scholarly journals Comparative investigations in the effect of angle of attack profile on hydrodynamic performance of bio-inspired foil, (corrected)

2013 ◽  
Vol 10 (2) ◽  
pp. 99-108 ◽  
Author(s):  
J. A. Esfahani ◽  
E. Barati ◽  
Hamid Reza Karbasian
Keyword(s):  
Angle Of Attack ◽  
Underwater Vehicles ◽  
Hydrodynamic Performance ◽  
Profile Function ◽  
Flapping Foil ◽  
Propulsive Performance ◽  
Wide Range ◽  
Effective Angle ◽  
Thrust Production ◽  
Optimum Profile

In flapping underwater vehicles the propulsive performance of harmonically sinusoidal heaving and pitching foil will be degraded by some awkward changes in effective angle of attack profile, as the Strouhal number increases. This paper surveys different angle of attack profiles (Sinusoidal, Square, Sawtooth and Cosine) and considers their thrust production ability. In the wide range of Strouhal numbers, thrust production of Square profile is considerable but it has a discontinuity in heave velocity profile, in which an infinite acceleration exists. This problem poses a significant defect in control of flapping foil. A novel profile function is proposed to omit sharp changes in heave velocity and acceleration. Furthermore, an optimum profile is found for different Strouhal numbers with respect to Square angle of attack profile.DOI: http://dx.doi.org/10.3329/jname.v10i2.14229

Effective Angle of Attack Control of a Flat Plate Flapping-Foil Turbine

2014 ◽  
Author(s):  
Chigozie Usoh ◽  
John Young ◽  
Joseph Lai ◽  
Muhammad Ashraf
Keyword(s):  
Flat Plate ◽  
Angle Of Attack ◽  
Flapping Foil ◽  
Effective Angle

Effects of circular trailing edge with the dimple on flow separation of NACA S1210 hydrofoil

2020 ◽  
Vol 234 (18) ◽  
pp. 3600-3613
Author(s):  
Parikshit Kundu
Keyword(s):  
Flow Separation ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Power Production ◽  
Hydrodynamic Performance ◽  
Control Methods ◽  
Blade Profile ◽  
Trailing Edge ◽  
Maximum Increase ◽  
Wide Range

Flow separation over a hydrofoil affects its hydrodynamic performance and ultimately reduces the power production of a turbine. Therefore, the different flow control methods have been proposed by the researchers to overcome these challenges. In this study, the combined effects of circular trailing edge with dimple have been investigated numerically on NACA S1210 hydrofoil to control the flow separation of the hydrofoil. The results showed that the coupled effects of the dimple and circular trailing edge modification appeared effective compared to baseline hydrofoil at a wide range of angles of attack. Maximum lift coefficient increments are 9 and 12% at an angle of attack of 10° and 12°, respectively, for circular trailing edge hydrofoil. The maximum increase of glide ratio for the coupled effect (circular trailing edge with outward dimple) is approximately 114% at an angle of attack of 12°. The outcome will be advantageous to design a proper blade profile for horizontal axis current turbines.

Quasi-Steady Effective Angle of Attack and Its Use in Lift-Equivalent Motion Design

AIAA Journal ◽  
2021 ◽  
pp. 1-14
Author(s):  
Xianzhang Xu ◽  
Francis D. Lagor
Keyword(s):  
Angle Of Attack ◽  
Effective Angle ◽  
Motion Design

Modification of effective angle of attack on hydrofoil power extraction

2021 ◽  
Vol 240 ◽  
pp. 109919
Author(s):  
Guanghua He ◽  
Weijie Mo ◽  
Yun Gao ◽  
Zhigang Zhang ◽  
Jiadong Wang ◽  
...  
Keyword(s):  
Angle Of Attack ◽  
Power Extraction ◽  
Effective Angle

Thrust Production in Highly Flexible Pectoral Fins: A Computational Dissection

2011 ◽  
Vol 45 (4) ◽  
pp. 56-64 ◽  
Author(s):  
Srinivas Ramakrishnan ◽  
Meliha Bozkurttas ◽  
Rajat Mittal ◽  
George V. Lauder
Keyword(s):  
Computational Analysis ◽  
Autonomous Underwater Vehicles ◽  
Underwater Vehicles ◽  
Bluegill Sunfish ◽  
Robust Performance ◽  
Pectoral Fin ◽  
Pectoral Fins ◽  
And Performance ◽  
Thrust Production ◽  
Computational Dissection

