Motion Phenomena Research Articles

Entropy production analysis for vortex rope of a Francis turbine using hybrid RANS/LES method

The precessing vortex core in the draft tube of Francis turbine is investigated using entropy production method. The high-fidelity Delayed Detached Eddy Simulation (DDES) method with SST k-ω turbulence model is used to acquire the entropy dissipative components of the flow, and the Q-criterion is selected to evaluate the vortex cores inside the draft tube under different operating conditions, separately. The results show that the numerical simulation is in good agreement with the experimental data obtained from the model test. It is found that the vortex motion, separation flow and shock phenomenon are considered to be hydrodynamic factors for the formation of entropy. Furthermore, draft tube accounts for the greatest proportion of entropy production, which is ascribed to the vortex rope. Vortex rope will rotate in the same direction as the runner, but the rotational speed is lower, resulting in low frequency pressure pulsation with large amplitude in the draft tube. It is concluded that the key reason why great energy dissipation is caused in the draft tube is that the vortex rope is transporting continuously towards the downstream, especially when the turbine deviating from optimum operating point.

LONGITUDINAL TRAP OF ELECTRON BEAM IN POTENTIAL PIT MAGNETIC SOLENOIDAL FIELD

A two-mode cylindrical magnetic field is considered, the potential of which has a minimum. The object of this work is the study of the parameters of an electron beam when it moves in a solenoid field with the longitudinal trap formed by the magnetic field, and the construction of the computational model of the motion of an electron beam. The problem is posed of the stability of the motion of electrons in such solenoid magnetic field. The possibility of obtaining oscillatory modes of particle motion has been studied. It was found that for oscillations of particles with an energy of tens of kiloelectronvolts in the potential well in a well, the field with the amplitude of tens of thousands of Oersteds is required. For the solenoid magnetic field of the solenoid, the formation of electron beam with an energy of 55 keV in the longitudinal and radial directions during its transportation is studied. A section of a magnetron gun was used as the physical object. One possible direction is to combine the two matched magnetic systems of the gun to create the potential magnetic field well. It is shown that, for the chosen conditions, the motion of electrons can be associated with the model of three-dimensional oscillations. In this work, on the basis of the Hamiltonian formalism of the motion of electrons in a magnetic field and an algorithm for numerically finding solutions to the differential equations of dynamics, a software tool is constructed that allows one to obtain arrays of values of particle trajectories in the volume. The use of the software made it possible to simulate the main dependences of the motion of the electron beam in a given two-mode solenoid magnetic field. The results of numerical simulation of electron trajectories in the gradient magnetic field with the point secondary emission cathode located in the middle of the system are presented. The formation of the beam with energy of 55 keV in the radial and longitudinal directions during its transportation in a solenoid magnetic field with a large gradient is considered. For significant time intervals, the possibility of three-dimensional oscillations is shown and the operating modes of the magnetic system are obtained, in which the particle undergoes stable three-dimensional oscillations. The influence of the initial conditions during emission on the occurrence of the reciprocating oscillatory effect has been studied. It is shown that for a given electron energy and fixed magnetic field, the parameter that determines the reflection of a particle, is the polar angle of entry relative to the axis of the cylindrical magnetic field. The dependence of the formation of the final distribution of particles on the amplitude and gradient of the magnetic field along the axis of the system is investigated. The results of numerical simulation on the motion of the electron flow are presented. The characteristics of the resulting electron beam are considered on the basis of a model of electron flow motion. The obtained simulation results show that it is possible to establish the phenomenon of oscillatory-return longitudinal motion under experimental conditions.
 Keywords: electron beam, magnetron gun, three-dimensional oscillations, electron dynamics, gradient magnetic field, mathematical modeling.

Numerical Investigation on the Thermal Performance of Three Advanced Micro Heat Pipes

Three micro heat pipes belonging to different types are selected as the research objects due to their lowest thermal resistance and the steadiest operation according to published literatures. They are the pulsating heat pipe with corrugated configuration (CPHP), the flat-plate heat pipe with eight microchannels (FPMHP) and the radial pulsating heat pipe (RPHP). A mathematical model common to the three micro heat pipes is built, and the maximum deviation between simulation and actual results is 16.1%. It is found that CPHP has the best heat transfer performance with the minimum thermal resistance of 1.14 K·W−1. Its average wall temperature and center-line velocity regularly oscillate after the start-up point. There is a pause phenomenon of motion for CPHP, and the pause period of motion decreases from 8.93 s to 7.25 s with the increasing input heat flux. RPHP possesses the most excellent temperature uniformity with the maximum axial temperature difference of 5.24 K. Furthermore, FPMHP is suitable for cooling temperature-resistant devices because its average wall temperature of evaporation section is the highest.

