Velocity Diagrams Research Articles

The velocity diagram for traveling waves

The velocity diagram for traveling waves

Dependences of Characteristics of Bulges on the Mass of the Central Black Hole and Theoretical Aspects of Their Origin

To study the influence of the central black hole on the formation of the bulge of spiral galaxies, we analyzed the relationship between the masses of supermassive black holes (SMBHs) and the parameters of their bulges. Unlike other authors, we consider only spiral galaxies. In this paper, we present empirical formulas derived from observations of 54 spiral galaxies, establishing connections between the mass of the central black hole (MBH), the bulge stellar mass (Mbulge), and the velocity dispersion (σ) of stars in it. A non-linear non-stationary disk model with an anisotropic velocity diagram is constructed. Within this model, the instabilities of individual perturbation modes are studied. The increments of instability are calculated depending on the physical parameters of the model. These values are compared across three perturbation modes. The paper is partly based on the report presented at the conference “Modern Stellar Astronomy-2022,” held at the Caucasian Mountain Observatory of the Sternberg Astronomical Institute of Lomonosov Moscow State University, on November 8–10, 2022.

Determining a flow structure in the region of local obstacles of different types taking into account the hydrodynamic conditions for entering the initial section

This paper investigates the influence of hydrodynamic conditions for entering the initial section of the channel located after local obstacles of various types. It is shown that the head losses in the valves and bends of pipelines and in various control elements can be several times higher than those in straight sections of the pipeline. It was established that the assumption about the rectangular shape of the velocity diagram at the entrance to the hydrodynamic initial section does not correspond to the flow pattern in real channels of technological equipment. It is proved that with the manifestation of inertia forces in the flow at the initial section of the channel, hydrodynamic energy losses usually increase, velocity and stress fields are significantly deformed. Given this, it seemed expedient to conduct a study into the processes of flow of viscous liquids in the initial section, located after local obstacles of various types. Experimental and analytical studies have confirmed that there is a significant influence of boundary conditions at the entrance to the initial section on the formation of velocity diagrams and energy loss along its length. The analytical-numerical solution to the system of differential equations describing such flow is given. While solving, the system of equations, by appropriate transformations, takes the form of a nonlinear integral-differential equation. This makes it possible to obtain correct dependences for determining the length of the velocity distribution and energy loss in the investigated section of the channel. The results of calculations of velocity fields in the region of local obstacles agree well with known ideas of the flow pattern, which is observed in physical experiments and the results of analytical solutions. The quantitative difference in results ranges within 12–20 % depending on the Reynolds number. Thus, there is reason to assert that the results of studies reported here could be the basis for devising a procedure of hydrodynamic calculation aimed at structural and operational improvement of existing and designed technological equipment.

Star-forming site RAFGL 5085: Is a perfect candidate of hub-filament system?

To investigate the star-formation process, we present a multi-wavelength study of a massive star-forming site RAFGL 5085, which has been associated with the molecular outflow, Hii region and near-infrared cluster. The continuum images at 12, 250, 350 and 500 $$\mu $$ m show a central region (having $$M_\textrm{clump}\sim 225$$ $$M_{\odot }$$ ) surrounded by five parsec-scale filaments, revealing a hub-filament system (HFS). In the Herschel column density ( $$N(\textrm{H}_{2})$$ ) map, filaments are identified with higher aspect ratios (length/diameter) and lower $$N(\textrm{H}_{2})$$ values ( $$\sim $$ 0.1– $$2.4 \times 10^{21}$$ cm $$^{-2}$$ ), while the central hub is found with a lower aspect ratio and higher $$N(\textrm{H}_{2})$$ values ( $$\sim $$ 3.5– $$7.0 \times 10^{21}$$ cm $$^{-2}$$ ). The central hub displays a temperature range of [19, 22.5] K in the Herschel temperature map, and is observed with signatures of star formation (including radio continuum emission). The JCMT $$^{13}$$ CO(J $$=$$ 3–2) line data confirm the presence of HFS and its hub is traced with supersonic and non-thermal motions having higher Mach number and lower thermal to non-thermal pressure ratio. In the $$^{13}$$ CO position–velocity diagrams, velocity gradients along the filaments towards the HFS appear to be observed, suggesting the gas flow in the RAFGL 5085 HFS and the applicability of the clump-fed scenario.

