Horizontal Oscillations Research Articles

Internal tides and the inviscid dynamics of an oscillating ellipsoid in a stratified fluid

A boundary integral representation is derived for the translational oscillations of a triaxial ellipsoid in a uniformly stratified fluid. The representation is of single-layer type, a distribution of sources and sinks over the surface of the ellipsoid. The added mass tensor of the ellipsoid is deduced from it and, from this tensor, the impulse response function together with the energy radiated away as internal waves. Horizontal oscillations correspond to the generation of an internal or baroclinic tide by the oscillation of the barotropic tide over ellipsoidal topography at the bottom of the stratified ocean. Such topography is unconditionally supercritical, namely of slope larger than the slope of the wave rays, irrespective of the frequency of oscillation. So far, analytical work on supercritical topographies has been limited, for the most part, to two-dimensional set-ups. Here, for the ellipsoidal seamount, the orientation of the barotropic tide and the anisotropy of the topography have their effects analysed in detail. As the height of the seamount increases, the rate of conversion of barotropic energy into baroclinic form is seen to first increase according to the square law expected for a topography of small slope, then saturate and eventually decrease.

Water wave radiation by an array of bottom-mounted surface-piercing concentric cylinders

This paper develops a wave radiation analysis model in horizontal oscillation mode for concentric cylindrical arrays with arbitrary numbers and arrangements within the framework of linear potential flow theory. The concentric cylinders have solid inner cylinders and porous outer cylinders, and they are both bottom-mounted and surface-piercing. The porous boundary conditions of the outer cylinders are treated using Darcy's law, and the flow field is divided into one outer region and N (number of cylinders) inner regions with the outer cylinders as the boundary. Employing eigenfunction expansion and region-matching methods, expressions for the radiation velocity potential of each region are obtained, and then expressions of the added mass and damping coefficient of each cylinder are obtained. Following a rigorous verification of the results against published literature, this paper proceeds to analyze the impact of various parameters, including oscillation modes, outer cylinder permeability, radius ratio, spacing, and the number of cylinders, on the wave radiation characteristics of tandem-arranged cylindrical arrays. The research reveals that when the oscillation direction of the structure is parallel with its arrangement direction, the hydrodynamic coefficient curves exhibit significant spikes, attributed to the influence of the Dirichlet trapped mode. Outside the peak regions, the hydrodynamic coefficient curves display regular fluctuations, which are attributed to the alternating occurrence of constructive and destructive interference effects within the wave field.

A hovering bubble with a spontaneous horizontal oscillation

Active matters, characterized by multi-mode motions, have been emerging for both engineering and biological applications. Generally, active objects rely on the symmetry-broken structures, compositions, or interfacial activities through a physical or chemical approach. Here, we report an active bubble spontaneously hovering with a horizontal oscillation at the solid/liquid interface by impacting a stationary laser beam into a liquid through a transparent solid cover. This spontaneous oscillation mode of the bubble synchronizes with that of the interfacial temperature and hydrodynamical flow. A physical mechanism is proposed, and the scaling analysis of the oscillation frequency agrees well with experiments in various liquids under different laser powers. Additionally, the bubble trajectory rotates azimuthally, arising from the symmetry breaking of the vortex pair accompanying the oscillation. Moreover, the double pendulum of oscillation bubbles has been demonstrated, achieving a preferable oscillation direction in a controllable way. These findings would not only advance our understanding of active matters but also shed light on the bubble-mediated technological applications, such as microrobots and drug deliveries.

Horizontal oscillation processed large MXene with Low Ti–Ti coordination for fast sodium storage

Horizontal oscillation processed large MXene with Low Ti–Ti coordination for fast sodium storage

From hydrodynamics to dipolar colloids: Modeling complex interactions and self-organization with generalized potentials.

