Near wake flow field measurements.

AIAA Journal ◽  
1965 ◽  
Vol 3 (11) ◽  
pp. 2075-2080 ◽  
Author(s):  
ANTONIO TODISCO ◽  
ADRIAN J. PALLONE
Keyword(s):  
Flow Field ◽  
Field Measurements ◽  
Wake Flow ◽  
Near Wake

Near wake flow field measurements

1965 ◽  
Author(s):  
A. PALLONE ◽  
A. TODISCO
Keyword(s):  
Flow Field ◽  
Field Measurements ◽  
Wake Flow ◽  
Near Wake

Experimental Investigation on the Tip Vortex of a Wind Turbine With and Without a Slotted Tip

2017 ◽  
Author(s):  
Pengyin Liu ◽  
Jinge Chen ◽  
Shen Xin ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Wind Turbine ◽  
Vortex Core ◽  
Control Method ◽  
Tip Vortex ◽  
Wake Flow ◽  
Core Model ◽  
Near Wake ◽  
Measured Velocity

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.

scholarly journals Near-Wake Flow Structure of a Suspended Cylindrical Canopy Patch

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 84 ◽  
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.

scholarly journals Blunt body near-wake flow field at Mach 6

1996 ◽  
Author(s):  
Thomas Horvath ◽  
Catherine McGinley ◽  
Klaus Hannemann
Keyword(s):  
Flow Field ◽  
Blunt Body ◽  
Wake Flow ◽  
Near Wake

Heat Transfer, Pressure Loss and Flow Field Measurements Downstream of Staggered Two-Row Circular and Elliptical Pin Fin Arrays

2005 ◽  
Vol 127 (5) ◽  
pp. 458-471 ◽  
Author(s):  
Oguz Uzol ◽  
Cengiz Camci
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Pressure Loss ◽  
Total Pressure ◽  
Local Heat Transfer ◽  
Field Measurements ◽  
Local Heat ◽  
Wake Flow ◽  
Pin Fin ◽  
Pin Fin Arrays

This paper presents the results of heat transfer, total pressure loss, and wake flow field measurements downstream of two-row staggered elliptical and circular pin fin arrays. Two different types of elliptical fins are tested, i.e., a Standard Elliptical Fin (SEF) and a fin that is based on NACA four digit symmetrical airfoil shapes (N fin). The results are compared to those of a corresponding circular pin fin array. The minor axis lengths for both types of elliptical fins are kept equal to the diameter of the circular fins. Experiments are performed using Liquid Crystal Thermography and total pressure probe wake surveys in a Reynolds number range of 18 000 and 86 000 as well as Particle Image Velocimetry (PIV) measurements at ReD=18 000. The pin fins had a height-to-diameter ratio of 1.5. The streamwise and the transverse spacings were equal to one circular fin diameter, i.e., S/D=X/D=2. For the circular fin array, average Nusselt numbers on the endwall within the wake are about 27% higher than those of SEF and N fin arrays. Different local heat transfer enhancement patterns are observed for elliptical and circular fins. In terms of total pressure loss, there is a substantial reduction in case of SEF and N fins. The loss levels for the circular fin are 46.5% and 59.5% higher on average than those of the SEF and N fins, respectively. An examination of the Reynolds analogy performance parameter show that the performance indices of the SEF and the N fins are 1.49 and 2.0 times higher on average than that of circular fins, respectively. The thermal performance indices show a collapse of the data, and the differences are much less evident. Nevertheless, N fins still show slightly higher thermal performance values. The wake flow field measurements show that the circular fin array creates a relatively large low momentum wake zone compared to the SEF and N fin arrays. The wake trajectories of the first row of fins in circular, SEF and N fin arrays are also different from each other. The turbulent kinetic energy levels within the wake of the circular fin array are higher than those for the SEF and the N fin arrays. The transverse variations in turbulence levels correlate well with the corresponding local heat transfer enhancement variations.

scholarly journals Blunt body near-wake flow field at Mach 10

1997 ◽  
Author(s):  
Thomas Horvath ◽  
Klaus Hannemann ◽  
Thomas Horvath ◽  
Klaus Hannemann
Keyword(s):  
Flow Field ◽  
Blunt Body ◽  
Wake Flow ◽  
Near Wake ◽  
Mach 10

A Novel Fluids Research Technique: Three-State Anemometry

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.

A Comparative Study of the Dynamic Wind Loads and Wake Flow Characteristics of a Turbine Sited in Onshore and Offshore Wind Farms

2014 ◽  
Author(s):  
Wei Tian ◽  
Ahmet Ozbay ◽  
Hui Hu
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Wind Farms ◽  
Field Measurements ◽  
Wake Flow ◽  
Offshore Wind ◽  
Wind Loads ◽  
Offshore Wind Farms ◽  
Piv Measurements ◽  
Turbine Model

An experimental study was conducted to compare the characteristics of the dynamic wind loads and evolution of the unsteady vortex and turbulent flow structures in the wake of a wind turbine sited in onshore and offshore wind farms. A scaled three-blade Horizontal Axial Wind Turbine (HAWT) model was placed in Atmospheric Boundary Layer (ABL) winds with different mean and turbulence characteristics to simulate the wind conditions in onshore and offshore wind farms. In addition to measuring dynamic wind loads acting on the wind turbine model by using a high-sensitive force-moment sensor unit, a high-resolution digital Particle Image Velocimetry (PIV) system was used to achieve flow field measurements to quantify the characteristics of the turbulent flow in the wake of the wind turbine model. Besides conducting “free-run” PIV measurements to determine the ensemble-averaged statistics of the flow quantities such as mean velocity, Reynolds stress, and Turbulence Kinetic Energy (TKE) distributions in the wake, “phase-locked” PIV measurements were also performed to elucidate further details about evolution of the unsteady vortex structures in the wake flow in relation to the position of the rotating turbine blades. The detailed flow field measurements are correlated with the dynamic wind loads measurements to elucidate underlying physics in order to gain further insight into changes of the dynamic wind loads and wake characteristics behind the wind turbine operating in either onshore or offshore wind farms.

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