Influence Of Inertia Research Articles

Local velocity variations for a drop moving through an orifice: Effects of edge geometry and surface wettability

We investigate velocity variations inside of and surrounding a gravity driven drop impacting on and moving through a confining orifice, wherein the effects of edge geometry (round- vs. sharp-edged) and surface wettability (hydrophobic vs. hydrophilic) of the orifice are considered. Using refractive index matching and time-resolved PIV, we quantify the redistribution of energy in the drop and the surrounding fluid during the drop's impact and motion through a round-edged orifice. The measurements show the importance of a) drop kinetic energy transferred to and dissipated within the surrounding liquid, and b) the drop kinetic energy due to internal deformation and rotation during impact and passage through the orifice. While a rounded orifice edge prevents contact between the drop and orifice surface, a sharp edge promotes contact immediately upon impact, changing the near surface flow field as well as the drop passage dynamics. For a sharp-edged hydrophobic orifice, the contact lines remain localized near the orifice edge, but slipping and pinning strongly affect the drop propagation and outcome. For a sharp-edged hydrophilic orifice, on the other hand, the contact lines propagate away from the orifice edge, and their motion is coupled with the global velocity fields in the drop and the surrounding fluid. By examining the contact line propagation over a hydrophilic orifice surface with minimal drop penetration, we characterize two stages of drop spreading that exhibit power-law dependence with variable exponent. In the first stage, the contact line propagates under the influence of impact inertia and gravity. In the second stage, inertial influence subsides, and the contact line propagates mainly due to wettability.

On rotational dynamics of a finite-sized ellipsoidal particle in shear flows

The rotational dynamics of finite-sized ellipsoidal particles with different aspect ratios around their fixed mass centers in shear flows have been investigated by direct numerical simulations. Particles are fully resolved by a revised immersed boundary projection method, and their rotational motion is governed by Euler’s equation which is calculated in the particle-fixed frame. The particle Reynolds number varies from 10 to 300 based on the longest axis of the particle. The steady states of the prolate and oblate spheroids in uniform flow, linear shear flow with the moving top wall and fixed bottom wall, and wall-bounded turbulence are analyzed. It is observed that the longest particle axes are perpendicular to or have a large angle with the local flow direction in the flow-gradient plane, which leads to a large drag force. A linear stability analysis on the rotational motion of a finite-sized particle in uniform flow is also carried out for supporting this finding. In the linear shear flow, the influence of fluid inertia and fluid shear on the inclined angle is examined in detail. In wall-bounded turbulence, it is found that the particles in the buffer region and the outside of the boundary layer behave similarly in the mean sense as in the linear shear flow and uniform flow, respectively. The present results with intermediate to large particle Reynolds numbers can be regarded as a starting point to understand the dynamics of heavy finite-sized particles in viscous flows.

The Analysis of Controllability and Stability of an Approximate Model of Heat Transfer in an Autoclave

Introduction.Ensuring the safety of country food industry in terms of the duration of storage and the quality of products is impossible without sterilizing products in autoclaves. The effectiveness of the sterilization processes depends on the degree of their automation. In the last twenty years, the improvement of automatic and automated control systems was primarily based on the development of technical means for automation without theoretical justification of decision-making. The proposed work is aimed at identifying the links between the parameters and connections of the sterilization process and the choice of structural and parametric features of the control system. Materials and Methods. A qualitative analysis is carried out based on the modern theory of automatic control for an approximative model of the thermal process of steam heating in an autoclave, taking into account the laws of heat transfer and the sufficiency of using a twodimensional model depending upon the structural and functional features of the model, which have regard to the parameters and relationships of the process, namely, the Kalman’s controllability properties of the model in the time domain in the state-space representation (the transition from the transfer function with zeros in the numerator to the normal differential system differential equations is also described). There were also analized the stability properties of the model in the frequency domain by means of transfer functions and structural transformations and the relationship of parameters in the form of inequalities with the subsequent choice of proportional-integral-differential configuration components for a real autoclave using the matrix of expert estimates. Results. It is shown that to make a qualitatively study of the issues of controllability and stability of the approximative model of the thermal process of water heating by steam in an autoclave, depending on the process parameters, it is necessary to represent the model the time domain (in the state-space representation) and in the frequency domain (in the form of transfer functions). The analysis of the controllability of the process is based on three approaches: the first (formalized) approach is based on the representation of the model in the form of a normal system of ordinary differential equations in the Cauchy form with the development of a method of decreasing the order of the higher derivatives of coordinates and introducing additional control signals taking into account the control derivatives; the second (unformalized) is based on the exclusion of management derivatives through structural transformation; the third (direct) approach uses the first-order heat balance and heat conduction equations derived from physical considerations. Under the conditions of Kalman’s controllability, dependencies between the parameters of the process and the degree of its controllability have been obtained.The analysis of the stability of the process is based on studying the poles of the transfer functions in the frequency domain and the characteristic roots of the equations of state in the time domain. On the basis of structural transformations, a closed canister heating loop with water with inertia, depending on the autoclave charging parameters, is isolated. Transient processes in this circuit take an amplifying, aperiodic or integral character, which affects the nature of the transient processes of the control system as a whole. The formalized choice of the components of the proportional-integral-differential regulation law is carried out depending on the frequency of application of the degree of loading and the need for the components of the proportional-integral-differential regulator using the matrix of expert estimates. Conclusions. The results of the research will serve as the material for the development of a real model of the autoclaving process, taking into account the static and dynamic characteristics of measuring, conversion and actuating elements, investigating the influence and compensation of inertia and nonlinearities of real elements, followed by the development of an automated system for controlling the sterilization process in autoclaves. The results of the work can be used to study general and applied problems of optimal control in both food and other industries, for example, in the production of building materials and the production of rubber products.

