Account Energy Dissipation Research Articles

Harmonic oscillations of a piezoceramic functional-graded sectional cylinders with account of energy dissipation

Harmonic oscillations of piezoceramic functional-gradient sectioned hollow cylinders are studied, taking into account energy dissipation. A cylinder of finite length is considered, consisting of an even number of sections polarized in the circular direction, which are connected to each other by similar sides. The material is considered to be functionally heterogeneous in the direction of the previous polarization. The cylinder is loaded by the potential difference applied to the flat faces of the sections. The calculation is performed by the finite element method. The forming of damping matrix and determining the coefficients corresponding to the four ways of introducing Rayleigh damping into the FEM is described. Amplitude-frequency responses taking into account damping are built for displacements, charge on the electrodes, electrical admittance and its logarithm. The consideration of energy dissipation according to the Rayleigh damping model is related to the experimental data due to the Q factor of the piezo element. The frequencies of electrical resonances, anti-resonances and the corresponding electromechanical coupling coefficients for functionally inhomogeneous and homogeneous cylinders are determined. For the functional-gradient piezoelectric element of the considered configuration, the maximum CEMC occurs at the frequency of the second electrical resonance. At this frequency, the dynamic stress-strain state of the cylinder is investigated. Forms of oscillations and distribution of stress amplitude values are constructed. The largest normal stresses according to the Coulomb-Mohr strength theory are determined and compared with the von Mises strength theory. FEA allows three-dimensional calculation of harmonic oscillations of functional-gradient piezo elements of complicated geometry. The determined frequencies of electrical resonance and anti-resonance and the corresponding CEMC make it possible to choose the most effective operating mode of the piezo element. The FEM mathematical apparatus makes it possible to quickly and qualitatively evaluate the strength, determine the charge on the electrodes, the current in the circuit, build the amplitude-frequency characteristics of admittance and impedance, and evaluate the efficiency of energy conversion.

MASS TRANSFER IN THE BIOREACTOR DURING GAS DISPERSION FROM THE STIRRER VORTEX CAVITY

Gas-liquid bioreactors in which the introduction of the gas substrate in the culture liquid is carried out from the vortex cavity formed by the rotation of the stirrer. In order to simplify the design and intensify mass transfer a new method of dispersing the gas substrate from the vortex cavity is proposed and studied. It consists in maintaining local zones with reduced pressure in the liquid behind the rotating paddles and creating the necessary conditions for the introduction of the gas substrate. On the basis of numerical simulation the pressure is calculated and the zones of low pressure in liquid behind the stirrer paddles are determined. The value of differential pressure necessary for gas dispersion has been estimated. The angular velocity of liquid rotation depending on the number of partitions on the apparatus wall and the number of mixer revolutions is presented. The gas content in the liquid during the implementation of the investigated method has been determined. The average surface diameter of gas bubbles and interfacial surface of gas-liquid medium were calculated from experimental data. The power spent on stirring in the apparatus has been established and the power criterion with regard to gas content has been determined. Mass transfer at intensive gas dispersion from gas vortex cavity into liquid has been investigated. Criterion dependence for calculation of mass transfer coefficient is presented, taking into account energy dissipation spent on mixing and interfacial surface. The fields of application of bioreactor with new method of gas dispersion are shown.

Rigid flexible coupling contact mechanism for oral and maxillofacial skin and soft tissues

Background and Objectives:The existing medical clinical treatment institutions mostly use rigid structures to come into contact with flexible skin. The rigid flexible coupled contact biomechanical model for the skin is the first step that urgently needs to be considered in the process of medical clinical operations. However, there has been currently no effective biomechanical contact model available. Methods:Based on the principle of elastic interface deformation, the basic biomechanical characteristics of oral and maxillofacial skin and soft tissues were analyzed to address the unknown mechanism of rigid body and maxillofacial contact in oral imaging operations. A nonlinear characterization method for the mechanical properties of oral and maxillofacial skin soft tissues was proposed by deriving a general contact force model that takes into account energy dissipation. However, the problem of the inability to obtain analytical solutions for the parameters of the dynamic model exists. It is necessary to perform particle swarm parameter identification on different nonlinear contact models and verify the accuracy of the algorithm through numerical simulation. A maxillofacial contact experiment was conducted to verify the operation process of an oral imaging robot. Results:After experimental analysis, it was found that the comprehensive average error between the model and the actual contact force was 0.13325 N. The absolute error of the maximum deformation displacement was below 0.18 N, which verified the effectiveness and safety of the contact model in the contact process of the oral imaging robot system. Conclusions:The results indicate that the output force of the model has been in good agreement with the actual contact force.

