Physical Modeling Method Research Articles

Influence of ferrimagnetic resonance on conversion of electromagnetic energy into mechanical one

In this paper it is obtained in zero approximation the algorithm of calculation of the force of electromagnetic wave propagation in rectangular waveguide applied to the ferrite sphere, placed into constant magnetic field by the method of physical modeling. It is researched the dependence of the force on a value of magnetic field intensity near ferromagnetic resonance. Theoretical results of the calculations were compared with experimental ones. At the resonance electromagnetic field with the power of 10W and the wave length of 3.2 cm influences on ferrite sphere with diameter of 3.55mmwith a force of 6 ± 0.5 µN. This force in enough for rotation of the suspension system of the reference ponderomotive wattmeter, fixed attached by means of braces or kerns. It allows to develop high-precision microwave wattmeters with enough mechanic strength for industrial application.

Real-time physical model of a grand piano soundboard on field programmable gate array hardware

A modern grand piano consists of over 10,000 singular parts and has a production cycle of approximately one year. This leads to the predicament that researching and changing acoustical features resulting from variable material properties of the instrument cannot be realized in a straightforward manner. The inevitable time delay as well as the variability of parameters makes a controlled research very hard, if not impossible. In this work, a system is presented that enables piano makers to change, simulate as well as auralise acoustical vibrations of a grand piano soundboard in real time using physical modelling methods on field programmable gate array (FPGA) hardware. This specific implementation focusses on synthesizing and simulating the vibrations of a geometrically complete model of a concert grand piano soundboard, including the ribs, the bass, and main bridge, realistic material parameters as well as coupled strings. It can be parametrized and controlled from a software GUI running on a personal computer. This implementation is part of a larger project aiming at modeling a complete grand piano in real-time for research, instrument making as well as purely musical applications.

Overview of the development and application of multi-time resolution source apportionment for particulate matters

Source apportionment is a key tool in establishing the relationship between the emission sources and receptors of particulate matters (PM), and it also plays a vital role on providing technical support for PM pollution control policy and its effective evaluation. Recently, a multi-time resolution PM source apportionment technique (MTR SA), based on the classic source apportionment method was developed as a new approach to explore the source, behavior and formation of PM during heavy pollution episodes, as well as to evaluate the effects of emergency control measures. In this study, three main methods of MTR SA are introduced, which based on the methods of receptor models combined with online observation of PM chemical composition. The atmospheric physical model method can be used to indentify the regional distribution and transporting characteristics of pollution sources. Combining with the classical source apportionment methods, the PM source apportionment in different air masses can be analyzed by this method, and it can investigate primary pollutants or tracers in different areas and industry sectors as well. Air quality model is a useful tool to simulate the regional air quality so as to identify the spatial distribution of the concentration of pollutants and to estimate the contribution of external pollution sources to the concentration of pollutants which can predict emission reduction in the future years. Methods of receptor model combined with online observation are more applicable to the classified quantitative analysis of the receptor particles. Atmospheric physical model and air quality model can not only provide high temporal resolution MTR SA, but also provide information about the spatial distribution and transmission pathways, which can offer decision-making basis for joint prevention and control of regional particles pollution. In order to meet the requirement of the current research and management demand, from three aspects of technology, science and application management, we put forward the future challenges of MTR SA technology. Although MTR SA technology has been applied in research and environmental management, intensive studies are still necessary to be verified, including the representativeness of the sampling results, the scientificity of calculation principles, the validity and accuracy of the simulation results, as well as the suitability and effectiveness of the method.

Linear System Identification in a Nonlinear Setting: Nonparametric Analysis of the Nonlinear Distortions and Their Impact on the Best Linear Approximation

This article addresses the following problems: 1) First, a nonlinearity analysis is made looking for the presence of nonlinearities in an early phase of the identification process. The level and the nature of the nonlinearities should be retrieved without a significant increase in the amount of measured data. 2) Next it is studied if it is safe to use a linear system identification approach, even if the presence of nonlinear distortions is detected. The properties of the linear system identification approach under these conditions are studied, and the reliability of the uncertainty bounds is checked. 3) Eventually, tools are provided to check how much can be gained if a nonlinear model were identified instead of a linear model. Addressing these three questions forms the outline of this article. The possibilities and pitfalls of using a linear identification framework in the presence of nonlinear distortions will be discussed and illustrated on lab-scale and industrial examples. In this article, the focus is on nonparametric and parametric black box identification methods, however the results might also be useful for physical modeling methods. Knowing the actual nonlinear distortion level can help to choose the required level of detail that is needed in the physical model. This will strongly influence the modeling effort. Also, in this case, significant time can be saved if it is known from experiments that the system behaves almost linearly. The converse is also true. If the experiments show that some (sub-)systems are highly nonlinear, it helps to focus the physical modeling effort on these critical elements.

