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Current industrial demands require the improvement of existing technologies and the creation of new ones that allow the production of parts and structures with advanced performance properties. Especially important is the issue of design and analysis of thermomechanical treatment of metals and alloys by intensive inelastic deformation methods. During these processes, significant structural changes occur at the meso- and microscale, which directly affect the working characteristics of the products. Particular attention should be paid to the study of the forming and use of miniature parts, which are increasingly in demand in various technical devices. An effective approach to describe these processes is to use multilevel models of crystal plasticity. Despite the tendency to miniaturize products, the parameters of such models are usually determined from the results of experiments on macrosamples. The question arises whether such parameters are valid for the analysis and modeling of real structures with typical length scales below 500 µm, where the internal and external boundaries of crystallites play a special role. In this study, the influence of the free surface on the mechanical properties of single crystalline and polycrystalline materials is considered. Modification of the basic direct crystal plasticity model of elastoviscoplasticity to account for the softening of slip systems near free boundaries due to easier exit of dislocations to the surface is proposed. [ABSTRACT FROM AUTHOR]

The previously developed numerical method for solving three-dimensional problems of dynamic interaction of deformable bodies and media in Euler variables based on the Godunov scheme of increased accuracy is used to solve problems of impact interaction of elastoplastic bodies. Improving the accuracy of the scheme is achieved by changing the "predictor" step. A three-dimensional and time-dependent solution of the elastic problem of discontinuity decay is applied, which provides the second order of approximation in time and space in the region of smooth solutions. Monotonicity in the region of discontinuous solutions is ensured by passing to the "predictor" step of the scheme of the first order of accuracy. A multigrid approach is used with three types of computational grids for each body with an explicit Lagrangian selection of moving free and contact surfaces. The first type of grids used is a Lagrangian surface grid in the form of a continuous set of triangles (STL file), which is used both to set the initial geometry of a liquid and a solid body and to accompany it during the calculation, and two types of 3D volumetric grids. These are a basic Cartesian fixed grid for each body, the number of cells of which can change, and auxiliary movable local Euler-Lagrangian grids associated with each triangle of the surface grid. The results of solving test and applied three-dimensional problems with large displacements and deformations are presented, demonstrating the possibilities of the numerical method. The processes of oblique impact, penetration and penetration of elastic-plastic barriers by deformable projectiles are considered. Numerical results demonstrate good performance of numerical models and techniques and are consistent with experimental data. [ABSTRACT FROM AUTHOR]

Sewage flow dissipating energy manholes play influencing role in reducing flow velocity with minimizing manhole erosion and gas emission. The current study is focusing on determining the discharge coefficient value for a side spillway rectangular weir situated longitudinally in a sewage dissipating energy manhole. The manhole receives pressurized flow through incoming force main and discharges water under gravity through outgoing pipe. The direction of flow alters 90 degrees two times within the manhole; after entering the manhole within inlet submerged channel, and before exiting the manhole within outlet channel. Between those alterations flow passes over the weir. Flow conditions was simulated using Computational Fluid Dynamics (CFD). Using the volume of fluid method (VOF), the free surface flow over the weir was modelled to track flow characteristics at subcritical flow conditions. Five different cases for weir length and three different cases for weir height were considered. The value of the coefficient was found to range from 0.32 to 0.57. It increases as the length of the weir decreased. [ABSTRACT FROM AUTHOR]

Photovoltaic Panel (PV) is one of the widely technologies that conversion the solar energy into direct – current (DC) in the present time. However, increase of panel temperature has a bad effect on the PV outcomes and major obstacle in widespread use, especially in the hot – dry climate. In this study, propose a new arrangement for accelerates the air-cooler motion behind the PV panel surface has introduced and investigated experimentally. Several containers of the air slot channels had fabricated and covered the back surface of PV panel. The test occurred in spring and summer season under varies outside environment climate conditions in terms of solar radiation and ambient temperatures. The investigation conducted in the city of Baghdad; it has longitude 44o and latitude 33o with a PV Panel angle of inclination 30o to the south. The experimental result appeared that, covered the free back surface of PV panel by slot platform helps to controller the panel temperature and maintain distribution of inlet air-cooling to cover PV back surface Panel as more orderly. The test showed that maximum PV panel performance achievement when enter the air-cooling from three direction and the slot platform have an air guided design as a nozzle shape. [ABSTRACT FROM AUTHOR]

The problem of studying the processes of wave propagation in an inhomogeneous continuous medium, as well as the impact of waves on moving and stationary marine objects, is modern and relevant. Internal waves, unlike surface waves, can have a much larger amplitude and carry more energy. The complex topography of the bottom surface can change the wave process. In the presented study, particular cases of solving the problem of the impact of the bottom surface on the stability of the wave process are considered. [ABSTRACT FROM AUTHOR]

