Inertia Coefficients Research Articles

Couple stress Darcy–Forchheimer nanofluid flow by a stretchable surface with nonuniform heat source and suction/injection effects

The thermal enhancement of industrial and engineering processes with interaction of nanofluids is exclusively important and presents applications in extrusion systems, heat transfer devices, electronic chips, chemical reactions, nuclear processes, etc. Owing to such motivated significance of nanofluids, the aim of this investigation is to present the heat and mass transfer phenomenon in the Couple stress nanofluid flow containing the microorganism due to oscillatory stretched surface. Additionally, the Darcy–Forchheimer applications, nonuniform heat source and nonlinear thermal radiation effects are considered. The modification in the concentration equation is done by activation energy. The independent variables in the defined flow system are decreased via suitable variables. The computation is simulated using the homotopy analysis method. It is noticed that the magnitude of velocity periodically decreases for larger values of suction parameter and inertia coefficient. The presence of an external heat source parameter enhanced the temperature profile. Moreover, the increment in the suction parameter improves the heat and mass transfer rate.

Особенности методики проведения экспериментальных исследований системы адаптивного управления судовых грузоподъемных устройств

Lowering and recovery operations, as well as towing underwater and surface objects are carried out with the help of a ship winch. As a result of the impact of any external disturbances, longitudinal oscillations appear in the towing rope, whose resonant maxima may fall into the vessel’s frequency range. The longer the cable, the greater the number of resonant frequencies in the operating range. Such operating conditions of the ship’s lifting equipment have a negative impact on the operation of the ship’s power plant as a whole. In order to increase the reliability of deck lifting equipment it is proposed to use an adaptive control system that would respond in a timely manner to changes in loading. Lifting equipment of a fishing vessel with non-stationarity of dynamic processes in operation is considered as an application of such a system. There is considered a principle of operation of the adaptive hydraulic drive of a trawl winch. The important scientific and technical problem of developing a complex mathematical model of the above control system has been solved. The directions of experimental research are determined. There is proposed a laboratory unit to evaluate the influence of the parameters of a mechanical system on the dynamics of a hydraulic drive of a load-lifting device adaptive to load variability. The unit operates due to changing the number and weight of the load discs installed on the driving and driven pulleys and simulating a change in the inertial coefficient, which is typical for a trawl winch. The second direction of experimental research is the verification of the adequacy of the obtained mathematical models. There are presented the results of the verification in the form of calculated and averaged experimental dynamometer cards, which are well correlated, with deviation up to 8%.

Statistical Modelling for the Darcy–Forchheimer Flow of Casson Cobalt Ferrite-Water/Ethylene Glycol Nanofluid under Nonlinear Radiation

Current research is focused on the utilization of a numerical solution of Casson cobalt ferrite nanofluid flow by taking two forms of base fluid. This investigation includes the gradual influence of nonlinear thermal radiation on the improvement of heat transfer related to the flow of nanofluids over a stretched rotating surface by the Darcy–Forchheimer law. The model constructed by a Casson nanoliquid in the boundary layer’s flow is studied for its symmetric behaviour, including cobalt ferrite nanomaterials. Two base liquids named as ethylene glycol and water are considered. The rate of heat transport is examined by considering Newtonian heating conditions. By utilizing similarity transformations, a partial differential system that governs the said model has been transformed into a highly nonlinear ordinary differential system, and numerical outcomes are obtained by implementing the RK4 via shooting methodologies. All obtained results, including local skin friction coefficients and local Nusselt number, are defined and discussed in the paper. The study’s findings ensure that the Casson cobalt ferrite nanofluid flowing towards a stretching plate has a unique solution: A variation of the solid volume fraction corresponds to the decrease in various values of the Casson nanofluid parameter for both type of nanofluid. Furthermore, a similar behaviour is noted for various values of the solid volume fraction, which corresponds to various values of the inertia coefficient parameter. Moreover, for the highest values of the solid volume fraction and all values of R1 and Ni taken into account, the rate of heat transfer upsurges. The data from the local skin friction coefficient (LSFC) and local Nusselt number (LNN) have been analysed using various statistical distributions, and it has been determined that both datasets generally fit the exponentiated Weibull distribution for various values of considered parameters. The findings would serve as a starting point for the manufacture of devices.

