Physical Modeling Method Research Articles

The Analysis and Research of Electric Dynamic Load Simulator

The aero load simulator is a typical application of electric dynamic load simulator in the engineering. It is important half hardware-in-loop simulation equipment, which is often used to simulate the aerodynamic torque load on the missile rudder or elevon actuators in the flight. The mathematical model of the electric dynamic load simulator is built using the physical modeling method. The influence of the rudder performance on the model was considered, and modeled it as the disturbance channel in the model. The electric dynamic load simulator is a typical coupled system. Under the different simplification, the validity of the model is verified by the actual experiment.

PRELIMINARY DESIGN OF DECISION SUPPORT SYSTEM FOR CHINESE SEADIKE SAFETY MANAGEMENT

A Decision Support System for Chinese Seadike Safety Management (DSS-CSSM) based on Geographic Information System (GIS) and database technology is initially proposed and designed in this paper. DSS-CSSM contains three major parts, which are fundamental information database, risk analysis module and hazard assessment module. Kinds of numerical and physical model methods can be selected and used in the modules. With integration of the fundamental information, analysis models and appropriate Human Computer Interaction(HCI), DSS-CSSM can be used to help people evaluate hazard losses of Chinese seadike and make some effective decisions.

Numerical Investigation for Heat Transfer of Supercritical CO2 Cooled in a Vertical Circular Tube

Convective heat transfer of supercritical CO2 cooled in a vertical circular tube has been numerically investigated by using the computational fluid mechanics code FLUENT. The objectives of this paper are to predict the heat transfer coefficient and to study the supercritical convective heat transfer of CO2 under uniform heat flux. Simulation starts with four cases, including a physical model, mathematical model, mesh independency, and solution method. Based on the mesh size of 80 × 500 in the radial and axial directions with near-wall resolution of less than 1, the low Reynolds number turbulence model proposed by Lam and Bremhorst (LB) model is adopted to investigate the heat flux effect, buoyancy effect on flow direction, and buoyancy effect on fluid flow. The results show that the LB low-Reynolds-number turbulence model agrees well with the experimental data. Buoyancy effect significantly affects the fluid flow and heat transfer characteristics in turbulent flow, which enhances heat transfer in upward flow, and impairs it in downward flow.

Dynamic stress and deformation of a layered road structure under vehicle traffic loads: Experimental measurements and numerical calculations

The study of stress and deformation of a road pavement–subgrade system under vehicle traffic loads is one of the most important areas in the field of transportation. In this paper, a physical model with all the road structure layers was built to study the dynamic behaviour of the layered pavement–subgrade system. Experiments were performed to determine the stresses, elastic deformations and irreversible permanent deformations at different depths to better understand the dynamic behaviour of a portion of a pavement–subgrade system. According to the physical model, the transmission and reflection matrices (TRM) method was used, and the general solutions for the stresses and displacements of the layered system subjected to dynamic double-circular loads at its surface were obtained. Numerical results in the space domain were derived by performing the inverse Hankel’s transform and were used to compare its results with the experimental measurements. The agreement between the numerical and the experimental results was good, which indicates that the TRM method is useful in predicting the stresses and elastic deformations of a multi-layered road structure. Moreover, the stresses and elastic deformations were analysed for different properties of the structure using numerical computation.

Global modeling of nonlinear circuits using the finite-difference Laguerre time-domain/alternative direction implicit finite-difference time-domain method with stability investigation

This paper describes a new unconditionally stable numerical method for the full-wave physical modeling of semiconductor devices by a combination of the finite-difference Laguerre time-domain (FDLTD) and alternative direction implicit finite-difference time-domain (ADI-FDTD) approaches. The unconditionally stable method by using FDLTD scheme for the electromagnetic model and semi-implicit ADI-FDTD approach for the active model leads to a significant decrease in the full-wave simulation time. Numerical simulations of an example transistor and a power amplifier show the efficiency of presented method for the full-wave simulation of mm-wave active circuits. Copyright © 2012 John Wiley & Sons, Ltd.

Physical Field Evaluation Model of High Speed Ball-End Milling Hardened Steel

Based on the experiment of high speed ball-end milling hardened steel, investigated the distribution characteristics of cutting force and cutting heat and wearing character of cutter, and set up analysis model of cutter physical field. Using failure criterion and safety margin of cutter, founded physical field evaluation model of high speed ball-end milling cutter. By means of physical field analysis and experiment, explored the influence of cutting parameters on cutting property during cutter wear. Results indicate that the method of safety margin and physical field evaluation model can evaluate cutting property of cutter effectively, the impact of feed per tooth on physical field and safety margin is noticeable, and high speed and small feed are helpful to improve safety margin and cutting performance of cutter.