Mechanical recycling is an essential tool in transitioning the plastics industry to a circular economy. The traditional route requires pelletizing after extrusion with melt filtration and degassing of the material. These (re)granulated materials can be later processed via injection molding. We present a study of a machine concept, which can be used to directly convert grinded or agglomerated thermoplastic materials to injection-molded products using a two-stage process. The machine concept consists of an extruder, a melt filter and an injection unit. To reduce odor and volatile organic contaminations, which are often present in post-consumer and sometimes also in post-industrial waste, a degassing system is introduced for the injection unit. Our study covers (i) virgin polypropylene with a humidity carrier and varying amount of water, (ii) grinded polyethylene from post-consumer caps, (iii) polypropylene agglomerate from post-consumer sheets, (iv) pre-sorted polypropylene flakes from post-consumer waste and (v) commercially available pellets from post-consumer PE/PP mixtures. Process stability and plasticizing performance is investigated under different boundary conditions. Effective degassing is achieved by increasing the free surface of the melt in the first section of the injection screw. Voids and closed pores are further reduced if vacuum is used. Mechanical testing shows an increasing tensile modulus of the injection-molded parts due to the reduction of volatile contaminations. The comparison to a state-of-the-art compounding process shows similar results. The machine concept represents an advanced opportunity to increase the content of recycled thermoplastics in injection molding including melt filtration and degassing, which would be very limited in a standard injection molding process. [ABSTRACT FROM AUTHOR]

Proper mixing of highly viscous, non-Newtonian, multicomponent fluids is complex but essential in industries such as food, catalyst production, and medical device manufacturing. Continuous mixing offers advantages such as more homogeneous products and reduced processing time and energy consumption. One common method for continuous mixing is the use of an extruder. In this study, a computational fluid dynamics model is developed to simulate the mixing of highly viscous, non-Newtonian, multicomponent fluids in a starved-fed single-screw extruder. The material behavior is described using the Herschel-Bulkley model, and the free surface of the material is captured by the volume of fluid method. The mixing performance is evaluated through two parameters: dispersive and distributive mixing. Dispersive mixing is assessed using the well-known Manas-Zloczower mixing index λMZ, while distributive mixing is evaluated through the Kramer mixing index. The more filled extruder yields better results in dispersive mixing, while distributive mixing is more easily achieved with lower percent fill length. [ABSTRACT FROM AUTHOR]

A side weir is a weir placed in the side wall of a channel. There are several functions performed by side weirs, including raising water levels for irrigation and drainage and diverting excess flow from rivers or channels during floods, which can help address major problems during the rainy season. In this study, side weir discharge coefficients in trapezoidal labyrinths of different side wall angles (15°, 30°, 45°, 60°, and 75°) and a linear side weir (90°) placed in the side wall of a rectangular channel was calculated in the laboratory. A hydraulic design and analysis approach for side weirs was first developed using experimental data from six physical models, and the locations in which these models were installed in the side wall of the straight channel and the discharge coefficient for each model were calculated by establishing the relationship between the discharge entering the main channel and the value of the head above each weir. Five values were taken from the discharge for five values from the head above the side weir, allowing the development of several equations in addition to the identification of the relationships through which the discharge coefficient was calculated. In addition, CFD software using a K-omega-SST turbulence model was used to simulate the side weirs, with the volume of fluid (VOF) scheme used to simulate changes in flow at the free surface. As a result, the CFD model was able to effectively predict changes in free surface flow, with results that demonstrate that the discharge coefficient Cd rises as the side wall angle increases and falls as the side wall angle decreases. This means that a trapezoidal labyrinth side weir with a side wall angle of 75° has a discharge coefficient greater than that of the other investigated weirs, and that the discharge coefficient increases as the shape approaches the shape of a straight weir. Significant agreement between the data from the lab and the simulations was also observed. [ABSTRACT FROM AUTHOR]

The widely use of petroleum-derived mineral oils for the production of offset printing inks has resulted in several environmental impacts. The suitable approach to develop alternative resources is palm oil fatty acid methyl ester (FAME) as a substitute for petroleum-based solvent. This study aimed to investigate the surface properties of palm oil-based offset ink on gloss-coated paper surfaces in terms of printability. The "green" varnishes were prepared with palm oil FAME as solvent, rosin-modified phenolic resin, and different vegetable oils linseed oil (FAME-LO) and soybean oil (FAME-SO) have been used as drying oils. The FAME-based Cyan offset printing inks have been prepared their properties compared with standard conventional inks. Printing tests were carried out using the IGT-A2 printability tester. Contact angles of water, methanol, and hexane on the surface of printed ink were measured using Contact Angle Analyzer. The surface free energy (SFE) and its components were calculated using Girifalco-Good-Fowkes-Young, Owens-Wendt, and van Oss-Chaudhury-Good methods. The results showed that as the liquid contact angle increased, the surface energy decreased. The surface energy of FAME-SO ink printed samples 36.36 mJ/m2 was higher than the unprinted paper 35.84 mJ/m2. Since high surface energy will affect the bond strength of the ink to the substrate, this will be an advantage for multicolor prints requiring good ink adhesion, which will enlarge the acceptance of other colors to be printed on the previous color. [ABSTRACT FROM AUTHOR]

A detailed reaction mechanism of the inhibition process of substrate N3 for the main protease produced by the coronavirus has been clarified using the QM(CDRK)/MM approach. Minimum free energy path optimizations were performed using the free energy gradient and nudged elastic band methods. The free energy profile includes three reaction steps: one bond formation and two proton transfers. The highest free energy barrier was 16.3 kcal/mol for the final proton transfer from His40 to the N3 molecule. Free energy contribution analysis was performed to identify important residues consisting of Mpro. Arg40, Arg188, and Glu166 were identified around the active site to increase the reaction profile at the free energy barrier. [ABSTRACT FROM AUTHOR]