Acceleration statistics of prolate spheroidal particles in turbulent channel flow

ABSTRACTComputation of a dilute suspension of prolate spheroidal particles in a turbulent channel flow is undertaken to study the influence of inertia and shape on acceleration statistics. A pseudo-spectral direct numerical simulation is coupled with Lagrangian tracking under the one-way coupling assumption. Simulations are carried out at friction Reynolds number , for three aspect ratios , 3 and 10, and two Stokes numbers St=5 and 30. Results indicate that, as a consequence of the filtering effect of inertia, particle acceleration RMS decreases with increasing inertia. In addition, the normalised streamwise acceleration PDFs depart from that of the conditional fluid and their tails become narrower as inertia is increased. Furthermore, acceleration statistics show that particle elongation has a significant effect on the mean drag and on the particle selective sampling. Moreover, the classification of elongated particle behaviour in turbulent channel flow based on a global Stokes number is questioned. The zero-crossing acceleration autocorrelation timescales presented points out the need for a local dimensionless number estimation adapted to the case of prolate spheroids.

Application of Phase Averaging Method for Measuring Kites Performance: Onshore Results

This paper describes an experimental set-up aiming to control and measure performances of small leading edge inflatable tube kites, with surface area of less than 35 m2. This set-up can be deployed either onshore or on a dedicated boat. This article focuses on the onshore results. A 3D load cell is used to obtain the position of the kite under a straight-line assumption. A wind profiler (SODAR) is deployed to determine the wind speed and direction at the kite position. A specific post-processing of the data is presented, including phase averaging. The guideline of this work is to estimate the variation of the aerodynamic lift coefficient and lift to drag ratio along figure-of-eight trajectories. Results, for a chosen particular case, show a decrease of lift coefficient of about 20% of the maximum value during turning maneuvers of the kite. The lift to drag ratio evolution along a trajectory is also observed to go through a local minimum during turning maneuvers of the kite in this case. Influence of weight and inertia is highlighted introducing a point mass model of the kite and tethers. Buckling phenomena of the kite inflatable leading edge tube are highlighted and it is shown that they cause control problems.

Analysis to the Influence of Inertia on Parallel VSG’s Stability

Virtual Synchronous Generator (VSG) is a flexible control approach for power electronic converters in the power system. In this paper, the nonlinear model for a pair of VSGs in parallel is built, and corresponding small-signal linear model considering each link is further established based on the second-order model of synchronous generator. Compared to the response curves of parallel model of inverter power supply with characteristics of synchronous generator in MATLAB / SIMULINK, the accuracy of the small signal model is verified. With the help of small signal model and its analysis method, the virtual moment of inertia, an important parameter of virtual synchronous machine, is studied in detail. For parallel VSGs, the universal selection principle of virtual moment of inertia J is put forward considering different parameters of two machines, and the results of simulation show that the proposed principle of parameter selection can expand the range of parameter selection and the stability of the system can be improved.

