Maneuvering Simulation of Two Ships During Meeting and Passing

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Koki Kitagawa ◽  
Masaaki Sano ◽  
Hironori Yasukawa
Keyword(s):  
Water Depth ◽  
Panel Method ◽  
Time Step ◽  
Interaction Forces ◽  
Motion Equations ◽  
Close Proximity ◽  
External Forces ◽  
Ship Speed

Motion equations of two ships maneuvering in close proximity are solved in consideration of the interaction between hulls. The interaction forces are calculated by a 3D panel method as a function of the ship position in the time step and considered as external forces in maneuvering. Four kinds of ships are prepared and the maneuvering motions are simulated with variation of the combination of ships, water depth, ship speed and draft. The effect of those parameters on the interaction forces and two ships behaviors are investigated. 

Computation of Ship-to-Ship Interaction Forces by a 3D Potential Flow Panel Method in Finite Water Depth

2010 ◽  
Author(s):  
Xueqian Zhou ◽  
Serge Sutulo ◽  
C. Guedes Soares
Keyword(s):  
Water Depth ◽  
Potential Flow ◽  
Hydrodynamic Interaction ◽  
Single Layer ◽  
Mirror Image ◽  
Present Contribution ◽  
Interaction Forces ◽  
Sea Bottom ◽  
Close Proximity ◽  
Finite Water Depth

The double-body 3D potential flow code developed earlier for computing hydrodynamic interaction forces and moments acting on the hulls of the ships sailing in close proximity with neighbouring ships or some other obstacles, is extended to the shallow water case. Two methods for accounting for the finite water depth were implemented: use of truncated mirror image series, and distribution of an additional single layer of sources on parts of the seabed beneath the moving hulls. While the first method does only apply to the flat horizontal seabed, the second one can also deal with the arbitrary bathymetry situations. As appropriate choice of the discretization parameters can significantly affect the accuracy and efficiency of the second method, the present contribution focuses on comparative computations aiming at defining reasonable dimensions of the moving panelled area on the sea bottom and maximum admissible size of the bottom panel. As result, conclusions concerning optimal parameters of the additional set of panels are drawn.

Computation of Ship-to-Ship Interaction Forces by a Three-Dimensional Potential-Flow Panel Method in Finite Water Depth

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Xueqian Zhou ◽  
Serge Sutulo ◽  
C. Guedes Soares
Keyword(s):  
Water Depth ◽  
Potential Flow ◽  
Three Dimensional ◽  
Single Layer ◽  
Mirror Image ◽  
Present Contribution ◽  
Interaction Forces ◽  
Sea Bottom ◽  
Close Proximity ◽  
Finite Water Depth

A double-body 3D potential-flow code developed earlier for computing hydrodynamic interaction forces and moments acting on the hulls of the ships sailing in close proximity with neighboring ships or some other obstacles, is extended to the shallow water case. Two methods for accounting for the finite water depth were implemented: (1) using truncated mirror image series and (2) distribution of an additional single layer of sources on parts of the seabed beneath the moving hulls. While the first method does only apply to the flat horizontal seabed, the second one can also deal with the arbitrary bathymetry situations. As appropriate choice of the discretization parameters can significantly affect the accuracy and efficiency of the second method, the present contribution focuses on comparative computations aiming at defining reasonable dimensions of the moving paneled area on the sea bottom and maximum admissible size of the bottom panel. As result, conclusions concerning optimal parameters of the additional set of panels are drawn.

Forced oscillation experiments

1991 ◽  
Vol 334 (1634) ◽  
pp. 199-211
Keyword(s):  
Numerical Methods ◽  
Water Depth ◽  
Forced Oscillation ◽  
Vertical Plane ◽  
Forced Oscillations ◽  
Hydrodynamic Characteristics ◽  
Scale Models ◽  
Ship Speed

Forced oscillation experiments with scale models are carried out to determine hydrodynamic characteristics of ships, with respect to motions in waves or steering and manoeuvring qualities. Depending on the considered motion components, in a horizontal or vertical plane, various methods are used to induce forced oscillations which are discussed briefly. Some results of forced oscillation experiments are presented as examples of this technique and compared with calculations based on numerical methods. The comparisons include, among others, the effects of ship speed and restricted water depth.

