Steady Mode Research Articles

Poly(2,5-dimethoxyaniline) coated polystyrene microspheres and their electrorheological characteristics

We synthesized core–shell type spherical semiconducting poly(2,5-dimethoxyaniline) (PDMA)-coated polystyrene (PS) (PS/PDMA) particles with uniform size and investigated their electrorheological (ER) response. Using monodisperse PS microspheres initially synthesized by dispersion polymerization, 2,5-dimethoxyaniline monomer was pre-adsorbed onto the PS surface via π–π stacking interaction, and then PDMA was synthesized by oxidative polymerization. Morphology of the synthesized PS/PDMA particles was observed by both scanning electron microscopy and transmission electron microscopy, while their chemical compound was confirmed by Fourier transform infrared spectroscopy. The PS/PDMA microspheres were suspended in silicone oil and their ER properties were studied using a rotational rheometer from both steady shear and oscillatory test modes. Flow curves were observed to be fitted well with the Bingham fluid equation, while all three differently measured yield stresses showed similar electric field dependence. Furthermore, dielectric analysis confirmed the degree of relaxation time and polarizability related to the ER behaviors of the PS/PDMA particle-based ER fluid. PS/PDMA particles with several advantages such as easy conductivity control through a doping and a de-doping process, their spherical shape and controllable size are expected to be of great help in their multiple applications in both ER fluids and colloidal science.

Density peaks clustering‐based steady/transition mode identification and monitoring of multimode processes

AbstractMultimode is the characteristic of industrial manufacturing processes due to different production strategies and environments. For multimode process monitoring, it is a challenge to identify different steady modes and transition modes. In this paper, a k nearest neighbours (KNN)‐based density peaks clustering (DPC) method is applied to identify different modes. First, the local density of each sample, which is obtained with a KNN constraint and its minimum distance to the higher local density points are calculated as two indicators of the DPC algorithm to find the cluster centres of the training data. Then, the transition modes are identified by combining the moving window strategy and the DPC algorithm, where an index called the local density‐distance ratio (LDDR) is employed. Finally, the monitoring algorithm is used to detect the faults for each operation mode. The effectiveness and advantages of the proposed method are illustrated by a numerical example and a Tennessee Eastman (TE) benchmark process.

Temporal secondary stability simulation of Rayleigh-Bénard-Poiseuille flow

The onset of primary and secondary instability has important implications for Rayleigh-Bénard-Poiseuille flows. This paper demonstrates that the primary and secondary instability can be investigated with temporal simulations based on the full and linearized Navier-Stokes equations. Three cases with subcritical Reynolds number and supercritical Rayleigh number are discussed. It is shown that the secondary instability results from a triad interaction of the fundamental steady three-dimensional mode with a two-dimensional and two oblique modes. As the disturbances grow to non-linear amplitudes, the longitudinal rolls exhibit a sinusoidal wavy deformation. The wavelength of the most amplified secondary instability wave is in good agreement with experimental observations. The phase speed of the waves is close to the basic flow bulk velocity as suggested in the literature.

MODELLING OF DYNAMIC MODES OF AN INDUCTION ELECTRIC DRIVE AT PERIODIC LOAD

Goal. Development of methods and mathematical models, based on them, for the calculation of transients and steady-state modes of induction electric drives operating in periodic load mode. Methodology. The developed algorithms are based on a mathematical model of an induction motor, which takes into account the saturation of the magnetic core and the displacement of current in the rotor bars. The processes are described by a system of nonlinear differential equations in the orthogonal axes x, y, which enables the results to be obtained with the smallest amount of calculations. The magnetization characteristics by the main magnetic flux and the leakage fluxes are used to calculate the electromagnetic parameters of the motor. To account for the current displacement in the rotor bars, the short-circuited winding is considered as a multilayer structure formed by dividing the bars in height by several elements. Results. Due to the variable load on the motor shaft, electromagnetic processes in both transient and steady state modes of the electric drive in any coordinate system are described by a system of nonlinear differential equations. The result of the calculation of the transients is obtained as a result of their integration time dependencies of coordinates (currents, electromagnetic torque, etc.) at a given law of change of the moment of loading. The proposed method of calculating steady-state mode is based on algebraization of differential equations on the mesh of nodes of the process cyclicity period and allows to obtain periodic dependencies in the time domain. Originality. The problem of calculating a steady-state periodic mode is solved as a boundary problem for a system of first-order differential equations with periodic boundary conditions, which allows to obtain instantaneous dependences during the period of currents, electromagnetic torque, capacities and other coordinates. Practical significance. Using the developed algorithm, it is possible to calculate the static characteristics of periodic processes as dependencies on different parameters of the cycle of periodic load or other coordinates, which is the basis for the choice of the motor for overload, power, heating, etc., as well as to detect the possibility of resonance.