Constitutive modelling of non-cohesive soils under high-strain rates: a consistency approach

Rapid loading of sands is a common issue in geotechnical engineering problems such as projectile or free-fall impact. At high strain rates (HSR), soils show more strength and enhanced dilation (viscoplastic behaviour) compared to the response at low rates (inviscid behaviour). However, few constitutive models account for the viscoplasticity of sands. Hence, the development of viscoplastic models is highly desired. Usually, viscoplasticity is modelled using overstress methods. However, overstress methods impose an overall modification of the constitutive equations, which prevents control of the evolution of internal state variables and the enforcement of the consistency condition. In this study, a generalised consistency–viscoplasticity method is proposed and applied to a non-associative modified Mohr–Coulomb model with coupled stress–dilation relation. The influence of strain rate is incorporated using a work–energy approach by way of an inertial coefficient. Two explicit integration strategies are proposed and compared, and guidelines for their implementation are shared. The numerical response of the model is tested by using drained triaxial simulations under constant axial strain rate, relaxation and impact loading. The results indicate that the consistency–viscoplasticity is a feasible alternative to simulate soil behaviour under HSR, capturing reasonably well the observed experimental responses.

Mayfly Sparrow Search Hybrid Algorithm for RFID Network Planning

The radio frequency identification (RFID) technology is frequently used for large-scale RFID network planning, which brings thought-provoking RFID network planning (RNP) problems such as the uncertain number of readers, high interference rate of readers, poor economic benefits, and weak robustness. In this paper, we propose a mayfly sparrow search hybrid algorithm with Circle chaotic map and Lévy flight, which is named MASSA. MASSA maps out the position of the readers by adding the idea of the mayfly algorithm (MA) into the optimization process of the sparrow search algorithm (SSA). Circle chaos mapping and Lévy flight are added in the SSA optimization process and the nonlinear inertia coefficients to balance the relationship between global search and local search. The MASSA is compared with SSA, Improved sparrow search algorithm (ISSA), MA, particle swarm optimization algorithm (PSO), and gray wolf algorithm (GWO). The first part of the experiment uses the CEC2017 test suite to evaluate algorithm performance and analysis strategy effectiveness. The results encourage the application of MASSA to solve RNP problems. In the second part, experiments were conducted with four objective functions of coverage, interference, power, and load balance. Two different experiments were carried out with fixed number of readers and flexible number of readers under random label conditions. Experimental results show that MASSA has good planning performance, better economy, and robustness.

Effective Inertia Coefficients Prediction and Cell Size Effects in Thickness Direction of Periodic Composite Plates

This paper develops a new homogenization method for free vibration problems of periodic composite plates. In this new method, three-dimensional (3D) periodic plates are equivalent to Reissner–Mindlin plates with both effective stiffnesses and effective inertia coefficients. The effective stiffnesses for the dynamic problems are the same as those for the static problems, and they can be achieved by the equivalence principle of macro- and microscopic internal virtual work. To fully take the inertia effects into account, the effective inertia coefficients including the effective translational, translational–rotational and rotational inertias are determined by the two-scale equivalence principle of kinetic energies under three rigid modes. In addition, cell size effects in the thickness direction of composite plates are investigated by using the proposed method and the asymptotic homogenization method (AHM). Numerical experiments validate the effectiveness of the proposed equivalent method for different scale factors, and show that the rotational inertia cannot be ignored for out-of-plane deformations, especially for higher-order modes. Besides, numerical comparisons show that the cell size effects are not negligible when using the AHM to analyze the out-of-plane deformations, and three or more repeated unit cells in the thickness direction are required to ensure accuracy.

