Horizontal Oscillations Research Articles

Superharmonic and triadic resonances in a horizontally oscillated stably stratified square cavity

The response to harmonic horizontal oscillations of a stably stratified fluid-filled two-dimensional square container is examined as the forcing amplitude is increased. For the studied forcing frequency, the response flow at very small forcing amplitudes is a synchronous periodic flow with piecewise-constant vorticity in regions delineated by the characteristics emanating from the corners of the container, regularized by viscosity. The second temporal harmonic of the forced response flow resonantly excites an intrinsic mode of the stratified container, whose magnitude grows as the square of the forcing amplitude. Above a critical forcing amplitude, a sequence of pairs of other container modes are excited via triadic resonances with the second-harmonic-driven mode. The flows are computed from the Navier–Stokes–Boussinesq equations and the ensuing dynamics is analysed using Fourier techniques, providing a comprehensive picture of the transition to internal wave turbulence.

In situ study on the oscillation of mobile droplets and force analysis during the directional solidification of Al-Bi alloy

During solidifications of immiscible alloys, the motion of droplets at the solid/liquid (S/L) interface is generally driven by dragging force, gravity force, repulsion force of interface, and thermal-solutal Marangoni force. However, there is few in situ study investigating kinetics behavior to analyze the forces on droplets. The mechanism of droplet motion remains unclear due to the unavailability or uncertainty of the effect of convection and solutal Marangoni force on droplet behavior. In this study, directional solidification of immiscible Al-Bi alloy was observed via synchrotron radiography, and the horizontal oscillation of droplets at S/L interface was detected for the first time. Forces, especially solutal Marangoni force, were calculated based on the in situ measured radius of droplets and thermal-solutal gradients. The experimental results cannot be reasonably explained by the previous analysis model which neglects melt convection. The non-negligible effect of flow on droplet motion was demonstrated, and the force balance of droplet both vertically and horizontally can be obtained considering a lift force of 6.39 × 10−9 N and a modified solute-related parameter dσdc of 0.45−0.65 J m−2, respectively.

Simulation Modeling of an Inhomogeneous Medium, in Particular: Round, Triangular, Square Shapes

The article analyzes and develops an algorithm for the operation of the powder backfill process using vibration oscillations. The results of the study make it possible to predict the main properties of particles of any shape. The developed computer simulation model also provides for the superposition of horizontal and vertical oscillations. It should be noted that the difference between them is that the main one for the implementation of horizontal oscillations is the X - coordinate, and for vertical ones – the Y - coordinate. It is also important that the model algorithm provides for simultaneous application of vibration oscillations, which makes it possible to study the influence of the history of the backfill process. It should also be noted that in this scientific study, a number of experiments were conducted, the change in porosity during the imposition of oscillations was studied, and graphs of the obtained experimental dependences were constructed. Porosity from the main parameters of the bunker, in particular: width and height, is also studied. The obtained results made it possible to record the optimal porosity of the backfill with a reliable deviation error (± 1%).

Improving the stability and handling of tractors when towing trailers and coupled units

BACKGROUND: Currently, almost all agricultural work is performed using tractors. As the transport speed of a tractor train increases, the amplitude of lateral and horizontal oscillations of its coupled units emerges and increases. At certain velocities, these oscillations become so large that they can lead to a rollover, in addition, shock loads occur in coupling devices, which make it difficult to handle a tractor train. The traditional method to prevent this is the velocity limit, which does not guarantee a positive result.
 AIMS: Development of methods to improve stability, handling and safety of wheeled tractor trains by reducing the galloping and yawing of a truck tractor when towing heavy loads.
 METHODS: The following options of the design of the system for countering the occurrence of self-oscillations in the design of a wheeled tractor train ensuring a reduction in the level of self-oscillations, increasing the stability, handling and safety of the tractor train have been proposed: the coupling device equipped with hydraulic damping devices operating at longitudinal and lateral folding; the control system for the individual traction electric drive of a truck tractor preventing the loss of wheel grip with the ground surface; the combined use of the control system for the individual traction electric drive of a truck tractor and the coupling device equipped with hydraulic damping devices; the combined use of the coupling device equipped with hydraulic damping devices and a steering correction system.
 RESULTS: With use of simulation modeling methods, it has been established that the coupling device equipped with hydraulic damping devices adjustable by the folding angle of the tractor train and by the yaw angle oscillations of a truck tractor body should be recognized as the most acceptable and effective system for reducing self-oscillations of a wheeled tractor train at the current state of the art.
 CONCLUSIONS: The practical value of the study lies in the possibility of using the proposed methods to eliminate the risk of self-oscillating processes in the design of promising types of agricultural machinery.

