Steady Mode Research Articles

Experimental and Model Study of a Swirling Fluid Flow in a Converging Channel As a Simulation of Blood Flow in the Heart and Aorta.

Study of swirling flows in channels corresponding to the static approximation of flow channels of the heart and major vessels with a longitudinal-radial profile zR2 = const and a concave streamlined surface at the beginning of the longitudinal coordinate has been carried out. A comparative analysis of the flow structure in channel configurations zRN = const, where N = -1, 1, 2, 3, in the absence and presence of a concave surface was carried out. The numerical modeling was compared with the results of hydrodynamic experiments on the flow characteristics and the shape of the flow lines. The numerical model was used to determine the velocity structure, viscous friction losses, and shear stresses. Numerical modeling of steady-state flows for channels without a concave surface showed that in the channel zR2 = const there is a stable vortex flow structure with the lowest viscous friction losses. The presence of a concave surface of sufficient size significantly reduces viscous friction losses and shear stresses in both the steady state and pulsed modes.

Research on the dynamics of transitional regimes in an inertial screen with two motor vibrators

Purpose. Analysis of mathematical models of vibrating screens, using the theory of oscillations and mathematical modeling to study the impact of initial start-up parameters and the dynamics of transient processes on the operation of the screen. Methodology. This research is dedicated to the analysis of mathematical models that describe the startup process and subsequent operation of a vibratory screen. Methods of oscillation theory, system dynamics, and mathematical modeling are applied to analyze the vibratory processes of screens. Special attention is given to studying the impact of initial startup parameters on the operation of the screen, including amplitude, frequency, and phase of oscillations. Within the framework of this work, detailed graphs are constructed that reflect the displacement of different points of the structure, as well as the trajectories of their movement during operation, using the Mathcad software. Results. Transitional modes of startup and steady operation are analyzed, with motion dynamics equations for both phases detailed. Displacement graphs for key screen points over time and changes in screen movement across operational modes are highlighted. Scientific novelty. The study defines a mathematical model for the motion of a screen with two motor-vibrators during startup and steady operation. It introduces a graph showing the screen points' displacement over time, from startup to steady mode, and illustrates the trajectories of these points under various operational modes. This research advances material classification techniques, enhancing process optimization and equipment efficiency. Practical significance. This research enhances vibratory material sorting by analyzing screen dynamics across operating modes, leading to optimized workflows, lower energy use, and improved sorting efficiency. It also bolsters equipment reliability and reduces the risk of failures, cutting down on maintenance and repair expenses.

Crashworthy optimization of skeleton-filled FRP tubes based on back propagation neural network

Lightweight composite tubes have been widely used in vehicle safety systems as energy absorbers. To improve the crashworthiness of tubes, composite skeletons with a variety of cross-sectional profiles were ingeniously designed as internal reinforcements. Herein, a novel composite skeleton comprising cross-ribs and an inner circle (OS-skeleton) was proposed and integrally fabricated through the special assembling molds. The novel OS-skeleton presented a steady progressive failure mode under dynamic impact loads, leading to remarkable material utilization and energy absorption characteristics. Subsequently, finite element analysis (FEA) models were developed. The predicted response curves and deformation modes were consistent with the experimental results. Finally, a multi-objective optimization utilizing the back propagation neural network (BPNN) was then conducted to further enhance the mean crushing force (MCF) and specific energy absorption (SEA) by adjusting several structural parameters. The results showed that MCF and SEA increased with the increasing thickness of the skeletons and the number of circumferential ribs. By comparison, the diameter of inner tube and the number of circumferential ribs showed a non-linear relationship with the energy absorption characteristics due to their combined effects. In sum, the proposed composite tubes filled with OS-skeletons could maximize certain aspects of crashworthiness performance through proper structural design, demonstrating great potential for lightweight energy absorbers.