Modelling of Dynamic Modes of An Induction Electric Drive at Periodic Load

Goal: Development of methods and mathematical models, based on them, for the calculation of transients and steady-state modes of induction electric drives operating in periodic load mode. Methodology: The developed algorithms are based on a mathematical model of an induction motor, which takes into account the saturation of the magnetic core and the displacement of current in the rotor bars. The processes are described by a system of nonlinear differential equations in the orthogonal axes x, y, which enables the results to be obtained with the smallest amount of calculations. The magnetization characteristics by the main magnetic flux and the leakage fluxes are used to calculate the electromagnetic parameters of the motor. To account for the current displacement in the rotor bars, the short-circuited winding is considered as a multilayer structure formed by dividing the bars in height by several elements. Results: Due to the variable load on the motor shaft, electromagnetic processes in both transient and steady state modes of the electric drive in any coordinate system are described by a system of nonlinear differential equations. The result of the calculation of the transients is obtained as a result of their integration time dependencies of coordinates (currents, electromagnetic torque, etc.) at a given law of change of the moment of loading. The proposed method of calculating steady-state mode is based on algebraization of differential equations on the mesh of nodes of the process cyclicity period and allows to obtain periodic dependencies in the time domain. Originality: The problem of calculating a steady-state periodic mode is solved as a boundary problem for a system of first-order differential equations with periodic boundary conditions, which allows to obtain instantaneous dependences during the period of currents, electromagnetic torque, capacities and other coordinates. Practical significance: Using the developed algorithm, it is possible to calculate the static characteristics of periodic processes as dependencies on different parameters of the cycle of periodic load or other coordinates, which is the basis for the choice of the motor for overload, power, heating, etc., as well as to detect the possibility of resonance.

Using High-Frequency Pulsed Supersonic Microjets to Control Resonant High-Speed Cavity Flows

A novel actuator concept is evaluated in a series of active flow control experiments on a resonant high-speed cavity flow. The actuator generates pulsed supersonic microjets by using the resonance of an impinging microjet source, and with smart materials incorporated into its design, the actuator’s resonant frequency can be actively controlled. The actuator was designed such that its resonant frequency would lie within the range of predicted cavity resonance. Results from Mach 1.5 flow over a cavity of length are presented, and the actuator’s performance is evaluated across three modes of operation: pulsed, active pulsed, and steady. In the active pulsed mode, the smart materials are used to actively vary the actuator’s resonant frequency, enabling frequency modulation of the actuator’s output. When the actuator operates in both pulsed modes, the amplitude of the dominant peak in the cavity’s unsteady pressure spectra is reduced by as much as 7 dB. However, steady microjet injection yields more effective control. The dominant peak is substantially attenuated (by 25 dB) in this mode of operation. The effectiveness of the steady mode is attributed to higher momentum flux that can be attained in contrast to the pulsed modes of operation.

Fluid–structure stability analyses and nonlinear dynamics of flexible splitter plates interacting with a circular cylinder flow

The dynamics of a hyperelastic splitter plate interacting with the laminar wake flow of a circular cylinder is investigated numerically at a Reynolds number of 80. By decreasing the plate’s stiffness, four regimes of flow-induced vibrations are identified: two regimes of periodic oscillation about a symmetric position, separated by a regime of periodic oscillation about asymmetric positions, and finally a regime of quasi-periodic oscillation occurring at very low stiffness and characterized by two fundamental (high and low) frequencies. A linear fully coupled fluid–solid analysis is then performed and reveals the destabilization of a steady symmetry-breaking mode, two high-frequency unsteady modes and one low-frequency unsteady mode, when varying the plate’s stiffness. These unstable eigenmodes explain the emergence of the nonlinear self-sustained oscillating states and provide a good prediction of the oscillation frequencies. A comparison with nonlinear calculations is provided to show the limits of the linear approach. Finally, two simplified analyses, based on the quiescent-fluid or quasi-static assumption, are proposed to further identify the linear mechanisms at play in the destabilization of the fully coupled modes. The quasi-static static analysis allows an understanding of the behaviour of the symmetry-breaking and low-frequency modes. The quiescent-fluid stability analysis provides a good prediction of the high-frequency vibrations, unlike the bending modes of the splitter plate in vacuum, as a result of the fluid added-mass correction. The emergence of the high-frequency periodic oscillations can thus be predicted based on a resonance condition between the frequencies of the hydrodynamic vortex-shedding mode and of the quiescent-fluid solid modes.