Effect of Horizontal Quasi-Periodic Oscillation on the Interfacial Instability of Two Superimposed Viscous Fluid Layers in a Vertical Hele-Shaw Cell

We investigate the effect of horizontal quasi-periodic oscillation on the stability of two superimposed immiscible fluid layers confined in a horizontal Hele-Shaw cell. To approximate real oscillations, a quasi-periodic oscillation with two incommensurate frequencies is considered. Thus, the linear stability analysis leads to a quasi-periodic oscillator, with damping, which describes the evolution of the amplitude of the interface. Two types of quasi-periodic instabilities occur: the low-wavenumber Kelvin-Helmholtz instability and the large-wavenumber resonances. We mainly show that, for equal amplitudes of the superimposed accelerations, and for a low irrational frequency ratio, there is competition between several resonance modes allowing a very large selection of the wavenumber from lower to higher values. This is a way to control the sizes of the waves. Furthermore, increasing the frequency ratio has a stabilizing effect for both types of instability whose thresholds are found to correspond to quasi-periodic solutions using the frequency spectrum. For a ratio of the two superimposed displacement amplitudes equal to unity and less than unity, the number of resonances and competition between their modes also become significant for the intermediate values of the ratio of frequencies. The effects of other physical and geometrical parameters, such as the damping coefficient, density ratio, and heights of the two fluid layers, are also examined.

Transition of a 2D crystal to a non-equilibrium two-phase coexistence state

In this paper, we present experimental observation of the transition of a 2D dust crystal to a non-equilibrium solid–liquid phase coexistence state. The experiments have been carried out in an L-shaped dusty plasma experimental device in a DC glow discharge argon plasma environment. Initially, a monolayer crystalline structure is formed, which is later transformed to a two-phase coexistence state using the background neutral pressure as a control parameter. Self-excited horizontal oscillations are found in the center of the monolayer prior to the appearance of the coexistence state. It is observed that a molten center coexists with a solid periphery. Various structural, thermodynamic, and dynamical quantities are used to characterize the phase state. The surface tension at the solid–liquid circular interface is also determined. A detailed parametric study is made to delineate the existence region of such a state. It is found that melting caused at the core is due to the onset of a localized Schweigert instability in the presence of a few stray particles beneath the top layer in that region.

Surface wave suppression in granular media using a partially embedded meta-barrier

Existing studies on meta-barrier designs for suppressing surface modes in inhomogeneous granular media are limited to meta-barriers comprising vertical or horizontal oscillators. However, a clear understanding of the surface mode hybridizations with the local resonances of the resonators is lacking and could help realize more realistic meta-barrier designs for surface wave control in granular media. In this work, we propose a meta-barrier comprising partially embedded rod-like resonators to study the hybridization of the fundamental surface modes: PSV1 and PSV2, with the longitudinal and flexural resonances of the resonators that enable surface mode suppression. The hybridized dispersion curves and frequency-domain finite element simulations with the meta-barrier demonstrate preferential hybridization of the PSV1 mode with the longitudinal resonance of the resonators, enabling PSV1 mode suppression above the hybridized longitudinal-resonance mode cut-off frequency. Unlike the PSV1 mode, PSV2 hybridizes with both longitudinal and flexural resonances, making it challenging to suppress the mode. However, we observe that enhancing the filling fraction of the meta-barrier promotes PSV2 mode suppression as the flexural-resonance hybridized modes are localized under the meta-barrier. The time-domain finite element simulation using a broadband excitation source further numerically validates the meta-barrier design for applications in vibration mitigation and seismic isolation of structures.

