Multiphysics

Modeling of Pervaporation process for water-alcohol separation with polymer membrane was performed using COMSOL Multiphysics software. Modeling was performed for two parts of the membrane and feed channel. For the feed section of the semiconductor, there is a mass transfer and semiconductor transfer term, while only the mass transfer occurs in the membrane. The flux from the membrane was calculated for the various concentrations and temperatures of the feed by the software. The concentration profiles in the membrane and the profile of speed and concentration in the feed channel were calculated for different operating conditions. The results showed that the modeling error to predict the flow of flask from the membrane for various feed concentrations (1.5-2.1%) was acceptable. For feed at different temperatures, the calculated error values are between (2.7-5.5) percent. Also, the speed and concentration profiles in the input channel of the feed and inside the membrane are calculated for the velocity and concentration of different feed intakes and along the channel by the software and the results are presented according to the results obtained, it can be concluded that the modeling of the evapotranspiration process using COMSOL Multiphysics software can help predict the results and determine the design parameters of the process.

In this book, a multi-physics approach to the modeling and analysis of nuclear reactor core behavior is presented, and applied to study the dynamics of Molten Salt Reactors (MSR). The Multi-Physics Modeling (MPM) approach is implemented in a unified simulation environment, which results able to catch the synergy between the different phenomena involved in the
reactor core behavior, whose modeling would otherwise require either the adoption of existing simulation tools with drastic modifications of their structure and possible loss of significant information or the development of purpose-made numerical codes for the specific analyzed situation.
The book is organized into four chapters, which are conceived so as to be read independently of each other. Here, the rationale of the R&D activities performed at the Politecnico di Milano by the authors, and giving rise to the book contents, is briefly outlined.
In the last years, MSRs have been the subject of a growing and renewed interest from the scientific community in the framework of the Generation IV International Forum. Due to the availability of an advanced conceptual design, the Molten Salt Breeder Reactor (MSBR) developed at the Oak Ridge
National Laboratory during the 1960s is usually considered in the literature as reference system for benchmark analyses and validation purposes. Coherently, the MSBR has been chosen as reference configuration for the analyses presented in the book. In such kind of Circulating Fuel Reactor (CFR), like the other MSRs, the coupling between neutronics and thermo-hydrodynamics is a key issue. This feature cannot be neglected in order to perform an adequate description of the reactor dynamic behavior, which shows peculiar aspects with respect to solid-fuelled conventional nuclear power plants. Relevant differences in terms of safety, fuel cycle and technology also distinguish the MSRs from the other nuclear reactors (Chapter 1).
The developed MPM methodology and the adopted models for neutronics and thermo-hydrodynamics required a deep investigation for what concerns the assessment and the extension of the simulation environment, represented in the specific case by the finite element COMSOL Multiphysics® software (chosen thanks to its flexible and modular numerical structure), but the same methodology can be applied to other multi-physics platforms. As far as thermo-hydrodynamics is concerned, a generalized approach was developed (Chapter 2) and exploited for the assessment of COMSOL simulations
(Chapter 3), making use of a dedicated finite volume computational fluid dynamics code (FLUENT®), in order to better appreciate the differences in numerical approaches to turbulence. The generalized approach was built in order to carefully take into account the molten salt mixture specificities (i.e., a fuel that operates also as coolant), the reactor core power conditions and the heat transfer in graphite. In this context, a Nusselt number correlation was developed, which takes into account the effect of internal heat generation on
fluid heat transfer characteristics. As far as neutronics is concerned, a module for the "reactor physics" was built in the COMSOL environment of simulation, and allowed to extend the potentialities of this computing platform. Numerical results were assessed by means of: (i) a code-to-code comparison with
dedicated neutron transport codes, in the case of static fuel; (ii) a comparison with simplified neutron kinetics models, representative of the zero-power dynamics, in the case of circulating fuel.
After the assessment of the COMSOL capabilities to cope with the adopted models for neutronics and thermo-hydrodynamics, the MPM approach was applied to study the dynamic behavior of a single-channel representative of the average conditions of the MSBR core (Chapter 4). For this case study, the MPM approach resulted particularly suitable because of the strong nonlinear coupling between the fuel motion and neutron dynamics, which requires a careful description of the time-space distribution of the physical quantities. Several different transients were analyzed, such as those driven by: reactivity variations due to control rod movements; fuel mass flow rate variations due to the change of the primary pump working conditions; presence of periodic perturbations, due to local precipitation of fissile solid compounds within the molten salt mixture. The analyses gave significant information on the MSBR dynamic behavior and highlighted the several advantages and potentialities offered by the proposed MPM approach (for instance, the "modularity", namely the possibility to include other physical phenomena and couplings).
These potentialities are of more general interest in the prospect of studying the design configuration, the dynamics and the control strategy of next generation MSRs, as well as of other nuclear reactor types.