In this paper, an experimental and analytical model of abrasive wear is proposed, based on the energy theory of wear, which makes it possible to predict the wear resistance of conjugated heterophase surfaces operating in a free abrasive medium. [ABSTRACT FROM AUTHOR]

In the introduction, the current situation is considered with the calculation of the weight-bearing flow and the task of the study is set. Considering the laws of non-pressure movement of water, the main equations of motion are considered, and to consider the specifics of the non-pressure flow of wastewater, the influence on the solution of these equations of motion of wave structural formations on the free surface and on the surface of bottom sediments is considered. In the third section, based on the experience of operating sewerage networks, the occurrence of waves on the free surface and ridges formed on the surface of sediments is considered, taking into account the changing geometry of the flow. Equations for the boundary conditions on the free surface are proposed, which reflect the motion of wave structural formations. The interaction of fluid motion with a moving layer is described, based on considering the developing non- stationary turbulent fluctuations of the velocity and pressure field. The last section presents the main conclusions of the work. [ABSTRACT FROM AUTHOR]

The review utilized different procedures to find out about the most recent desalination advances. Sun-powered energy is a significant wellspring of elective energy, particularly in districts like Iraq that get a great deal of daylight. Water desalination frameworks depend on conventional energy which is hurtful to the climate and human well-being since it comes about because of consuming petroleum products. Instructions to fulfill the rising need for new water, which is turning out to be progressively hard to get because of urbanization and populace development, is the issue confronting human culture. Sun-based stills are the most prudent method for delivering new water since they just sudden spike in demand for the energy of the sun, which is promptly accessible in nature. The essential disadvantage of ordinary sun-powered gatherers is that they can't hold a lot of water on a surface with a shallow water profundity. To work on the usefulness and proficiency of shifted sunlight-based still, a few endeavors have extended the free surface area of water. The scope of the greatest combined efficiency is 2.4 L and the most elevated limit is 10 L, this distinction in efficiency is because of a portion of the variables influencing the presentation of the working framework, including the elements as follows: seasons of the trial, sun powered radiation, wind speed, mass stream rate, and the area of the experiment (6), The greatest efficiency around (0.478 l/m2 hr), and least efficiency around (0.117 l/m2 hr). [ABSTRACT FROM AUTHOR]

Al Adham dam is located 133 km northeast of Baghdad, was constructed on Al Adhaim River, and started to operate in 2000. It is a multipurpose dam used to flood control, power generation, and irrigation. Its storage capacity reaches 1.5 billion m3. The dam has an ogee spillway to control the flood flow with a length of 562 m, crest level of 131.5 m.a.m.s.l., and a maximum discharge of 1150 m3/s at its maximum flooding elevation of 143 m.a.m.s.l. This study investigates the spillway hydrodynamics and the performance of the stilling basin of Al Adhaim Dam by using numerical simulation models under the design conditions. FLUENT software was applied to simulate flow over a spillway. The free surface was simulated using the fluid volume, VOF, method. The SST k-ω turbulence model was selected to deal with turbulence. The study found that the spillway could carry the design discharge and the flood wave over the spillway. Negative pressure occurs at points along the stilling basin at the crest, the drops in elevation, and at the flip bucket due to high velocity. [ABSTRACT FROM AUTHOR]

Tsunamis are uncommon events compared to natural hazards. Population growth along the shorelines has increased the statistic of the number of victims affected by the tsunami disaster. In order to help people to be aware about the tsunami disasters, tsunami wave propagation must be predicted. This study proposes a one-dimensional coupled shallow water equation for predicting the tsunami wave propagation. The simulation of numerical modelling was conducted to predict the occurrence of tsunami wave propagation. In order to approximate the shallow water equation, the discretization process was conducted using a new semi-implicit method which is one of the methods in finite difference method. A problem regarding the free surface wave damping problem were used in validating the semi-implicit method. For the purposes of the simulation, the boundary condition and initial condition, the spatial steps and time steps as well as the approximation of shallow water equation were encoded. By comparing the simulation results with Park (2007), we found that the simulation of one-dimensional shallow water equation is successfully predicted the behaviour of the tsunami propagation near the coastline after the earthquake ground shaking occurred. [ABSTRACT FROM AUTHOR]

The study investigates the sloshing of a viscoelastic fluid described by the Oldroyd-B model in a partially filled rect-angular container, under horizontal excitations. The research is divided into two parts. In the first part, a mathematical model in the case of viscoelastic liquid is developed using the Oldroyd-B model. From the equations of movement, a variational equation of the problem was obtained. In the second part, a two-dimensional numerical method is carried out, using Comsol Multiphysics software. A series of numerical simulations for various viscoelastic liquids were conducted to study the behavior of the free surface profiles of the viscoelastic fluid under horizontal excitations, in connection with the viscosity and relaxation time. The effect of the viscosity and relaxation time parameters of the liquid on sloshing is analyzed and presented. Surface wave elevation is discussed by changing the pulsation of the periodic excitation. It is evident from the obtained results that the free surface elevation changes by changing the coefficient of viscosity and the relaxation time of the viscoelastic liquid. Significant free surface profiles decrease is observed in the case of liquids with an elevated coefficient of viscosity. The relaxation time coefficient has a considerable impact on the sloshing behavior of the viscoelastic liquid. [ABSTRACT FROM AUTHOR]

