• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3415-3421
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• 2022

This paper is aimed to find out the impact of the geometrical parameters, mainly the radius and the height of a cylinder, on the SGEMP response including the famous scaling law in the classical cylinder model using a homemade PIC code UNIPIC-3D. We computed the electric fields at the center and at the edge on the emission head face with different radii and heights under normal X-rays incidence. The results show that the electric field will increase with the radius but decrease with the height. We analyze the scaling law that links the electric field product and fluence product, and whereafter an irreconcilable contradiction raises when the radius is changeable, which limits the application range of the scaling law. Moreover, the field-height-radius relation is found and described by a combination of logarithmic and minus one-quarter numerical fitting law firstly. Particle and magnetic field distributions are used to explain all the behaviors of the fields reasonably. All the findings will assist the evaluation of SGEMP response in spacecraft protection.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제32권1호
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• pp.35-42
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• 2008

Instrumented sharp indentation test is a well-directed method to measure hardness and elastic modulus. The sharp indenter such as Berkovich and conical indenters have a geometrical self-similarity in theory, but the self-similarity ceases to work in practice due to inevitable indenter tip-blunting. In this study we analyzed the load-depth curves of conical indenter with finite tip-radius via finite element method. Using the numerical regression data obtained from Kick's law, we first confirmed that loading curvature is significantly affected by tip radius as well as material properties. We then established a new method to evaluate Young's modulus, which successfully provides the value of elastic modulus with an average error of less than 2%, regardless of tip-radius and material properties of both indenter and specimen.

• Advances in aircraft and spacecraft science
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• 제4권4호
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• pp.487-501
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• 2017

The main purpose of the paper is to analyze effect of geometrical parameters of the reentry capsules such as radius of the spherical cap, shoulder radius, back shell inclination angle and overall length on the flow field characteristics. The numerical simulation with viscous flow past ARD (Atmospheric Reentry Demonstrator), Soyuz (Russian) and OREX (Orbital Reentry EXperimental) reentry capsules for freestream Mach numbers range of 2.0-5.0 is carried out by solving time-dependent, axisymmetric, compressible laminar Navier-Stokes equations. These reentry capsules appear as bell, head light and saucer in shape. The flow field features around the reentry capsules such as bow shock wave, sonic line, expansion fan and recirculating flow region are well captured by the present numerical simulations. A low pressure is observed immediately downstream of the base region of the capsule which can be attributed to fill-up in the growing space between the shock wave and the reentry module. The back shell angle and the radius of the shoulder over the capsule are having a significant effect on the wall pressure distribution. The effects of geometrical parameters of the reentry capsules will useful input for the calculation of ballistic coefficient of the reentry module.

• Journal of the Society of Naval Architects of Korea
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• 제43권2호
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• pp.177-185
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• 2006

Cavitation is the dominant noise source of the marine vehicle. Of the various types of cavitation , tip vortex cavitation is the first appearance type of marine propeller cavitation and it generates high frequency noise. In this study, tip vortex cavitation behavior and noise are numerically investigated. A numerical scheme using Eulerian flow field computation and Lagrangian particle trace approach is applied to simulate the tip vortex cavitation on the hydrofoil. Vortex flow field is simulated by combined Moore and Saffman's vortex core radius equation and Sculley vortex model. Tip vortex cavitation behavior is analyzed by coupled Rayleigh-Plesset equation and trajectory equation. The cavitation nuclei are distributed and released in the vortex flow result. Vortex cavitation trajectories and radius variations are computed according to nuclei initial size. Noise is analyzed using time dependent cavitation bubble position and radius data. This study may lay the foundation for future work on vortex cavitation study and it will provide a basis for proper underwater propeller noise control strategies.

• Journal of applied mathematics & informatics
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• 제10권1_2호
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• pp.41-50
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• 2002

We provide local and semilocal theorems for the convergence of Newton-like methods to a locally unique solution of an equation in a Banach space. The analytic property of the operator involved replaces the usual domain condition for Newton-like methods. In the case of the local results we show that the radius of convergence can be enlarged. A numerical example is given to justify our claim . This observation is important and finds applications in steplength selection in predictor-corrector continuation procedures.

