Modeling and Simulation of Supercavity with Inertial Force in the Horizontal Curvilinear Motion

To make a curvilinear motion in the horizontal plane is one of the most contents for realizing the maneuverability of the supercavitating vehicle. It is significant to achieve the controllability and maneuverability of the vehicle in three dimensions both theoretically and practically on research. Models of angle of attack, gravity and inertial force effects on the supercavity in the horizontal curvilinear motion are established, respectively. The supercavity is simulated based on these models in combination with Logvinovich model and the unsteady gas-leakage rate model at the given ventilation rate, and the effect of the inertial force on it is analyzed numerically. Results show that the maximum deviation of the center line of the cross section of supercavity towards the outward normal direction of its trajectory increases as the cavitation number or curvature radius decrease and always occur in the tail because of the increase of inertial effects along the axis of supercavity from the cavitator when other models and flow parameters are constant for the given trajectory curvature. For the variable curvature, the supercavity sheds due to its instability caused by the time-varying angle of attack. The deviation increases along the length of supercavity if the curvature remains the same sign.

The lubrication performance of water lubricated bearing with consideration of wall slip and inertial force

The lubrication mechanism and the performance parameters with consideration of wall slip and inertial force are studied in this paper. Based on the modified Reynolds equation, the finite difference method is used to study the lubrication mechanism and the performance. Effects of the wall slip and the inertial force on the performance parameters are obtained, and found in good agreement with the results of FLUENT. It is shown that the wall slip and the inertial force do not significantly change the distribution of the pressure, the load capacity and the friction force. The inertial force slightly increases the pressure and the load capacity by 1.2% and 4.8%, while the wall slip reduces them by 8.0% and 17.85%. The wall slip and the inertial force increase the friction by about 15.98%, 2.33%, respectively. Compared with the wall slip, the inertial force is smaller, but cannot be neglected.

Study of aerodynamic and inertial forces of a experimental and numerical methods

The force-generation mechanism of a dovelike flapping-wing micro air vehicle was studied by numerical simulation and experiment.To obtain the real deformation pattern of the flapping wing,the digital image correlation technology was used to measure the dynamic deformation of the wing.The dynamic deformation data were subsequently interpolated and embedded into the CFD solver to account for the aeroelastic effects.The dynamic deformation data were further used to calculate the inertial forces by regarding the wing as a system of particles to take into account the wing flexibility.The temporal variation of the forces produced by the flapping wing was measured by a miniature load cell.The numerical results provide more flow details of the unsteady aerodynamics of the flapping wing in terms of vortex formation and evolution.The calculated results of the inertial forces are analyzed and compared with the CFD results which represent the aerodynamic forces.In addition,the total forces,i.e.,the sum of the CFD result and inertial result,are compared with the experimental results,and an overall good agreement is obtained.

Inertial force balance and ADAMS simulation of the oscillating sieve and return pan of a rice combine harvester

To reduce the inertial force of the oscillating sieve and return pan of a rice combine harvester,partial equilibrium was adopted.Firstly,based on the kinematic analysis of a slider-crank mechanism,the appropriate mass of counterweight intervals was achieved.Then,an ADAMS dynamic simulation was used to determine the optimum balance mass of the oscillating sieve and return pan individually.Considering the relative motion between the return pan and the oscillating sieve,the overall inertial force of the two parts would be reduced.The simulation results indicated that the optimum counterweight of the oscillating sieve was 15.5 kg based on an analysis of the movement tracks of the mass center and overall inertial force.The results also showed that the overall balance of inertial force not only reduced the counterweight but also decreased the overall inertial force of the oscillating sieve and return pan.Finally,a search for the most suitable crank initial angle of the return pan to reduce the overall inertial force and optimize the overall balance revealed three groups of initial angles:φ=0°,φ=45°,andφ=90°.The results indicated that arranging the initial angle of the crank of the oscillating sieve and return pan in the same position(φ=90°)was the most favorable for reducing the overall inertial force.In this situation,the optimum counterweight of the oscillating sieve was only 14.0 kg.The results can provide references for the design of the overall balance of the inertial force in the cleaning components of a combine harvester.

