Oscillations Of Liquid Research Articles

Internal resonance of nonlinear liquid surface oscillation in a cylindrical tank with an eccentric core barrel

Internal resonance of nonlinear liquid surface oscillation in a cylindrical tank with an eccentric core barrel

Influence of low-frequency oscillatory motion on particle settling in Newtonian and shear-thinning non-Newtonian fluids

An experimental study is performed to observe the effect of vertical fluid oscillations on the mean settling velocity of single spherical glass particles released into mixtures of water and polymeric fluids which exhibit shear-thinning behavior for “non-zero” shear rates. The influence of the shear region in shear-thinning non-Newtonian fluids on the settling rate of spherical particles at different oscillatory conditions is also discussed.A transparent, U-shaped pipe with a circular cross-section of 50 mm inner diameter is used. Visualizations are captured along one of the two vertical branches of the pipe while a piston generates pressure gradient oscillations in the other branch at three different low frequencies (0.25, 0.5, and 0.75 Hz). Tests at still fluid are also carried out for comparison. Four fluids are considered: water and three mixtures of water-based polymeric solutions which provide the mixture with viscoelastic properties and shear-thinning behavior. Spherical particles of diameter d = 1 mm, 2 mm, and 3 mm are released at three different distances from the center of the cross-section: 0, 0.5 R, and 0.8 R, where R is the pipe radius. Particles are released one-by-one and their trajectory is captured from the high-speed camera.The settling velocity was found smaller if particles were released close to the pipe wall, independently on the rheology of the fluid. A significant reduction of the settling velocity was observed in the presence of an oscillatory flow when a fluid characterized by shear-thinning viscosity is used. According to the results, it was found that the liquid oscillations brought a decrement of up to 7% in the average settling velocity in Newtonian fluid and a 23% decrement of that in non-Newtonian fluids. Moreover, when the fluid oscillates, the shear-layer associated with the particle wake and the pipe wall does not result in any reduction of the settling velocity. In other words, the effect of the near-wall shear layer, which reduces the viscosity of shear-thinning fluids, dominates over the other effects that would not keep the particle longer in suspension.

Optical characterization of methanol compression-ignition combustion in a heavy-duty engine

In the search for renewable fuels, there are very few candidates as compelling as methanol. It can be derived from refuse material and industrial waste, while the infrastructure exists worldwide to support broad and fast adoption, potentially even as a “drop-in” fuel for existing vehicles with only minor modifications. The most efficient engines currently available are compression-ignition engines, however they often come with high emissions or compromises like the soot-NOx trade-off. Methanol however, is a low sooting fuel that can potentially be used in such engines despite its high resistance to auto-ignition and reduce emissions while maintaining high engine efficiency. Due to the auto-ignition resistance, few studies of methanol compression-ignition exist and even fewer are conducted in an optically accessible engine. Here, two cases of premixed combustion and two of spray-driven combustion of methanol are studied in a Heavy-Duty optically accessible engine. Ignition and combustion propagation are characterized with a combination of time-resolved natural flame luminosity measurements and single-shot, acetone fuel-tracer, laser induced fluorescence. Additionally, Mie-scattering is used to identify the interaction between liquid spray and ignition sites in spray-driven methanol combustion. Results show that methanol combusts drastically different compared to conventional fuels, especially in spray-driven combustion. The evaporative cooling effect of methanol appears to play a major role in the auto-ignition characteristics of the delivered fuel. Ignition sites appear right at the end of injection when the evaporative cooling effect is withdrawn or at liquid length oscillations where, again the effect is momentarily retracted. To the authors’ knowledge, this has not been documented before.

Mathematical model of oscillations of a railway tank car with partial fillingunder shunting collision

This article is devoted to simulating longitudinal vibrations of the tank car in case of partial filling with liquid during shunting collision. A brief overview of studies of the movement of solid bodies with liquid was performed. The design scheme of cars, represented by a 4-mass system with elastically-dissipative connections, has been developed. A system of differential equations of car motion according to the main equation of dynamics has been compiled. The mathematical model of liquid cargo oscillations based on shallow water theory is derived. In integration, the characteristic method and Euler method are applied. It is envisaged to transfer parameters between the mathematical model of cars (tank acceleration) and the mathematical model of liquid load (pressure forces on the bottoms). The methodology is implemented in the C++ Builder programming environment. According to the developed method, a study of the shunting collision with the tank at incomplete filling was carried out. The dependence of the reaction in the automatic coupling on time has two bursts. The maximum reaction is also dependent on the impact rate and the degree of filling of the tank.

