scholarly journals Bulbous bow applications on a catamaran fishing vessel for improving performance

2018 ◽  
Vol 159 ◽  
pp. 02057 ◽  
Author(s):  
Samuel ◽  
Dong-Joon Kim ◽  
Muhammad Iqbal ◽  
Aldias Bahatmaka ◽  
Aditya Rio Prabowo
Keyword(s):  
Finite Element Method ◽  
Fluid Dynamic ◽  
Wave Resistance ◽  
Total Resistance ◽  
Fishing Vessel ◽  
Dynamic Approach ◽  
Slender Body Theory ◽  
Vessel Resistance ◽  
Bulbous Bow ◽  
Body Theory

This study aims to prove the usefulness of a bulbous bow traditional catamaran fishing vessel. Bulbous bow applications are widely used to reduce wave resistance. The fishing vessel resistance was calculated using CFD (Computational Fluid Dynamic) approach and combined with classical slender body theory. In this research, the application of bulbous bow was being adopted on traditional catamaran fishing vessel to reduce the total resistance. The bulbous bow has adopted based on Kracht method. Modeling procedure was developed by using linear form coefficients. The ship resistance was simulated using Tdyn software which basically Finite Element Method. The results show that adding bulbous bow can decrease or increase the ship’s total resistance.

scholarly journals Analysis of Effect of Bulbous Bow Shape to Ship Resistance in Catamaran Boat

2018 ◽  
Vol 159 ◽  
pp. 02058
Author(s):  
Deddy Chrismianto ◽  
Kiryanto ◽  
Berlian Arswendo Adietya
Keyword(s):  
Fluid Dynamic ◽  
The Body ◽  
Wave System ◽  
Total Resistance ◽  
Factors Affecting ◽  
Ship Resistance ◽  
Bow Wave ◽  
Main Factors ◽  
The One ◽  
Bulbous Bow

Ship resistance is one of the main factors affecting the design of a ship. Catamaran boat is a ship with small wet surface area that able to reduce drag and improve ship power. Generally, a bulbous bow is implemented to reduce wave resistance because the bulbous shape is believed to attenuate the bow wave system. Additionally, the bulbous bow also tends to reduce viscous resistance. When the flow around the body is smooth, the total ship resistance can be reduced significantly if the optimum bulbous bow is obtained. In this study, the main purpose is to get the bulbous bow shape in catamaran boat which produces the smallest ship resistance by using computational fluid dynamic (CFD). Generating the variation of the bulbous bow shapes apply the one-to-one correspondence of the cross section parameter (ABT) and lateral parameter (ABL). The result of investigation shows that application of bulbous bow on catamaran boat can reduce about 11-13% of total resistance of ship.

A Wave Resistance Formulation for Slender Bodies at Moderate to High Speeds

2012 ◽  
Vol 56 (04) ◽  
pp. 207-214
Author(s):  
Brandon M. Taravella ◽  
William S. Vorus
Keyword(s):  
General Solution ◽  
High Speed ◽  
Near Field ◽  
Wave Resistance ◽  
Slender Body ◽  
Slender Body Theory ◽  
Rates Of Change ◽  
Order Of Magnitude ◽  
Flow Variables ◽  
Body Theory

T. Francis Ogilvie (1972) developed a Green's function method for calculating the wave profile of slender ships with fine bows. He recognized that near a slender ship's bow, rates of change of flow variables axially should be greater than those typically assumed in slender body theory. Ogilvie's result is still a slender body theory in that the rates of change in the near field are different transversely (a half-order different) than axially; however, the difference in order of magnitude between them is less than in the usual slender body theory. Typical of slender body theory, this formulation results in a downstream stepping solution (along the ship's length) in which downstream effects are not reflected upstream. Ogilvie, however, developed a solution only for wedge-shaped bodies. Taravella, Vorus, and Givan (2010) developed a general solution to Ogilvie's formulation for arbitrary slender ships. In this article, the general solution has been expanded for use on moderate to high-speed ships. The wake trench has been accounted for. The results for wave resistance have been calculated and are compared with previously published model test data.

Propulsive Efficiency of the Underwater Dolphin Kick in Humans

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Alfred von Loebbecke ◽  
Rajat Mittal ◽  
Frank Fish ◽  
Russell Mark
Keyword(s):  
Fluid Dynamic ◽  
Three Dimensional ◽  
Underwater Video ◽  
Dynamic Simulations ◽  
Slender Body Theory ◽  
Propulsive Efficiency ◽  
Video Footage ◽  
Wide Range ◽  
Dolphin Kick ◽  
Body Theory

Three-dimensional fully unsteady computational fluid dynamic simulations of five Olympic-level swimmers performing the underwater dolphin kick are used to estimate the swimmer’s propulsive efficiencies. These estimates are compared with those of a cetacean performing the dolphin kick. The geometries of the swimmers and the cetacean are based on laser and CT scans, respectively, and the stroke kinematics is based on underwater video footage. The simulations indicate that the propulsive efficiency for human swimmers varies over a relatively wide range from about 11% to 29%. The efficiency of the cetacean is found to be about 56%, which is significantly higher than the human swimmers. The computed efficiency is found not to correlate with either the slender body theory or with the Strouhal number.

