Lift, Drag, and Cavitation Onset On Rudders With Leading-edge Tubercles

2010 ◽  
Vol 47 (01) ◽  
pp. 27-36
Author(s):  
Paul W. Weber ◽  
Laurens E. Howle ◽  
Mark M. Murray
Keyword(s):  
Leading Edge ◽  
Reynolds Numbers ◽  
Hydrodynamic Performance ◽  
Humpback Whales ◽  
Control Surface ◽  
The Difference ◽  
Lift And Drag ◽  
Control Surfaces ◽  
Onset Of Cavitation

This paper presents the experimental measurement of lift and drag as well as the determination of the onset of cavitation on rudders with leading-edge protuberances (tubercles) that are operating at low to moderate Reynolds Numbers in water. The leading-edge shape used for the rudders in this study is derived from our earlier work concerning the analysis of the leading-edge morphology found on the pectoral flippers of humpback whales. While humpback whales do not swim at speeds that induce cavitation, engineered control surfaces based on this bio-inspired control surface modification might operate in cavitation conditions. This point motivates our present work to investigate the onset of cavitation on small aspect ratio rudders with tubercles. Our findings are that (i) the presence of leading-edge tubercles accelerates the onset of cavitation, (ii) the tubercles can modify the location of the onset of cavitation, (iii) the tubercle geometry has an influence on the rudder's hydrodynamic performance, (iv) for the lower Reynolds Numbers considered in this paper, the tubercles decrease lift and increase drag for angles of attack between 15 and 22 deg, (v) for angles above 22 deg, rudders with tubercles generate more lift than smooth rudders, and (vi) for the higher Reynolds Numbers investigated, the difference in performance between the smooth and tubercled rudders diminishes, suggesting the existence of a critical Reynolds Number for a given tubercle geometry beyond which tubercles have no significant effect on hydrodynamic performance.

A Numerical Study Into the Influence of Leading Edge Tubercles on the Aerodynamic Performance of a Highly Cambered High Lift Airfoil Wing at Different Reynolds Numbers

2020 ◽  
Author(s):  
Amr Abdelrahman ◽  
Amr Emam ◽  
Ihab Adam ◽  
Hamdy Hassan ◽  
Shinichi Ookawara ◽  
...  
Keyword(s):  
Control Method ◽  
Numerical Study ◽  
Leading Edge ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Stall Angle ◽  
Lifting Surfaces ◽  
Lift And Drag

Abstract Through the last two decades, many studies have demonstrated the ability of leading-edge protrusions (tubercles), inspired from the pectoral flippers of the humpback whale, to be an effective passive flow control method for the stall phase of an airfoil in some cases depending on the geometrical features and the flow regime. Nevertheless, there is a little work associated with revealing tubercles performance for the lifting surfaces with a highly cambered cross-section, used in numerous applications. The present work aims to investigate the effect of implementing leading edge tubercles on the performance of an infinite span rectangular wing with the highly cambered S1223 foil at different flow regimes. Two sets; baseline one and a modified with tubercles have been studied at Re = 0.1 × 106, 0.3 × 106 and 1.5 × 106 using computational fluid dynamics with a validated model. The numerical results demonstrated that Tubercles have the ability to entirely alter the flow structure over the airfoil, confining the separation to troughs, hence, softening the stall characteristics. However, the tubercle modification expedites the presence of the stalled flow over the suction side, lowering the stall angle for the three mentioned Reynolds numbers. While, no considerable difference occurs in lift and drag before the stall.

The effect of leading-edge droop on the performance of cavitating hydrofoil in an oscillating environment

2009 ◽  
Vol 223 (10) ◽  
pp. 2331-2339
Author(s):  
K Park ◽  
H Sun ◽  
S Lee
Keyword(s):  
Leading Edge ◽  
Hydrodynamic Performance ◽  
Control Surface ◽  
Navier Stokes ◽  
Two Phase ◽  
Sheet Cavitation ◽  
Maximum Angle ◽  
Oscillating Motion ◽  
Drag Ratio ◽  
Cavitating Hydrofoil

The hydrodynamics of cavitating hydrofoil in oscillating motion are important in the aspect of the performance and hydro-elasticity of the control surface of the ship. The effect of leading-edge droop is numerically studied in the oscillating hydrofoil with cavitation. A two-phase incompressible Navier—Stokes solver is used to compute the cavitation flow. The hydrodynamic performance of the baseline hydrofoil is compared with that of the fixed droop and the variable droop hydrofoil. The droop models delay the separation behind the sheet cavitation near the maximum angle of attack. When the pitch goes down, the drooped models suppress the collapse of the sheet cavitation. Therefore, they result in the improved hydrodynamic performance against the baseline model through the oscillation cycle. Among the three hydrofoils, the variable droop showed the smallest change of the lift-to-drag ratio.