High-temperature melt spreading under a shallow water layer can lead to energetic interaction, known as the stratified steam explosion. One of the key uncertainties in the current understanding of this phenomenon is the mechanism for the formation of a premixed zone above the melt layer. It is known that the most energetic steam explosions occur when dispersed melt droplets are mixed with water in a certain proportion. There exists experimental evidence that high-temperature melt spreading is featured by intensive disturbances of the melt surface, visible as sporadic splashes to the height of about few centimeters. In this work, numerical simulations are performed on the interaction of a melt pool with water jets impinging on the free melt surface. Three phases are considered: melt, water, and vapor; the interfaces are modeled by the Volume of Fluid (VOF) method. Phase change is taken into account on the water-vapor interface. The problem is solved numerically in two- and three-dimensional framework. Firstly, impingement of a short-duration vertical water jet on the melt surface is studied, with the parametric analysis performed to establish the effect of the jet characteristics (mass, velocity, diameter) on the primary (due to development of a cavity on the melt surface) and secondary (central jet due to cavity collapse) splashes. Secondly, three-dimensional simulations are presented demonstrating the development of vapor film instability in an initially three-layered configuration (melt and water layers separated by a thin vapor film). Implication for the steam explosion problem is discussed. [ABSTRACT FROM AUTHOR]

The coupling of dynamic loading platforms with synchrotron light sources have enabled experiments examining void formation in optically opaque materials. Much like spallation in a solid, cavitation occurs when rarefaction waves collide within a liquid. The resulting deformation leads to a complex flow field with numerous voids. It has been suggested that compaction of such a structure may be a significant source of ejecta (i.e. shallow bubble collapse). Experiments imaging supported and unsupported shocks interacting with a free surface in shock melted Mg with synchrotron radiation are presented. The results are used to examine the structure of a cavitation plane that forms in the unsupported case and provide an estimate of the porosity within this region. [ABSTRACT FROM AUTHOR]

Small-scale gap tests are useful when comparing the sensitiveness of compositions where formulation parameters and manufacturing conditions are varied. Such gap tests are very economical in terms of quantity of material, time and effort. The current UK small-scale gap test uses a cylindrical Tetryl donor pellet (density 1500 kg/m3) 12.7 mm diameter and 12.7 mm long combined with a brass shim attenuator. The shape of the acceptor charge is optional, the cross section being either square (12.7 mm side) or circular (12.7 mm in diameter). The acceptor length is 25.4 mm. A 25-or 25.4-mm cube of mild steel is used as a witness block. It can accommodate any explosive with a critical diameter less than 12.7 mm. However, there are issues with the current test: Tetryl is no longer commonly available and the test explosive needs a detonation pressure sufficient to deform the witness block. In order to address these shortfalls, we have developed a new Modified Small-Scale Gap Test (MSSGT) that does not require a metal witness plate for test sentencing, instead additional instrumentation in the form of contact pins follow the shock in the explosive and determine whether it transits to detonation. Using this technique, it is also possible to observe the run distance to detonation for a given attenuator thickness. From a calibration of the gap test donor and attenuator system the shock pressure entering the explosive can be obtained. From knowledge of the shock pressure and the run distance a 'Pop Plot' can then be obtained for the test explosive. It has also been shown that it is possible to extract the unreacted Hugoniot of the test explosive by capturing the free surface velocity of a thin brass plate placed on the end of the charge using Photon Doppler Velocimetry (PDV) for a number of given input pressures. In this paper, we describe two variations of the gap test that differ in the diameter (20 and 25 mm) and the donor explosive as well as test results on an HMX/Viton (90:10) formulation and an RDX/Al/HTPB (64:20.5:15.5) composition. [ABSTRACT FROM AUTHOR]

The generation of laser ablation depth data in the ultrafast (100ps) time regime is important for the validation of radiation hydrodynamic codes in that time regime. We present a technique using data from a velocimetry diagnostic to determine the hot electron penetration depth into a metal sample. [ABSTRACT FROM AUTHOR]

The Shock Release Experiments (SRE) platform has been developed to investigate the off-Hugoniot release path of metals that are shocked to high pressure using plate impact on gas-guns. This simple and direct measurement provides a release isentrope of a shocked sample in a single experiment. The release path is determined by measuring the free surface velocity, along with shock velocity, of up to six witness materials of lower impedance. We present the details of the shock release platform, and an example of the release behavior captured with tantalum samples for shock pressures between 18-24.9 GPa. [ABSTRACT FROM AUTHOR]

The interaction of elongated cylindrical strikers made of tungsten alloy VNZh90 with a finite-thickness plate made of the D16T aluminum alloy is numerically modeled. The influence of the shape of the head of the striker on the process and the result of interaction is investigated. Interaction velocities ranging from 300 to 600 m/s and interaction angles from 0 to 75 degrees are considered. The behavior of the materials of the striker and barrier is described by an elastoplastic model. The limit value of the intensity of plastic deformations is used as a fracture criterion. Modeling is carried out in a three-dimensional statement using the finite element method using the author's algorithm and the EFES 2.0 software, which allows modeling the fragmentation of interacting bodies with the formation of new contact and free surfaces and erosion fracture of materials. The adequacy of the mathematical model and numerical algorithm is confirmed by the good agreement of experimental and numerical results. The interaction of the striker with the flat and conical shape of the head part with the barrier was investigated. The conditions under which the striker ricochets from the barrier were determined. [ABSTRACT FROM AUTHOR]