Liquid Sloshing in Partially Filled Capsule Storage Tank Undergoing Gravity Reduction to Low/Micro-Gravity Condition

Liquid sloshing in storage tanks is of critical concern for the fluid management in space. In the present study, oscillation of liquid in a partially filled capsule storage tank was numerically studied using the volume of fluid method and taking into account the dynamic contact angle. The filling ratios of tank ranging from 10% to 90% and the gravity levels of 10−3 g0 and 0 g0 were considered as the controlling variables. The temporal evolution of characteristic points of free surface and the law of oscillation frequencies were analyzed. The results show that for different filling ratios, the oscillations of free surfaces present different damping types, in which the small and large filling ratios correspond to the underdamping and the intermediate filling ratios to the critical damping. The present study provides fundamental insights into the free surface oscillations depending on the filling ratios and residual gravity level, which is useful for the corresponding utilization in space.

Synchronization of chemo-mechanical oscillators

The synchronization of chemically driven oscillators plays a crucial role in various biological motions. An artificial model system of these chemo-mechanical oscillators is proposed in this study. The oscillator is composed of three liquid layers (oil/water/oil), which exhibit a back and forth motion in a glass tube. This motion is caused by the chemical reaction between a water-soluble surfactant and oil-soluble anions. The frequency is unique for an individual experimental setup because it depends on the surface state of the glass sensitively. When the glass tube with the liquid oscillator is placed on a plate with mechanical vibration, the frequencies of the oscillator and mechanical vibration become similar within a certain frequency range of mechanical vibration. When two or more glass tubes are placed in a boat floating on a water surface, all frequencies agree with each other by the joggling motion of the boat. The entrainment into the external vibration and mutual synchronization on the boat are explained by a simple mathematical model. The proposed chemo-mechanical oscillator may be used as a primitive model system for studying the interplay of macroscopic motion and molecular scale processes that control chemically driven motion.

Transition from Exponentially Damped to Finite-Time Arrest Liquid Oscillations Induced by Contact Line Hysteresis.

To clarify the role of wetting properties on the damping of liquid oscillations, we studied the decay of oscillations of liquid columns in a U-shaped tube with controlled surface conditions. In the presence of sliding triple lines, oscillations are strongly and nonlinearly damped, with a finite-time arrest and a dependence on initial amplitude. We reveal that contact angle hysteresis explains and quantifies this solidlike friction.

Charge oscillations in ionic liquids: A microscopic cluster model.

In spite of their enormous applications as alternative energy storage devices and lubricants, room-temperature ionic liquids (ILs) still pose many challenges from a pure scientific viewpoint. We develop an IL microscopic theory in terms of ionic clusters, which describes the IL behavior close to charged interfaces. The full structure factor of finite-size clusters is considered and allows us to retain fine and essential details of the system as a whole. Beside the reduction in the screening, it is shown that ionic clusters cause the charge density to oscillate near charged boundaries, with alternating ion-size thick layers, in agreement with experiments. We distinguish between short-range oscillations that persist for a few ionic layers close to the boundary, as opposed to long-range damped oscillations that hold throughout the bulk. The former can be captured by finite-size ion pairs, while the latter is associated with larger clusters with a pronounced quadrupole (or higher) moment. The long-wavelength limit of our theory recovers the well-known Bazant-Storey-Kornyshev (BSK) equation in the linear regime, and elucidates the microscopic origin of the BSK phenomenological parameters.

Oscillations of a Stratified Liquid Partially Covered with Ice (General Case)

We study the problem of small motions of an ideal stratified liquid whose free surface consists of three regions: liquid surface without ice, a region of elastic ice, and a region of crumbled ice. The elastic ice is modeled by an elastic plate. The crumbled ice is understood as weighty particles of some matter floating on the free surface. Using the method of orthogonal projection of boundary conditions on a moving surface and the introduction of auxiliary problems, we reduce the original initial boundary value problem to an equivalent Cauchy problem for a second-order differential equation in a Hilbert space. We obtain conditions under which there exists a strong (with respect to time) solution of the initial boundary value problem describing the evolution of the hydrodynamic system under consideration.

