Effects Of Inertia Forces Research Articles

Design and testing of an innovative electro-dynamic filter for gas turbine intake systems

Abstract Gas turbines require filtered air to preserve the efficiency and the life of the system. Different degradation processes can occur depending on the size and composition of the contaminants. The compressor’s performance can be negatively impacted by fouling and erosion, which alter the shape and roughness of the blades. To limit the effects of the aforementioned phenomena, multistage filtration systems are commonly installed to reduce the contamination at the gas turbine inlet. Traditionally, particle separation is performed through mechanical filtration, which means that the particles are trapped inside cartridges of porous materials. This typology of filter guarantees a high filtration efficiency but on the other hand, generates remarkable pressure drop increasing over time. Inertial filters instead separate contaminants from the flow by utilizing the effect of inertial force acting on solid particles. In recent years, electrostatic filters have become widespread. The fibers of the filters are charged with an electrostatic field before installation and this charge is capable of separating and attracting metallic particles from the airflow. However, the electrostatic field’s effect diminishes with the exposure time with this type of filter. This work presents an innovative electro-dynamic filtration system for gas turbine application. The geometry and electrical features of the devices are designed to keep low-pressure drop and high capturing efficiency over time. To achieve these goals, a numerical campaign is performed using an in-house OpenFOAM solver, which takes into account the effect of the electrostatic force of the Lagrangian phase. After the definition of the optimal geometry, experimental tests are performed to validate the numerical results. Finally, a comprehensive laboratory-scale campaign is carried out to evaluate filtration efficiency under various environmental conditions, including different types of contaminants, concentrations, and exposure times.

Prestressed concrete slabs subjected to low-velocity impact: Theoretical analysis model and design method

Bidirectional bonded prestressed concrete (PS) structures are widely used in energy engineering structures due to their excellent impermeability. Owing to the particularity of the structure and the severity of damage consequences, the impact dynamic performance of bidirectional bonded PS structures has been widely concerned. Nonetheless, the existing researches focus on the test and finite element, and lacks the theoretical analysis model that can consider the whole process of load action, let alone the corresponding anti-impact design method. Therefore, based on the existing test and finite element results, the resistance function model of bidirectional bonded PS slab is proposed in this paper, and the anti-impact design method is formed. Firstly, the performance of specimens under low-velocity impact loading and quasi-static loading conditions is compared, and the effects of inertia force and material strain rate on the dynamic performance of specimens under low-velocity impact are further explored. Then, a resistance function theoretical analysis model that can consider the whole process of load action is proposed with a quadrilinear form, and the analytical expressions of resistance and stiffness at characteristic points are derived. Subsequently, the accuracy of the resistance function model is verified based on the existing test results. Furthermore, based on the resistance function model, the influence laws of compressive strength of concrete, prestressing degree, reinforcement ratio of reinforcement and slab thickness on slab resistance are analyzed. Finally, an anti-impact design method considering perforation and scabbing failure is proposed, and the feasibility of the design method is verified by impact test results.

Reduction of Input Torque and Joint Reactions in High-Speed Mechanical Systems with Reciprocating Motion

In high-speed machinery, the variable inertia forces generated by reciprocating masses often introduce undesirable effects, such as a significant increase in the required input torque and joint forces. This paper addresses the challenge of reducing input torque and joint reaction forces in such mechanisms by employing two compression linear springs positioned between the slider and the frame. These springs counterbalance the slider's inertia force, thereby diminishing both the input torque and joint reactions. It is important to note that the elastic forces exerted by these springs remain internal to the mechanical system, preserving the balance of shaking forces and moments of the mechanism on the frame. The analytical framework developed in this study focuses on minimizing the root mean square and maximum values of the inertia force effects. A significant scientific achievement is attaining a given goal through an analytical solution. Notably, this is the first instance where this problem has been formulated and solved using explicit expressions. The effectiveness of the proposed technique is also demonstrated through CAD simulations, showing a substantial reduction in input torque and joint reactions.