AbstractBluegill sunfish pectoral fins represent a remarkable success in evolutionary terms as a means of propulsion in challenging environments. Attempts to mimic their design in the context of autonomous underwater vehicles have overwhelmingly relied on the analysis of steady swimming. Experimental observations of maneuvers reveal that the kinematics of fin and wake dynamics exhibit characteristics that are distinctly different from steady swimming. We present a computational analysis that compares, qualitatively and quantitatively, the wake hydrodynamics and performance of the bluegill sunfish pectoral fin for two modes of swimming: steady swimming and a yaw turn maneuver. It is in this context that we comment on the role that flexibility plays in the success of the pectoral fin as a versatile propulsor. Specifically, we assess the performance of the fin by conducting a “virtual dissection” where only a portion of fin is retained. Approximately 90% of peak thrust for steady swimming is recovered using only the dorsal half. This figure drops to 70% for the yaw turn maneuver. Our findings suggest that designs based on fin analysis that account for various locomotion modes can lead to more robust performance than those based solely on steady swimming.

scholarly journals Study on the Motion Stability of the Autonomous Underwater Helicopter

2022 ◽  
Vol 10 (1) ◽  
pp. 60
Author(s):  
Yuan Lin ◽  
Jin Guo ◽  
Haonan Li ◽  
Hai Zhu ◽  
Haocai Huang ◽  
...  
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Angle Of Attack ◽  
Vertical Movement ◽  
Plane Motion ◽  
Hydrodynamic Performance ◽  
Scale Model ◽  
Motion Stability ◽  
Movement Stability ◽  
Stability Indexes ◽  
Drag Ratio

The hydrodynamic performance of a novel hovering autonomous underwater vehicle, the autonomous underwater helicopter (AUH), with an original disk-shaped hull (HG1) and an improved fore–aft asymmetric hull (HG3), is investigated by means of computational fluid dynamics with the adoption of overlapping mesh method. The hydrodynamic performance of the two hull shapes in surge motion with variation of the angle of attack is compared. The results show that HG3 has less resistance and higher motion stability compared to HG1. With the angle of attack reaching 10 degrees, both HG1 and HG3 achieve the maximum lift-to-drag ratio, which is higher for HG3 compared to HG1. Furthermore, based on the numerical simulation of the plane motion mechanism test (PMM) and according to Routh’s stability criterion, the horizontal movement and vertical movement stability indexes of HG1 and HG3 (GHHG1=1.0, GVHG1=49.7, GHHG2=1.0, GVHG3=2.1) are obtained, which further show that the AUH has better vertical movement stability than the torpedo-shaped AUV. Furthermore, the scale model tail velocity experiment indirectly shows that HG3 has better hydrodynamic performance than HG1.

scholarly journals Hydrodynamics of gliding penguin flipper suggests the adjustment of sweepback with swimming speeds

2021 ◽  
Author(s):  
Masateru Maeda ◽  
Natsuki Harada ◽  
Hiroto Tanaka
Keyword(s):  
Large Eddy Simulation ◽  
Cfd Simulation ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Force Balance ◽  
Hydrodynamic Performance ◽  
Vertical Force ◽  
Sweep Angle ◽  
Eddy Simulation ◽  
Large Eddy

Hydrodynamic performance of a gliding penguin flipper (wing) considering the backward sweep was estimated with computational fluid dynamics (CFD) simulation. A flipper of a gentoo penguin (Pygoscelis papua) was 3D scanned, smoothed, and a numerical fluid mesh was generated. For accurate yet resource-saving computation, an embedded large-eddy simulation (ELES) methods was employed, where the flow near the flipper was solved with large-eddy simulation (LES) and flow far away from the flipper was solved with Reynolds-averaged Navier-Stokes (RANS). The relative flow speed was fixed at 2 m s-1, close to the typical foraging speed for the penguin species. The sweep angle was set to be 0°, 30°, and 60°, while the angle of attack was varied between -40° and 40°, both are within the realistic ranges in the wing kinematics measurement of penguins in an aquarium. It was revealed that a higher sweep angle reduces the lift slope, but the lift coefficient is unchanged at a high angle of attack. Drag coefficient was reduced across the angles of attack with increasing the sweep angles. The drag polars suggest the sweep angle may be adjusted with the change in swimming speed and anhedral (negative dihedral) angle to minimise drag while maintaining the vertical force balance to counteract the positive buoyancy. This will effectively expand the swimming envelope of the gliding penguin, similar to a flying counterpart such as swift.