Methods for Parametric Identifi cation of Systematic Errors of Onboard Measurements of Aerodynamic Angles in Aircraft Flight Tests

Methods of the actual values of the angles of attack and slip determination in the technology of air data systems estimation using satellite navigation systems during aircraft flight tests of are stated. Also methods of parametric identification of mathematical models of on-board aerodynamic angles measurements errors are presented. The technology has been developed and implemented in the practice of flight tests at Flight Research Institute. The technology shows high efficiency of solving tasks of air data on-board systems, vertical separation systems, flight performance and takeoff and landing characteristics estimation in flight tests. The technology covers a wide range of issues of aerometric measurements, many of which have already been published. Here, attention is paid to measurements of aerodynamic angles. The features of determining the angles of attack and slip using data from air data systems, satellite and inertial navigation systems are shown. Equations for determining the angles of attack and slip during testing, factors of measurement errors, the structure of the mathematical model of the aerodynamic errors of the angle of attack on-board measurements are presented in a stationary approximation. Algorithms for solving problems in steady and unsteady modes of flight, takeoff and landing are considered. The completeness of the solution for the wind speed vector is noted. Estimates of methodological errors in determining aerodynamic angles using the technology are made. Compliance with modern requirements is showing. The effectiveness of the technology is confirmed by the materials of flight tests of a short-range aircraft. Typical examples of test materials presentation, features of measurements depending on the type of test mode, aerodynamic influence factors are shown.

Разработка метода идентификации синхронного сопротивления турбогенератора и критериев выбора состава данных синхронизированных векторных измерений

To enhance power system dependability and efficiency, it is of great importance to obtain correct parameters of the models of key power system components such as a synchronous generator (SG). Technology of synchronized phasor measurements allows us to estimate the SG model parameters through measurements in power system steady states and transients states, without switching the SG off and conducting complex testing procedures. The theory of electric circuits and electric machines, theory of optimization and statistics, and matrix algebra are applied in this study. The developed parameter estimation method has been implemented in the MATLAB software. The method has been verified through real-world measurements captured by a phasor measurement unit installed at a large power plant in the United Power System. This paper presents an algorithm of the turbogenerator synchronous reactance estimation via a set of synchrophasor data taken under steady-state conditions. Also, the paper considers the criteria for an appropriate data array ensuring successful parameter estimation. An algorithm has been developed and implemented in MATLAB software package. To improve the parameter estimation accuracy, an algorithm has been proposed to modify a nominal value for the SG no-load excitation current depending on the heating of the field winding. The algorithm has been successfully tested out based on a set of steady state synchrophasor data captured for one of the turbogenerators in the Russian United Power System. The authors have developed and analyzed quantitative criteria to determine a set of measured parameters of steady-state modes, providing the most accurate results of the turbogenerator synchronous reactance. The developed algorithm allows accurate update of the turbogenerator synchronous parameters through synchrophasor measurements recorded in a steady state modes of electric power systems. Using the criteria for selecting phasor data, it seems possible to automate the process of generating a data array of measurement of various steady-state modes necessary for identification. The proposed procedure that considers the field winding temperature can be employed in math models to estimate SG transient and subtransient parameters based on phasor measurements in transient modes of electric power systems.

Servomotor Dataset: Modeling Health in Mechanisms with Typically Intermittent Operation

Servomotors are used in a variety of industrial applications where precise movements are of critical importance. Degradation mechanisms in servomotors have been mostly studied and modeled for systems with long duration steady state modes. However, some specialized applications require health estimation from very short duration intermittent operations, which require different analysis techniques. With such applications in mind, a simulated dataset for servomotor health modeling and prediction is described and made available for public use. The application scenario is motivated by a fine motion control rod drive (FMCRD) mechanism used for intermittent, and typically infrequent, fine motion (insertion or withdrawal) adjustment of control rods in some nuclear reactor designs. Though the drives do not run continuously, servomotor and associated linear motion mechanisms do show wear and damage during its operational lifetime. Specifically, in FMCRD such degradations may be caused by internal as well as external damage to the system. While the causes of such damage can be diverse, in simulation we model the impact of cumulative damage as an external opposing load which resists the movement of the motor shaft. Such scenarios represent effects of rod-binding and debris in the fuel channels. The dataset includes measurements such as motor currents and rotor speed which would be part of the instrumentation in a typical deployments of rotating machinery. These observable measurements can be used to predict the health state of the servomotor. Also presented are baseline results on health state estimation, formulated as classification and regression problems, which can be used by the larger PHM community for performance comparisons. This dataset is hosted at the PHM Society Data repository [https://data.phmsociety.org/servomotor_dataset/].