Dynamic analysis and vibration control for overhead hoist transport

The OHT system is a transport device used for intra- or inter-plant transport in a fab or other factory, the load-bearing part of the goods stored under the trolley generates longitudinal vibration and lateral oscillation due to inertia force When the OHT in the air starts or stops. Firstly, the trolley dynamic model under the action of lateral thrust and longitudinal tensile force need to be established. secondly, the coupling analysis of horizontal oscillation and longitudinal oscillation on the model is carried out. Thirdly, aiming at the lateral swing and longitudinal vibration of the carriage, a double closed-loop vibration control strategy with tension control as inner loop and speed control as outer loop and carry out the simulation analysis of longitudinal vibration control is proposed. In the experiment of the ground trolley, the control strategy is applied. The simulation and experimental results show that the control method can quickly restrain the longitudinal vibration of the trolley bearing plate, reduce the pulling force of the trolley on the lifting steel belt, and avoid the large displacement of the bearing plate in the air.

Seismic dynamics of offshore wind turbine-seabed foundation: Insights from a numerical study

In the past 10 years, the offshore wind energy harvest industry has developed rapidly worldwide. However, seismic waves would bring a great threat to the safety and stability of offshore wind turbines (OWTs). In this study, taking the marine geotechnics numerical software FssiCAS as the computational platform, adopting the generalized elastoplastic soil model Pastor-Zienkiewicz-Mark III (PZIII) to describe the complex mechanical behavior of seabed soil, the seismic dynamics, as well as the stability of a thin-walled monopile OWT with an equipped capacity of 1.5 MW and its seabed foundation are comprehensively investigated, by the way of finely modeling and meshing for the important components of the OWT, i.e., the blades, nacelle, and tower. The numerical results indicate that OWT and its seabed foundation strongly respond to the excitation of seismic waves, and there is intensive interaction between OWT and its seabed foundation. In the case of this study, the horizontal oscillation amplitude at the top of the turbine tower reaches 2m, the superficial seabed soil at the far field is liquefied with a depth of 3–4 m, and the liquefaction depth of the seabed soil surrounding the monopile reaches 5–6 m. Even so, the OWT involved in this study has no cumulative displacement, there is only vibration displacement. It is indicated that the OWT has good seismic stability. It is indicated by the comparative study that the complex mechanical behavior of seabed soil, the complex geometry and mass distribution of OWTs, and the consideration of the pore water in seabed foundations have a radical influence on the seismic dynamics of OWTs. The work presented could be a valuable reference for the evaluation of the seismic dynamics and stability of OWTs in the future.

Повышение эффективности грузоперевозок на основе совершенствования механической части электровоза 2ЭС6

The key problems of railways are presented, the cause-and-effect relationships between the dynamic characteristics of a typical scheme of a locomotive axle box suspension, the features of the traction engine suspension and malfunctions of its mechanical components are revealed. The impact of the properties of the spring suspension of the electric locomotive on emergence of defects in rails and wheels is reflected. A brief overview of foundations of the theory of invariance and application of the compensation method of external disturbances to improve the indicators of locomotive dynamic qualities is presented. Mathematical modeling of oscillations of the «locomotive-track» system with standard and upgraded systems of the axle box stage of the spring suspension of the 2ES6 electric locomotive has been performed, which makes it possible to evaluate the effectiveness of the proposed method for improving the dynamic qualities of the locomotive based on application of compensation of external disturbances compared with the standard scheme of the box stage of the 2ES6 electric locomotive. In order to reduce dynamic loads in the body of the traction motor and in the supports of motor axial bearings arising from horizontal oscillations of the electric locomotive, a new technical solution has been proposed which increases the reliability of motor axial bearings, their attachment points and the body of the traction motor.