The Influence of Solid Wall-Fluid Molecular Interaction on Transport Properties of Gases in a Mini/micro Channel

The physical model and analytical method are put forward for considering the molecular interaction between solid wall and gas fluid when dealing with convective heat transfer in macro/mini/micro channels based on the boundary layer theory concept, the molecular kinetic theory of gases, structural chemistry and continuum hypothesis. The influence rule of wall-fluid intermolecular forces to the transport properties of gases located in boundary layer region is studied applying proposed models. The gas density variation distribution equation including the wall-fluid molecular interaction is derived with continuum media integral approach. The theoretical results show that the fluid diffusion is independent of the wall-fluid interaction but visosity and heat conductivity not. According to the gas molecular density distribution function and molecular dynamics, new formulae were developed for calculating viscidity coefficient and thermal conductivity with wall-fluid interacting effect for a fluid. The research results provide scientific reference for further study and exploitation on fluid flow and heat transfer of mini/micro channels. In addition, the formulae offered in this paper to compute the transport properties of gases are also suitable for fine analysis of boundary layer in macro-scale channels.

Meso-scale oriented simulation towards virtual process engineering (VPE)—The EMMS Paradigm

With the dramatic development of computational science and technology, computer simulation is playing an increasingly important role in scientific research and engineering practice, and is believed to bring about a profound revolution to the mode and means of these activities. For chemical engineering, it will promote the transition from an experience-and-experiment-based research and development mode to the one based on virtual process engineering (VPE). However, such a revolution still requires tremendous improvements in the Accuracy of physical modeling and numerical methods, the Capability of the computing hardware and software, and the Efficiency of the simulation activities, or in short, ACE. This article will systematically review the 3-decade endeavors at IPE, CAS (Institute of Process Engineering, Chinese Academy of Sciences) on upgrading ACE by establishing a multi-scale computing paradigm focusing on meso-scale structures. We also report recent developments in this direction with projections on future work. Meso-scales refer to the intermediate scales at which the discrete elements in a system interact to shape the global behavior of the system. Reasonable description of the structures at such scales is a bottleneck for reliable and accurate modeling of global behaviors. To address this problem, we started from gas–solid flow by proposing the energy minimization multi-scale (EMMS) model to quantify the hydrodynamics of meso-scale structures in gas–solid fluidization. This model, that is, its stability condition, was thoroughly analyzed and verified with the pseudo-particle modeling (PPM) method. Other systems, such as turbulence and gas–liquid flow, were then studied following the same strategy, revealing the ubiquity of stability conditions for meso-scale structures as a result of the compromise among different dominant mechanisms, and leading to a generalized model mathematically formulated as a multi-objective variational (MOV) problem. Meanwhile, along with wider industrial applications of the EMMS-based simulation methods, common features were recognized that ACE requires structural consistency among the simulated system, the physical model, the numerical software and the computing hardware under the umbrella of MOV, which we have named as the EMMS Paradigm. The EMMS Paradigm was first implemented from the software level using traditional computing hardware to achieve Accuracy. Since 2007, with the development of general-purpose GPU (graphic processing unit) computing, CPU (central processing unit)–GPU hybrid computing was deployed to implement the Paradigm from the hardware level, boosting the Capability to Petaflops range. In applying the Paradigm to the development of an industrial petro-chemical process (maximizing iso-paraffins, MIP), enabling technologies such as pre- and post-processing, error-tolerance, network-based computing and seamless integration of different simulation methods are now under development, which will greatly improve the Efficiency. A demonstration virtual laboratory featuring the comparison and interaction of online measurement and real-time computing is under construction. With these endeavors, an industrial process could be simulated globally in almost real-time, and different levels of details could be traced from the global distribution of flow parameters in a reactor to the inner-channels of catalytic particles at a perceivable evolution speed. The realization of VPE is, therefore, in the foreseeable future.

