scholarly journals Modeling of Coaxial Slot Waveguides Using Analytical and Numerical Approaches: Revisited

2012 ◽  
Vol 2012 ◽  
pp. 1-12
Author(s):  
Kok Yeow You ◽  
Jamaliah Salleh ◽  
Mohd Fareq Abd Malek ◽  
Zulkifly Abbas ◽  
Cheng Ee Meng ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Numerical Simulations ◽  
Frequency Domain ◽  
Analytical Methods ◽  
Fringing Field ◽  
Coaxial Waveguides ◽  
Physical Principles ◽  
Numerical Approaches ◽  
Slot Waveguides

Our reviews of analytical methods and numerical methods for coaxial slot waveguides are presented. The theories, background, and physical principles related to frequency-domain electromagnetic equations for coaxial waveguides are reassessed. Comparisons of the accuracies of various types of admittance and impedance equations and numerical simulations are made, and the fringing field at the aperture sensor, which is represented by the lumped capacitance circuit, is evaluated. The accuracy and limitations of the analytical equations are explained in detail. The reasons for the replacement of analytical methods by numerical methods are outlined.

Simulation of multiwavelength conditions in laser picosecond ultrasonics

SIMULATION ◽  
2021 ◽  
pp. 003754972199645
Author(s):  
Philippe Babilotte
Keyword(s):  
Numerical Simulations ◽  
Acoustic Signal ◽  
Acoustic Waves ◽  
Bulk Material ◽  
Deformation Field ◽  
Optical Pump ◽  
Pump And Probe ◽  
Oriented Object ◽  
Numerical Approaches ◽  
Picosecond Ultrasonics

Complete numerical simulations are given under SciLab® and MATLAB® coding environments, concerning propagative acoustic wavefronts, for laser picosecond ultrasonics under multiwavelength conditions. Simulations of the deformation field and its propagation into bulk material are given under different wavelength configurations for optical pump and probe beams, which are used to generate and to detect the acoustic signal. Complete insights concerning the dynamics of the acoustic waves are given, considering the absence of carrier diffusions into the material. Several numerical approaches are proposed concerning both the functions introduced to simulate the wavefront ( Heaviside or error) and the coding approach (linear/vectorized/ Oriented Object Programming), under the pure thermo-elastic approach.

scholarly journals Feasibility Study on Oil Droplet Flow Investigations Inside Aero Engine Bearing Chambers: PDPA Techniques in Combination With Numerical Approaches

1995 ◽  
Author(s):  
A. Glahn ◽  
M. Kurreck ◽  
M. Willmann ◽  
S. Wittig
Keyword(s):  
Numerical Methods ◽  
Flow Field ◽  
Flow Analysis ◽  
Field Analysis ◽  
Oil Droplet ◽  
Droplet Flow ◽  
Aero Engine ◽  
Secondary Air ◽  
Numerical Approaches ◽  
Engine Bearing

The present paper deals with oil droplet now phenomena in aero engine bearing chambers. An experimental investigation of droplet sizes and velocities utilizing a Phase Doppler Particle Analyzer (PDPA) has been performed for the first time in bearing chamber atmospheres under real engine conditions. Influences of high rotational speeds are discussed for individual droplet size classes. Although this is an important contribution to a better understanding of the droplet flow impact on secondary air/oil system performance, an analysis of the droplet flow behaviour requires an incorporation of numerical methods because detailed measurements as performed here suffer from both strong spatial limitations with respect to the optical accessibility in real engine applications and constraints due to the extremely time consuming nature of an experimental flow field analysis. Therefore, further analysis is based on numerical methods. Droplets characterized within the experiments are exposed to the flow field of the gaseous phase predicted by use of our well-known CFD code EPOS. The droplet trajectories and velocities are calculated within a Lagrangian frame of reference by forward numerical integration of the particle momentum equation. This paper has been initiated rather to show a successful method of bearing chamber droplet flow analysis by a combination of droplet sizing techniques and numerical approaches than to present field values as a function of all operating parameters. However, a first insight into the complex droplet flow phenomena is given and specific problems in bearing chamber heat transfer are related to the droplet flow.

