Non-Linear Effects of Roll Damping Tanks on Ship Motions

2006 ◽  
Author(s):  
Carsten Schumann ◽  
Ricardo Pereira
Keyword(s):  
Free Surface ◽  
Numerical Methods ◽  
Linear Time ◽  
Ship Motions ◽  
Response Curves ◽  
Roll Damping ◽  
Time Simulation ◽  
Non Linear ◽  
Linear Effects

This article describes the application of two numerical methods of computing the flow in u-tube and free surface roll damping tanks. These methods account for the most important non-linear effects in tank flows. i) The programs based on these methods are integrated in a non-linear time simulation strip program. ii) Response curves of tanks are computed with the mentioned tank programs and the results are incorporated in a linear strip program. iii) With both strip programs (linear and non-linear), sea keeping computations are carried out and the results are compared.

Non Linear Effect on Wave-Induced Loads for Hull Structural Design: Bulk Carrier, Container Carrier, Vehicles Carrier

2020 ◽  
Author(s):  
Kei Sugimoto ◽  
Yusuke Fukumoto ◽  
Junya Matsuwaki ◽  
Tatsuya Akamatsu ◽  
Shinsaku Ashida ◽  
...  
Keyword(s):  
Hydrodynamic Pressure ◽  
Irregular Waves ◽  
Structural Safety ◽  
Sensor Technology ◽  
Ship Motions ◽  
Bulk Carrier ◽  
Structural Rules ◽  
Linear Effect ◽  
Non Linear ◽  
Linear Effects

Abstract The structural rules of classification societies typically specify various loads corresponding to the most severe sea states which are expected to be encountered by a ship throughout her service life in order to ensure ship structural safety, and these rules also usually define a variety of simplified formulae to aid in the calculation of such loads. In most cases, such formulae have been developed using linear seakeeping codes and linear statistical predictions; such methods, however, do not typically take into account some complex phenomena due to theoretical and methodological limitations. For this reason, the use of values obtained through linear theory alone is often not sufficient to properly evaluate structural strength, and it is, therefore, necessary to consider other things such as non-linear effects and operational effects. Although the structural rules of classification societies normally take into account such effects, most of them generally treat such things simply as either a constant coefficient or as an implicit condition because of the difficulty of expressing such effects mathematically (i.e. as specific formulae) as well as a general lack of prior research related to such effects. In this paper, the authors present the results of tank tests and numerical calculations carried out in regular and irregular waves using a bulk carrier, a container carrier and a vehicles carrier, and discuss possible ways of improving the non-linear coefficients specified in the IACS Common Structural Rules (CSR) [1]. Load states, including their non-linear effects, were investigated by examining the behavior of ship motions and hydrodynamic pressure. In order to investigate the behavior of pressure in detail, the pressure acting upon the hull surfaces of the target ships was measured at over 300 locations using a FBG sensor, the latest in optical fiber sensor technology [2].

Five Years of Numerical Naval Ship Hydrodynamics at DTNSRDC

1981 ◽  
Vol 25 (04) ◽  
pp. 219-235
Author(s):  
Nils Salvesen
Keyword(s):  
Free Surface ◽  
Numerical Methods ◽  
Initial Period ◽  
Three Dimensional ◽  
Hydrodynamic Performance ◽  
Ship Motions ◽  
Surface Boundary ◽  
Local Flow ◽  
Ship Hydrodynamics ◽  
Naval Ship

In 1974 the Numerical Naval Ship Hydrodynamics Program was established at the David W. Taylor Naval Ship Research and Development Center. The objective of the program is to develop new numerical methods which can be used to evaluate those hydrodynamic performance characteristics which cannot be satisfactorily predicted by traditional methods. In this paper, the accomplishments during the first five-year period (1974–1979) are discussed. During this initial period, the effort was devoted entirely to naval ship free-surface problems. Several successful methods have been developed for solving fully three-dimensional ship-motions, ship-wave-resistance and local-flow problems using linearized free-surface boundary conditions. Numerical methods have also been developed for unsteady and steady two-dimensional problems where the exact free-surface conditions are satisfied. These new numerical methods are more accurate than the conventional computational methods and they can be used to analyze several naval free-surface problems which previously could only be investigated experimentally. It is concluded that the Numerical Naval Ship Hydrodynamics Program should include consideration of all areas in naval ship hydrodynamics where it is believed that the application of advanced numerical techniques and computers can result in better solution techniques.

