Slam induced loads on a 3D bow with various pitch angles

2019 ◽  
pp. 1-18 ◽  
Author(s):  
Yiwen Wang ◽  
Weiguo Wu ◽  
Shan Wang ◽  
Carlos Guedes Soares
Keyword(s):  
Impact Velocity ◽  
Pitch Angle ◽  
Water Entry ◽  
Model Tests ◽  
Experimental Measurements ◽  
Pressure Distributions ◽  
Slamming Load

Abstract A 3D water entry of a typical bow model of River-to-Sea ship is studied experimentally. A large number of systematic experiments have been performed for the bow model with different pitch angles. Considering various pitch angles and impact velocities in the model tests, the slamming pressure distributions on the bottom of the bow are presented and discussed. The measured slamming pressures on the bow are identified in terms of the maximum slamming coefficient. The effects of the pitch angle and impact velocity on slamming pressure are discussed as well, based on the experimental measurements. It is shown that the slamming load on the bottom of the model increases as the pitch angle decreases in most cases. With a higher impact velocity, the coefficient of the maximum slamming pressure is smaller for most of the tested cases.

Slam Induced Loads on a 3D Bow With Various Pitch Angles

2016 ◽  
Author(s):  
Yiwen Wang ◽  
Weiguo Wu ◽  
C. Guedes Soares
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Impact Velocity ◽  
Pitch Angle ◽  
Water Entry ◽  
Experimental Measurements ◽  
Numerical Predictions ◽  
Element Method

A 3D water entry of a typical bow model of sea-river link ship is studied using both experimental measurements and numerical predictions. A large number of systematic experiments have been performed with different pitch angles. The slamming process is simulated through finite element method with LS-DYNA. The distribution and magnitude of slam induced loads is determined from experiments and is calculated. The effect of the pitch angle and impact velocity is discussed based on the comparison between the predicted results and the experiments values.

scholarly journals Water entry of an expanding wedge/plate with flow detachment

2016 ◽  
Vol 797 ◽  
pp. 322-344 ◽  
Author(s):  
Yuriy A. Semenov ◽  
Guo Xiong Wu
Keyword(s):  
Free Surface ◽  
General Solution ◽  
Water Entry ◽  
Hodograph Method ◽  
Fixed Length ◽  
Pressure Distributions ◽  
Initial Stage ◽  
Special Cases ◽  
Wedge Plate ◽  
Special Case

A general similarity solution for water-entry problems of a wedge with its inner angle fixed and its sides in expansion is obtained with flow detachment, in which the speed of expansion is a free parameter. The known solutions for a wedge of a fixed length at the initial stage of water entry without flow detachment and at the final stage corresponding to Helmholtz flow are obtained as two special cases, at some finite and zero expansion speeds, respectively. An expanding horizontal plate impacting a flat free surface is considered as the special case of the general solution for a wedge inner angle equal to ${\rm\pi}$. An initial impulse solution for a plate of a fixed length is obtained as the special case of the present formulation. The general solution is obtained in the form of integral equations using the integral hodograph method. The results are presented in terms of free-surface shapes, streamlines and pressure distributions.

Water Entry of a Wedge by Hydroelastic Orthotropic Plate Theory

1999 ◽  
Vol 43 (03) ◽  
pp. 180-193 ◽  
Author(s):  
Odd M. Faltinsen
Keyword(s):  
Impact Velocity ◽  
Cross Sections ◽  
Orthotropic Plate ◽  
Plate Theory ◽  
Three Dimensional ◽  
Water Entry ◽  
Natural Period ◽  
Cross Sectional ◽  
Flow Effects ◽  
The Impact

Water entry of a hull with wedge-shaped cross sections is analyzed. The stiffened platings between two transverse girders on each side of the keel are separately modeled. Orthotropic plate theory is used. The effect of structural vibrations on the fluid flow is incorporated by solving the two-dimensional Laplace equation in the cross-sectional fluid domain by a generalized Wagner's theory. The coupling with the plate theory provides three-dimensional flow effects. The theory is validated by comparison with full-scale experiments and drop tests. The importance of global ship accelerations is pointed out. Hydrodynamic and structural error sources are discussed. Systematic studies on the importance of hydroelasticity as a function of deadrise angle and impact velocity are presented. This can be related to the ratio between the wetting time of the structure and the greatest wet natural period of the stiffened plating. This ratio is proportional to the deadrise angle and inversely proportional to the impact velocity. A small ratio-means that hydroelasticity is important and a large ratio means that hydroelasticity is not important.

