Numerical method for predicting transition in three-dimensional flows by spatial amplification theory

AIAA Journal ◽  
1992 ◽  
Vol 30 (8) ◽  
pp. 1972-1979 ◽  
Author(s):  
Tuncer Cebeci ◽  
Hsun H. Chen
Keyword(s):  
Numerical Method ◽  
Three Dimensional

scholarly journals The time domain numerical method of three-dimensional conductors including radiation with lumped parameter circuit

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Souma Jinno ◽  
Shuji Kitora ◽  
Hiroshi Toki ◽  
Masayuki Abe
Keyword(s):  
Numerical Method ◽  
Time Domain ◽  
Maxwell Equations ◽  
Three Dimensional ◽  
New Formalism ◽  
Vector Potentials ◽  
Lumped Parameter ◽  
Radiation Theory ◽  
Stable Solutions ◽  
The Time Domain

AbstractWe formulate a numerical method on the transmission and radiation theory of three-dimensional conductors starting from the Maxwell equations in the time domain. We include the delay effect in the integral equations for the scalar and vector potentials rigorously, which is vital to obtain numerically stable solutions for transmission and radiation phenomena in conductors. We provide a formalism to connect the conductors to any passive lumped-parameter circuits. We show one example of numerical calculations, demonstrating that the new formalism provides stable solutions to the transmission and radiation phenomena.

scholarly journals A Fast Two-Dimensional Numerical Method for the Wake Simulation of a Vertical Axis Wind Turbine

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 49
Author(s):  
Zheng Yuan ◽  
Jin Jiang ◽  
Jun Zang ◽  
Qihu Sheng ◽  
Ke Sun ◽  
...  
Keyword(s):  
Velocity Distribution ◽  
Numerical Method ◽  
Three Dimensional ◽  
Particle Method ◽  
Vortex Method ◽  
Vertical Axis ◽  
Two Dimensional ◽  
Vertical Axis Wind Turbine ◽  
Wake Effect ◽  
Array Design

In the array design of the vertical axis wind turbines (VAWT), the wake effect of the upstream VAWT on the downstream VAWT needs to be considered. In order to simulate the velocity distribution of a VAWT wake rapidly, a new two-dimensional numerical method is proposed, which can make the array design easier and faster. In this new approach, the finite vortex method and vortex particle method are combined to simulate the generation and evolution of the vortex, respectively, the fast multipole method (FMM) is used to accelerate the calculation. Based on a characteristic of the VAWT wake, that is, the velocity distribution can be fitted into a power-law function, a new correction model is introduced to correct the three-dimensional effect of the VAWT wake. Finally, the simulation results can be approximated to the published experimental results in the first-order. As a new numerical method to simulate the complex VAWT wake, this paper proves the feasibility of the method and makes a preliminary validation. This method is not used to simulate the complex three-dimensional turbulent evolution but to simulate the velocity distribution quickly and relatively accurately, which meets the requirement for rapid simulation in the preliminary array design.

A Greenwood-Williamson Model of Small-Scale Friction

2005 ◽  
Vol 74 (1) ◽  
pp. 31-40 ◽  
Author(s):  
Reese E. Jones
Keyword(s):  
Numerical Method ◽  
Recursion Formula ◽  
Three Dimensional ◽  
Interfacial Friction ◽  
Small Scale ◽  
Analytical Estimate ◽  
Normal Loading ◽  
Proposed Model ◽  
Loading Case ◽  
Transition Length

A Greenwood and Williamson based model for interfacial friction is presented that incorporates the presliding transition phenomenon that can significantly affect small devices. This work builds on previous similar models by developing: an analytical estimate of the transition length in terms of material and surface parameters, a general recursion formula for the case of slip in one direction with multiple reversals and constant normal loading, and a numerical method for the general three-dimensional loading case. In addition, the proposed model is developed within a plasticity-like framework and is shown to have qualitative similarities with published experimental observations. A number of model problems illustrate the response of the proposed model to various loading conditions.

A Voxel-Based Numerical Method for Computing and Visualising the Workspace of Offshore Cranes

2015 ◽  
Author(s):  
Lars I. Hatledal ◽  
Filippo Sanfilippo ◽  
Yingguang Chu ◽  
Houxiang Zhang
Keyword(s):  
Numerical Method ◽  
Three Dimensional ◽  
Point Clouds ◽  
Third Party ◽  
Operational Performance ◽  
The Monte Carlo Method ◽  
Load Limit ◽  
Offshore Crane ◽  
Safe Working

Workspace computation and visualisation is one of the most important criteria in offshore crane design in terms of geometry dimensioning, installation feasibility and operational performance evaluation. This paper presents a numerical method for the computation and visualisation of the workspace of offshore cranes. The Working Load Limit (WLL) and the Safe Working Load (SWL) can be automatically determined. A three-dimensional (3D) rectangular grid of voxels is used to describe the properties of the workspace. Firstly, a number of joint configurations are generated by using the Monte Carlo method, which are then mapped from joint to Cartesian space using forward kinematics (FK). The bounding box of the workspace is then derived from these points, and the voxels are distributed on planes inside the box. The method distinguishes voxels by whether they are reachable and if they are on the workspace boundary. The output of the method is an approximation of the workspace volume and point clouds depicting both the reachable space and the boundary of the workspace. Using a third-party software that can work with point clouds, such like MeshLab, a 3D mesh of the workspace can be obtained. A more in-depth description and the pseudo-code of the presented method are presented. As a case study, the workspace of a common type of offshore crane, with three rotational joints, is computed with the proposed method.

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