Experimental and numerical studies for parameters identification of direct current motor

<p><span>Direct current (DC) motors are widely used in many applications especially those require a speed control, direction and closed-loop control system. In electric vehicle drive system, DC motor is commonly used for the propulsion of low power (<250 W) electric bicycle (e-bike) because it can operate directly from rechargeable batteries with a smart controller. In driving an e-bike in a closed loop control system, it is important to identify and estimate the dynamic of electrical and mechanical parameters. In this paper, the parameters such as armature resistance, armature inductance, back emf constant, torque constant, moment of inertia and viscous friction coefficient are ideally identified using dynamic responses experiments and tests focusing on no load motor and transient input tests. The motor is then modeled in MATLAB/Simulink using the identified motor parameters and its open loop speed and current responses are studied.</span></p>

Universality Class of Ising Critical States with Long-Range Losses.

We show that spatial resolved dissipation can act on d-dimensional spin systems in the Ising universality class by qualitatively modifying the nature of their critical points. We consider power-law decaying spin losses with a Lindbladian spectrum closing at small momenta as ∝q^{α}, with α a positive tunable exponent directly related to the power-law decay of the spatial profile of losses at long distances, 1/r^{(α+d)}. This yields a class of soft modes asymptotically decoupled from dissipation at small momenta, which are responsible for the emergence of a critical scaling regime ascribable to the nonunitary counterpart of the universality class of long-range interacting Ising models. For α<1 we find a nonequilibrium critical point ruled by a dynamical field theory described by a Langevin model with coexisting inertial (∼∂_{t}^{2}) and frictional (∼∂_{t}) kinetic coefficients, and driven by a gapless Markovian noise with variance ∝q^{α} at small momenta. This effective field theory is beyond the Halperin-Hohenberg description of dynamical criticality, and its critical exponents differ from their unitary long-range counterparts. Our Letter lays out perspectives for a revision of universality in driven open systems by employing dark states tailored by programmable dissipation.

Periodic Flow Through Regenerator Fillers Made from Packed Spherical Microparticles

Periodic flow of gases at cryogenic temperatures through microporous structures occur in the regenerators of Stirling-type cryocoolers. For computational fluid dynamics simulation of such flows using the Darcy–Brinkman–Forchheimer model, permeability and inertial coefficients are needed. Experimental pore-level characterization of such regenerators is difficult due to their microporous structure, and the occurrence of near-zero instantaneous flow rates and extraction of these parameters from experimental data can involve significant uncertainty. In this work, by three-dimensional direct simulation, the hydrodynamic parameters are found for flow through a metallic fill powder common to some recent cryocooler regenerators that operate at very low temperatures. The intrinsic permeability and the Forchheimer coefficients are found for parameter ranges of interest to pulse-tube cryocoolers and are compared with reported extracted experimental values. The permeability and Forchheimer coefficients are correlated to be suitable for application in computational fluid dynamics codes.

Numerical Investigations about Flow Resistance Values for Stirling Type Pulse Tube Cryocooler

Pulse tube cryocoolers are extensively used for space application because of simplicity and reliability in operation. Many researchers have attempted the numerical analysis of the oscillatory flow inside the cryocooler, however, the precise predictions of the exact behavior of the gas inside the cryocooler using CFD has not yet been reported. While performing the CFD analysis of cryocooler, the values of inertial and viscous resistance coefficients play vital role and highly contributes to the pressure drop taking place in porous media. The prime objective of present work is to analyze the effect of these resistance values on performance of cryocooler. A single stage Stirling type pulse tube cryocooler model from literature is employed to perform the CFD analysis and the results obtained from the analysis are validated to ensure that methodology used for analysis is correct. The resistance values mentioned in the literature are applicable for steady and unidirectional flows. The model is further modified for the values of resistances for oscillating flow at room temperature and oscillating flow at cryogenic temperature. It is observed that performance predictions for oscillating flow at cryogenic temperature resistance values yields substantially lower temperature than all other cases. As experimental validation of this model is still not reported in literature, the reliability of accurate resistance values is not confirmed. Hence, another model of single stage Stirling type pulse tube cryocooler from literature is numerically analyzed for various operating conditions and is compared with its experimental performance, and found to be in fair agreement.

