Dynamic Lift Coefficients for Spade Rudders on Yachts

2007 ◽  
Author(s):  
Paul H. Miller
Keyword(s):  
Lift Coefficient ◽  
Bending Moment ◽  
Pressure Profile ◽  
Element Analysis ◽  
Aspect Ratios ◽  
Back Calculation ◽  
Computational Fluid Dynamics Cfd ◽  
Sailing Yacht ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The loss of a rudder is a dangerous situation for any vessel, and with the increasingly higher aspect ratios in current sailing yacht rudder designs, a better understanding of the forces on a rudder are required. While many failures have been caused by impacts with objects, a large number have failed due to underestimation of sailing loads. While larger aspect ratios increase the lift-to-drag ratio, they also increase the bending moment about the rudder’s root. Combined with thinner airfoil sections to reduce drag, modern rudders are highly stressed. Traditional design methods normally assume that the maximum lift coefficient is constant for all aspect ratios. This project combined computational fluid dynamics (CFD), finite element analysis (FEA) and the tank testing of a 1/5-scale yacht to determine suitable design lift coefficients for spade rudders of cruising and racing yachts. Two rudders of different aspect ratios were tested at various speeds, heel angles and wave conditions in the tank at the Naval Surface Warfare Center – Carderock Division. The rudders were equipped with strain gauges to determine the strains at various positions along the stock and blade. The strain profile was compared against FEA results that used a CFD prediction of the pressure profile. Through back-calculation the lift coefficients in still water and waves were derived. The results indicated that these lift coefficients are not constant.

Effects of Aspect Ratio on the Hydrodynamic Performance of Circular Cambered Otter Board

2018 ◽  
Author(s):  
Liuyi Huang ◽  
Yuyan Li ◽  
Jiqiang Xu ◽  
Qingchang Xu ◽  
Fenfang Zhao ◽  
...  
Keyword(s):  
Lift Coefficient ◽  
Flow Distribution ◽  
Full Scale ◽  
Hydrodynamic Performance ◽  
High Lift ◽  
Aspect Ratios ◽  
Simulation Results ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Good Agreement

An otter board is an important device that provides a desired horizontal opening of a trawl net. A high lift coefficient or lift-to-drag ratio is required for an otter board to maintain fishing efficiency. In the present work, the hydrodynamic performance of a circular cambered otter board was studied by numerical simulation, including the effects of aspect ratios (AR), and flow distribution around the otter board. Model tests were conducted in the flume tank as well as a comparison to the numerical results. It showed that simulation results exhibited very good agreement with experiment results. Results demonstrated that the model otter board had a critical angle of attack (AOA) of 50° (when the stall appeared). The maximum lift coefficient and lift-to-drag ratio of the model otter board were 2.421 and 3.719, respectively. However, the maximum values of the full-scale otter board increased first and then decreased with an increasing AR. And the full-scale otter board had a better performance when AR = 2.489, it can enhance the lift coefficient by 17.4% compared with the initial otter board (AR = 1.25). In addition, the flow distribution around the otter board showed that the flow was smooth at small AOAs, when it attacked at large AOA (exceeded 55°), flow separation and eddies were appeared at the lee-side of the otter board.

scholarly journals Aerodynamic and Vibration Characteristics of the Micro-Octocopter at Low Reynolds Number

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Xiaohua Zou ◽  
Mingsheng Ling ◽  
Wenzheng Zhai
Keyword(s):  
Reynolds Number ◽  
Load Capacity ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Aerodynamic Characteristics ◽  
Vibration Characteristics ◽  
Low Reynolds ◽  
Vibration Performance ◽  
Drag Ratio ◽  
Lift To Drag Ratio