Thermal analysis for axisymmetric stagnation point flow of viscoelastic magnetised nanofluid over a lubricated disk

This numerical study elaborates on the impacts of non-linear thermal radiation, Ohmic heating quadratic chemical reaction, an applied magnetic field on thermal characteristics of an axisymmetric flow of viscoelastic fluid in the vicinity of the axisymmetric stagnation point of a lubricated disk. The phenomena of the Brownian motion and thermophoresis with zero mass flux condition are also taken into account. The similarity transformation is used to reduce the number of independent variables in governing boundary layer equations and the transformed system of boundary value problem is solved using the box method. Variation in axial velocity, temperature and concentration profiles for various involved parameters of interest are graphically presented and categorically discussed. The local Nusselt number is documented for linear and non-linear radiations, whereas the Sherwood number is presented for linear and quadratic chemical reactions. It is observed that lubrication enhance both heat and mass transfer rates.

The birth of motion capture: Transcribing the phenomena of bodily movement through the “graphic method”

How is the movement of bodies recorded, traced, captured? How is the perception of movement decomposed, analyzed, and then reconstructed through signs, lines, and diagrams? This article traces how, with the help of engineers and collaborators, Etienne-Jules Marey’s self-styled “graphic method” innovated upon existing instruments and photographic apparatuses in order to capture not just the movement of horses’ legs but something of the biomechanical essence of animal movement through the technique of “chronophotographie.” Although inspired by Edward Muybridge’s photographs of horses in motion, for Marey the photographs were not the end result. What he achieved were new ways of transcribing the phenomena of bodily motion. Unlike previous physiologists who thrived on vivisection in the laboratory, Marey took ever greater pains to examine the principles of animal movement in the wild, and built an open-air “station physiologique” in a Parisian park for this purpose. One legacy of Marey’s chronophotographic technique was in the documentation and dissection of human movement, and became acknowledged precursors of the wave of Taylorism which would sweep industrial research in the early 20th century. But another legacy is the capacity to transcribe the phenomena of movement into other forms, externalizing perception across other media.

Application of microseismic methods for identification of ground movement potential in Cemara sub-village, Sukorejo village, Gunungpati Semarang

Based on data of landslide from Regional Disaster Mitigation Board (BPBD), Sukorejo village is one of three urban villages in Gunungpati which has a high potential possibility for disaster, particularly landslide. One of the areas in Sukorejo Village that frequently sustains of land movement is Kampung Cemara. On April 23, 2018 in Kampung Cemara, a landslide occurred which caused detrimental damage to buildings. Several other accidents signified ground movement resulting cracks in the land surface. The high level of losses is not only induced by the magnitude of the disaster, but also due to inadequate information related to the potential for disasters and conditions in the area, that it decreases public awareness of the environment. That is the main reason for this micro seismic research. Micro seismic is a geophysical method which employ to determine the ground motion potency through the subsurface layer characteristics by calculating the value of Ground Shear Strain (GSS). The data processing is using the HVSR method. The value was ranged from 4.54 × 10−3 to 1.59 × 10−2. The result represents that Kampung Cemara is considerably potential to undergo land movements with plastic-elastic soil properties and ground motion phenomena that can effect vibration and cracks in surface land and habitation.

Mixed convection and melting rheology in dual stratified Eyring-Powell nanofluid flow over surface of variable thickness: Buongiorno model approach

Eyring Powell fluid flow over linear as well as nonlinear stretching surfaces has been discussed in literature by several researchers. However, lesser attention has been paid for such studies with surfaces comprising variable thickness. Present communication inculcates the novel features regarding melting heat transport in Eyring Powell nanofluid over a surface of variable thickness while keeping in view the aspects of radiative heat transfer. Influence of thermophoresis and Brownian motion phenomena is discussed by making use of Buongiorno model approach. Here, the flow characteristics are analyzed in mixed convective and dual stratified porous medium. Appropriate transformations are imposed in order to convert partial differential equations to ordinary differential equations possessing highly nonlinear form. Homotopy analysis method is utilized to achieve desired convergent series solutions. Impact of several emerging variables on velocity temperature and concentration distributions is analyzed graphically. Expressions for drag force and rate of heat transfer are evaluated and demonstrated graphically. Nano particle concentration increases for higher Brownian motion parameter. Enriched thermal field is attained due to rise in thermophoretic parameter. However, recessive behavior of velocity profile results due to higher fluid parameters. Thermal field rises as a result of larger values of mixed convection parameter while it decays gradually for enhanced melting parameter.