SUPERCAVITY MOTION WITH INERTIAL FORCE IN THE VERTICAL PLANE

The curvilinear motion in a vertical plane is one of the most important features of the supercavitating vehicle. It is of great significance to study the controllability and the maneuverability of the supercavitating vehicle. Models are built for the effects of the angle of attack, the gravity and the inertial force in the curvilinear motion in the vertical p｜ane. Numerica~ simulations are carried out for the supercavity motion based on these models combined with the Logvinovich model. It is shown that the maximum deviation displacement in the outward normal direction of the trajectory with a constant curvature, which occurs in the tail of the supercavity, increases as the cavitation number or the curvature radius of the supercavity trajectory decreases under the condition that other model and flow parameters are kept constant. For a varied curvature, the supercavity shape changes evidently because of the change of the ambient pressure, but with the same trend as in constant curvature. The deviation displacement increases along the supercavity length gradually.

The Nature of Inertial and Vacuum Gravitational Field

The uniformly accelerated motion is studied in the framework of gauge theory of gravity. It is found that, when an inertial reference system is transformed into a uniformly accelerated system by a local gravitational gauge transformation, a non-trivial gravitational gauge field appears. If there is a mass point in the new reference frame, there will be a non-trivial gravitational force acting on it. The nature and the characteristic of this new force are completely the same as those of the traditional inertial force. This new gravitational force is considered to be the inertial force. Therefore, the nature of inertial force is gravity, which is the basic idea of the equi-valence principle.

Cardboard Eco-Bundle as an Alternative for Collation Shrink Film

Due to increasing pressure on brand owners and distributors to avoid single use plastics such as plastic bundle packaging, a new bundle packaging that consists of corrugated board only, has been designed. Obviously this new packaging should equally enable transportability. This study compares the transportability of bundles using corrugated board on the one hand and bundles using plastic collation shrink film on the other. In particular, the resistance to varying horizontal inertial forces is compared experimentally. All tested bundle packagings of corrugated board perform well above expectations and significantly better than shrink film packaging. All additional requirements regarding marketing, durability, consumer convenience, …are met.

Laminar Flow in the Gap between Two Rotating Parallel Frictional Plates in Hydro-viscous Drive

The velocity, pressure and temperature distributions of the flow in the gap between hydro-viscous drive friction disks are the key parameters in the design of hydro-viscous drive and angular velocity controller. In the previous works dealing with the flow in the gap between disks in hydro-viscous drive, few authors considered the effect of Coriolis force on the flow. The object of this work is to investigate the flow with consideration of the effects of centrifugal force, Coriolis force and variable viscosity. A simplified mathematical model based on steady and laminar flow is presented. An approximate solution to the simplified mathematical model is obtained by using the iteration method assuming that the fluid viscosity remains constant. Then the model considering the effect of variable viscosity is solved by means of computational fluid dynamics code FLUENT. Numerical results of the flow are obtained. It is found that radial velocity profile diverges from the ideal parabolic curve due to inertial forces and tangential velocity profile is nonlinear due to Coriolis force, and pressure has two possible solution branches. In addition, it is found that variable viscosity plays an important role on pressure profiles which are significantly different from those of fluid with constant viscosity. The experimental device designed for this work consists of two disks, and one of them is fixed. Experimental pressure and temperature of the flow within test rig are obtained. It is shown that the trend of numerical results is in agreement with that of experimental ones. The research provides a theoretical foundation for hydro-viscous drive design.