Transient Response Study on Rolling Effectiveness of Multiple Control Surfaces

2002 ◽  
Author(s):  
Deman Tang ◽  
Aiqin Li ◽  
Earl H. Dowell
Keyword(s):  
Transient Response ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Leading Edge ◽  
Control Surface ◽  
Multiple Control ◽  
Wing Model ◽  
Aerodynamic Model ◽  
Control Surfaces ◽  
Dry Friction Damping

In the present paper, a transient response study of the effectiveness of trailing and leading edge control surfaces has been made for a rolling wing-fuselage model. An experimental model and wind tunnel test are used to assess the theoretical results. The theoretical model includes the inherently nonlinear dry friction damping moment that is present between the spindle support and the experimental aeroelastic wing model. The roll trim equation of motion and the appropriate aeroelastic equations are solved for different combinations of leading and trailing edge control surface rotations using a reduced order aerodynamic model based upon the fluid eigenmodes of three dimensional vortex lattice aerodynamic theory. The present paper provides new insights into the transient dynamic behavior and design of an adaptive aeroelastic wing using trailing and leading edge control surfaces.

scholarly journals Airfoil Selection Procedure, Wind Tunnel Experimentation and Implementation of 6DOF Modeling on a Flying Wing Micro Aerial Vehicle

Micromachines ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 553 ◽  
Author(s):  
Taimur Ali Shams ◽  
Syed Irtiza Ali Shah ◽  
Ali Javed ◽  
Syed Hossein Raza Hamdani
Keyword(s):  
Wind Tunnel ◽  
Equations Of Motion ◽  
Selection Procedure ◽  
Leading Edge ◽  
Control Surface ◽  
Flight Tests ◽  
Micro Aerial Vehicle ◽  
Aerial Vehicle ◽  
P Factor ◽  
Control Surfaces

Airfoil selection procedure, wind tunnel testing and an implementation of 6-DOF model on flying wing micro aerial vehicle (FWMAV) has been proposed in this research. The selection procedure of airfoil has been developed by considering parameters related to aerodynamic efficiency and flight stability. Airfoil aerodynamic parameters have been calculated using a potential flow solver for ten candidate airfoils. Eppler-387 proved to be the most efficient reflexed airfoil and therefore was selected for fabrication and further flight testing of vehicle. Elevon control surfaces have been designed and evaluated for longitudinal and lateral control. The vehicle was fabricated using hot wire machine with EPP styrofoam of density 50 Kg/ m 3 . Static aerodynamic coefficients were evaluated using wind tunnel tests conducted at cruise velocity of 20 m/s for varying angles of attack. Rate derivatives and elevon control derivatives have also been calculated. Equations of motion for FWMAV have been written in a body axis system yielding a 6-DOF model. It was found during flight tests that vehicle conducted coordinated turns with no appreciable adverse yaw. Since FWMAV was not designed with a vertical stabilizer and rudder control surface, directional stability was therefore augmented through winglets and high wing leading edge sweep. Major problems encountered during flight tests were related to left rolling tendency. The left roll tendency was found inherent to clockwise rotating propeller as ‘P’ factor, gyroscopic precession, torque effect and spiraling slipstream. To achieve successful flights, many actions were required including removal of excessive play from elevon control rods, active actuation of control surfaces, enhanced launch speed during take off, and increased throttle control during initial phase of flight. FWMAV flew many successful stable flights in which intended mission profile was accomplished, thereby validating the proposed airfoil selection procedure, modeling technique and proposed design.

scholarly journals Numerical analysis of a leading edge tubercle hydrofoil in turbulent regime