With the development of flight technology, the need for stable aerodynamic and vibration performance of the aircraft in the civil and military fields has gradually increased. In this case, the requirements for aerodynamic and vibration characteristics of the aircraft have also been strengthened. The existing four-rotor aircraft carries limited airborne equipment and payload, while the current eight-rotor aircraft adopts a plane layout. The size of the propeller is generally fixed, including the load capacity. The upper and lower tower layout analyzed in this paper can effectively solve the problems of insufficient four-axis load and unstable aerodynamic and vibration performance of the existing eight-axis aircraft. This paper takes the miniature octorotor as the research object and studies the aerodynamic characteristics of the miniature octorotor at different low Reynolds numbers, different air pressures and thicknesses, and the lift coefficient and lift-to-drag ratio, as well as the vibration under different elastic moduli and air pressure characteristics. The research algorithm adopted in this paper is the numerical method of fluid-solid cohesion and the control equation of flow field analysis. The research results show that, with the increase in the Reynolds number within a certain range, the aerodynamic characteristics of the miniature octorotor gradually become better. When the elastic modulus is 2.5 E, the aircraft’s specific performance is that the lift increases, the critical angle of attack increases, the drag decreases, the lift-to-drag ratio increases significantly, and the angle of attack decreases. However, the transition position of the flow around the airfoil surface is getting closer to the leading edge, and its state is more likely to transition from laminar flow to turbulent flow. When the unidirectional carbon fiber-reinforced thickness is 0.2 mm and the thin arc-shaped airfoil with the convex structure has a uniform thickness of 2.5% and a uniform curvature of 4.5%, the aerodynamic and vibration characteristics of the octorotor aircraft are most beneficial to flight.

Optimal Design of Wind Turbines Using BIAS, A Method of Multipliers Code

1988 ◽  
Author(s):  
B. D. Vick ◽  
W. Wrigglesworth ◽  
L. B. Scott ◽  
K. M. Ragsdell
Keyword(s):  
Optimal Design ◽  
Rough Surface ◽  
Wind Turbines ◽  
Lift Coefficient ◽  
Power Coefficient ◽  
Method Of Multipliers ◽  
High Lift ◽  
Small Wind Turbines ◽  
Drag Ratio ◽  
Lift To Drag Ratio

Abstract A method has been developed and is demonstrated which determines the chord and twist distribution for a wind turbine with maximum power coefficient. Only small wind turbines (less than 10 kilowatts) are considered in this study, but the method could be used for larger wind turbines. Glauert determined a method for estimating the chord and twist distribution that will maximize the power coefficient if there is no drag. However, the method proposed here determines the chord and twist distribution which will maximize the power coefficient with the effect of drag included. Including drag in the analysis does not significantly affect the Glauert chord and twist distribution for airfoils with a high lift coefficient at the maximum lift to drag ratio. However, if the airfoil has a fairly low lift coefficient at its maximum lift to drag ratio due to its shape or a rough surface then significant improvement can be obtained in power coefficient by altering the Glauert chord and twist distribution according to the method proposed herein.

scholarly journals Study of board bending degree on hydrodynamic performances of a single-layer cambered otter-board

2019 ◽  
Vol 131 ◽  
pp. 01120
Author(s):  
Lei Wang ◽  
Lu Min Wang ◽  
Yong Li Liu ◽  
Wen Wen Yu ◽  
Guang Rui Qi ◽  
...  
Keyword(s):  
Center Of Pressure ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Single Layer ◽  
Moment Coefficient ◽  
Pitch Moment ◽  
Engineering Models ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The effect of board bending degree on hydrodynamic performances of a single-layer cambered otter-board was investigated using engineering models in a wind tunnel. Three different bending degree boards were evaluated at a wind speed of 28 m/s. Parameters measured included: drag coefficient Cx, lift coefficient Cy, pitch moment coefficient Cm, center of pressure coefficient Cp , over a range of angle of attack (0° to 70°). These coefficients were used in analyzing the differences in the performance among the three otter-board models. Results showed that the bending of the board(No. 2, No. 3) increased the water resistance of the otter-board, and improved the lift coefficient of the otter-board in the small angle of attack (0°<α≤20 °) ; the maximum lift coefficients Cy of otter-board model (No. 1) was higher (1.680, α = 25°). the maximum lift–drag ratios of models (No. 1, No. 2 and No. 3) are 6.822 (α = 7.5 °), 6.533 (α = 2.5 °) and 6.384 (α = 5.0°), which showed that the board bending reduces the lift-to-drag ratio of the otter-board.The stability of the No. 3 model was better than those two models (No. 1, No. 2) in most range of attack angle, but No. 1 otter-board model had a better stability in roll of otter-board. The findings of this study can offer useful reference data for the structural optimization of otter-boards for trawling.