Verification and Validation of Transient Body Force in GOTHIC for Spent Fuel Pool Response to Seismic Events and Other Applications

Post Fukushima the U.S. Nuclear Regulatory Commission issued an Order on Spent Fuel Instrumentation (EA-12-051) requiring all U.S. nuclear plants to install spent fuel pool (SFP) water level monitoring instrumentation and ensure the instrument would remain functional following a safe shutdown earthquake (SSE). The structural integrity analysis requires an assessment of the hydrodynamic loads and wave impact forces that the instrument is subjected to during an SSE. Modeling and simulation of the SFP response to an SSE can provide this type of information if the simulation tool is able to capture the important physical phenomena, such as seismic acceleration, surface wave formation, fluid velocities, and multidimensional effects. This paper describes the capabilities of GOTHICTM that can be used to simulate the sloshing surface waves and subsurface fluid motion of an SFP in response to an earthquake. GOTHIC is a versatile, general-purpose, thermal-hydraulic software package for multiphase flow that is a hybrid between traditional system thermal-hydraulic and computational fluid dynamics codes. It includes a transient, variable body force capability to simulate multi-axis acceleration, and is therefore applicable to seismic events; movement experienced on ships, airplanes, or spacecraft; and other events with system acceleration. Also, since the gravitational constant can be adjusted, GOTHIC can model systems placed outside the Earth’s atmosphere (e.g., spacecraft, space station, the Moon, or other extraterrestrial bodies). The variable body force capability makes GOTHIC well suited to model the hydrodynamic response of an SFP to a seismic event. This paper describes the governing equations that are solved by GOTHIC as they pertain to accelerating systems. A series of benchmarks covering a range of experiments for surface wave dynamics, acceleration-induced motion, and other important phenomena are presented to demonstrate the verification and validation of GOTHIC for these types of applications. Finally, results from a sample application of GOTHIC for SFP hydrodynamic response are presented that provide the necessary inputs for a structural integrity analysis.

Hydrodynamic aspects of tsunami wave motion: a review

Since the 2004 Indian Ocean tsunami and particularly after the 2011 Tohuku tsunami, there has been a significant increase of computer simulation using real-time data; however, there are evidences of failures in pre-disaster preparedness. The scientific challenges to mitigate tsunami hazards rely heavily on understanding the hydrodynamics of the motion. The problem with tsunami is that it grows beyond the natural boundaries of generation and covers many oceans confronting different physical parameters which not only makes it a real global event but also enhances the complexity of the event. In this article, one, the underlying physical phenomena of tsunami motion starting from generation to evolution is identified. Two, the linear and non-linear studies of wave propagation and the effect of several oceanic parameters to the basic motion are highlighted. Three, considering the importance of tsunami wave runup, its research both at the theoretical and computational level is thoroughly explained. Four, although the majority of tsunamis are earthquake or landslide generated, there are instances of tsunamis generated by other sources; a brief review in this regard is provided. Five, the importance of benchmark problems for developing modelling tools is imperative; an attempt is made to underscore the obstacles faced while implementing the new improvements in hazard mitigation. Six, new research avenues are explored based on lessons learned over the years.

Identifying the module structure of swarms using a new framework of network-based time series clustering

Swarm is a collective motion phenomenon whose dynamic mechanism and cooperation structure could be identified based on observations. Unmanned Aerial Vehicles (UAV) is a special artificial swarm with unique rules and structures. Therefore, corresponding identification methods need to be developed. One critical identification problem is distinguishing the swarm’s cooperation structure, which is usually clustered and grouped to achieve stability of behaviors and low communication cost. This paper proposes a framework of Overlay Network Integrated Time series clustering (ONIT) to identify the UAV swarm structures based on trajectories. The framework consists of Snapshot, Net Growth and Net Split. It can fuse with most distance functions in time series clustering, achieving high accuracy, update ability, and fault tolerance with various datasets. We create point-based and sliding window-based snapshots, allowing the framework compatible with more methods. In particular, the Dynamic Time Wrapping (DTW) correspondence in point-based snapshots shows the high scalability of the framework, and the Euclidean Distance (ED) correspondence shows that the framework can still significantly improve the accuracy while maintaining the simplicity of calculation. The test results show that the fused ONIT-clustering algorithms, especially the point-based ones, outperform original time series clustering methods separately in simulation datasets of UAV swarms and UCR repository by 28% and 27%. In summary, the proposed framework is a flexible and scalable time series clustering method that can solve various time series clustering problems especially the trajectory clustering of the UAV swarm and has great potential for general time series analysis.