2019 ◽  
Vol 878 ◽  
pp. 292-305 ◽  
Author(s):  
Blanca Pena ◽  
Ema Muk-Pavic ◽  
Giles Thomas ◽  
Patrick Fitzsimmons
Keyword(s):  
Numerical Analysis ◽  
Turbulent Flow ◽  
Flow Regime ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Main Flow ◽  
Hydrodynamic Performance ◽  
Turbulent Regime ◽  
Transitional Regime ◽  
Turbulent Flow Regime

This paper presents a numerical performance evaluation of the leading edge tubercles hydrofoil with particular focus on a fully turbulent flow regime. Efforts were focused on the setting up of an appropriate numerical approach required for an in-depth analysis of this phenomenon, being able to predict the main flow features and the hydrodynamic performance of the foil when operating at high Reynolds numbers. The numerical analysis was conducted using an improved delayed detached eddy simulation for Reynolds numbers corresponding to the transitional and fully turbulent flow regimes at different angles of attack for the pre-stall and post-stall regimes. The results show that tubercles operating in turbulent flow improve the hydrodynamic performance of the foil when compared to a transitional flow regime. Flow separation was identified behind the tubercle troughs, but was significantly reduced when operating in a turbulent regime and for which we have identified the main flow mechanisms. This finding confirms that the tubercle effect identified in a transitional regime is not lost in a turbulent flow. Furthermore, when the hydrofoil operates in the turbulent flow regime, the transition to a turbulent regime takes place further upstream. This phenomenon suppresses a formation of a laminar separation bubble and therefore the hydrofoil exhibits a superior hydrodynamic performance when compared to the same foil in the transitional regime.

Return bit for ploughing tools

2020 ◽  
pp. 12-15
Author(s):  
I. Liskin ◽  
D. Mironov ◽  
S. Sidorov ◽  
I. Afonina
Keyword(s):  
Initial Period ◽  
Leading Edge ◽  
Cutting Edge ◽  
Rear Side ◽  
Front Edge ◽  
Optimal Value ◽  
Central Regions ◽  
The Difference ◽  
Made In

Plough working elements performing formation cutting are the most loaded important parts, on which quality and economic indicators of ploughing depend. In terms of wear capacity, the difference for certain types of soils in Russia can range from 5 to 15 times. Developed and carried out tests of lemechs with a new, unparalleled in the world practice overhead return bit. Determination of the optimal ratio of the thickness of the cutting edge on the blade part of the front and rear side when installing the blade bit. Bits were made in which the leading edge (initial at operation) had a constant value of 4±2 mm. The rear edge had an optimal value of 6 mm from the experiments. The results of the tests showed that on the most common loam soils in the central regions of Russia, the optimal thickness value is the rear cutting edge, which turns the front edge 1.5–1.7 times. It was found that the cutting edge of the blade on the rear side when ploughing loam soils should exceed the leading edge 1.5–1.7 times in the initial period of operation and be 6–7 mm.

Vortex Generators Contribution to the Enhancement of the Aerodynamic Performances

2014 ◽  
Vol 950 ◽  
pp. 268-274
Author(s):  
Hocine Tebbiche ◽  
Mohamed S. Boutoudj
Keyword(s):  
Wind Tunnel ◽  
Flow Control ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Vortex Generators ◽  
Drag Coefficients ◽  
Passive Devices ◽  
Aerodynamic Performances ◽  
Lift And Drag ◽  
Naca 0015

This study interest flow control using a new vortex generators (VGs) shape with counter-rotating vortices, obtained by adding a new element to a configuration mostly investigated. The experiments were performed in the aim to determine the VGs answer when placed on the suction face at 10% from the leading edge of an airfoil Naca 0015 in order to improve the lift and drag coefficients. The investigations were accomplished in wind tunnel for two Reynolds numbers and geometrical vortex generators configurations. The obtained results are analyzed according to several parameters such as the VG height, the space between the same VG pair and the additional factor. The results show a profit brought by the passive devices estimated at about 28% of the CL/Cd ratio.