Effects of leading-edge bevel angle on the aerodynamic forces of a non-slender 50° delta wing

2005 ◽  
Vol 109 (1098) ◽  
pp. 403-407 ◽  
Author(s):  
J. J. Wang ◽  
S. F. Lu
Keyword(s):  
Delta Wing ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Relative Thickness ◽  
Aerodynamic Performances ◽  
Stall Angle ◽  
Drag Ratio ◽  
Low Speed Wind Tunnel ◽  
Lift To Drag Ratio ◽  
Blunt Leading Edge

Abstract The aerodynamic performances of a non-slender 50° delta wing with various leading-edge bevels were measured in a low speed wind tunnel. It is found that the delta wing with leading-edge bevelled leeward can improve the maximum lift coefficient and maximum lift to drag ratio, and the stall angle of the wing is also delayed. In comparison with the blunt leading-edge wing, the increment of maximum lift to drag ratio is 200%, 98% and 100% for the wings with relative thickness t/c = 2%, t/c = 6.7% and t/c = 10%, respectively.

Aerodynamic characteristics of breathing blunt nose configuration at hypersonic speeds

2016 ◽  
Vol 231 (5) ◽  
pp. 840-858 ◽  
Author(s):  
Yasumasa Watanabe ◽  
Kojiro Suzuki ◽  
Ethirajan Rathakrishnan
Keyword(s):  
Lift Coefficient ◽  
Aerodynamic Characteristics ◽  
The Body ◽  
Positive Pressure ◽  
Stagnation Region ◽  
Total Drag ◽  
Hypersonic Speeds ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Blunt Nose

Breathing blunt nose technique is one of the promising methods for reducing the drag of blunt-nosed body at hypersonic speeds. The air, traversed by the bow shock positioned ahead of the nose, at the stagnation region is allowed to enter through a hole at the blunt-nose and ejected at the rear part (base region) of the body. This manipulation reduces the positive pressure over the stagnation regions of the nose and increases the pressure at the base, resulting in reduced suction at the base. The simultaneous manifestation of reducing the compression at the nose and suction at the base regions results in reduction of the total drag. The drag reduction caused by the breathing blunt nose technique has been measured in a Mach 7 tunnel. Also, the drag and flow field around the blunt-nosed body, with and without breathing hole, has been computed. The aerodynamic characteristics of the breathing blunt nose model obtained experimentally are compared with the CFD results. It is found that the breathing results in 5% reduction in drag. The lift coefficient also comes down for the model with breathing nose. But the lift-to-drag ratio is found to be the same for both the cases; the blunt-nosed body with and without nose-hole.

Lift Augmentation between Passive and Active Vortex Generator

2016 ◽  
Vol 851 ◽  
pp. 532-537
Author(s):  
Nur Faraihan Zulkefli ◽  
Zulhilmy Sahwee ◽  
Nurhayati Mohd Nur ◽  
Muhamad Nor Ashraf Mohd Fazil ◽  
Muaz Mohd Shukri
Keyword(s):  
Reynolds Number ◽  
Lift Coefficient ◽  
Vortex Generator ◽  
Leading Edge ◽  
Plasma Actuator ◽  
Triangular Shape ◽  
Subsonic Wind Tunnel ◽  
Different Types ◽  
Drag Ratio ◽  
Lift To Drag Ratio

This study was conducted to investigate the performance of passive and active vortex generator on the wing’s flap. The triangular shape of passive vortex generator (VG) was developed and attached on the wing’s flap leading edge while the plasma actuator performed as active vortex generator. The test was carried out experimentally using subsonic wind tunnel with 300 angles extended flap. Three different types of turbulent flow; with Reynolds number 1.5 x105, 2.0 x105, and 2.6x105 were used to study the aerodynamics forces of airfoil with plasma actuator OFF. All Reynolds number used were below 1x106. The result indicated that airfoil with plasma actuator produced higher lift coefficient 12% and lift-to-drag ratio 5% compared to airfoil with passive vortex generator. The overall result showed that airfoil with plasma actuator produced better lift forces compared to passive vortex generator.