Novel dependencies of currents and voltages in power system steady state mode on regulable parameters of three-phase systems symmetrization

The unbalanced mode, negative/zero sequence, variation of real power are caused by the nonlinear or unbalanced loads increase the power transmission losses in distributing power systems and also harmful to the electric devices. Reactive power compensation is considered as the common methods for overcoming asymmetry. The critical issue in reactive power compensation is the optimal calculation of compensation values that is extremely difficult in complex circuits. We proposed a novel approach to overcome these difficulties by providing the creation of new analytical connections of the steady-state mode parameters (voltages, currents) depends on the controlled parameter for the arbitrary circuits. The base of our approach to reactive power compensation is the fractional-polynomial functions. We present a new description of the behavior of voltages and currents depending on the controlled parameters of the reactive power compensation devices, and we prove its effectiveness.

Optimization of the phase-change wallboard test method: Experimental and numerical investigation

Abstract The application of phase change materials (PCMs) within building envelopes has been a topic of significant research in recent years. Conventionally, determination of the thermophysical properties of PCM-containing wallboard is achieved using the differential scanning calorimetry (DSC) and guarded hot plates method. The thermophysical parameters (phase change temperature, specific heat (Cp), and enthalpy-temperature curves (H(t))), however, of PCM wallboard (PCMW) determined using different methods present certain deviations. This has a significant impact on the reliability of corresponding numerical simulation investigations (e.g., EnergyPlus). Taking this into consideration, this study compares the temperature-dependent specific heats - Cp(T) - from both the DSC and guarded hot plates methods (in dynamic mode, steady mode, and step mode) via experimental investigation. Numerical simulation (using FLUENT software) was then employed to deduce the optimal test parameters for the phase change wallboard test, applying the guarded hot plates method (including dynamic/linear mode, steady mode, and step mode). These parameters include the heating/cooling rate, PCM content, wallboard thickness, and recommended thermal stability time (RST). Key results show that, using the dynamic mode, the heating/cooling rate should be set to 0.5°C/min or less, while for the step mode, the RST function was established. The purpose of this study was to propose an optimal phase-change wallboard test mode, using the guarded hot plates method, to accurately measure the thermophysical properties of PCMs within a full-scale specimen.

RESULTS OF EXPERIMENTAL STUDIES OF ACCELERATIONS OF THE DM-617 VIBRATORY ROLLER USING DIGITAL SIGNAL PROCESSING TECHNOLOGY

Introduction. To improve the vibrating rollers in order to increase sealing capacity, reliability and vibration safety, the interaction of vibrating roller parts between each other and with compacted soil is simulated mathematically. The developed models are validated, i.e. compared with the results of experimental studies. However, the known results of experimental studies were obtained based on a relatively small list of vibrating roller models and soil types, as well as in a steady vibration mode. The paper presents the results of experimental studies, which used a vibratory drum of a roller to study its vertical vibration accelerations both in the steady vibration, as well as transient mode at turning the vibration generator on (speedup) and off (halt). This expands the range of opportunities to validate the existing and newly developed mathematical models.Materials and methods. Experimental studies of vertical vibration accelerations of a drum were conducted using the DM-617 vibrating roller when compacting natural sand-gravel aggregate. The accelerometer readings show high-frequency harmonics, which makes it significantly more difficult to determine amplitude values of vibration accelerations, therefore a low-frequency filter with a boundary frequency of 200 Hz was used for digital processing.Results. It was determined that when the DM-617 vibrating roller is compacting soil with maximum driving force within the range of variation of dynamic modulus of soil deformation Evd=14…25 MPа, amplitude values of vertical vibration accelerations of the vibratory drum are from 65... 77 to -61... -69 m/s2 . At the start-up (speedup) of vibration generator, acceleration amplitudes are 1.1 times higher than vertical accelerations of steady operation mode of the vibrating drum and practically do not depend on the dynamic modulus of soil deformation Evd. At turning off (stop) of the vibration generator, amplitude of vertical accelerations do not exceed the vertical accelerations of the steady operation mode of the vibratory drum.Discussion and conclusion. The vertical acceleration amplitudes of vibratory drums of DM-617 do not depend on the dynamic soil deformation modulus Evd, and this is consistent with the results of experimental studies of the vibratory drum mounted on DM-614. The obtained vertical vibration accelerations of the drum mounted on DM-617 in the steady vibration mode, as well as at switching the vibration generator on (speedup) and off (halt) make it possible to verify the existing and developed mathematical models of interaction of vibrating rollers with compacted soil.Financial transparency: the authors have no financial interest in the presented materials or methods. There is no conflict of interest.

