Influence Of Inertia Forces Research Articles

Experimental analysis on the flow patterns and conversion mechanisms of condensing flow with non-azeotropic mixtures in spiral tube

The flow patterns have a significant impact on the flow and heat transfer characteristics of the working fluid, making it fundamental for the study of complex two-phase flows. To investigate the condensation flow pattern and flow pattern transformation mechanism with mixed hydrocarbon in a spiral tube, a two-phase flow pattern experimental system was designed. The effects of mass flux (196–540 kg/m−2·s−1), vapor quality (0–1), and operating pressure (2–4 MPa) on flow patterns of methane/ethane/propane/isobutane mixed fluid in spiral tubes were analyzed. The results showed that with the increase in vapor quality, flow patterns such as bubbly flow, intermittent flow, wavy-stratified flow, and annular flow were observed in sequence. Additionally, through a comparative analysis of the experimental observations with existing flow pattern maps, a new flow pattern map tailored for the condensation two-phase flow of mixed hydrocarbon working fluids has been established. Based on the influence of inertial force, surface tension, gravity, shear force and other forces, Martinelli number, Soliman We and Soliman Fr are selected for the development of flow pattern conversion criteria. The new flow pattern map accurately predicts the majority of flow patterns.

Dielectrophoretic–inertial microfluidics for Symbiodinium separation and enrichment

In the marine environment, the symbiotic relationship between Symbiodinium and corals plays a pivotal role in coral growth and development. Against the backdrop of widespread coral bleaching due to the global climate change, the facile and efficient separation and enrichment of different strains of Symbiodinium hold significant importance for studying coral bleaching. This paper aims to report a platform that integrates dielectrophoretic and inertial forces for the separation and enrichment of Symbiodinium, comprising two modular components: a separation module and an enrichment module. Within the separation module, distinct strains of Symbiodinium undergo preliminary stratification in a contraction–expansion microchannel under the influence of inertial forces. Dielectrophoretic forces generated by the indium tin oxide electrodes divert them toward different outlets, achieving separation. In the enrichment module, the Symbiodinium collected from outlets is rapidly focused through a contraction–expansion microchannel and high-purity samples are concentrated through a single outlet. Evaluating separation efficiency is based on the purity of collected Symbiodinium at the outlet under three different flow rates: 13, 16, and 19 μl/min, while the concentration of enriched Symbiodinium at 100, 200, 300, and 400 μl/min flow rates evaluates the effectiveness of the enrichment process. The experimental results demonstrate a separation purity of approximately 90% and an enrichment factor of around 5.5. The platform holds promise for further applications in the selection and targeted enrichment of high-quality coral symbiotic algae, providing essential research foundations for the conservation of coral ecosystems.

Dynamic digging force modeling and comparative analysis of backhoe hydraulic excavators

The evaluation of excavator performance relies heavily on digging force, which serves as a crucial indicator. However, the accuracy of performance assessment is hindered by the absence of a suitable method to characterize the dynamic digging capacity of excavators. This study addresses this limitation by proposing an approach to establish a set of solution-limited inequalities for dynamic digging force. The approach incorporates D’Alembert’s principle and composite digging, while considering the influence of inertia force. Furthermore, to mitigate the issue of bucket tooth tip trajectory shaking caused by discontinuous posture during excavation, an amount of measurement data from a 20-ton machine is utilized to construct a consistent theoretical digging trajectory. The theoretical trajectory is subjected to numerical verification to determine the dynamic digging force along the trajectory. A comparative analysis is then conducted, contrasting the obtained dynamic digging force with different theoretical digging forces and measured resistances. Additionally, the dynamic digging forces within the selected digging area of the machine are characterized, without accounting for attitude continuity. The findings demonstrate that the dynamic digging force effectively captures the excavator’s performance along the trajectory, and it also provides an excellent characterization of the digging force at discrete digging spots.

Design and development of a piezoelectric-hydraulic hybrid actuator with quarter-wavelength tubes

The piezoelectric hydraulic actuator is a hybrid device consisting of a hydraulic pump driven by a piezoelectric stack connected to a hydraulic cylinder. For this type of piezoelectric actuator, the inertial force caused by the flow pulsation of the liquid will inhibit the movement of the piezoelectric vibrator and reduce its output performance. To solve these issues, two tubes were embedded into the piezoelectric-hydraulic hybrid actuation system for the first time to act as mechanical bandstop filters by interfering with the propagation of acoustic waves. The acoustic power transmission loss of the tube is derived from the one-dimensional wave equation. According to the experimental results, when the excitation frequency is close to the optimal operating frequency corresponding to the tubes, the liquid pulsation rate is reduced, the influence of inertial force on the actuator is weakened, and the output performance is relatively significantly improved. This strategy finally leads to a maximum no-load velocity of 153.5 mm s−1 and a maximum blocking force of 261.5 N for the hybrid actuator with 300 mm tubes; the maximum no-load velocity and blocking force of the hybrid actuator with 500 mm tubes are 94.45 mm s−1 and 230 N, respectively. Furthermore, this strategy can be used in other electrohydraulic actuators to enhance their capabilities.

