Numerical investigation on semi-active flapping foil for marine propulsion

Name: Nonthipat Thaweewat

LCSH: Kasetsart University -- Dissertations. D.Eng. (Mechanical Engineering) 2018

Classification :.LCCS: VM751

LCSH: Kasetsart University. -- Department of Mechanical Engineering -- Dissertations

LCSH: Ship propulsion

LCSH: Marine engines

LCSH: Remote submersibles

Abstract: A potential flow code is used to simulate the flow around a semi-active flapping foil of which the kinematics is characterized by an imposed sinusoidal heave motion and a free pitch motion. A torsion spring is attached to the foil and acts to restore the foil parallel to the advance velocity. The solver has been validated by a comparison between force coefficients obtained from the employed BEM code and a viscous solver. The results show that the semi-active flapping propulsor has its openwater characteristics similar to that of a variable-pitch propeller which is efficient over a wide range of loads and operating conditions. An optimal performance exists at an intermediate value of spring stiffness. The rigid spring strongly resists the foil from pitching leading to high heave force required to drive the foil, while the elastic spring insufficiently provides restoring force resulting in a momentary undesired pitch direction and hence temporary drag production. A proper spring avoids the mentioned mechanisms and gives optimal performance. Moreover, the simulation results demonstrate that the best efficiency of the semi-active flapping foil takes place in the same range of Strouhal number and pitch amplitude as observed in the natural world. Initially, the resonance mechanism seems to be less relevant to the openwater propulsive efficiency. However, a more detailed investigation is performed in order to clarify the effects of foil inertia and resonance. The peak efficiencies occur approximately at an identical advance number and also correspond to the same pitch amplitude in spite of different inertia. The estimated added inertia suggests that the immersed resonance seemingly corresponds to the optimal performance. On the other hand, it has been found that the structural resonance is a critical condition yielding identical characteristics regardless the foil inertia. The results also confirm that the semi-active flapping foil performs efficiently over wide ranges of kinematic and mechanical conditions. Moreover, an evidence has been found that the foil could also perform as an energy harvester in a certain range of operating condition.

Kasetsart University. Office of the University Library

Address: Bangkok

Email: tdckulib@ku.ac.th

Name: Varangrat Juntasaro

Role: Thesis Advisor

Name: Surasak Phoemsapthawee

Role: Thesis CO-Advisor

Created: 2018

Modified: 2025-07-02

Issued: 2025-07-02

วิทยานิพนธ์/Thesis

application/pdf

URL: https://www.lib.ku.ac.th/KUthesis/2561/nonthipat-tha-all.pdf

CallNumber: VM751 .N66

eng

DegreeName: Doctor of Engineering

Level: Doctoral Degree

Descipline: Mechanical Engineering

Grantor: Kasetsart University

©copyrights Kasetsart University

ลำดับที่.	ชื่อแฟ้มข้อมูล	ขนาดแฟ้มข้อมูล	จำนวนเข้าถึง	วัน-เวลาเข้าถึงล่าสุด
1	nonthipat-tha-all.pdf	17.11 MB

ใช้เวลา

0.047684 วินาที