Automatic Control of Underway Replenishment Maneuvers in a Random Sea

1978 ◽  
Vol 22 (01) ◽  
pp. 20-28
Author(s):  
Reidar Alvestad
Keyword(s):  
Computer Simulation ◽  
Automatic Control ◽  
Collision Avoidance ◽  
Nonlinear Interaction ◽  
Interaction Forces ◽  
Random Seas ◽  
Close Proximity ◽  
Controller Performance ◽  
Hybrid Computer ◽  
Avoidance Problem

This paper describes a hybrid computer simulation of two ships performing replenishment operations in random seas. Such operations present collision hazards due to the nonlinear interaction forces and moments which result from close proximity maneuvering while underway. Maneuvers are simulated to demonstrate automatic controller performance during station-keeping, station-changing, and the approach and breakaway phases of typical underway replenishment (UNREP) operations. Results indicate that automatic control should be considered as a possible solution to the UNREP collision avoidance problem.

Evaluation of Ship-Bank and Ship-Ship Interaction Forces using a 3D Panel Method

2009 ◽  
Author(s):  
H Yasukawa ◽  
◽  
S Kawamura ◽  
S Tanaka ◽  
M Sano ◽  
...  
Keyword(s):  
Panel Method ◽  
Interaction Forces

Estimation of Fluctuating Propeller Torque of Full-Scale Ship Using Free-Running Model in Waves

2015 ◽  
Author(s):  
Michio Ueno ◽  
Yoshiaki Tsukada
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Full Scale ◽  
Engine Torque ◽  
Engine Model ◽  
Frequency Components ◽  
Free Running ◽  
External Forces ◽  
Ship Propeller ◽  
Ship Speed

The authors propose a method to estimate full-scale propeller torque consisting of low-frequency and high-frequency components in waves using measured data of free-running model ship. The duct fan auxiliary thruster (DFAT) [1] and the rudder-effectiveness and speed correction (RSC) [2,3] ensure similar model ship motion to full-scale in external forces, where RSC controls the model ship propeller rate of revolution and the auxiliary thrust depending on measured model ship speed. Analyzing a fluctuating component of effective inflow velocity to propeller due to waves, the method estimates full-scale fluctuating propeller torque in waves. This method also makes it possible to adopt into free-running model ship tests any engine model simulating interaction between propeller torque and engine torque. Trial application of the method exemplifies the property of full-scale fluctuating propeller torque comparing with that of model ship.

Hydrodynamic Interaction Forces on Ship Hulls Equipped With Propulsors

2012 ◽  
Author(s):  
Serge Sutulo ◽  
C. Guedes Soares
Keyword(s):  
Pressure Distribution ◽  
Hydrodynamic Interaction ◽  
Potential Interaction ◽  
Interaction Forces ◽  
Ship Hulls ◽  
Actuator Disk ◽  
Close Proximity ◽  
Body Potential ◽  
Yaw Moment ◽  
Accelerating Motion

Typically, study of hydrodynamic interaction between vessels navigating in close proximity to each other is limited to hydrodynamics of bare hulls. Meanwhile, ship propulsors, especially heavily loaded, which may happen in accelerating motion, can alter substantially the flow and distribution of pressure on the hulls which can be viewed as generalization of the thrust deduction phenomenon. The 3D doubled body potential interaction code based on the source panel method developed earlier by the authors has been enhanced to include the effect of a propeller on each of the interacting ships under the assumption that the propeller jets (slipstreams) are not involved into the interaction. Each propeller is simulated by a disk of sinks further approximated with a polygon composed of identical triangular panels with identical constant sink density linked to the thrust of the propulsor according to the actuator disk theory. Comparative computations were carried out for two identical tanker vessels in the close-proximity overtaking manoeuvre at various values of the loading coefficient of each propeller. The loading coefficient is not supposed to be necessarily defined by the steady propulsion point. Numerical results demonstrate that a heavily loaded propeller substantially modifies the pressure distribution on both hulls resulting in alteration of the hydrodynamic interaction loads, especially of the surge force and yaw moment.

Fundamental Study of Active Mass Damper for Improving Livability of Houses Against Traffic Vibration: Substantiation Test

2004 ◽  
Author(s):  
Osamu Hasegawa ◽  
Jyunji Okabe ◽  
Toyohiko Higashida ◽  
Yukito Matsumoto
Keyword(s):  
Complex Geometry ◽  
Vibration Level ◽  
Fundamental Study ◽  
Active Mass ◽  
Target Weight ◽  
Response Characteristics ◽  
Close Proximity ◽  
Mass Damper ◽  
Active Mass Damper ◽  
External Forces

In Japan, there are many houses built in limited space as well as in close proximity to causeways and railroads, due mainly to concentration of population in the cities in recent years. Slender structures and especially 3-story houses are susceptible to vibration induced by external forces such as traffic. This effect often creates an uncomfortable environment for habitation. Because houses often have a complex geometry, it is difficult to establish the vibration characteristics of a structure. Furthermore, the response characteristics of a house will change with environmental conditions. A prototype Active Mass Damper (AMD) has been developed to address some of these issues. This has been tested in an exhibition house in Tokyo. It uses two AMD’s of 1,725N mass each for both X-axis and Y-axis. Both AMD’s are applied in X and Y directions and are installed at RooF level, they are controlled by Direct Displacement Feedback (DDFB). The test showed that the AMD could dramatically reduce vibration. Of particular note was reduction about 6dB to 8dB (L10) in the first mode of vibration even though the house mass is double the prototype target weight. Also, vibration was dramatically decreased by the AMD on 3rd floor of the house. Vibration level and comfort are important criteria for this kind of system.