Analysis of Nonlinear Time-Domain Lubrication Characteristics of the Hydrodynamic Journal Bearing System

The nonlinear time-domain lubrication characteristics of the hydrodynamic journal bearing system are studied in this paper. The motion equation of the hydrodynamic journal bearing system is established based on the balance of the relationship among the water film force, journal inertia force, and external load. The water film pressure distribution of the sliding bearing is calculated by the finite difference method. Firstly, the variation law of the water film pressure distribution with time under the external periodic load is calculated considering the inertial force of the journal. The influence of the initial eccentricity on the orbit of the journal center is studied. Secondly, the maximum water film pressure, the orbit of the journal center, eccentricity, water film pressure, and the minimum water film thickness of the bearing under the action of circumferential and unidirectional periodic external loads are calculated, and the effects of inertial force and rotational speed on the dynamic characteristics of the bearing are analyzed. Finally, the water film dynamic characteristics under low speed and heavy load are studied. The result shows that the pressure of the dimensionless water film caused by inertial force is reduced by 7 to 10 percent at the rotational speed between 200 r/min and 800 r/min, which means that the influence of inertia force cannot be ignored.

Numerical investigation on the influence of contact characteristics on nonlinear flow in 3D fracture

The objective of this paper is to investigate the effects of contact rate on fluid flow through rock fractures. Different contact rate fracture models are constituted by changing the relative position of the upper and lower fracture surfaces, which is realized with the three-dimensional scanning technology. The results indicate that the generation of contact area and the increase of contact rate will enhance the nonlinearity of fracture fluid flow, and the influence of inertial force in fluid will be more obvious, under which the regime of fracture fluid flow will turn from linear to nonlinear earlier. The entire pressure field and velocity field in fracture are obviously affected by the contact rate. An obvious pressure dividing line appears near the contact area, and the pressure gradient and velocity increase significantly across the dividing lines. The phenomenon of groove flow exists between the contact areas, and eddy is generated on the back flow area of the contact area. The eddy area increases with the Re, the effective flow aperture is further compressed, and the local velocity increases. In the three-dimensional view, it is discovered that the streamline in the double eddy system is distributed in an “8″ shape, and there is flow exchanges between the two eddies.

Features of the calculation of air leaks through the mined-out space of coal mines

The movement of air leaks through the goaf of coal mines can lead to gas contamination of workings with the formation of local and layer accumulations of methane. This increases the likelihood of explosive situations. Therefore, an important factor is the ventilation scheme used in the excavation area. The process of gas flow through a goaf is an understudied issue. This is due to the difficulty of conducting direct measurements inside the object under study. In many works, when studying the movement of air leaks through the mined-out space, the linear Darcy filtration law is used. However, the influence of inertia forces can lead to additional gas pressure losses and, accordingly, to deviations from the classical law. Therefore, it is advisable to use the law of two-term filtration. The purpose of the work is to study the patterns of movement of air leaks through the mined-out space, taking into account its filtration parameters and the current ventilation scheme. The article presents the results of calculating the speeds of air leaks and the trajectories of streamlines in the mined-out space with direct-flow and return ventilation schemes. The Darcy formula and the Forchheimer formula were used in the calculations. It has been established that with a two-term filtration law, the values of the result-ing air leakage rates are less than with a linear law. This is due to pressure losses as a result of inertial forces. It has been established that with a direct-flow ventilation scheme, the rates of air leakage in the longwall increase exponentially along the goaf boundary in the direction of the ventilation flow and quadratic ally increase deep into the goaf to a certain maximum located at a distance of about half the length of the longwall. At the same time, in the case of the return-flow ventilation scheme, the rates of air leaks in the longwall have maxima at the boundary of the goaf and decrease linearly towards the center of the longwall, and in the goaf at a distance of up to three meters from the longwall, their quadratic decrease occurs. The results obtained make it possible to reduce the gas contamination of workings by choosing rational schemes and ventilation modes.

Dynamic Modeling and Experimental Validation of a Water Hydraulic Soft Manipulator Based on an Improved Newton-Euler Iterative Method.

