Rotation Of Cylinder Research Articles

Rotation of a superhydrophobic cylinder in a viscous liquid

The hydrodynamic quantification of superhydrophobic slipperiness has traditionally employed two canonical problems – namely, shear flow about a single surface and pressure-driven channel flow. We here advocate the use of a new class of canonical problems, defined by the motion of a superhydrophobic particle through an otherwise quiescent liquid. In these problems the superhydrophobic effect is naturally measured by the enhancement of the Stokes mobility relative to the corresponding mobility of a homogeneous particle. We focus upon what may be the simplest problem in that class – the rotation of an infinite circular cylinder whose boundary is periodically decorated by a finite number of infinite grooves – with the goal of calculating the rotational mobility (velocity-to-torque ratio). The associated two-dimensional flow problem is defined by two geometric parameters – namely, the number $N$ of grooves and the solid fraction $\unicode[STIX]{x1D719}$. Using matched asymptotic expansions we analyse the large-$N$ limit, seeking the mobility enhancement from the respective homogeneous-cylinder mobility value. We thus find the two-term approximation,$$\begin{eqnarray}\displaystyle 1+{\displaystyle \frac{2}{N}}\ln \csc {\displaystyle \frac{\unicode[STIX]{x03C0}\unicode[STIX]{x1D719}}{2}}, & & \displaystyle \nonumber\end{eqnarray}$$ for the ratio of the enhanced mobility to the homogeneous-cylinder mobility. Making use of conformal-mapping techniques and inductive arguments we prove that the preceding approximation is actually exact for $N=1,2,4,8,\ldots$. We conjecture that it is exact for all $N$.

Operational performance and losses in mechanized soybean harvesting as a function of field shape

Information on the capacity, operational efficiency, and performance of the harvester is very important in the management of agricultural mechanized systems, influencing decisions made with the aim of optimization. This study aimed to evaluate times, movements, and quality of mechanical soybean harvest operations in different shapes of the plots. Operational performance parameters of the harvester and variables representative of the agronomic aspects of the crop were used as indicators through statistical process control tools. Mechanized harvesting was carried out at a farm located in Uberaba, Minas Gerais, and the experimental design was completely randomized, with 18, 28, and 24 repetitions in irregular, rectangular, and trapezoidal fields, respectively. The activities of the harvester (harvest, unloading, handling, and climate charts) were monitored. The indicators of quality for harvester performance were: forward speed, engine and cylinder rotation and concave opening. The losses were determined: on the platform, internal mechanisms, total and in relation to productivity. The managerial efficiency and shunt time presented better results for the trapezoidal and rectangular section, respectively. All quality indicators evaluated were within the limits of statistical control, characterizing quality and reliability of the soybean harvesting operation.

Heat generation in a Couette-Taylor flow multicylinder system

The paper presents the results of an experimental study of energy production in the Couette-Taylor heat generator with independent rotation of cylinders: the system is applied to solving the problem of direct conversion of wind energy into thermal energy. The system consists of two nested multicylinder rotors. The regimes for two counter-rotating rotors are studied. The study is focused on the rotor drag torque and the heat power of the generator as a function of the relative angular velocity of two rotors at a fixed viscosity of the working liquid or as a function of the working liquid viscosity at a steady relative angular velocity of two rotors. Representing of this multicylinder design of the heat generator to a form of a single equivalent annular channel between two rotating cylinders allows generalization of experimental data for the law of the drag torque and specific heat power as a function of the Reynolds number. This generalization offers a possibility of developing engineering methods for calculating the thermal parameters of various systems for fluid heating.

Mixed convection of non-Newtonian nanofluid in an H-shaped cavity with cooler and heater cylinders filled by a porous material: Two phase approach

In the present problem, two-phase mixed convection of a non-Newtonian nanofluid in a porous H-shaped cavity is studied. Inside the enclosure there are four rotating cylinders, using the Boussinesq approximation, mixed convection is created. Nanofluid includes H2O + 0.5% CMC and copper oxide nanoparticles. The mixture model was used to model physical phenomena. Different aspect ratios were used in order to achieve the best heat transfer rate. The Darcy and Richardson numbers ranges are 10−4 ≤ Da ≤ 10−2 and 1 ≤ Ri ≤ 100 respectively. Also, the aspect ratio and dimensionless angular velocities of cylinders ranges are 1.4 ≤ AR ≤ 1.6 and −10 ≤ Ω ≤ 10 respectively. Streamlines and isotherm-lines contours have been obtained for the variation of Darcy and Richardson numbers, aspect ratio and angular velocity. The heat transfer rates have been obtained for various aspect ratios, Darcy and Richardson numbers, and the direction of the cylinder's rotation, and are compared with each other. The results show that the direction of cylinders rotation influences the strength and extent of the generation vortices. Also, the use of porous material in high permeability can be a good alternative to lowering the angular velocity of the cylinders and ultimately reducing the need for less energy.