Разработка математической модели стеллажного крана-штабелера с учетом диссипации энергии

Stacker cranes are widely used in automated warehouses. The actual task is to increase their energy efficiency and productivity. Simulation mathematical models are used for the solution of this problem at the stage of research and development works. We have developed a mathematical model of a rack stacker crane in long spatial displacements taking into account energy dissipation of linear coordinates of the cart and the cargo carriage. The model is a system of two second-order Lagrange differential equations. Partial derivatives of analytical expressions of kinetic and potential energies of the dynamic stacker crane system as well as dissipative Rayleigh function are used for derivation of the differential equations. Different values of dissipation coefficients for two linear coordinates of the stacker crane can be used. Using SimInTech we develop a simulation model of a conventional stacker crane based on the suggested system of differential equations and represented in the form of a block diagram. The developed simulation model is described and an example of its use is given. A complex model of a shelf stacker crane includes as a constituent part a procedure of determining time intervals of equivalent-accelerated motion of the links. Examples of time dependences of the crane bogie and cargo carriage coordinates, drive forces providing the set coordinate dependences, drives work and total work are given. The developed mathematical model of the stacker-crane can be used for the modelling of the processes of the cargo moving along the rack, its raising to the given height corresponding to the rack target cell, its lowering as well as for the estimation of the energy input of the crane.

SIMULATION OF INTERMEDIATE VISCOELASTIC SUPPORT UNDER NON-STATIONARY VIBRATIONS OF TIMOSHENKO BEAMS

When modeling mechanical objects and their systems, mathematical models developed for an elastic domain are most often used, which in some cases can lead to significant inaccuracies in calculations. The use of mathematical models that take into account visco-elastic properties or energy dissipation allows to obtain more realistic models, which will make it possible to obtain more accurate calculation results. In the paper non-stationary loading of a mechanical system, consisting of a beam hinged at the edges, and an additional support installed in the span of the beam is considered. We use a beam deformation model, which is based on the hypotheses of S. P. Timoshenko and takes into account the inertia of rotation and shear. The system of partial differential equations describing the deformation of the beam is solved by expanding the desired functions into the corresponding Fourier series and subsequent using the integral Laplace transform. The additional support is assumed to be realistic rather than absolutely rigid, having linear elastic and viscous components. It is assumed that at the point of attachment of the additional support to the beam their displacements coincide. The reaction between the beam and the additional support is replaced by an external unknown concentrated force applied to the beam, which changes with time. The law of change in time of this unknown reaction is determined from the solution of the Volterra integral equation. A method for obtaining an integral equation for an unknown reaction is described. Analytical relations and calculation results for specific numerical parameters are given. The influence of stiffness and viscosity on the determined reaction of the additional support, as well as on the deflections of the beam at various points, is investigated. The results obtained can also be used for damping forced vibrations of mechanical systems.

Parametric vibrations of piezoelectric viscoelastic cylindrical panels taking into account transverse shear deformations

The paper presents a numerical-analytical approach to solving problems of parametric vibrations of layered hinged piezoelectric viscoelastic cylindrical panels under electromechanical harmonic loading. The mathematical model is constructed using mechanical hypotheses about layer-by-layer approximation of shear deformations by quadratic functions on the thickness of panel, which are supplemented by adequate hypotheses on the distribution of electric field quantities when the components of the electric field strength vector and the normal component of the electric induction vector are different from zero. The dissipative properties of materials are taken into account on the basis of the theory of linear viscoelectric elasticity. To solve the problems, a technique based on the use of the variation principle and the representation of the required quantities in the form of decomposition into double trigonometric series has been developed. This makes it possible to reduce the considered problems to Mathieu-Hill-type equations taking into account energy dissipation, which are solved by the method of harmonic linearization, which allows to determine the boundaries of the regions of dynamic instability.