Technical safety of buildings around polish quarries against harmful seismic vibrations caused by rock blasting

This paper presents the results of measurements of the elliptical distribution of seismic vibrations generated during rock blasting.The technical safety of a building in the area of seismic vibrations is determined by the vibration velocity that does not exceed the line B included in zone II of the scale of dynamic influences [SWD]. The hypothesis proved in the paper is that for both elliptical and circular distributions of the vibration velocity in rock mining with blasting material [BM] there is a directionality of the horizontal radial component Vx and the tangential component Vy of the vibration velocity.The magnitude of the components Vx and Vy of the vibration velocity at the same distance from the vibration source depends on the directional angle "α" between the line of the blast holes and the line connecting the centre of the surface of the rock block being mined with [BM] and the place of measurement. The elliptical shapes of the graphs Vx and Vy obtained during the mining of the BM of the basalt deposit, which depend on the value of the directional angle, were compared with the shape of the circular velocity graphs Vx and Vy. New correlations are given that take into account the directional angle when calculating the maximum vibration velocity values needed to determine the damage caused to a bulding by the SWD.A dynamic impact scale [SWD] for the assessment of building damage as the vibration velocity acting on the building increases is given and discussed. Vibration velocity diagrams measured during the excavation of BM rock are presented for circular distributions in accordance with theoretical predictions. A vibration velocity diagram for an elliptical distribution, inconsistent with a circular distribution, measured during the excavation of BM rock is presented. It is shown that the directionality of the horizontal radial and tangential components of vibration velocity exists for both circular and elliptical distribution of vibration velocity in rock excavation with BM. In the conclusions, for the elliptical velocity field of the vibrations, the conditions to be observed in order to be able to direct the smallest vibrations towards the built up area are given.

FAST discovery of an extra plume in DDO 168

ABSTRACT With the aim to study the extended H i environment around dwarf galaxies in the local universe, we performed a high-sensitivity H i observation of the DDO 168 and DDO 167 pair using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). We chose this pair as previous studies indicate that DDO 168 might have undergone an interaction with a local companion. Based on this deep observation, no new extra gas was found around DDO 167 and it was hardly resolved by FAST. On the other hand, on the north side of DDO 168 we discovered an extended plume of H i gas which has never been detected before. The plume has a ring-like structure with a radius of about 5.0 kpc and its gas mass is estimated to be 5.2 × 107 M⊙. The expanding velocity of the plume is about 30 km s−1, corresponding to a dynamical age of about 200 Myr. The position–velocity (PV) diagrams cut through the two galaxies show a short and pronounced ‘spur’ pointing to DDO 167 from DDO 168, indicating a tidal interaction between the two galaxies. We also found an H i knot in the plume. The gas mass of the knot is about 9.5 × 106 M⊙. This value is much higher than its virial mass, indicating the knot is gravitationally unstable and star formation will take place there in the future. Our study suggests that the ring-like structure of the plume might be caused by the passage of DDO 167 through the outer disc of DDO 168 about 200 Myr ago. We also discussed other plausible scenarios for the origin of the plume.

Bandgap tuning and in-plane wave propagation of chiral and anti-chiral hybrid metamaterials with assembled six oscillators

In this paper, a hybrid acoustic metamaterial consisting of chiral and anti-chiral ligaments is proposed. The bandgap properties of the hybrid chiral and anti-chiral structure with and without oscillator intercalation are calculated using Bloch’s theorem and the finite element method, and the structure is verified and evaluated to have good vibration attenuation performance by means of transfer functions and stress clouds. By adjusting the resonant oscillator configuration and applying active strain, the structure is verified to have tunable capability, which provides a simple and easy scheme for bandgap tunability analysis. Finally, a comprehensive analysis of the structural vibration mode, phase constant plane, group velocity, phase velocity and wave propagation direction diagram lead to the conclusion that the directional and regional nature of wave propagation is responsible for the bandgap opening. The new structure in this paper provides a new way of thinking for vibration and noise reduction, and also provides a practical solution for bandgap adjustment. The comprehensive analysis of wave propagation also presents theoretical and technical support for the subsequent structure and bandgap optimization.