scholarly journals Continuity with respect to the speed for optimal ship forms based on Michell's formula

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Author(s):  
Julien Dambrine ◽  
Morgan Pierre
Keyword(s):  
Drag Coefficient ◽  
Froude Number ◽  
Nonnegative Function ◽  
Wave Resistance ◽  
Viscous Drag ◽  
Total Resistance ◽  
Hull Design ◽  
Bulbous Bow ◽  
Two Parameters ◽  
Theoretical Results

<p style='text-indent:20px;'>We consider a ship hull design problem based on Michell's wave resistance. The half hull is represented by a nonnegative function and we seek the function whose domain of definition has a given area and which minimizes the total resistance for a given speed and a given volume. We show that the optimal hull depends only on two parameters without dimension, the viscous drag coefficient and the Froude number of the area of the support. We prove that, up to uniqueness, the optimal hull depends continuously on these two parameters. Moreover, the contribution of Michell's wave resistance vanishes as either the Froude number or the drag coefficient goes to infinity. Numerical simulations confirm the theoretical results for large Froude numbers. For Froude numbers typically smaller than <inline-formula><tex-math id="M1">\begin{document}$ 1 $\end{document}</tex-math></inline-formula>, the famous bulbous bow is numerically recovered. For intermediate Froude numbers, a "sinking" phenomenon occurs. It can be related to the nonexistence of a minimizer.</p>

A Wave Resistance Formulation for Slender Bodies With Fine Bow Shapes

2010 ◽  
Author(s):  
Brandon M. Taravella ◽  
William S. Vorus ◽  
Daniel R. Givan
Keyword(s):  
Near Field ◽  
Surface Profile ◽  
Wave Resistance ◽  
Slender Body ◽  
Slender Body Theory ◽  
Rates Of Change ◽  
Order Of Magnitude ◽  
The Difference ◽  
Flow Variables ◽  
Body Theory

Ogilvie (1972) investigated a Green’s function method for calculating the wave profile of slender ships with fine bows. He recognized that near a slender ship’s bow, rates of change of flow variables axially should be greater than those typically assumed in slender body theory. Ogilvie’s (1972) result is still a slender body theory in that the rates of change in the near field are different transversely (a half-order) than axially; however, the difference in order of magnitude between them is less than in the usual slender body theory. Typical of slender body theory, this formulation results in a downstream stepping solution (along the ship’s length) in which downstream effects are not reflected upstream. Ogilvie (1972), however, only developed a solution for wedge-shaped bodies. In this paper, a general solution for arbitrary slender ships has been developed based on Ogilvie’s (1972) formulation. The results for wave resistance have been calculated and are compared to previously published model test data and calculated results. The free surface profile has also been calculated.

Note on the swimming of slender fish

1960 ◽  
Vol 9 (2) ◽  
pp. 305-317 ◽  
Author(s):  
M. J. Lighthill
Keyword(s):  
Swimming Speed ◽  
Critical Value ◽  
Slender Body ◽  
Vortex Wake ◽  
Frictional Drag ◽  
Slender Body Theory ◽  
Propulsive Efficiency ◽  
Deformable Bodies ◽  
Work Done ◽  
Body Theory

The paper seeks to determine what transverse oscillatory movements a slender fish can make which will give it a high Froude propulsive efficiency, $\frac{\hbox{(forward velocity)} \times \hbox{(thrust available to overcome frictional drag)}} {\hbox {(work done to produce both thrust and vortex wake)}}.$ The recommended procedure is for the fish to pass a wave down its body at a speed of around $\frac {5} {4}$ of the desired swimming speed, the amplitude increasing from zero over the front portion to a maximum at the tail, whose span should exceed a certain critical value, and the waveform including both a positive and a negative phase so that angular recoil is minimized. The Appendix gives a review of slender-body theory for deformable bodies.

Slender-body theory for slow viscous flow

1976 ◽  
Vol 75 (4) ◽  
pp. 705-714 ◽  
Author(s):  
Joseph B. Keller ◽  
Sol I. Rubinow
Keyword(s):  
Integral Equation ◽  
Incompressible Fluid ◽  
Viscous Incompressible Fluid ◽  
Unit Length ◽  
The Body ◽  
Slender Body ◽  
Slow Flow ◽  
Slender Body Theory ◽  
Slow Viscous Flow ◽  
Body Theory

Slow flow of a viscous incompressible fluid past a slender body of circular crosssection is treated by the method of matched asymptotic expansions. The main result is an integral equation for the force per unit length exerted on the body by the fluid. The novelty is that the body is permitted to twist and dilate in addition to undergoing the translating, bending and stretching, which have been considered by others. The method of derivation is relatively simple, and the resulting integral equation does not involve the limiting processes which occur in the previous work.

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