Designing MEMS accelerometer for enhanced sensitivity and reduced cross-sensitivity in landslide monitoring

MEMS accelerometers capable of detecting weak motions are required in measuring landslide movements. The sensor’s sensitivity and its independent readings of various acceleration modes are crucial factors in the design of these sensors. In addition, it is highly desired to fabricate these sensors with low-cost and flexible manufacturing technologies such as surface micromachining. This paper presents an advanced topology optimization approach to design the suspended structure for the maximum level of sensitivity and for a low cross-sensitivity in the reading of principal and lateral modes, while it is manufacturable with a low-cost surface micromachining process. The effect of inertial forces as a variable loading condition and mode switch prevention is applied using a meta-heuristic topology optimization method with simulated annealing. Considering the unique results of this topology optimization, PolyMUMPs surface micromachining is employed to manufacture the developed sensor. The fabricated sensor is subjected to measurement and subsequent comparison with analogous designs from the literature. The outcomes reveal a sensitivity of 0.3pF/g and cross-axis sensitivity of 0.048%, signifying a noteworthy advancement for surface micromachined accelerometers. Notably, this design, coupled with the devised topology optimization methodology, holds the potential for adoption by sensor manufacturers for diverse commercial applications.

VIBRATION ANALYSIS OF HEAVY WEAPONS IN TRANSIT BY AIRCRAFT IN FRACTAL SPACE CONSIDERING LOCATION DEVIATION

Air transportation constitutes a significant advancement in enhancing transportation efficiency. Nonetheless, when this modality is employed for the transit of large-scale armaments and equipment, the vibrational properties of these items within the aircraft’s cabin, coupled with potential deviations from their designated installation positions, emerge as critical factors that could compromise the safety of such transportation endeavors. To accommodate the unique environmental conditions of low-temperature and low-pressure prevalent in high-altitude air transportation, this model employs a fractal frequency formula for an expedited and accurate characterization of vibrational properties, while also providing a detailed analysis of the errors attributable to positional deviations in these vibration assessments. The findings of this research demonstrate that the computational accuracy achieved herein surpasses that of the variational iteration method (VIM) and the homotopy perturbation method (HPM). Moreover, the investigation into the damping effects of inertial forces within fractal dimensions unveils innovative prospects for optimizing nonlinear vibration systems under the challenging conditions of low-temperature and low-pressure environments.

RESEARCH OF THE CHANGE IN THE CONSOLIDATED MASS IN FLAT MULTI-LINK MECHANISMS

Purpose. Determination of the equation of motion of the crank-connecting mechanism using the methods of researching the motion of flat multi-link mechanisms. Development of the dependence using the theorem on the change in kinetic energy of the mechanical system for determining the total mass of flat mechanisms when the angle of rotation of the driving link of the flat mechanism changes.
 Research methods. Dynamic analysis of the mechanism. The method of reducing forces and masses. Mathematical determination of the kinetic energy depending on the angle of rotation of the crank of a flat mechanism. Regression processing of the obtained calculation results and their subsequent correlation analysis were carried out using computer software for the analysis and visualisation of scientific and statistical data – «SigmaPlot» from the company «Jandel Corporation».
 Results. A calculated formula for the change in the combined mass depending on the angle of rotation of the crank was obtained. The existence of a sinusoidal relationship between the calculated parameters (crank angle and reduced mass) was established. The correlation analysis of the obtained function showed a sufficiently high degree of relationship between the calculated data and the mathematical dependence, while the correlation coefficient was r = 0.972. The graph of the determined mathematical dependence also showed a fairly high correlation between the specified parameters. The resulting equation can be used for systems with one degree of freedom. For mechanisms with several degrees of freedom, the law of change of the combined mass will be different for each degree of freedom.
 Scientific novelty. Using the calculated formulas of kinetic energy for planar mechanisms, the law of change of the reduced mass in planar mechanisms, which takes into account the rotation of the crank around its own axis, is obtained.
 Practical value. When designing flat crank mechanisms, it is necessary to take into account the effect of inertial forces, the value of which depends on the mass and acceleration. This makes it possible to calculate correctly the dynamic loads on the parts of the flat mechanism (bearings, etc.). The obtained mathematical dependence of the change in the combined mass on the angle of rotation of the leading link of the mechanism makes it possible to analyse the change in the combined moment of inertia, which in turn affects the change in torque.

