Advances In Numerical Simulation Research Articles

Numerical Simulation Technologies in Solar-Driven Interfacial Evaporation Processes.

Solar interfacial evaporation technology has the advantages of environmentally conscious and sustainable benefits. Recent research on light absorption, water transportation, and thermal management has improved the evaporation performance of solar interfacial evaporators. However, many studies on photothermal materials and structures only aim to improve performance, neglecting explanations for heat and mass transfer coupling or providing evidence for performance enhancement. Numerical simulation can simulate the diffusion paths and heat and water transfer processes to understand the thermal and mass transfer mechanism, thereby better achieving the design of efficient solar interfacial evaporators. Therefore, this review summarizes the latest exciting findings and tremendous advances in numerical simulation for solar interfacial evaporation. First, it presents a macroscopic summary of the application of simulation in temperature distribution, salt concentration distribution, and vapor flux distribution during evaporation. Second, the utilization of simulation in the microscopic is summed up, specifically focusing on the movement of water molecules and the mechanisms of light responses during evaporation. Finally, all simulation methods have the goal of validating the physical processes in solar interfacial evaporation. It is hoped that the use of numerical simulation can provide theoretical guidance and technical support for the application of solar-driven interfacial evaporation technology.

Advances in numerical simulation with a clustering method based on K–means algorithm and Adams Bashforth scheme for fractional order laser chaotic system

In this research work, we present a mathematical analysis of a fractional sixth-order laser model of a resonant which is homogeneously extended three-level optically pumped. We use Caputo fractional order derivative in the proposed model. Our analysis includes an investigation of various chaotic behaviors under fractional order derivative and qualitative theory of the existence of the solution to the proposed model. For our required analysis of qualitative type, we use formal analysis tools. Further, numerical simulations are performed with a clustering method based on the K–Means algorithm and Adams Bashforth scheme. With the help of the aforesaid scheme, we present different chaotic behavior corresponding to various values of fractional order. Finally, we give a comparison of the CPU time of the proposed method with that of the RK4 method.

Finite Element Methods for Modeling the Pressure Distribution in Human Body–Seat Interactions: A Systematic Review

The objective of this systematic review is to investigate the various approaches that have been undertaken in finite element analysis (FEA) of human–seat interactions and synthesize the existing knowledge. With advances in numerical simulation and digital human modeling, FEA has emerged as a powerful tool to study seating comfort and discomfort. FEA employs various biomechanical factors to predict the contact stress and pressure distribution in a particular seat design. Given the complexity of human–seat interaction, several modeling and processing steps are required to conduct realistic FEA. The steps of how to perform an FEA simulation on human–seat interactions, the different models used, the model mesh compositions, and the material properties are discussed and reviewed in this paper. This can be used as a guideline for future studies in the context of FEA of human–seat interactions.

A Comprehensive Review of Liquid Ring Vacuum Pumps and Compressors for Improving Global Efficiency and Energy Saving

Liquid ring vacuum pumps and compressors are mechanical positive displacement turbomachines that can operate in the mode of both vacuum compressor and vacuum pump. They are widely used in the fields of filtration, cryogenic, reaction, gas injection, condensation, evaporation, and convective drying. Despite their low performance, they have many advantages such as low costs, simplicity, reliability, improve suction characteristics, and in many cases, can provide a more efficient option. Improving efficiency is the key to decrease energy consumption and costs. The article analyzed and evaluated the previous investigations regarding these machines with a focus on challenges of improving efficiency, advances in numerical simulation, and experiments to afford beneficial insight on future research and next steps. The study revealed that the thermal interaction and the cavitation phenomenon are among the most important problems that require further research.