Graphical analysis of an oscillator with constant magnitude sliding friction

We treat a horizontal oscillator damped by constant-magnitude sliding friction by extending the analogy between the simple harmonic motion of a mass on a spring and the uniform circular motion of a mass attached to the end of a string. In the presence of sliding friction, the motion of the mass on a spring becomes the horizontal projection of the path of a mass attached to a string winding around two nails separated by a well-defined distance; this path is a spiral consisting of connected semi-circles of diminishing radii. This graphical analysis is very simple and pedagogically useful. It can also be generalized to any oscillation affected by other forces of constant magnitude but not necessarily constant direction.

Suppression of eddy-current effects in beam injection using a pulsed sextupole magnet with a new ceramic chamber

At the Photon Factory storage ring (PF ring) of the High Energy Accelerator Research Organization (KEK), a pulsed sextupole magnet (PSM) has been used for top-up injection for the first time. Following its successful operation at the KEK, this new injection scheme was expanded to one with a nonlinear kicker in BESSY II and was then applied at UVSOR and Aichi SR in Japan. Also, the PSM system in the PF ring was improved by introducing a rectangular shape for the magnet's bore to strengthen the magnetic field. However, this upgraded PSM was not implemented for user operation because it induced a horizontal oscillation of the stored beam with a maximum amplitude of 5.0 mm. This oscillation was assumed to be caused by eddy currents originating from the uniform inner coating of the ceramic chamber. We, therefore, developed a modified ceramic chamber with a new patterned coating designed to suppress the eddy current--induced magnetic field. The pattern shape was optimized to suppress this magnetic field and, simultaneously, to reduce the resistive wall impedance. A fine-line pattern-coating process, originally developed for a ceramic chamber with an integrated pulsed magnet, was modified for application with the magnet's chamber of the sextupole. The maximum horizontal oscillation amplitude was suppressed by a factor of 16 by using the new PSM chamber without any issues related to beam instability. Details of the historical background of the upgrading of the PSM system, an investigation of the cause of the abnormal oscillation problem, the development of the new process for coating the ceramic chamber, and the results of the beam-response measurements for the new ceramic chamber installed in the PF ring are reported in this article.

Study of the dynamic model of the oscillating system of vibratory feeders with an elliptical trajectory of the movement of the working body

Vibrating feed bins with electromagnetic drive are widely used in the automation of production processes in mechanical engineering and instrument engineering. They are used for feeding miniature, small, or medium-sized parts to automated production equipment. These parts must be located in a certain stable position, that is, oriented in space, when using these feeders to feed component parts to the assembly position in assembly machines. Different means of orientation may be applied, which are directly located in the bunkers of these devices, in this case. The parts must be transported without sensitive tossing on trays of vibratory feeders for reliable operation of such orientation devices. A vibratory feeders with an elliptical trajectory of vibrations of the working body should be used in this case. A vibrating feeder with independent oscillations can be used in such a case. Vertical and horizontal component oscillations are excited by separate drives in it. It is necessary to apply a device for shifting phases in the power supply system of vibration drives to obtain elliptical oscillations. However, existing designs of vibrobunker feeders with an independent oscillation system have a number of significant disadvantages. They require the presence of independent vibrators: an axial vibrator to excite vertical vibrations and two or more tangential vibrators to excite horizontal (angular) vibrations. In addition, it is necessary to have a device for shifting the phases between them. Therefore, there was a need to create a new design of a vibrating bunker feeder with a system of elliptical oscillations, which will not have the listed disadvantages. Such a vibrating hopper feeder was developed and an experimental sample of this design was made. However, for the successful implementation of such feeders, a preliminary calculation of the parameters of their oscillating system is required, the methodology of which differs from the existing one. In the presented work, a mathematical study of the dynamics of the oscillating system of such vibratory feeders was carried out and a calculation method for its calculation was developed.