The influence of political risk, inertia and imitative behavior on the location choice of Chinese multinational enterprises

PurposeDrawing on the institutional perspective, the purpose of this paper is to investigate how state ownership moderates the relationships between political risk, inertia and mimetic behavior, and the location choice of Chinese multinational enterprises (MNEs).Design/methodology/approachThe authors argue that state ownership leads Chinese firms to behave toward political risk in an unconventional way, and that government support makes them less dependent on their own and other Chinese firms’ prior host country experience. The authors tested the hypotheses using data on outward foreign direct investment (OFDI) decisions made by 186 Chinese firms in 93 countries.FindingsThe authors found that Chinese state-owned enterprises (SOEs), compared to non-SOEs, are more likely to move into countries with high political risk, and that they are less likely to be inertial and mimetic.Originality/valueBuilding on the distinction between macro- and micro-political risk, The authors contribute to the political risk literature by developing several arguments that explains why political risk varies across investing firms in a given host country. Moreover, this is one of the first studies of its kind to investigate the moderating effect of state ownership on the relationship between inertial and mimetic behavior, and the location choice of Chinese MNEs.

Foreign sequential entry mode choice

PurposeThe purpose of this paper is to use the theoretical perspective of structural inertia as a unique lens to study foreign sequential entry mode choices of multinational firms.Design/methodology/approachIt adopts quantitative analysis of a sample of 121 Chinese publicly listed firms with 564 foreign entry incidents in the 2001-2012 period to test the hypotheses.FindingsThe empirical results show that multinational firms have a tendency to adopt the same mode in the subsequent entry as the number of prior entry mode choice of a given type (joint venture (JV) in this study) increases. The results support the theoretical prediction that organizations repeat their past activities due to structural inertia. Moreover, such an inertia effect in foreign sequential entry mode choices becomes stronger for older multinational firms, larger multinational firms and state-owned multinational firms.Research limitations/implicationsConsistent with existing research, this study focuses on the entry mode choice between JV and wholly owned subsidiaries. However, it is better to examine the relationship identified in the study for different types of entry mode choices to assess result generalizability.Practical implicationsIt reminds managers of multinational firms that they should be cautious to the influence of structural inertia that can be a barrier to strategic flexibility when they make entry mode choices.Originality/valueThe main contribution of this study resides in introducing structural inertia perspective to help understand the determinants of foreign sequential entry mode choices of multinational firms.

Improved thermal transient modeling with new 3-order numerical solution for a district heating network with consideration of the pipe wall's thermal inertia

An improved thermal transient model was put forward to predict the thermal transient behavior of a long pipe. The model took particular consideration of the influences of the pipe wall's thermal inertia. Then a new 3-order numerical solution was presented to solve the proposed model. The new solution would not only preserve the sharp temperature front during the heat propagation, but also achieve fine computational accuracy even for the coarse grids. In addition, the proposed model and numerical solution could be easily coupled with enormous common hydraulic models to be available to a general district heating (DH) network. The model and solution were validated in a real DH system. The simulation results had a good agreement with the measured data. Furthermore, in order to quantify the degree of the influence of pipe wall's thermal inertia, a practical indicator was developed based on ten types of often-used pipes in the DH projects. The research results showed that, for the large pipes with diameters over DN 200, the simulation errors caused by neglecting the pipe wall's thermal inertia were no more than 10%, which meant it was unnecessary to consider the thermal inertia for larger diameter pipes during the process of modeling.

The effect of initial geometric imperfection on the nonlinear resonance of functionally graded carbon nanotube-reinforced composite rectangular plates

The purpose of the present study is to examine the impact of initial geometric imperfection on the nonlinear dynamical characteristics of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) rectangular plates under a harmonic excitation transverse load. The considered plate is assumed to be made of matrix and single-walled carbon nanotubes (SWCNTs). The rule of mixture is employed to calculate the effective material properties of the plate. Within the framework of the parabolic shear deformation plate theory with taking the influence of transverse shear deformation and rotary inertia into account, Hamilton's principle is utilized to derive the geometrically nonlinear mathematical formulation including the governing equations and corresponding boundary conditions of initially imperfect FG-CNTRC plates. Afterwards, with the aid of an efficient multistep numerical solution methodology, the frequency-amplitude and forcing-amplitude curves of initially imperfect FG-CNTRC rectangular plates with various edge conditions are provided, demonstrating the influence of initial imperfection, geometrical parameters, and edge conditions. It is displayed that an increase in the initial geometric imperfection intensifies the softening-type behavior of system, while no softening behavior can be found in the frequency-amplitude curve of a perfect plate.