Effect of a rotating cylinder on the flow of a Bingham plastic fluid in T-junction: Momentum and heat transfer characteristics

The present numerical work investigates the momentum and heat transfer characteristics of a Bingham plastic fluid in a rectangular T-channel. A rotating cylinder which is placed in a T-junction mimics the behaviour of a rotating valve to regulate the fluid flow and enthalpy in the two branches of the channel. Numerical simulations are carried out over a wide range of conditions (based on the cylinder diameter): Reynolds number (10-2⩽Re≤40), Bingham number (10-2⩽Bn≤20), Prandtl number (10⩽Pr≤100) and rotational velocity of the cylinder (-5⩽α≤5) where α is the circumferential velocity normalized by the inlet velocity. Extensive results are presented in the form of streamline patterns, isotherm contours and yielded/unyielded regions in the vicinity of the T-junction. In particular, the major thrust of this study is to predict the hydrodynamic forces and torque exerted on the cylinder, flow split ratio (i.e., flow rates in the two outlet branches), critical Bingham number (beyond which no flow separation occurs). Also, the outlet temperatures, enthalpy gain, distribution of Nusselt number over the cylinder surface and its average value as a function of the governing dimensionless parameters have been investigated. The present results show that the rotation of the cylinder can aid or suppress the formation of the recirculation zones effectively which appear on the left wall of the main branch and lower wall of the side branch depending upon the Reynolds number while it always suppresses the cylinder wake. As expected, the Bingham number stabilizes the flow by suppressing the recirculation zone while the Reynolds number tends to promote it. The flow split ratio is found to be significantly affected by the direction of the cylinder rotation. The cylinder rotation also shows a strong impact on the mean values of the hydrodynamic forces and torque. The temperature of the exiting relative streams is seen to be higher for the lower Reynolds and Prandtl numbers, and higher Bingham numbers while cylinder rotation shows a weak effect. The enthalpy gain by the main branch is found to be significantly affected by all the parameters. It has also been observed that the rate of heat transfer is higher for a clockwise rotating cylinder than in the case of an anticlockwise rotating cylinder.

Self-excited rotation and flow dynamics across a freely rotatable square cylinder confined between two parallel walls

This paper reports on a numerical investigation conducted to study the vortex-induced rotation of a square cylinder confined between two parallel walls. The fluid flow past the cylinder is simulated by solving the Navier–Stokes equations, and the cylinder’s motion is captured using Newton’s law. A dynamic mesh technique is employed to track the movement of the cylinder boundaries. The numerical model is first validated through comparisons with results in the literature. By changing the fluid velocity and wall distance, the influences of the Reynolds number (40 ≤ Re ≤ 800) and blockage ratio (0.10 ≤ br ≤ 0.55) on the rotation characteristics and flow dynamics are then revealed. Six distinct rotating modes are recognized in the present confined geometries, namely, static mode I (with θ = 0), static mode II (with θ = ±π/4), oscillating mode I (with respect to θ = 0), oscillating mode II (with respect to θ = ±π/4), an autorotating mode, and a randomly rotating mode. A phase diagram is made to describe the distribution of these rotating modes with respect to Re and br. To understand the underlying mechanisms, typical fluid–structure interaction details are presented and discussed for each rotating mode. Owing to the confinement of the parallel walls, the shear-induced torque is found to play an important role in the rotation of the cylinder, and its contribution is quantitatively compared with the pressure-induced torque.

A thermomechanical coupling in cholesteric liquid crystals: Unidirectional rotation of double-twist cylinders driven by heat flux.

We made aggregates of cholesteric liquid crystalline Cylinders with Double-Twist orientational structure (DTC) and investigated their rigid-body rotation under a temperature gradient, focusing on how the rotational speed should depend on the cylinder size. The experimental results showed that the angular velocity of the DTC aggregates linearly increased with the height of the cylinders and was inversely proportional to the base area. With a phenomenological equation, we analyzed the torque caused by the heat flux and its balance with the viscous friction, and found that the simple analysis well explained the size-dependence of the rotation of the DTC aggregates. The coupling constant between the heat flux and the torque to drive the rigid-body rotation was in the same order of magnitude as that for the director rotation.