Simultaneous in operando monitoring of keyhole depth and absorptance in laser processing of AISI 316 stainless steel at 200 kHz

The formation of keyholes during high-irradiance laser-metal interaction is the complex, multiphysics phenomenon that underpins industrial processes such as laser-based additive manufacturing, laser welding, and laser cutting. The complex dynamics of energy coupling in keyhole formation are not well understood, and the energy absorptance in these processes are often assumed to be constant. Therefore, we implement two state-of-the-art measurement techniques in operando to simultaneously measure keyhole depth using inline coherent imaging and laser energy absorptance using integrating sphere radiometry at imaging rates of 200 kHz. Results directly reveal the time evolution of cavity-enhanced absorptance in these keyholes generated by the laser-metal interaction. For stationary irradiance on AISI 316 stainless steel, we find that processing in an argon-rich environment compared to air reduces coupling efficiency by 50 % ± 11 % in conduction, 27 % ± 2 % in transition, and 8 % ± 3 % in keyhole mode. High imaging rates allow clear observation of liquid surface oscillations and corresponding changes to absorptance, declining from 15 kHz to 10 kHz over the first 10 ms of the spot weld.

ВЕРИФІКАЦІЯ АЛГОРИТМУ КЕРУВАННЯ РЕЗЕРВУАРАМИ З РІДИНОЮ НА ОСНОВІ КОМПЕНСАЦІЇ СИЛОВОГО ВІДГУКУ В РІЗНИХ ДІАПАЗОНАХ ПРОЯВУ НЕЛІНІЙНОСТЕЙ

Problem about motion of a reservoir with liquid with a free surface is considered based on the compensation of a force response of the liquid on reservoir walls. Such an approach is selected since usual methods of control of mechanical system motion are mostly intended for linear systems of relatively small dimension. However, models of dynamics of the combined motion of reservoirs with liquid are described with relatively high-dimensional nonlinear systems ordinary differential equations. For obtaining the mathematical model of combined motion of a reservoir with liquid with a free surface we use the Hamilton–Ostrogradskiy variational principle, for which it is possible to determine analytically all internal forces of interaction of system component parts. Namely using this algorithm, we determine the main vector of forces of the liquid pressure on reservoir walls (force response of liquid). The algorithm of the motion control of the reservoir with liquid is based on the inclusion of the compensation of the liquid force response to controlling actions, this reduces the motion of the system reservoir–liquid, where the effect of forces from oscillating liquid on the reservoir motion is eliminated. This algorithm was tested for problems of impulse and vibration disturbance of the translational motion of the system in the horizontal plain. We consider the disturbance of the system motion by a force rectangular impulse applied to the reservoir wall, the duration of the impulse is lesser than a quarter of the period of a liquid free oscillations according to the first normal mode. Amplitudes of the impulse were selected with the purpose of analysis of the behavior of the controlled system in different ranges of manifestation of nonlinearities. We state the problem to verify the accuracy of this algorithm for three ranges of manifestation of nonlinear properties in the system, namely, for the linear range (amplitudes of waves on a free surface h do not exceed 0,1 of the radius of a free surface (  <0,1R); for the weakly nonlinear range (  <0,2R) and for the strongly nonlinear range with maximum amplitudes of waves about  =0,32R. Numerical modeling enables the determination of errors of developed algorithm, which does not exceed 0,5 %, although they insignificantly increase with the increase of amplitudes of oscillations on a free surface of liquid. At the same time perturbations on a free surface of liquid for the controlled motion are always greater than for the uncontrolled motion.

ХАРАКТЕР ПРОЯВУ НЕЛІНІЙНОСТЕЙ ПРИ ВІБРАЦІЙНОМУ ЗБУДЖЕННІ РУХУ ЕЛІПСОЇДАЛЬНОГО РЕЗЕРВУАРА З РІДИНОЮ ІЗ ВІЛЬНОЮ ПОВЕРХНЕЮ

The problem with vibration disturbance of the reservoir of ellipsoidal shape, partially filled with a liquid, is under consideration. For the construction of the model, we use the before developed method, based on the use of non-Cartesian parametrization of the domain, occupied by a liquid. And the method of the auxiliary domain for satisfying boundary conditions on tank walls above the unperturbed free surface of a liquid, where the liquid can pass in its perturbed motion. The liquid is considered as ideal incompressible. The mathematical model of the system is constructed based on the variational formulation of the problem in the form of the Hamilton–Ostrogradskiy principle. The motion of a liquid free surface is given in the form of decomposition with respect to normal modes of oscillations. Amplitude parameters of oscillations of a liquid free surface together with parameters of the translational motion of the reservoir form a complete independent system of parameters, for which the resolving system of ordinary differential equations is constructed. The constructed model includes nonlinear properties of the system and corresponds to the model of the combined motion of the liquid with the reservoir. According to its structure, the model has considerable similarities with the case of the cylindrical reservoir. The practical implementation of the method is done for vibration disturbance of the system motion in the horizontal plane for the case of extended and compressed ellipsoidal reservoirs. The analysis of the character of manifestation of the dynamical behavior of the system in different ranges of frequencies of motion disturbance shows that mainly this system behaves as a system with the soft type of nonlinearities. The system output to the steady mode of oscillations is not observed. Modulation of oscillations of a liquid free surface is considerably manifested for most modes. Increased attention is paid to the study of regularities of variation of a period of the oscillation modulation. It was ascertained that due to compression of the spectrum of liquid oscillations with the increase of the wavenumber, the simultaneous considerable effect of several frequencies is manifested in the system reservoir–liquid, which leads to complex modulation envelope lines.

