scholarly journals Near-wake characteristics of rigid and membrane wings in ground effect

2018 ◽  
Vol 80 ◽  
pp. 199-216 ◽  
Author(s):  
R. Bleischwitz ◽  
R. de Kat ◽  
B. Ganapathisubramani
Keyword(s):  
Ground Effect ◽  
Near Wake ◽  
Wake Characteristics

Numerical investigation of near-wake characteristics of cavitating flow over a circular cylinder

2016 ◽  
Vol 790 ◽  
pp. 453-491 ◽  
Author(s):  
Aswin Gnanaskandan ◽  
Krishnan Mahesh
Keyword(s):  
Circular Cylinder ◽  
Single Phase ◽  
Three Dimensional ◽  
Low Frequency ◽  
Reynolds Numbers ◽  
Cavitating Flow ◽  
Cylinder Surface ◽  
Near Wake ◽  
Eddy Simulation ◽  
Wake Characteristics

A homogeneous mixture model is used to study cavitation over a circular cylinder at two different Reynolds numbers ($Re=200$ and 3900) and four different cavitation numbers (${\it\sigma}=2.0$, 1.0, 0.7 and 0.5). It is observed that the simulated cases fall into two different cavitation regimes: cyclic and transitional. Cavitation is seen to significantly influence the evolution of pressure, boundary layer and loads on the cylinder surface. The cavitated shear layer rolls up into vortices, which are then shed from the cylinder, similar to a single-phase flow. However, the Strouhal number corresponding to vortex shedding decreases as the flow cavitates, and vorticity dilatation is found to play an important role in this reduction. At lower cavitation numbers, the entire vapour cavity detaches from the cylinder, leaving the wake cavitation-free for a small period of time. This low-frequency cavity detachment is found to occur due to a propagating condensation front and is discussed in detail. The effect of initial void fraction is assessed. The speed of sound in the free stream is altered as a result and the associated changes in the wake characteristics are discussed in detail. Finally, a large-eddy simulation of cavitating flow at $Re=3900$ and ${\it\sigma}=1.0$ is studied and a higher mean cavity length is obtained when compared to the cavitating flow at $Re=200$ and ${\it\sigma}=1.0$. The wake characteristics are compared to the single-phase results at the same Reynolds number and it is observed that cavitation suppresses turbulence in the near wake and delays three-dimensional breakdown of the vortices.

The effect of flow perturbations on the near wake characteristics of a circular cylinder

2003 ◽  
Vol 18 (3-4) ◽  
pp. 367-386 ◽  
Author(s):  
E. Konstantinidis ◽  
S. Balabani ◽  
M. Yianneskis
Keyword(s):  
Circular Cylinder ◽  
Near Wake ◽  
Wake Characteristics

Near-wake characteristics of various V-shaped bluff bodies

1994 ◽  
Vol 10 (1) ◽  
pp. 47-53 ◽  
Author(s):  
Jing-Tang Yang ◽  
Go-Long Tsai ◽  
Wen-Bin Wang
Keyword(s):  
Bluff Bodies ◽  
Near Wake ◽  
Wake Characteristics

Effects of tip injection on the performance and near wake characteristics of a model wind turbine rotor

2016 ◽  
Vol 88 ◽  
pp. 73-82 ◽  
Author(s):  
Anas Abdulrahim ◽  
Ezgi Anık ◽  
Yashar Ostovan ◽  
Oğuz Uzol
Keyword(s):  
Wind Turbine ◽  
Turbine Rotor ◽  
Near Wake ◽  
Tip Injection ◽  
Wind Turbine Rotor ◽  
Wake Characteristics

A Comparative Study of the Wind Loads and Wake Characteristics of a Single-Rotor Wind Turbine and Dual-Rotor Wind Turbines

2014 ◽  
Author(s):  
Ahmet Ozbay ◽  
Wei Tian ◽  
Hui Hu
Keyword(s):  
Turbulent Flow ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Large Scale ◽  
Wind Farm ◽  
Wake Flow ◽  
Wind Loads ◽  
Neutral Stability ◽  
Near Wake ◽  
Wake Characteristics

An experimental study was carried out to investigate the aeromechanics and wake characteristics of dual-rotor wind turbines (DRWTs) with co- and counter-rotating configurations, in comparison to those of a conventional singlerotor wind turbine (SRWT), in order to elucidate the underlying physics to explore/optimize design of wind turbines for higher power yield and better durability. The experiments were performed in a large-scale Aerodynamic/Atmospheric Boundary Layer (AABL) wind tunnel under neutral stability conditions. In addition to measuring the power output performance of DRWT and SRWT systems, static and dynamic wind loads acting on those systems were also investigated. Furthermore, a high resolution PIV system was used for detailed near wake flow field measurements (free-run and phase-locked) so as to quantify the near wake turbulent flow structures and observe the transient behavior of the unsteady vortex structures in the wake of DRWT and SRWT systems. In the light of the promising experimental results on DRWTs, this study can be extended further to investigate the turbulent flow in the far wake of DRWTs and utilize multiple DRWTs in different wind farm operations.

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