Effect of inertia force on the interface stability of a tangential-velocity discontinuity in porous media

Effect of inertia force on the interface stability of a tangential-velocity discontinuity in porous media

Jaffrey-Hamel flow features of Oldroyd-B model through intersecting plates

We evaluate the steady Jaffrey-Hamel flow of a viscoelasticfluid using Oldroyd-B modelin a deformablechannel formed by two intersectingplates. To be more precise, we offer a mathematical structure for computing the leading-order impacts of the fluid viscoelasticity on the flow in the setting of relaxation and temporal retardation interactions between the fixed walls of the channel. The typicaldimensionless variables influencing the interaction of fluid and structure in both wider (divergent) and narrower (convergent) channels are primarily identified. The flow originates from a source located at the apex, travel from convergent to divergent zone, and exist at the outlet to the reservoir. Only radial component of velocity contributes to the fluid velocity while the azimuthal component is zero. The fluid attributes are independent of hydraulic pressure and temperature. We highlight the respective contributions of various components of momentum equation coupled with pressure gradient along the radial and tangential direction. The pressure gradientis omitted, since gradients of viscoelastic shear stresses predominantly cause the contribution for narrower/expanding geometries. We further demonstrate that, although the pressure is minimal along the midline line for narrow geometries, viscoelasticstresses are equal to or greater than shear stresses across the domain. Applying the principle of momentum and mass conservations in a cylindrical polar framework,thesystem of governingequations are constructed. Thecomputer basedMATLABcode (bvp4c tool) is used to numerically solve the consequent set of modelled equations. The results pertaining to a Navier-Stokes fluid, and aMaxwell fluid exist as limiting instances of our formulations. Effect of inertial forces 20≤Re≤140 and channel opening have similar effects on converging and diverging section of the channel. A higher strain delaying time and a shorter stress relaxation phase produce an improved velocity profile, but both viscoelastic times have the opposite effect.

Dynamic response and liquefaction potential of porous seabed induced by partial standing ocean waves

The analysis of ocean wave-induced dynamic response of a porous seabed is particularly important for coastal and geotechnical engineers when designing and constructing maritime structures. In this study, an analytical solution is presented to analyze the dynamic response and liquefaction potential of a poro-elastic seabed induced by partial standing waves with arbitrary reflectivity. The porous seabed is modeled using Biot’s theory describing the propagation of elastic waves, and coupled deformation and water flow of porous media, whereas the ocean waves are described using linear ocean wave theory. Based on the mixed boundary-value conditions, explicit expressions of displacements, effective stresses and excess pore water pressure of seabed are derived with consideration of the effects of inertial forces, compressibility of solid and fluid, and arbitrary reflectivity of standing waves. The results of degenerated analytical solutions are compared with the existing ones to verify the correctness of the proposed method. The effects of several pertinent parameters of ocean wave-seabed system, including reflection coefficient, phase lag and period of standing waves, depth of water, permeability, degree of saturation, and shear modulus of seabed deposits, etc., on the dynamic response of seabed and liquefaction potential, are examined and discussed. It is found that the reflection of standing wave has a significant effect on the dynamic response and liquefaction potential of porous elastic seabed. Compared with that of no wave reflection, the liquefaction depth of seabed induced by fully-reflected standing waves increases 82.49% under certain conditions of wave-seabed system. In addition, phase lag, wave period, water depth and mechanical and physical properties of seabed soil such as saturation, permeability and shear modulus have different effects on the dynamic response and liquefaction potential of porous elastic seabed. The investigation of the dynamic response and liquefaction of the porous elastic seabed under partial standing ocean waves will help to better predict the influence of standing waves on breakwaters and seabed soil, and can provide some guidance for the design of offshore structures.