The Theoretical and Experimental Research of a Novel Rotary Cylinder Compressor

Rotary compressor has been widely used in home air conditioning. The sealing forms of roller-vane and roller-cylinder in rotary compressor are linear sealing, resulting in large leakage and low volumetric efficiency. The performance of the compressor tempestuously reduces with the running frequency decreasing. A novel positive displacement compressor was introduced in this paper: rotary cylinder compressor. The cylinder and shaft rotate around their own axes, and the piston reciprocates relative to them, in order to implement suction and exhaust process. Further, the volume efficiency and mechanical efficiency of rotary cylinder compressor and rotary compressor was analyzed and compared theoretically. The results indicated that the sealing forms of all leaking channels in rotary cylinder compressor are face sealing, which results in less leakage and higher volumetric efficiency than linear sealing. The novel compressor has a significant advantage at the medium and low frequency, and the advantage shows more obvious with the decreasing frequency. Finally, the experimental results of the prototype fully verified the performance advantages of rotary cylinder compressor at volumetric efficiency and electrical efficiency, which was consistent with the theoretical analysis.

Taylor-Couette Column for Emulsion Liquid Membrane System: Characterisation Study

Study on the application of Taylor-Couette column for emulsion liquid membrane system has been done. To optimise extraction process under TCC, a research to investigate effect of viscosity and cylinders rotation is of important. Fluid viscosity was examined by varying volume ratio of kerosene to water. TCC was characterised to determine flow regimes, shear stress, and energy loss distribution. Volume ratio of oil to water was varied at 1:1, 1:3, 1:5, and 1:6 while inner and outer cylinders speed were maintained constant at 300 and 200 rpm, respectively. Investigation on the effect of volume ratio of oil to water towards flow regime ended to same flow regime of Featureless Turbulent. There was degradation of wall shear stress from 8.57x10-2 Pa to 7.42x10-2 Pa.

Minimal n-noids in hyperbolic and anti-de Sitter 3-space.

We construct minimal surfaces in hyperbolic and anti-de Sitter 3-space with the topology of a n-punctured sphere by loop group factorization methods. The end behaviour of the surfaces is based on the asymptotics of Delaunay-type surfaces, i.e. rotational symmetric minimal cylinders. The minimal surfaces in H3 extend to Willmore surfaces in the conformal 3-sphere S 3 = H3∪S2∪H3.

Application of improved pseudo-potential model in examination of droplet dynamic on a rotary cylinder with high-density ratio

This work examines the ability of the improved pseudo-potential model in simulating the two-phase flows on the curved surface with the angular velocity. Owing to this purpose, the movement of a two-dimensional droplet on a cylinder is investigated using the lattice Boltzmann method. To calculate the cohesion forces the model of Kupershtokh is used. Also, the distribution functions near the surface are approximated using the bounce-back method with the ability to calculate the surface velocity. After validation, results are presented for two droplets with and without initial velocity. Accordingly, the effects of the capillary number and Galilei number in the static droplet and the effect of Reynolds number and Weber number for a thrown droplet are investigated considering effects of contact angle and angular velocity. Results show that increasing the Galilei number leads to droplet dripping from the cylinder, while the reduction of the capillary number causes the droplet to oscillate before reaching the equilibrium state. Also, at low angular velocities, the dripping of the droplet is accelerated but with a further increase of the angular velocity the droplet completely covers the surface of the cylinder without detaching it. On the other hand, the inertia of the droplet causes more surface wetting, while further increase in the inertia causes the droplet to be fragmented and it removes the surface before complete surface wetting.

Fluid-structure interaction analysis of entropy generation and mixed convection inside a cavity with flexible right wall and heated rotating cylinder

The current work concentrates on the transient entropy generation and mixed convection due to a rotating hot inner cylinder within a square cavity having a flexible side wall by using the finite element method and arbitrary Lagrangian-Eulerian formulation. Effects of various relevant parameters like Rayleigh number (104⩽Ra⩽107), angular rotational velocity (-1⩽Ω⩽1), dimensionless elasticity modulus (1012⩽E⩽1015) on the convective heat transfer characteristics and entropy generation rates are analyzed for dimensionless time 10-8⩽τ⩽3.5. It is observed that various complex shaped wall deformations are established depending on the non-dimensional elastic modulus of the flexible right wall and cylinder rotation direction. The local and average Nusselt numbers rise with Ra and secondary peaks in the local Nusselt number are established for lower values of Ra. The local heat transfer along the hot cylinder does not change for the case of clockwise rotation of the heated cylinder even if there is a wall deformation in the positive x-direction. The highest average heat transfer and global entropy generation rates are achieved for the case of counter-clockwise rotation of the circular cylinder and for lower values of the flexible wall deformation.

