Blunt body near-wake flow field at Mach 10

In this paper, a slotted tip structure is experimentally analyzed. A wind turbine with three blades, of which the radius is 301.74mm, is investigated by the PIV method. Each wind turbine blade is formed with a slots system comprising four internal tube members embedded in the blade. The inlets of the internal tube member are located at the leading edge of the blade and form an inlet array. The outlets are located at the blade tip face and form an outlet array. The near wake flow field of the wind turbine with slotted tip and without slotted tip are both measured. Velocity field of near wake region and clear images of the tip vortex are captured under different wake ages. The experimental results show that the radius of the tip vortex core is enlarged by the slotted tip at any wake age compared with that of original wind turbine. Moreover, the diffusion process of the tip vortex is accelerated by the slotted tip which lead to the disappearance of the tip vortex occurs at smaller wake age. The strength of the tip vortex is also reduced indicating that the flow field in the near wake of wind turbine is improved. The experimental data are further analyzed with the vortex core model to reveal the flow mechanism of this kind of flow control method. The turbulence coefficient of the vortex core model for wind turbine is obtained from the experimental data of the wind turbine with and without slotted tip. It shows that the slotted tip increases the turbulence strength in the tip vortex core by importing airflow into the tip vortex core during its initial generation stage, which leads to the reduction of the tip vortex strength. Therefore, it is promising that the slotted tip can be used to weaken the vorticity and accelerate the diffusion of the tip vortex which would improve the problem caused by the tip vortex.

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Near-Wake Flow Structure of a Suspended Cylindrical Canopy Patch

Water ◽

10.3390/w12010084 ◽

2019 ◽

Vol 12 (1) ◽

pp. 84 ◽

Cited By ~ 1

Author(s):

Ayşe Yüksel Ozan ◽

Didem Yılmazer

Keyword(s):

Flow Field ◽

Flow Structure ◽

Green Infrastructure ◽

Nutrient Management ◽

Wake Flow ◽

Wake Region ◽

Near Wake ◽

Vegetation Patch ◽

Comprehensive Picture ◽

Flowing Waters

Urban stormwater is an important environmental problem, especially for metropolitans worldwide. The most important issue behind this problem is the need to find green infrastructure solutions, which provide water treatment and retention. Floating treatment wetlands, which are porous patches that continue down from the free-surface with a gap between the patch and bed, are innovative instruments for nutrient management in lakes, ponds, and slow-flowing waters. Suspended cylindrical vegetation patches in open channels affect the flow dramatically, which causes a deviation from the logarithmic law. This study considered the velocity measurements along the flow depth, at the axis of the patch, and at the near-wake region of the canopy, for different submerged ratios with different patch porosities. The results of this experimental study provide a comprehensive picture of the effects of different submergence ratios and different porosities on the flow field at the near-wake region of the suspended vegetation patch. The flow field was described with velocity and turbulence distributions along the axis of the patch, both upstream and downstream of the vegetation patch. Mainly, it was found that suspended porous canopy patches with a certain range of densities (SVF20 and SVF36 corresponded to a high density of patches in this study) have considerable impacts on the flow structure, and to a lesser extent, individual patch elements also have a crucial role.

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Separated Flows Around the Rear Window of a Simplified Car Geometry

Journal of Fluids Engineering ◽

10.1115/1.2829566 ◽

2008 ◽

Vol 130 (2) ◽

Cited By ~ 13

Author(s):

Mathieu Rouméas ◽

Patrick Gilliéron ◽

Azeddine Kourta

Keyword(s):

Blunt Body ◽

Wake Flow ◽

Complex Flow ◽

Flow Topology ◽

Rear Window ◽

Near Wake ◽

Longitudinal Vortices ◽

Simulation Based ◽

Aerodynamic Performances ◽

Boltzmann Method

A 3D numerical simulation based on the lattice Boltzmann method is carried out on a simplified car geometry (initially proposed by Ahmed, Ramm, and Falting, 1984, SAE Technical Paper series No. 840300) to analyze and establish a method for controlling the near-wake flow topology of a generic blunt body model. The results indicate the existence of a complex flow topology consisting of transverse and longitudinal vortices emanating from flow separations that occur on the top and the lateral edges of the slanted rear window, respectively. The topology of each structure is detailed and the numerical results are compared with the experimental results in the literature. The results presented in this paper can then be used to develop and parametrize active control solutions conducive to improving the aerodynamic performances of automobile vehicles.

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Numerical simulation of the near-wake flow field of a horizontal-axis wind turbine (HAWT) model

Journal of Vibroengineering ◽

10.21595/jve.2016.16934 ◽

2016 ◽

Vol 18 (5) ◽

pp. 3258-3268

Author(s):

Hong-lei Ding ◽

Dan-mei Hu

Keyword(s):

Numerical Simulation ◽

Flow Field ◽

Wind Turbine ◽

Horizontal Axis ◽

Wake Flow ◽

Horizontal Axis Wind Turbine ◽

Near Wake

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Laminar boundary-layer separation and near-wake flow for a smooth blunt body at supersonic and hypersonic speeds.

AIAA Journal ◽

10.2514/3.4142 ◽

1967 ◽

Vol 5 (6) ◽

pp. 1089-1096 ◽

Cited By ~ 27

Author(s):

JEAN-MARIE GRANGE ◽

JOHN M. KLINEBERG ◽

LESTER LEES

Keyword(s):

Boundary Layer ◽

Laminar Boundary Layer ◽

Blunt Body ◽

Boundary Layer Separation ◽

Wake Flow ◽

Near Wake ◽

Layer Separation ◽

Hypersonic Speeds

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A Novel Fluids Research Technique: Three-State Anemometry

Volume 1: Turbomachinery ◽

10.1115/96-gt-305 ◽

1996 ◽

Author(s):

M. Funes-Gallanzi

Keyword(s):

Flow Field ◽

Region Of Interest ◽

Velocity Fields ◽

Wake Flow ◽

Flow Density ◽

Viscosity Data ◽

Near Wake ◽

Flow Past A Cylinder ◽

Different Populations ◽

Selection Of

A new flow measurement technique is described which allows for the non-intrusive simultaneous measurement of flow velocity, density, and viscosity. The viscosity information can be used to derive the flow field temperature. The combination of the three measured variables and the perfect-gas law then leads to an estimate of the flow field pressure. Thus, the instantaneous state of a flow field can be completely described. Three-State anemometry (3SA), a derivative of PIV, which uses a combination of three monodisperse sizes of styrene seeding particles is proposed. A marker seeding is chosen to follow the flow as closely as possible, while intermediate and large seeding populations provide two supplementary velocity fields, which are also dependent on fluid density and viscosity. A simplified particle motion equation, for turbomachinery applications, is then solved over the whole field to provide both density and viscosity data. The three velocity fields can be separated in a number of ways. The simplest and that proposed in this paper is to dye the different populations and look through interferometric filters at the region of interest. The two critical aspects needed to enable the implementation of such a technique are a suitable selection of the diameters of the particle populations, and the separation of the velocity fields. There has been extensive work on the seeding particle behaviour which allows an estimate of the suitable particle diameters to be made. A technique is described in this paper to allow the separation of μm range particle velocity fields through fluorescence (separation through intensity also being possible). Some preliminary results by computer simulations of a 3SA image are also presented. The particle sizes chosen were 1 μm and 5 μm tested on the near-wake flow past a cylinder to investigate viscosity only, assuming uniform flow density. The accuracy of the technique, derived from simulations of swirling flows, is estimated as 0.5% RMS for velocity, 2% RMS for the density and viscosity, and 4% RMS for the temperature estimate.

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