PROBABILISTIC ZONING OF ADJACENT CATCHMENTS BY PHYSICAL MODELING

Now the probabilistic zoning of avalanche sites is being made either on the basis of the available field data, or using the mathematical and physical modeling of avalanche dynamics processes. The work purpose consisted in research of interaction and compiling probabilistic zoning maps of two adjacent avalanche sites by a physical modeling method. For the two adjacent sites № 9 and 10 on the slope of northern exposition ofTchegetMountain(Elbrus region,Caucasus) the model of this slope with the scale of 1: 2 500 was created. The model dimension is 0,82 × 1,1 ×0,57 m. This model was produced using the 4-mm plywood sheets imposed against each other. The model horizontals correspond to the10 mnatural ones. The model slope was also surfaced by thin gypsum lay and then varnished. The fine-grained sawdust (0.1 mm) with a natural friction angle of 43º has been chosen as the loose material modeling snow. A series of experiments on modeling avalanche releases from the two sites were carried out resulted in the measurements of avalanche deposit parameters such as run-out distance and length, width and thickness of deposits. The similarity criteria were used during the experiments. The morphometric features of adjacent sites interaction are revealed. The basic result of the carried out work will consist in the probabilistic zoning map of two adjacent sites № 9 and 10.

Physical modelling of pipe piles under oblique pullout loads using transparent soil and particle image velocimetry

A small-scale physical modelling method was developed to investigate the pile bearing capacity and the soil displacement around the pile using transparent soil and particle image velocimetry (PIV) technique. Transparent sand was made of baked quartz and a pore fluid with a matching refractive index. The physical modelling system consists of a loading system, a laser light, a CCD camera, an optical platform and a computer for image analyzing. A distinctive laser speckle was generated by the interaction between the laser light and transparent soil. Two laser speckle images before and after deformation were used to calculate the soil displacement field using PIV. Two pipe piles with different diameters under oblique pullout loads at angles of 0°, 30°, 45°, 60° and 90° were used in tests. The load-displacement response, oblique pullout ultimate resistances and soil displacement fields were then studied. The test results show that the developed physical modelling method and transparent soil are suitable for pile-soil interaction problems. The soil displacements around the pipe piles will improve the understanding on the capacity of pipe piles under oblique pullout loads.

Physical Modelling Of The Steel Flow In RH Apparatus

Abstract The efficiency of vacuum steel degassing using RH methods depends on many factors. One of the most important are hydrodynamic processes occurring in the ladle and vacuum chamber. It is always hard and expensive to determine the flow character and the way of steel mixing in industrial unit; thus in this case, methods of physical modelling are applied. The article presents the results of research carried out on the water physical model of RH apparatus concerning the influence of the flux value of inert gas introduced through the suck legs on hydrodynamic conditions of the process. Results of the research have visualization character and are presented graphically as a RTD curves. The main aim of such research is to optimize the industrial vacuum steel degassing process by means of RH method.

Developing methodology for model tests of floating platforms in low-depth towing tank

The paper presents two different methods of physical modeling of semi-submersible platform mooring system for research in low depth towing tank. The tested model was made in the scale of 1:100 resembling the “Thunder Horse” platform moored in the Gulf of Mexico at a depth of 1920m. Its mooring system consisted of 16 semi-taut mooring lines (chain-wire-chain) spaced star-shape and attached at the bottom to suction piles. The tests were performed in the towing tank of the Gdansk University of Technology (GUT). The tank depth is 1.5m and which is about 13.5 times less than that required for typical model tests. This required the development and use of non-standard methods of mooring for the model, which was adapted to the technical conditions existing in the laboratory and material possibilities. Numerical calculations and characteristics of static displacement of the model as a function of the external horizontal load were carried out for both anchoring systems. These characteristics were scaled to the natural conditions and compared with the calculated characteristics of the reference platform. The second method of modeling proved to be much more accurate.

Determination of Heat and Mass Transfer Efficiency on a Bubbling Plate with Account for Scale Transition

The efficiency of heat and mass transfer in the bubbling bed on the plate has been investigated with the use of the method of combined physical and mathematical modeling based on the representation of the physical process in the form of a combination of elementary phenomena having a hierarchy of scales that permits realizing a scale transition in designing a contact device. The mathematical modeling of the heat and mass transfer in the above bed is based on the idea that the structure of this bed is invariant with its size and the interaction of the phases in it. A parametric investigation of the interaction of various effects in the process of heat and mass transfer in the bubbling bed on the plate and their conjugation has been carried out on the basis of the variational formulation of the conservation laws. Examples of calculating the efficiencies of the heat and mass transfer processes on bubbling plates are given. The results of calculations were compared with the corresponding experimental data.

