Effects of Non-Linear Eddy-Airfoil Interaction on the Acoustic Radiation of a Thin Wing

2012 ◽  
Author(s):  
A. Manela
Keyword(s):  
Acoustic Radiation ◽  
Dynamical Problem ◽  
Nonlinear Dynamical ◽  
Reynolds Number Flow ◽  
Motion Signal ◽  
Non Linear ◽  
Number Flow ◽  
High Reynolds ◽  
Dynamical Description ◽  
Nonlinear Dynamical Problem

We study the combined effect of boundary animation (small-amplitude heaving) and incoming flow unsteadiness (incident vorticity) on the vibroacoustic signature of a thin rigid airfoil in low-Mach high-Reynolds number flow. The nonlinear dynamical problem for the vortex trajectory is studied using potential flow theory. The dynamical description then serves as an effective source term to evaluate the far-field sound using Powell-Howe’s analogy. The results identify the fluid-airfoil system as a dipole-type source, and demonstrate the significance of non-linear eddy-airfoil interaction on the acoustic radiation. At low heaving frequencies (ωa/U < 1, where ω denotes the heaving frequency, 2a the airfoil chord, and U the mean stream speed), the effect of heaving is minor, and the acoustic field can be approximated by neglecting airfoil motion. However, at ωa/U > 1, heaving becomes dominant, radiating sound through an “airfoil motion” dipole (oriented along the direction of heaving) and airfoil-induced oscillations in the vortex trajectory. In contrast with the periodic “airfoil motion” signal, the non-periodic incident vortex sound has a component along the airfoil chord, which becomes significant when the vortex passes close to the airfoil. The work is suggested as a preliminary tool to examine the acoustic radiation during flapping flight at unsteady flow conditions.

scholarly journals Approximation theorems of a solution of amperometric enzymatic reactions based on Green’s fixed point normal-S iteration

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Khanitin Muangchoo-in ◽  
Kanokwan Sitthithakerngkiet ◽  
Parinya Sa-Ngiamsunthorn ◽  
Poom Kumam
Keyword(s):  
Fixed Point ◽  
Boundary Value Problems ◽  
Iterative Methods ◽  
Dynamical Problem ◽  
Enzymatic Reactions ◽  
Nonlinear Dynamical ◽  
Numerical Examples ◽  
Approximation Theorems ◽  
Kinetics Of ◽  
Nonlinear Dynamical Problem

AbstractIn this paper, the authors present a strategy based on fixed point iterative methods to solve a nonlinear dynamical problem in a form of Green’s function with boundary value problems. First, the authors construct the sequence named Green’s normal-S iteration to show that the sequence converges strongly to a fixed point, this sequence was constructed based on the kinetics of the amperometric enzyme problem. Finally, the authors show numerical examples to analyze the solution of that problem.

Vortex Suppression Efficiency of Discontinuous Helicoidal Fins

2007 ◽  
Author(s):  
Antonio Pinto ◽  
Riccardo Broglia ◽  
Elena Ciappi ◽  
Andrea Di Mascio ◽  
Emilio F. Campana ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Computational Time ◽  
Reynolds Number Flow ◽  
Flow Past A Cylinder ◽  
Helical Strakes ◽  
Unsteady Rans ◽  
Number Flow ◽  
Offshore Industry ◽  
Good Trade ◽  
High Reynolds

Vortex-Induced Vibration (VIV) is one of the most demanding areas in the offshore industry, and detailed investigation of the fluid-structure interaction is becoming fundamental for designing new structures able to reduce VIV phenomenon. To carry on such analysis, and get reliable results in term of global coefficients, the correct modelling of turbulence, boundary layer, and separated flows is required. Nonetheless, the more accurate is the simulation, the more costly is the computation. Unsteady RANS simulations provide a good trade-off between numerical accuracy and computational time. This paper presents the analysis of the flow past a cylinder with several three-dimensional helical fins at high Reynolds number. Flow field, vortical structures, and response frequency patterns are analysed. Spectral analysis of data is performed to identify carrier frequencies, deemed to be critical due to the induced vibration of the whole structure. Finally, helical strakes efficiency in reducing the riser vibrations is also addressed, through direct consideration on the carrier shedding frequency.

Three-Dimensional Numerical Simulations of Circular Cylinders Undergoing Two Degree-of-Freedom Vortex-Induced Vibrations

2006 ◽  
Author(s):  
Juan P. Pontaza ◽  
Hamn-Ching Chen
Keyword(s):  
Numerical Simulations ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Degree Of Freedom ◽  
Circular Cylinders ◽  
Time Step ◽  
Reynolds Number Flow ◽  
Number Flow ◽  
High Reynolds ◽  
Two Degree Of Freedom

In an effort to gain a better understanding of the VIV phenomena, we present three-dimensional numerical simulations of VIV of circular cylinders. We consider operating conditions that correspond to high Reynolds number flow, low structural damping, and allow for two-degree of freedom motion. The numerical implementation makes use of overset (Chimera) grids, in a multiple block environment where the workload associated with the blocks is distributed among multiple processors working in parallel. The three-dimensional grids around the cylinder are allowed to undergo arbitrary motions with respect to fixed background grids, eliminating the need for tedious grid regeneration at every time step.

scholarly journals The Effect of Surface Roughness of a Body in the High Reynolds-Number Flow

1995 ◽  
Vol 2 (1) ◽  
pp. 23-32
Author(s):  
Tsutomu adachi
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
High Reynolds Number ◽  
The Body ◽  
Reynolds Number Flow ◽  
Flow Phenomena ◽  
Number Flow ◽  
High Reynolds ◽  
Cryogenic Wind Tunnel ◽  
Effect Of Surface

In this paper, first, the principle, structures, operations, and performances of the cryogenic wind tunnel are described. By changing the pressure, temperature and velocity of gas a high Reynolds-number flow(5×104<Re<107)can be obtained. From the research results, a high Reynolds-number flow with comparatively low power, LN consumptions was attained. It was with Mach-number independent of each other, o show some examples of high Reynolds-number flow, the effects of surface roughness and grooves on the surface of a cylinder on the flow are measured using models with various values of roughness and size. A model test of an airship was also conducted. With the high Reynolds-number flow, the thickness of the boundary layer becomes thinner. Then the surface conditions of a body have great effect on the flow phenomena and on the drag of the body. Some attempts to reduce the drag of the body were shown.

Coherent structures in coflowing jets and wakes

1978 ◽  
Vol 88 (3) ◽  
pp. 451-463 ◽  
Author(s):  
A. E. Perry ◽  
T. T. Lim
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Glass Tube ◽  
Reynolds Numbers ◽  
Reynolds Number Flow ◽  
Naturally Occurring ◽  
Number Flow ◽  
High Reynolds ◽  
Scale Motion

By applying small lateral oscillations to a glass tube from which smoke was issuing, perfectly periodic coflowing jets and wake structures were produced at Reynolds numbers of order 300-1000. These structures remained coherent over long streamwise distances and appeared to be perfectly frozen when viewed under stroboscopic light which was synchronized with the disturbing oscillation. By the use of strobing laser beams, longitudinal sections of the structures were photographed and an account of the geometry of these structures is reported.When the tube was unforced, similar structures occurred but they modulated in scale and frequency, and their orientation was random.A classification of structures is presented and examples are demonstrated in naturally occurring situations such as smoke from a cigarette, the wake behind a three-dimensional blunt body, and the high Reynolds number flow in a plume from a chimney. It is suggested that an examination of these structures may give some insight into the large-scale motion in fully turbulent flow.

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