Numerical Investigation of Bionic Rudder With Leading-Edge Protuberances

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Hongtao Gao ◽  
Wencai Zhu
Keyword(s):  
Electron Microscopy ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Hydrodynamic Performance ◽  
Spanwise Direction ◽  
Flow Mechanism ◽  
Suction Surface ◽  
Edge Profile ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The duck's webbed feet are observed by using electron microscopy, and observations indicate that the edges of the webbed feet are the shape of protuberances. Therefore, the rudder with leading-edge protuberances is numerically studied in the present investigation. The rudder has a sinusoidal leading-edge profile along the spanwise direction. The hydrodynamic performance of rudder is analyzed under the influence of leading-edge protuberances. The present investigations are carried out at Re = 3.2 × 105 and 8 × 105. In the case of Re = 3.2 × 105, the curves of lift coefficient illustrate that the protuberant leading-edge scarcely affects the lift coefficient of bionic rudder. However, the drag coefficient of the bionic rudder is markedly lower than that of the unmodified rudder. Therefore, the lift-to-drag ratio of the bionic rudder is obviously higher than the unmodified rudder. In another case of Re = 8 × 105, the advantageous behavior of the bionic rudder with leading-edge protuberances is mainly performed in the post-stall regime. The flow mechanism of the significantly increased efficiency by the protuberant leading-edge is explored. It is obvious that the pairs of counter-rotating vortices are presented over the suction surface of bionic rudder, and therefore, the flow is more likely to adhere to the suction surface of bionic rudder.

Design and Numerical Investigation of Rudder With Leading-Edge Protuberances

2018 ◽  
Author(s):  
Wencai Zhu ◽  
Hongtao Gao
Keyword(s):  
Numerical Investigation ◽  
Turbulence Model ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Leading Edge ◽  
Numerical Results ◽  
Spanwise Direction ◽  
Suction Surface ◽  
Pressure Surface ◽  
Edge Profile

The marine rudder with leading-edge protuberances is numerically investigated by SST k-ω turbulence model in present investigations. The newly designed rudder has a sinusoidal leading-edge profile along the spanwise direction. The numerical results show that the newly designed rudder helps to improve the lift coefficient of the rudder. The efficiency of the rudder is improved by adopting the leading-edge protuberances. The results are analyzed by means of streamlines and pressure coefficient. The leading-edge protuberances can delay or overcome the stall. The effect of leading-edge protuberances on the pressure coefficient of pressure surface is very small. However, the pressure coefficient of the suction surface is changed in the vicinity of leading-edge.

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.

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.

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.

Hydrodynamic Performance of Leading-Edge Tubercle Three-Dimensional Airfoil

2012 ◽  
Vol 152-154 ◽  
pp. 1509-1515 ◽  
Author(s):  
Feng Feng ◽  
Xiang Ru Cheng ◽  
Xiang Yang Qi ◽  
Xin Chang
Keyword(s):  
Numerical Simulation ◽  
Research Method ◽  
Optimization Design ◽  
Lift Coefficient ◽  
Three Dimensional ◽  
Leading Edge ◽  
Hydrodynamic Performance ◽  
Normal Model ◽  
Edge Profile ◽  
Calculation Results

Based on RANS method, this paper studied leading-edge tubercle three-dimensional airfoil, which had effect on hydrodynamic performance of three-dimensional airfoil. Both section configurations of the two three-dimensional airfoil models were NACA0020 airfoil. The research method was numerical simulation. First, the leading-edge profile of the first airfoil model was normal. To get stalling angle of the first model, it analyzed hydrodynamic performance of the first model under different angle of attacks at Re=1.35*105. Then, the second model had a sinusoidal leading-edge profile. The second model chose the same Reynolds number. By comparison the numerical calculation results between the first and the second model, the stalling angle of second model delays 3°than the normal airfoil, and the lift coefficient of the second model increases 11.92% than the normal model. The results have laid the foundation for optimization design of leading-edge tubercle three-dimensional airfoil.

Numerical Investigation on the Aerodynamic Performance of an Airfoil With Leading-Edge Protuberances

2016 ◽  
Author(s):  
Chang Cai ◽  
Zhigang Zuo ◽  
Shuhong Liu
Keyword(s):  
Control Method ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Streamwise Vortex ◽  
Hydrodynamic Performance ◽  
Small Range ◽  
Wide Range ◽  
Edge Profile ◽  
Passive Technique ◽  
Stall Angle

Leading edge protuberance modifications on airfoils or wings have attracted extensive attentions as a new passive technique for separation control. In this paper, the hydrodynamic performance of a NACA 634-021 foil and a modified foil with leading-edge protuberances were numerically investigated using Spalart-Allmaras turbulence model. Compared to the sharp decline of baseline lift coefficient, the stall angle of the modified foils was advanced and the decline of lift coefficient became mild, and the post-stall performance was improved. A special bi-periodic flow pattern may occur and stay extremely steady at a wide range of attack angles, accompanied with a relatively steady lift. The transformation from single-periodicity to bi-periodicity occurred within a small range of range of attack angle. A couple of counter-rotating streamwise vortex was formed on the shoulder of each protuberance, altering the vorticity line to share a similar shape as the leading-edge profile. At larger angles of attack, the development of streamwise vortex would be accompanied with transformation to lateral vortex, where strong interaction may happen and give rise to the occurrence of bi-periodic condition. The formation mechanism and control method of the special phenomenon should be investigated more deeply in the future.