We performed molecular dynamics (MD) experiments to explore dry sliding friction at the nanoscale. We used the setup comprised of a spherical particle built up of 32,000 aluminum atoms, resting on a semi-space with a free surface, modelled by a stack of merged graphene layers. We utilized LAMMPS with the COMB3 many-body potentials for the inter-atomic interactions and Langevin thermostat which kept the system at 300 K. We varied the normal load on the particle and applied different tangential force, which caused the particle sliding. Based on the simulation data, we demonstrate that the friction force Ffr linearly depends on the sliding velocity ν, that is, Ffr=− γν, where γ is the friction coefficient. The observed dependence is in a sharp contrast with the macroscopic Amontons-Coulomb laws, which predict the velocity independence of sliding friction. We explain such a dependence by surface fluctuations of the thermal origin, which give rise to surface corrugation hindering sliding motion. This mechanism is similar to that of the viscous friction force exerted on a body moving in viscous fluid. [ABSTRACT FROM AUTHOR]

The responses of two models of heterogeneous medium to impact loading are compared, namely, the direct numerical simulation model and the additive mixture model. Verification of Ni and Ti material parameters in the simulation of spall in a homogeneous barrier is performed. The calculated free surface velocity for homogeneous plates corresponds to the experimental data with an accuracy of at least 10%. A simulation of the impact loading process of plates made of Nitinol based on mathematical models of heterogeneous materials has been performed. The additive mixture model more accurately reproduces the free surface velocity profiles than direct numerical simulations. Nevertheless, the deviation of numerical simulation results from experimental data does not exceed 10% for both models. A comparison of the results of the models' responses to impact loading has shown that it is acceptable to use both models in problems considering alloys as heterogeneous media. [ABSTRACT FROM AUTHOR]

This paper presents the results of a numerical simulation of the interaction of the effects of elongated cylindrical steel projectiles with concrete obstacles. Problems are solved numerically, by the finite element method, in a three-dimensional formulation within the framework of the phenomenological approach to solid mechanics using the original EFES software package. The behavior of the steel projectile material is described by an elastic model. The deformation, damage and cracking processes of concrete are studied using the JH-2 model, which can account for high strains, high strain rates and high pressures in the material. The calculation algorithm used takes into account the formation of discontinuities in the material and the fragmentation of the solids with the formation of new free surfaces. The study also addresses the influence of reinforcement on concrete damage and failure dynamics in certain structures. [ABSTRACT FROM AUTHOR]

This paper aims to present a numerical model to analyze liquid sloshing in a flexible tank subjected to an external excitation, with taking into account the effects of fluid–structure interaction (FSI). The sloshing response to the ground motion was reproduced using a Gabor Wavelet pulse. The time history of the free surface is analyzed for a rigid and a flexible tank cases. [ABSTRACT FROM AUTHOR]

The numerical investigation of flow over the models of hydraulic structures is an interesting method to estimate the flow parameters of a given geometry. It is a time-saving system and the most economical in terms of investigation cost and accuracy of results. The design and simulation of flow over various shapes of models are economic and reliable in numerical simulation. Twelve experiments were conducted on wide dam models with rounded edges of different lengths and heights. The experiments were carried out in a channel of dimensions (50 * 50) cm and length of 12 m. the same laboratory experiments were carried out using computational fluid dynamics for Flow 3D program. The free surface profile was determined and a pressure distribution profile was included which shows that the hydrostatic pressure over the broad crested weir and the highest pressure in the upstream region was the computational inferences in close agreement with the experimental data. Compared with the upstream depth, the highest relative error of upstream water depth (y1) was 3.07%. It also shows through experimental and numerical experiments the head over broad is inversely proportional to the height of the weir and positivly to the length of the weir. [ABSTRACT FROM AUTHOR]

Experimental study of the dissociation of Freon R-134a hydrate with an external air flow U0 was carried out. At U0 = 1.6 m/s, the non-uniformity of the temperature field increases on the powder surface. It is shown that the Freon hydrate dissociation rate decreases with time. The decrease in the dissociation rate is associated with a decrease in the free surface of the granules and the ingress of the powder into the region of self-preservation. The dissociation rate for U0 = 1.6 m/s is higher due to the increase in the heat transfer coefficient from the air flow. [ABSTRACT FROM AUTHOR]

In the paper numerical study results of polymer melt flow on the cable head channels have been presented. The distinctive feature of the present investigation is calculation of a free outflow zone at the flow exit from the cable head. In the work a mathematical model of the isothermal three-layer flow with regard to viscoelastic properties of the processed materials has been given. The ANSYS POLYFLOW software package was used to solve the problem. The Maxwell model describing the viscoelastic properties of the examined materials has been applied. The mathematical model of the flow process was based on the laws of conservation. Calculation results have been velocity, pressure and current functions fields, boundaries of the external free surface at the cable head outlet. Diagrams of changes in the insulation thickness for different sections of the sector are given. [ABSTRACT FROM AUTHOR]

This work show the analysys of a three different airfoil geometris, that shows the turbine design and how important are this for the existent technologies. The imporante of cavitation and other physics phenomes it's a critical point on blade design, this mean that its necessary create many profiles and operation conditions, like free surface separation, blade high, cavitation and the influence of the diffusors applied directly to the turbine design and the effects that all this phenomens has into the blade design. [ABSTRACT FROM AUTHOR]