A music-box-like extended rotational plucking energy harvester with multiple piezoelectric cantilevers

Vibrational interference has been found to incur inefficient system responses and suboptimal energy harvesting performance as the rotational frequency increases in the conventional rotational plucking energy harvester. As a result, this letter proposes a music-box-like structure of a rotational plucking energy harvester to overcome the problem by extending the rotary cylinder out of plane. A model is proposed and experimentally validated by characterizing its dynamic and energetic characteristics. Numerical analyses show that the proposed rotational plucking structure can reduce the vibrational interference and be capable of harvesting more energy at high rotational frequencies as well as extending the operating frequency range and broadening the half-power bandwidth.

Experimental investigation of energy dissipation in the multi-cylinder Couette-Taylor system with independently rotating cylinders

The paper presents the results of an experimental study of the process of dissipative heating of fluid in a multi-cylinder Couette-Taylor system with independently rotating smooth cylinders. The task was set to solve the problem of direct conversion of wind energy into heat. The flow regimes and generation of heat energy at relatively low cylinder revolutions F < 5 Hz were studied. This range corresponds to velocities of cylinder rotation, achieved by the wind turbine at moderate wind load. Rotation of only one cylinder with the braked second cylinder and their counter-rotation are considered. The second regime can be successfully implemented in the schemes of kinetic wind energy conversion without additional mechanical transmissions and reduction gears from two wind wheels. Water-glycerine solutions in a wide range of changes in their viscosity were used as a working fluid. It is shown that the specific thermal power released in the heat generator can be about 1 MW/m3, and this indicates the competitiveness of such devices among the designs of renewable energy resources.

Linear stability characteristics of the pressure-gradient driven flow confined in concentric cylinders with the rotation of outer cylinder and translation of inner cylinder

In this contribution laminar to turbulent transition is studied in a pressure gradient driven flow confined between Taylor cylinders. The outer cylinder is assumed rotating and the inner cylinder is under translational motion. In this respect, a mathematical model describing the physics of flow dynamics is presented and implemented using MATLAB. Spectral collocation approach is used to calculate the eigenvalues which predict the critical stability parameter value. The critical parameters at which the laminar to turbulent transition just starts are calculated. The neutral stability diagrams are obtained for various physical situations characterizing the limit points of damping and growth of the wave disturbances. It is observed that an increase in the swirl and translation allows the transition to start later than the classical case. However, increase in the gap width allows the transition to appear earlier than the classical case. A change in the Tollmien Schlichting mechanism is seen with the change in swirl, translation and gap width of the two cylinders. Moreover, the linear stability analysis discussed here provides a basis for the nonlinear stability analysis with the help of adjoints calculated and presented.

Convection in vertical annular gap formed by stationary heated inner cylinder and rotating unheated outer cylinder

A combined experimental and numerical study was conducted to understand the effect of rotation of outer cylinder on heat transfer from a vertical heated inner cylinder. The dimensionless analysis carried out for this problem underlines that the non dimensional heat transfer depends on the rotation parameter, radius ratio and aspect ratio. Experiments were conducted for the rotational parameter ranging from 0 ≤ ζ ≤ 526 at different heat loads, keeping the aspect ratio and radius ratio unchanged. Numerical simulations have been performed (for a wide range of rotation parameter 0 ≤ ζ ≤ 526 and fixed radius ratio) using a commercial computational fluid dynamics package ANSYS CFX 14. The heat transfer was found to increase progressively with increasing rotational parameter until a certain value of rotational parameter was reached, thereafter a sharp decay in heat transfer resulting from destabilization of flow field was observed. Three laminar heat convection modes, namely; natural, mixed and forced convection dominant, have been observed during the increasing phase of Nusselt number with rotation parameter. The transport mechanism under different heat transfer regimes was explored and discussed with the aid of numerically simulated flow and thermal fields.