The self-organization of clusters of particles is a fundamental phenomenon across various physical systems, including hydrodynamic and colloidal systems. One example is that of dense spherical particles submerged in a viscous fluid and subjected to horizontal oscillations. The interaction of the particles with the oscillating flow leads to the formation of one-particle-thick chains or multiple-particle-wide bands, both oriented perpendicular to the oscillation direction. In this study, we model the hydrodynamic interactions between such particles and parallel chains using simplified potentials. We first focus on the hydrodynamic interactions between chains, which we characterize using data from fully resolved numerical simulations. Based on these interactions, we propose a simplified model potential, called the Siren potential, which combines the representative hydrodynamic interactions: short-range attraction, mid-range repulsion, and long-range attraction. Through one-dimensional Monte Carlo simulations, we successfully replicate the characteristic patterns observed in hydrodynamic experiments and draw the phase diagram for the model potential. We further extend our analysis to two-dimensional systems, introducing a dipole-capillary model potential that accounts for both chain formation and Siren-like chain interactions. This potential is based on a system with colloidal particles at an interface, where chain formation is driven by an external electric field that induces a dipole moment parallel to the interface in each particle. The capillary force contributes the long-range attraction. Starting with parallel chains, the patterns in the two-dimensional Monte Carlo simulations of this colloidal system are similar to those observed in the hydrodynamic experiments. However, we identify that nonlinear interactions are important for some distinct steps in the chain formation. Still, the model potentials help clarify the dynamic behavior of the particles and chains due to the complex interactions encountered in both hydrodynamic and colloidal systems, drawing parallels between them.

Energy extraction and Keplerian fundamental frequencies in the Kalb–Ramond gravity

The nonminimal coupling of the nonzero vacuum expectation value of the self-interacting antisymmetric Kalb–Ramond field with gravity leads to a power-law hairy BH having a parameter s, which encompasses the Reissner-Nordström black hole (s=1). It is obtained the axially symmetric counterpart of this hairy solution, namely, the rotating Kalb–Ramond black hole, which encompasses, as special cases, Kerr (s=0) and Kerr–Newman (s=1) black holes. With rotating Kalb–Ramond black hole metric, we study its horizon structure and motion of the test particles in the near of the equatorial plane and we determine radial motion equations which governing t and ϕ. We also explore thatthe black hole mass increasing when falling many of mass-less particles are relative to the black hole mass. We consider how the Kalb–Ramond parameters depend on increasing its mass. Furthermore, we analyze the Keplerian frequency, as well as the vertical and horizontal oscillations of basic frequencies, using a graph-based approach. The frequency charts are contingent upon the Kalb–Ramond parameters s and Γ. By consulting certain sources, ones can investigate the distinctions between KR gravity and other models.

Effect of background wind and dissipation processes on the diurnal component of atmospheric solar tides

The radiation coming from the Sun heats the Earth’s atmosphere and generates atmospheric tides. In this paper, we model atmospheric tides in the presence of background wind and dissipation processes and investigate their effects. The equations for tidal oscillations of wind and temperature in the atmosphere encompass factors such as background wind, temperature profile, and background composition including ozone, carbon dioxide, hydro-magnetic interactions, Newtonian cooling, eddy, and molecular diffusion. These components interact to define the behavior of tidal phenomena comprehensively. Thermal forcing processes include the insolation absorption of H2O in the troposphere, O3 in the stratosphere, and a contribution from O2 absorption in the thermosphere. The method of solution for the equations is outlined for the solar diurnal tides during the March equinox by considering all these dissipation processes and the background wind. The obtained results are in good agreement with the Global Scale Wave Model (GSWM-00). It is found that the background wind plays significant role in affecting the horizontal wind oscillations below 100 km. At higher altitudes (100–200 km), the background wind, ion drag force, divergence of momentum, and heat fluxes due to molecular and eddy diffusion have a considerable role in affecting the zonal and meridional winds.

Unexpected frequency of horizontal oscillations of magnetic structures in the solar photosphere

It is well known that the dominant frequency of oscillations in the solar photosphere is ≈3 mHz, which is the result of global resonant modes pertaining to the whole stellar structure. However, analyses of the horizontal motions of nearly 1 million photospheric magnetic elements spanning the entirety of solar cycle 24 have revealed an unexpected dominant frequency, ≈5 mHz, a frequency typically synonymous with the chromosphere. Given the distinctly different physical properties of the magnetic elements examined in our statistical sample, when compared to largely quiescent solar plasma where ≈3 mHz frequencies are omnipresent, we argue that the dominant ≈5 mHz frequency is not caused by the buffeting of magnetic elements, but instead is due to the nature of the underlying oscillatory driver itself. This novel result was obtained by exploiting the unmatched spatial and temporal coverage of magnetograms acquired by the Helioseismic and Magnetic Imager (HMI) on board NASA’s Solar Dynamics Observatory (SDO). Our findings provide a timely avenue for future exploration of the magnetic connectivity between sub-photospheric, photospheric, and chromospheric layers of the Sun’s dynamic atmosphere.