NON LINEAR ANALYSIS OF SHIP MOTIONS AND LOADS IN LARGE AMPLITUDE WAVES

2021 ◽  
Vol 153 (A2) ◽  
Author(s):  
G Mortola ◽  
A Incecik ◽  
O Turan ◽  
S.E. Hirdaris
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Large Amplitude ◽  
Linear Time ◽  
Ship Motions ◽  
Wave Loads ◽  
Time Step ◽  
Strip Theory ◽  
Non Linear ◽  
The Time Domain

A non linear time domain formulation for ship motions and wave loads is presented and applied to the S175 containership. The paper describes the mathematical formulations and assumptions, with particular attention to the calculation of the hydrodynamic force in the time domain. In this formulation all the forces involved are non linear and time dependent. Hydrodynamic forces are calculated in the frequency domain and related to the time domain solution for each time step. Restoring and exciting forces are evaluated directly in time domain in a way of the hull wetted surface. The results are compared with linear strip theory and linear three dimensional Green function frequency domain seakeeping methodologies with the intent of validation. The comparison shows a satisfactory agreement in the range of small amplitude motions. A first approach to large amplitude motion analysis displays the importance of incorporating the non linear behaviour of motions and loads in the solution of the seakeeping problem.

The protestant ethic and the spirit of democracy: what is the democratic effect of Calvinism?

2014 ◽  
Vol 34 (9/10) ◽  
pp. 634-653
Author(s):  
Milan Zafirovski
Keyword(s):  
Social Structure ◽  
Sociological Theory ◽  
Negative Impact ◽  
Linear Time ◽  
Modern Society ◽  
Content Type ◽  
Linear Effect ◽  
Non Linear ◽  
Specific Position ◽  
Linear Effects

Purpose – The paper considers whether and how Calvinism as a specific type of religion, ideology, and social system impacts political democracy in modern society. In contrast to the previous sociological and related literature assuming only a positive or negative linear effect, the paper proposes that Calvinism exerts mixed positive-negative and non-linear effects on democracy. The purpose of this paper is to aim at making a contribution to the sociological theory and research on Calvinism and democracy and modern society in general. Design/methodology/approach – A combination of comparative and historical sociological methodology. Findings – The main proposition and finding is that whether Calvinism is likely to have a positive or negative impact on democracy is the function of its specific position within social structure and its concrete phase of development. Thus, different positions of Calvinism in social structure are linked to its differential consequences in aggregate for democracy, and various stages of its development to time-variable non-linear effects in sequence. Originality/value – This is a relatively novel finding innovating and expanding on the literature's assumption that Calvinism has a structurally uniform, either positive or negative, and linear, time-constant effect on democracy.

scholarly journals Numerical Investigation of Wave-Body Interactions in Shallow Water

2014 ◽  
Author(s):  
Yi Luo ◽  
Torgeir Vada ◽  
Marilena Greco
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Numerical Study ◽  
Surface Boundary ◽  
Regular Waves ◽  
Incoming Wave ◽  
Surface Boundary Conditions ◽  
First Case ◽  
Non Linear ◽  
Linear Effects