Experimental research of vertical movements and accelerations of the drum vibrations of the DM-617 vibratory roller during soil compaction

Rheological modeling of how the elements of a vibratory roller during soil compaction interact with each other allows the optimization of parameters of the roller and soil compaction modes based on the study of the obtained model, as well as the improvement of the soil compaction continuous control system, and the solution of other practically important tasks. To verify the models, it is required to compare the calculation results for the models with experimental data. The paper includes the results of experimental studies of the acceleration range for the vibratory drum of the DM-617 vibratory roller during soil compaction in the steady vibration mode, when the vibration is turned on, and when it is turned off. It is established that during the compaction of the soil in question in the range Evd = 14…25 MPa, the range of vertical movements and accelerations of the vibratory drum in the steady vibration mode does not depend on the soil density. When the vibration is turned on, the vertical movements and accelerations of the drum is 1.5…2 times higher than those of the steady mode. When the vibration is turned off, the vertical movements are increased by 1.5…2 times when passing the resonance zone, and the drum accelerations do not exceed the range of those in the steady vibration mode. The obtained results allow the mathematical models of vibratory rollers during soil compaction to be verified not only in the steady vibration modes, but also in transient modes, including passing the resonance areas when switching the vibration on and off.

Effect of viscosity ratio on the dynamic response of droplet deformation under a steady electric field

The effect of the fluid viscosity ratio on the transient deformation of a droplet is investigated. A numerical model is developed by employing the phase field method to capture the interface. The model is validated in both steady and transient cases with literature data with good agreement. In the creeping flow regime, the droplet always undergoes monotonic deformation. When the viscosity of the suspending fluid dominates, the transient process of the droplet deformation is nearly independent of the viscosity ratio. When the viscosities of the droplet and suspending fluid are comparable, the damping effect of the droplet viscosity on the deformation is magnified and the time to reach the steady-state deformation increases with viscosity. When the effect of suspending fluid inertia prevails, the droplet will deform to the steady state either in a monotonic way or in an oscillating way depending on the viscosity ratio. A quasi-steady mode, which can be considered as an intermediate mode between the oscillating and the steady mode, is identified for the first time. When the droplet is in the quasi-steady mode, the increase in the electric capillary number can turn it into the steady mode. The flow field evolution is analyzed and it shows that the vortices inside the droplet play an important role in the transient deformation. The deformation process can be determined by the competition between the inner and outer vortices. It is found that the minimum deformation time can be obtained for the quasi-steady mode when the viscosity of the suspending fluid is low.

Experimental Evaluation of Thermal Protection Properties of Volume Textile Materials

In the article research results are presented, which aim to provide evaluation of thermal protection properties of volume textile materials. However, as a result of experts wearing it has been revealed that by their operational performance their characteristicsare quite high to such materials: Holofiber, Tinsulate, Arctic, etc. At the present time to research thermal protection properties of sewing materials methods are used that can be divided into 2 groups: Methods based on the principle of steady heat mode and Methods based on the principle of unsteady (regular) mode. New device has been developed which allows to simplify both the schematic diagram and the methodological approach to experimental evaluation of thermal protection properties of volume textile materials. The corresponding experimental research were held based on the developed bicalorimeter. Study results allowed to establish heat insulation material «ArcticP» possesses the highest thermal resistance.It is located with its metallized coating facing outside. High values of thermal protection properties of this material are explained by availability of metallized coating from outer side which ensures partial heat reflection.. The research was made in Don State Technical University within the framework of State Assignment of the Ministry of education and science of Russia under the project 11.9194.2017/БЧ.