Analysis of the influence the liquid cargo oscillations in a semi-trailer tank on the wheeled tractor motion indicators

A large amount of transport work of a wheeled tractor accounts for the transportation of liquid cargoes by tractor tanks. These tanks are different from road and rail tank containers with no internal partitions that would quench fluid fluctuations. The constant tendency to increase such freight transportation causes the appearance of negative factors affecting the driver's health and economic performance of the tractor. In the study of the influence of dynamic load on fuel efficiency, a mathematical model was used, which is capable of simulating engine operation at partial load and speed modes

On the Stability of the rotation under the action of constant momentum Lagrangian top with perfect fluid in a resisting medium

The rotation around a fixed point of a heavy dynamically symmetric solid body with an arbitrary asymmetric cavity completely filled with an ideal in-compressible liquid is considered. The stability of a uniform rotation of a Lagrang' top with the ideal liquid in a resisting medium under condition of a given constant moment is investigated. The equation of the perturbed motion of the Lagrang' top with the ideal liquid is presented. It is proved the follow-ing: the asymptotic stability of uniform rotation for an ellipsoidal cavity will be only for a compressed ellipsoidal cavity. It has been observed that most practically important cases consider the main effect of the ideal liquid influence on the motion of a solid can be researched by means of considering only the fundamental tone of the liquid oscillation. Conditions of uniform rotation asymptotic stability in a resistive medium under the action of the Lagrange top' constant moment with an arbitrary axisymmetric cavity containing an ideal liquid are obtained. Stability conditions are derived with provisions for the main and additional tones of liquid oscillations. The heavy solid body with the fixed-point value is ex-posed to the action of a constant moment in the inertial coordinate system. Analytic and numerical investigations of the main and additional tones of liquid oscillations influence, over-turning, restoring, dissipative and constant moments on the conditions of the asymptotic stability of the uniform rotation of the Lagrange top with an ideal liquid are carried out. It is stated the following: cubic and square inequalities presented in the paper are conditions of asymptotic stability if the basic tone of liquid fluctuations will be mentioned. Stability region numerical studies have been carried out on the example of an ellipsoidal cavity. It is presented that increasing of the equatorial moment of inertia of the solid body de-creases its stability region as well as the increasing of the solid body inertia axial moment in-creases the last one.

Free and Forced Oscillations of Magnetic Liquids Under Low-Gravity Conditions

Abstract The sloshing of liquids in microgravity is a relevant problem of applied mechanics with important implications for spacecraft design. A magnetic settling force may be used to avoid the highly non-linear dynamics that characterize these systems. However, this approach is still largely unexplored. This paper presents a quasi-analytical low-gravity sloshing model for magnetic liquids under the action of external inhomogeneous magnetic fields. The problems of free and forced oscillations are solved for axisymmetric geometries and loads by employing a linearized formulation. The model may be of particular interest for the development of magnetic sloshing damping devices in space, whose behavior can be easily predicted and quantified with standard mechanical analogies.

Pulsation Characteristics of Corona Discharge in Electrohydrodynamic Process Using Ionic Liquid

In this study, the pulse phenomenon is found in the electrohydrodynamic (EHD) process using an ionic liquid, which is similar to other liquids, but there are significant differences in pulse characteristics. The frequency, waveform, charge, and images of the pulse in the EHD process with the ionic liquid are studied experimentally. The results show that the pulse process is divided into two stages: a low-frequency pulse stage and a high-frequency pulse stage. We propose that the pulse is caused by the air corona discharge and the frequency is influenced by the anchoring radius of liquid oscillation in the electric field. The different anchoring radii of the two stages are the main reason for the obvious difference in the frequency. The main difference between the ionic liquid and other solutions is the conductivity and the surface tension coefficient, which is the cause of corona discharge rather than electrospray.

