scholarly journals Investigation on Hydrodynamic Performance of Flapping Foil Interacting with Oncoming Von Kármán Wake of a D-Section Cylinder

2021 ◽  
Vol 9 (6) ◽  
pp. 658
Author(s):  
Jian Li ◽  
Peng Wang ◽  
Xiaoyi An ◽  
Da Lyu ◽  
Ruixuan He ◽  
...  
Keyword(s):  
Bluff Body ◽  
Underwater Vehicle ◽  
Chord Length ◽  
Hydrodynamic Performance ◽  
Foil Thickness ◽  
Geometrical Parameters ◽  
Flapping Motion ◽  
Flapping Foil ◽  
Propelling Efficiency ◽  
Flapping Foils

Flapping foils are studied to achieve an efficient propeller. The performance of the flapping foil is influenced by many factors such as oncoming vortices, heaving amplitude, and geometrical parameters. In this paper, investigations are performed on flapping foils to assess its performance in the wake of a D-section cylinder located half a diameter in front of the foil. The effects of heaving amplitude and foil thickness are examined. The results indicate that oncoming vortices facilitate the flapping motion. Although the thrust increases with the increasing heaving amplitude, the propelling efficiency decreases with it. Moreover, increasing thickness results in higher efficiency. The highest propelling efficiency is achieved when the heaving amplitude equals ten percent of the chord length with a symmetric foil type of NACA0050 foil. When the heaving amplitude is small, the influence of the thickness tends to be more remarkable. The propelling efficiency exceeds 100% and the heaving amplitude is 10% of the chord length when the commonly used equation is adopted. This result demonstrates that the flapping motion extracts some energy from the oncoming vortices. Based on the numerical results, a new parameter, the energy transforming ratio (RET), is applied to explicate the energy transforming procedure. The RET represents that the flapping foil is driven by the engine or both the engines and the oncoming vortices with the range of RET being (0, Infini) and (−1, 0), respectively. With what has been discussed in this paper, the oncoming wake of the D-section cylinder benefits the flapping motion which indicates that the macro underwater vehicle performs better following a bluff body.

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

Effect of Geometric Parameters of New Semisubmersible Platform on Stability and Hydrodynamic Performance

2021 ◽  
Author(s):  
Tianying Wang ◽  
Yanjun Zhou ◽  
Honglin Tang ◽  
Shihua Zhang ◽  
Haiqing Tian
Keyword(s):  
Geometric Parameters ◽  
Hydrodynamic Performance ◽  
Geometrical Parameters ◽  
Main Body ◽  
Floating Bodies ◽  
Full Picture ◽  
New Type ◽  
Design Plan ◽  
The Stability ◽  
Shape Characteristics

Abstract The JCSM concept (short for Jackup Combined Semisubmersible Multifunction Platform) is a new type of semisubmersible platform presented by the first author, which overcomes the shortcomings of the available semisubmersible platforms, and combines the advantages of the traditional semisubmersible platform, the Jackup platform and the new FPSO concept - IQFP. Due to the complicated interaction between stability and hydrodynamic performance, it is necessary to explore the effect of geometrical parameters of the main body on the stability and hydrodynamic performance in order to obtain the optimal design plan of a JCSM platform. Firstly, the structure components and innovations of the JCSM were briefly reviewed in order to facilitate readers to understand its full picture. Then, six independent geometric parameters were selected by carefully studying the shape characteristics of the initial design plan of a JCSM study case. Furthermore, the stability heights and motion responses of various floating bodies of the JCSM case with different geometric parameters in wave were calculated using boundary element method based on potential flow theory. Lastly, effect of the shape parameters on stability and hydrodynamic performance of the JCSM was qualitatively evaluated. The research would shed lights on the shape design of the JCSM main body.