scholarly journals The fibronectin synergy site re-enforces cell adhesion and mediates a crosstalk between integrin classes

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Maria Benito-Jardón ◽  
Sarah Klapproth ◽  
Irene Gimeno-LLuch ◽  
Tobias Petzold ◽  
Mitasha Bharadwaj ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Thrombus Formation ◽  
Critical Role ◽  
Initial Contact ◽  
Αvβ3 Integrin ◽  
Rgd Motif ◽  
Cell Coverage ◽  
Vessel Injury ◽  
Close Proximity ◽  
External Forces

Fibronectin (FN), a major extracellular matrix component, enables integrin-mediated cell adhesion via binding of α5β1, αIIbβ3 and αv-class integrins to an RGD-motif. An additional linkage for α5 and αIIb is the synergy site located in close proximity to the RGD motif. We report that mice with a dysfunctional FN-synergy motif (Fn1syn/syn) suffer from surprisingly mild platelet adhesion and bleeding defects due to delayed thrombus formation after vessel injury. Additional loss of β3 integrins dramatically aggravates the bleedings and severely compromises smooth muscle cell coverage of the vasculature leading to embryonic lethality. Cell-based studies revealed that the synergy site is dispensable for the initial contact of α5β1 with the RGD, but essential to re-enforce the binding of α5β1/αIIbβ3 to FN. Our findings demonstrate a critical role for the FN synergy site when external forces exceed a certain threshold or when αvβ3 integrin levels decrease below a critical level.

Efficient simulation of flood events using machine learning

2020 ◽  
Author(s):  
Jihane Elyahyioui ◽  
Valentijn Pauwels ◽  
Edoardo Daly ◽  
Francois Petitjean ◽  
Mahesh Prakash
Keyword(s):  
Machine Learning ◽  
Water Depth ◽  
Input Data ◽  
Learning Model ◽  
Water Levels ◽  
Training Dataset ◽  
Time Step ◽  
Machine Learning Model ◽  
Maximum Water ◽  
Spatio Temporal

<p>Flooding is one of the most common and costly natural hazards at global scale. Flood models are important in supporting flood management. This is a computationally expensive process, due to the high nonlinearity of the equations involved and the complexity of the surface topography. New modelling approaches based on deep learning algorithms have recently emerged for multiple applications.</p><p>This study aims to investigate the capacity of machine learning to achieve spatio-temporal flood modelling. The combination of spatial and temporal input data to obtain dynamic results of water levels and flows from a machine learning model on multiple domains for applications in flood risk assessments has not been achieved yet. Here, we develop increasingly complex architectures aimed at interpreting the raw input data of precipitation and terrain to generate essential spatio-temporal variables (water level and velocity fields) and derived products (flood maps) by training these based on hydrodynamic simulations.</p><p>An extensive training dataset is generated by solving the 2D shallow water equations on simplified topographies using Lisflood-FP.</p><p>As a first task, the machine learning model is trained to reproduce the maximum water depth, using as inputs the precipitation time series and the topographic grid. The models combine the spatial and temporal information through a combination of 1D and 2D convolutional layers, pooling, merging and upscaling. Multiple variations of this generic architecture are trained to determine the best one(s). Overall, the trained models return good results regarding performance indices (mean squared error, mean absolute error and classification accuracy) but fail at predicting the maximum water depths with sufficient precision for practical applications.</p><p>A major limitation of this approach is the availability of training examples. As a second task, models will be trained to bring the state of the system (spatially distributed water depth and velocity) from one time step to the next, based on the same inputs as previously, generating the full solution equivalent to that of a hydrodynamic solver. The training database becomes much larger as each pair of consecutive time steps constitutes one training example.</p><p>Assuming that a reliable model can be built and trained, such methodology could be applied to build models that are faster and less computationally demanding than hydrodynamic models. Indeed, in with the synthetic cases shown here, the simulation times of the machine learning models (< seconds) are far shorter than those of the hydrodynamic model (a few minutes at least). These data-driven models could be used for interpolation and forecasting. The potential for extrapolation beyond the range of training datasets will also be investigated (different topography and high intensity precipitation events). </p>

Sign in / Sign up

Export Citation Format

Share Document