Interactions between oblique second mode and oblique waves in a high-speed boundary layer

Interactions between oblique second mode and oblique waves at a high-speed boundary at Mach 4.5 are studied using linear stability theory, nonlinear parabolized stability equations (NPSE) and direct numerical simulation (DNS). Parametric analysis based on the NPSE suggests that the oblique second mode can amplify both the oblique first and second modes, with the former experiencing a higher amplification. Our analysis reveals that the mean-flow distortion and difference mode contribute to this enhancement, with the latter exerting a key influence through the parametric resonance process. Kinetic energy transfer analysis demonstrates that the oblique waves gain energy from the mean flow, rather than from the oblique second mode. Furthermore, we find that the mechanism underlying the interaction between a pair of second oblique waves and a single oblique wave is similar to that between an oblique second mode and an oblique wave, as the steady modes generated by the pair of oblique second modes have a limited impact on the oblique wave. Finally, DNS confirms the validity of two transition paths proposed in this study based on the NPSE results. The first path suggests that a pair of low-amplitude second oblique waves alone are insufficient to cause oblique breakdown, but the introduction of a pair of low-amplitude damping first oblique modes could lead to boundary layer breakdown. The second path involves the formation of a domino-like effect through the combination of different types of oblique waves with the appropriate parameters. These two nonlinear paths can lead to a fully developed turbulent boundary layer.

Технология использования чернового концентрата в качестве минералов-носителей

Технология использования чернового концентрата в качестве минералов-носителей

Effect of Support Stiffness Nonlinearity on the Low-Frequency Vibro-Acoustic Characteristics for a Mechanical Equipment—Floating Raft—Underwater Cylindrical Shell Coupled System

The low-frequency vibro-acoustic characteristics of a mechanical equipment—floating raft—cylindrical shell—underwater acoustic field coupled system with nonlinear supports are studied in this paper. Firstly, the state space equations were established by a modal superposition theory for the coupled system, and a modal parameter identification method was deduced and verified for the cylindrical shell—underwater acoustic field coupled subsystem. On this basis, the formulas were derived for transmitted power flow in the coupled system, and the nonlinear stiffness constitutive relation of the vibration isolation supports was expressed by softening and hardening characteristics. Finally, dynamic simulations were carried out by the Runge—Kutta method to analyze the effect of nonlinear stiffness characteristic parameters on the low-frequency vibration modes and vibro-acoustic transfer characteristics in the coupled system. The research shows that a superharmonic phenomenon is common in the steady vibration mode of the coupled system with a nonlinear softening (or hardening) stiffness characteristic under harmonic excitation. The stronger the softening (or hardening) stiffness characteristic is, the more complex the vibration form is, and the smaller (or larger) the low-frequency vibro-acoustic transfer level in resonance regions is.

Формування математичної моделі турбовального двигуна

The subject of the study is the process of forming a mathematical model (MM) of a turboshaft gas turbine engine and a twin-engine helicopter power plant, which provides the determination of parameters of the working process in steady and transient operating modes for use in the estimation of dynamic characteristics, in the analysis and synthesis of engine and helicopter automatic control systems. The goal is to substantiate the structure and methodology of MM formation intended for use in real and accelerated time scale systems. Tasks: implementation of the previously proposed MM structure taking into account the turboshaft engine performances, development of a methodology for determining the MM coefficients based on known information about the static and dynamic properties of the engine, and formation of the MM structure of a two-engine helicopter power plant. For this, the methods of the theory of airjet engines and the theory of linear dynamic systems are used. The following results were obtained: the structure of a multimode high-speed MM of a turboshaft engine and a two-engine power plant was formed and tested. The scientific and practical novelty of the obtained results is as follows: the structure of the multimode linearized MM of the turboshaft engine is formed, which consists of static and dynamic submodels implemented in corrected parameters; the modeling technique was worked out on a simplified model, compiled considering expert information about the static and dynamic properties of the engine in the considered operation area. Formulas were obtained that relate the coefficients of the linear dynamic model to the values of the time constants of the rotors and the sensitivities obtained from the static characteristics; transient characteristics of the engine based on changes in fuel consumption and load power are determined, which correspond to physical knowledge about the engine; the modeling methodology and MM structure of a two-engine power plant were formed, which is distinguished by the combination of individual static and linear dynamic models of two engines with a single nonlinear dynamic model of the helicopter rotor; a simplified MM load necessary for testing the MM of the engine installation is proposed, which provides the calculation of the power consumed by the rotor, depending on the angular position of the blades.