Study of cathode-spot crater and droplet formation in a vacuum arc

A 3D transient model of a cathode-spot crater and droplet formation in a vacuum arc is developed. The model includes mass, momentum, heat transfer (energy), current continuity and potential equations. Using the energy flux density, current density and pressure as external parameters, the shape of the cathode-spot crater and the temperature, velocity, potential and current density distributions at each time step are determined via numerical simulation. Under symmetrical conditions, the 3D simulation results are highly consistent with those from the previous 2D model. The new cathode spot tends to appear in the direction in which the protrusion is largest because the liquid-metal velocity is lower and the liquid-metal ridge radius is larger in this direction. The effect of the external transverse magnetic field is considered by using a symmetric space function to represent the pressure and energy flux density of the plasma cloud. Simulation results show that even small changes in the plasma cloud distribution have a significant impact on the cathode-spot crater process and droplet formation. Since the pressure is asymmetric, the crater becomes asymmetric and the new cathode spot tends to appear opposite to the direction of the Ampere force. Based on this phenomenon, a possible explanation for the retrograde motion phenomenon of cathode spots is proposed.

Performance comparison of two motion modes of a piezoelectric inertial linear motor and its potential application in cell manipulation

The piezoelectric inertial linear motor (PILM) has great application potential in cell manipulation, location of artificial neural electrode, and other micro-operation fields for its advantages of fast response, long stroke, and high resolution. However, the traditional schemes have been challenging to avoid the phenomenon of backward motion, which may lead to motion instability and failure of positioning in cell manipulation. To solve this problem, a novel PILM with two motion modes is proposed. In this study, throughin-depthanalysis of steppingcharacteristics, the reason why the motor with the traditional “forward–backward” motion mode is difficult to eliminate the backward motion phenomenon by adjusting the friction force in experiments is revealed. Then, a series of performance evaluation and cell manipulation simulation experiments are carried out. Experimental results indicate that the novel “forward–forward” motion mode can solve the backward motion problem and has the advantages of the speed, efficiency, and stability of the system, while the “forward–backward” motion mode has the advantages of resolution and carrying capacity. Moreover, the proposed motor can switch between the two motion modes freely according to the different requirements of the application environment for obtaining the required specific performance. Based on the above advantages and the successful druginjection simulation process in a zebrafishembryo, the proposed motor has great application potential in cell manipulation and other micromanipulation fields.

Simulation of vacuum arc cathode spot movement between transverse magnetic field contacts

Vacuum switches have been extensively used in the field of medium voltage. Carrying out relevant research on vacuum arc is particularly important for improving the performance and reliability of vacuum switches. The vacuum arc cathode spots provide metal vapor and electrons, which determine the breaking capacity of the vacuum switches to some extent. Therefore, based on the simulation model of the cathode spots between the transverse magnetic field (TMF) contacts, the motion phenomenon and distribution of the cathode spot were simulated and the characteristics of the initial diffusion stage of cathode spots between TMF contacts were studied. The simulation results showed that the probability of generating a cathode spot in the direction of retrograde motion increased with the increase in the TMF component and the direction of motion varied with the angle between the magnetic field and the contact. The diffusion process of cathode spots under wan-shaped contacts, cup-shaped contacts, and spiral-shaped contacts was simulated. The ring-shaped distribution of the cathode spots between cup-shaped contacts with a large current in the initial diffusion stage was formed by the self-generated magnetic field of cathode spots, while the axial magnetic field component and the clustered cathode spots destroyed the ring-shaped distribution. Taking the distribution of cathode spots and current from experiments as initial conditions, the simulation results of cathode spot distribution in the initial diffusion stage and the arc root radius were consistent with the experimental results.

Analytical and numerical treatment to study the effects of hall currents with viscous dissipation, heat absorpation and chemical reaction on peristaltic flow of Carreau nanofluid

The peristaltic flow of Carreau nanofluid with heat and mass transfer through porous medium inside a symmetric horizontal channel with flexible walls is investigated. The Hall currents with viscous dissipation, heat absorption and chemical reaction are considered, the system is stressed by a uniform strong magnetic field. The problem is modulated mathematically by a system of non-linear PDE which describe the motion, heat and nanoparticles phenomenon of the fluid. These equations with subjected boundary conditions are transferred to a dimensionless form and simplified under the assumptions of long wavelength and low Reynolds number, then solved analytically by using perturbation technique for small Weissen-berg number. In other word these equations are solved also numerically by using Runge-Kutta-Merson method with Newton iteration in a shooting and matching technique. The effects of the emerging physical parameters of the problem on the velocity, temperature, and nanoparticles phenomena are discussed numerically for both techniques used for solutions and illustrated graphically through a set of figures. It is found that this problem plays a dramatic role in controlling the solutions. A comparison between the obtained solutions from both methods is made.