The size-dependent free vibration analysis of a rectangular Mindlin microplate coupled with fluid

In this paper, the size-effect and fluid-structure interaction on the vibrational characteristics of a simply supported rectangular microplate is investigated. The influences of rotary inertia and transverse shear deformation which have the remarkable role in the analysis of moderately thick microplates are considered. The first order shear deformation theory along with the modified couple stress theory has been used to perform the free vibrational analysis of the considered problem. The Hamilton's principle is employed to derive the governing differential equations of motion and the corresponding boundary conditions. The fluid is assumed to be incompressible, inviscid and irrotational. The fluid velocity potential is obtained using the boundary and compatibility conditions. Then the Rayleigh-Ritz method has been applied to calculate the natural frequencies of the system. A convergence study is carried out. The obtained results are compared against available data in the published papers and very good agreements have been observed. Finally by referring to the numerical results, the effects of dimensionless thickness, side to thickness ratio, aspect ratio, material length scale parameter and fluid depth ratio on the natural frequencies are discussed in details.

Wavefront evolution of compression waves propagating in high speed railway tunnels

The amplitude of micro-pressure wave emitted from the exit portal of a high-speed railway tunnel is approximately proportional to the pressure gradient of the internal wavefronts approaching the portal. For long tunnels, the evolution during propagation is an important factor for estimating the pressure gradient in the exit wavefront. Moreover, the relationship between the entrance and exit states depends upon the conflicting influences of inertia and damping along the propagation. In this paper, the investigation is done to study the evolution of wavefronts with different initial waveforms and to assess the influence of friction and train speed in the process. This work is based on numerical simulations of wavefront propagation using a third-order monotonic upwind scheme for conservation laws and backed up by field measurements. Numerical analyses show that the wavefront evolution not only depends on the pressure amplitude and the maximum pressure gradient of the initial wavefront but also depends strongly on the shape and timing of the peak steepness of ∂P/∂t. The predictions also demonstrate the existence of a critical tunnel length. For any particular train and tunnel entrance, the magnitudes of the micro-pressure waves increase with the tunnel length when this length is below the critical one and decrease with the tunnel length otherwise. The critical length decreases with the increase of the tunnel wall friction and the train speed.

Combined effects of fluid–solid interfacial slip and fluid inertia on the hydrodynamic performance of square shape textured parallel sliding contacts

Lubrication performances of square shape textured parallel sliding contacts are examined under the combined influence of both fluid inertia and fluid slippage at the fluid–solid interface. A two-component slip length model and first-order perturbation method are adopted to formulate pressure governing equation consisting of fluid-slip and fluid inertia terms. The effect of texture size (aspect ratio), texture height ratio, reduced Reynolds number, slip length coefficient and critical threshold shear stress on the performance parameters like load support, end flow and friction parameter of parallel sliding contacts is studied. The results indicate that effect of fluid-slip is more influential than fluid inertia; therefore, the result shows similar and closer trend to the fluid-slip results. However, the magnitude of performance parameters depends on the effect of fluid inertia. Moreover, aspect ratio of 0.3–0.5 and lower value of texture height ratios can be used to achieve better hydrodynamic lubrication performance in parallel sliding contacts.

Batch evaporation power cycle: Influence of thermal inertia and residence time

The transition in the energy market and the growing share of renewable energy sources have been boosting the research in new power cycles. For example, the concept of batch evaporation in the Misselhorn Cycle promises to increase the overall efficiency in low-temperature applications and therefore saves resources. In this paper, a dynamic evaporator model was extended in order to prove the feasibility of the Misselhorn Cycle despite its transient character. In this context, the thermal capacity of the wall material as well as the residence time of the heat source medium were added. The previous, underlying model predicted an improved system efficiency for the Misselhorn Cycle of about 50% compared to an Organic Rankine Cycle (ORC) at 100C∘. Initially, the results of the extended model showed a negative influence of the inertial effects on the possible net power output (advantage over ORC only 10%). However, an unheated discharge phase and reduced dimensions of the heat exchanger could compensate these drawbacks and achieved results (about 40% better than ORC) in the same range as the previous, simple model predicted. These findings prove the general practical feasibility of the Misselhorn Cycle.