MODAL TEST AND ANALYSIS OF CANTILEVER BEAM WITH TIP MASS

The phenomenon of dynamic stiffening is a research field of general interest for flexible multi-body systems.In fact,there are not only dynamic stiffening but also dynamic softening phenomenon in the flexible multi-body systems.In this paper,a non-linear dynamic model and its linearization characteristic equations of a cantilever beam with tip mass in the centrifugal field are established by adopting the general Hamilton Variational Principle.Then,the problems of the dynamic stiffening and the dynamic softening are studied by using numerical simulations.Meanwhile, the modal test is carried out on our centrifuge.The numerical results show that the system stiffness will be strengthened when the centrifugal tension force acts on the beam (i.e.the dynamic stiffening).However,the system stiffness will be weakened when the centrifugal compression force acts on the beam (i.e.the dynamic softening). Furthermore,the equilibrium position of the system will lose its stability when the inertial force reaches a critical value.Through theoretical analysis,we find that this phenomenon comes from the effect of dynamic softening resulting from the centrifugal compression force.Our test results verify the above conclusions and confirm that both dynamic stiffening and softening phenomena exist in flexible multi-body systems.

Dynamic Analysis and Structural Optimization of a Novel Palletizing Robot

A novel palletizing robot is presented and developed.By using the Newton-Euler method and the principle that the instantaneous inertial force system could be transformed into a static system,the force equilibrium equations of the whole robot and its subsystem were derived and the robot＇s dynamic models were established.After that,an example simulation was performed by using Matlab software and the structural optimization of the robot＇s key parts were discussed and analyzed in ANSYS platform.The results show that the dynamic models are correct and can be helpful for the design,validation and kinetic control based on dynamics of this kind of palletizing robots.

Cosmogonic Speculations: Particle Creation from Energy Conservation in the Universe Evolution

Information about the Universe from Hubble’s law is consistent with that coming from the evaluation of inertial forces, supporting the picture of a steady state expansion of a black hole Universe. Backed up also by the consideration of the black body self energy, the post big bang temperature decrease is consistent with particle creation if energy conservation applies at every scale. This process is shown to provide a gravitational repulsive force which can counterbalance gravitational attraction thus allowing the possibility of a steady non-inflationary expansion. That seems to provide an alternative coherent scheme for our picture of the Universe evolution, disposing of the cosmological term, of dark energy and of the bulk of dark matter.

An analysis on a rigid-flexible coupling system of an oscillating massand a rotating disk

A mass-rod-disk system consisting of an oscillating mass attached to a rigid rotating disk by an elastic rod is designed to study rigid-flexible coupling mechanism.Suppose the rod is lightweight and has enough stiffness,the theorems of linear momentum and angular momentum are applied to the mass-rod-disk system based on the kinematic description of the system.With respect to two deflections of the mass and one angular velocity of the system,a group of nonlinear differential equations are established where the tangential inertial force,centrifugal force,Coriolis force as well as the moments of additional inertial forces take important effects on the dynamic response.For the sake of description,these three types of inertial forces mentioned before are referred to as additional inertial forces in this paper.The horizontal deflections of the mass and the angular velocity of the disk rotating about a fixed-axis are numerically solved for the prescribed external torque.The oscillating trajectory of the mass is deeply influenced by the additional inertial forces,meanwhile the dynamic fluctuations of the angular velocity and rotary inertia of the system are strongly affected by the mass oscillation.

Research of novel oscillating wire feeding system using the AC servo motor

With the background of the control of additional mechanical force droplet transfer in MIG/MAG welding, regarding the AC servo motor as core, a novel oscillating wire feeding system has been developed with excellent performances of control and dynamic acceleration which is tested. System constitution and operation principle are introduced in this paper. Influences of parameters on dynamic acceleration performance are analyzed and discussed emphatically, such as oscillating frequency, oscillating amplitude and draw-back speed. Experimental result indicates that according to the technique of welding control, the novel wire feeding system responds rapidly to various kinds of control orders of wire feeding and draw-back, and realizes flexible control of welding wire axial movement, including dynamic shifting,oscillating and so on.