Compared with rigid robots, soft robots have better adaptability to the environment because of their pliability. However, due to the lower structural stiffness of the soft manipulator, the posture of the manipulator is usually decided by the weight and the external load under operating conditions. Therefore, it is necessary to conduct dynamics modeling and movement analysis of the soft manipulator. In this paper, a fabric reinforced soft manipulator driven by a water hydraulic system is firstly proposed, and the dynamics of both the soft manipulator and hydraulic system are considered. Specifically, a dynamic model of the soft manipulator is established based on an improved Newton–Euler iterative method, which comprehensively considers the influence of inertial force, elastic force, damping force, as well as combined bending and torsion moments. The dynamics of the water hydraulic system consider the effects of cylinder inertia, friction, and water response. Finally, the accuracy of the proposed dynamic model is verified by comparing the simulation results with the experimental data about the steady and dynamic characteristics of the soft manipulator under various conditions. The results show that the maximum sectional error is about 0.0245 m and that the maximum cumulative error is 0.042 m, which validate the effectiveness of the proposed model.

A model formulation for the prediction of churning power loss in worm gear transmission

Churning power loss is a complex process that causes significant loss of energy under splash lubrication of gear units. A set of empirical equations are available that allows for precise churning power losses calculation for only the parallel axis gears. The main objective of this study is to formulate a new mathematical model for worm gear based on the experiment result. The mathematical model is formulated using the dimensional analysis method and has been experimentally validated over a wide range of speeds in terms of revolutions, types of lubricants, lubricant temperature, and immersion depths. The simple direct torque measurement method was used to measure the churning loss. The influence of inertia force, viscous force, and gravitational forces were also investigated therefore correlations with Froude and Reynolds numbers are presented. Hardened steel and bronze were used as a material combination of worm and worm gear, respectively. A new formula for worm gear under splash lubrication has been derived and validated by comparison with experimental evidence. A very little discrepancy was found between the experiment result and the mathematical equation.

The Use of the k-ω SST Turbulence Model for Mathematical Modeling of Jet Fire

Aim: The purpose of this study is to verify the usability of the k-ω SST turbulence model for the description of the combustion process during a vertical propane jet fire. Simulating a jet fire using computational fluid mechanics involves an appropriate selection of a mathematical model to describe the turbulent flow. It is important as the variables from this model also describe the rate of the combustion reaction. As a result, they have an impact on the size and shape of the flame. The selection of an appropriate model should be preceded by preliminary simulations. Project and methods: For this purpose, a vertical jet fire in no wind conditions was selected for simulation. Consequently, it was possible to develop a two-dimensional axisymmetric geometry. A good numerical mesh can be applied to such axisymmetric geometry. Selected process conditions allowed to create an axisymmetric numerical grid. Its values, proving the quality, are shown in a chart demonstrating the distribution of the parameter quality depending on the number of elements from which the numerical grid was built. In the work, a two-stage model of the combustion reaction was selected in order to verify whether the area in which the mole fraction of carbon monoxide will have significant values is so large that the selected kinetic reaction model will have an impact on the flame length. Results: Three simulations of jet fire taking place in the direction opposite to the force of gravity were performed. The simulations performed allowed for setting the basic L f parameter, which determines the flame length. Additionally, the length of the mixing path slift-off, needed to initiate the combustion reaction, was determined. The simulations performed allowed for comparing significant parameters characterizing the flame with the parameters calcu- lated using correlations included in the literature on the subject. Due to this comparison, it was possible to define an interesting scope of research work, because the length of the gas mixing path determined from the CFD simulation differed significantly from the values calculated from the correlation. Conclusions: Interestingly, such large differences between CFD results and correlations were not observed for the L f parameter. The correlations based on the Froude number give slightly higher values of the flame length than the results of the CFD simulation. On the other hand, the correlation based on the Reynolds number gives slightly lower values of the L f parameter than the values obtained from the CFD calculations. This may indicate that the effects related to the inertia forces (Re number) better describe the simulation process conditions than the correlations based on the influence of inertia forces and gravity forces (Fr number). Keywords: jet fire, mathematical modelling, computational fluid dynamics Type of article: short scientific report

Improving two-phase mass transportation under Non-Darcy flow effect in orientated-type flow channels of proton exchange membrane fuel cells

Orientated-type flow channels of proton exchange membrane fuel cells cause non-Darcy effect occurring in flow regions. Therefore, the species transportation is affected by inertial effect. However, how the inertial force affects convection and diffusion of different species has not been discussed before. Thus, a modified two-dimensional, non-isothermal, two-phase and steady state model considering non-Darcy effect is employed in this study, and reactants and products transportations through diffusion and convection under inertial effects are quantitatively analyzed for the first time. Simulation results reveal that the convective transportation of reactants increases more under the influence of inertial force; water vapor transportation through convection increases the water content in porous regions. At the same time, liquid water expels more rapidly from gas diffusion layers under baffle regions, and enlarging baffle volumes increases the regions where the liquid water is rapidly removed under the inertial effect.