Semi-Active Vibration Control of Seat Suspension Equipped with a Variable Equivalent Inertance-Variable Damping Device

The seat suspension has a significant influence on riding comfort in many practical applications, such as heavy duty vehicles, military vehicles, and high-speed crafts. This paper proposes a seat suspension equipped with a variable equivalent inertance-variable damping (VEI–VD) device and a novel semi-active vibration control strategy. The VEI–VD device can control its equivalent inertance and damping by controlling two external resistors in its electric circuit. Especially, the VEI part of the device can store and release vibration energy via the inside flywheel, which enables the seat suspension to have a four-quadrant controllable capability in the available force–velocity diagram, similar to an active system. First, the dynamic model of the VEI–VD device is built, and a prototype is developed and tested to identify the model parameters and verify its characteristics. Then, a semi-active vibration control method is proposed for the VEI–VD seat suspension. The control method uses a sliding mode controller to acquire the desired control force for reducing vibration; then, according to the desired force and system states, the VEI–VD device is tuned by a force-tracking scheme to generate a real force. In the numerical validation, the vibration transmissibility of VEI–VD seat suspension around its natural frequency is tested with different states. The effectiveness of force-tracking control strategies for different types of suspensions is verified. In the random excitation test, the root means square acceleration of the VEI–VD seat is reduced by 30.72% compared with a passive seat. The VEI–VD seat suspension shows great potential in applications.

A Stage Flow Parameter Analytical Model for Transonic Counter-Rotating Compressor and Its Application

This paper proposes a stage flow parameter analytical model for rapid evaluation of a counter-rotating compressor’s performance for design optimization and its application in the design of a transonic counter-rotating fan. In the first part, the velocity diagram method, considering the influence of flow-path geometry variation for enhancing the accuracy, is used to correlate the aerodynamic parameter between the inlet guide vane (IGV), the upstream rotor (R1), and the downstream CR rotor (R2). A profile loss correlation based on Lieblein’s diffusion factor and a shock loss model from a high-speed fan database are incorporated for predicting the rotor efficiency. In the second part, to verify its effectiveness, the analytical model is used for aiding in the aerodynamic design of a transonic CR fan for indicating the optimized combination of design parameters for good efficiency and a high pressure ratio. According to the analytical model and the simulation results, the final selected samples have higher efficiency, with a moderate pressure ratio (0.949/2.67, 0.890/2.99, and 0.841/2.99 for R = 0.1, 0.5, and 0.9, respectively). Finally, the aerodynamic characteristics of the designed transonic CR fan at a relative rotating speed of N = 1.05~0.8 are calculated by using the CFD software Numeca. Simulations indicate that the designed transonic CR fan has a pressure ratio of 2.76, with an efficiency of 0.8405 at the design point, and the efficiency is maintained above 0.821 with a stall margin of 13.3% for N=1.0. The maximum pressure ratio of this CR fan reaches 3.08 and 3.36 for N = 1.0 and 1.05, respectively. If used to provide thrust, calculations indicate that the thrust of this transonic CR fan is 71.8, 65.9, and 35.8 kN for N = 1.05, 1.0, and 0.8 at the near-choke point for the sea-level condition.

Conceptual design modeling by the novel aircraft conceptual design and analysis system (ACDAS)

