Cylindrical Fluid Research Articles

Pressure-Based and Potential-Based Differential Quadrature Procedures for Free Vibration of Circular Plates in Contact with Fluid

The differential quadrature method (DQM) has been so far applied to a wide variety of fluid and/or structural problems. The results of many researchers reveal that the DQM is computationally efficient and is applicable to a large class of boundary value problems. However, there is little information about its applications to fluid-structure interaction problems. Therefore, the purpose of this paper is to provide some information in this area and to develop procedures based on the DQM for the numerical solution of fluid-structure interaction problems. First, the governing partial differential equations of motion of the structure and fluid are discretized separately using the DQM. Then, by applying the boundary condition at fluid-structure interface, the governing eigenvalue equations of the coupled system are obtained which can then be solved for the eigenvalues of the system. The applicability of the proposed procedures is shown herein through the free vibration analysis of thin circular plates in contact with a cylindrical fluid-filled cavity. Issues related to the implementation of the regularity conditions at the center of the circular plate and the central line of the cylindrical cavity are addressed. Two new regularity conditions are proposed for the circular cylindrical fluid domain. The accuracy and efficiency of the proposed procedures are demonstrated by comparing the obtained results with those available in the literature. It is shown that highly accurate converged results can be obtained by the proposed procedures using a small number of grid points. Three new dimensionless parameters and variables are also introduced for the free vibration of the coupled system. The influences of these parameters on dynamic behavior of the system are studied.

Convective heat transfer in a rotating horizontal cylindrical fluid layer

This paper describes the thermal convection and heat transfer in a cylindrical fluid layer rotating around a horizontal axis, with various constant temperatures set at the layer boundaries. The influence of the rotational speed of the cylindrical fluid layer on the convective heat transfer in this layer is studied. The study results are presented as functions of dimensionless parameters that characterize the action of two convective mechanisms: centrifugal and thermal-oscillatory. It is shown that, with low rotational speed, the heat transfer is determined by quasistationary gravitational convection.

Fluid-structure interaction between an incompressible, viscous 3D fluid and an elastic shell with nonlinear Koiter membrane energy

The long-time existence of a weak solution is proved for a nonlinear, fluid-structure interaction (FSI) problem between an incompressible, viscous fluid and a semilinear cylindrical Koiter membrane shell with inertia. No axial symmetry is assumed in the problem. The fluid flow is driven by the time dependent dynamic pressure data prescribed at the inlet and outlet boundaries of the 3D cylindrical fluid domain. The fluid and the elastic structure are fully coupled via continuity of velocity and continuity of normal stresses. Global existence of a weak solution is proved as long as the lateral walls of the cylinder do not touch each other. The main novelty of the work is the nonlinearity in the structure model: the model accounts for the fully nonlinear Koiter membrane energy, supplemented with a small linear fourth-order derivative term modeling the bending rigidity of shells. The existence proof is constructive, and it is based on an operator splitting scheme. A version of this scheme can be implemented for the numerical simulation of the underlying FSI problem by extending the FSI solver, developed by the authors in [5], to include the nonlinearity in the structure model discussed in this manuscript.

Конвективный теплоперенос во вращающемся горизонтальном цилиндрическом слое жидкости

Конвективный теплоперенос во вращающемся горизонтальном цилиндрическом слое жидкости

Gravitational collapse of dissipative fluid as a source of gravitational waves

Gravitational collapse of cylindrical anisotropic fluid has been considered in analogy with the work of Misner and Sharp. Using Darmois matching conditions, the interior cylindrical dissipative fluid (in the form of shear viscosity and heat flux) is matched to an exterior vacuum Einstein–Rosen space–time. It is found that on the bounding 3-surface the radial pressure of the anisotropic perfect fluid is linearly related to the shear viscosity and the heat flux of the dissipative fluid on the boundary. This non-zero radial pressure on the bounding surface may be considered as the source of gravitational waves outside the collapsing matter distribution.

Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water.