• East Asian mathematical journal
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• 제39권1호
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• pp.75-85
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• 2023

In this paper, a non-overlapping rectangular domain decomposition method is presented in order to numerically solve two-dimensional telegraph equations. The method is unconditionally stable and efficient. Spectral radius of the iteration matrix and convergence rate of the method are provided theoretically and confirmed numerically by MATLAB. Numerical experiments of examples are compared with several methods.

• Journal of Environmental Science International
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• 제18권3호
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• pp.271-281
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• 2009

In order to reduce the uncertainties and improve the air flow field, objective analysis using observational data is chosen as a method that enhances the reality of meteorology. To improve the meteorological components, the radius influence and nudging coefficient of the objective analysis should perform a adequate value on complex area for the objective analysis technique which related to data reliability and error suppression. Several numerical experiments have been undertaken in order to clarify the impacts of the radius influence and nudging coefficient of the objective analysis on meteorological environments. By analyzing practical urban ground conditions, we revealed that there were large differences in the meteorological differences in each case. In order to understand the quantitative impact of each run, the Statistical analysis by estimated by MM5 revealed the differences by the synoptic conditions. The strengthening of the synoptic wind condition tends to be well estimated when using quite a wide radius influence and a small nudging coefficient. On the other hand, the weakening of the synoptic wind is opposite.

• Mass Spectrometry Letters
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• 제6권3호
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• pp.59-64
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• 2015

Quadrupole ion trap mass analyzer with a simplified geometry, namely, the cylindrical ion trap (CIT), has been shown to be well-suited using in miniature mass spectrometry and even in mass spectrometer arrays. Computation of stability regions is of particular importance in designing and assembling an ion trap. However, solving CIT equations are rather more difficult and complex than QIT equations, so, analytical and matrix methods have been widely used to calculate the stability regions. In this article we present the results of numerical simulations of the physical properties and the fractional mass resolutions m/Δm of the confined ions in the first stability region was analyzed by the fifth order Runge-Kutta method (RKM5) at the optimum radius size for both ion traps. Because of similarity the both results, having determining the optimum radius, we can make much easier to design CIT. Also, the simulated results has been performed a high precision in the resolution of trapped ions at the optimum radius size.

• Journal of computational fluids engineering
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• 제4권3호
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• pp.21-27
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• 1999

In this paper, tile characteristics of flow resulting from the configurations of piston head and intake-port of the cylinder in a gasoline-direct-injection engine are investigated numerically. Calculations are carried out from intake process to the end of compression. GTT code which includes the third order upwind Chakravarthy-Osher TVD scheme and κ-ε turbulence model with the law of wall as a boundary condition. As a result, a piston head with a smaller radius of curvature and larger radius gives stronger reverse tumble. It is also shown that as the maximum tumble ratio increases by the configuration of the intake-port the tumble ratio at the end of compression stroke increases. It is concluded that flows at the end of compression stroke can be controlled by the optimum design of intake-port and piston head.

• International Journal of Safety
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• 제2권1호
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• pp.7-11
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• 2003

Structure of the counterflow nonpremixed flames were investigated by using Fire Dynamics Simulator(FDS) and OPPDIF to evaluate FDS for simulations of the diffusion flame. FDS, employed a mixture fraction formulation, were applied to the diluted axisymmetric methane-air nonpremixed counterflow flames. Fuel concentration in the mixture of methane and nitrogen was considered as a numerical parameter in the range from 20% to 100% increasing by 10% by volume at the global strain rates of $a_g = 20S^{-l} and 80S^{-1}$ respectively. In all the computations, the gravity was set to zero since OPPDIF is not able to compute the buoyancy effects. It was shown by the axisymmetric simulation of the flames with FDS that increasing fuel concentration increases the flame thickness and decreases the flame radius. The centerline temperature and axial velocity, and the peek flame temperature showed good agreement between the both methods.