Anticorrelated lags in a neutron star Z source GX 5-1: AstroSat’s View

ABSTRACT We report the cross-correlation function studies of a neutron star low-mass X-ray binary, a Z source GX 5-1, using Soft X-ray Telescope (SXT) and Large Area X-ray Proportional Counter (LAXPC) energy bands onboard AstroSat. For the first time, we report the lag between soft (0.8–2.0 keV, SXT) and hard X-ray energy bands (10–20 and 16–40 keV, LAXPC) in GX 5-1 and detected lags of the order of a few tens to hundreds of seconds in the horizontal branch. We interpreted them as the readjustment time-scale of the inner region of the accretion disc. We used various two components and three-component spectral models to unfold the spectra and observed the changes in soft and hard component fluxes that were exhibiting horizontal branch oscillation variations. It was observed that the bbody component assumed to be originating from the boundary layer over the NS and was also found to vary along with the HBO variation where lags were detected. We constrained the size of the comptonizing region of the order 15–55 km, assuming that lags were due to variation in the size of the corona. We noticed a similar size of the comptonizing region after employing other models and suggest that the overall size of corona must be of the order of a few tens of km to explain the lags, HBO variation, and respective spectral variations. In a case study, it was noted that the BL size increases as GX 5-1 vary from the top of the HB to the upper vertex.

Natural Oscillations of a Tower-Type High-Rise Building: Modes of Horizontal, Vertical and Rotational Oscillations According to the Standing Wave Method and Verification of the Computational Model

Natural Oscillations of a Tower-Type High-Rise Building: Modes of Horizontal, Vertical and Rotational Oscillations According to the Standing Wave Method and Verification of the Computational Model

Mathematical modeling of truck movement in rough road conditions of agricultural area

The article presents the methods of modeling the horizontal and vertical movement of a small truck Labo. Using the Lagrange equation of the second type, mathematical models of the movement of a small truck Labo on uneven roads developed. The mathematical models developed by the Runge-Kutta-number method solved and the values of the horizontal and vertical oscillations, speeds of movement and the forces acting and acting on each wheel of the automobile found. On the given masses, the parameters of the automobile’s leaf springs and the depreciation part are determined.

Wave impact on a rigid and flexible wall using various viscous fluids during sloshing

This paper addresses a study of wave impacts on the chamfered shape of a structure during sloshing, using two different fluids through experimental analysis. Horizontal oscillations are carried out on the tank under various excitation frequencies at a fixed amplitude. Rigid and relatively flexible walls are considered for measuring pressure impact and structural deformation from the wave impacts. Various wave impulses are directed at the sidewall, and the structural deformations are discussed in detail. Wave impacts for various fluids are carried out, from which the pressure-time history, strain values, and free-surface deformation measurements are highlighted. Through the analysis, the breaking wave gets distorted by bottom chamfer at around the vertical portion of the wall. Therefore, physical results are changed likely to having with the wave strike the wall. The impact from more viscous fluids have also been found to reduce both the dynamic pressure and structural strain at practically the same rates in comparison with less viscous fluids.

The influence of the land–sea breeze on coastal upwelling systems: locally forced vs internal wave vertical mixing and implications for thermal fronts