PurposeThroughout an aircraft development process, the conceptual design phase is an extremely important milestone; hence, the quality and success of this step directly affect the overall cost and lead time of the project. Because of this fact, the purpose of this study is to provide outputs and suggestions to the designing engineer regarding the requirements for reducing overall design time as well as costs and creating an ideal design at the early phases of the project by optimizing the aircraft development process.Design methodology approachThe system has been prepared parametrically and presents some performance specifications for the aircraft in the early phases of the design, for example, coefficients for lift CL as well as drag CD and weight as well as fuel estimations. The software uses a combination of well-known design techniques within just one platform in contrast to many other applications. Because of this feature, it is not needed to use different sub-platforms which would require an appropriate environment and even though would lead to complications with regard to the connectivity. The system also presents relevant information about the aircraft performance like velocity versus load factor (V-n) diagrams, maximum turn rate of climb, turn rate and climb angle graphs in contrast to many other open-source conceptual design platforms.FindingsIn this study, authentic General Dynamics F-16 Fighting Falcon and McDonnell Douglas F-15 Eagle data were used as input to the system, and advanced geometric and/or performance graphs were obtained and compared to the literature where a good agreement of the results was observed. These results with regard to the aircraft performance are typically product specific and quite rare in the literature. These data obtained by use of the software during the aircraft design are, thus, of major interest, especially for the design of new aerospace platforms. In this study, all of these graphs (especially the remarkable V-n diagram) are obtained on one platform.Originality valueThe aircraft conceptual design and analysis system software provides information and suggestions regarding the requirements for reducing the overall design time, reducing the design costs and creating an optimized design at the early phases of a project by optimizing the aircraft development process within just one convenient, that is, user friendly, platform, where it uses a combination of varying methodologies. Besides presenting one interface, which is quite typical for conceptual design tools, it allows applications of methods like vortex lattices and finite differences for obtaining aerodynamic performance parameters.

A Unified Model for Bipolar Outflows from Young Stars: Kinematic Signatures of Jets, Winds, and Their Magnetic Interplay with the Ambient Toroids

Kinematic signatures of the jet, winds, multicavities, and episodic shells arising in the unified model of bipolar outflows developed in Shang et al. (Paper I), in which an outflow forms by radially directed, wide-angle toroidally magnetized winds interacting with magnetized isothermal toroids, are extracted in the form of position–velocity diagrams. Elongated outflow lobes, driven by magnetized winds and their interplay with the environment, are dominated by extended bubble structures with mixing layers beyond the conventional thin-shell models. The axial cylindrically stratified density jet carries a broad profile near the base, across the projected velocity of the wide-angle wind, and narrows down along the axis with the collimated flow. The reverse shock encloses the magnetized free wind, forms an innermost cavity, and deflects the flow pattern. Shear, Kelvin–Helmholtz instabilities, and pseudopulses add fine and distinctive features between the jet–shell components, and the fluctuating jet velocities. The broad webbed velocity features connect the extremely high and the low velocities across the multicavities, mimicking nested outflowing slower-wind components. Rings and ovals in the perpendicular cuts trace multicavities at different heights, and the compressed ambient gap regions enrich the low-velocity features with protruding spikes. Our kinematic signatures capture the observed systematics of the high-, intermediate-, and low-velocity components from Class 0 to II jet–outflow systems in molecular and atomic lines. The nested shells observed in HH 212, HH 30, and DG Tau B are naturally explained. Outflows as bubbles are ubiquitous and form an inevitable integrative outcome of the interaction between wind and ambient media.

KINEMATIC CALCULATION OF VARIABLE CURVATURE FIST MECHANISM WITH CONVEX PROFILE

In order to take into account more boundary conditions, a new modified equation was obtained to establish the profile of the fist by adding a constant to the equation obtained from the solution of the differential equation of curvature (i.e., k < 0 - convex profile surface as a special case). Based on this equation, the expression defining the movement of the pusher based on the rotation angle of the fist was deduced. The kinematic report of the punching mechanism was performed on the basis of a modified formula. During the kinematic calculations, it was found that there are no jumps in the displacement, velocity and acceleration diagrams of the pusher, that is, the mechanism works smoothly. In order to verify that the curvature takes a negative value along the profile, the equation of the curvature was deduced, its graph was plotted and its accuracy was confirmed.

Low‐Frequency Vibration and Noise Reduction and Wave Propagation Properties of Hexagonal Hybrid Metamaterials with Local Resonance Strips

Based on the idea of local resonance, a class of hybrid acoustic metamaterials with interposed resonant strips is proposed in this article, and the bandgap characteristics and transmission properties are calculated by combining Bloch's theorem and lattice theory. The new structure is verified to have low‐frequency damping and noise reduction capability through the analysis of the stress cloud diagram at specific frequencies in the bandgap range. A comprehensive analysis of vibration modes, phase constant surfaces, group velocity, phase velocity, and wave propagation direction diagram is used to explore the wave propagation and bandgap opening mechanism, providing technical support and theoretical basis for subsequent bandgap optimization and structural improvement. The results show that this structure can open multiple bandgaps in the low‐frequency range below 500 Hz, and the stepped design of the single‐cell structure and the introduction of resonant strips provide a new design idea for low‐frequency vibration and noise reduction.