The test-area (TA) perturbation approach has been gaining popularity as a methodology for the direct computation of the interfacial tension in molecular simulation. Though originally implemented for planar interfaces, the TA approach has also been used to analyze the interfacial properties of curved liquid interfaces. Here, we provide an interpretation of the TA method taking the view that it corresponds to the change in free energy under a transformation of the spatial metric for an affine distortion. By expressing the change in configurational energy of a molecular configuration as a Taylor expansion in the distortion parameter, compact relations are derived for the interfacial tension and its energetic and entropic components for three different geometries: planar, cylindrical, and spherical fluid interfaces. While the tensions of the planar and cylindrical geometries are characterized by first-order changes in the energy, that of the spherical interface depends on second-order contributions. We show that a greater statistical uncertainty is to be expected when calculating the thermodynamic properties of a spherical interface than for the planar and cylindrical cases, and the evaluation of the separate entropic and energetic contributions poses a greater computational challenge than the tension itself. The methodology is employed to determine the vapour-liquid interfacial tension of TIP4P/2005 water at 293 K by molecular dynamics simulation for planar, cylindrical, and spherical geometries. A weak peak in the curvature dependence of the tension is observed in the case of cylindrical threads of condensed liquid at a radius of about 8 Å, below which the tension is found to decrease again. In the case of spherical drops, a marked decrease in the tension from the planar limit is found for radii below ∼ 15 Å; there is no indication of a maximum in the tension with increasing curvature. The vapour-liquid interfacial tension tends towards the planar limit for large system sizes for both the cylindrical and spherical cases. Estimates of the entropic and energetic contributions are also evaluated for the planar and cylindrical geometries and their magnitudes are in line with the expectations of our simple analysis.

Acoustic microfluidics: Capillary waves and vortex flows in the cylindrical volume of a fluid drop

We calculate the field of radiation forces in a cylindrical fluid layer on a solid substrate formed as a result of the action on a fluid of a capillary wave propagating from the axis along a free surface. We study the structure of acoustic flows excited by the radiation forces. We discuss the action of flows on small-sized particles and the possibilities of these particles to form ordered structures.

Gravitational collapse of cylindrical anisotropic fluid: a source of gravitational waves

The present work deals with dynamics of gravitational collapse with cylindrical symmetry as developed by Misner and Sharp. The interior collapsing anisotropic cylindrical perfect fluid is matched to an exterior vacuum cylindrically symmetric space-time due to Einstein–Rosen using the Darmois matching conditions. It is found that the radial pressure of the anisotropic perfect fluid is non-zero on the boundary surface and is related to the components of shear viscosity. As a result, there is formation of gravitational waves outside the collapsing matter.

A modular, operator‐splitting scheme for fluid–structure interaction problems with thick structures

SUMMARYWe present an operator‐splitting scheme for fluid–structure interaction (FSI) problems in hemodynamics, where the thickness of the structural wall is comparable to the radius of the cylindrical fluid domain. The equations of linear elasticity are used to model the structure, while the Navier–Stokes equations for an incompressible viscous fluid are used to model the fluid. The operator‐splitting scheme, based on the Lie splitting, separates the elastodynamics structure problem from a fluid problem in which structure inertia is included to achieve unconditional stability. We prove energy estimates associated with unconditional stability of this modular scheme for the full nonlinear FSI problem defined on a moving domain, without requiring any sub‐iterations within time steps. Two numerical examples are presented, showing excellent agreement with the results of monolithic schemes. First‐order convergence in time is shown numerically. Modularity, unconditional stability without temporal sub‐iterations, and simple implementation are the features that make this operator‐splitting scheme particularly appealing for multi‐physics problems involving FSI. Copyright © 2013 John Wiley & Sons, Ltd.