This paper presents a methodology to determine the thermal conductivity of ice using Multiphysics analysis. This methodology used a combination of both experimentation and numerical simulation. In the experimental work, an ice block is observed using an infrared camera. The results reveal the variation in temperature over the surface. These results are dependent on two primary heat transfer parameters, namely, conductivity of ice within the ice cuboid and overall heat transfer coefficient. In addition to these two parameters, the surrounding temperature also affects the observed temperature profile. In the numerical simulation, the same behaviour is simulated using Multiphysics tools. In this work, the finite difference method is used to discretize the heat equation and is solved using an FTCS (Forward-Time Central-Space) method in MATLAB® software. The inputs to the simulation are the thermal properties of ice. These parameters are varied to match with the experimental results, hence revealing the real-time thermal properties of ice and surroundings.

This paper presents a multi-physics modelling (MPM) approach developed for the study of the dynamics of the Molten Salt Reactor (MSR), which has been reconsidered as one of the future nuclear power plants in the framework of the Generation IV International Forum for its several potentialities. The proposed multi-physics modelling is aimed at the description of the coupling between heat transfer, fluid dynamics and neutronics characteristics in a typical MSR core channel, taking into account the spatial effects of the most relevant physical quantities. In particular, as far as molten salt thermo-hydrodynamics is concerned, Navier–Stokes equations are used with the turbulence treatment according to the RANS (Reynolds Averaged Navier–Stokes) scheme, while the heat transfer is taken into account through the energy balance equations for the fuel salt and the graphite. As far as neutronics is concerned, the two-group diffusion theory is adopted, where the group constants (computed by means of the neutron transport code NEWT of SCALE 5.1) are included into the model in order to describe the neutron flux and the delayed neutron precursor distributions, the system time constants, and the temperature feedback effects of both graphite and fuel salt. The developed MPM approach is implemented in the unified simulation environment offered by COMSOL Multiphysics Ò , and is applied to study the behaviour of the system in steady-state conditions and under several transients (i.e., reactivity insertion due to control rod movements, fuel mass flow rate variations due to the change of the pump working conditions, presence of periodic perturbations), pointing out some advantages offered with respect to the conventional approaches employed in literature for the MSRs.

A numerical framework based on a modified Monte Carlo ray-tracing method and the Discrete Element Method (DEM) is developed to predict the physical behavior of discrete particles during the Powder Bed Fusion (SLS) process. A comprehensive model coupling all major aspects of the underlying physics and the corresponding numerical framework, accounting for radiative heat transfer, heat conduction, sintering and granular dynamics among others, is developed. In particular, the effect of scattering on the laser-particle interaction is investigated and accounted for in the numerical framework. The spatially and temporally varying distribution of heat and displacement within the additively manufactured object are captured in detail. The model is validated through the comparison of simulated results with existing experimental results in the literature.

Simulasi penyajian kapasitor MEMS ( Micro-Electro-Mechanical Systems ) ini menggunakan perangkat lunak COMSOL Multiphysics 5.0.Penelitian ini terdiri dari merancang dan menyetel atau tining kapasitor pelat paralel yang dapat diatur secara elektrostatis untuk mendapatkan peningkatan nilai kapasitansi. Menyetel nilai kapasitansi dengan mengubah parameter desain kapasitor telah dilakukan dan ditunjukkan dengan 3 cara yaitu: dengan mengubah bahan dielektrik, mengurangi ketinggian pegas, dan memperluas area kapasitor.