Investigation of the Influence of Inertia Forces on the Adhesion of the Coating to the Outer Surface of Bodies of Revolution during Thermal Spraying

The article presents the results of a study of the influence of inertial forces on the adhesion of the coating to the external surface of a body of revolution during thermal spraying. A mathematical apparatus is proposed for calculating the inertia forces, acting on a particle of coating, applied to the outer surface of the bodies of revolution. As a result, dependencies have been revealed that allow predicting the adhesion strength of the coating with the steel base during thermal spraying.

Inertial property of oscillatory flow for pulse injection in porous media

The low-frequency pulse wave makes the velocity of the fluid in the reservoir fluctuate dramatically, which results in a remarkable inertia force. The Darcy’s law was inapplicable to the pulse flow with strong effect of inertial force. In this paper, the non-Darcy flow equation and the calculation method of capillary number of pressure pulse displacement are established. The pressure pulse experiments of single-phase and two- phase flow are carried out. The results show that the periodic change of velocity can decrease the seepage resistance and enhance apparent permeability by generating the inertial force. The higher the pulse frequency improves the apparent permeability by enhancing influence of inertial force. The increase of apparent permeability of high permeability core is larger than that of low permeability core, which indicates that inertial force is more prominent in high permeability reservoir. For the water-oil two-phase flow, inertia force makes the relative permeability curve move towards right, and the equal permeability point becomes higher. In other words, with the increase of capillary number, part of residual oil is activated, and the displacement efficiency is improved.

Numerical Modeling of the Spread of Cough Saliva Droplets in a Calm Confined Space

The coronavirus disease 2019 (COVID-19) outbreak has altered the lives of everyone on a global scale due to its high transmission rate. In the current work, the droplet dispersion and evaporation originated by a cough at different velocities is studied. A multiphase computational fluid dynamic model based on fully coupled Eulerian–Lagrangian techniques was used. The evaporation, breakup, mass transfer, phase change, and turbulent dispersion forces of droplets were taken into account. A computational domain imitating an elevator that with two individuals inside was modeled. The results showed that all droplets smaller than 150 μm evaporate before 10 s at different heights. Smaller droplets of <30 µm evaporate quickly, and their trajectories are governed by Brownian movements. Instead, the trajectories of medium-sized droplets (30–80 µm) are under the influence of inertial forces, while bigger droplets move according to inertial and gravitational forces. Smaller droplets are located in the top positions, while larger (i.e., heaviest) droplets are located at the bottom.

Basic Research on the Influence of Inertial Force in Force Presentation System, Position Input System and Rehabilitation Support System

Basic Research on the Influence of Inertial Force in Force Presentation System, Position Input System and Rehabilitation Support System

THE GRINDING MECHANISM ON A KNIFE CENTRIFUGAL GRINDING MACHINE

The article presents a methodology for calculating the force effect on a fibrous suspension of working bodies in a centrifugal grinding apparatus. The aim of the research is to calculate the force per tooth of an inertial body at different speeds of rotation of the rotor, to determine the effect of the circumferential speed of movement of inertial bodies on the grinding process of fibrous semi-finished products. The article discusses the mechanism of grinding on a centrifugal knife grinding apparatus, determines the tangential shear forces at the contact of the grinding satellite knives with the grinding bowl knives, determines the effect on the fiber of rolling friction forces and sliding friction forces when the grinding satellite knives come into contact with the grinding bowl knives, as well as the effect of specific pressure at the point of contact of the satellite knives with the grinding bowl knives under the influence of inertial forces. Based on the research results, it is scientifically substantiated that the forces arising at the minimum of the considered values of the rotation speed of inertial bodies are sufficient to break the fiber when using this installation for grinding fibrous semi-finished products. An increase in the speed of rotation of the satellites causes a positive change in the physical and mechanical characteristics of the finished castings.

