scholarly journals Effects of Regular Waves on Propulsion Performance of Flexible Flapping Foil

2018 ◽  
Vol 8 (6) ◽  
pp. 934 ◽  
Author(s):  
Peng Liu ◽  
Yebao Liu ◽  
Shuling Huang ◽  
Jianfeng Zhao ◽  
Yumin Su
Keyword(s):  
Regular Waves ◽  
Flapping Foil ◽  
Propulsion Performance

scholarly journals Propulsion Performance of the Full-Active Flapping Foil in Time-Varying Freestream

2020 ◽  
Vol 10 (18) ◽  
pp. 6226
Author(s):  
Zhanfeng Qi ◽  
Lishuang Jia ◽  
Yufeng Qin ◽  
Jian Shi ◽  
Jingsheng Zhai
Keyword(s):  
Flow Velocity ◽  
Steady Flow ◽  
Navier Stokes ◽  
Time Varying ◽  
Flapping Foil ◽  
Propulsion Performance ◽  
Reduced Frequency ◽  
Motion Parameters ◽  
Volume Method ◽  
The Impact

A numerical investigation of the propulsion performance and hydrodynamic characters of the full-active flapping foil under time-varying freestream is conducted. The finite volume method is used to calculate the unsteady Reynolds averaged Navier–Stokes by commercial Computational Fluid Dynamics (CFD) software Fluent. A mesh of two-dimensional (2D) NACA0012 foil with the Reynolds number Re = 42,000 is used in all simulations. We first investigate the propulsion performance of the flapping foil in the parameter space of reduced frequency and pitching amplitude at a uniform flow velocity. We define the time-varying freestream as a superposition of steady flow and sinusoidal pulsating flow. Then, we study the influence of time-varying flow velocity on the propulsion performance of flapping foil and note that the influence of the time-varying flow is time dependent. For one period, we find that the oscillating amplitude and the oscillating frequency coefficient of the time-varying flow have a significant influence on the propulsion performance of the flapping foil. The influence of the time-varying flow is related to the motion parameters (reduced frequency and pitching amplitude) of the flapping foil. The larger the motion parameters, the more significant the impact of propulsion performance of the flapping foil. For multiple periods, we note that the time-varying freestream has little effect on the propulsion performance of the full-active flapping foil at different pitching amplitudes and reduced frequency. In summary, we conclude that the time-varying incoming flow has little effect on the flapping propulsion performance for multiple periods. We can simplify the time-varying flow to a steady flow field to a certain extent for numerical simulation.

scholarly journals On movement control of deformable hull for displacement ship in waves

2020 ◽  
Vol S-I (2) ◽  
pp. 237-241
Author(s):  
R. Mudrik ◽  
◽  
P. Mudrik ◽  
Keyword(s):  
Target Function ◽  
Bending Moment ◽  
Movement Control ◽  
Irregular Waves ◽  
Regular Waves ◽  
Propulsion Performance ◽  
Design Variables ◽  
Internal Forces ◽  
Wave Induced

This paper discusses the optimization of ship heading in given regular waves taking into account the limitations for wave-induced midship bending moment and roll amplitude. External and internal forces in irregular waves are determined as per finite-element method used for motion calculations. This study presents the obtained surfaces of responses for the variables of state depending on wave parameters and design variables. The optimization problem discussed in this study was solved taking the non-linearity of target function and limitation functions into account. the study also formulated and solved an inverse problem, i.e. determination of controlling parameters (heading and speed) so as to obtain optimal propulsion performance in given wave conditions without prejudice to reliability and seakeeping.

scholarly journals Effects of time-varying flexibility on the propulsion performance of a flapping foil

2020 ◽  
Vol 32 (12) ◽  
pp. 121904
Author(s):  
Guangyu Shi ◽  
Qing Xiao ◽  
Qiang Zhu
Keyword(s):  
Time Varying ◽  
Flapping Foil ◽  
Propulsion Performance

scholarly journals The Effect of Mass Ratio and Damping Coefficient on the Propulsion Performance of the Semi-Active Flapping Foil of the Wave Glider

2020 ◽  
Vol 8 (5) ◽  
pp. 303
Author(s):  
Zhanfeng Qi ◽  
Min Jiang ◽  
Lishuang Jia ◽  
Bo Zou ◽  
Jingsheng Zhai
Keyword(s):  
Output Power ◽  
Damping Coefficient ◽  
Power Coefficient ◽  
Mass Ratio ◽  
Propulsion Efficiency ◽  
Flapping Foil ◽  
Propulsion Performance ◽  
Reduced Frequency ◽  
The Mean ◽  
Wave Glider

A numerical investigation on the propulsion performance of the semi-active flapping foil of the wave glider with different mass ratio and damping coefficient is investigated. The commercial CFD software Fluent is used to solve the URANS equations around the flapping foil by the Finite Volume Method. A mesh of 2D NACA0012 foil with the Reynolds number Re = 42,000 is used in all simulations. We first analyze the effect of the mass ratio on the mean output power coefficient and propulsion efficiency and note that with the variation of the mass ratio, the propulsion efficiency decreases slightly. Besides, we find that the mass ratio has a noticeable influence on the mean output power coefficient, and the influence is determined by the reduced frequency. For high reduced frequency, with the increase of the mass ratio, the propulsion performance of the flapping foil decreases monotonously. For low reduced frequency, the mean output power increases slightly. For critically reduced frequency, the mean output power coefficient of the foil firstly increases and then decreases via the mass ratio increase. Then, we examine the influence of the damping coefficient on the propulsion performance of the flapping foil and find that the damping coefficient has a severe adverse effect on the output power and propulsion efficiency. We conclude that the influence of the damping coefficient should be considered first when we design the propulsion device of the semi-active flapping foil. Meanwhile, we should also consider the sea conditions to choose the mass ratio to optimize the flapping foil.

A proposal for propulsion performance prediction of a single-propeller twin-rudder ship

2009 ◽  
Vol 14 (3) ◽  
pp. 296-309 ◽  
Author(s):  
Vishwanath Nagarajan ◽  
Dong-Hoon Kang ◽  
Kazuhiko Hasegawa ◽  
Kenjiro Nabeshima ◽  
Toshihiko Arii
Keyword(s):  
Performance Prediction ◽  
Propulsion Performance

scholarly journals Time Scale for Scour Beneath Pipelines Due to Long-Crested and Short-Crested Nonlinear Random Waves Plus Current

2021 ◽  
Vol 9 (2) ◽  
pp. 114
Author(s):  
Dag Myrhaug ◽  
Muk Chen Ong
Keyword(s):  
Time Scale ◽  
Current Flow ◽  
Irregular Waves ◽  
Wave Crest ◽  
Random Wave ◽  
Random Waves ◽  
Flow Conditions ◽  
Regular Waves ◽  
Nonlinear Random Waves ◽  
2D And 3D

This article derives the time scale of pipeline scour caused by 2D (long-crested) and 3D (short-crested) nonlinear irregular waves and current for wave-dominant flow. The motivation is to provide a simple engineering tool suitable to use when assessing the time scale of equilibrium pipeline scour for these flow conditions. The method assumes the random wave process to be stationary and narrow banded adopting a distribution of the wave crest height representing 2D and 3D nonlinear irregular waves and a time scale formula for regular waves plus current. The presented results cover a range of random waves plus current flow conditions for which the method is valid. Results for typical field conditions are also presented. A possible application of the outcome of this study is that, e.g., consulting engineers can use it as part of assessing the on-bottom stability of seabed pipelines.

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