Numerical Simulation Study on the Recovery Process of Autonomous Underwater Vehicle

2021 ◽  
Author(s):  
Weigang Huang ◽  
Donglei Zhang ◽  
Jiawei Yu ◽  
Tao He ◽  
Xianzhou Wang
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Autonomous Underwater Vehicle ◽  
Flow Characteristics ◽  
Recovery Process ◽  
Underwater Vehicle ◽  
Hydrodynamic Performance ◽  
Time Step ◽  
Convergence Test ◽  
Motion Paths

Abstract AUV (Autonomous Underwater Vehicle) recovery is considerably influenced by the nearby flow field and simulations of AUV in different motion paths in the wake of a submarine with a propeller are presented in this paper. A commercial CFD solver STAR CCM+ has been used to research the motion and flow characteristics of AUV, which using the advanced computational continuum mechanics algorithms. The DARPA (Defense Advanced Research Projects Agency) SUBOFF Submarine (L1 = 4.356m) propelled with INSEAN (Italian Ship Model Basin) E1619 propeller is used in this study, and the self-propulsion characteristics of the propeller at an incoming flow velocity of 2.75m/s are obtained through numerical simulation and results are compared with the available experimental data to prove the accuracy of the chosen investigation methodology. A grid/time-step convergence test is performed for verification study. AUV (L2 = 0.4356m) is a smaller-scale SUBOFF without a sail, which approaches the submarine in different motion paths in the submarine wake at a relative speed combined with the dynamic overlapping grid technology. The hydrodynamic performance of the AUV when approaching the submarine and the velocity distribution of the surrounding flow field are analyzed, which provides a useful reference for underwater recovery of the AUV.

Study on Hydrodynamic Performance of a Dish-Shaped Underwater Vehicle

2010 ◽  
Author(s):  
Yumin Su ◽  
Zhaoli Wang
Keyword(s):  
Numerical Method ◽  
Processing System ◽  
Least Square Method ◽  
Underwater Vehicle ◽  
Least Square ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Coefficients ◽  
Post Processing ◽  
Motion Mechanism ◽  
Planar Motion Mechanism

A new kind of dish-shaped underwater vehicle was designed. The maneuverability of the dish-shaped underwater vehicle (UV) is predicted in this paper. Hydrodynamic coefficients of the vehicle were calculated in numerically. The numerical method applied is one of the tools available in the commercial computational fluid dynamics software FLUENT. The dynamic mesh system and post-processing system are adopted in the numerical method. By simulating numerically straight motion, inclined motion and planar motion mechanism (PMM) experiment, the hydrodynamic performance in different states were obtained. Based on the least square method, the hydrodynamic coefficients of maneuverability were obtained. The calculated results indicate that the numerical method is suitable.

scholarly journals Thrust Prediction of an Active Flapping Foil in Waves Using CFD

2019 ◽  
Vol 7 (11) ◽  
pp. 396
Author(s):  
Rupesh Kumar ◽  
Hyunkyoung Shin
Keyword(s):  
Wave Energy ◽  
Thrust Force ◽  
Short Wave ◽  
Floating Structures ◽  
Flapping Foil ◽  
Short Waves ◽  
Computational Fluid Dynamics Cfd ◽  
Numerical Tool ◽  
Flapping Foils ◽  
Ansys Workbench

A horizontally submerged passive flapping foil can generate thrust force against the wave propagation using wave energy. This renewable method has been used for the design of propulsion and maneuvering systems of ships and other floating structures. Recently, the passive flapping foils were applied to design the station-keeping system of deep-water floaters. Studies proved that the passively flapping foil system was ineffective in short waves and drift of the floater beyond the design limit was recorded. Therefore, an active flapping foil was investigated as a potential solution to this problem. A computational fluid dynamics (CFD) numerical tool “ANSYS Workbench 19.2” was used to predict the thrust force generated by the active flapping foil in a short wave. Results proved that the active flapping foil can effectively convert wave energy into propulsive energy in short waves and the magnitude of the thrust force depends on the flapping frequency.

scholarly journals A Hydrodynamic Methodology And CFD Analysis For Performance Prediction Of Stepped Planing Hulls