Sample Intercorrelation-Based Multidomain Fusion Network for Aquatic Human Activity Recognition Using Millimeter-Wave Radar

To address the issue that existing multi-domain fusion methods do not consider data correlation within mini-batch data, the first attempt is made in this letter to propose a method based on sample inter-correlation learning multi-domain fusion network (SIMFNet), which aims to accommodate multivariate domain data and further enhance the aquatic human activity recognition performance. To fully utilize the radar multidimensional information, the three-branch convolution neural network (CNN) feature extractor is first employed to extract domain-specific features from the time-range map (TRM), time-Doppler map (TDM) and cadence velocity diagram (CVD). Then, the multi-domain features are fused and fed into the graph construction layer (GCL) to generate instance graphs. Next, a graph aggregation layer (GAL) is applied to aggregate node information from various-hop neighborhood domains. Finally, node-level classification is used to achieve aquatic human activity recognition. The experimental results evaluated on the built aquatic human activity recognition dataset demonstrate that the proposed SIMFNet has better generalization performance than the state-of-the-art multi-domain fusion methods.

Large-scale CO (J = 1–0) Observations toward the M120.1+3.0 Molecular Cloud: A Filament with a Chain of Starburst Clusters

We present large-scale (2° × 2°) observations toward the molecular cloud M120.1+3.0, using 12CO, 13CO and C18O (J = 1 − 0) data from the Purple Mountain Observatory 13.7 m millimeter telescope. The distance of the cloud is measured to be ∼1.1 kpc. Using the 13CO data, we identify a main filament F1 and two sub-filaments F2 and F3 in the cloud, which together show a “hub-filament” structure. Filaments F1 and F2 are thermally supercritical. Furthermore, F1 displays clear localized systematic motions in the 13CO position–velocity diagram, which could be explained by accretion along the filament. The mean estimated accretion rate is ∼132 M ⊙ Myr−1. Approximately 150 13CO clumps are identified in the cloud, of which 39 are gravitationally bound. Most of these virialized clumps are well distributed along the supercritical filaments F1 and F2. Based on the complementary infrared and optical data, we identify ∼186 young stellar objects in the observed area and extract five clusters within the dense ridge of F1. The calculated star formation rate (SFR) surface densities (ΣSFR) in the clusters range from 1.4 to 2.5 M ⊙ Myr−1 pc−2, with a mean value of ∼2.0 M ⊙ Myr−1 pc−2. We therefore regard them as mini-starburst cluster candidates. The comparison between ΣSFR and column density N gas along the skeleton of F1 suggests that star formation is closely related to the dense gas in the cloud. Along the main filament F1, five bipolar outflows are also found. All these results indicate intense star-forming activities in the M120.1+3.0 molecular cloud.

Modelling the CO streamers in the explosive ejection of Orion BN/KL region

ABSTRACT We present reactive gasdynamic, axisymmetric simulations of dense, high-velocity clumps for modelling the CO streamers observed in Orion BN/KL. We have considered 15 chemical species, a cooling function for atomic and molecular gas, and heating through cosmic rays. Our numerical simulations explore different ejection velocities, interstellar medium density configurations, and CO content. Using the CO density and temperature, we have calculated the CO (J = 2 → 1) emissivity, and have built CO maps and spatially resolved line profiles, allowing us to see the CO emitting regions of the streamers and to obtain position velocity diagrams to compare with observations. We find that in order to reproduce the images and line profiles of the BN/KL CO streamers and H2 fingers, we need to have clumps that first travel within a dense cloud core, and then emerge into a lower-density environment.