A numerical study of the slurry erosion in 90° horizontal elbows

The slurry erosion processes of horizontal elbows are investigated numerically using an Eulerian-Lagrangian method coupled with particle rebound and erosion model. First, a mechanical model for the internal multiphase flow involving slurry erosion in the 90° horizontal elbow is established and the corresponding governing equations are presented. Then, a two-way coupled numerical solution procedure is developed and its accuracy and stability are examined carefully using benchmark pipe flow models with experimental results. Using the validated numerical methods, the effects of flow velocity, fluid density and fluid viscosity on the flow and slurry erosion in the horizontal elbow are analyzed in detail. Finally, a prediction method of erosion rate distribution based on the pipe Froude number, particle Stokes number and the Dean number is proposed. In this method the pipe Froude number is employed to qualify the effect of ununiform distribution of particles, particle Stokes number and Dean number are combined to qualify the effects of inertia force, drag force and secondary flow. Using this approach, the location of the maximum erosion rate in horizontal elbows under different operating conditions can be predicted more conveniently.

Numerical analysis of the behavior of molten pool and the suppression mechanism of undercut defect in TIG-MIG hybrid welding

In order to investigate the multi-coupling transport phenomena in TIG-MIG hybrid arc welding, a three-dimensional model including droplet and molten pool was established. An innovative distribution pattern of arc heat and force that adapted to the evolution of molten pool surface was proposed, achieving a unified distribution of "arc current density-arc pressure-electromagnetic force-arc heat". The effect of TIG arc on molten pool behavior and undercut defect was quantitatively analyzed by comparing TIG-MIG hybrid welding with traditional MIG welding. The results showed that the electromagnetic repulsion between the two arcs with opposite currents increased the aspect ratio of the hybrid arc heat and force distribution. It led to a long and narrow gouging region, where the promoting effect of inertial force on the undercut was weakened by arc pressure and hydrostatic pressure. The liquid metal with a lower cooling rate had sufficient time to fully fill the weld toe and suppressed undercut. Sensitivity and dimensional analysis illustrated that the TIG-MIG hybrid arc eliminated undercut by reducing the inertia force, adjusting the arc pressure distribution, and enhancing the hydrostatic pressure. The groove sizes was predicated based on molten pool characteristics, including the stress state of liquid metal, morphology, and fluid flow patterns. It revealed the quantitative relationships among welding parameters, behavior of molten pool, and weld bead formation, promoting the implementation of digital twinning technology in the manufacturing industries.

Dynamic Analysis for Overturning of Pile Driving Machine, etc., on Soft Ground

There were quite a few overturning accidents of heavy machinery which have a high center of gravity such as pile driving machines, cranes, jacks, or working vehicles with aerial platform. Researches to study the background of the accidents have taken place from the structural stability point of view by the authors. The structural instability, as can be seen typically in the elastic buckling of columns, may be a blind spot because the structures deflect in different directions to that of the load, which makes it difficult to predict. According to the past investigations, the overturning mechanisms can be categorized into the three: (1) Type of overturning moment, (2) Type of structural instability and (3) Type of equilibrium transition, in which Type of equilibrium transition plays important role on the overturning on soft ground. The past investigations were based on the static analysis. Dynamic analysis is essential to include the effect of inertial forces which will significantly affect the overturning accidents on the soft ground. In the static analysis, the displacement inclination is considered to stop at the equilibrium position, but in the dynamic analysis it will continue increasing due to the inertial force. Then, it is possible the displacement may go beyond the equilibrium and even the stability limit to overturn. In this paper, the equations of motion will be first introduced, then behaviors of the machinery from time to time, i.e., the inclination-time curves, will be obtained by solving the equations. It is shown that the dynamic analysis can explain more precisely the overturning behaviors of the machinery on the soft foundation than the static analysis.

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.

