A critical study on passive flow control techniques for straight-bladed vertical axis wind turbine

Effects of trailing-edge movable flap on aerodynamic performance and noise characteristics of VAWT

Design, experimental investigation, and nonlinear flight dynamics with atmospheric disturbances of a fixed-wing micro air vehicle

Design methodology using characteristic parameters control for low Reynolds number airfoils

Prevailing utilization of airfoils in the design of micro air vehicles and wind turbines causes to gain attention in terms of determination of flow characterization on these flight vehicles operating at low Reynolds numbers. Thus, these vehicles require flow control techniques to reduce flow phenomena such as boundary layer separation or laminar separation bubble (LSB) affecting aerodynamic performance negatively. This chapter presents a detailed review of traditional passive control techniques for flight vehicle applications operating at low Reynolds numbers. In addition to the traditional methods, a new concept of the pre-stall controller by means of roughness material, flexibility and partial flexibility is highlighted with experimental and numerical results. Results indicate that passive flow control methods can dramatically increase the aerodynamic performance of the aforementioned vehicles by controlling the LSB occurring in the pre-stall region. The control of the LSB with new concept pre-stall control techniques provides lift increment and drag reduction by utilizing significantly less matter consumption and low energy. In particular, new types of these methods presented for the first time by the chapter’s authors have enormously influenced the progress of separation and LSB, resulting in postponing of the stall and enhancing the aerodynamic performance of wind turbine applications.

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Traditional and New Types of Passive Flow Control Techniques to Pave the Way for High Maneuverability and Low Structural Weight for UAVs and MAVs

An experimental study has been carried out on a typical Micro Air Vehicle of span 300mm having inverse Zimmerman planform. The objective is to get i) the aerodynamic characteristics of the vehicle in the range of incidence and sideslip angle the vehicle expected to encounter during its flight; ii) an understanding of the propeller effect on the aerodynamic data and iii) the control surface (elevon) effectiveness with incidence. Tests were carried out in a low speed wind tunnel at a freestream velocity of 8 m/s and 12 m/s corresponding to a test Reynolds number based on chord of about 120000 and 180000 respectively. Analysis of the aerodynamic data showed significant effect of propeller flow field on the lift, stall angle and drag of the vehicle. The propeller induced flow is seen to increase the lift coefficient at higher angle of attack and delay the stall. Nonlinear variation is observed in the rolling moment indicating the onset of asymmetric flow field at higher incidence. The effectiveness of the elevon is observed to increase linearly with incidence.

https://www.researchgate.net/profile/Suraj_C_S/publication/258424535_Experimental_Studies_on_a_Propelled_Micro_Air_Vehicle/links/0deec5283010e53072000000.pdf

Experimental Studies on a Propelled Micro Air Vehicle

Self-adaptive flaps on low aspect ratio wings at low Reynolds numbers

Covert feathers, a group of feathers on the upper surface of bird wings, are one of birds’ features that aid them in flight at high angles of attack, making them more maneuverable. In a previous st...

Rudimentary Emulation of Covert Feathers on Low-AR Wings for Poststall Lift Enhancement

An experimental study has been carried out to explore the effect of propeller induced slipstream on the flow field of a fixed wing micro air vehicle (MAV). Tests were conducted at freestream velocity of 10m/s, corresponding to Reynolds number based on root chord of about 160000. Flow pattern on the surface of MAV planform with propeller-on and off
condition was captured using oil flow visualization at four angles of incidence. Mean flow field on the MAV planform at four chordwise planes with propeller-on and off condition
were measured using stereo PIV technique at angle of incidence of 24°. Little difference has been seen on the oil flow pattern at 10° and 15° angle of incidence between propeller-off and on condition. Small asymmetry in the flow topology was observe at 20° angle of incidence. Significant difference in flow field was observed at 24° between propeller-on and off condition. The induced slipstream from the propeller makes the flow well attached over the
wing planform.

D Arivoli

Papers

Experimental Studies on a Propelled Micro Air Vehicle

Self-adaptive flaps on low aspect ratio wings at low Reynolds numbers

Rudimentary Emulation of Covert Feathers on Low-AR Wings for Poststall Lift Enhancement

Experimental studies of propeller induced flow over typical micro air vehicle - AIAA 2013-0060

Effect of Gurney flap on the vortex-dominated flow over low-AR wings