Simulation on Performances of Vertical Axis Wind Turbine

2010 ◽  
Author(s):  
Chien-Chang Chen ◽  
Cheng-Hsiung Kuo
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Vertical Axis ◽  
Flow Structures ◽  
Vertical Axis Wind Turbine ◽  
Ansys Fluent ◽  
Moment Coefficient ◽  
Pressure Distributions ◽  
The Moment ◽  
Starting Torque

This study employs the commercialized computational fluid dynamics software (Ansys/Fluent), with the user’s defined technique, to simulate the unsteady flow structures around the small-size vertical axis wind turbines (VAWT) with three straight blades. This study addresses the effects of the collective variations of the pitch angle (within ± 10°) on the performance of the VAWT system. The results of the transient (acceleration) stage will be employed to evaluate the self-starting ability. While the vertical axis wind turbine (VAWT) reaches a steady rotating stage, the detailed flow structures, the vorticity fields, the pressure distributions around, and the forces on the airfoils at various azimuthal positions will be addressed. For the blades with a negative pitch angle (θ = −10°), has the peak value of the moment coefficient within one revolution is the largest which will provide the largest starting torque to drive the VAWT system more easily. However, in this case, the moment coefficients are negative within some part of the period. This cancels part of the positive moment within one revolution, thus the efficiency is reduced at this pitch angle. For the case with positive pitch angle (θ = 10°), the area under the moment coefficient curve is the smallest and the time elapse of large moment coefficient is relatively short. Thus the efficiency and the starting torque are the lowest among thee pitch angles.

scholarly journals Parametric Study on the Free-Fall Water Entry of a Sphere by Using the RANS Method

2019 ◽  
Vol 7 (5) ◽  
pp. 122
Author(s):  
Pengyao Yu ◽  
Cong Shen ◽  
Chunbo Zhen ◽  
Haoyun Tang ◽  
Tianlin Wang
Keyword(s):  
Impact Velocity ◽  
Impact Force ◽  
Free Fall ◽  
Water Entry ◽  
Time Step ◽  
Measuring Device ◽  
Mesh Density ◽  
The Impact ◽  
Peak Value ◽  
Rans Method

Motivated by the application of water-entry problems in the air-drop deployment of a spherical oceanographic measuring device, the free-fall water entry of a sphere was numerically investigated by using the transient Reynolds-averaged Navier–Stokes (RANS) method. A convergence study was carried out, which accounts for the mesh density and time-step independence. The present model was validated by the comparison of non-dimensional impact force with previous experimental and numerical results. Effects of parameters, such as impact velocity, radius, and mass of the sphere on the impact force and the acceleration of the sphere, are discussed. It is found that the peak value of the non-dimensional impact force is independent of the impact velocity and the radius of the sphere, while it depends on the mass of the sphere. By fitting the relationship between the peak value of the non-dimensional impact force and the non-dimensional mass, simplified formulas for the prediction of peak values of the impact force and the acceleration were achieved, which will be useful in the design of the spherical oceanographic measuring device.