Study of two-phase flow characteristics in the interrupted microchannels

The key factor restricting the use of microchannels in the cooling of micro-electronic equipment is the non-uniformity of the flow and temperature distribution. In this paper, the structure of the interrupted microchannel is improved by numerical simulation, coupling the Volume of Fluid (VOF) method with the Level-Set (LS) method to quantify the two-phase characteristics of the new microchannel using gas-liquid flow ratios, relative standard deviations, and pressure drop fluctuations. The simulation results proved that the effect of inertia force is largely offset by the widening design of the two side branches, and the flow resistance in the downstream branches is balanced. The effect of microchannel boiling heat transfer was enhanced by gas-liquid phase separation, and the gas flow relative standard deviation value of the interrupted microchannel was 83.1% lower than that of the traditional microchannel at the limit of high void fraction. The liquid-phase flow ratio increases with the inlet void fraction increasing, while the gas-phase flow ratio decreases. The relative standard deviation of the gas-to-liquid flow ratios were 0.215 and 0.134 for an inlet gas volume fraction of 0.2 and the mass flow rate of 80 kg/h, respectively, at which point the flow distribution was supported by the relative standard deviation. In addition, the fluctuation of pressure drop in different pipeline sections is opposite to the changing trend of void fraction, and the fluctuation frequency is the same. At the same time, the amplitude of pressure difference fluctuation under different flow patterns is defined, which provides a new idea for future flow pattern judgment.

Comparison of Dynamic Performance of an All-Metallic Vibration Isolator by Elliptic Method and Frequency Sweeping Method

A horizontally symmetric all-metallic vibration isolator (AM-VI) is proposed to further investigate the dynamic mechanical performance. The novel AM-VI was constructed by combining hat-shaped metal rubber and oblique springs, which were connected in parallel. The springs were arranged symmetrically relative to the support. The elliptic method and the frequency sweeping method were used to compare the dynamic stiffness and the loss factor of the AM-VI. The results demonstrated that the dynamic stiffness and the loss factor calculated by two distinct test methodologies were considerably different, indicating that the inertial force effect of the dynamic testing equipment should be taken into count when adopting the elliptic method. Furthermore, when the vibration isolation performance was evaluated by utilizing mechanical impedance and force transmissibility, the AM-VI achieved excellent vibration isolation performance within a broad frequency range.

Analysis of the effect of inertial forces of the electrolyte flow on the ECM machining effects of curvilinear rotary surfaces

Analysis of the effect of inertial forces of the electrolyte flow on the ECM machining effects of curvilinear rotary surfaces

Numerical investigation on turbulent flow, heat transfer, and entropy generation of water-based magnetic nanofluid flow in a tube with hemisphere porous under a uniform magnetic field

This paper numerically investigates the forced convection and entropy generation of Fe3O4 water nanofluid inside a cylindrical tube with porous hemisphere media. The flow regime is turbulent under a uniform magnetic field and constant heat flux, and to solve the equations, the finite volume method is applied. The combination of nanofluid, magnetic field and porous hemisphere media on the flow and heat transfer in a tube is the main novelty. The effects of different parameters such as Reynolds number (10,000 to 25,000), porosity (ε = 20%, 40%, and 80%.), the solid volume fraction of nanofluid (0.5 vol%, 1 vol%, and 2.5 vol%), friction factor and entropy generation of Ferro-nanofluid in the tube are investigated. The Nusselt number, entropy generation, and friction factor have been discussed and analyzed detailly. It is found that as the Reynolds number enhances, the effect of inertial forces becomes more dominant. Furthermore, by increasing the porosity to 0.8, the Nusselt number decreases to a minimum value. Heat transfer enhancement by increasing Hartmann's number is less effective than adding nanoparticles. A more significant Hartmann number and larger nanoparticle volume fraction lead to more extensive performance evaluation criteria. It is also found that adding a magnetic field increases the friction factor. Adding nanoparticles to the pure water decreases entropy generation by heat transfer per unit volume.