Guest Editor's Introduction: Special Section on the Joint Conference on Geometric Design and Solid and Physical Modeling (GDSPM)

THE 2009 SIAM/ACM Joint Conference on Geometric Design and Solid and Physical Modeling (GDSPM), which was a federation of the 2009 SIAM Conference on Geometric Design and the 2009 ACM Symposium on Solid and Physical Modeling, was held in San Francisco, CA, from 5 October to 8 October 2009. The goal of the conference was to present theoretically well-founded new methods for geometric and physical modeling that have useful practical applications. In response to the call for papers of the conference, 85 papers were submitted on many aspects of geometric and physical modeling, and their application in design, analysis, manufacturing, biomedicine, digital entertainment, and other areas. All papers were assessed by five reviewers, usually a member from the international program committee. A total of 24 papers were selected for plenary presentation and publication as full papers, and an additional 18 papers for poster presentation and publication as short papers. All papers appeared in the proceedings of the conference, published by ACM. From the full papers, we selected the four papers here for extended publication in this special section. The papers were chosen on the basis of their high quality and their suitability for the readership of IEEE Transactions on Visualization and Computer Graphics (TVCG). All the papers were revised and expanded from the version that appeared in the conference proceedings, and all papers went through further review and revision. We are very pleased with the quality of the resulting papers, and we believe they will be of interest to a wide audience. “Model Synthesis: A General Procedural Modeling Algorithm,” by Paul Merrell and Dinesh Manocha, presents a method for automatically generating geometric models that resemble those provided by an input example. The method examines input models to determine a variety of geometric constraints (such as connectivity and spacing between various features) that help describe the given shape. These constraints are then used in a procedural method to generate new models that follow the same constraints. As a result, a wide variety of new models that resemble the input model can be created very easily, which should be beneficial for numerous graphics applications that require extensive geometry creation with limited user input. “GPU-Accelerated Minimum Distance and Clearance Queries,” by Adarsh Krishnamurthy, Sara McMains, and Kirk Haller, presents a number of fundamental algorithms for computing distance queries for NURBS surfaces. Bounded distance measures are computed for axis-aligned bounding boxes rapidly using the GPU. This allows one to quickly compute the nearest point on a NURBS surface, given a point in space, or to compute clearance between two NURBS models. The paper provides a significant performance increase for fundamental geometric queries that form the basis for several operations in CAD and other applications. “Voronoi-Based Curvature and Feature Estimation from Point Clouds,” by Quentin Merigot, Maks Ovsjanikov, and Leonidas Guibas, an extension of the best paper award winner at the conference, presents a method for estimating certain surface properties directly from point cloud data. In particular, normals, principal curvatures, and sharp features can be computed on point clouds. Perhaps more importantly, theoretical guarantees on many of the computations are provided, including robustness to noise in the point sampling. This paper provides a significant advance in making use of point cloud data sets. “Ball-Morph: Definition, Implementation, and Comparative Evaluation,” by Brian Whited and Jaroslaw (Jarek) Rossignac, describes three methods in detail for computing morphs between pairs of certain planar curves. These methods are compared to several standard morphing methods, and it is shown that the proposed morphs consistently provide better performance on particular metrics. This paper offers a significant improvement to 2D morphing, and should be of particular interest in animation applications. We believe that these four papers are strong representatives of the papers presented at the conference, and hope that you will enjoy reading them. We thank all the authors of the papers and the reviewers for their work in ensuring the high quality of these final papers, along with Dr. Tom Ertl and the TVCG staff for their help in seeing this special section published.

Local characteristics of cross-unit contamination around high-rise building due to wind effect: Mean concentration and infection risk assessment

In this present work, the characteristics of hazardous gas dispersion and possible cross-unit contamination around a complex-shaped high-rise residential building due to wind effect are thoroughly studied using physical modeling method. Experiments were performed in a boundary layer wind tunnel for a 1:30 scale model that represented a 10-story residential building in prototype. Tracer gas, simulating exhausted room air, was continuously released from different floor levels, and its concentrations on the adjacent envelope surfaces were measured using fast flame ionization detectors. The mean concentration fields were reported and analyzed under different configurations during the experiment to consider the effects on pollutant dispersion behavior due to changes in source position and approaching wind condition, with the main emphasis on the differences between open-window and closed-window conditions. In particular, the measured concentration fields were further examined from a practical point of view, with respect to hazard assessment. Understanding these hazardous plume dispersion features is useful for employing effective intervention strategies in modern residential building environment in case of hazardous substance release. The study on this physical process is not only helpful to reduce the hazardous effect of routine release of harmful pollutant near the building, but also useful for the purpose of prevention and control of accidental infectious diseases outbreak.