Drying behavior of steel-ladle lining refractory castables under continuous heating rate

The current trend to replace shaped refractories for monolithics is related to various technical aspects, i.e., lack of joints, easier installation and free format. However, the main drawback of these non-shaped products is their longer first heat-up demand, otherwise mechanical failures or even explosive spalling may take place due to steam pressurization within the well packed consolidated structure. As a consequence, over-conservative drying schedules are commonly used in industrial equipment lined with such ceramics, which increase the energy consumption and the production down-time. Based on this scenario and considering the recent advances in numerical simulations, this article discusses the implications of applying different heating rates during the drying of a refractory castable lining of a steel ladle. Additionally, a novel methodology based on the correlation of the maximum vapor pressure and the mechanical strength of the ceramic material was also proposed. Using some of the castable properties measured as a function of temperature, simulation results pointed out that higher vapor pressures and a displacement of the maximum pressure peak are attained by applying high heating rates and thicker linings. This behavior is associated with the water migration to the inner regions of the refractory structure. It was observed that these conditions displace the maximum resistance ratio position towards the hot face, where most common spallings are observed. The work also emphasizes the importance of carrying out accurate measurements of physical properties as a function of the temperature, otherwise the outcome can be far from the reality of the working conditions.

On ultrasound propagation in composite laminates: advances in numerical simulation

The growing use of composite materials for aerospace applications has resulted in the need for quantitative methods to analyze composite components. Ultrasonic guided waves constitute the physical approach for nondestructive evaluation (NDE) and structural health monitoring (SHM) of solid composite materials, such as carbon fiber reinforced polymer (CFRP) laminates. Ultrasound based NDE methods are commonly used in the aerospace field, but ultrasonic wave behavior can be complicated by the presence of material anisotropy, complex geometries (e.g., highly curved parts, stiffeners, and joints) and complex geometry defects. Common defects occurring in aerospace composites include delaminations, porosity, and microcracking. Computational models of ultrasonic wave propagation in CFRP composites can be extremely valuable in designing practical NDE and SHM hardware, software, and methodologies that accomplish the desired accuracy, reliability, efficiency, and coverage. Physics based simulation tools that model ultrasonic wave propagation can aid in the development of optimized inspection methods and in the interpretation of NDE data. This paper presents a review of numerical methodologies for ultrasound and guided wave simulation in fiber reinforced composite laminates summarizing the relevant works to date, different methods, and their respective applications.

Modern perspectives on near-equilibrium analysis of Turing systems.

In the nearly seven decades since the publication of Alan Turing’s work on morphogenesis, enormous progress has been made in understanding both the mathematical and biological aspects of his proposed reaction–diffusion theory. Some of these developments were nascent in Turing’s paper, and others have been due to new insights from modern mathematical techniques, advances in numerical simulations and extensive biological experiments. Despite such progress, there are still important gaps between theory and experiment, with many examples of biological patterning where the underlying mechanisms are still unclear. Here, we review modern developments in the mathematical theory pioneered by Turing, showing how his approach has been generalized to a range of settings beyond the classical two-species reaction–diffusion framework, including evolving and complex manifolds, systems heterogeneous in space and time, and more general reaction-transport equations. While substantial progress has been made in understanding these more complicated models, there are many remaining challenges that we highlight throughout. We focus on the mathematical theory, and in particular linear stability analysis of ‘trivial’ base states. We emphasize important open questions in developing this theory further, and discuss obstacles in using these techniques to understand biological reality.This article is part of the theme issue ‘Recent progress and open frontiers in Turing’s theory of morphogenesis’.

Dynamo constraints on the long-term evolution of Earth’s magnetic field strength

SUMMARY Elucidating the processes in the liquid core that have produced observed palaeointensity changes over the last 3.5 Gyr is crucial for understanding the dynamics and long-term evolution of Earth’s deep interior. We combine numerical geodynamo simulations with theoretical scaling laws to investigate the variation of Earth’s magnetic field strength over geological time. Our approach follows the study of Aubert et al., adapted to include recent advances in numerical simulations, mineral physics and palaeomagnetism. We first compare the field strength within the dynamo region and on the core–mantle boundary (CMB) between a suite of 314 dynamo simulations and two power-based theoretical scaling laws. The scaling laws are both based on a Quasi-Geostropic (QG) force balance at leading order and a Magnetic, Archimedian, and Coriolis (MAC) balance at first order and differ in treating the characteristic length scale of the convection as fixed (QG-MAC-fixed) or determined as part of the solution (QG-MAC-free). When the data set is filtered to retain only simulations with magnetic to kinetic energy ratios greater than at least two we find that the internal field together with the root-mean-square and dipole CMB fields exhibit power-law behaviour that is compatible with both scalings within uncertainties arising from different heating modes and boundary conditions. However, while the extrapolated intensity based on the QG-MAC-free scaling matches Earth’s modern CMB field, the QG-MAC-fixed prediction shoots too high and also significantly overestimates palaeointensities over the last 3.5 Gyr. We combine the QG-MAC-free scaling with outputs from 275 realizations of core–mantle thermal evolution to construct synthetic true dipole moment (TDM) curves spanning the last 3.5 Gyr. Best-fitting TDMs reproduce binned PINT data during the Bruhnes and before inner core nucleation (ICN) within observational uncertainties, but PINT does not contain the predicted strong increase and subsequent high TDMs during the early stages of inner core growth. The best-fitting models are obtained for a present-day CMB heat flow of 11–16 TW, increasing to 17–22 TW at 4 Ga, and predict a minimum TDM at ICN.

