scholarly journals The Influence of the Ship's Speed and Distance to an Arbitrarily Shaped Bank on Bank Effects

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Evert Lataire ◽  
Marc Vantorre ◽  
Guillaume Delefortrie
Keyword(s):  
Return Flow ◽  
Asymmetric Flow ◽  
Dimensionless Velocity ◽  
Test Conditions ◽  
Close Proximity ◽  
Unique Model ◽  
Bank Effects ◽  
Yaw Moment ◽  
Sailing Ship ◽  
Restricted Waterways

In shallow and restricted waterways, the water displaced by a sailing ship is squeezed under and along its hull. These confinements result in increased velocities of the return flow along the hull and the induced pressure distribution on the hull causes a combination of forces and moments on the vessel. If generated because of asymmetric flow due to the presence of a bank, this combination of forces and moment is known as bank effects. A comprehensive experimental research program on bank effects has been carried out in the towing tank for maneuvers in shallow water (cooperation Flanders Hydraulics Research—Ghent University) at Flanders Hydraulics Research (FHR) in Antwerp, Belgium. The obtained data consist of more than 14,000 unique model test conditions. The relative position and distance between a ship and an arbitrarily shaped bank is ambiguous. Therefore, a definition for a dimensionless distance to the bank is introduced. In this way, the properties of a random cross section are taken into account without exaggerating the bathymetry at a distance far away from the ship or without underestimating the bank shape at close proximity to the ship. Also, a dimensionless velocity is introduced to take the influence of the water depth, forward speed, and blockage into account. The proposed mathematical model for bank effects, often described as a sway force and yaw moment, is instead decomposed in two sway forces at each perpendicular.

scholarly journals The Influence of the Ship’s Speed and Distance to an Arbitrarily Shaped Bank on Bank Effects

2015 ◽  
Author(s):  
Evert Lataire ◽  
Marc Vantorre ◽  
Guillaume Delefortrie
Keyword(s):  
Cross Section ◽  
Water Depth ◽  
Ship Motions ◽  
Return Flow ◽  
Asymmetric Flow ◽  
Data Set ◽  
Close Proximity ◽  
Unique Model ◽  
Bank Effects ◽  
Insight Into

A displacement vessel — obviously — displaces a (large) amount of water. In open and deep navigation areas this water can travel almost without any restriction underneath and along the ship’s hull. In restricted and shallow waterways, however, the displaced water is squeezed under and along the hull. These bathymetric restrictions result in increased velocities of the return flow along the hull. The resulting pressure distribution on the hull causes a combination of forces and moments on the vessel. If generated because of asymmetric flow due to the presence of a bank, this combination of forces and moment is known as bank effects. By far the most comprehensive and systematic experimental research program on bank effects has been carried out in the Towing Tank for Manoeuvres in Shallow Water (cooperation Flanders Hydraulics Research – Ghent University) at Flanders Hydraulics Research (FHR) in Antwerp, Belgium. The obtained data set on bank effects consists of more than 14 000 unique model test setups. Different ship models have been tested in a broad range of draft to water depth ratios, forward speeds and propeller actions. The tests were carried out along several bank geometries at different lateral positions between the ship and the installed bank. The output consists of forces and moments on hull, rudder and propeller as well as vertical ship motions. An analysis of this extensive database has led to an increased insight into the parameters which are relevant for bank effects. Two important parameters are linked to the relative distance between ship and bank and the ship’s forward speed. The relative position and distance between a ship and an arbitrarily shaped bank is ambiguous. Therefore a definition for a dimensionless distance to the bank will be introduced. In this way the properties of a random cross section are taken into account without exaggerating the bathymetry at a distance far away from the ship or without underestimating the bank shape at close proximity to the ship. The dimensionless velocity, named the Tuck number (Tu), considers the water depth and blockage, and is based on the velocity relative to the critical speed. The latter is dependent on the cross section (and thus the bank geometry) of the waterway.

scholarly journals Investigation into the Potential Migration of Nanoparticles from Laponite-Polymer Nanocomposites

Nanomaterials ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 723 ◽  
Author(s):  
Johannes Bott ◽  
Roland Franz
Keyword(s):  
Laser Light ◽  
Limit Of Detection ◽  
Surfactant Solution ◽  
Ethylene Vinyl Acetate ◽  
Field Flow Fractionation ◽  
Migration Test ◽  
Asymmetric Flow ◽  
Worst Case ◽  
Test Conditions ◽  
Migration Potential

In this study, the migration potential of laponite, a small synthetic nanoclay, from nanocomposites into foods was investigated. First, a laponite/ethylene vinyl acetate (EVA) masterbatch was compounded several times and then extruded into thin low-density polyethylene (LDPE) based films. This way, intercalation and partial exfoliation of the smallest type of clay was achieved. Migration of laponite was investigated using Asymmetric Flow Field-Flow Fractionation (AF4) with Multi-Angle Laser Light Scattering (MALLS) detection. A surfactant solution in which laponite dispersion remained stable during migration test conditions was used as alternative food simulant. Sample films with different loadings of laponite were stored for 10 days at 60 °C. No migration of laponite was found at a limit of detection of 22 µg laponite per Kg food. It can be concluded that laponite (representing the worst case for any larger structured type of clay) does not migrate into food once it is incorporated into a polymer matrix.