CATHARE-3: A new system code for thermal-hydraulics in the context of the NEPTUNE project

After a thorough analysis of the industrial needs and of the limitations of current simulation tools, EDF and CEA (Commissariat à l’Energie Atomique) launched the NEPTUNE Project in 2001 (see Guelfi et al., 2007) with the support of AREVA-NP and IRSN. The NEPTUNE activities include software development, research in physical modeling and numerical methods, development of advanced instrumentation techniques and new experimental programs. Four different simulation scales were addressed including DNS (Direct Numerical Simulation), CFD in open medium (Computational Fluid Dynamics), component (subchannel-type analysis) and system (reactor modeling) scales. In 2006 CEA, EDF, AREVA-NP and IRSN defined the strategy for the system scale of NEPTUNE and the CATHARE-3 development was launched. The main objectives are: • advanced physical modeling of two-phases flows, mainly by using multi-field and turbulence models, • improved 3D modeling by the use of fine and non conforming structured meshes, • generalized coupling capabilities with other thermal-hydraulic scales and with other disciplines (core physics, structural mechanics, …), • extension of the applicability to new Gen IV reactors (Sodium Cooled Fast Breeder Reactors, Gas Cooled Reactors, Supercritical Light Water Reactors), • a true object-oriented code architecture. At the same time CATHARE-3 is in continuity with the CATHARE-2 code which is the current industrial version of CATHARE and internationally used for nuclear power plant safety analysis, in simulators and in coupled simulation tools. The road map of these two codes will allow a smooth transition from CATHARE-2 to CATHARE-3 for all users. This paper gives an overview of the choices made for the development of CATHARE-3 including new physical models, validation strategy and experimental programs, numerical improvements, enhanced coupling capability and software architecture evolution. The current status of the project as well as the overall schedule will be presented.

Modeling of blood microcirculation processes with allowance for pulse pressure oscillations

Processes of unsteady transcapillary exchange in hemodynamics with allowance for plasma motion in the interstitial space are studied by methods of physical and mathematical modeling. The presence of pulse oscillations of pressure in the network of capillaries is responsible for separation of filtration and re-absorption through capillary walls in space and time. General and specific properties of functioning of the arteriole, intermediate, and venule segments of the capillary network in exchange properties are demonstrated. Pressure oscillations are found to enhance transcapillary exchange.

Component Mode Modification Technique for Vibration Control

In the present paper, a vibration mode modification method when the dynamic characteristics of the vibration system change by assembly is proposed. When the dynamic characteristics change, component mode synthesis (CMS) is widely used. However, CMS is not suitable for vibration control. Therefore, the present paper proposes a component mode modification technique for vibration control problem. The vibration modes are modified using component modes for constructing a reduced-order model. In this method, vibration modes are modified using static correction modes (attachment modes). Using these modes, orthogonalization is performed by subspace iteration. First, the concept of vibration mode modification is proposed. This concept is then applied to the proposed modeling method, which is referred to as the extended reduced-order physical modeling method. Finally, the proposed method is examined through dynamic responses of an elastic vehicle. Using the elastic vehicle, a single lane change test and simulation are carried out.

206205 弾性搭載物・除振台システムの低次元化物理モデル作成法を用いたモデリングと制御(一般02 機械力学・制御工学5)

206205 弾性搭載物・除振台システムの低次元化物理モデル作成法を用いたモデリングと制御(一般02 機械力学・制御工学5)

Physical human model eye and methods of its use to analyse optical performance of soft contact lenses

A bench-top physical model eye that closely replicates both anatomical and optical properties of an average human eye was designed and constructed. The cornea was sourced from a flouro-polymer with refractive index (RI) of 1.376 and crystalline lenses were made of Boston RGP polymers, EO and Equalens II, with an equivalent RI of 1.429 and 1.423 respectively. These materials served to make crystalline lens components of different age groups and accommodative states. De-Ionized water, with RI of 1.334 represented both aqueous and vitreous humor. The complementary metal-oxide sensor of a PixelLink digital camera with a resolution of 5MP and a 2.2 microm pixel pitch, hosted on a motor-base, served as the 'acting' retina. The translation and rotary functions of the motor-base facilitated the simulation of different states of ametropia and assessment of peripheral visual function, respectively. We validated one of its configurations to suit normal viewing conditions and results from the on and off-axis optical quality measurements are presented. As a demonstration of potential practical uses, several corrective soft contact lenses were placed on the model eye and their optical performance evaluated.