Ramp-wave dynamic-compression experiments are used to examine quasi-isentropic loading paths in materials. The gradual and continuous increase in pressure created by ramp waves make these types of experiments ideal for studying nonequilibrium material behavior, such as solidification kinetics. In ramp-wave compression experiments, the input drive pressure to the experimental setup may be exerted through one of a number of different mechanisms (e.g., magnetic fields, gas-gun-driven impactors, or high-energy lasers) and is generally required for simulating such experiments. Yet, regardless of the specific mechanism, this drive pressure cannot be measured directly (measurements are generally taken at a location near the back of the experimental setup through a transparent window), leading to an inverse problem where one must determine the drive pressure at the front of the experimental setup (i.e., the input) that corresponds to the particle velocity (the output) measured near the back of the experimental setup. We solve this inverse problem using a heuristic optimization algorithm, known as differential evolution, coupled with a multiphysics, hydrodynamics code that simulates the compression of the experimental setup. By running many rounds of forward simulations of the experimental setup, our optimization process iteratively searches for a drive pressure that is optimized to closely reproduce the experimentally measured particle velocity near the back of the experimental setup. While our optimization methodology requires a significant number of hydrodynamics simulations to be conducted, many of these can be performed in parallel, which greatly reduces the time cost of our methodology. One novel aspect of our method for determining the drive pressure is that it does not require physical modeling of the drive mechanism and can thus be broadly applied to many types of ramp-compression experiments, regardless of the drive mechanism.

In this paper, we proposed a methodology to model, verify, and generate IEC standard PLC code using Timed-MPSG (an extended version of finite state automata). It can reduce PLC development time and the errors that generally occur when PLC programs are manually programmed. For this purpose, we used Timed-MPSG to model the formal specification of the targeted shop floor controller system, after that, the graphical representation of Timed-MPSG is converted to the textual format automatically. Thereafter, ...

One of the most revealing causes of deterioration leading to durability loss in concrete structures is premature time-tocorrosion ignition due to chloride induced corrosion associated with diffusive transport of chloride in concrete. To permit a more realistic modeling of the diffusive transport of chloride in concrete, chloride binding capacity model based on experimental isotherm describing the relation between total, bound, and free chlorides have to be considered. The aim of this work is to demonstrate the capability of using COMSOL Multiphysics modeling to provide insight regarding a more realistic consideration of chloride penetration behavior in concrete in view of chloride binding. Simulations of the problem in COMSOL allow main process of the chloride binding to be closely captured in the light of its nonlinear concentration dependence and influence on evolution of chloride diffusivity governing the transport problem. Good agreement of the model results with experimental da...

We consider multiphysics applications from algorithmic and architectural perspectives, where “algorithmic” includes both mathematical analysis and computational complexity, and “architectural” includes both software and hardware environments. Many diverse multiphysics applications can be reduced, en route to their computational simulation, to a common algebraic coupling paradigm. Mathematical analysis of multiphysics coupling in this form is not always practical for realistic applications, but model problems representative of applications discussed herein can provide insight. A variety of software frameworks for multiphysics applications have been constructed and refined within disciplinary communities and executed on leading-edge computer systems. We examine several of these, expose some commonalities among them, and attempt to extrapolate best practices to future systems. From our study, we summarize challenges and forecast opportunities.

Wireless power transfer system has a major concern for several decades since various benefits have been included against wired counterpart. In this context, coupling structure has been investigated for various coils having different shapes of both magnetic cores and windings. This investigation is implemented based on a mathematical and modeling analysis to calculate inductive values of charging setups. This paper provides an accurate evaluation of inductive characteristics for the proposed coreless helical and spiral coils. The evaluation considers the dependence of inductive parameters on distance, geometry, and misalignment of coupling coils. In addition, the evaluation method is verified by the COMSOL software. Moreover, an accurate approximation of required inductive parameters is provided for the design of wireless charging system. Furthermore, four ferrite cores are provided for both winding types; and their coupling coefficients are examined to show the best configuration. R...

Chapter 9 Pull-In Instability in Electrostatically Actuated MEMS due to Coulomb and Casimir Forces Romesh C. Batra and Davide Spinello Department of Engineering Science and Mechanics Virginia Polytechnic Institute and State University Blacksburg, VA 24061, USA rbatra@ vt. ...