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.

VERTICAL AND SLOPED BANK EFFECTS ON DIFFERENT SHIP TYPES

2021 ◽  
Vol 157 (A3) ◽  
Author(s):  
Dong-Taur Su
Keyword(s):  
Current Flow ◽  
Center Of Mass ◽  
Computer Design ◽  
Hydrodynamic Analysis ◽  
Safe Navigation ◽  
Study Results ◽  
Bank Effects ◽  
Design Software ◽  
Asymmetric Flows ◽  
Yaw Moment

This study employed computer design software to completely draft 3D ship models; then, computational fluid dynamics were used to establish numeric navigation channels and simulate fluid hydrodynamic analysis of ships navigating along shore banks. The parameters considered comprised bank type (vertical and sloped), ship model (two types), velocity, ship-to-bank distance, and navigation time. Figures and tables were used to present the distribution of ship stern eddy current, flow field pressure, and velocity, and the comparison of center of mass deviation, sway force, and yaw moment. Results showed that ships navigating along embankments and channels produced asymmetric flows, which draw the bow away from the shore. Larger ships are substantially more influenced by bank effects than smaller ships. Large sway forces and yaw moments are produced in large ships, drifting the bow away from the bank and the stern towards the bank, increasing the risk of collision with the embankment. From the study results, the characteristics of bank effects are understood and can be used for assisting the safe navigation of ships in restricted waters.

On the Prediction of Hydrodynamic Forces Acting on a Ship Moving at Constant Drift

2006 ◽  
Author(s):  
N. Sulficker Ali ◽  
G. Dhinesh ◽  
K. Murali ◽  
V. Anantha Subramanian
Keyword(s):  
Fluid Dynamics ◽  
Computational Study ◽  
Flow Characteristics ◽  
Lateral Force ◽  
Asymmetric Flow ◽  
Mean Velocity ◽  
Drift Angle ◽  
Towing Tank ◽  
Computational Fluid Dynamics Cfd ◽  
Yaw Moment

The effect of drift angle on a ship is investigated through towing tank tests and using Computational Fluid Dynamics (CFD). Resistance and wave elevations obtained from the computational study are validated with experimental results. Detailed free surface, mean velocity and pressure flow fields on the hull surface are obtained from the computational study for Fn ranging from 0.16 to 0.22 and for drift angle β = 0, 5 and 10°. The lateral force, yaw moment and asymmetric flow characteristics are brought out in the computational study.

Numerical Prediction of Ship Hydrodynamic Derivatives in Close Proximity to a Vertical Bank and Maneuvering Stability Analysis

2016 ◽  
Author(s):  
Han Liu ◽  
Ning Ma ◽  
Xiechong Gu
Keyword(s):  
Lateral Force ◽  
Ship Maneuvering ◽  
Directional Stability ◽  
Bank Effect ◽  
Hydrodynamic Derivatives ◽  
Captive Model Tests ◽  
Close Proximity ◽  
Derivatives Of ◽  
Yaw Moment ◽  
Water Depths

As bank effect has a remarkable influence on the maneuverability of a ship proceeding close to a vertical bank, the assessment of ship maneuvering stability is of great importance. The hydrodynamic derivatives of a ship can reflect the change of the ship’s maneuverability and they are determined with the method of planar motion mechanism (PMM) tests. This paper presents a numerical way to simulate the PMM captive model tests for the ship KVLCC2. A general purpose viscous flow solver was adopted to solve unsteady Reynolds averaged Navier Stokes (RANS) equations in conjunction with a RNG k-ε turbulence model. A hybrid dynamic mesh technique is developed to update the mesh volume around the ship hull when the ship is undertaking pure yaw motions and it turns out efficient and effective to solve the limitation of small ship-bank distance to the mesh configuration and remeshing.. The numerical simulations and the accuracy of the numerical method was validated in comparison with the results of PMM tests in a circulating water channel. Then a series of distances between ship and bank together with different water depths were set for simulating the PMM tests of the KVLCC2 model in proximity to a vertical bank. The first order hydrodynamic derivatives of the ship were analyzed from the time history of lateral force and yaw moment according to the multiple-run simulating procedure. The values of derivatives in different lateral proximities to the bank and variant water depths were compared and it showed some favorable trends for predicting the ship’s maneuverability in the restricted waterways. For example, the influence of velocity derivatives on lateral force reduces while that of velocity derivatives on yaw moment strengthens and this is partly due to the suction force and bow-out moment caused by bank wall effect. The straight line stability and directional stability in terms of the calculated hydrodynamic derivatives were also discussed based on the MMG model for ship maneuvering. Results indicate that the ship is inherently unstable without control and the enhancement of bank effect makes the condition even worse. Moreover, a stable or unstable zone of PD controller parameters focusing on the directional stability was illustrated and setting the values of controller parameters in the range of “Control with high sensitivity” is recommended for cases of the ship navigating in very close proximity to a bank.