내부냉각노즐의 열차폐코팅을 위한 복합열전달 해석기법 연구

ABSTRACT In this study, two computational methodologies were compared to consider an effective conjugate heat transfer analysis technique for the cooled vane with thermal barrier coating. The first one is the physical modeling method of the TBC layer on the vane surface, which means solid volume of the TBC on the vane surface. The second one is the numerical modeling method of the TBC layer by putting the heat resistance interface condition on the surface between the fluid and solid domains, which means no physical layer on the vane surface. For those two methodologies, conjugate heat transfer analyses were conducted for the cooled vane with TBC layer having various thickness from 0.1 mm to 0.3 mm. Static pressure distributions for two cases show quite similar patterns in the overall region while the physical modeling shows quite a little difference around the throat area. Thermal analyses indicated that the metal temperature distributions are quite similar for both methods. The results show that the numerical modeling method can reduce the computational resources significantly and is quite suitable method to evaluate the overall performance of TBC even though it does not reflect the exact geometry and flow field characteristics on the vane surface.

Metaballs-based physical modeling and deformation of organs for virtual surgery

Prior research on metaballs-based modeling solely focuses on shape geometry and its processing for organic objects. This paper takes a different approach by exploring a new metaballs-based physical modeling method for digital organs that are imperative to support virtual surgery. We propose a novel hybrid physical model comprising both surface mesh and the metaballs which occupy organs' interior. The finer surface mesh with high-precision geometric information and texture is necessary to represent the boundary structure of organs. Through the use of metaballs, the organ interior is geometrically simplified via a set of overlapping spheres with different radii. This work's novelty hinges upon the integration of metaballs and position-based dynamics (PBD) which enables metaballs-based organs to serve as physical models and participate in dynamic simulation. For the metaballs construction, we develop an adaptive approach based on Voronoi Diagram for model initialization. Using global optimization, an electrostatic attraction model is proposed to drive the metaballs to best match with the organ's boundary. Using PBD, we devise a novel metaballs-based deformation algorithm, which preserves two local shape properties via constraints on Laplacian coordinates and local volume. To retain the organ's smooth deformation, we propose a new skinning method based on distance field, and it is employed to build the mapping between the metaballs and organ boundary. This metaballs-based deformation technique has already been integrated into a VR-based laparoscopic surgery simulator.

ANALYSIS OF APPLICATION OF VORTEX MOTION FOR FIRE-RESISTANT COATINGS ON THE VESSEL LINING

Using the methods of physical modeling, the study of the modes of expiration of vortex gas streams of the nozzles of different dimensions for different gas flow has been carried out.

Re-analysis of wind and slope effects on flame characteristics of Mediterranean shrub fires

During the past 20 years, study of wind–slope-aided wildland fire behaviour with experimental burns and physical modelling methods has increased. As part of their continuing study of fires in Mediterranean shrub, F. Morandini and X. Silvani reported experimental temperatures, heat fluxes, flame characteristics and other fire behaviour variables measured on five wind–slope-aided fires. Calculating convection numbers and several convective Froude numbers, the authors concluded that these dimensionless variables for their two wind-dominated fires did not satisfy criteria identified in previous studies for determining mechanisms of heat transfer during fuel preheating. The present paper describes a re-analysis of the data based on a triangular flame model and alternative definitions of flame tilt angle and height. This new analysis has shown that the influence of slope on the fire behaviour was not accounted for; thus, the conclusion of Morandini and Silvani is questionable. Of the five dimensionless variables studied using criteria in the literature, the squared flame height convective Froude number best describes modes of heat transfer to unburned fuels during the experimental fires. Though these results come indirectly from field measurements, they confirm the need to include slope effects in descriptions of wind–slope-aided fire behaviour.

Physical Μodelling as a Method to Estimate Plastic Flow Homogeneity During ECAP

A physical model method allows the estimation of the strain inhomogeneity in a material subjected to equal channel angular pressing. Copper samples which deformed with ECAP with a standard die-set showed significant inhomogeneity. The sample section was split into two sections, which have significantly different values of accumulated strain and, as a consequence in the microstructure. Application of a die-set with a special geometry modification allows uniform strain across the sample. A comparative analysis of physical modeling results, changes of microstructure and properties showed complete correlation. Known theoretical models of the ECAP process with deformation modes close to simple shear are analyzed.