Robot Path Planning Based on an Improved Salp Swarm Algorithm

This paper demonstrates an improved version of the Salp Swarm Algorithm (SSA) to solve the problems of slow convergence and local minima of the original version. In the population initialization of this scheme, ten chaotic searches with dynamic inertia coefficients are introduced to increase the diversity so that the probability of being trapped in local minima is reduced. Genetic algorithms are then applied to improve the global search ability and convergence speed. The experiments with 12 test functions show that the improved version achieves better accuracy and convergence speed over the original SSA. In the test with robot path planning problem, the proposed algorithm shows improved performance in the average number of iterations, path length, and average number of turns by 69.2%, 19.1%, and 43%, respectively, compared with the original SSA.

Magnetohydrodynamic Effects on Third-Grade Fluid Flow and Heat Transfer with Darcy–Forchheimer Law over an Inclined Exponentially Stretching Sheet Embedded in a Porous Medium

The major aim of the current investigations is to study the magnetohydrodynamic effects on heat and mass transfer phenomena in third-grade fluid past an inclined exponentially stretching sheet fixed in a porous medium with Darcy–Forchheimer law influence. The constitutive equations compatible for heat and mass transportation in third-grade fluid in terms of partial differential equations are modeled. These partial differential equations are then converted to ordinary differential equations by using suitable similarity variables formulation. The transformed flow model is solved by using MATLAB built-in numerical solver bvp4c. Effects of pertinent parameters on physical properties that are velocity field, temperature field and mass concentration along with skin friction coefficient, Nusselt number and Sherwood number are demonstrated in graphs and tables. The impact of dimensionless numbers on the physical properties is analyzed and discussed with a physical view point at angle α=π/6 (inclined sheet). It is seen that as the third-grade fluid parameter (0.1≤β≤11) is increased, the velocity profile increases, but the temperature field and mass concentration are decreased. It is observed that as the permeability parameter (1≤K*≤11) is raised, the velocity distribution decreases and mass concentration increases. It is concluded from the results that owing to an increase in the local inertial coefficient (0.1≤Fr≤5), the velocity profile reduces but an increment in mass concentration is noted. It is concluded that by increasing values of magnetic field parameter (0.1≤M≤10) the velocity field is delineated and temperature field is elevated exactly according to the physics of magnetic field parameters. The present results are compared with already published results and it is observed that there is good agreement between them. This good agreement ensures the validation of accuracy of the results.

Dynamic Resource Allocation and Forecast of Snow Tourism Demand Based on Multiobjective Optimization Algorithm.

This paper aims to map the task of reliable transmission of wireless sensor networks. At the same time, this paper transforms the mapping problem of wireless sensor networks into a problem of reducing the energy consumption of mapping under many constraints such as reliability and scheduling length and uses discrete particle swarm optimization algorithm to map. For optimization, the algorithm performs iterative calculations to obtain the best mapping node for each operation so that the inertia coefficient of the existing particle swarm optimization algorithm is improved and linearly minimized with the number of iterations. When resource-demanding tasks need to allocate dynamic resources to multiple nodes to complete collaboratively, adding the mapping principle of the nearest node in the discrete particle swarm optimization mapping reduces the energy consumption of communication between tasks. An in-depth analysis of the influencing factors of the ice and snow tourism market shows that the per capita disposable income of urban residents and the number of urban residents have a significant impact on the ice and snow tourism market demand. In addition, regression analysis and demand-based forecasting are important methods to analyze the scale and development trend of tourism. At the same time, it shows an important position in the purpose of urban tourism and regional market share so as to provide a basis for decision-making in tourism destination marketing. This paper mainly studies and analyzes the wireless sensor network and further introduces it into dynamic resource allocation and ice and snow tourism, which can promote the continuous development of dynamic resource allocation and ice and snow tourism.