Modeling and analysis of a two-stage tri-linear pendulum ultra-low frequency horizontal vibration isolator with experimental investigations.

In engineering practice, the external horizontal oscillations always influence the working performance of precise instruments, advanced manufacture equipment, and gravitational wave detection. In order to ensure the normal operation of these instruments, it is necessary to attenuate these vibrations adequately. The pendulum mechanism horizontal vibration isolator is an efficient method. Hence, this paper presents a type of two-stage tri-linear pendulum horizontal vibration isolator (TPHVI). The first-stage TPHVI is connected in series with the second-stage one. The dynamic equations of the two-stage TPHVI are subsequently established so that the vibration isolation performance of the two-stage TPHVI is acquired. The analysis result of the natural frequency of the two-stage TPHVI reveals that it can obtain a low frequency vibration isolation performance when the first-stage TPHVI swings in a small value. As a case study, an experimental rig is constructed. The measured transmissibility keeps in good agreement with the calculated one. The natural frequency of the second-stage TPHVI is 0.25Hz. The initial vibration isolation frequency is 0.3Hz. When the external frequency is 0.8Hz, the transmissibility of the second-stage TPHVI reaches -20 dB. Meanwhile, when the external frequency is 3Hz, the transmissibility of the second-stage TPHVI is -40 dB. These measured data demonstrate that the proposed two-stage TPHVI can realize low frequency vibration isolation horizontally, which will have broad application prospects in the field of ultra-precision in engineering practice.

Experimental studies of the influence of elastic-dissipative parameters of engine mounting units on the dynamic characteristics of the “wing model – elastic pylon – engine” system

A feature of modern heavy transport aircraft is their layout with engines on elastic pylons under the wing, with the fuel tanks located in the wing consoles. In this case, the main elastic tones of the aircraft’s own oscillations, which determine its dynamic response to external disturbing influences, include the so-called motor tones (vertical and horizontal (lateral) oscillations of engines on elastic pylons). A new type of flutter has appeared – pylon, which for some aircraft determines the critical flutter speed of the aircraft as a whole. The main reason for this phenomenon is the low oscillation damping of the engine on the pylon under the wing. Therefore, research aimed at modernizing the engine mounting points on the pylon in order to reduce the level of elastic oscillations during aircraft operation seems relevant. One of the possible ways to solve this problem is to use the concept of a freed engine, when the engine attachment points to the pylon are modernized, providing more effective damping of engine oscillations. In order to confirm the possibility of practical implementation of these solutions, corresponding experimental studies were carried out on an experimental setup developed by the authors. A design of engine mounting units has been developed that allows specified displacements of the engine relative to the pylon during forced elastic oscillations of the system, which includes a hinged suspension, installation of additional elastic elements and hydraulic dampers.The article presents the results of studies of the influence of elastic-dissipative parameters (partial frequency of natural oscillations and partial decrement of oscillations) of an engine mount on an elastic pylon on the dynamic characteristics of the dynamic system “wing model – elastic pylon – engine”. It is shown that by introducing specially designed engine suspension units on pylons, it is possible to significantly change the dynamic characteristics (frequencies and amplitudes of natural oscillations) of the elastic system as a whole. Thus, the amplitudes of oscillations of the engine’s center of mass in the region of motor tones decrease by 3...7 times during forced harmonic oscillations.

Bidirectional Multi-Spectral Vibration Control: Insights from Automotive Engine Mounting Systems in Two-Dimensional Structures with a Damaged Vertical Active Element