Present investigation is based on a numerical study using a time-domain Rankine panel method. The effort and novelty is to extend the applicability of the solver to shallower waters and to steeper waves by including additional non-linear effects, but in a way so to limit the increase in computational costs. The challenge is to assess the improvement with respect to the basic formulation and the recovery of linear theory in the limit of small waves. The wave theories included in the program are Airy, Stokes 5th order and Stream function. By their comparison the effect of the incoming-wave non-linearities can be investigated. For the free-surface boundary conditions two alternative formulations are investigated, one by Hui Sun [1] and one developed here. The two formulations combined with the above-mentioned wave theories are applied to two relevant problems. The first case is a fixed vertical cylinder in regular waves, where numerical results are compared with the model tests by Grue & Huseby [2]. The second case is a freely floating model of a LNG carrier (with zero forward speed) in regular waves, where computations are compared with the experimental results from the EC project “Extreme Seas”. This comparison revealed several challenges such as how to interpret/post process the experimental data. Some of these are described in the paper. After careful handling of both computed and measured data the comparisons show reasonable agreement. It is proven that including more non-linear effects in the free-surface boundary conditions can significantly improve the results. The formulation by Hui Sun gives better results compared to the linear condition, but the present formulation is shown to provide a further improvement, which can be explained through the nonlinear terms included/retained in the two approaches.

Nonlinear Ship Motions

1998 ◽  
Vol 42 (02) ◽  
pp. 120-130 ◽  
Author(s):  
Yifeng Huang ◽  
Paul D. Sclavounos
Keyword(s):  
Free Surface ◽  
Numerical Method ◽  
Time Domain ◽  
Linear Time ◽  
Ship Motions ◽  
Experimental Measurements ◽  
Approximate Theory ◽  
Nonlinear Method ◽  
Motion Responses ◽  
Nonlinear Solutions

A nonlinear numerical method has been developed to compute motion responses for a ship traveling in steep ambient waves. The method is based on an approximate theory and is an extension to a well-established linear time-domain numerical method. The nonlinear solution is found to be greatly improved over the classical linear and quasi-nonlinear solutions, in comparison to experimental measurements for conventional commercial ships. Through this study, it is also demonstrated that the free surface hydrodynamic nonlinearities are at least as important as, if not more than, the hydrostatic and Froude-Krylov nonlinearities. Stability, consistency and convergence for the nonlinear method are also addressed.

Glycemia monitoring

1998 ◽  
Vol 2 ◽  
pp. 23-30
Author(s):  
Igor Basov ◽  
Donatas Švitra
Keyword(s):  
Diabetes Mellitus ◽  
Mathematical Model ◽  
Numerical Methods ◽  
Differential Equations ◽  
Blood Sugar ◽  
Self Regulation ◽  
Physiological System ◽  
Non Linear ◽  
The Mathematical Model

Here a system of two non-linear difference-differential equations, which is mathematical model of self-regulation of the sugar level in blood, is investigated. The analysis carried out by qualitative and numerical methods allows us to conclude that the mathematical model explains the functioning of the physiological system "insulin-blood sugar" in both normal and pathological cases, i.e. diabetes mellitus and hyperinsulinism.

Prediction of Ship Motions Via a Three-Dimensional Time-Domain Method Following a Quad-Tree Adaptive Mesh Technique

2020 ◽  
Vol 27 (1) ◽  
pp. 29-38
Author(s):  
Teng Zhang ◽  
Junsheng Ren ◽  
Lu Liu
Keyword(s):  
Free Surface ◽  
Incident Wave ◽  
Time Domain ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
Wave Profile ◽  
Time Domain Method ◽  
Ship Motions ◽  
Quad Tree ◽  
Mesh Technique

AbstractA three-dimensional (3D) time-domain method is developed to predict ship motions in waves. To evaluate the Froude-Krylov (F-K) forces and hydrostatic forces under the instantaneous incident wave profile, an adaptive mesh technique based on a quad-tree subdivision is adopted to generate instantaneous wet meshes for ship. For quadrilateral panels under both mean free surface and instantaneous incident wave profiles, Froude-Krylov forces and hydrostatic forces are computed by analytical exact pressure integration expressions, allowing for considerably coarse meshes without loss of accuracy. And for quadrilateral panels interacting with the wave profile, F-K and hydrostatic forces are evaluated following a quad-tree subdivision. The transient free surface Green function (TFSGF) is essential to evaluate radiation and diffraction forces based on linear theory. To reduce the numerical error due to unclear partition, a precise integration method is applied to solve the TFSGF in the partition computation time domain. Computations are carried out for a Wigley hull form and S175 container ship, and the results show good agreement with both experimental results and published results.

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