An Experimental Study of Mangrove‐Induced Resistance on Water Waves Considering the Impacts of Typical Rhizophora Roots

AbstractThis paper studied the interactions between mangroves and water waves through laboratory experiments. Using 1:7 scale 3D‐printed trees based on the scanned image of a typical Rhizophora species, we replicated the root structure of natural mangroves and constructed a model forest. Three arrangements of mangrove models, two model forests of different stem densities and a single tree in isolation, were adopted. To investigate the relationships between mangrove resistance and waves, we applied the approach of direct force measurement, measuring wave forces on mangrove models, fluid velocity, and free surface elevation along the wave flume. Testing regular and solitary waves of various conditions, we observed non‐negligible inertia effects in the measured forces. Based on the direct measurements, we estimated drag and inertia coefficients in the Morison‐type equation (Morison et al., 1950, https://doi.org/10.2118/950149-g) and established empirical relationships between the two coefficients and Reynolds and Keulegan‐Carpenter numbers. These relationships of drag and inertia coefficients can be used in mathematical/numerical simulations to parameterize mangrove effects under similar scale conditions. Compared to previous studies, the drag coefficients for mangroves were more scattered than rigid cylinders, especially in shallower water depths. By testing different water depths, we observed different patterns of drag and inertia coefficients when the root system was partially or fully submerged. In addition, the fluctuating fluid velocity and enhanced turbulence kinetic energy at the vertical positions near prop roots indicated the blockage effects and the shear‐induced turbulence due to the complex root structure. These findings suggested the influence of mangrove roots on water waves.

Tsunami-Induced Drift Motion and Numerical Simulation Using Various Models

In this study, laboratory experiments were conducted to observe drifting of objects transported by a tsunami. Tsunami-induced drift motion was simulated using various numerical models, and the results were compared. Experiments were performed with and without obstacles in the terrain, and the differences were assessed. The spread of debris occurred faster in the presence of an obstacle. In the absence of structures in the flow, the debris did not shift perpendicular to the flow direction in any of the numerical models. The experimental results were generally consistent with the calculated results, although they varied in a normally distributed manner. However, when there was a downstream structure, the uncertainty of the drift motion was not accurately simulated. Furthermore, it was observed that debris moved behind obstacles. A numerical model that calculated the collision force between debris using momentum conservation reproduced this phenomenon. Thus, the numerical model with the drag and inertia coefficients was fairly accurate.

Multi-scale dispersive gradient elasticity model with rotation for the particulate composite

Research on the characteristics of composites material has received enormous interest in recent years. The multi-scale nature of composite material leads to employing advanced techniques. Moreover, the presence of a wave with the high-frequency source adds complexity to the analysis. In this paper, a novel multi-scale elasticity model was developed to predict the wave dispersion property of particulate composites. The methodology was based on the simultaneous participation of translational and rotational degrees of freedom in motion equations. The method scheme of gaining motion equations was accomplished by using Taylor's expansion as a continualization method. The framework of the motion equations and restrictions determined the layout of the lattice. The obtained lattice was a network of polydispersive particles in three-dimensional as a unit cell. The model proposed the inertia coefficient and dimension coefficient, which reflected the heterogeneity on the particulate composite. The theoretical results were then validated with experimental results. For this aim, concrete and mortar with the various classes of heterogeneity were nominated as a sample of particulate composite material. The nominated composites were prepared with different mixture schemes from geopolymer paste. The wave dispersion behavior of geopolymer specimens was established by measuring phase velocity in various frequencies. In addition to geopolymer products, experimental results from independent literature were scrutinized for concrete and mortar with cement binder. In the end, the capability of the presented parameters was indicated for realizing the state of concrete curing and features of the binder.

A Class of Unconditionally Stable Shooting Methods with Application to Radiative Darcy–Forchheimer Flow

Since there are shooting methods in the literature to solve ordinary differential equations (ODEs), those are mainly based on Runge–Kutta explicit methods. It is a proven fact that explicit Runge–Kutta methods are conditionally stable. The present contribution consists of constructing a class of shooting methods based on implicit methods that are unconditionally stable with their application to solving the problem of Darcy–Forchheimer’s flow over the stretching sheet under the influence of thermal radiations. Governing equations of the flow phenomena are presented in the form of partial differential equations (PDEs). Further, these PDEs are reduced into ODEs which are tackled by the present constructing shooting methods based on the class of Adam Moulton’s techniques with the Gauss–Siedel iterative method. The stability and convergence for the system of differential equations are also given. Thus, the main advantage of the presented methods is to turn the implicit methods into explicit methods using the shooting approach. Also, the impact of inertia coefficient, porosity parameter, radiation parameter, and Prandtl number on velocity and temperature profiles is given graphically. It is seen that the increment of the porosity parameter escalates the temperature profile. A computational code for the proposed model scheme may be made available to readers upon request for convenience.