Improving the algorithms for measuring sensor parameters to determine the moisture content of dry and liquid agricultural products

The article describes the result of algorithms studies for measuring sensor parameters to determine the moisture content of dry and liquid agricultural products. Measuring circuits are given and an algorithm for determining the moisture and impurities of agricultural products based on measuring the parameters of multi-element two-terminal devices in steady and transient modes is described in detail.

Experimental Analysis of the Kinematics of Motion of Floating Elements in Rotor Mechanisms

The kinematics of the motion of floating elements (ring) of rotor mechanisms under steady state rotation modes is examined experimentally. The ring is placed with a gap with respect to the drive cylindrical link and touches it without losing contact. It is shown that the ring motion is a direct asynchronous precession and its points circumscribe epitrochoids, if the driving motion is “lunar.”

Hydroelastic response of a circular sandwich plate interacting with a liquid layer

We considered the formulation and solution of the forced oscillations hydroelasticity problem for a three-layered circular plate contacting with a viscous incompressible fluid layer, the pressure in which varies according to the harmonic law. The plate is the bottom wall of a narrow channel completely filled with a viscous fluid. The axisymmetric coupled hydroelasticity problem consisting of the plate dynamics equation, the viscous fluid layer dynamics equation, and their corresponding boundary conditions was investigated. We obtained the plate dynamics equations taking into account inertia forces in the radial and normal directions in the framework of zigzag kinematic theory. In these equations, the load was expressed by the stresses of the viscous fluid contacting with the three-layered circular plate. The fluid dynamics equations were represented by the Navier-Stokes equations and continuity equation written for the case of creeping fluid flow in a channel. We obtained the forced radial and bending hydroelastic oscillations equations of the circular three-layered plate using the perturbation method. The solution of these equations was represented by a series of eigenfunctions of the corresponding Sturm-Liouville problem. We have also presented the numerical study results of the radial and bending vibrations amplitude dependence on the frequency for the main steady oscillations mode of the plate.

Дослідження режиму роботи верстата-гойдалки під час розгону

Розроблена математична модель свердловинної штангової насосної установки з балансирним приводом – верстатом-гойдалкою. Більшість свердловин Українських нафтових родовищ знаходяться на пізній стадії розробки, тобто їх дебіт нижчий ніж подача штангових насосів. Така робота верстатів-гойдалок приводить до зниження динамічного рівня рідини в свердловині, а отже й до зміни навантаження привода. Таким чином порушується усталений режим роботи. Коли рівень рідини досягає прийому глибинного штангового насоса, верстат-гойдалку відключають. На кривошипах верстата-гойдалки встановлено противаги, які зрівноважують навантаження, що діє в точці підвіски штанг. Зміна динамічного рівня призводить до порушення зрівноваження. Таким чином двигун привода перевантажується під час пуску верстата-качалки. Проведено аналітичне дослідження свердловинної штангової насосної установки під час її пуску.

Flow characteristics around airfoils near transonic buffet onset conditions

In transonic flow, buffet is a phenomenon of flow instability caused by shock wave/boundary layer interaction and flow separation. The phenomenon is common in transonic flow, and it has serious impact on the structural strength and fatigue life of aircraft. In this paper, three typical airfoils: the supercritical OAT15A, the high-speed symmetrical NACA64A010, and the thin, transonic/supersonic NACA64A204 are selected as the research objects. The flow fields of these airfoils under pre-buffet and buffet onset conditions are simulated by Unsteady Reynolds Averaged Navier-Stokes (URANS) method, and the mode analysis of numerical results is carried out by Dynamic Mode Decomposition (DMD). Qualitative and quantitative analysis of the shock wave motion, shock wave intensity, shock foot bubble and trailing edge separation, and pressure coefficient fluctuation were performed to attain deep insight of transonic buffet flow features of different airfoils near buffet onset conditions. The results of DMD analysis show that the energy proportion of the steady mode of these airfoils decreases dramatically when approaching the buffet onset angle of attack, while the growth rate of the primary mode increases inversely. It was found that at the onset of buffet, there exist different degrees of merging behavior between shock foot bubble and trailing edge separation during one buffet cycle, and the instability of shock wave and separation induced shear layer are closely related to the merging behavior.

