THE JET HOLE-TONE OSCILLATION CYCLE SUBJECTED TO ACOUSTIC EXCITATION : A NUMERICAL STUDY BASED ON AN AXISYMMETRIC VORTEX METHOD(Sound and Nature)

2005 ◽  
Vol 2005 (0) ◽  
pp. 745-750 ◽  
Author(s):  
Mikael A. Langthjem ◽  
Masami Nakano
Keyword(s):  
Numerical Study ◽  
Vortex Method ◽  
Acoustic Excitation ◽  
Oscillation Cycle ◽  
Axisymmetric Vortex

scholarly journals A numerical study of flow around an impulsively started circular cylinder by a deterministic vortex method

1991 ◽  
Vol 233 ◽  
pp. 243-263 ◽  
Author(s):  
Chien-Cheng Chang ◽  
Ruey-Ling Chern
Keyword(s):  
Finite Difference ◽  
Circular Cylinder ◽  
Numerical Study ◽  
Vortex Method ◽  
Reynolds Numbers ◽  
Numerical Results ◽  
High Reynolds Numbers ◽  
Small Times ◽  
Axis Of Symmetry ◽  
High Reynolds

Impulsively started flow around a circular cylinder at various Reynolds numbers is studied by a deterministic hybrid vortex method. The key feature of the method consists in solving the viscous vorticity equation by interlacing a finite-difference method for diffusion and a vortex-in-cell method for convection. The vorticity is updated along the surface of the cylinder to satisfy the no-slip condition. The present method is basically different from previous applications of vortex methods, which are primarily in the context of random vortex algorithms. The Reynolds numbers of the flows under investigation range from 300 to 106. Numerical results are compared with analytical solutions at small times, and compared with finite-difference solutions and flow visualization results at relatively long times. Satisfactory agreement is found in the evolutions of the separation angles, wake lengths, surface pressure and drag coefficients, streamline patterns, and some velocities on the axis of symmetry behind the circular cylinder. The present hybrid vortex method is highly stable and suffers from little numerical diffusivity, yielding convincing numerical results for unsteady vortical flows at moderately high Reynolds numbers.

scholarly journals Effect of structural interaction on the aerodynamic properties

2020 ◽  
Vol 17 (3) ◽  
pp. 79-86
Author(s):  
R. N. Guzeev ◽  
◽  
E. S. Goloviznina ◽  
Keyword(s):  
Cross Sections ◽  
Mutual Influence ◽  
Numerical Study ◽  
Vortex Method ◽  
Discrete Vortex ◽  
Discrete Vortex Method ◽  
Structural Interaction ◽  
Cable Stayed Bridge ◽  
Aspect Ratios ◽  
Aerodynamic Properties

Effect of structural interaction on drag coefficient is considered. Numerical study is performed using discrete vortex method. There have been obtained dependences of the mutual influence of rectangular cross sections with different aspect ratios depending on the reduced distance between the cross sections, on their aerodynamics. The effect of structural interaction of cable-stayed bridge pylon legs is investigated on the examples of Golden Bridge and Russian Bridge in Vladivostok.

Numerical study of two-airfoil arrangements by a discrete vortex method

2020 ◽  
Vol 34 (1-2) ◽  
pp. 79-103 ◽  
Author(s):  
Thierry M. Faure ◽  
Laurent Dumas ◽  
Olivier Montagnier
Keyword(s):  
Numerical Study ◽  
Vortex Method ◽  
Discrete Vortex ◽  
Discrete Vortex Method

NUMERICAL STUDY OF THE FLOW AROUND SLENDER BODIES USING A LAGRANGIAN VORTEX METHOD

2017 ◽  
Author(s):  
Alex Bimbato ◽  
Luiz Antonio Alcântara Pereira ◽  
Carlos Felipe Carvalho Junior
Keyword(s):  
Numerical Study ◽  
Vortex Method ◽  
Slender Bodies

scholarly journals Vortex shedding from an impulsively started rotating and translating circular cylinder

1991 ◽  
Vol 233 ◽  
pp. 265-298 ◽  
Author(s):  
Chien-Cheng Chang ◽  
Ruey-Ling Chern
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Numerical Study ◽  
Vortex Method ◽  
Reynolds Numbers ◽  
Speed Ratio ◽  
Stagnation Points ◽  
Time Variations ◽  
Strong Competition ◽  
High Reynolds

A numerical study is made of the flow past an impulsively started rotating and translating circular cylinder using a hybrid vortex method. The Reynolds number (Re) ranges from 103 to 106 while the (counter-rotating) rotating-to-translating speed ratio (α) is increased from 0 to 2. It is found that three basic patterns of vortex shedding can be identified according to the behaviour of the stagnation points associated with the first upper and the first lower vortices. Depending on the parameters Re and α, the rotation may favour the shedding of the first upper vortex, or the first lower vortex (typically at high Reynolds numbers). In a transition region, strong competition for shedding exists between the first two vortices in the form of double transposition of stagnation (closure) points associated with the two vortices. Time variations of lift coefficients characterize different shedding patterns; the cylinder may first experience a substantial maximal downward lift when the first shedding vortex is from the upper wake, or a maximal upward lift otherwise.

NUMERICAL STUDY OF SOUND RADIATION BY AXISYMMETRIC VORTEX RINGS

2003 ◽  
Vol 11 (01) ◽  
pp. 11-45 ◽  
Author(s):  
ELIE RIVOALEN ◽  
SERGE HUBERSON ◽  
OMAR M. KNIO
Keyword(s):  
Sound Production ◽  
Numerical Study ◽  
Sound Radiation ◽  
Particle Method ◽  
Turnover Time ◽  
Vortex Rings ◽  
Vortex Particle Method ◽  
Axisymmetric Vortex ◽  
Dominant Period ◽  
Radiated Sound

The sound production by vortex rings is investigated by means of an axisymmetric vortex particle method. The predictions are first calibrated by analyzing the noise generated by steady vortex rings that are described by the analytical solutions of Fraenkel and Norbury. The noise produced by isolated vortex rings for both nominally steady and unsteady cores is then analyzed. For nominally steady cores, computed results indicate that the efficiency of sound radiation decreases as the slenderness parameter is reduced, and the acoustic signals reveal a dominant period that is approximately half the eddy turnover time. For unsteady cores, the amplitude of the radiated sound is substantially higher than that of similar steady rings. When the initial core vorticity distribution is nonuniform, complex internal motion may also occur within the core which is also reflected in the corresponding far-field acoustic signal. Finally, the effect of vortex stretching is analyzed based on computations of two coaxial corotating vortex rings.

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