Experimental Investigation of Wave-Induced Forces on a Large Quasi-Elliptical Cylinder during Extreme Events

Large quasi-elliptical cylinders are extensively used in ocean engineering. To enhance a better understanding of the hydrodynamic wave force on such quasi-elliptical cylinders during extreme events, a series of experiments on extreme wave interaction with a quasi-elliptical cylinder were conducted. A series of waves with various wave heights, wave periods, and wave incident directions were tested to investigate the wave parameter effect and wave directionality effect on the wave forces on the quasi-elliptical structure. The experimental results indicate that the extreme wave-induced forces on the quasi-elliptical cylinder are strongly correlated to the wave period and wave incident direction. The peak forces on the quasi-elliptical model do not vary monotonically with the increasing wave period but show an increase followed by a decrease. Both the longitudinal and transversal forces are significantly increased when the wave incident direction changes from 0° to 45° and the wave directionality effect is enhanced when the wave period is decreased. Additionally, the inertial force equation was applied to the wave force estimation for such quasi-elliptical cylinders, and the inertia coefficient CM was fitted based on the experimental results of α = 0°.

Computational Fluid Dynamics modelling of hydrodynamic characteristics of oscillatory flow past a square cylinder using the level set method

This paper presents a numerical study of the three-dimensional hydrodynamic characteristics of oscillatory flow past a square cylinder including the effect of the variation of blockage ratio and the Keulegan–Carpenter (KC) number on those characteristics. The oscillatory flow is simulated using an open-source Computational Fluid Dynamics (CFD) modelling tool REEF3D. The CFD model solves the Reynolds-Averaged Navier–Stokes (RANS) equations in all the three dimensions. The location of the free-surface is represented using the level-set method (LSM), which calculates the complex motion of the free-surface in a very realistic manner. For the implementation of the waves, the CFD code is used as a numerical wave tank. First, the model has been extensively validated against experimental measurements present in the literature. Thereafter, further analysis is carried out using the CFD code to study the effect of blockage ratio on the hydrodynamic characteristics (drag coefficient, inertia coefficient, lift coefficient and coefficient of pressure) for different oscillatory flow regimes. To this effect KC numbers ranging between 3 and 13 (implying different flow regimes) have been selected for blockage ratios of 0.05, 0.0625, 0.1, 0.2, 0.3, 0.5 (for wall effect). The results indicate that the drag coefficient and the lift coefficient increases with the increase of blockage ratios for a particular KC number. Further, both these coefficients increases with the increase of KC number at a fixed blockage ratio. The coefficient of inertia, however, increases up to a blockage ratio of 0.2 and decreases thereafter for a particular KC number. The results also show that for a particular blockage ratio the coefficient of inertia decreases on escalating KC number and the coefficient of pressure increases for large blockage ratios at a fixed KC number on the upstream of the cylinder and reduces on the downstream side of the cylinder.

THE NEWEST TERRITORIAL SHIFTS IN THE GLOBAL OIL INDUSTRY: QUANTITATIVE EVALUATION

This article is devoted to the quantitative evaluation of the newest changes in the global oil industry for the period from 2001 to 2020. The study of changes in territorial structures over time allows us to better understand the emerging trends in the industry and give more accurate forecasts of further development. The objects of the study are the sub-sectors - oil production and refining in two segments - the actual output and installed capacity of refineries. The author estimates territorial shifts based on the following indicators: V.M. Ryabtsev’s criterion and A.P. Gorkin’s coefficient of location inertia. In addition, a general overview of the changes in the role of individual states and macro-regions in the oil industry is presented. The results of the study indicate significant territorial shifts in all segments of the oil industry, despite its overall maturity.