Experimental study on physical characteristics of dielectric-boosted gliding arc discharge

To augment the plasma processing capability, and obtain an enhanced plasma area, a dielectric-boosted gliding arc discharge (DBGAD) reactor was developed. The electrical, gliding arc motion and energy injection characteristics of the DBGAD reactor were investigated. The process of AC DBGAD includes breakdown gliding mode (B-G) and steady arc gliding mode (A-G), with peak currents on the order of amperes in B-G mode and on the order of milliamps in A-G mode. Situating a 50 mm quartz dielectric underneath the plasma area at a distance of 10 mm from the base of the blade electrodes, enhanced discharge power is obtained, and sustained arc gliding time is extended efficiently. At an input voltage of 9.2 kV, the DBGAD demonstrates a 27% increase in arc stabilization gliding time compared to the gliding arc discharge (GAD) and delivers an average discharge power 1.12 times superior to that of the GAD. In the DBGAD reactor, the plasma column twists following the minor vortex of the reflow and has a more pleated shape. The energy injection characteristics are analyzed using the fast Fourier transform system, and the results show that the current harmonic content of DBGAD is reduced and the discharge fluctuation is mitigated, which is favorable for stable discharge. The primary benefit of incorporating quartz dielectric is that it provides the mobile arc with a supportive force, leading to a more substantial and intensely focused plasma field. This in turn facilitates greater system stability and yields measurable enhancements in power output.

Multi-aspect prediction of the sensitivity of thermodynamic/thermoeconomic performance metrics of an innovative solar-driven trigeneration system utilizing thermal energy storage

Clean energy development for multiple productions interests many countries and companies. Hence, this paper presents an innovative solar-driven trigeneration arrangement equipped with a thermal energy storage unit (TESU); the whole system comprises parabolic dish collectors, a modified Rankine cycle, and a double-effect absorption chiller. The system is designed to enhance the integrity performance compared to previous designs. Heat loss recovery is performed using an internal heat exchanger to improve the Rankine cycle's performance. The operating framework of the arrangement contains three steady modes: solar mode associated with the state without applying TESU, storage mode corresponding to the state without solar energy using TESU, and solar-storage mode capable of storing energy in addition to launching the combined cycles. The prediction of the sensitivity of the net output power, heating capacity, input energy, power to heating and cooling ratios, and energy and exergy efficiencies is conducted in solar mode. Furthermore, the thermoeconomic analysis is carried out in solar mode to determine the equipment's financial aspect. Referring to the results, the overall energy efficiencies of the modes introduced before are equal to 97.23%, 81.98%, and 40.23%, and the corresponding exergy efficiencies are 15.53%, 14.47%, and 8.58%. Also, the exergoeconomic factor of the solar subsystem is 70.77%.

The light source of the TRIDENT pathfinder experiment

In September 2021, a site scouting mission known as the TRIDENT pathfinder experiment (TRIDENT EXplorer, T-REX for short) was conducted in the South China Sea with the goal of envisaging a next-generation multi-cubic-kilometer neutrino telescope. One of the main tasks is to measure the in-situ optical properties of seawater at depths between 2800 m and 3500 m, where the neutrino telescope will be instrumented. To achieve this, we have developed a light emitter module equipped with a clock synchronization system to serve as the light source, which could be operated in pulsing and steady modes. Two light receiver modules housing both photomultiplier tubes (PMTs) and cameras are employed to detect the photons emitted by the light source. This paper presents the instrumentation of the light source in T-REX, including its design, calibration, and performance.