scholarly journals Development trends of outboard launchers for unmanned underwater vehicles and marine underwater weapons from underwater carriers (based on materials from open publications)

2020 ◽  
Author(s):  
В.О. Боярчик ◽  
В.Г. Михлин ◽  
А.А. Румянцев ◽  
Р.А. Урусов
Keyword(s):  
Rapid Development ◽  
Underwater Vehicles ◽  
Technical Condition ◽  
Mineral Deposits ◽  
Development Trends ◽  
Unmanned Underwater Vehicles ◽  
Mining Sites ◽  
Special Place ◽  
Wide Range ◽  
Technical Solutions

Принимая во внимание бурное развитие морской подводной техники для разведки и добычи полезных ископаемых со дна Мирового океана, которое невозможны без широкого использования необитаемых подводных аппаратов (НПА), вопросы, связанные с их отделением от носителя, становятся, несомненно, актуальными. Среди широкой номенклатуры подводных аппаратов, используемых для этих целей, особое место занимают НПА торпедообразной формы. К основной их миссии относят вопросы разведки мест залегания полезных ископаемых, освещения подводной обстановки при проведении работ, а также вопросы контроля технического состояния оборудования, оснащения мест добычи ископаемых, а также охраны района. В статье анализируются тенденции развития забортных пусковых установок, на основе открытых зарубежных и отечественных публикаций (статей, патентов, рекламных буклетов). Рассмотрены известные технические решения забортных пусковых установок и намечены наиболее перспективные направления развития пусковых установок. Taking into account the rapid development of marine underwater equipment for exploration and mining from the bottom of the oceans, which is impossible without the widespread use of unmanned underwater vehicles (UUV), issues related to their separation from the carrier are undoubtedly relevant. Among the wide range of underwater vehicles used for these purposes, a special place is occupied by torpedo-shaped UUV. Their main mission includes issues of exploration of mineral deposits, an overview of the underwater situation during work, as well as issues of monitoring the technical condition of equipment, equipping mining sites, as well as protecting the area. The article analyzes the development trends of overboard launchers based on open foreign and domestic publications (articles, patents, advertising booklets). The well-known technical solutions of overboard launchers are considered and the most promising directions for the development of launchers are outlined.

A Straight-Bladed Variable-Pitch VAWT Concept for Improved Power Generation

2003 ◽  
Author(s):  
Yann Staelens ◽  
F. Saeed ◽  
I. Paraschivoiu
Keyword(s):  
Power Output ◽  
Angle Of Attack ◽  
Correction Function ◽  
Wind Speeds ◽  
Abrupt Changes ◽  
Effective Angle ◽  
Improved Performance ◽  
Stall Angle ◽  
The Cost ◽  
Local Angle

The paper presents three modifications for an improved performance in terms of increased power output of a straight-bladed VAWT by varying its pitch. Modification I examines the performance of a VAWT when the local angle of attack is kept just below the stall value throughout its rotation cycle. Although this modification results in a very significant increase in the power output for higher wind speeds, it requires abrupt changes in the local angle of attack making it physically and mechanically impossible to realize. Modification II improves upon the first by replacing the local angle of attack by the blade static-stall angle only when the former exceeds the latter. This step eliminates the two jumps in the local effective angle of attack curve but at the cost of a slight decrease in the power output. Moreover, it requires a discontinuous angle of attack correction function which may still be practically difficult to implement and also result in an early fatigue. Modification III overcomes the limitation of the second by ensuring a continuous variation in the local angle of attack correction during the rotation cycle through the use of a sinusoidal function. Although the power output obtained by using this modification is less than the two preceding ones, it has the inherent advantage of being practically feasible.

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