2015 ◽  
Vol 22 (2) ◽  
pp. 23-31 ◽  
Author(s):  
Hassan Ghassemi ◽  
Mojtaba Kamarlouei ◽  
Sajad Taj Golah Veysi
Keyword(s):  
High Speed ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Geometrical Parameters ◽  
Cfd Analysis ◽  
Analysis Model ◽  
Marine Coatings ◽  
Resistance Reduction ◽  
Calculation Results ◽  
Fruitful Research

AbstractNowadays all efforts in planing hull research are focused on resistance reduction for achieving the highest speed in fast planing crafts. Furthermore, many fruitful research projects have been carried out on marine coatings, planing equipment, and optimization of propeller and hull form, which revolutionized industry of high - speed crafts and made them an efficient survival vehicle in coastal areas and rivers. In this paper the hydrodynamic performance of planing hulls are investigated by means of a modified Savitsky model for both non-stepped and stepped bodies. Meanwhile, in order to meet this goal reasonably, effective geometrical parameters of planing hull are investigated and then operational hydrodynamic characteristics of the craft are predicted by using a computational program. Finally, the calculation results are verified by means of a CFD-analysis model.

Influence of Donut-Shaped Bump on the Hydrodynamic Lubrication of Textured Parallel Sliders

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Hao Fu ◽  
Jinghu Ji ◽  
Yonghong Fu ◽  
Xijun Hua
Keyword(s):  
Hydrodynamic Lubrication ◽  
Three Dimensional ◽  
Hydrodynamic Pressure ◽  
Hydrodynamic Performance ◽  
Geometrical Parameters ◽  
Textured Surfaces ◽  
Bump Height ◽  
Lubrication Performance ◽  
Parallel Surfaces ◽  
Vertical Spacing

The influence of donut-shaped bump texture on the hydrodynamic lubrication performance for parallel surfaces is presented in this paper. A mathematical equation has been applied to express the shape of three-dimensional donut-shaped bump texture. Numerical simulation of the pressure distribution of lubricant between a textured slider and a smooth, moving slider has been performed to analyze the geometrical parameters' influence on the hydrodynamic performance for textured surfaces. The numerical results show that the convex of the donut-shaped bump provides a microstep slider, which can form a convergent wedge and build up hydrodynamic pressure. Optimum values of horizontal spacing and bump height are obtained to maximize the hydrodynamic pressure. It is also noted that the average pressure increases monotonically with the increase of bump radius, but decreases with the increase of vertical spacing and dimple depth, respectively.

scholarly journals Effects of Geometrical Parameters of Internal Blown Flap and Its Optimal Design

2020 ◽  
Vol 38 (1) ◽  
pp. 58-67
Author(s):  
Rui Liu ◽  
Junqiang Bai ◽  
Yasong Qiu ◽  
Guozhu Gao
Keyword(s):  
Optimal Design ◽  
Design Method ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Chord Length ◽  
Geometrical Parameters ◽  
Design Constraint ◽  
Design Variables ◽  
Flap Deflection ◽  
Stall Angle

The internal blown flap was numerically simulated. Firstly, a parameterization method was developed, which can properly describe the shape of the internal blown flap according to such geometrical parameters as flap chord length, flap deflection, height of blowing slot and its position. Then the reliability of the numerical simulation was validated through comparing the pressure distribution of the CC020-010EJ fundamental generic circulation control airfoil with the computational results and available experiment results. The effects of the geometrical parameters on the aerodynamic performance of the internal blown flap was investigated. The investigation results show that the lift coefficient increases with the increase of flap chord length and flap deflection angle and with the decrease of height of blowing slot and its front position. Lastly, a method of optimal design of the geometrical parameters of the internal blown flap was developed. The design variables include flap chord length, flap deflection, height of blowing slot and its position. The optimal design is based on maximum lift coefficient, the angle of attack of 5 degrees and the design constraint of stall angle of attack of less than 9 degrees. The optimization results show that the optimal design method can apparently raise the lift coefficient of an internal blown flap up to 1.7.

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