Flow Control in Serpentine Inlet Duct Using Vortex Generator Jets

The objective of the present research is to study the effectiveness of steady and pulsed vortex generator jets in reducing inlet flow distortion and in improving pressure recovery by effective secondary flow control in uniform inflow serpentine duct diffuser. The measurements were carried out at a test Reynolds number of 6.5 x 105 based on the diffuser inlet width. Serpentine duct diffuser consisted of two main portions, namely, a square to circular constant area transition duct followed by a circular diffusing duct. Investigations show that the flow in the serpentine diffusing duct suffers from stall on the inner wall and consequently the outflow at AIP has considerable flow distortion due to the combined effect of secondary flow and the inner wall stall. It is observed that the use of vortex generator jets, both in steady and pulsed modes, improve the performance substantially. The number of jets, location of jets, velocity ratios and the pulse frequency are some of the variables that are studied. The results obtained so far suggest that use of pulsed jet not only gives better performance but also reduces the amount of air that is needed to be injected through the jets in comparison to steady jets for similar velocity ratios.

A fast tunable driver of light source for the TRIDENT Pathfinder experiment

TRIDENT (The tRopIcal DEep-sea Neutrino Telescope) is a proposed next-generation neutrino telescope to be constructed in the South China Sea. In September 2021, the TRIDENT Pathfinder experiment (TRIDENT EXplorer, T-REX for short) was conducted to evaluate the in-situ optical properties of seawater. The T-REX experiment deployed three digital optical modules at a depth of 3420 meters, including a light emitter module (LEM) and two light receiver modules (LRMs) equipped with photomultiplier tubes (PMTs) and cameras to detect light signals. The LEM emits light in pulsing and steady modes. It features a fast tunable driver to activate light-emitting diodes (LEDs) that emit nanosecond-width light pulses with tunable intensity. The PMTs in the LRM receive single photo-electron (SPE) signals with an average photon number of approximately 0.3 per 1-microsecond time window, which is used to measure the arrival time distribution of the SPE signals. The fast tunable driver can be remotely controlled in real-time by the data acquisition system onboard the research vessel, allowing for convenient adjustments to the driver's parameters and facilitating the acquisition of high-quality experimental data. This paper describes the requirements, design scheme, and test results of the fast tunable driver, highlighting its successful implementation in the T-REX experiment and its potential for future deep-sea experiments.

Material stability criteria for a plane stress asymptotic solution for steady mode I crack growth in an elastic/perfectly plastic solid

Material stability criteria for a plane stress asymptotic solution for steady mode I crack growth in an elastic/perfectly plastic solid

Investigation of influence of local cooling/heating on nonlinear instability of high-speed boundary layer with direct numerical simulations

The influence of local cooling/heating on two types of nonlinear instabilities of the high-speed boundary layer, namely, the First and Second Mode Oblique Breakdown (FMOB and SMOB), is studied using direct numerical simulations. Local cooling and heating are performed at the weak and strong nonlinear stages of the two types of nonlinear instabilities. It is found that for the FMOB, local cooling at the weak nonlinear region will suppress the increase of the fundamental mode, leading to transition delay. Opposite to local cooling, local heating at the weak nonlinear region of the FMOB will promote the growth of the fundamental mode, resulting in the occurrence of more upstream transition onset. However, if local cooling and heating are performed at the strong nonlinear region, the influence of both local cooling and heating on the FMOB can be neglected. Remarkably, both local heating and cooling can delay the SMOB for different mechanisms. Performing local cooling at the weak nonlinear region of the SMOB, the low amplitude of higher spanwise wavenumber steady mode caused by local cooling lies behind transition delay. When local cooling is set at the strong nonlinear region, the low amplitude of harmonic modes around the cooling area can cause transition delay. Additionally, local heating will suppress the SMOB for the slowing amplification rate of various modes caused by the local heating at both the weak and strong nonlinear stages of the SMOB.

Integrating spheroid-on-a-chip with tubeless rocker platform: A high-throughput biological screening platform.

