scholarly journals EVALUATION OF THE ADDED RESISTANCE AND SHIP MOTIONS COUPLED WITH SLOSHING USING POTENTIAL FLOW THEORY

Brodogradnja ◽  
2016 ◽  
Vol 67 (4) ◽  
pp. 109-122
Author(s):  
Ivana Martić ◽  
◽  
Nastia Degiuli ◽  
Ivan Ćatipović
Keyword(s):  
Potential Flow ◽  
Flow Theory ◽  
Ship Motions ◽  
Added Resistance ◽  
Potential Flow Theory

Implementation of Linear Potential-Flow Theory in the 6DOF Coupled Simulation of Ship Collision and Grounding Accidents

2016 ◽  
Vol 60 (03) ◽  
pp. 119-114
Author(s):  
Zhaolong Yu ◽  
Yugao Shen ◽  
Jørgen Amdahl ◽  
Marilena Greco
Keyword(s):  
Potential Flow ◽  
Structural Damage ◽  
Flow Theory ◽  
Ship Motions ◽  
Linear Potential ◽  
Hydrodynamic Loads ◽  
Potential Flow Theory ◽  
Highly Nonlinear ◽  
Ship Collision ◽  
Fully Coupled

Ship collisions and groundings are highly nonlinear and transient, coupled dynamic processes involving large structural deformations and fluid structure interactions. It has long been difficult to include all effects in one simulation. By taking advantage of the user-defined load subroutine and the user common variable, this article implements a model of hydrodynamic loads based on linear potential-flow theory into the nonlinear finite element code LS-DYNA, facilitating a fully coupled six degrees of freedom (6DOF) dynamic simulation of ship collision and grounding accidents. Potential-flow theory both with and without considering the forward speed effect is implemented for studying the speed influence. With the proposed model, transient effects of the fluid, global ship motions, impact forces, and structural damage can all be predicted with high accuracy. To the authors' knowledge, this is the first time the fully coupled 6DOF collision and grounding simulations are carried out with linear hydrodynamic loads for transient conditions but without simplification of collision forces. The proposed method is applied to calculations of an offshore supply vessel colliding with a rigid plate and with a submersible platform. The results are compared with a decoupled method and discussed with emphasis on the influence of different initial velocities. The proposed method is capable of predicting both the 6DOF ship motions and structural damage simultaneously with good efficiency and accuracy; hence, it will be a very promising tool in the application to ship collision and grounding analysis.

Application of Potential Flow Theory to Plane-Strain Extrusion

1967 ◽  
Vol 89 (3) ◽  
pp. 503-511 ◽  
Author(s):  
A. Shabaik ◽  
S. Kobayashi ◽  
E. G. Thomsen
Keyword(s):  
Plane Strain ◽  
Potential Flow ◽  
Flow Line ◽  
Flow Theory ◽  
Flow Fields ◽  
Potential Flow Theory ◽  
Good Agreement

Theoretical and experimental flow fields of several extrusion ratios of lead in plane strain were compared. It was found that, for extrusion ratios where dead metal exists, the agreement between the potential and experimental flow nets was better for small reductions when a modified boundary approaching a flow line was used. It was also found that when the flow changed direction gradually, the potential flow net was in good agreement with the experimental one. The solution obtained is unique and complete.

Passing Ship Effects in Non-Uniform Water Depth

2016 ◽  
Author(s):  
Lilan Zhou ◽  
Ji Yang ◽  
Qian Wang ◽  
Jiangtao Qin
Keyword(s):  
Time Domain ◽  
Potential Flow ◽  
Flow Model ◽  
Flow Theory ◽  
Propagation Model ◽  
Beach Erosion ◽  
Wave Flow ◽  
Generation Model ◽  
Theory Method ◽  
Potential Flow Theory

Waves generated by passing ships have potential adverse impacts on the environment (beach erosion, ecological disturbance, structures damage) and other waterway users (navigations, moored ships) in the coastal and sheltered areas. But issues related to waves of ships were addressed rarely in China until now. Accurate prediction of wash waves is the first step to control the washes from passing ships and it’s significant to reduce the effects of washes. A coupled method is used in this paper to simulate the washes and its effects caused by the passing ship. A potential flow theory method is adopted as the stationary wave generation model; a non-hydrostatic wave flow model is used as the wave propagation model; a time domain method is chosen as the model for simulating the forces and moments of mooring ship. The waves calculated by a potential flow theory method in the near field are used as the input for the non-hydrostatic wave-flow model to obtain the far field waves. A time-domain representation of the wave-cut at the location of the passing vessel is transformed to the frequency-domain and is used as the input for the diffraction computations. Parts of the calculated results are validated experimentally, satisfactory agreement is demonstrated.

