Passive Flow Control on Civil Aircraft Flaps Using Sub-Boundary Layer Vortex Generators in the AWIATOR Programme

2006 ◽  
Author(s):  
Keith Bohannon
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Vortex Generators ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Civil Aircraft

Passive Flow Control on Crossing Shock-Wave/Boundary-Layer Interactions

2019 ◽  
Author(s):  
Matthew J. Schwartz ◽  
Katherine Stamper ◽  
Ryan B. Bond ◽  
John D. Schmisseur
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Flow Control ◽  
Passive Flow Control ◽  
Wave Boundary Layer ◽  
Passive Flow ◽  
Wave Boundary

Boundary Layer Control for a Vertical Axis Wind Turbine Using a Secondary-Flow Path System

2011 ◽  
Author(s):  
Alexandrina Untaroiu ◽  
Archie Raval ◽  
Houston G. Wood ◽  
Paul E. Allaire
Keyword(s):  
Boundary Layer ◽  
Control System ◽  
Flow Control ◽  
Wind Turbine ◽  
Secondary Flow ◽  
Flow Path ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Path System ◽  
Flow Control System

Vertical axis wind turbines (VAWTs) have typically lower efficiency compared to their horizontal counterparts (HAWTs), but are attractive for places where taller structures are prohibited, as well as for regions where available wind speeds are lower. For HAWTs, the blades are always perpendicular to the incoming wind, providing a continuous thrust throughout the rotation. Contrary to HAWTs, VAWTs have advancing blades and retreating blades, where blades backtrack against the wind, causing lower efficiency. Hence, any modifications that can be made to improve the efficiency of VAWTs can be beneficial to the wind industry. Passive flow control permits the airfoil geometry to be modified by means of grooves or slots without requiring heavy mechanisms or actuators. Hence, this form of boundary layer control seems advantageous for wind turbines, so that minimal amount of maintenance is required, while complexity of the turbine is not significantly increased. Such modification changes the boundary layer over an airfoil reducing flow separation and reversed flow. This study introduces a new form of passive flow control: Secondary-flow control system, which works on the principle of mass removal, eliminating flow separation at different apparent angles of attack in a VAWT. CFD analysis is used to investigate passive flow control for the airfoils NACA8H12 and LS0417 in a three-bladed VAWT configuration. A secondary flow path is initially designed and optimized in a single airfoil configuration, and then used to adjust the wind turbine blade design. The effects of secondary-flow control system in a VAWT design configuration are investigated by comparison with the non-modified airfoil design. The CFD results indicate that secondary-flow path system can be used to modify and control the boundary layer for a wind turbine. It is believed that secondary-flow control system incorporated in VAWT design has potential for improving turbine efficiency. Further research should be conducted to optimize the secondary-flow path system according to the shape of the airfoil in a 3D VAWT configuration, so that blades interference can be captured.

scholarly journals Visualization of boundary layer separation and passive flow control on airfoils and bodies in wind-tunnel and in-flight experiments

2012 ◽  
Vol 25 ◽  
pp. 01078
Author(s):  
Lukas Popelka ◽  
Jana Kuklova ◽  
David Simurda ◽  
Natalie Souckova ◽  
Milan Matejka ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Flow Control ◽  
Boundary Layer Separation ◽  
Passive Flow Control ◽  
Layer Separation ◽  
Passive Flow

Passive Flow Control on Low-Pressure Turbine Airfoils

2003 ◽  
Vol 125 (4) ◽  
pp. 754-764 ◽  
Author(s):  
Ralph J. Volino
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Free Stream ◽  
Low Pressure ◽  
Suction Surface ◽  
Free Stream Turbulence ◽  
Passive Flow Control ◽  
Low Pressure Turbine ◽  
Passive Flow ◽  
Surface Length

Two-dimensional rectangular bars have been used in an experimental study to control boundary layer transition and reattachment under low-pressure turbine conditions. Cases with Reynolds numbers (Re) ranging from 25,000 to 300,000 (based on suction surface length and exit velocity) have been considered at low (0.5%) and high (8.5% inlet) free-stream turbulence levels. Three different bars were considered, with heights ranging from 0.2% to 0.7% of suction surface length. Mean and fluctuating velocity and intermittency profiles are presented and compared to results of baseline cases from a previous study. Bar performance depends on the bar height and the location of the bar trailing edge. Bars located near the suction surface velocity maximum are most effective. Large bars trip the boundary layer to turbulent and prevent separation, but create unnecessarily high losses. Somewhat smaller bars had no immediate detectable effect on the boundary layer, but introduced small disturbances that caused transition and reattachment to move upstream from their locations in the corresponding baseline case. The smaller bars were effective under both high and low free-stream turbulence conditions, indicating that the high free-stream turbulence transition is not simply a bypass transition induced by the free stream. Losses appear to be minimized when a small separation bubble is present, so long as reattachment begins far enough upstream for the boundary layer to recover from the separation. Correlations for determining optimal bar height are presented. The bars appear to provide a simple and effective means of passive flow control. Bars that are large enough to induce reattachment at low Re, however, cause higher losses at the highest Re. Some compromise would, therefore, be needed when choosing a bar height for best overall performance.

Potential of Retrofit Passive Flow Control for Small Horizontal Axis Wind Turbines

2016 ◽  
Author(s):  
D. Holst ◽  
G. Pechlivanoglou ◽  
F. Wegner ◽  
C. N. Nayeri ◽  
C. O. Paschereit
Keyword(s):  
Flow Control ◽  
Wind Turbines ◽  
High Performance ◽  
Horizontal Axis ◽  
Vortex Generators ◽  
Passive Flow Control ◽  
Wind Speeds ◽  
Passive Flow ◽  
Horizontal Axis Wind Turbines ◽  
Low Reynolds

The present paper analyzes the effect of passive flow control (PFC) with respect to the retrofitting on small horizontal axis wind turbines (sHAWT). We conducted extensive wind tunnel studies on an high performance low Reynolds airfoil using different PFC elements, i.e. vortex generators (VGs) and Gurney flaps. QBlade, an open source Blade Element Momentum (BEM) code, is used to study the retrofitting potential of a simulated small wind turbine. The turbine design is presented and discussed. The simulations include the data and polars gained from the experiments and give further insight into the effects of PFC on sHAWT. Therefore several different blades were simulated using several variations of VG positions. This paper discusses their influence on the turbine performance. The authors focus especially on the start-up performance as well as achieving increased power output at lower wind speeds. The vortex generators reduce the risk of laminar separation and enhance the lift in some configurations by more than 40% at low Reynolds numbers.

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