Spheroid-on-a-chip platforms are emerging as a promising in-vitro model that enables screening of the efficacy of biologically active ingredients. Generally, the supply of liquids to spheroids occurs in the steady flow mode with the use of syringe pumps; however, the utilization of tubing and connections, especially for multiplexing and high-throughput screening applications, makes spheroid-on-a-chip platforms labour- and cost-intensive. Gravity-induced flow using rocker platforms overcomes these challenges. Here, we develop a robust gravity-driven technique to culture arrays of cancer cell spheroids and dermal fibroblast spheroids in a high-throughput manner using a rocker platform. We benchmark the efficiency of the developed rocker-based platform to syringe pumps for generating multicellular spheroids and their use for screening biologically active ingredients. We study cell viability, internal spheroid structure, as well as the effect of vitamin C on the production of collagen type I and fibronectin by dermal fibroblast spheroids. We demonstrate that the rocker-based platform not only offers comparable or enhanced performance in terms of cell viability, spheroids formation, and protein production by dermal fibroblast spheroids but also, from a practical perspective it offers a smaller footprint, requires a lower cost, and offers an easier method for handling. These results support the application of rocker-based microfluidic spheroid-on-a-chip platforms for in-vitro screening in a high-throughput manner with industrial scaling-up opportunities. This article is protected by copyright. All rights reserved.

Cooperation search algorithm for optimal parameters identification of SOFCs feeding electric vehicle at steady and dynamic modes

In this work, the new application of cooperation search algorithm (CSA) is addressed to extract the unknown solid oxide fuel cell (SOFC)'s parameters supported by investigating and testing the cell steady-state and dynamic performances. Primarily, the indefinite SOFC's parameters are estimated utilizing CSA and the results are assessed and verified with compulsory comparisons. The minimum errors are obtained, CSA convergence behavior and SOFC's performance are all compared with other recognized algorithms in the literature. At last, and for more validations, the dynamic behavior of the SOFCs is studied when supplying electric vehicle (EV) operated with four DC motors at different speeds. The SOFCs and EV are represented via Simulink/MATLAB package. The EV's input current, voltage, power, and torque are traced at various acceleration and speed according to the road nature and/or driver requirements. The extensive investigations and validations prove the high efficacy of CSA capabilities in representing the SOFCs and for analyzing their steady-state and dynamic behaviors.

Natural extract-polymer monodisperse submicron particles from Plateau-Rayleigh microjets

Particles of interest in food, pharmaceutical, and nutraceutical sectors are often formulated with a polymer and one or more natural or synthetic active compound. The two components frequently have distinct hydrophilicity. Submicrometric particles with narrow size dispersion can be made by the droplet-to-particle route by electrospray. In the steady cone-jet mode a liquid Taylor cone (TC) continuously emits a Plateau-Rayleigh microjet which breaks up spontaneously and periodically into tiny droplets, which later dry up to form solid particles. To achieve a stable process of this kind, we argue that it is necessary to: (i) operate near the minimum solution flow rate compatible with TC stability, (ii) prevent the drying of the TC by surrounding it with a gentle gas stream saturated in solvent vapor, and (iii) monitor the electric current and image the TC. We demonstrate this process in the preparation of curcumin (CUR) loaded polyvinylpyrrolidone (PVP) submicrometric particles as a function of solution composition and ambient relative humidity. In the atomization step (jet and droplet formation), the initial droplet size and charge are determined by the liquid properties and flow rate. The particles’ shapes were spherical (with or without internal voids), corrugated due to shell buckling (with compact interiors), and filamented due to Coulombic instabilities, depending on the interplay of different factors at the droplet drying step. These included the droplet size and charge, solvent evaporation, solute diffusion, water uptake from the ambient, mechanical forces, and solution thermodynamics. The electric current and droplet size are suitably predicted by scaling laws developed for simple Newtonian fluids. Hence, our particle sizes lie always between the predicted droplet and compact-sphere sizes, at a distance which depends on the particle morphology. CUR-loaded PVP quasi-monodisperse submicron particles could be an interesting model for drug delivery and biomedical applications.