The departure of atoms from the surface of the condensed phase leads to the appearance of a flow of atoms flying not only from the surface but also, due to collisions of atoms, leads to the reverse flow of atoms from the gas phase to the condensed phase, and to the formation of nanoclusters that affect the flow of gas. In this regard, the first collisions of atoms after the departure from the surface of the condensed phase play an important role. In the present paper, the simultaneous flight of three atoms from the bounded surface of the condensed phase is considered. The first and second collisions of atoms were determined depending on the size of the evaporation area. The regularities for the densities of the distributions of collisions of atoms over the surface and the free path lengths, as well as their average values, are established. The calculations were performed using the direct Monte Carlo simulation. The atoms were represented as rigid spheres, so after the collision the atoms instantly flew apart. In each computer experiment, at least 180,000,000 triples of atoms were played. [ABSTRACT FROM AUTHOR]

Liquid movement in tanks that is partially filled can cause large structural loads if the tank movement is near the natural period of fluid within the tank. Sloshing implies the movement of a free liquid surface inside a vessel. A shake-table experiment for various depths of water of aspect ratio 0.163, 0.325, and 0.488 are investigated to examine the effect of sloshing. The frequencies of excitation range from 0.4566 Hz to 1.9757 Hz which covers up to the fifth mode sloshing frequency and a constant amplitude of 7.5mm is adopted. A single porous at l/2 location is considered to check its effectiveness in comparison with the unbaffled condition. Three different porosities of 15%, 20%, and 25 % are adopted. Capacitance wave probes are used to record the free surface elevation at the end walls. The results of maximum free surface elevation (ηmax) and spectral moments (mo) are present here. The suppression of resonant sloshing motion by porous baffle is analyzed. A higher sloshing oscillation is observed for the aspect ratio (hs/l) of 0.325 than compared with the other two fill levels. [ABSTRACT FROM AUTHOR]

A hump in the channel bed can have an effect on the free surface profile. This submerged obstruction can be used to regulate the flow of water upstream and downstream. In this study, we present a mathematical model to investigate fluid behavior in the existence of a hump. The governing equation used here is the linearized Boussinesq-type equation. The model is solved analytically to obtain the transient and steady solution. Numerically, we apply finite-difference-based methods, namely FTCS and two-step Lax-Wendroff to solve the model. Validations are performed by comparing the numerical results with the analytical solution. We conclude that the two-step Lax-Wendroff produces a more accurate result. Further, we examine several factors that affect the transient state's duration and the maximum wave elevation, such as the type of incoming flow (subcritical or supercritical) and the hump dimension. The widest hump from subcritical flow generates the longest time for waves to propagate in a transient state, while the narrowest hump from supercritical flow generates the highest wave elevation. [ABSTRACT FROM AUTHOR]

In this work, a study of the process of filling a plane tank with a central body with a non-Newtonian fluid is carried out. The flow is described by momentum equations and continuity equations; the no-slip conditions are satisfied on solid walls. The rheological behavior of the medium is described by the Ostwald-de Waale model. The fluid is supplied through an upper channel at a given flow rate. The problem is solved numerically using the finite volume method and the SIMPLE algorithm. The location of the free surface is determined using the VOF/PLIC method. Parametric studies are carried out for Newtonian, dilatant, and pseudoplastic fluids in the following ranges of the governing parameters: 0≤Re≤20 and 0≤W≤20. Different tank filling regimes are revealed depending on the parameters of the problem. The kinematic characteristics of the flow are obtained at various regimes. [ABSTRACT FROM AUTHOR]

This research presents a modification of "finite–size particle in cell" method developed for numerical modeling of processes at high energy density. It uses the Lagrangian–Eulerian representation of media which allows one to match contact and free surfaces and to calculate flows with strong deformations. Efficient models of thermodynamic properties, elastic–plastic deformation and fragmentation have been employed in the gas dynamic code adapted for parallel computations. 3D and 2D numerical modeling of plates penetrations by impactors of different geometry has been done in a wide range of velocities. The influence of used materials properties models on numerical results has been investigated. [ABSTRACT FROM AUTHOR]

The description of the implicit finite element method for the numerical solution of the Navier-Stokes equations in a three-dimensional formulation with allowance for surface tension is presented. The mathematical description of the process is based on the equations of motion, continuity, and natural boundary conditions on a free surface. The numerical solution of the problem is based on the finite element method with the approximation of the main variables of the problem (the vector of velocity and pressure), satisfying the condition of their compatibility. In addition, to reduce pressure oscillations in the vicinity of the free surface, increased pressure integration schemes on the element are used. The evolution of the free surface of a drop under the action of surface tension is considered as an example. The stability and computational efficiency of a model with approximate convergence and conservatism with an increase in the time step by two orders of magnitude relative to the currently used integration schemes is shown. [ABSTRACT FROM AUTHOR]