Study on the Dynamics of the Bubble under the Combined Action of the Bjerknes Effect of the Free Surface and the Buoyancy

2014 ◽  
Vol 644-650 ◽  
pp. 628-631
Author(s):  
Ke Yi Li ◽  
Zhong Cai Pei
Keyword(s):  
Free Surface ◽  
Boundary Element Method ◽  
Boundary Element ◽  
Potential Flow ◽  
Flow Theory ◽  
Motion Direction ◽  
Potential Flow Theory ◽  
Combined Action ◽  
Element Method

When the bubble moves in the vicinity of a free surface, the movement will be affected by the buoyancy and the Bjerknes effect. Blake and Gibson proposed the criterion which determined the motion direction of the jet and the dynamics of bubble. They proposed the jet wouldn’t be formed in the condition that . Based on the potential flow theory, boundary element method (BEM) is used to calculate three typical examples in this paper in order to study the dynamics of the bubble under the combined action of the Bjerknes effect of the free surface and the buoyancy. It is found out during the analysis that the Blake criterion is applicable to predict the conditions that and .

Study on the Aerodynamics Mechanism of Passenger Car under Unsteady Crosswind

2013 ◽  
Vol 631-632 ◽  
pp. 809-816
Author(s):  
Chen Shen ◽  
Hui Zhu ◽  
Zhi Gang Yang
Keyword(s):  
Empirical Formula ◽  
Potential Flow ◽  
Aerodynamic Force ◽  
Vortex Motion ◽  
Flow Theory ◽  
Potential Flow Theory ◽  
Practical Engineering ◽  
Precise Prediction ◽  
Engineering Significance ◽  
Semi Empirical

Regular formulae for lateral aerodynamic force cannot give precise prediction under unsteady crosswind. By generalizing potential flow theory and taking the aerodynamic derivative into consideration, the semi-empirical expression for lateral aerodynamic force is derived. In order to determine the coefficients in the semi-empirical formula, the model of a typical double-deck coach is investigated in a sequence of numerical simulations under pure crosswind condition (i.e. linear crosswind, pseudo-step crosswind, sinusoidal crosswind). Moreover, advantages of the semi-empirical formula over the regular one are revealed. Further inspections into the flow field derived from the theory of vortex motion indicate that the deviation between the prediction given by semi-empirical formulae and that by numerical simulation is caused by the non-viscous assumption in potential flow theory. The lateral aerodynamic force depends linearly on the crosswind aerodynamic derivative. Situations in which the coach is moving in the direction perpendicular to the wind velocity are also studied to find the cause of the error in semi-empirical formula. Furthermore, the semi-empirical formula is revised by introducing the “damping model method”. A relatively complete system of prediction for lateral aerodynamic force on a coach, which is of practical engineering significance, has been constructed.

Hybrid Method for Predicting Ship Manoeuvrability in Regular Waves

2019 ◽  
Author(s):  
Tianlong Mei ◽  
Yi Liu ◽  
Manasés Tello Ruiz ◽  
Marc Vantorre ◽  
Evert Lataire ◽  
...  
Keyword(s):  
Experimental Data ◽  
Hybrid Method ◽  
Potential Flow ◽  
Flow Theory ◽  
Regular Waves ◽  
Potential Flow Theory ◽  
Hydrodynamic Derivatives ◽  
Mmg Model ◽  
Calm Water ◽  
Wave Induced

Abstract The ship’s manoeuvring behaviour in waves is significantly different from that in calm water. In this context, the present work uses a hybrid method combining potential flow theory and Computational Fluid Dynamics (CFD) techniques for the prediction of ship manoeuvrability in regular waves. The mean wave-induced drift forces are calculated by adopting a time domain 3D higher-order Rankine panel method, which includes the effect of the lateral speed and forward speed. The hull-related hydrodynamic derivatives are determined based on a RANS solver using the double body flow model. The two-time scale method is applied to integrate the improved seakeeping model in a 3-DOF modular type Manoeuvring Modelling Group (MMG model) to investigate the ship’s manoeuvrability in regular waves. Numerical simulations are carried out to predict the turning circle in regular waves for the S175 container carrier. The turning circle’s main characteristics as well as the wave-induced motions are evaluated. A good agreement is obtained by comparing the numerical results with experimental data obtained from existing literature. This demonstrates that combining potential flow theory with CFD techniques can be used efficiently for predicting the manoeuvring behaviour in waves. This is even more true when the manoeuvring derivatives cannot be obtained from model tests when there is lack of such experimental data.

Sign in / Sign up

Export Citation Format

Share Document