Active mounting systems have become more prevalent in recent years to effectively mitigate structure-induced vibration across the automobile chassis. This trend is particularly evident in engine mounts. Considerable research has been dedicated to this approach owing to its potential to enhance the quietness and travel comfort of automobiles. However, prior research has concentrated on a limited spectrum of specific vibrations and noise control or has been restricted to vertical vibration control. This article describes the modeling, analysis, and control of a source structure employing a multidirectional active mounting system designed to closely simulate the position and direction of an actual automobile engine mount. A piezoelectric stack actuator is connected in series to an elastic (rubber) mount to form an active mount. The calculation of the secondary force required for each active mount is achieved through the application of harmonic excitation forces. The control signal can also reduce vibrations caused by destructive interference with the input signal. Furthermore, horizontal oscillations can be mitigated by manipulating the parameters via dynamic interconnections of the source structure. We specifically examined the level of vibration reduction performance in the absence of a vertical active element operation and determined whether the control is feasible. Simulation outcomes demonstrate that this active mount, which operates in both the vertical and horizontal directions, effectively mitigates excitation vibrations. Furthermore, a simulation was conducted to mitigate the vibrations caused by complex signals (AM and FM signals) and noise. This was achieved by monitoring the system response using an adaptive filter NLMS algorithm. Adaptive filter simulations demonstrate that the control efficacy degrades in response to complex signals and noise, although the overall relaxation trend remains unchanged.

Thrust production and chordal flexion of the flukes of bottlenose dolphins performing tail stands at different efforts.

Dolphins have become famous for their ability to perform a wide variety of athletic and acrobatic behaviors including high-speed swimming, maneuverability, porpoising and tail stands. Tail stands are a behavior where part of the body is held vertically above the water's surface, achieved through thrust produced by horizontal tail fluke oscillations. Strong, efficient propulsors are needed to generate the force required to support the dolphin's body weight, exhibiting chordwise and spanwise flexibility throughout the stroke cycle. To determine how thrust production, fluke flexibility and tail stroke kinematics vary with effort, six adult bottlenose dolphins (Tursiops truncatus) were tested at three different levels based on the position of the center of mass (COM) relative to the water's surface: low (COM below surface), medium (COM at surface) and high (COM above surface) effort. Additionally, fluke flexibility was measured as a flex index (FI=chord length/camber length) at four points in the stroke cycle: center stroke up (CU), extreme top of stroke (ET), center stroke down (CD) and extreme bottom of stroke (EB). Video recordings were analyzed to determine the weight supported above the water (thrust production), peak-to-peak amplitude, stroke frequency and FI. Force production increased with low, medium and high efforts, respectively. Stroke frequency also increased with increased effort. Amplitude remained constant with a mean 33.8% of body length. Significant differences were seen in the FI during the stroke cycle. Changes in FI and stroke frequency allowed for increased force production with effort, and the peak-to-peak amplitude was higher compared with that for horizontal swimming.

Experimental and theoretical research on oscillation behavior of droplets on horizontally oscillating substrates

The oscillation behavior of a droplet on a horizontally oscillating flat substrate was studied. We derived a formula to relate the resonance frequency and damping constant of the horizontal oscillation of the droplet to the physical properties of the liquid materials, which were examined experimentally. The resonance frequency and damping constant were expressed as functions of surface tension, droplet radius, contact angle, density, and viscosity. Furthermore, we observed the non-equilibrium phenomenon of the droplet through the adsorption of molecules from the surrounding gas phase onto the droplet surface. We demonstrated the time evolution of the surface tension of an ethanol aqueous solution, and the decrease in surface tension due to the evaporation of ethanol was detected using the newly developed system.

Linear coupling of transverse betatron oscillations: Dynamic stability and invariants of motion

Based on the technique of the discrete one-turn transfer maps, the problem of linear coupling between horizontal and vertical betatron oscillations in an accelerator has been treated exactly and entirely in explicit form. The stability region in the fractional part of the horizontal and the vertical betatron tune space as a function of the linear coupling strength has been obtained, and the increment/decrement of the horizontal and the vertical betatron oscillations in the case of the linear sum resonance has been shown to be approximately equal to the half of the coupling strength. The normal form parameterization of the one-turn linear map with horizontal-to-vertical coupling has been developed in detail in the spirit of Edwards and Teng formalism. The motion in the normal mode in the new normal form coordinates is decoupled by implying that two independent Courant-Snyder invariants exist, which have been found explicitly. Published by the American Physical Society 2024