In our work, one-dimensional shallow water equations are proposed to model the phenomena of tsunami propagation and run-up. This model is known to be reliable to make predictions on maximum run-up along the shorelines above the mean sea level induced by the tsunami waves. 1D shallow water equations in a depth-averaged manner can be derived from incompressible Navier-Stokes equations by the simplification of lateral velocity (z-direction) using boundary conditions imposed on both free surface and bottom topography. In our current work, we assume there is no motion in the y-direction. Further, 1D shallow water equations in a conservative form are solved using the fourth-order Runge-Kutta method for time and second-order central difference schemes in space. We observed that the resulting high-order method in time is efficient, fairly accurate for their smaller stencil sizes, and has a slightly better stability property than that of the conventional forward Euler in time. This high-order method allows us to take larger mesh size and time steps while still producing small discretization errors. Our method was implemented using a low-level C++ programming language which is essential to incorporate larger domains (consecutively larger degrees of freedom) and to render fast computations. Using a conceptual test problem, we validate the numerical error, reproduce the theoretical convergence rate in both time and space while observing its computational efficiency. We also verified our model using two test problems – one for wave propagation and another is for the run-up. Our numerical models reproduced the expected outcomes when a tsunami wave travels in the ocean just before it arrives at the shoreline in terms of a solitary wave and finally collapses. [ABSTRACT FROM AUTHOR]

The present work focuses on the numerical investigation of fluid flow due to dam-break with a simplified building model. OpenFOAM®, an open source computational fluid dynamics tool was used to run the three-dimensional dam-break simulation. The volume of fluid (VOF) method was used to track the free surface or phase fraction(α) between two fluid interface. The results from the simulation are post-processed using Paraview. Liquid phase evolution at various time steps and flood wave impact on the different zones in the domain are discussed. In the downstream region, a low pressure wake zone was identified in the vicinity of the building. To escape from the dam-break flooding, the safer regions are identified through the simulation results. [ABSTRACT FROM AUTHOR]

A molecular dynamics simulation of the self-diffusion of thorium cations in ThO2 nanocrystals with a free surface is conducted. It is shown that a vacancy in the bulk of a crystal initiates a complex collective movement of cations, in which the interstitial positions surrounding the vacancy are involved. The diffusion coefficients of cations in the temperature range are calculated. The effective activation energy of diffusion is ED = (7.6 ± 0.7) eV. [ABSTRACT FROM AUTHOR]

The normal interaction of conical strikers made of heavy tungsten-iron-nickel alloy with monolithic and spaced barriers made of aluminum-manganese alloy with velocities up to 320 m/s is studied numerically. Modeling is carried out in a three-dimensional formulation by the finite element method using the author's algorithm and the EFES 2.0 software package, which allows modeling the fragmentation of interacting bodies with the formation of new contact and free surfaces, erosional destruction of materials. The behavior of the strikers and barriers materials is described by an elastoplastic model. The limiting value of the intensity of plastic deformation is used as a fracture criterion. A comparative analysis of the effectiveness of the protective properties of monolithic and spaced barriers is carried out. It was found that for the considered conditions of interaction, a monolithic barrier is more effective. The effectiveness of the barrier properties is assessed by the value of the velocity of the center of mass of the striker after the barrier is perforated. [ABSTRACT FROM AUTHOR]

The aim of this work is modeling of sway-sloshing motion in a partially filled rectangular tank while different frequency of motions are enforced. Within the study, a CFD code based on Smooth Particle Hydrodynamics (SPH) approach is developed for modelling violent free surface flows. The code is parallelized in order to run efficiently in supercomputers to solve complex flow phenomenon occurs in the cargo and fuel tanks of ships with a high resolution. It is shown that numerical results of the proposed SPH scheme are in good agreement with experimental and numerical findings of the literature and presently benefits from complex compute nodes of supercomputers. [ABSTRACT FROM AUTHOR]

The experiments are performed to study the liquid surface deformations caused by the thermocapillary effect. The Reflective Synthetic Schlieren method is used to restore the relief of the thin liquid film. The method is based on the analysis of two images of a background points pattern reflected from the free surface. Cross-correlation analysis between the underformed liquid layer and deformed one is used to reconstruct the displacement field. Poisson equation to obtain the free surface deformations is solved numerically. The technique allows to measure with sensitivity of less than 1 µm. [ABSTRACT FROM AUTHOR]

'Moon-Glade' Background Oriented Schlieren method for measuring liquid surface deformations was used. The method is based on the analysis of the background dots pattern images reflected from the liquid surface. The background pattern is a transparent polyester film with dots, which is located at a certain distance above the liquid. Compared to other methods that use a background image, this technique has the following advantages: (1) it allows restoring the instantaneous topography of a free surface with a sensitivity of less than 1 µm; (2) it is non-intrusive and only requires the camera and the background; (3) it is also suitable for a non-isothermal liquid layer and does not require the addition of dye. The studies of the free surface deformations caused by the buoyancy effect are carried out. It is shown that the measurement by this method is limited by the radius of the curvature of the free surface, but the range of measured values can be increased by reducing the distance from the background dots pattern to the liquid. [ABSTRACT FROM AUTHOR]

The mathematical statement of a problem about potential movement of a liquid for dependent variables is given, features of numerical algorithm for the decision of a spatial eaday, the system of the difference equations for potential is offered, the order of calculation of sizes in a single-step method is described, the method of construction of a grid is considered. [ABSTRACT FROM AUTHOR]

