if the structure is complicated, there require many case‐ studies for verification, which increases trial and error. In addition, resonance by phase matching between structures changes according to the angle of incident light. In this study, we suggest a method to reduce the trial and error required in designing structure. Also, the design parameters of the MCFs of the desired color was extracted through an AI model capable of reverse design. Furthermore, we propose a novel MCFs that shows characteristics independent to the angle of incident light through a coaxial hole and disk array structure.

Swirling flow analysis of Eyring–Powell fluid between coaxial disks with variable property

Abstract The main objective of this study is to examine an unsteady swirling flow of a non-Newtonian Eyring–Powell fluid between two coaxial disks. The lower and upper disks are considered to rotate with different angular velocities. The three-dimensional axisymmetric flow phenomenon and heat transfer mechanism are observed with the consequences of the magnetic field and variable thermal conductivity of the fluid. The variable thermal conductivity is taken to be dependent on the fluid temperature. The implementation of the Von Karman similarity transformations on the constituting equations of the flow phenomenon yields the dimensionless system of the non-linear equations. An optimal homotopy analysis technique is adopted to obtain analytical solutions for highly non-linear equations. In view of the same and opposite directions of disks rotation, the various aspects of the flow system corresponding to the pertinent parameters are discussed with physical significance. The obtained results indicate that both radial and axial fields are the escalating functions of the Eyring–Powell fluid parameter. Moreover, the heat transfer rate enhances with the improving variable thermal conductivity parameter.

Effect of Prandtl number on the flow instabilities in thermocapillary liquid bridges between two coaxial disks with different radii

The effect of Prandtl number on the instability of thermocapillary liquid bridges has been extensively studied, but the vast majority of efforts were put into typical cylindrical liquid bridge between two equal ends. The crystal growth practices have the propensity to form liquid bridges between unequal disks, thus the dependence of instability patterns and underlying mechanisms on the radius ratio is crucial but remains unclear. By fixing the radius ratio at Γr=0.5, we systematically explore the effects of Prandtl number and heating strategy, namely the upper heating and the bottom heating settings, on flow instabilities in thermocapillary liquid bridges between coaxial disks with different radii under microgravity through linear stability analysis based on spectral element method. In contrast to typical cylindrical liquid bridge (Γr=1), the present analysis indicates that the instability is always an oscillatory bifurcation even for small Prandtl number Pr=0.001 in the bottom heating scenario. What's more, the instability remains a stationary bifurcation and the critical Marangoni number experiences significant increase with the rise of Pr in the region of 0.001≤Pr≤1.2 for the upper heating situation. For all liquid bridges, the energy analysis results show that the instability under different Prandtl numbers can be roughly divided into three types.

On the Unsteady Rotationally Symmetric Flow Between a Stationary and a Finite Rotating Disk With a Given Change in the Axial Velocity

Abstract We consider the scenario of an unsteady viscous flow between two coaxial finite disks, one stationary and the other rotating with an axial velocity changing impulsively from zero to a constant value. The three-dimensional (3D) incompressible Navier–Stokes equations are analytically solved by postulating the polynomial profiles for the axial and circumferential velocity components and by employing the open-end condition of zero pressure difference and an integral approach. It is shown that the time-dependent squeezing of the fluid between the disks and the edge effects of the finite open-ended disks in the flow domain are determined by the compressing Reynolds number and the rotating Reynolds number for the case of laminar flow at low Reynolds numbers and small aspect ratios. The general explicit formulae are derived for the velocity and pressure distributions as a function of the compressing and rotating Reynolds numbers in this unsteady flow process (and the steady-state solutions are then obtainable as the compressing Reynolds number vanishes). A simple theoretical relationship between the radial and axial pressure gradients is deduced to hinge the radial and circumferential velocity components together. The values of the compression and rotation Reynolds numbers suitable to this theory are also suggested for the problem of rotating disk flows at low Reynolds numbers. The validity of the theoretical predictions for the circumferential, radial, and axial velocity components is partially verified through comparison with previous steady experimental and numerical results. These analytical results have the immediate engineering applications of fluid flows with varying gap widths, including wet brakes, wet clutches, hydrostatic bearings, face seals, and rotating heat exchangers.

Dynamics of elastoviscoplastic filament stretching.

We study theoretically the stretching dynamics of a yield stress material that exhibits both elastic and viscoplastic behavior. The material is confined between two coaxial disks, forming initially a cylindrical liquid bridge and then a neck when the disks are pulled apart. The material follows the Saramito-Herschel-Bulkley constitutive model and yields according to the von Mises criterion. We find that an elongated thin neck is formed when elasticity prevails, connecting the upper and lower parts of the filamentous bridge. This neck has been observed in breakup experiments of yield stress bridges, but this is the first theoretical study that predicts it. Earlier numerical and theoretical studies of filament stretching of yield stress materials failed to do so, because they excluded elasticity from the constitutive model they used in the simulations. Our results indicate that increasing elasticity leads to shorter pinching times and filament length than the viscoplastic case. This is caused by the fact that larger areas of the filament remain unyielded, while they undergo small deformation even before yielding, and only the remaining smaller yielded areas carry the burden of visible deformation. Our findings suggest that the value of the yield strain, defined as the ratio of the yield stress to the elastic modulus, should be used with caution to determine whether elastic effects will affect the filament stretching procedure or not.

Morphological nanolayer impact on hybrid nanofluids flow due to dispersion of polymer/CNT matrix nanocomposite material

<abstract> <p>The objective of this study is to explore the heat transfer properties and flow features of an MHD hybrid nanofluid due to the dispersion of polymer/CNT matrix nanocomposite material through orthogonal permeable disks with the impact of morphological nanolayer. Matrix nanocomposites (MNC) are high-performance materials with unique properties and design opportunities. These MNC materials are beneficial in a variety of applications, spanning from packaging to biomedical applications, due to their exceptional thermophysical properties. The present innovative study is the dispersion of polymeric/ceramic matrix nanocomposite material on magnetized hybrid nanofluids flow through the orthogonal porous coaxial disks is deliberated. Further, we also examined the numerically prominence of the permeability ($ {\mathrm{A}}_{\mathrm{*}} $) function consisting of the Permeable Reynold number associated with the expansion/contraction ratio. The morphological significant effects of these nanomaterials on flow and heat transfer characteristics are explored. The mathematical structure, as well as empirical relations for nanocomposite materials, are formulated as partial differential equations, which are then translated into ordinary differential expressions using appropriate variables. The Runge–Kutta and shooting methods are utilized to find the accurate numerical solution. Variations in skin friction coefficient and Nusselt number at the lower and upper walls of disks, as well as heat transfer rate measurements, are computed using important engineering physical factors. A comparison table and graph of effective nanolayer thermal conductivity (ENTC) and non-effective nanolayer thermal conductivity are presented. It is observed that the increment in nanolayer thickness (0.4−1.6), enhanced the ENTC and thermal phenomena. By the enhancement in hybrid nanoparticles volume fraction (2% to 6%), significant enhancement in Nusselt number is noticed. This novel work may be beneficial for nanotechnology and relevant nanocomponents.</p> </abstract>

Determination of the Rotational Derivatives of a Cylinder with a Coaxial Disc in an Air Flow

Determination of the Rotational Derivatives of a Cylinder with a Coaxial Disc in an Air Flow