An Inchworm Bionic Stepping Actuator Based on PZT/ER Hybrid Dive and Control

An unconventional inchworm stepping actuator based on bionics is presented, which consists of driving unit (PZT stack pump), fluid control unit (ER fluids valve), actuating mechanism (precision hydraulic cylinder). As a new type of precision force/ displacement driving and positioning system, it inherits the advantages of conventional inchworm actuators, and also has its own remarkable characteristics, such as that stepping displacement can be adjusted precisely through varying the working voltage and frequency, etc. The driving unit is actuated jointly by double PZT stacks; Multi-channel parallel cylindrical ER fluids valve is designed as the control valve. In the lab, the inchworm bionic stepping actuator based on PZT/ ER hybrid dive and control is designed and manufactured, and the related performances are testedsystematically. The maximum driving force reaches 49N, and the step size and driving speed VS the working voltage shows a good linear relationship under three different signal waveforms. At the same time, in the frequency range less than 40Hz, the driving speed VS the frequency approximately shows a linear relationship. When working voltage is 100V and rectangle wave signal inputs, the step size reaches 12.6μm. When the working voltage and frequency is 100V, 40Hz, respectively, the driving speed reaches 420μm/s. The maximum drive speed of test prototype reaches 1051 μm/s, when working in frequency 75 Hz. The systematic test shows that the method using PZT and ER hybrid drive and control technology to develop a new type of inchworm bionic stepping actuator is feasible, which provides a reference for the future development of new type of actuator.

Nonlinear stability analysis for a jet moving in a material medium collinearly to an electrostatic field

Analytically, in the second order approximation, the nonlinear internal resonance energy exchange between waves on the surface of a cylindrical incompressible dielectric fluid jet that moves relative to a material medium in the longitudinal electrostatic field is investigated.

MR 댐퍼를 이용한 전자제어 현가장치의 승차감 평가

This paper presents design and control of electronic control suspension(ECS) equipped with controllable magnetorheological(MR) damper for passenger vehicle. In order to achieve this goal, a cylindrical type MR fluid damper that satisfies design specification of a middle-sized commercial passenger vehicle is proposed. After manufacturing the MR damper with design parameters, their field-dependent damping forces are experimentally evaluated and compared with those of a conventional damper. A quarter-vehicle MR ECS system consisting of sprung mass, spring, tire, controller and the MR damper is established in order to investigate the ride comfort performances. On the basis of the governing equation of motion of the suspension system, five control strategies(soft, hard, comfort, sport and optimal mode) are formulated. The proposed control strategies are then experimentally realized with the quarter-vehicle MR ECS system. Control performances such as vertical acceleration of the car body and tire deflection are evaluated in frequency domains on random road condition. In addition, performance comparison of WRMS(weighted root mean square) of the quarter-vehicle MR ECS system on random road are undertaken in order to investigate ride comfort characteristics.

Resonant Scattering and Absolute Phase Applied to Cylindrical and Spherical Hollow Fluids Embedded in an Elastic Medium: A Numerical Simulation

This paper is based on the study of acoustic scattering classic RST, in which it was introduced the method of MRST (multichannel resonant scattering theory) to study the problem of interaction of acoustic waves normal incidence in environments consisting of a biphasic isotropic elastic matrix in which is inserted a fluid inclusion (cylindrical or spherical). Initially we implement the transition matrix S containing the mode n of the longitudinal (L) and transverse (T) of the wave in the elastic medium. The isolation of resonances characteristic of the fluid inclusion is done via the S-matrix factorization as a product of the matrix of soft bottoms no resonant matrix and resonances. To improve the localization of the resonances we undertake a study of the absolute phase in connection with MRST. A numerical simulation of cavity fluid (water) cylindrical and spherical copper in a matrix, showed the effectiveness of the absolute phase spectra for the exact determination of the resonances.

Cylindrical Fluid Membranes and the Evolutions of Planar Curves

Cylindrical Fluid Membranes and the Evolutions of Planar Curves

Study of vorticity and helicity distribution in advective flow with secondary structures

The distribution of vorticity and helicity in a stationary cylindrical fluid layer locally heated at its center is studied numerically and experimentally. Such localized heating leads to the generation of a large-scale flow in the form of a toroidal convective cell. In the heating area, small-scale secondary flows and local upward jets appear. The goal of this study is to investigate helicity and vorticity structures produced by the interaction between the shear flow and the upward jets. Formation and evolution of vortex structures in the boundary layer of advective flows are considered in detail. It is shown that the interaction of convective jets with the advective flow does not give rise to substantial non-zero mean helicities and the vertical component of vorticity.