낙하하는 액적의 계면활성제 흡수 거동에 관한 수치 해석 연구

Surfactant, which has hydrophilic heads and hydrophobic tails, tends to accumulate at the phase interface. In general, surfactant decreases the surface tension coefficient locally, and thereby affects the dynamics of interface motion as well as flow characteristics. Although recent advances in numerical simulation for multiphase flow systems have made it possible to understand complicated interfacial phenomena interacting with surfactant, most of the existing numerical studies have mainly focused on the surfactant adsorption behaviors of rising bubbles so far. In this study, we attempt to analyze the effect from surfactant in the concentration field of external gas with a freely falling droplet. A Numerical model for tracking the movement of interface is proposed by using Level Contour Reconstruction Method (LCRM), and the governing equations for the surfactant transport are also formulated. Two benchmarking tests, i.e. Marangoni migration of a droplet, and a bubble rise interacting with surfactant, are performed to check the validity of proposed numerical formulation. Interaction behavior of surfactant with a freely falling droplet is compared with the case of rising bubble. In addition, the adsorption characteristics of surfactant during the free fall of a droplet are analyzed with various non-dimensional flow conditions. The absorption coefficient and the maximum surfactant concentration have been found to be the effective variables to increase the total absorption amount.

The Catalogue for Astrophysical Turbulence Simulations (CATS)

Abstract Turbulence is a key process in many fields of astrophysics. Advances in numerical simulations of fluids over the last several decades have revolutionized our understanding of turbulence and related processes such as star formation and cosmic ray propagation. However, data from numerical simulations of astrophysical turbulence are often not made public. We introduce a new simulation-oriented database for the astronomical community: the Catalogue for Astrophysical Turbulence Simulations (CATS), located at www.mhdturbulence.com. CATS includes magnetohydrodynamic (MHD) turbulent box simulation data products generated by the public codes athena++, arepo, enzo, and flash. CATS also includes several synthetic observational data sets, such as turbulent HI data cubes. We also include measured power spectra and three-point correlation functions from some of these data. We discuss the importance of open-source statistical and visualization tools for the analysis of turbulence simulations such as those found in CATS.

Understanding dense hydrogen at planetary conditions

Materials at high pressures and temperatures are of great interest for planetary science and astrophysics, warm dense-matter physics and inertial confinement fusion research. Planetary structure models rely on an understanding of the behaviour of elements and their mixtures under conditions that do not exist on Earth; at the same time, planets serve as natural laboratories for studying materials at extreme conditions. The topic of dense hydrogen is timely given the recent accurate measurements of the gravitational fields of Jupiter and Saturn, the current and upcoming progress in shock experiments, and the advances in numerical simulations of materials at high pressure. In this Review we discuss the connection between modelling planetary interiors and the high-pressure physics of hydrogen and helium. We summarize key experiments and theoretical approaches for determining the equation of state and phase diagram of hydrogen and helium. We relate this to current knowledge of the internal structures of Jupiter and Saturn, and discuss the importance of high-pressure physics to their characterization. Understanding the behaviour of materials at high pressures and temperatures is of great importance to planetary science and the physics of warm dense matter. This Review addresses the close connection between modelling the interiors of gaseous planets and the high-pressure physics of hydrogen and helium.