Bat wing airfoil and planform structures relating to aerodynamic cleanliness

2007 ◽  
Vol 55 (4) ◽  
pp. 237 ◽  
Author(s):  
R. D. Bullen ◽  
N. L. McKenzie
Keyword(s):  
Aspect Ratio ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Foraging Strategy ◽  
High Lift ◽  
Minimum Drag ◽  
Wing Chord ◽  
Lift And Drag ◽  
Lift And Drag Coefficient ◽  
Bat Wing

In this paper we examine 12 species of Western Australian bat for anatomical and morphometric attributes related to wing lift and drag characteristics. We present values for bat wing camber (typically 6.5–9%) and its location, measurements of wing planform and tip shape (typically elliptical but with two different tip designs), dimensions of wing leading-edge flaps (typically 8–10.5% of hand wing chord but with some species having much larger flaps up to 18%) and then discuss several features related to airflow separation control. All species assessed had thin, low-camber airfoil sections, an optimisation appropriate to the range of Reynolds Numbers in which bats fly. Wing relative cleanliness was consistent with, and functionally appropriate to, species foraging strategy. The interceptors had the point of maximum camber well forward and no trailing edge wing fences, optimisations for minimum drag generation. The air-superiority bats had leading-edge fences optimised for maximum lift generation while maintaining low drag. Surface bats were characterised by their low-aspect-ratio wingtips and the absence of optimisations for either low section drag or high lift. The frugivore and the carnivore appear to be discrete optimisations while the emballinurid had a long and broad leading edge flap in combination with a high-aspect-ratio tip. We propose a range of lift and drag coefficient values for use in models of metabolic power output.

Two Dimensional Jet at Low Reynolds Numbers

2007 ◽  
Author(s):  
Akinori Muramatsu ◽  
Tatsuo Motohashi
Keyword(s):  
Reynolds Number ◽  
Outer Part ◽  
Reynolds Numbers ◽  
Streamwise Velocity ◽  
Momentum Conservation ◽  
Control Surface ◽  
Two Dimensional ◽  
Low Reynolds Numbers ◽  
Vortical Motion ◽  
The Difference

A numerical simulation of two-dimensional jets was carried out using a SOLA method. The two-dimensional jets were discharged from a slit in a wall at Reynolds numbers below 50. The difference between the calculated flow fields and those of the Bickley jet is due to the non-uniformity of the pressure field near the jet exit at the wall. The jet spreads faster than the Bickley jet. The decay of the streamwise velocity on the center line is more rapid than that of the Bickley jet. The streamwise velocity profile is different from that of the Bickley jet, and a reversed flow is generated in the outer part of the jet. The jet develops instability through two processes. First, small fluctuations grow exponentially. Second, vortical motion such as so-called ‘flapping motion’ of the jet develops in the downstream region. The critical Reynolds number, as determined by the growth of an integral of kinetic energy, is approximately 16.5. Integrals of momentum and pressure are calculated on a control surface in order to confirm the momentum conservation law. When the Reynolds number exceeds 20, the generation of fluctuations contributes to streamwise variations in the integrals of momentum and pressure.

Effects of smart flap on aerodynamic performance of sinusoidal leading-edge wings at low Reynolds numbers

2020 ◽  
pp. 095441002094690
Author(s):  
AA Mehraban ◽  
MH Djavareshkian ◽  
Y Sayegh ◽  
B Forouzi Feshalami ◽  
Y Azargoon ◽  
...  
Keyword(s):  
High Performance ◽  
Leading Edge ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Drag Forces ◽  
Wide Range ◽  
Beam Bending ◽  
Low Reynolds ◽  
Lift And Drag ◽  
Drag Ratio

Sinusoidal leading-edge wings have shown a high performance after the stall region. In this study, the role of smart flaps in the aerodynamics of smooth and sinusoidal leading-edge wings at low Reynolds numbers of 29,000, 40,000 and 58,000 is investigated. Four wings with NACA 634-021 profile are firstly designed and then manufactured by a 3 D printer. Beam bending equation is used to determine the smart flap chord deflection. Next, wind tunnel tests are carried out to measure the lift and drag forces of proposed wings for a wide range of angles of attack, from zero to 36 degrees. Results show that using trailing-edge smart flap in sinusoidal leading-edge wing delays the stall point compared to the same wing without flap. However, a combination of smooth leading-edge wing and smart flap advances the stall. Furthermore, it is found that wings with smart flap generally have a higher lift to drag ratio due to their excellent performance in producing lift.

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