Trajectory control and random vibration control of nonlinear system with dielectric elastomer actuator

Dielectric elastomer actuators have gained extensive attention in scientific and industrial communities with the rapid development of soft robot technology. There still remain some questions on the control aspect of nonlinear system with dielectric elastomer actuator. The first is whether the soft actuator can successfully drive the primary structure to track an arbitrary prescribed trajectory. The second is how to suppress the random vibration around the equilibrium position when the primary structure is disturbed by external excitation. This article seeks the answers for these two questions. By directly solving the governing equation of motion, an open-loop control technique is designed to track a prescribed trajectory. The effectiveness of the trajectory tracking technique is investigated and the limitation is illustrated by the influence of inertia of the primary structure. Based on the stochastic averaging of energy envelope and stochastic dynamic programming principle, a clipped control strategy is proposed by slightly adjusting the voltage in real time to suppress the random vibration around the equilibrium position. The good effectiveness and high robustness of the clipped control strategy are verified numerically. This work may provide some guidelines for the control aspect of nonlinear systems with dielectric elastomer actuators.

The effect of non-linear inertia on dynamic response of asymmetric multi-story buildings

The goal of this paper is to inspect the influence of non-linear inertia on dynamic response of multi-story asymmetric buildings. In this study unlike conventional linear approach, the non-linear inertial terms are considered in the equations of motion. For considering non-linear inertia, the motion equations are derived in local rotary coordinates system. Also, the stiffness and damping parameters are defined in the rotary coordinates system. In the novel approach which is proposed in this paper, the motion equations are different with conventional linear approach. Numerical examples are presented to compare the response of the proposed model and conventional linear model. The modeled building response is derived under harmonic excitation. The results show that if non-linear inertia is considered, the dynamic response of asymmetric multi-story buildings may become different with conventional linear approach.

Use of the Kolsky method for dynamic tests of brittle media

The dynamic test techniques used to obtain the mechanical properties of brittle materials are described. The techniques are based on the fundamental Kolsky method using the Split-Hopkinson Pressure Bar. Dynamic tests are characterized by high intensity and short duration and the influence of inertia on their results should be ruled out which is especially important for brittle media. The prerequisites and assumptions presented methods are described to justify the validity of the obtained data. The methods allow to obtain dynamic deformation diagrams at compression, splitting, indirect tension, shear and triaxial stress state and also to determine the ultimate strength, strain and time properties of brittle materials. The techniques are approved in the tests of ceramic bricks, finegrain concrete and fiber-reinforced concrete.

Influence of inertia and material properties on discrete simulation of dynamic fracture of concrete

It is well known that the material resistance to fracture increases with increasing strain rate. For relatively slow strain rates, the response is strongly dependent on the material fracture properties such as material strength or fracture energy, whereas with further increase of loading rate, the loading force is getting influenced predominantly by the material inertia. The response of the material changes with strain rate in the sense of loading force as well as character of the crack pattern. The contribution is focused on simulations of fracture experiments at various strain rates. Dynamical concrete fracture is simulated using meso-scale discrete model, i.e. a system of interconnected discrete particles. Material properties in the model are randomly distributed within the volume domain. Similar to quasi-static loading rates, the material randomness influences the dynamic fracture as well. Deterministic and probabilistic simulations are compared and the influence of material parameters and their strain rate dependence are discussed.

Design of Fuzzy PID Temperature Control System

Temperature plays an important role in daily life, industry production and scientific experimentation. However, because of the multi characteristics of nonlinearity, large lag, and time-varying of control objects, there will be great difficulties in establishing accurate mathematical models with mathematical methods. In order to achieve well controlling effects, this paper proposes a mature controlling system. This system combines PID algorithm and fuzzy control to design a fuzzy PID intelligent controller, which could process complex data and complex systems simultaneously. The high flexibility of fuzzy control and the high precision of PID control of this system could solve the influence of large inertia and interference of the temperature control system. This design will adopt the STC89C52 MCU as the main control core. Meanwhile, the fuzzy PID controller are combined with fuzzy control and PID control to control the temperature. In this paper, we first introduce the hardware composition of PID temperature control system. Secondly, we use proteus to build the general circuit diagram, and then use KEIL software to program again. Finally, we simulate the system and analyze the simulation results by the simulink module in MATLAB, and finally achieve the expected results.

A Finite Element Analysis of Pore Throat Ratio on the Characteristics of Flow Structure through Low Permeability Reservoir

Present research work focus on the two–dimensional axisymmetric incompressible flow of a Newtonian fluid through Pore–Throat tube. Different model parameters are employed to investigate the influence of inertia and impact of various pore throat ratios on flow structure, pressure differential, stress distribution and friction factor. A time–marching finite element method is used to analyse the numerical solutions through flow structure via streamline distribution, pressure distribution, speed and stress. A time–marching Taylor–Galerkin/Pressure–Correction procedure in semi–implicit form is employed to achieve the steady–state solutions. Predicted numerical results demonstrate Pore–Throat ratio have vital impact on the flow field distribution.