Modeling of annular-laser-beam-driven plasma jets from massive planar targets

AbstractProduction of sharply collimated high velocity outflows – plasma jets from massive planar targets by a single laser beam at PALS facility is clarified via numerical simulations. Since only a few experimental data on the intensity distribution in the interaction beam near the focus are available for the PALS facility, the laser beam profile was calculated by a numerical model of the laser system and the interaction optics. The obtained intensity profiles are used as the input for plasma dynamic simulations by our cylindrical two-dimensional fluid code PALE. Jet formation due to laser intensity profile with a minimum on the axis is demonstrated. The outflow collimation improves significantly for heavier elements, even when radiative cooling is omitted. Using an optimized interaction beam profile, a homogeneous jet with a length exceeding its diameter by several times may be reliably generated for applications in laboratory astrophysics and impact ignition studies.

Formation of columnar baroclinic vortices in thermally stratified nonlinear spin-up

AbstractWe investigate the mechanisms that affect the formation of columnar vortices for spin-up in a cylinder where the temperatures at the horizontal walls are prescribed. Numerical results from the three-dimensional Navier–Stokes equations show that a short-lived instability, suppressed by the combined effect of rotation and stratification, generates small temperature variations in the azimuthal direction. Temperature-gradient anomalies produce vorticity, and these vortices stir the fluid at the interface of the central vortex core thus reinforcing the temperature gradients. For sufficiently strong temperature gradients, the central vortex core breaks up into several columnar vortices. It is found, in particular, that small aspect ratios (height over radius of the cylindrical fluid layer) $\Gamma = 1, 2$ tend to inhibit the instability, while larger ones, $\Gamma = 3. 3$, have the opposite effect. The main source of instability is the baroclinic vorticity production and not the presence of a solid sidewall since, counter-intuitively, the flow is more unstable for a free-slip boundary than for a no-slip one. Finally the effect of the temperature boundary conditions (isothermal versus adiabatic) on the horizontal boundaries has been investigated. The adiabatic boundaries help to preserve for longer times the sloping density interfaces that feed, with their potential energy, the baroclinic vorticity production; this results in more unstable flows.

Cylindrical Magnetorheological Fluid Variable Transmission Controlled by Shape-Memory Alloy

Centrifugal fan is an important component of a ventilation system in a nuclear power plant. In this paper, we proposed a magnetorheological speed-adjustment system controlled by shape-memory alloy for centrifugal fan. A theoretical analysis of the effect of the applied magnetic field on the viscoplastic flow between two cylinders in the speed-adjustment system is presented. The expressions for the velocity in viscoplastic flow and the torque transmitted by MR fluids are derived. A sliding mode SMA switch is proposed to modify the magnetic field acting on working gap under thermal effect. The results indicate that with the increases of applied magnetic field, the torque transmitted by MR fluid goes up rapidly.

Experimental studies of surface waves inside a cylindrical container

We experimentally investigate the dynamics of surface waves excited by oscillations from a cylindrical sidewall. Particle-imaging-velocimetry measurements with fluorescent particles were used to determine the flow patterns near the sidewall of the cylindrical fluid container and to identify the locations of the evolving air–water interfaces. The high-frequency wall oscillations created four jets that originate at the cylindrical sidewall. Four vortex streets shed from the jets propagate from the sidewall to the centre of the container and subsequently excite a low-frequency gravity wave. The interaction between this gravitational surface wave and the high-frequency capillary waves was found to be responsible for creating droplet splash at the water surface. This phenomenon was first described as ‘Long-Xi’ or ‘dragon wash’ in ancient China. The physical processes for generating the droplet ejection, including the circular capillary waves, azimuthal waves, streaming jets and low-frequency gravity waves, are described in this paper.

Formation of differential rotation in a cylindrical fluid layer

The formation of differential rotation in a rotating cylindrical layer heated locally is investigated numerically. In the simulations performed, geometric parameters (the layer height and radius and the heating area), the kinematic viscosity, the heat flux, and the angular velocity of the cylinder were varied. Integral characteristics of differential rotation are obtained. The dependence of the relative angular momentum of the layer on various parameters is investigated.