Free and Forced Vibrations of a Composite Plate in a Perfect Compressible Fluid, Taking into Account Energy Dissipation in the Plate and Fluid

Free and Forced Vibrations of a Composite Plate in a Perfect Compressible Fluid, Taking into Account Energy Dissipation in the Plate and Fluid

Energy dissipation and resilience of precast segmented concrete-filled steel tube self-centering column: Parameter study and design methodology

Based on the pseudo-static test of precast segmented concrete-filled steel-tube (PSCFST) self-centering columns, a fiber-section analysis model was established, then validated through comparison with the test results. After that, a detailed parameter analysis is conducted to investigate the energy-dissipation and the resilience performance of the PSCFST column. Furthermore, a design process was proposed which takes into account both energy dissipation and self-centering by introducing the two coefficients, the energy dissipation coefficient, λED, and resiliency coefficient, ζSC. The optimized ratio of the energy-dissipated (ED) reinforcements and the posttension prestressing tendons are determined based on the two coefficients. Based on the concept of contradictory between the energy dissipation and resiliency performance, the design procedure showed that the separation of the two functional requirements of energy dissipation and self-centering is more convenient. Compared the PSCFST self-centering column with original RC column, the ultimate bearing capacity of PSCFST self-centering column is increased by about 35.73%. When the ratio of the ED bars and the prestressing tendons is 2:1, there is an ideal flag hysteresis relationship for the self-centering column with favorite energy dissipation.

SOLVING THE PROBLEM OF THERMODYNAMIC INEQUALITIES

It is shown that the combined equation of the 1st and 2nd principles of classical thermodynamics does not transform into inequality in the case of irreversible processes, if the external energy exchange of the system is expressed in terms of energy carrier flows. This means that thermodynamic inequalities are generated by attempts to take into account the irreversibility of real (non-static) processes, without taking into account explicitly its reasons - the inhomogeneity of the system and the presence of internal sources not only for entropy, but also for other parameters.On this basis, exact expressions of heat and work in open nonequilibrium systems, as well as their dissipative function, are obtained. The physical meaning of entropy as a thermal impulse and the unprovability of the principle of its increase in the framework of equilibrium systems are revealed. Non-entropy criteria for evolution are proposed and the latter is shown to be incompatible not only with the second law of thermodynamics, but also with the laws of conservation of energy carriers. The elimination of thermodynamic inequalities opens up the possibility of applying the equations of thermodynamics, taking into account energy dissipation, to other fundamental disciplines.

Регулирование динамических характеристик пролетных строений мостов в условиях изменяющегося воздействия временной подвижной нагрузки

It is known that an unregulated structure is likened to an unadjusted musical instrument [7]. The adjusted dynamic stress-strain state of the bridge spans will be adequate to the parameters of the design and operational state as a result of the introduction of regulation and control of fl uctuations in the conditions of the changing impact of the temporary mobile load. Methods for regulating dynamic characteristics by changing the frequency of natural oscillations of the system, taking into account energy dissipation, as well as introducing into the oscillatory process a transformed form of intense oscillations in the process of artifi cial or selective resonance, in which the oscillations of the system either damp or cease to be dangerous, are especially carefully considered. Attention is focused on the infl uence of the defectiveness of the roadway with an increase in the mass and speed of a temporary moving load. For this purpose, a classifi er of bridge deck defects has been developed to clarify the boundaries of the eff ect of a defect on the dynamic operation of a structure [1, 3]. Analysis of the structural content and criteria for determining shows the insuffi ciency of the components assessing the eff ect of the temporary mobile load on the span under non-stationary oscillations, and also reveals contradictions in the assessment of the dynamic additive . The practical use of the research results is advisable by the Ministry of Transport Construction in the implementation of state national programs and projects for improving structures, calculation methods, design and operation of bridge structures

ON A METHOD FOR CALCULATING HEAT TRANSFER IN A MOVING FLUID TAKING INTO ACCOUNT ENERGY DISSIPATION

An approximate analytical solution to a heat transfer problem for a moving fluid in a cylindrical channel is obtained using an additional new function and additional boundary conditions in the heat balance integral method and taking into account energy dissipation under a first-order boundary condition that varies along the longitudinal coordinate. The use of an additional new function that determines the temperature change along the longitudinal variable in the center of the channel makes it possible to reduce the solution of the partial differential equation to the integration of an ordinary differential equation. Additional boundary conditions are found in such a way that their satisfaction for the new solution is equivalent to the satisfaction of the differential equation at boundary points.

Simplified Method for the Identification of Erosion and Flooding Hazard Hotspots on Sandy Beaches