Vibration Analysis and Motion Control Method for an Under-Actuated Tower Crane

In this paper, we developed a solution for controlling a tower crane thought as a no-rigid system, and therefore able to have deformation and, during the motion, vibrations. Particularly, large tower cranes show high structural dynamics. Under external excitations, the payload tends to sway around its vertical position and this motion is coupled to the resulting dynamic vibration of the crane structure. These induced vibrations may cause instability and serious damage to the crane system. Furthermore, the energy stored in the flexible structure of a tower crane causes vibrations in the structure during the acceleration and deceleration of slewing movements. A crane operator perceives these vibrations as an unstable speed of the boom. Such behavior involves the control of the crane, particularly precise positioning and manual control of the crane movement at low pivoting speed. We define an Elastic model of the Slewing crane and analyze the bending and Torsional elasticity of the Tower, and the Jib Elasticity. With an approximated method, we calculate the natural wavelengths of the crane structure in the slewing direction. We consider the tower crane as a nonlinear under-actuated system. The motion equations are obtained considering both the normal vibration modes of the tower crane and the sway of the payload. An elastic model of the Slewing crane is achieved, modeling the crane jib as an Euler-Bernoulli beam. Even the payload dynamic is considered, developing an Anti-sway solution by the equation of the movement. We define an iterative calculation of the sway angles and obtain the corresponding velocity profiles, implementing two kinds of solution: an input-shaping control in open-loop, to be used with automatic positioning, and a “command smoothing” method in open-loop, used for reducing the sway of the payload with the operator control. These solutions lead to a reduction of the vibrations of the crane structure. As a consequence, the tower crane is not subject to the strong horizontal and vertical oscillations during the motion of the elastic structure.

A GPU accelerated three-dimensional ghost cell method with an improved implicit surface representation for complex rigid or flexible boundary flows

This paper presents an efficient and reliable three-dimensional (3D) ghost cell method for complex rigid or flexible boundary flows. An improved implicit interface representation method is developed to treat the arbitrary complex interfaces including the thin or sharp boundaries. This method is robust and avoids the solving of a large dense matrix, and thus the computational efficiency is greatly enhanced. The ghost cell method with a unified eight-node interpolation scheme is adopted to enforce the no-slip boundary conditions on complex boundaries. To perform 3D high-resolution simulation on a desktop computer, a GPU parallel framework in CUDA environment is developed to significantly accelerate the computational efficiency of the present solver. The horizontal oscillations of a two-dimensional (2D) cylinder and a 3D sphere in the rest fluid are simulated to validate the accuracy and computational performance of the present model. Spatial accuracy of near second-order on the boundary treatment and good grid convergence are confirmed. Also, the present solver can achieve hundreds of acceleration ratios for 2D grids and thousands of acceleration ratios for 3D grids. Then, uniform flows around a 3D arbitrary rigid or flexible object such as a stationary cylindrical cylinder, a stationary square cylinder, an oscillating airfoil, and a swimming carangiform are simulated. The accuracy and capability of the present model for 3D complex geometries with large-amplitude movement or deformation is satisfactorily validated. Moreover, typical 3D wake structures are well captured.

Horizontal oscillations of the wood sawing support during the cutting process in a wood sawing line using a vertical bandsaw

The wooden trolley (in the sawing line using a vertical bandsaw) during work generally moves by iron wheels on two rails placed on the concrete floor. Due to the effect of noticeable cutting force applied by the saw blade and the vehicle's uneven weight on the wheels, it causes the vehicle to vibrate during the horizontal movement, affecting the stability of the wood sawing circuit. By modeling the problem of vibration of beams located on Winkler elastic foundations, subjected to mobile concentrated loads, the article has built a system of differential equations of vibration of two rails, giving an expression to calculate the vibration amplitude of the swan plane. The influence of the flexural rigidity EI of the rails and the elastic stiffness k of foundation on the vibration amplitude of the cutting plane is studied and analyzed. The use of the Dirac Delta function and the employed analytical solution allow the designers to evaluate the accuracy and reliability of the calculated results.

