Regular and chaotic advection in the flow field of a three-vortex system

1998 ◽  
Vol 58 (6) ◽  
pp. 7330-7349 ◽  
Author(s):  
Leonid Kuznetsov ◽  
George M. Zaslavsky
Keyword(s):  
Flow Field ◽  
Chaotic Advection ◽  
Vortex System

Chaotic advection of fluid particles

1990 ◽  
Vol 333 (1631) ◽  
pp. 273-288 ◽  
Keyword(s):  
Flow Field ◽  
Fluid Mechanics ◽  
Particle Motion ◽  
Basic Feature ◽  
Point Of View ◽  
Chaotic Advection ◽  
Dynamical Processes ◽  
Fluid Particles

Particle motion in a fluid can be chaotic even when the flow field is very simple from an eulerian point of view. This basic feature of fluid kinematics, known as chaotic advection, is reviewed and a number of applications are cited. The notion of a chaotic ‘kinematic template’ underlying dynamical processes is introduced and discussed. Some emerging directions of investigation for this application of chaos to fluid mechanics are indicated.

Visualizations of the Unsteady Flow Field Near the Endwall of a Turbine Cascade

2002 ◽  
Author(s):  
Hongwei Ma ◽  
Haokang Jiang ◽  
Yaxi Qiu
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Incidence Angle ◽  
Suction Side ◽  
Horseshoe Vortex ◽  
Radial Clearance ◽  
Pressure Side ◽  
Turbine Cascade ◽  
Suction Surface ◽  
Vortex System

The unsteady flow field near the endwall of a turbine cascade was visualized in a water tunnel using the hydrogen bubble technique. With the help of a light sheet, the experiment was carried out at different incidences without a radial clearance. A fluctuating horseshoe vortex system of varying number of vortices is observed near the leading-edge endwall. The pressure-side leg of the vortex moves toward the suction side after it enters the passage, while the suction-side leg develops along the corner of the suction surface. With the incidence increase, the pressure-side leg of the horseshoe vortex becomes stronger and can directly kick on the suction surface, causing a considerable influence nearby. The interaction and the flow mixing among the counter-rotating horseshoe legs, the endwall boundary layer and the main flow occur in the passage, forming a vortex system traditionally called the passage vortex. The vortex patterns and the interactions are related to the incidence angle.

LES of the Flow and Particle Ingestion Into an Air Intake of a Jet Engine Running on the Ground

2004 ◽  
Author(s):  
Dragos Moroianu ◽  
Arne Karsllon ◽  
Laszlo Fuchs
Keyword(s):  
Flow Field ◽  
Vortex System ◽  
Compressor Blades ◽  
Mean Velocity ◽  
Jet Engine ◽  
Large Eddy ◽  
Air Intake ◽  
Ground Effects ◽  
Particle Ingestion ◽  
Good Agreement

The flow field generated by the flow into a jet engine air-intake, with near ground effects, is considered. The axial inflow in the neighborhood of the ground generates a system of unsteady vortices. Some of these vortices extend from the air-intake towards the ground. Some of these vortices are strong enough to dislocate and even lift small objects from the ground up to the air-intake. The dynamics of the vortex system makes it difficult to study the problem by standard numerical and experimental methods. The dynamics of the vortices can be captured by using Large Eddy Simulations (LES), which is used here to enhance the understanding of the dynamics of the flow field. The computed flow field is used also to assess the ingestion of particles into the air-intake. It is shown that particles of several mm sizes can be ingested into the jet engine. This in turn may result in enhanced erosion of the compressor blades. The results of the computations in terms of mean velocity field have been compared to experimental data. These results are in good agreement with the experiments.

scholarly journals Vortex Evolution within Propeller Induced Scour Hole around a Vertical Quay Wall

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1538 ◽  
Author(s):  
Maoxing Wei ◽  
Nian-Sheng Cheng ◽  
Yee-Meng Chiew ◽  
Fengguang Yang
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Critical Role ◽  
Turbulent Energy ◽  
Energy Spectra ◽  
Small Scale ◽  
Central Plane ◽  
Vortex System ◽  
Quay Wall ◽  
Scour Hole

This paper presents an experimental study on the characteristics of the propeller-induced flow field and its associated scour hole around a closed type quay (with a vertical quay wall). An “oblique particle image velocimetry” (OPIV) technique, which allows a concurrent measurement of the velocity field and scour profile, was employed in measuring the streamwise flow field (jet central plane) and the longitudinal centerline scour profile. The asymptotic scour profiles obtained in this study were compared with that induced by an unconfined propeller jet in the absence of any berthing structure, which demonstrates the critical role of the presence of the quay wall as an obstacle in shaping the scour profile under the condition of different wall clearances (i.e., longitudinal distance between propeller and wall). Moreover, by comparing the vortical structure within the asymptotic scour hole around the vertical quay wall with its counterpart in the case of an open quay (with a slope quay wall), the paper examines the effect of quay types on the formation of the vortex system and how it determines the geometrical characteristic of the final scour profile. Furthermore, the temporal development of the mean vorticity field and the vortex system are discussed in terms of their implications on the evolution of the scour hole. In particular, comparison of the circulation development of the observed vortices allows a better understanding of the vortex scouring mechanism. Energy spectra analysis reveals that at the vortex centers, their energy spectra distributions consistently follow the −5/3 law throughout the entire scouring process. As the scour process evolves, the turbulent energy associated with the near-bed vortex, which is responsible for scouring, is gradually reduced, especially for the small-scale eddies, indicating a contribution of the dissipated turbulent energy in excavating the scour hole. Finally, a comparison of the near-bed flow characteristics of the average kinetic energy (AKE), turbulent kinetic energy (TKE), and Reynolds shear stress (RSS) are also discussed in terms of their implications for the scour hole development.