In the Continuous Casting Process (CCP), the utmost indispensable piece for making steel. The pattern relating to flow close to Submerged Entry Nozzle (SEN) enormously impact the nature of produced slab. The current examination performed was to pick up information with respect to the meniscus variance under various blockage of port conditions by liquid model tests. The examinations were done to examine the impact of having 0% blockage, blockage by 25 %, half blockage, and blockage by 75 % of SEN port on shape level changes. The outcome illustrates that when fluid rate of flow expands, amplitude near to the surface rises. In these analyses, the normal and most extreme meniscus vacillations remained estimated though changing various factors, for example, flow rate of liquid, submergence depth, and partly clogging of one side of the port of SEN while opposite side has been kept fully open. The perception displays that when size of the port declines, the liquid steel blended from the impeding side to the fully opened portion becomes in dissymmetry. The highest amplitude of the wave and the average value the amplitude of the wave increases with drop in the depth of submergence. It is seen that for most extreme case of the stationary wave, the shape kept ascending on the opened side of the SEN. Obstruction increments as of 25% to 75%, and for 75% clogging of right hand side of the SEN port, shape of the free surface change at the left half of the form is outrageous, while for the right hand side it is moderately calm. [ABSTRACT FROM AUTHOR]

The results of experimental studies on forced convection of a fluid inside a droplet blown by an external gas are carried out. The convection velocity in a droplet depends on the gas velocity and a droplet diameter. The experimental data are compared with numerical solutions. When a water droplet is blown by air, an underestimation of the velocity in droplet is observed, in comparison with the calculation, by about 35–40 times. It is assumed that a strong discrepancy between experiment and calculation is associated with the accumulation of impurities (contaminants) on the free surface of a droplet. In the absence of a free surface (liquid-gas), the calculation satisfactorily describes the experimental data. The case of a drop of one liquid in a flow other liquid is considered. Convection for different liquids is compared. [ABSTRACT FROM AUTHOR]

Experiments have been carried out to investigate convective motion in a stationary hanging droplet of water in an air flow. When modeling convective motion in a hanging drop, all key factors must be taken into account: air velocity; the thermal Marangoni flow (MaT), the solutal Marangoni flow (MaC), the Rayleigh number (Ra). The effect of air velocity on convection in a droplet decreases by a factor of 35–40 due to contamination on the free surface of the drop. The liquid velocity parameters were measured using the Particle Image Velocimetry method. The data obtained are of both scientific and practical interest. [ABSTRACT FROM AUTHOR]

A representation for the effect of internally heated on penetrative Bénard-Marangoni-ferroconvection (BMF) driven by constant and uniform volumetric heating with magnetic field dependent (M FD) viscosity is studied. The lower surface is rigid-isothermal and the upper free surface is considered to be plane and non-deformable subject to Robin type of thermal boundary condition. A Galerkin-type is based on the weighted residual method (WRM) has been used to obtain the eigenvalue for gravity and magnetic thermal Rayleigh number. It is noted that the buoyancy, magnetic and surface tension forces influence the onset of BMF. The onset of BMF is delayed with an increase in magnetic field dependent viscosity parameter (Λ), Biot number (Bi) and magnetic susceptibility (χ) with an increase in the region of stability. In addition, the nonlinearity of fluid magnetization (M 3) and magnetic number (M 1) is found to hasten the onset of FTC. Some existing results are reproduced as particular cases from the present study. [ABSTRACT FROM AUTHOR]

This research presents a numerical simulation of flow around surface piercing vertical cylinder at different Froude numbers. The Finite Volume Method (FVM) based on Navier-Stokes Equations is used for the simulation. The Shear Stress Transport (SST) k-omega turbulence model has been incorporated to capture the turbulent boundary layer. The Volume of Fluid (VOF) method is applied to track the free surface of the water. A highly accurate scheme named High-Resolution Interface Capturing (HRIC) is implemented with the volume of fluid method for flux evaluation. To accomplish all of the above procedures, a commercial CFD software 'ANSYS-FLUENT' is used. The profile of air-liquid interface on a cylinder, drag coefficient, velocity fields, and dynamic pressure fields at different liquid layer and wall shear stress is computed and compared with previous experimental and simulation results. At a particular Froude number, the wave-induced separation of velocity fields is studied and it is found that the effects decrease with increasing depth. It is also found that the free surface is highly influenced by increasing Froude number. The dynamic pressure and drag coefficient increase with the increase in the Froude number. Finally, separation regions of wall shear stress are studied for three different Froude numbers. [ABSTRACT FROM AUTHOR]

Dynamic fracture behavior of two nano-cracks in a functionally graded elastic isotropic half-plane under excitation of time-harmonic P-wave is studied. The applied approach is based on the non-hypersingular traction based boundary integral equation method for the graded bulk elastic isotropic solid extended with the non-classical boundary conditions and the localized constitutive law for the matrix-nano-crack interface within the framework of the Gurtin-Murdoch theory. The formulation allows for a quadratic variation of the material properties in depth. The boundary integral equation is treated by using the frequency dependent half-plane Green's function derived analytically by application of an appropriate functional transform, accompanied by a follow-up Fourier transform. The numerical solution provides stress-strain state at any point in the semi-infinite graded solid as well as the displacements from which the stress concentrations are determined. Simulations for two nano-cracks parallel to the free surface of the half-plane are presented and discussed. They reveal the sensitivity of the scattered wave field and dynamic stress concentration factors to the complex influence of nano-cracks interaction phenomena, existence of material gradient and surface elasticity effects. The verification and parametric study illustrate convincingly the applicability of the proposed mechanical model in material science of functional graded composites and in computational dynamic fracture mechanics. [ABSTRACT FROM AUTHOR]