Cryogenic propellant recirculation for orbital propulsion systems

In the next generation orbital propulsion systems, cryogenic propellant recirculation will be applied to reduce engine chill-down consumption by recirculation chill-down and to achieve efficient propellant utilization by active propellant cooling. To understand tank-to-tank recirculation, a recirculation test campaign was conducted using liquid nitrogen as a working fluid. An electrically-driven recirculation pump developed for this experiment has bleed holes on the impeller to bleed vapor rather than liquid so that it works under two-phase flow operation. In addition to this pump, the test facility includes a 600 mm-diameter cryogenic tank, void fraction meters, an ultrasonic flow meter, and temperature and pressure sensors. The tank has a double layered window on the top to visually observe the return flow inside. The void fraction meters and ultrasonic flow meter were used to evaluate the two-phase mass flow rate. The tests were carried out in two different return port positions in the tank, the side and bottom return port cases, and the results indicated that the pressure and temperature behaviors in the tank were affected by the return flow rate, phase of the return flow and the return port position in the tank. In the side return port case, the flow returned to tank ullage and less disturbance of liquid in the tank was observed at a low flow rate while strong mixing of the liquid was observed at a high flow rate. The tank pressure was affected by the phase of return flow rather than the ullage temperature. In the bottom return port case, less disturbance was observed in vapor return flow, while in two-phase or liquid return flow, strong disturbance was observed even at lower flow rate. The tank pressure in this case was similar to that in the side return port case: the vapor return increased the pressure while the two-phase or liquid return decreased the pressure. The bleed holes on the impeller helped the inlet flow to recover to subcooled liquid condition and to keep the impeller working under saturation condition at the inlet although the recirculation system suffered decreased pump head, loss of liquid and unsteady oscillation of pump head and flow rate.

Chaos under interface oscillations during boiling and sea surface agitation

Results of investigation of the phase interface fluctuations at film and bubble boiling and sea surface agitation are presented. The vapor film thickness and vapor bubble growing on the wall were determined with the aid of laser diagnostics. Oscillations of a growing vapor bubble and simultaneous pressure oscillations in liquid were detected using optical (laser) and acoustic diagnostics. For the very first time volume and shape oscillations of a vapor bubble growing on a wall were determined. An approached model of volume oscillations of a vapor bubble, growing on a heat transfer surface is presented basing on experimental data. The system of model equations and bubble dynamics were presented considered, accounting simultaneous evaporation and condensation at the interface. It has been found that the growth of a vapor bubble is accompanied by its volume oscillations, which become chaotic under certain circumstances.

Dynamics of an Acoustically Excited Gas Cavity Attached to a Rigid Surface

Expansion, collapse and impact of a gas bubble onto a rigid wall are numerically studied. The bubble is adjacent to the wall, it is initially spherical, at the equilibrium state. Its dynamics results from harmonic variation of the surrounding liquid pressure. The impulse action of the bubble on the wall is realized by means of impact of a cumulative jet arising on the surface of the bubble during its collapse. The expansion of the bubble and its collapse prior to the jet collision with the wall is calculated using the boundary element method under the assumption that the liquid is ideal incompressible and its movement is potential. The jet impact on the wall, during which the liquid compressibility is significant, is calculated using the equations of gas dynamics and the CIP-CUP method. It is found that in the considered frequency range of the liquid pressure oscillations, the shape of the jet at the beginning of its impact remains nearly the same. For the frequency corresponding to the wall pressure maximum, estimates of the pulse loading on the wall are obtained. It is shown that the pressure distribution on the wall during impact is violently nonuniform with a pronounced peak at the periphery of the loaded area. The maximum pressure on the wall averaged over the loaded area is equal to the water hammer pressure, whereas the maximum peripheral pressure is about 2.5 times as much.

Spreading and oscillation induced by liquid drop impacting onto sessile drop

Abstract This study investigates interaction between an impact liquid drop and a sessile drop on both flat and cylindrical substrates, focusing mainly on the combined liquid spreading and oscillation under low impact velocity with aid of high-speed photography. Different from the coaxial interaction with spreading and recoiling one after another, the off-center interaction presents an asymmetric liquid motion featured by the concomitant spreading and recoiling. Rim thickness in recoiling decreases appreciably with increasing the offset distance. Results also show that the height of combined liquid is more representative of liquid oscillation than the diameter, based on which the interaction is grouped into four major phases: impingement phase, unsteady damped oscillation phase, steady damped oscillation phase, and static phase. Also presented in this study are maximum spreading diameter and minimum height of the combined liquid. This is followed by investigations of unsteady duration, oscillation period, and height profile with regards to Weber number and offset distance.