Interannual differences in larval haddock survival: hypothesis testing with a 3D biophysical model of Georges Bank

AbstractThe ultimate goal of early life studies of fish over the past century has been to better understand recruitment variability. As evident in the Georges Bank haddock (Melanogrammus aeglefinus) population, there is a strong relationship between recruitment success and processes occurring during the planktonic larval stage. This research sought new insights into the mechanisms controlling the recruitment process in fish populations using biological–physical modeling methods together with laboratory and field data sets. We created the first three‐dimensional model of larval haddock on Georges Bank by coupling models of hydrodynamics, lower trophic levels, a single copepod species, and larval haddock. Interactions between feeding, metabolism, growth, vertical behavior, advection, predation, and the physical environment of larval haddock were quantitatively investigated using the coupled models. Particularly, the model was used to compare survival over the larval period and the sources of mortality in 1995 and 1998, 2 years of disparate haddock recruitment. The results of model simulations suggest that the increased egg hatching rates and higher food availability, which reduced starvation and predation, in 1998 contributed to its larger year‐class. Additionally, the inclusion of temperature‐dependent predation rates produced model results that better agreed with observations of the mean hatch date of survivors. The results from this biophysical model imply that food limitation and its related losses to starvation and predation, especially from hatch to 7 mm, may be responsible for interannual variability in recruitment and larval survival outside of the years studied.

Convection in a Limited Space Between Two Rotating Cylinders

Using the methods of physical and mathematical modeling, the pattern of flow and heat exchange in a rotating cylindrical chamber is investigated for the case where a radial temperature difference is realized. The mathematical model is formulated in the dimensional variables: current function – velocity vorticity –temperature in the cylindrical coordinates. The distributions of the current function and temperature isolines, which indicate the effect of the temperature difference and the chamber rotation velocity on the flow pattern and heat exchange are obtained. It is found out that an increase in the rate of rotation gives rise to an increased number of vortex structures in the plane and a significantly intensified flow in them, while an increase in the temperature difference results in a slightly higher circulation of the medium in the chamber only.

Physical modeling of seismic source generation in failure of fault asperities

A series of full-scale experiments was performed to study the influence of impact loads on the parameters of seismic vibrations initiated in variable friction. The study was conducted on a test setup Tribo which is a movable concrete slab modeling an allochthon on a rough plane of the Angara fault segment in Baikal region. Contact interactions of asperities in the slip zone were recorded using strain and load measuring equipment and four seismic stations Baykal-7HR widely used for recording earthquakes. The proposed physical modeling method and obtained results can be of interest for the development of new physical models of differently scaled sources of seismic energy dissipation in tectonic faults and can be useful for seismological studies, related data interpretation, and improvement of extended forecast of rock bursts and earthquakes.

Flow Simulation in a Labyrinth Seal

The paper studies the labyrinth seals of centrifugal compressor profit-proved stages using modern methods of numerical and physical modeling of the centrifugal compressor stages. A series of studies of the effect of operational and geometrical parameters on the maze, namely the quantities of the packed differential pressure, speed, fluid, geometric parameters of the seal, the magnitude of the eccentricity and radial clearance swirl flow at the inlet of a seal, etc. The technique of physical modeling seal has been specified. Research was conducted in two phases: numerical simulation using complex software Flow Vision and receiving data on a universal test bench to study the labyrinth seals.. A three-dimensional model of the labyrinth seal has been created, its verification by "known data has been held.. Integral characteristics in the form of distribution of flow velocities and pressures, flow visualization were obtained. Results of studies made ​​it possible to refine the workflow and introduce amendments to the known calculation formula for a more accurate calculation of leakage through the seal, subject to a number of additional factors that were not previously taken into account

Modelling of projectile penetration using transparent soils

This paper presents a novel physical modelling method to study projectile penetration problems. The method employs a recently developed transparent synthetic soil made of oil-saturated fused quartz, which represents the macroscopic behaviour of silica sand. Digital image correlation (DIC, also known as particle image velocimetry (PIV)) techniques were employed to quantify the response of granular soils to high-speed penetration, non-intrusively. A conical nose projectile made of steel was accelerated into a transparent soil target at an impact velocity of 13.6 m/s. Visualisation of the soil deformation was made possible by means of a novel seeded plane within the transparent soil model. The complete penetration event was recorded using a high-speed digital camera. The captured images were analysed using DIC, and further analysis of displacement trajectories and strains were also carried out using in-house algorithms.

EXPERIMENTAL STUDY OF THE PERFORMANCE OF FLOATING BREAKWATERS WITH HEAVE MOTION

Nowadays, the application of floating breakwaters in small or recreational harbors has found more popularity. These types of breakwaters are more flexible in terms of design, configuration and especially installation compared with fixed breakwaters. In the current study, the performance of floating breakwater (FBs) under regular waves was studied using the physical modeling method. For the modeling practice, a wave flume with a flap-type wave generator and progressive wave absorber was designed, constructed and used in order to investigate the performance of FBs. In this regard, a number of geometrical and hydrodynamic parameters were chosen including the degree of freedom, width variation, FB shapes (pontoon, T and types) and draft depth. In each scenario the water level variation was measured in three points along the flume. Based on the measured water levels transmission, reflection and energy dissipation coefficients were obtained. The effect of each parameter on the performance of FBs was investigated and the best configuration was proposed for further studies. According to the collected experimental data, the mathematical descriptions for calculating the transmission coefficient were also proposed.