Numerical investigation of cooling heat transfer to supercritical CO 2 in a horizontal circular tube

Cooling heat transfer to supercritical CO 2 in a horizontal circular tube has been numerically investigated using CFD code FLUENT in the present study. The purpose is to provide detailed information on heat transfer behavior which is hard to be observed in experimental studies and to help to better understand the heat transfer mechanism. Simulation starts with five key issues, including physical model, mathematical models, mesh independency, boundary conditions and solution methods. The results demonstrate that almost all models are able to reproduce the trend of heat transfer characteristics qualitatively, and LB low Re turbulence model shows the best agreement with the experimental data, followed by standard k– ɛ model with enhanced wall treatment. After the validation, further studies are discussed on velocity and turbulence fields, buoyancy effect, and heat transfer mechanism. It concludes that buoyancy significantly affects the turbulent flow, and evidently enhances the cooling heat transfer of supercritical CO 2, especially in the vicinity of pseudo-critical point. The mixed convection is the main heat transfer mechanism during supercritical CO 2 cooling process.

Control Effects of Baffle on Combustion Instability in a LOX/GH2 Rocket Engine

The combustion instability encountered unexpectedly in hot-firing tests of the YF-960 liquid oxygen/gaseous hydrogen (LOX=GH2) rocket engine was numerically researched. Here, the emphasis was on evaluating the control effects of two kinds of baffle configurations on combustion instability. The integrated physical model and numerical method were presented to solve the turbulent, three-dimensional, two-phase, and full-size LOX=GH2 rocket combustion process. The dominant oscillation frequency characteristics that appeared in the hot-firing tests were reproduced andconfirmedfirst,which validated the computationalfluiddynamics code to a certain extent. Thebaffle effects were investigated by the developedmass flow flux perturbingmodel. Results show that the control effect of the hub-and-six-blade baffle on the one-order tangential-mode oscillation frequency of 5800 Hz is better than that of the hub-and-three-blade baffle. Although the two kinds of baffles have similar effects on the radial-mode instability, the control effect is better fordamping the5800Hzoscillation than the2900Hzoscillation.This researchhasprovided direct design data for engineers, and it is valuable in further understanding the baffle-eliminating mechanisms.

Object-oriented Physical Modeling and Simulation of Fuel Cell Vehicle Powertrain

Fuel cell vehicle (FCV) is the focus of new energy vehicles research, in which the study of the powertrain is one of the crucial. This paper introduces the structure and working principle of the FCV powertrain, and analyses the critical powertrain components. According to complex and multi-domain characteristics of the powertrain, this paper presents an object-oriented modeling language to unify the physical modeling method and establish the physical model of FCV powertrain and the critical components base upon Maplesim platform. Using combined simulation based on Maplesim and Simulink and the results show the effectiveness of the model.

Physical modelling of pile penetration in clay using transparent soil and particle image velocimetry

A small-scale physical modelling method was developed to study the movement of clay during pile installation. The clay was simulated using a mixture of amorphous silica and mineral oil, which becomes almost transparent when the refractive indices of the oil and the silica are well matched. After adding reflective particles and consolidating the mixture in a transparent container, cylindrical model piles were driven vertically at the centre. A vertical section aligned with the pile centreline was illuminated by a laser light sheet, and a sequence of digital images was recorded. These were analysed using particle image velocimetry, and the complete displacement distribution during the pile installation was obtained. Notwithstanding some discrepancies at shallow depths, the observed displacements generally showed fairly good agreement with the theoretical predictions of the shallow strain path method (SSPM) once the effect of some soil trapped beneath the flat pile tip was taken into account. Normalisation of the horizontal and vertical components of movement employing both the pile length and radius, based on SSPM theory, was shown to be valid. The normalised vertical displacement contours were similar to those published by previous researchers. The results of this study could be used to assess the impact of disturbance due to pile installation on, for example, buried services or archaeology.

Formation and consolidation of hummocks on the Arctic seas’ one-year ice cover as a result of laboratory and field researches

Structural-genetic types of hummocks formed on the Arctic seas’ ice cover are considered. A method of the laboratory physical modeling was used for understanding kinematic schemes of the hummocks’ formation processes. A methodology of computation of the hummock consolidation intensity for different hummocks’ structural types was proposed. The performed computations showed good coherence of the laboratory experiments results and field studies of hummocks’ structure in the Barents and Kara seas.