Study on MHD Cylindrical Couette Flow and Rheological Properties of Some Magnetic Suspensions

The study of magnetic suspensions (MS) and magnetic field effects on their rheological properties is of evident practical importance due to its ability to orient and change their physical properties, especially their viscosity, by magnetic fields. This research presents the effect of a uniform magnetic field on the flow of MS in the annular region between two concentric cylinders. The motion of the fluid is due to the rotation of the inner cylinder with a constant angular velocity. An exact solution of the governing equations is obtained in the form of modified Bessel functions of the first and second kinds. The torque, which must be applied to the inner cylinder in order to maintain the rotation, is also calculated. The results show that as the magnetic parameter increases, the velocity profile decreases, while the torque increases due to the effect of magnetic force against the flow direction.&#x0D; In order to model the magnetoviscous effects, experiments were performed for different shear rates and different magnetic field strengths by using specially designed rheometers. The studied samples are iron oxide-water-glycerol system, ferrofluid nanoparticles, MAG DX biocompatible ferrofluid. The theoretical analysis is based on Giesekus model for MS. This model gives more accurate results and takes into account the effects of viscoelastic shear thinning characteristics. It is found that a magnetic field increases the viscosity of all suspensions under consideration. Finally, new proposed correlation for the viscosity of MS as a function of both shear rate and magnetic field has been suggested.

Features of the flow over a rotating circular cylinder at different spin ratios and Reynolds numbers: Experimental and numerical study

In this study, the characteristics of the flow in a rotating circular cylinder are investigated experimentally and numerically. The hot-wire anemometry is used to measure the mean velocity and turbulent intensity of the flow, also the k- $\omega$ SST model is used to extract the numerical results. The diameter of the cylinder is considered to be 20mm. The effect of Reynolds number $({\rm Re})$ in the range of $(5900 \leq {\rm Re} \leq 11800)$ and the spin ratio ( $ \alpha$ ) in the range of $(0 \leq \alpha \leq 0.525)$ on the characteristics of the flow wake such as time-averaged velocity, turbulence intensity, higher-order central moments of the hot-wire velocity signals (i.e. skewness factor), Strouhal number, drag coefficient and flow pattern have been investigated. According to the experimental results, the cylinder rotation has led to change in the mean and fluctuation velocity profiles and the velocity reduction region has become smaller by increasing the Reynolds number. Furthermore, the symmetry of the flow is broken as the rotation ratio increases. Also, by increasing the rotation ratio, the positions of the stagnation and separation points are changed. It is found that with increasing the rotation ratio, the drag coefficient and the velocity reduction parameters are decreased.

AAV2/DJ-mediated alpha-synuclein overexpression in the rat substantia nigra as early stage model of Parkinson's disease.

Parkinson's disease (PD) is pathologically characterized by the progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) and alpha-synucleinopathy. We mimic the disease pathology with overexpression of either the human α-syn wildtype (α-syn-WT) or E46K mutant form (α-syn-E46K) in DA neurons of the SNpc in adult rats using AAV2/DJ as a viral vector for the first time. Transduction efficiency was compared to an equal virus titer expressing the green fluorescent protein (GFP). Motor skills of all animals were evaluated in the cylinder and amphetamine-induced rotation test over a total time period of 12weeks. Additionally, stereological quantification of DA cells and striatal fiber density measurements were performed every 4weeks after injection. Rats overexpressing α-syn-WT showed a progressive loss of DA neurons with 40% reduction after 12weeks accompanied by a greater loss of striatal DA fibers. In contrast, α-syn-E46K led to this reduction after 4weeks without further progress. Insoluble α-syn positive cytoplasmic inclusions were observed in both groups within DA neurons of the SNpc and VTA. In addition, both α-syn groups developed a characteristic worsening of the rotational behavior over time. However, only the α-syn-WT group reached statistically significant different values in the cylinder test. Summarizing these effects, we established a motor symptom animal model of PD by using AAV2/DJ in the brain for the first time. Thereby, overexpressing of α-syn-E46K mimicked a rather pre-symptomatic stage of the disease, while the α-syn-WT overexpressing animals imitated an early symptomatic stage of PD.

Photo-Controllable Rotation of Cholesteric Double-Twist Cylinders

We fabricated aggregates of cholesteric cylinders coexisting with the isotropic phase and investigated their dynamics under a temperature gradient. Each constituent cylinder possessed the double-twist (DT) structure, and when a heat flux was applied, the whole aggregates rotated as a rigid-body without changing the DT orientation. The angular velocity was proportional to the heat flux and the rotational direction was determined by the molecular chirality and the flux direction. The result suggests that the rigid-body rotation was driven by the thermomechanical cross-correlation in chiral LCs. We also succeeded in switching the rotation by changing the illumination onto the sample.