Montes, J.; Benavente, J.; Silva, R.; Plomaritis, T.A., and Del Rio, L., 2020. Simplified method for the identification of erosion and flooding hazard hotspots on sandy beaches. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1206-1210. Coconut Creek (Florida), ISSN 0749-0208. The exponential growth in coastal population over the recent decades has intensified the pressure on coastal zones and has placed them on the focus of the scientific community, particularly in the context of climate change. This work presents a reliable method to easily identify current and future hazard hotspots on sandy beaches in monitored coastal areas. Hotspots are defined as areas with high erosion and flooding hazard, which require detailed further study. The methodology is based into the application of WAPO (Wave Propagation On the Coast) model and DSAS (Digital Shoreline Analysis System) tool. WAPO model propagates monochromatic wave trains over a variable bottom and extracts the energy flux on the coast, taking into account refraction, diffraction, shoaling, reflection and energy dissipation. DSAS tool calculates rates of shoreline change from multiple historical shoreline positions. The method was applied in La Atunara beach in the South of Spain, influenced by the presence of anthropic structures and a complex bathymetry. Wave data used in the models were extracted by a joint probability analysis of wave height, period and direction for modal and storm conditions in the zone. Additionally, synthetic cases were generated for assessing climate change impact by modifying mean sea level parameters according to the IPCC scenarios. Results show that this methodology provides a simplified assessment of hotspots that allows focusing on the most vulnerable areas. This avoids the use of more complex and time-consuming models in large areas, allowing efforts to be concentrated on the identified hotspots.

Energy consumption of small-since mixers in emulsification processes

There is given a common method of calculation of power consumptions for emulsification at systems liquid-liquid in low volume mixing devices (rotary pulsating apparatuses and rotor-disc mixers) in this Article. Named mixing devices shown a high efficiency at processing of liquid-liquid systems and are widely used at chemical processes. It is shown that at determination of energy consumptions it is need to take in account energy dissipation processes, caused by viscous friction forces, which affect a significant influence at high gradients of speeds turbulent motion. It is obtained the ratio, which connects an angular velocity of rotor rotation of mixing device and a characteristic size of dispersed phase particles of a mixing device. There are given an experimental equations of consumed power of rotor-disc mixers on rotor rotations number and characteristic sizes of dispersed particles for th system water and diesel fuel. Also it is known that in decrease of dispersed particles size and in increase of volume consumption of the processed mixture, the consumed power is increase, and it due to the fact by increase energy consumption for creation of interphase surface.

Энергопотребление процессов эмульгирования в малообъемных перемешивающих аппаратах

There is given in this thesis a general method of calculation of power consumption for emulgation in systems liquid-liquid in small-size mixing devices (rotor-pulsation apparatuses and rotor-disc mixers). This mixing devices, have shown a high efficiency at processing of liquid-liquid systems and are wide using chemical processes. The base of calculation method is an energy ratio to describe of developed turbulent motion, pulsation intensity of which is enough for create of dispersed particles of given size and concentration, which provide a necessary surface of phases contact. It is shown, that in determination of energy consumption it is need to take in account energy dissipation processes, due to viscous friction forces, which have a significant influence at high gradients of turbulent motion. There is obtained a ratio, which connects an angular velocity of rotor rotation of mixing device and a characterized size of dispersed phase particles.There is given an experimental dependencies of consumed power of rotor-disc mixers on rotor rotations number of mixing device and characterized sizes of dispersed particles for systems water-diesel fuel. It was determined, that are decreasing of dispersed particles sizes and in increasing of volumetric flow of processing mixture a value of consumed power increases, and it is related with by increase of energy consumption for creating of interphase surface. It was determined, that a power, consumed by rotor-disc mixer, for emulsion making with averaged dispersion size of particles at range 5-25 mkm, increases by increase of rotation numbers ~n0.37. Comparison of theoretical equations and experimental data have shown adequacy of supposed calculation method of energy consumption.

On a Method for Calculating Heat Transfer in a Moving Fluid Taking into Account Energy Dissipation

On a Method for Calculating Heat Transfer in a Moving Fluid Taking into Account Energy Dissipation

Finite-element simulation of cyclic compression of a cylinder with account for energy dissipation

The article considers the solution of the associated thermoelastic problem of dynamic compression of a cylindrical sample from hyperelastic material in an axisymmetric formulation using the Abaqus Simulia finite element modeling software package. The authors present the results of a numerical experiment, carry out its analysis, make a conclusion if it is necessary to take into account energy dissipation in the study of materials operating under cyclic loading.