On analysis of magnetized viscous fluid flow in permeable channel with single wall carbon nano tubes dispersion by executing nano-layer approach

The prime motive of this pagination is to adumbrate attributes of water-based hybrid nanoliquid flow with dispersion of single wall carbon nanotubes. An innovative thermal conductance model containing the aspects of nanolayer formation along with shape and size of inserted particles is obliged. Flow transport mechanism is addressed mathematically in the form Navier Stokes equations with magnetization. In addition, heat and mass transport mechanism is manipulated by considering the impression of viscous dissipation and chemical reactions. Walls of channels are assumed to be porous in order to examine the phenomenon of suction and injection. Mathematical formulation of problem is represented in view of ODE’s and simulated computationally by Keller Box scheme. Subsequently, Newton method is utilized to solve system of nonlinear equations. Results are revealed through graphs and tables showing behavior of associated momentum, temperature and concentration profile against involved parameters. Quantities of engineering interest like wall drag coefficient, heat and mass fluxes are computed. Credibility of work is shown by creating match with existing study and an excellent agreement is found. After thorough analysis it is determined that heat flux increases with induction of single wall carbon nanotubes in base liquid. It is also manifested that thermal conductance of base fluid enriches with increase in thickness of nanolayer and radius of particles. In addition, positive trend in skin friction and heat flux coefficients is measured against elevation in nanoparticle volume fraction. Opposite behavior in velocity and temperature distributions against all flow variables near upper and lower walls of channel is depicted due to provision suction and injection wall velocities. Due to consideration of viscous dissipation heat transfer rate with in the flow domain reduces. By increasing Reynold number concentration distribution diminishes due to dominant effect of inertial forces. Decline in momentum distribution against Hall current parameter is adhered. Uplift and decrement in temperature distribution is manifested against heat source and sink parameters respectively.

Air Injection Into Water‐Saturated Granular Media—A Dimensional Meta‐Analysis

AbstractGas saturation degree and flow patterns are key factors for modeling and designing multiphase systems and operations. In turn, these factors are strongly related to the flow dynamics, which are controlled largely by the fluid and media properties. However, predicting the gas distribution and flow pattern remains elusive. Data from 11 series of steady air injection experiments into initially water‐saturated granular media, conducted with different media and flow geometries, are analyzed to identify the main factors governing air saturation and flow patterns. For air injection into otherwise water‐saturated granular media, the flow pattern is affected mainly by the ratio between the Capillary number (ratio of viscous to capillary forces) and the Bond number (ratio of gravitational to capillary forces), that is, by the ratio of viscous to gravitational forces. Moreover, the meta‐analysis presented here indicates that the steady air saturation degree is correlated strongly to flow velocity and grain diameter. Furthermore, analysis of experimental results from different studies of air injection into coarse, homogeneous, granular media (glass beads, sand) also suggests a significant effect of inertial forces. Both viscous and buoyancy forces increased air saturation, while capillary forces decreased the saturation degree. The ratio between capillary and buoyancy forces determines the air flow pattern during air injection into otherwise water‐saturated media.

Thermal valuation and entropy inspection of second-grade nanoscale fluid flow over a stretching surface by applying Koo–Kleinstreuer–Li relation

Abstract There are flow research centers on magnetohydrodynamic (MHD) emission of auxiliary liquid in an extended region. The prevailing model is constrained by attractions/infusion and gooey release. The administering model is based on the Koo–Kleinstreuer–Li nanofluid model in the existence of entropy generation. Final requirements of this model are addressed by implementing the shooting strategy, which incorporates a fourth approach for the Runge–Kutta strategy. Into the bargain, the last adds (in standard ordinary differential equations (ODE) divisions) are obtained from the measurable controls partial differential equations, which were represented toward the start of the overseeing model. The varieties for all boundaries are exhibited through graphical arrangements. It is noticed that expanding the substantial volume portion diminishes speed but builds nuclear power dispersion. Likewise, the classification of mathematical qualities on divider heat move rate and skin contact is introduced. Both Reynolds and Brinkman numbers improve the entropy rate of the thermal system resulting in the growth effects of inertial forces and the surface heat dissipation, respectively.