Advances in Numerical Simulations of Hydrothermal Ore Forming Processes

Advances in Numerical Simulations of Hydrothermal Ore Forming Processes

An Advanced Multiple‐Layer Canopy Model in the WRF Model With Large‐Eddy Simulations to Simulate Canopy Flows and Scalar Transport Under Different Stability Conditions

AbstractForest canopies play a critical role in affecting momentum and scalar transfer. Although there have been recent advances in numerical simulations of turbulent flows and scalar transfer across plant canopies and the atmosphere interface, few models have incorporated all important physical and physiological processes in subcanopy layers. Here we describe and evaluate an advanced multiple‐layer canopy module (MCANOPY), which is developed based largely on the Community Land Model version 4.5 and then coupled with the Weather Research and Forecasting model with large‐eddy simulations (WRF‐LES). The MCANOPY includes a suite of subcanopy processes, including radiation transfer, photosynthesis, canopy layer energy balance, momentum drag, and heat, water vapor, and CO2 exchange between canopy layers and the canopy atmosphere. Numerical schemes for heat and water transport in soil, ground surface energy balance, and soil respiration are also included. Both the stand‐alone MCANOPY and the coupled system (the WRF‐LES‐MCANOPY) are evaluated against data measured in the Canopy Horizontal Array Turbulence Study field experiment. The MCANOPY performs reasonably well in reproducing vertical profiles of mean and turbulent flows as well as second‐order statistical quantities including heat and scalar fluxes within the canopy under unstable stability conditions. The coupled WRF‐LES‐MCANOPY captures major features of canopy edge flows under both neutral and unstable conditions. Limitations of the MCANOPY are discussed for our further work. Our results suggest that our model can be a promising modeling system for a variety of applications to study canopy flows and scalar transport (e.g., CO2).

Star formation in cloud cores — simulations and observations of dense molecular cores and the formation of solar mass stars

AbstractStar formation is inefficient. Recent advances in numerical simulations and theoretical models of molecular clouds show that the combined effects of interstellar turbulence, magnetic fields and stellar feedback can explain the low efficiency of star formation. The star formation rate is highly sensitive to the driving mode of the turbulence. Solenoidal driving may be more important in the Central Molecular Zone, compared to more compressive driving agents in spiral-am clouds. Both theoretical and observational efforts are underway to determine the dominant driving mode of turbulence in different Galactic environments. New observations with ALMA, combined with other instruments such as CARMA, JCMT and the SMA begin to reveal the magnetic field structure of dense cores and protostellar disks, showing highly complex field geometries with ordered and turbulent field components. Such complex magnetic fields can give rise to a range of stellar masses and jet/outflow efficiencies in dense cores and protostellar accretion disks.

Advances in numerical simulation of sonic boom in realistic atmospheres

Efficient and accurate numerical simulation of sonic boom is a key issue for both the design of low boom aircraft and the definition of a standard on supersonic overland flights. Atmospheric turbulence is known since the 1960s to significantly alter the ideal N-wave boom waveform. Such random fluctuations cannot be reproduced by the standard ray tracing method. Neither can it simulate the lateral boom beyond the geometrical carpet edge. There occur many non-geometrical features such as creeping waves, wave guiding or scattering. To progress in the direction of boom simulation beyond the geometrical approximation, we developed the so-called FLHOWARD3D software. For accuracy, it can handle 3D temperature, density or wind heterogeneities, atmospheric absorption, and nonlinear propagation effects. For efficiency, a one-way approximation is performed, neglecting the backscattered field. Nevertheless, the forward field satisfies an accurate dispersion relation, even in moving atmospheres. Involved physical effects are handled separately by optimized algorithms, combined by a second-order split-step approach. The resulting software is parallelized using the MPI paradigm. The performances of the software will be illustrated by two cases: boom scattering by turbulence, and lateral boom propagation in case of temperature inversion. This last case will be compared with flight test data.

Recent Advances in Numerical Simulation of Propagation of EM Waves in the Earth's Ionosphere

EM wave propagation in the magnetoactive terrestrial ionosphere was investigated by numerical methods, and associated software was developed. Two principal functions were realized: ray tracing and ionogram synthesis. For the first time, reference-standard models, including the International Reference Ionosphere (IRI) 2012, World Magnetic Model 2010, and World Geodetic System 1984, have been globally implemented for every component of the propagation medium, and fully manipulatable 3-D visualization was enabled in a study utilizing the bicharacteristic method. An assimilation model of the ionosphere was also used along with IRI. The focus was on the unveiling of multiskip long-range propagation effects. Effective numerical algorithms for solving the bicharacteristic system that allow rapid insight into an extremely large-scale EM problem and enable quasi-real-time operation were discussed. The simulation in the presence of abnormal locally increased or decreased electron density in the ionosphere of natural or artificial occurrence was considered. Experimental ionograms obtained by an ionosonde were compared to numerically synthesized ones.