Turbulent Flows with Drops and Bubbles: What Numerical Simulations Can Tell Us – Freeman Scholar Lecture

2021 ◽  
Author(s):  
Giovanni Soligo ◽  
Alessio Roccon ◽  
Alfredo Soldati
Keyword(s):  
Numerical Methods ◽  
Best Practices ◽  
Numerical Simulations ◽  
Turbulent Flows ◽  
Multiphase Flows ◽  
Simulation Analysis ◽  
Droplet Size Distribution ◽  
Limited Range ◽  
Numerical Resolution ◽  
Multi Scale

Abstract Turbulent flows laden with large, deformable drops or bubbles are ubiquitous in nature and in a number of industrial processes. These flows are characterized by a physics acting at many different scales: from the macroscopic length scale of the problem down to the microscopic molecular scale of the interface. Naturally, the numerical resolution of all the scales of the problem, which span about eight to nine orders of magnitude, is not possible, with the consequence that numerical simulations of turbulent multiphase flows impose challenges and require methods able to capture the multi-scale nature of the flow. In this review, we start by describing the numerical methods commonly employed and discussing their advantages and limitations, and then we focus on the issues arising from the limited range of scales that can be possibly solved. Ultimately, the droplet size distribution, a key result of interest for turbulent multiphase flows, is used as a benchmark to compare the capabilities of the different methods and to discuss the main insights that can be drawn from these simulations. Based on this, we define a series of guidelines and best practices that we believe important in the simulation analysis and in the development of new numerical methods.

scholarly journals Experimental and Numerical Research on Cylindrical Tubes under Outer Cylindrical Explosive Waves

2017 ◽  
Vol 2017 ◽  
pp. 1-10
Author(s):  
Sui Yaguang ◽  
Zhang Dezhi ◽  
Tang Shiying ◽  
Chen Bo
Keyword(s):  
Numerical Methods ◽  
Numerical Simulations ◽  
Explosive Loading ◽  
Important Application ◽  
Uniform Deformation ◽  
Collision Region ◽  
Explosive Wave ◽  
Cylindrical Tubes ◽  
Numerical Research ◽  
Microscopic Deformation

Cylindrical explosive loading has an important application in explosive working, researching on weapon damage, and explosive-driving load. This study uses experimental and numerical methods to study the response of long and thin tubes when subjected to cylindrical explosive loading. The flake-like charge and multipoint initiation technique were adopted to load cylindrical explosive waves. Experimental results showed that the method could produce uniform deformation in certain parts of the long tube, but partial spall injuries occurred after the explosion. The macroscopic and microscopic deformation of tubes were analyzed. Numerical simulations were conducted to investigate the detailed response of the tube subjected to a cylindrical explosive wave. The results indicate that the collision of explosive waves brought inconsistencies in pressure and velocity. The pressure and velocity in the collision region were significantly higher than those of other parts, which caused the collision region to be easily damaged.

scholarly journals Exact receptance function and receptance curvature of a clamped-clamped continuous cracked beam

2019 ◽  
Vol 41 (4) ◽  
pp. 349-361
Author(s):  
Nguyen Viet Khoa ◽  
Cao Van Mai ◽  
Dao Thi Bich Thao
Keyword(s):  
Numerical Simulations ◽  
Frequency Domain ◽  
Crack Detection ◽  
Harmonic Excitation ◽  
Second Derivative ◽  
Cracked Beam ◽  
Cracked Beams

The receptance function has been studied and applied widely since it interrelates the harmonic excitation and the response of a structure in the frequency domain. This paper presents the derivation of the exact receptance function of continuous cracked beams and its application for crack detection. The receptance curvature is defined as the second derivative of the receptance. The influence of the crack on the receptance and receptance curvature is investigated. It is concluded that when there are cracks the receptance curvature has sharp changes at the crack positions. This can be applied for the crack detection purpose. In this paper, the numerical simulations are provided.

scholarly journals Numerical simulation of minor losses coefficient on the example of elbows

2018 ◽  
Vol 180 ◽  
pp. 02093
Author(s):  
Smyk Emil ◽  
Mrozik Dariusz ◽  
Olszewski Łukasz ◽  
Peszyński Kazimierz
Keyword(s):  
Numerical Simulation ◽  
Numerical Methods ◽  
Numerical Method ◽  
Cross Section ◽  
Analytical Methods ◽  
Circular Cross Section ◽  
Experimental Methods ◽  
Loss Coefficient ◽  
Complicated Problem ◽  
Minor Losses

Determining of minor losses coefficient is very complicated problem. Analytical methods are often very difficult and experimental methods are very expensive and time-consuming. Consequently, the use of numerical methods seems to be a good solution, but there are no publications describing this issue. Therefore, the paper is describing the numerical method of determining the minor loss coefficient ξ on the example of elbows with circular cross-section.