The Method of Accurate Determination of Frequencies and Modes of Vibration of the Resonator of the Vibration Frequency Sensor

The article is devoted to the development of an accurate method for determining the frequencies and vibration modes of a resonator of a vibration-frequency sensor by applying an exact simplification of the basic equations of resonant oscillations of a resonator taking into account the rigidity (compliance) of the supports and their location. The deviation of the parameters of the geometry of the resonator from the ideal and the heterogeneity of the material of the resonator affect the metrological characteristics of the vibration frequency sensor. However, existing technologies do not provide the possibility of manufacturing resonators with nominal parameters. The existing numerous algorithms for calculating the frequencies and waveforms of resonators are used to estimate the fundamental frequency of an oscillating system that do not take into account the dynamic characteristics. The accuracy of the oscillation frequency of the resonator depends on the choice of the mode of oscillations, which is sometimes difficult to predict in advance.
 Practical tasks require performing design work with the required accuracy. The lack of an accurate method for determining the frequencies and modes of vibration of the resonator of the vibration-frequency sensor, which would take into account the type of mounting and location of resistance, designers have to adapt existing approaches and calculation models to specific measurement conditions. Therefore, in practice, simplified and approximate methods of calculation are used. In the presence of concentrated masses and in the case of taking into account energy dissipation in the places where the resonator is fixed, the calculation methods become more laborious. In some cases, the possibility of a mathematical interpretation of a task becomes feasible only if some simplifications are introduced into the calculation.

CST: A new semi-empirical tool for simulating spacecraft collisions in orbit

This paper provides a general description of a new Collision Simulation Tool (CST) to model the consequences of orbital impacts involving large debris and satellites, with the aim to predict fragments distributions in case of sub-catastrophic and catastrophic impacts. The new tool is being developed in the framework of the ESA contract “Numerical simulations for spacecraft catastrophic disruption analysis”, carried out by the Center of Studies and Activities for Space CISAS “G. Colombo” of the University of Padova (prime contractor) and etamax space GmbH.The CST makes possible to model a large variety of collision scenarios involving complex systems, such as entire satellites with many design details included, and provides statistically accurate results with a computational effort orders of magnitude lower than hydrocodes. To this end, the simulation approach is based on a hybrid modelling strategy, in which every colliding object is described as a gross net of Macroscopic Elements (ME) representing spacecraft elementary building blocks. On one hand, individual fragmentation of Macroscopic Elements is addressed through the use of semi-empirical breakup models applied, at element level, only to those spacecraft parts which are involved in the collision. On the other hand, structural distortion, fracture, and separation of satellite broken parts are modelled with a discrete-element approach through the simulation of momentum transfer to Macroscopic Elements through the net, taking into account energy dissipation inside elements and across links.This paper provides a description of the CST simulation methodology and framework; preliminary results are also shown with respect to the tool validation process. Validation is done by comparing the tool predictions with empirical data from ground-based impact tests on simple targets (simple plates and Whipple Shields) as well as sub-scale spacecraft models. In the first case, the tool capability of predicting fragments distributions from plates and ballistic limit equations of shields is verified. In the second case, fragments distributions calculated by the software are compared with those derived from published experiments on a micro-satellite.

Intensification of thermal and rheological processes in a scraped-surface apparatus

The operation parameters of a special heat exchange scraped-surface apparatus ware studied and mathematically described in the article. The feature of the apparatus was the use of perforated cleaning devices in order to increase the turbulence of a product. The developed device can be used in the dairy, meat, and fat and oil industry to cool cream, animal fats, margarine emulsions, cooking fats, and other viscous food products. The increase in the productivity of the apparatus was achieved as a result of the more intensive mixing of the cleaned wall layers with the bulk of the cooled product due to the presence of cylindrical holes in the slats with a diameter of at least 
 0.05–0.1 of the diameter of the working cylinder. As a result of processing experimental data on heat exchange taking into account energy dissipation, a calculated criterial heat exchange equation for the nonisothermal motion of products and their different flows – laminar and transient – was obtained explicitly. In addition, the article considers the effect of starting modes on the operation of apparatus with mixing devices. These data can make it possible to take into account the possible deviations of parameters caused by nonsteady operating modes. On the basis of the data obtained, we have proposed assumptions about the degree of impact of viscosity and inertia in the considered range of parameters on a starting mode. The results of the study are relevant since they allow us to intensify the thermal processes in this type of common apparatus by 10–12%.

Analog–Digital Quantum Simulation of the Dicke Model with Superconducting Circuits

We propose a concept of mixed analog–digital quantum simulation of the Dicke model with ensembles of superconducting qubits coupled to the single-mode microwave resonators. Using both single-qubit and twoqubit quantum logic gates, it should be possible to engineer different initial conditions for the ensemble of qubits. Since qubits can interact through the photon field of a common quantum resonator, it is attractive to examine the time evolution of this system depending on various characteristics of the initial state, including entanglement and symmetry. We here study theoretically the dynamics of such systems taking into account energy dissipation, pure decoherence as well as disorder in qubits excitation frequencies, which are unavoidable for macroscopic artificial quantum systems. We reveal unusual effects of these imperfections on the dynamics.