Evolution of slamming load and flow field in water-entry process of trimaran ship section

2020 ◽  
Vol 205 ◽  
pp. 107319 ◽  
Author(s):  
Zhi Zong ◽  
Yifang Sun ◽  
Yichen Jiang ◽  
Tiezhi Sun ◽  
Yiquan Yu
Keyword(s):  
Flow Field ◽  
Water Entry ◽  
Slamming Load

Experimental study on oblique water entry of projectiles

2016 ◽  
Vol 30 (28) ◽  
pp. 1650348 ◽  
Author(s):  
Chenggong Zhao ◽  
Cong Wang ◽  
Yingjie Wei ◽  
Xiaoshi Zhang ◽  
Tiezhi Sun
Keyword(s):  
Experimental Study ◽  
Impact Velocity ◽  
High Speed ◽  
Transition Point ◽  
Water Entry ◽  
High Speed Photography ◽  
Initial Water ◽  
Before And After ◽  
Velocity Attenuation ◽  
Cavity Evolution

An experimental study of oblique water entry of projectiles with different noses has been conducted using high-speed photography technology. The images of the initial water entry impact, cavity evolution, and the closure and shedding of vortices of cavity are presented in the paper. The results reveal that for high-speed oblique water entry (the initial impact velocity [Formula: see text][Formula: see text]50 m/s), the cavity attached to the projectile is symmetrical and free from the influence of gravity. The shedding of the water–vapor–air mixture in the tail of the cavity produces vortices which disappear in the rear of the projectile trajectory. Particular attention is given to the velocity attenuation of the projectile after water entry. The results show that there is a transition point at the time corresponding to the surface seal of the cavity during the velocity attenuation after oblique water entry, and the rates of velocity attenuation are different before and after this transition point. Additionally, the chronophotography of the cavity evolution shows that the time when the surface seal of the cavity occurs decreases with the increase of the initial impact velocity of the projectile.

scholarly journals Numerical Investigation of Water Entry Problem of Pounders with Different Geometric Shapes and Drop Heights for Dynamic Compaction of the Seabed

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-18
Author(s):  
Mohammad Hossein Taghizadeh Valdi ◽  
Mohammad Reza Atrechian ◽  
Ata Jafary Shalkoohy ◽  
Elham Chavoshi
Keyword(s):  
Impact Velocity ◽  
Three Dimensional ◽  
Water Entry ◽  
Drop Height ◽  
Fluid Structure Interactions ◽  
Critical Height ◽  
Geometric Shapes ◽  
Model Fluid ◽  
Explicit Dynamic ◽  
Off Time

The water entry problem of three-dimensional pounders with different geometric shapes of cube, cylinder, sphere, pyramid, and cone was numerically simulated by the commercial software Abaqus, and the effects of pounder shape and drop height from the free surface of water on deepwater displacement and velocity as well as pinch-off time and depth were investigated. An explicit dynamic analysis method was employed to model fluid-structure interactions using a Coupled Eulerian-Lagrangian (CEL) formulation. The simulation results are verified by showing the computed shape of the air cavity, displacement of sphere, pinch-off time, and depth which all agreed with the experimental results. The results reveal that the drag force of water has the highest and lowest effect on cubical and conical pounders, respectively. Increasing the pounder drop height up to the critical height leads to increased pounder velocity while impacting the model bed and more than the critical drop height has a reverse effect on pounder impact velocity. Pinch-off time is a very weak function of pounder impact velocity; but pinch-off depth increases linearly with increased impact velocity.

scholarly journals Flow Field Analysis and Performance Assessment Inside a Vanned Diffuser of a Laboratory-Type Centrifugal Pump

1970 ◽  
Vol 3 (1) ◽  
pp. 8-15
Author(s):  
Abdelmadjid Atif ◽  
Sara Sami
Keyword(s):  
Numerical Simulation ◽  
Performance Assessment ◽  
Centrifugal Pump ◽  
Design Flow ◽  
Field Analysis ◽  
Experimental Measurements ◽  
Vaned Diffuser ◽  
Pressure Distributions ◽  
Flow Field Analysis ◽  
And Performance

The paper refers to the analysis of flow fields inside a vaned diffuser and performance assessment of a laboratory-type centrifugal pump operating with air. The study deals with numerical simulation of the flow at design flow rate, with focus on velocity and pressure distributions across a diffuser passage. The aim is to highlight the flow structure how it leaves the impeller and evolves through the diffuser to understand the mechanism of pressure recovery. The performance assessment consists of evaluating diffuser effectiveness. The numerical results are compared to experimental measurements for validation.

Sign in / Sign up

Export Citation Format

Share Document