A numerical framework for the approximate solution of fractional tumor-obesity model

2019 ◽  
Vol 10 (01) ◽  
pp. 1941008 ◽  
Author(s):  
Sadia Arshad ◽  
Dumitru Baleanu ◽  
Ozlem Defterli ◽  
Shumaila
Keyword(s):  
Immune Response ◽  
Approximate Solution ◽  
Numerical Methods ◽  
Numerical Simulations ◽  
Fractional Order ◽  
Response Rate ◽  
Stability And Convergence ◽  
Fractional Operators ◽  
High Caloric Diet

In this paper, we have proposed the efficient numerical methods to solve a tumor-obesity model which involves two types of the fractional operators namely Caputo and Caputo-Fabrizio (CF). Stability and convergence of the proposed schemes using Caputo and CF fractional operators are analyzed. Numerical simulations are carried out to investigate the effect of low and high caloric diet on tumor dynamics of the generalized models. We perform the numerical simulations of the tumor-obesity model for different fractional order by varying immune response rate to compare the dynamics of the Caputo and CF fractional operators.

scholarly journals Note on the Sensitivity of Simulated Solutions of the Nonlinear Singularly Perturbed Dynamical System on the Used Different Rewriting into a System of First Order Differential Equations

2016 ◽  
Vol 24 (39) ◽  
pp. 51-55
Author(s):  
Vladimír Liška ◽  
Zuzana Šútova ◽  
Dušan Pavliak
Keyword(s):  
Dynamical System ◽  
Numerical Methods ◽  
Differential Equations ◽  
Numerical Simulations ◽  
Numerical Scheme ◽  
Singularly Perturbed ◽  
First Order ◽  
First Order Differential Equations

Abstract In this paper we analyze the sensitivity of solutions to a nonlinear singularly perturbed dynamical system based on different rewriting into a System of the First Order Differential Equations to a numerical scheme. Numerical simulations of the solutions use numerical methods implemented in MATLAB.

Basin Tests and Numerical Simulations of Wake-Induced Oscillations of In-Line Risers in Subcritical/Critical Regime

2018 ◽  
Author(s):  
Vincent Levasseur ◽  
Charles Leca ◽  
Benjamin Rousse ◽  
Francois Pétrié
Keyword(s):  
Numerical Simulations ◽  
Industrial Design ◽  
Design Tool ◽  
Critical Regime ◽  
Incoming Flow ◽  
Numerical Approaches

This paper adresses Wake Induced Oscillations in the transition between subcritical and critical regime. Both experimental and numerical approaches are proposed and compared here to model tandem risers motion. The main purpose is to enlarge our insights of the behavior of different arrangements of risers in this very tricky range of incoming flow (Re ∈ [134,000; 300,000]) and to assess the CFD ability as an industrial design tool.

Surveying Computations: Backsight — Turning Point — Foresight

1983 ◽  
Vol 37 (4) ◽  
pp. 247-254
Author(s):  
Kresho Frankich
Keyword(s):  
Problem Solving ◽  
Numerical Methods ◽  
Approximation Theory ◽  
Analytical Methods ◽  
High Speed ◽  
Turning Point ◽  
Data Handling ◽  
Engineering Work ◽  
Electronic Computers ◽  
Digital Or

Surveying computations are an integral part of the surveying profession. Until only a few decades ago they were performed by logarithms, mechanical calculators and slide rules. Mathematical models had to be given in forms suitable for the computational means available to the profession. The invention of digital or high-speed electronic computers led to a revolution in data handling and problem solving practices. The application of modern computers and calculators in surveying necessitates a radical reorganization of scientific research and everyday engineering work. Analytical methods of computations have not lost their importance, although the domains of their applications have changed. Computers brought a variety of numerical methods which, together with approximation theory, have become the most important part of surveying computations.

Sign in / Sign up

Export Citation Format

Share Document