Numerical investigation of wave interaction with two closely spaced floating boxes using particle method

This paper applies Improved Meshless Local Petrov-Galerkin method based on Rankine source function (IMLPG_R) to simulate two-dimensional wave interaction with two closely spaced floating boxes. The present study considers four different box configurations based on the degree of freedom, namely FF (both boxes fixed), HH (only heave allowed), RR (only roll allowed), and MM (both heave and roll allowed). The influences of the different degrees of freedom of the boxes on the wave elevation in the gap, and forces acting on the boxes, are investigated. Regular waves with a wave period ranging from 0.6s to 1.6s and two focused wave groups based on the JONSWAP spectrum with a peak frequency of 0.869Hz and 1.081Hz, respectively, are employed for the analysis. The piston mode resonance frequencies of different configurations were observed to vary slightly depending on the motion restrained. Compared to the FF configuration, the MM configuration showed a 28.3% increase in wave amplification in the gap. Some unique characteristics observed in the response amplitude operator (RAO) and flow patterns around the boxes are explained using instantaneous velocity and vorticity diagrams. The response of various configurations under a nonlinear transient-focused wave is also examined. The first-order and second-order time series of wave elevation in the gap is obtained by using the four-phase combination method.

The Dynamics of the Outflow Structure in W49 N

AbstractIn this current study, we report only the preliminary result of the SiO v=0 Ј=5→4 emission toward W49 N at 230 GHz, observed using the ALMA telescope on September 29, 2018. The position–velocity diagram of the SiO emission shows a structure of a bipolar outflow and has a face-on orientation with an inclination angle of 36.4±0.4 degrees with respect to the line of sight. Here we summarize the calculated physical properties of its outflow.

Evaporation-induced deposition morphology of suspension droplets on hydrophobic surfaces manipulated by controlling the relative humidity

The deposition morphology of drying suspension droplets has attracted significant attention due to its practical applications in inkjet printing, painting, and coating technologies. In this study, the deposition morphology of silica/polystyrene suspension droplets on hydrophobic surfaces is explored and manipulated by controlling the relative humidity. The deposits are ring-like for the silica suspension droplets and become thicker and smaller under higher relative humidity. On the other hand, a uniform deposition is observed for the polystyrene suspension droplet evaporated at a relative humidity of 15%, i.e., the coffee ring effect is suppressed simply by manipulating the relative humidity. We applied a mass conservation model incorporated with the image analysis of an evaporating droplet to calculate the capillary flow velocity distribution inside a three-phase-contact-line (TPCL) shrinking droplet. The capillary flow velocity is higher when the relative humidity is lower. While the capillary flow velocity is higher to bring more particles towards and accumulate along the TPCL of the droplet, and the particles would pin the droplet earlier. The capillary flow velocity diagram also shows that the velocity is higher at the beginning of the mixed mode in the evaporation process and when the droplet starts to self-pin (at the end of the mixed mode) along the TPCL.

Effect of asymmetrical orifice inlet geometry on spray kinematics and development

In diesel engines, fuel injection has a commanding effect on combustion. Thus studying diesel spray characteristics is beneficial for controlling and improving diesel combustion. However, information on diesel spray characteristics, especially those governed by injector needle lift, is lacking. This study investigates the near-nozzle spray kinematics for particular nozzle geometries over a range of injection pressures. The nozzles used in this research include a single-hole off-axis nozzle and a two-hole nozzle with deviated orifices. This study aims to observe the effect of asymmetrical orifice inlet on the spray kinematics and describe how sensitive they are to the injection pressure. First, we applied double-pulses time-gated ballistic imaging to obtain well-defined spray/gas interfaces. Then, by tracking these interface structures, we obtained spray kinematics. The results show that the two-hole nozzle generates slower sprays than the single-hole nozzle at the beginning of injection. However, the velocity differences between these sprays become less significant as the sprays develop to a quasi-steady state. In addition, the velocity diagrams show that the instabilities cause the flow to experience significant velocity alterations at the beginning of the injection. Moreover, we observed that the nominal spray axis shifts towards the sharper orifice inlet edge, which will affect the spray targeting. Finally, the injection pressure seems to have minimal effect on the spray profile, but it certainly changes spray evolution timing and shortens the transient phase.