Fluid-Structure Interaction Study of Stenotic Flow in Subject Specific Carotid Bifurcation—A Case Study

Advances in numerical simulation have allowed the investigation of complex interaction of blood flow through elastic arteries which can be useful in demonstrating the disease progression and haemodynamics of cardiovascular diseases such as atherosclerosis. In the present study, patient is diagnosed with an occluded right Internal Carotid Artery (ICA) with partial stenosis at root of right External Carotid Artery (ECA) and partial stenosis at the root of left ICA. 3D patient specific carotid bifurcation is generated based on CT scan data using MIMICS-14.0 and numerical analysis is performed using FSI in ANSYS-14.5. The blood flow is assumed to be incompressible, homogenous and Newtonian, while artery wall is assumed to behave linearly elastic. The two-way sequentially coupled transient FSI analysis is performed using FSI solver for three pulse cycles and haemodynamic parameters such as flow pattern, Wall Shear Stress (WSS), pressure contours and arterial wall deformation are studied at the bifurcation and critical zones. The variation in flow behavior is investigated throughout the pulse and simulation results obtained reveals that there is a considerable increase in the flow behavior in partially stenosed carotid unlike occluded carotid. The investigation also demonstrates disturbed flow pattern especially at the bifurcation and stenosed zone elevating the haemodynamic variation during peak systole and later part of pulse cycle. The obtained results agree well with the clinical observation and demonstrate the potential of patient specific numerical studies in prognosis of disease progression and plaque rupture

Theory of pulsar magnetosphere and wind

Neutron stars are fascinating astrophysical objects immersed in strong gravitational and electromagnetic fields, at the edge of our current theories. These stars manifest themselves mostly as pulsars, emitting a timely very stable and regular electromagnetic signal. Even though discovered almost fifty years ago, they still remain mysterious compact stellar objects. In this review, we summarize the most fundamental theoretical aspects of neutron star magnetospheres and winds. The main competing models explaining their radiative properties like multi-wavelength pulse shapes and spectra and the underlying physical processes such as pair creation and radiation mechanisms are scrutinized. A global but still rather qualitative picture slowly emerges thanks to recent advances in numerical simulations on the largest scales. However considerations about pulsar magnetospheres remain speculative. For instance, the exact composition of the magnetospheric plasma is not yet known. Is it solely filled with a mixture of$e^{\pm }$ leptons or does it contain a non-negligible fraction of protons and/or ions? Is it almost entirely filled or mostly empty except for some small anecdotal plasma filled regions? Answers to these questions will strongly direct the description of the magnetosphere to seemingly contradictory results leading sometimes to inconsistencies. Nevertheless, accounts are given as to the latest developments in the theory of pulsar magnetospheres and winds, the existence of a possible electrosphere and physical insight obtained from related observational signatures of multi-wavelength pulsed emission.

Recent Advances in Numerical Simulation of Material Flow Behavior during Frictions Stir Welding

Friction stir welding(FSW) is a revolutionary welding technology for joining metallic materials such as aluminum alloys and magnesium alloys. The advantages of FSW over traditional fusion welding stem from the fact that material experiences severe plastic flow at temperatures below melting point. Therefore, it is critical to study and understand the material flow behaviors in order to optimize the FSW processing condition. Due to the spatial and temporal limitations of experimental studying, numerical simulation becomes an importance methodology in studying the material flow behavior. The basic physical processes involved in FSW process are analyzed. Thereafter, the numerical simulation on the material flow behavior is reviewed regarding the numerical method, heat source model, frictional boundary condition and constitutive model. Finally, the recent applications of the numerical models are discussed. In addition, the shortcomings in the current models and key points for the future researches are also pointed out.

The gas gun launch advances in numerical simulation of hypervelocity impact

The gas gun launch advances in numerical simulation of hypervelocity impact