scholarly journals Stable marker-particle method for the Voronoi diagram in a flow field

2007 ◽  
Vol 202 (2) ◽  
pp. 377-391 ◽  
Author(s):  
Tetsushi Nishida ◽  
Kokichi Sugihara ◽  
Masato Kimura
Keyword(s):  
Flow Field ◽  
Voronoi Diagram ◽  
Particle Method ◽  
Marker Particle

Flow/Acoustic Mechanisms in Three-Dimensional Vortices Undergoing Sinusoidal-Wave Instabilities

2007 ◽  
Author(s):  
Wenhua Li ◽  
Z. C. Zheng ◽  
Ying Xu
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Vortex Pair ◽  
Particle Method ◽  
Acoustic Signals ◽  
Short Wave ◽  
Vortical Flow ◽  
Vortex Particle Method ◽  
Structure Changes ◽  
Wave Instabilities

It has been identified that vorticity in a vortex core directly relates to the frequency of a significant sound peak from an aircraft wake vortex pair where each of the vortices is modeled as an elliptic core Kirchhoff vortex. In three-dimensional vortices, sinusoidal instabilities at various length scales result in significant flow structure changes in these vortices, and thus influence their radiated acoustic signals. In this study, a three-dimensional vortex particle method is used to simulate the incompressible vortical flow. The flow field, in the form of vorticity, is employed as the source in the far-field acoustic calculation using a vortex sound formula that enables computation of acoustic signals radiated from an approximated incompressible flow field. Cases of vortex rings and a pair of counter-rotating vortices are studied when they are undergoing both long- and short-wave instabilities. Both inviscid and viscous interactions are considered and effects of turbulence are simulated using sub-grid-scale models.

Introduction of Virtual Structural Boundary for Collision Force Analysis of Tsunami Drifting Objects in Particle Method

2019 ◽  
Author(s):  
Yasuhiro Aida ◽  
Koichi Masuda ◽  
Tomoki Ikoma ◽  
Hiroaki Eto
Keyword(s):  
Boundary Condition ◽  
Analytical Solution ◽  
Flow Field ◽  
Particle Method ◽  
Force Analysis ◽  
Fluid Force ◽  
Virtual Boundary ◽  
Collision Force ◽  
Structural Boundary ◽  
Particle Boundary

Abstract One of the reasonable methods to analyze the collision force of a tsunami drifting object against a structure is a particle method. However, when both the structure and the drifting body are composed of particles, there are various problems such as particles of the collision object slipping through particles of the structure. Therefore, the authors have constructed a particle method - analytical solution hybrid method which can analyze the collision force of a tsunami drifting object to an elastic member by constructing a structure as a boundary condition acting on a drifting object. However, since this boundary was introduced as a virtual boundary that acts only on drifting particles, the collision force of the tsunami drifting object to the structure can be analyzed, but the fluid force can’t be analyzed. Therefore, in this study, in addition to the boundary condition as the structure, we further reconstructed the collision force and the fluid force as a method that can analyze the collision force and the fluid force simultaneously by setting the mirror particle boundary condition for the fluid particle. By developing this method, it became possible to calculate the collision force in a situation where a stagnation point occurs like a flow field at the front of the wall type structure, and the drifting object is decelerating.

Multiple bifurcations of the flow over stalled airfoils when changing the Reynolds number

2018 ◽  
Vol 846 ◽  
pp. 356-391 ◽  
Author(s):  
E. Rossi ◽  
A. Colagrossi ◽  
G. Oger ◽  
D. Le Touzé
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Complex Dynamics ◽  
Particle Method ◽  
Micro Air Vehicles ◽  
Suction Side ◽  
Two Dimensional ◽  
Vortex Particle Method ◽  
Critical Configurations ◽  
Lift And Drag

In the present study, the sudden changes of the flow field past stalled airfoils for small variations of the Reynolds number are investigated numerically. A vortex particle method has been used for the simulations in a two-dimensional framework. The most critical configurations found with this solver are verified through the comparison with the solution given by a mesh-based finite volume solver. The airfoils considered are the NACA0010 and a narrow ellipse with the same thickness. The angle of attack is fixed to $\unicode[STIX]{x1D6FC}=30^{\circ }$ for which complex dynamics of the flow can take place in the different viscous regimes inspected. The Reynolds number ranges between $Re=100$ and $Re=3000$ and, within this interval, numerous bifurcations of the solution are observed in terms of mean lift and drag coefficients, Strouhal number and downstream wake. An analysis of these bifurcations is provided and links are made between the wake structures observed. On this base the flow patterns can be classified in different modes similarly to the analysis by Kurtulus (Intl J. Micro Air Vehicles, vol. 7(3), 2015, pp. 301–326; vol. 8(2), 2016, pp. 109–139). A discussion of the vortical evolution of the flow in the vicinity of the suction side of the airfoil is also provided.

scholarly journals A line element algorithm for curve flow problems in the plane

1993 ◽  
Vol 35 (2) ◽  
pp. 244-261 ◽  
Author(s):  
Stephen Roberts
Keyword(s):  
Flame Propagation ◽  
Mean Curvature Flow ◽  
Line Element ◽  
Particle Method ◽  
Normal Velocity ◽  
Flow Problems ◽  
Curve Flow ◽  
Marker Particle ◽  
Line Elements ◽  
Element Algorithm

AbstractIn this paper we shall describe a numerical method for the solution of curve flow problems in which the normal velocity of the curve depends locally on the position, normal and curvature of the curve. The method involves approximating the curve by a number of line elements (segments) which are only allowed to move in a direction normal to the element. Hence the normal of each line element remains constant throughout the evolution. In regions of high curvature elements naturally tend to accumulate. The method easily deals with the formation of cusps as found in flame propagation problems and is computationally comparable to a naive marker particle method. As a test of the method we present a number of numerical experiments related to mean curvature flow and flows associated with flame propagation and bushfires.

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