RANS Investigation of the Transitional Flow Over Stepped NLF(1)-0416

2012 ◽  
Author(s):  
Shervin Sammak ◽  
Rambod Mojgani ◽  
Masoud Boroomand
Keyword(s):  
Skin Friction ◽  
Fluid Dynamic ◽  
Leading Edge ◽  
Transitional Flow ◽  
Stream Velocity ◽  
Backward Facing Step ◽  
Suction Surface ◽  
Rans Equations ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The Computational Fluid Dynamic simulation of RANS equations over NLF(1)-0416, utilized by backward facing step, is investigated for enhancement of aerodynamic characteristics. This article concentrates on the effects of step location transition point and reattachment of separated flow by backward facing step on pressure distribution and skin friction coefficient and subsequently on lift and drag. Reynolds number (based on the free stream velocity and airfoil chord) is 2.0 million. The finite volume method has been employed to numerically solve the steady state compressible Reynolds Averaged Navier-Stokes (RANS) equations with second order Roe’s scheme. Steps at different chordwise locations are chosen on both suction and pressure sides of the airfoil in order to determine their effects on skin friction, lift, lift to drag ratio and near stall behavior. In specific cases decreasing in drag is achieved due to step point on the chord followed by transition inception. The results show that all stepped studied airfoil cases experienced higher drag in comparison with base airfoil. Lift to drag ratio enhancement is seen in step on pressure side while the step extended to leading edge, this effect increases. Based on the results, delaying stall in some cases with step on suction surface is concluded.

Performance of S1210 Profile Used in Current Turbine Blades With Tubes Inserted at a Regular Interval

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Parikshit Kundu ◽  
Arunjyoti Sarkar ◽  
Vishwanath Nagarajan
Keyword(s):  
Flow Separation ◽  
Turbine Blades ◽  
Leading Edge ◽  
Suction Side ◽  
Current Speed ◽  
Separation Process ◽  
Hydrodynamic Performance ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Current Turbine

Abstract The annual power output of a current turbine is affected by flow separation followed by the stall condition in an environment of varying current speed. Flow separation appears as the fluid in the boundary layer over the blade surface loses its kinetic energy. Delaying this separation process is essential to extract more power throughout the year considering the variation in the current speed. Several active and passive means are available in the literature today to achieve a delay in the flow separation process. Inserting tubes in an aero/hydrofoil at a constant spacing, connecting the fluid near the leading edge and a downstream location on the suction side is a novel approach that has been numerically investigated here. The baseline profile chosen here is S1210, which is used in the current turbine blades. The hydrodynamic performance of the profile with tubes has been compared with the baseline profile in terms of the force coefficients, lift to drag ratio, and stall angle. The maximum lift has been noticed to be increased by 18% and the stall is delayed by 2 deg (from 10 deg to 12 deg). The maximum lift to drag ratio is increased by 130% at 12 deg (beyond the stall of the baseline profile). The results show that the insertion of tubes can make the existing profile more efficient for the stated application.

scholarly journals An aeroelastic instability provides a possible basis for the transition from gliding to flapping flight

2013 ◽  
Vol 10 (80) ◽  
pp. 20120940 ◽  
Author(s):  
Oscar M. Curet ◽  
Sharon M. Swartz ◽  
Kenneth S. Breuer
Keyword(s):  
Lift Coefficient ◽  
Leading Edge ◽  
Flapping Flight ◽  
Fluid Forces ◽  
Low Wind Speed ◽  
Stiffness Properties ◽  
Edge Vortex ◽  
Lifting Surfaces ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The morphology, kinematics and stiffness properties of lifting surfaces play a key role in the aerodynamic performance of vertebrate flight. These surfaces, as a result of their flexible nature, may move both actively, owing to muscle contraction, and passively, in reaction to fluid forces. However, the nature and implications of this fluid–structure interaction are not well understood. Here, we study passive flight (flight with no active wing actuation) and explore a physical mechanism that leads to the emergence of a natural flapping motion. We model a vertebrate wing with a compliant shoulder and the ability to camber with an idealized physical model consisting of a cantilevered flat plate with a hinged trailing flap. We find that at low wind speed the wing is stationary, but at a critical speed the wing spontaneously flaps. The lift coefficient is significantly enhanced once the wing starts to oscillate, although this increase in lift generation is accompanied by an increase in drag. Flow visualization suggests that a strong leading edge vortex attached to the wing during downstroke is the primary mechanism responsible for the enhanced lift. The flapping instability we observe suggests a possible scenario for an evolutionary transition from gliding to powered flapping flight in animals that possess compliant wings capable of passive camber. Although the flapping state is accompanied by a lower lift-to-drag ratio, the increased lifting capability it confers might have enabled increased body mass, improved foraging performance and/or flight at lower speeds, any of which might have been selectively advantageous.

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.

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