Numerical Simulation of Drag Reduction on a Square Rod Detached with Two Control Rods at Various Gap Spacing via Lattice Boltzmann Method

Numerical simulations are performed to examine the effect of size of control rods (d1) and spacing ratio (g) on flow around a square rod with upstream and downstream control rods aligned in-line using the lattice Boltzmann method (LBM). The Reynolds number (Re) is fixed at Re = 160, while the spacing between the main rod and control rods is taken in the range 1 ≤ g ≤ 5 and the size of the control rod is varied between 4 and 20. Seven different types of flow mods are observed in this study at different values of g and d1. Variation in force statistics, like mean drag coefficient (Cdmean), Strouhal number (St), root mean square values of drag (Cdrms) and lift coefficients (Clrms), and percentage reduction in mean drag coefficient is discussed in detail. It was examined that vortex shedding completely suppressed at (g, d1) = (1, 12), (2, 12), and (2, 16) where steady flow mode exists. Moreover, it was found that at large gap spacing, where g = 5, the effect of control rods on the main rod vanishes. Due to this strong vortex shedding produced and as a result, maximum value of Cdmean is found at (g, d1) = (5, 8). The negative values of mean drag force are also observed at some gap spacing and size of control rods are due to the effect of thrust. Furthermore, the maximum percentage reduction in Cdmean is 121%, found at (g, d1) = (2, 20).

Aspects Determining the Dominance of Fomitopsis pinicola in the Colonization of Deadwood and the Role of the Pathogenicity Factor Oxalate

Carbon and mineral cycling in sustainable forest systems depends on a microbiome of basidiomycetes, ascomycetes, litter-degrading saprobes, ectomycorrhizal, and mycoparasitic fungi that constitute a deadwood degrading consortium. The brown rot basidiomycete Fomitopsis pinicola (Swartz: Fr.) P. Karsten (Fp), as an oxalate-producing facultative pathogen, is an early colonizer of wounded trees and fresh deadwood. It replaces basidiomycetous white rot fungi and non-basidiomycetous fungal phyla in the presence of its volatilome, but poorly in its absence. With the goal of determining its dominance over the most competitive basidiomycetes and its role in fungal successions within the forest microbiome in general, Fp was exposed to the white rot fungus Kuehneromyces mutabilis (Schaeff.: Fr.) Singer & Smith (Km) in aseptic dual culture established on fertilized 100 mm-long wood dust columns in glass tubes with the inclusion of their volatilomes. For the mycelia approaching from the opposite ends of the wood dust columns, the energy-generating systems of laccase and manganese peroxidase (MnP), the virulence factor oxalate, and the exhalation of terpenes were determined by spectrophotometry, High Pressure Liquid Chromatography (HPLC), and Gas Chromatography-Mass Spectrometry (GC-MS). Km mycelia perceived the approaching Fp over 20 mm of non-colonized wood dust, reduced the laccase activity to 25%, and raised MnP to 275%–500% by gaining energy and presumably by controlling oxalate, H2O2, and the dropping substrate pH caused by Fp. On mycelial contact, Km stopped Fp, secured its substrate sector with 4 mm of an impermeable barrier region during an eruption of antimicrobial bisabolenes, and dropped from the invasion mode of substrate colonization into the steady state mode of low metabolic and defensive activity. The approaching Fp raised the oxalate production throughout to >20 g kg−1 to inactivate laccase and caused, with pH 1.4–1.7, lethal conditions in its substrate sector whose physiological effects on Km could be reproduced with acidity conditions incited by HCl. After a mean lag phase of 11 days, Fp persisting in a state of high metabolic activity overgrew and digested the debilitated Km thallus and terminated the production of oxalate. It is concluded that the factors contributing to the competitive advantage of F. pinicola in the colonization of wounded trees and pre-infected deadwood are the drastic long-term acidification of the timber substrate, its own insensitivity to extremely low pH conditions, its efficient control of the volatile mono- and sesquiterpenes of timber and microbial origin, and the action of a undefined blend of terpenes and allelopathic substances.