Analysis and Simulation of the Impact of Inertial Force on the Impact Point of Missile Weapons

In order to explore the impact of inertial force on missile impact point, the law of the missile impact point error with missile range, aiming azimuth and launch point latitude under the influence of inertial force is analyzed. In this paper, based on the basic principles of missile ballistics and theoretical mechanics, the trajectory and the distribution of impact point under the influence of inertial force are simulated and analyzed. The results show that the impact point error affected by inertial force is positive correlation to the range of missile when the aiming azimuth is fixed. In the case of a certain range, with the change of the aiming azimuth, the impact point error will also change according to a certain rule. When the range and aiming azimuth are fixed, the impact point error decreases with the increase of latitude.

HYDRODYNAMICS OF GAS-LIQUID FLOW IN THE TUBING OF ROD PUMP INSTALLATIONS

During the operation of rod installations, pressure oscillations occur in the pump and compressor pipes due to the influence of hydrodynamic friction and inertia forces under conditions of uneven supply of the plunger pump during the pumping cycle. Pressure oscillations have a negative impact on the operation of pumping units: they lead to an increase in loads on pumping equipment components, the rate of fatigue wear of pumping rods, etc. Promising direction for improving the efficiency of rod installations is the development of methods and technologies for reducing pressure oscillations in pumping pipes. To smooth out pressure oscillations, pneumatic compensators are used. Pneumatic compensators are designed to equalize the speed of the liquid in the pipes. A mathematical model of the unsteady flow of gas-liquid flow in the pumping pipes of rod installations has been developed. By modeling the pumping of products with different rheological properties (differing in water content, viscosity, and compressibility), the features of pressure dynamics in the lower end of the tubing and in the flushing line at the wellhead are analyzed to assess the potential efficiency of placing wellhead (located in the flushing line at the mouth) and deep (located in the lower part of the tubing) pneumatic compensators. By modeling the pumping of high-viscosity oil it is shown that the maximum pressure at the wellhead and the lower end of the tubing is achieved in different half-cycles of the plunger (at the mouth of the upstroke, at the lower end of the tubing - at moving down) that is associated with the influence of relative movement of the rods and fluid on the formation pressure in the tubing. As a result, when pumping out high viscosity products, the wellhead pneumatic compensator reduces the component of the maximum load on the balancer head due to the hydrodynamic friction of the liquid when it moves in the collector, while the deep one reduces the load of hydrodynamic friction acting on the rod column and ensures free movement of the rods downwards. It is shown that when pumping low-viscosity oil with a high gas content, the amplitude of pressure oscillations is small and in the considered examples does not exceed 0.02 MPa. The influence of inertia forces that are crucial for pumping high-water oil is analyzed. Calculations show that the amplitude of pressure oscillations at the mouth is about 70 % of the amplitude of oscillations at the lower end of the tubing, which allows using wellhead pneumatic compensators to reduce the component of pressure pulsations in the tubing caused by the forces of inertia when the fluid moves in the reservoir.

Stepwise analysis of pantographic beams subjected to impulsive loads

Materials based on pantographic unit cells have very interesting mechanical peculiarities. For these reasons they are largely studied from a theoretical, experimental, and numerical point of view. Numerical simulations furnish an important contribution for the the design and optimization of such materials and, more generally, for metamaterials. Here, we consider the influence of inertial forces, removing the hypothesis of quasistatic loading. By using an intrinsically discrete model, inspired by Hencky’s ideas, already tested in a series of published works, here we add the contribution of inertial forces and, in the framework of stepwise schemes, we re-experience an adaptive integration scheme capable of reconstructing the best structural response corresponding to a prefixed time step. Several numerical simulations, although preparatory, inspire some remarks on materials based on pantographic cells and outline the way for future challenges.

Multi-Well Pumping System Design and Field Application

Abstract In view of the low efficiency of cluster wells, a multi-well pumping system with phase-division balance is put forward based on the idea of overlapping load-dislocation vectors. In this article, the kinematics and dynamics of the system are analyzed and the torque fluctuation characteristics of the system and the changing law of the motor energy consumption are studied under theory and actual working conditions. Additionally, a comparative analysis of a computer simulation and field test is carried out from the single-well to four-well pumping system. The results show that the dynamic performance of the multi-well pumping system based on phase-division balance is obviously better than that of single-well pumping unit. In addition, the system has remarkable high-efficiency energy-saving characteristics and good dynamic characteristics with coefficient of load fluctuation approaching 1 and a markedly reduced root mean square torque. The influence of inertia force on driving moment is considered by establishing the dynamic equation of the main mechanism and doing dynamic simulation. The friction power is equivalent to the corresponding additional driving power, so the influence of friction on driving moment is considered. The computer simulation results also show that the effect of multi-wells is good. According to field test data, a four-well pumping system can save 361 kWh of electricity per day.