Dynamics of freely falling perforated disks

The dynamics of free-falling perforated disks within the moderate Reynolds number Rem regime (700<Rem<1400) are experimentally investigated in this paper, including translation and rotation dynamics. Four falling styles are analyzed, including spiral motion, Hula-Hoop motion, helical precession motion and spiral irregular motion. In contrast to spiral irregular motion, we group the other three motions as regular motions. The relative contribution of different dynamical effects (impulsive effect, Magnus effect and viscous effect respectively) is quantitatively determined. The contribution of impulsive effect is commonly ignorable during the descent, and Magnus effect plays a crucial role in horizontal oscillations. Vortex loads always dominate this dynamical process, and balance the gravity along the vertical direction. In the Frenet–Serret coordinate system, the contribution resulting from Magnus effect is relatively small to that of vorticity-induced fluid force. Hence, an alternative way to model this involved system is presented, which is based on the extended Kelvin-Kirchhoff equations. A Fast Fourier Transform (FFT) is performed on total hydrodynamics forces FHx and FHy. For regular motions with the dimensionless inertia ratio I∗≤1×10−3, sub-harmonic force components are identified in the frequency domain. However, the frequency ratio of high-frequency components and the dominant peak is no longer integer in spiral irregular motion. The azimuth distribution of angular velocity is counted in the Frenet–Serret coordinate system. For spiral irregular motion with the dimensionless inertia ratio I∗>1×10−3, no preferential alignment is observed and its distribution scatters, while those of regular motions are rather concentrated. The probability density functions (PDFs) of angular velocity components in spiral and Hula-Hoop motions share similar distributions, which indicates angular dynamics may decouple from translation dynamics in high Reynolds number regime under certain circumstances.

Spectral and temporal features of GX 13+1 as revealed by AstroSat

ABSTRACT GX 13+1, a neutron star low-mass X-ray binary that exhibits the properties of both atoll and Z sources, is studied using data from Soft X-ray Telescope and Large Area X-ray Proportional Counter (LAXPC) onboard AstroSat. The source traces a ν shaped track in its hardness-intensity diagram (HID). Spectral modelling of the data in the 0.7–30.0 keV energy range, with the model – $\tt {constant}$ × $\tt {tbabs}$ × $\tt {thcomp}$ × $\tt {bbodyrad}$ + $\tt {relxillNS}$, yields orbital inclination angle (θ) of 77$\substack{+10\\-8}$°. Flux resolved spectral analysis reveals the ν shaped pattern in the plots of spectral parameters kTe, kTbb, and Γ versus Fbol, closely resembling the pattern traced in LAXPC HID. This indicates changes in the spectral properties of the corona and the boundary layer/accretion disc. Assuming that the accretion disc truncates at the Alfvén radius, the upper limit of the magnetic field strength (B) at the poles of neutron star in GX 13+1 is calculated to be 5.10 × 108 G (for kA = 1 and η = 0.1), which is close to that of atoll sources. Furthermore, thickness of the boundary layer is estimated to be 5.70 km, which results in the neutron star radius value of ≲14.50 km. Quasi-periodic oscillations (QPOs) at 56 ± 4 and 54 ± 4 Hz are detected in Regions D and E of HID, respectively. The frequencies of these QPOs are similar to the characteristic frequency of horizontal branch oscillation and these do not exhibit a positive correlation with mass accretion rate.

Simultaneous Horizontal and Vertical Oscillation of a Quiescent Filament Observed by CHASE and SDO

In this paper, we present the imaging and spectroscopic observations of the simultaneous horizontal and vertical large-amplitude oscillation of a quiescent filament triggered by an extreme-ultraviolet (EUV) wave on 2022 October 2. Particularly, the filament oscillation involved winking phenomenon in Hα images and horizontal motions in EUV images. Originally, a filament and its overlying loops across AR 13110 and 13113 erupted with a highly inclined direction, resulting in an X1.0 flare and a non-radial coronal mass ejection. The fast lateral expansion of loops excited an EUV wave and the corresponding Moreton wave propagating northward. Once the EUV wave front arrived at the quiescent filament, the filament began to oscillate coherently along the horizontal direction, and the “winking filament” appeared concurrently in Hα images. The horizontal oscillation involved an initial amplitude of ∼10.2 Mm and a velocity amplitude of ∼46.5 km s−1, lasting for ∼3 cycles with a period of ∼18.2 minutes and a damping time of ∼31.1 minutes. The maximum Doppler velocities of the oscillating filament are 18 km s−1 (redshift) and −24 km s−1 (blueshift), which were derived from the spectroscopic data provided by the Chinese Hα Solar Explorer/Hα Imaging Spectrograph. The three-dimensional velocity of the oscillation is determined to be ∼50 km s−1 at an angle of ∼50° to the local photosphere plane. Based on the wave–filament interaction, the minimum energy of the EUV wave is estimated to be 2.7 × 1020 J. Furthermore, this event provides evidence that Moreton waves should be excited by the highly inclined eruptions.