Land–sea breeze forcing near a land boundary drives both a locally forced response and an associated offshore propagating internal wave response, the effects of which can be difficult to separate. These processes enhance vertical mixing near the critical latitude for diurnal-inertial resonance (30° N/S), and are a feature of all four major eastern boundary upwelling systems. Here, we employ 1D- and 2D-vertical model configurations forced by a land–sea breeze to quantify the relative contributions of the locally forced and internal wave responses to surface currents and vertical mixing, and test sensitivity to latitude and bottom slope. We further include a sub-inertial alongshore wind to consider the role of the land–sea breeze in the context of upwelling systems. At the critical latitude, the internal waves generated via thermocline pumping near the land boundary are evanescent (in agreement with theory) and largely absent ∼50 km offshore. The internal waves are shown to contribute to vertical mixing, which can be ∼20% greater than that due to the forced response alone, further deepening the surface Ekman boundary layer. This deepening reduces the sub-inertial offshore advection of surface waters, thereby retaining the upwelling front closer to the land boundary and driving a net warming of the nearshore surface waters. Cross-shore horizontal oscillations of the upwelling front generated by the land–sea breeze drive strong diurnal variability in sea surface temperature, in agreement with observations from a cross-shore mooring array in the southern Benguela (∼32.3° S).

Prospects of application of vibratory devices in military equipment

Possibilities of employing vibratory devices as conveying mechanisms in some models of military equipment, in particular in engineering weapons, are considered. Vibratory conveyors, which are widely used in industry for moving products over short distances, are mainly devices with one-component rectilinear oscillations, in which at the high conveying velocity the modes of movement with hopping are implemented, that is unacceptable for conveying many military facilities, including weapons and explosive objects. Vibratory conveying in non-hopping modes (without tossing) at high speed is possible when using independent (two-component) horizontal and vertical oscillations of the working body of the vibratory conveyor. Based on the analysis of the influence of oscillation parameters on the velocity and stability of vibratory movement of objects in non-hopping modes, a conclusion is made about the feasibility of using horizontal harmonic oscillations in near-resonant mode and vertical oscillations with piecewise constant acceleration. The equations describing the optimal law of vertical oscillations, which consists of two segments of parabolas during the period of oscillations, are derived. A constructive scheme of the vibratory conveyor based on a three-mass oscillating system with an unbalanced vibratory drive of horizontal oscillations and eccentric vibratory drive of vertical oscillations is proposed. The working body of the vibratory conveyor is connected to the intermediate frame by an elastic system of vertical oscillations, the stiffness of which is adjusted to a mode far from resonance. The reactive frame is connected to the intermediate frame by an elastic system of horizontal oscillations, the stiffness of which provides near-resonant mode. The presented vibratory conveyor significantly enhances the conveying velocity in non-hopping modes, which are required for conveying explosive objects, as well as increases the lifting angles and reduces the vibration transmitted to the environment, which will facilitate its use in military machines. It also outlines a number of issues that need to be addressed in the design and implementation of such devices in military equipment.

Experimental investigation of transverse quadrupolar beam oscillation in the Hefei Light Source-II storage ring

Research on the transverse beam dynamics issues and collective bunch behaviors in association with the higher-mode oscillation fields are important in analyzing beam properties and improving machine performance of particle accelerators. In this study, a simple effective excitation and detection scheme was developed to analyze the transverse quadrupole-mode beam oscillation in electron storage rings. Transverse quadrupole-mode beam oscillation was induced by the stripline transverse quadrupole kicker, and then, measured using the stripline beam position monitor in the Hefei Light Source-II storage ring. A spectrum analyzer was employed for the real-time detection of the excitation sidebands of the horizontal quadrupole-mode oscillation in both single-bunch and nominal multi-bunch operations. Additionally, the horizontal dipolar and quadrupolar kick factors are obtained as 6.992 × 1014 and −4.458 × 1014 V/mC with accuracy of 7.49% and 2.03%, respectively, for the single-bunch operation. The dipolar and quadrupolar kick factors in the nominal multi-bunch operation are −2.567 × 1013 and −2.344 × 1013 V/mC with accuracy of 3.53% and 4.91%, respectively. The experimental measurements thus validate the practicability and reliability of this scheme. Moreover, it is demonstrated that this excitation and detection method for the transverse quadrupole oscillation is valid for studying the properties of transverse higher-mode wakefields and related beam behaviors in storage ring light sources.