Vacuum Fluctuations, Isolated Systems and Hierarchical Cosmology

Einstein's general theory of relativity rests on the convention of constant units for time and length, specified by standards at a fired world point P. It is valid to flatten space-time by choice of unit fields, obtained by applying time dilation and length contraction to standards in accordance with an aether velocity field vg(r,t). Two equally valid descriptions for gravitation result. Cosmology in flat space-time is first developed. Zero-point radiation is renormalized to finite energy Kpoc2 density by inclusion of gravitational self-potential energy density provided that Kpoc2 closes the uni- verse at radius R. It is shown that such a universe satisfies the black hole condition, and hence behaves as an isolated system. A single constant defines a finite universe with respect to any mass, due to self-adjustment of boundary surface. The equivalent Einstein model is found by a units transformation to be de Sitter space-time. Einstein's equations must contain only the cosmological term as source term. The Hubble redshift is shown to emerge in both Doppler-gravitational and frequency-decay guises. By postulating an infinite Cosmos containing universes on a hierarchy of scales specified by a geometric series of constants, it is possible for gravitation and electromagnetism to acquire equal complementary status. Unified field equations are proposed, and the relationship between an electron and a universe is explored. A theoretical value of the Hubble constant emerges, H= 108 km s-1Mpc-1.

Design and identification of a double-acting piezoelectric-hydraulic hybrid actuator

Traditional single-acting piezoelectric-hydraulic hybrid actuators usually have the problem of inertial force caused by flow pulsation of the liquid,which degrades their output performance.To suppress or solve the associated inertial force and enhance its output capabilities,this paper proposes a new type of double-acting piezoelectric-hydraulic hybrid actuator with four check valves acting as mechanical diodes.The new hybrid actuator was fabricated and its output performance was tested.When the voltage is 700 Vp-pand the bias pressure is 2 MPa,the pulsation ratesδof the new actuator at 400 Hz,500 Hz and 600 Hz are 2.29,2.08 and 1.78,respectively,whileδof the single-acting hybrid actuator under the same conditions are 10.98,11.05 and 17.12.Therefore,the liquid pulsation rate of the new hybrid actuator is significantly reduced,which is beneficial for improving the flow uniformity and weakening the influence of inertial force on the hybrid actuator.This strategy ultimately leads to a maximum no-load velocity of 168.1 mm/s at 600 Hz and a maximum blocking force of 141 N at 450 Hz for the new hybrid actuator.In addition,this strategy has the potential to be used in other electrohydrostatic actuators to improve their performance.

LABORATORY STUDIES ON WAVE FORCE OF COASTAL STRUCTURES MADE OF FLAT GEOTUBES

Flat geotubes are widely used for coastal structures such as seawalls, breakwaters and sightseeing groins, etc.. However, the understanding of the stable mechanism involved in the wave-structure interactions should be deepened, and one of the important work is to clarify the stress state of the structure under the wave action. In this article, wave force acting on coastal structures made of flat geotube is experimentally investigated. The required drag, inertia and lift coefficients are especially analyzed from the results of hydraulic model experiments specially designed for geotube structure. Several types of structures made of flat geotubes under wave action have been tested in order to understand the stress state of the geotube fixed to force transducer within different structures. Experimental results show that the wave-induced forces on the instrumented geotube are markedly influenced by wave elements. Meanwhile, the magnitude of horizontal force of adjoining geotube is different at the same time.

Viscoelastic microfluidics: progress and challenges

The manipulation of cells and particles suspended in viscoelastic fluids in microchannels has drawn increasing attention,in part due to the ability for single-stream three-dimensional focusing in simple channel geometries.Improvement in the understanding of non-Newtonian effects on particle dynamics has led to expanding exploration of focusing and sorting particles and cells using viscoelastic microfluidics.Multiple factors,such as the driving forces arising from fluid elasticity and inertia,the effect of fluid rheology,the physical properties of particles and cells,and channel geometry,actively interact and compete together to govern the intricate migration behavior of particles and cells in microchannels.Here,we review the viscoelastic fluid physics and the hydrodynamic forces in such flows and identify three pairs of competing forces/effects that collectively govern viscoelastic migration.We discuss migration dynamics,focusing positions,numerical simulations,and recent progress in viscoelastic microfluidic applications as well as the remaining challenges.Finally,we hope that an improved understanding of viscoelastic flows in microfluidics can lead to increased sophistication of microfluidic platforms in clinical diagnostics and biomedical research.