Vertical and Sloped Bank Effects on Different Ship Types

2015 ◽  
Vol 157 (A3) ◽  
pp. 189-204
Keyword(s):  
Current Flow ◽  
Center Of Mass ◽  
Computer Design ◽  
Hydrodynamic Analysis ◽  
Safe Navigation ◽  
Study Results ◽  
Bank Effects ◽  
Design Software ◽  
Asymmetric Flows ◽  
Yaw Moment

"This study employed computer design software to completely draft 3D ship models; then, computational fluid dynamics were used to establish numeric navigation channels and simulate fluid hydrodynamic analysis of ships navigating along shore banks. The parameters considered comprised bank type (vertical and sloped), ship model (two types), velocity, ship-to-bank distance, and navigation time. Figures and tables were used to present the distribution of ship stern eddy current, flow field pressure, and velocity, and the comparison of center of mass deviation, sway force, and yaw moment. Results showed that ships navigating along embankments and channels produced asymmetric flows, which draw the bow away from the shore. Larger ships are substantially more influenced by bank effects than smaller ships. Large sway forces and yaw moments are produced in large ships, drifting the bow away from the bank and the stern towards the bank, increasing the risk of collision with the embankment. From the study results, the characteristics of bank effects are understood and can be used for assisting the safe navigation of ships in restricted waters."

Effect of Nose Tip on Wing Rock of Slender Delta Wing

2012 ◽  
Vol 232 ◽  
pp. 178-183
Author(s):  
Saifur Rahman Bakaul ◽  
Yan Kui Wang ◽  
Guang Xing Wu ◽  
Qureshi Humayun
Keyword(s):  
Force Measurement ◽  
Delta Wing ◽  
Close Relation ◽  
Asymmetric Flow ◽  
Delta Wings ◽  
Root Cause ◽  
Wing Rock ◽  
Close Proximity ◽  
Back Angle ◽  
Wing Tip

The root cause of wing rock is investigated by examining two slender delta wings (700 and 850 sweep back angle) in wind tunnel using force measurement, pressure measurement and PIV techniques. The results show presence of asymmetric flow at 200 angle of attack and initiation of wing rock at the same point for 850 model while there is neither asymmetric flow nor wing rock for 700 model suggesting close relation of flow asymmetry with wing rock. Investigation with three apparently identical nose sections reveals that the asymmetry comes from the area very close to the wing tip. This asymmetric flow causes the vortices to interact in a complex way resulting in wing rock when the vortices are in close proximity (such as for 850 model), which is not the case when the vortices are ‘comparatively away’ (such as 700 model) from each other.

HYDRODYNAMIC INTERACTION BETWEEN SHIPS AND RESTRICTED WATERWAYS

2021 ◽  
Vol 159 (A1) ◽  
Author(s):  
E Lataire ◽  
M Vantorre
Keyword(s):  
Pressure Drop ◽  
Hydrodynamic Interaction ◽  
Model Tests ◽  
Extensive Literature ◽  
Literature Study ◽  
Data Set ◽  
Bank Effects ◽  
Robust Formulation ◽  
The Mathematical Model ◽  
Restricted Waterways

In open and unrestricted waters the water displaced by a forward sailing vessel can travel without major obstruction underneath and along the ship. In restricted and shallow sailing conditions, the displaced water is squeezed between the hull and the bottom and/or the bank. This results in higher flow velocities and as a consequence a pressure drop around the same hull. In the vicinity of a bank this pressure drop generates a combination of forces and moments on the vessel, known as bank effects. The major achievement of the presented research is the development of a realistic and robust formulation for these bank effects. This knowledge is acquired with an extensive literature study on one hand and with dedicated model tests carried out in different towing tanks on the other. The majority of the utilised model tests were carried out in the shallow water towing tank at Flanders Hydraulics Research in Antwerp, Belgium. The data set on bank effects consists of more than 8 000 unique model test setups (which is by far the most elaborate research ever carried out on this subject). These model tests provide the input for the analysis of bank effects and the creation of the mathematical model.

Effects of Vincristine on Endothelial Microtubules in the Spinal Cord

1976 ◽  
Vol 34 ◽  
pp. 58-59
Author(s):  
John L. Beggs ◽  
John D. Waggener ◽  
Wanda Miller
Keyword(s):  
Spinal Cord ◽  
Biological Activity ◽  
Horseradish Peroxidase ◽  
Transport Mechanism ◽  
Vasogenic Edema ◽  
Vesicular Transport ◽  
Close Proximity

Microtubules (MT) are versatile organelles participating in a wide variety of biological activity. MT involvement in the movement and transport of cytoplasmic components has been well documented. In the course of our study on trauma-induced vasogenic edema in the spinal cord we have concluded that endothelial vesicles contribute to the edema process. Using horseradish peroxidase as a vascular tracer, labeled endothelial vesicles were present in all situations expected if a vesicular transport mechanism was in operation. Frequently,labeled vesicles coalesced to form channels that appeared to traverse the endothelium. The presence of MT in close proximity to labeled vesicles sugg ested that MT may play a role in vesicular activity.

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