Three-dimensional numerical modeling of flow upstream of a symmetric streamlined body mounted over a flat plate with tip gap

2022 ◽  
pp. 095440622110470
Author(s):  
Ovais U Khan ◽  
Ghulam Arshed ◽  
Mohammad Javed Khan
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Numerical Simulations ◽  
Flat Plate ◽  
Free Stream ◽  
Three Dimensional ◽  
System Structure ◽  
Research Activity ◽  
Vortex System ◽  
Streamlined Body

In this research activity numerical simulations are carried out to investigate the flow field upstream of a symmetric streamlined body mounted perpendicular to a flat plate with and without clearance gap between the tip of the streamlined body and the flat plate with laminar boundary layer. The developed numerical model successfully predicted the three-dimensional horseshoe vortex system upstream of the streamlined body with and without the tip gap. The resulting vortex system for the configuration with tip gap contains multiple vortices with characteristics similar to that of end-wall-flows of surface-mounted obstacles. The effects of varying tip gap clearance for various values of free stream Reynolds number are also investigated. It was found that the introduction of a gap between the streamlined body tip and flat surface caused shifting of the vortex structure system in the upstream direction. Moreover, it is observed that the free stream Reynolds number and the tip gap between the streamlined body and the flat plate substantially influences the unsteady character of the flow field and the vortex system structure. Results obtained from the numerical simulations are compared with experimental measurements of a blunt body configuration and have been found in good agreement.

Experimental study of the plane of symmetry flow structure upstream of blunt bodies with tip clearance

2009 ◽  
Vol 223 (7) ◽  
pp. 1597-1604 ◽  
Author(s):  
Javed M Khan ◽  
E Tay
Keyword(s):  
Flow Field ◽  
Flow Visualization ◽  
Flat Plate ◽  
Cross Section ◽  
Tip Clearance ◽  
Square Cylinder ◽  
Primary Vortex ◽  
Vortex System ◽  
Blunt Bodies ◽  
End Wall

Flow field in the plane of symmetry, upstream of circular and square cross-section blunt bodies mounted perpendicular to a flat plate with varying clearance between the obstacle tip and the flat plate, was experimentally studied in a water tunnel for a Reynolds numbers of 1400—3100. Qualitative aspects of the flow were captured using flow visualization. Detailed mapping of the flow field was carried out using planar particle image velocimetry (PIV). The existence of a multiple vortex system with characteristics similar to that of end-wall flows of surface-mounted obstacles with zero gap was noted. For large gap values, a jet-like flow was observed in the flow visualization; however, PIV measurements revealed the presence of the characteristic juncture vortex system even for such a configuration. The primary vortex of the square cylinder was observed to be further upstream as compared with the circular cylinder and moved closer to the cylinder surface with increasing Reynolds number. The vortex system for the square cylinder oscillated at a higher frequency. Increasing the tip gap resulted in the upstream movement of the primary vortex and reduction in amplitude and frequency of oscillation for both the cross-sections. The end-wall flow for the square cross-section cylinder was found to be more sensitive to variation in the tip gap.

Vortex system around a step cylinder in a turbulent flow field

2021 ◽  
Vol 33 (4) ◽  
pp. 045112
Author(s):  
Cai Tian ◽  
Fengjian Jiang ◽  
Bjørnar Pettersen ◽  
Helge I. Andersson
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Vortex System ◽  
Turbulent Flow Field

Numerical Study of the Combined Free-Forced Convection and Mass Transfer Flow Past a Vertical Porous Plate in a Porous Medium with Heat Generation and Thermal Diffusion

2006 ◽  
Vol 11 (4) ◽  
pp. 331-343 ◽  
Author(s):  
M. S. Alam ◽  
M. M. Rahman ◽  
M. A. Samad
Keyword(s):  
Mass Transfer ◽  
Flow Field ◽  
Differential Equations ◽  
Forced Convection ◽  
Heat Generation ◽  
Numerical Study ◽  
Porous Plate ◽  
Integration Scheme ◽  
Suction Parameter ◽  
Transfer Flow

The problem of combined free-forced convection and mass transfer flow over a vertical porous flat plate, in presence of heat generation and thermaldiffusion, is studied numerically. The non-linear partial differential equations and their boundary conditions, describing the problem under consideration, are transformed into a system of ordinary differential equations by using usual similarity transformations. This system is solved numerically by applying Nachtsheim-Swigert shooting iteration technique together with Runge-Kutta sixth order integration scheme. The effects of suction parameter, heat generation parameter and Soret number are examined on the flow field of a hydrogen-air mixture as a non-chemical reacting fluid pair. The analysis of the obtained results showed that the flow field is significantly influenced by these parameters.

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