Based on Imitation Seagull Airfoil UVA Wing Numerical Simulation

2012 ◽  
Vol 271-272 ◽  
pp. 791-796
Author(s):  
Xin Hua ◽  
Wei Shao ◽  
Chun Hua Zhang ◽  
Zhi Qiang Zhang
Keyword(s):  
Numerical Simulation ◽  
High Performance ◽  
Lift Coefficient ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Wing Scale ◽  
Fluent Software ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Straight Wing

Wing aircraft is one of the major components to generate lift, in today's energy shortage, design the high lift-to-drag ratio wing is the goal pursued by, The author in the exploration of bionic airfoil aerodynamic characteristics on the basis of, which will be applied to straight wing design so as to improve the aerodynamic performance of aircraft.Our research mainly includes two aspects: first, the use of imitation seagull airfoil and NACA4412 airfoil are designed into the straight wing. The use of FLUENT software in Re=300000condition carries on the numerical simulation results show that the ratio of gull wing airfoil than NACA4412 lift coefficient increased by 13%, while the lift to drag ratio,is improved by 46.83%. Then, using the similarity principle, the wing scale, was tested in a wind tunnel test, the results obtained with the simulation are consistent. Airfoil design for the design of high performance wing opened a new way.

Numerical Study of Winglet Cant Angle Effect on Wing Performance at Low Reynolds Number

2013 ◽  
Vol 393 ◽  
pp. 366-371
Author(s):  
C.F. Mat Taib ◽  
Abdul Aziz Jaafar ◽  
Salmiah Kasolang
Keyword(s):  
Reynolds Number ◽  
Numerical Analysis ◽  
Numerical Study ◽  
Low Reynolds Number ◽  
Lift Coefficient ◽  
Wing Model ◽  
Low Reynolds ◽  
Wing Performance ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The study on the effect of winglet shape in wing design has been a focus of many researchers. Nevertheless, the effect of cant angle on the wing performances at low Reynolds number has not been fully explored. This paper describes the effect of a single semi-circular shaped winglet attached with a rectangular wing model to lower the drag without increasing the span of the wing. Aerodynamic characteristics for the rectangular wing (NACA 65-3-218) with and without semi-circular winglets have been studied using STAR CCM+ 4.0. This numerical analysis is based on Finite Volume Approach. Simulations were carried out on the rectangular wing model with and without winglet at aspect ratio of 2.73 and Reynolds number of 0.16 x 10 6 for various angles of attack. From the numerical analysis, wing performance characteristics in terms of lift coefficient CL, drag coefficient CD, and lift-to-drag ratio, CL/CD were obtained. It was found that the addition of a semi-circular winglet has resulted in a larger lift curve slope and higher Lift-to-Drag ratio in comparison with the case of a wing without winglet. Further investigation has revealed that a wing with semi-circular winglet with cant angle of 45 degree has produced the best Lift-to-Drag ratio, CL/CD.

scholarly journals Aerodynamic Performance of Biomimicry Snake-Shaped Airfoil

2019 ◽  
Vol 9 (2) ◽  
pp. 3319-3323
Keyword(s):  
Cross Section ◽  
Lift Coefficient ◽  
Design Parameters ◽  
Drag Forces ◽  
Cross Section Shape ◽  
Section Shape ◽  
Wide Range ◽  
Lift And Drag ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The cross-section shape and proportionality between geometrical dimensions are the most important design parameters of any lifting surfaces. These parameters affect the amount of the aerodynamic forces that will be generated. In this study, the focus is placed on the snake-cross-section airfoil known as the S-airfoil. It is found that there is a lack of available researches on S-airfoil despite its important characteristics. A parametric study on empty model of the S-airfoil with a cross-section shape that is inspired by the Chrysopelea paradise snake is conducted through numerical simulation. Simulation using 2D-ANSYS FLUENT17 software is used to generate the lift and drag forces to determine the performance of airfoil aerodynamic. Based on the results, the S-airfoil can be improved in performance of aerodynamic by reducing the thickness at certain range, whereby changing the thickness-to-chord ratio from 0.037 to 0.011 results in the increment of lift-to-drag ratio from 2.629 to 3.257. On other hand, increasing the height-to-chord ratio of the S-airfoil will increase maximum lift coefficient but drawback is a wide range of angles of attack regarding maximum lift-to-drag ratio. Encouraging results obtained in this study draws attention to the importance of expanding the research on S-airfoil and its usage, especially in wind energy.

Sign in / Sign up

Export Citation Format

Share Document