Parmenides and M. Karagatsis (Reflection of Myth in Fiction)*

The paper aims to show some structural parallels between the concept of motion as developed by Parmenides (5th c. BC) and the expression of the phenomena of motion in the story A Solitary Voyage to the Island Cythera by the Greek writer M. Karagatsis (1908–1960). The novelette of M. Karagatsis is interpreted as a parmenidean “motionless motion” reflexion. It is argued that M. Karagatsis’s story is structurally and essentially related to the Parmenidean poem On Nature, treating the consideration of motion as one of the impossible properties of being; and more obviously refers to certain poems by Constantine Cavafy (1863–1993), which also contain the idea of the meaninglessness of the difference between κίνησις and ἀκινησία. Thus, the concepts of κίνησις and ἀκινησία in the story by M. Karagatsis echo both the Parmenidean ideas and the Cavafy’s images of movement.

Transient flow of Maxwell Nanofluid Over a Shrinking Surface: Numerical Solutions and Stability Analysis

This article explores the theoretical analysis for thermal and mass transport of Maxwell nanofluid along permeable shrinking surface. The thermal and concentration configuration involve heat generation/absorption and chemical reaction in the flow regime. Brownian motion and thermophoresis phenomenon are considered in the mass transport analysis. This physical configuration is translated in terms of nondimensional differential system. A numerical investigation of the governing equations is carried out with Bvp4c technique in MATLAB. Further, it has been found that shrinking and suction at porous surface leads to multiple solutions of the system. The results in terms of line graphs portray that the stronger suction at shrinking surface possess higher heat and mass transfer rate at surface. The heat transfer rate enhances by the larger values of Biot number. Further, the velocity, temperature and mass distribution indicate maximum values at stronger relaxation parameter.

Mode locking phenomena of the current-induced skyrmion-lattice motion in microfabricated MnSi

Using voltage fluctuation spectroscopy, we observe the mode locking phenomena of current-induced skyrmion-lattice motion in microfabricated MnSi. When only a dc electric current is applied, the frequency of the emergent narrow-band noise (NBN) monotonously increases with increasing dc current. By contrast, if an ac electric current is further added, the NBN frequency becomes much less dependent on the dc current when it satisfies a simple integer ratio to the ac current frequency, a hallmark of mode locking. In the mode locked state, the linewidth of the NBN is sharpened, indicating the enhanced coherence of the skyrmion-lattice motion. The overall features of the mode locking phenomena are qualitatively reproduced within the framework of the classical rigid-sphere model.

Nature-inspired noise model accounts for a broad range of motion phenomena

Nature-inspired noise model accounts for a broad range of motion phenomena

Volterra-series approach to stochastic nonlinear dynamics: Linear response of the Van der Pol oscillator driven by white noise.

The Van der Pol equation is a paradigmatic model of relaxation oscillations. This remarkable nonlinear phenomenon of self-sustained oscillatory motion underlies important rhythmic processes in nature and electrical engineering. Relaxation oscillations in a real system are usually coupled to environmental noise, which further enriches their dynamics, but makes theoretical analysis of such systems and determination of the equation parameter values a difficult task. In a companion paper we have proposed an analytic approach to a similar problem for another classical nonlinear model-the bistable Duffing oscillator. Here we extend our techniques to the case of the Van der Pol equation driven by white noise. We analyze the statistics of solutions and propose a method to estimate parameter values from the oscillator's time series. We use experimental data of active oscillations in a biophysical system to demonstrate how our method applies to real observations and can be generalized for more complex models.

Influence of Soret and Dufour effect on MHD flow over an exponential stretching sheet: A numerical study

The present paper analyzes the effect of chemical reaction on free convection MHD motion of steady, laminar, incompressible liquid under the influence of heat source/sink. The motion is considered over an exponential radiative extending surface with a magnetic field. An appropriate similar transformation is employed to convert the nonlinear system of partial differential equations (PDEs) to a set of ordinary differential equations (ODEs). Due to the high nonlinearity, the analytical approach for these coupled nonlinear equations does not hold good. Therefore, these transformed ODEs are solved by using numerical techniques adopting Runge-Kutta fourth-order method accompanied by shooting technique. The behavior of different physical parameters on the motion phenomena is shown via diagrams. However, as a concluding remark, the major outcomes of the present investigation are described as: the buoyant forces overshoot the velocity profile significantly whereas the fluid temperature retards with an increasing Soret number. Finally, the chemical reaction parameter favors retard the concentration profiles resulted in reducing the thickness of the solutal boundary layer.