Impact Pressures on the Bottom of a Prismatic Planing Hull During Water Impact

2015 ◽  
Author(s):  
Carolyn Q. Judge ◽  
John A. Judge ◽  
Christine M. Ikeda
Keyword(s):  
Pressure Distribution ◽  
Structural Design ◽  
Structural Damage ◽  
High Speed ◽  
Empirical Method ◽  
Naval Academy ◽  
Water Impact ◽  
Empirical Estimates ◽  
Peak Pressures ◽  
The Impact

High-speed planing boats are subject to repeated slamming impacts, which can cause structural damage and discomfort or injury to passengers. The structural and seakeeping aspects of the design of high-speed craft are mainly determined through empirical estimates of mean and peak pressures. The primary structural guideline (Allen and Jones, 1978) relies heavily on semi-empirical criteria that are not always accurate and have limited application. The Allen and Jones guidelines provide conservative estimates leading to sufficient structural design, but do not provide enough guidance to allow strategic reduction in structural weight. Structural design depends on the hull bottom pressures while information about the magnitudes of peak pressures, time durations, and locations along the hull is generally not available. Model tests conducted at the US Naval Academy have measured bottom pressures on a prismatic planing hull geometry during operation in waves (both regular and irregular). Pressures were measured at point locations and using a two-dimensional pressure pad to examine how pressures change in both time and space during a water impact. Rosen (2005) presents a method for reconstructing the momentary pressure distribution during a hull-water impact. This method allows the measurements of a propagating pressure segment in one position of the hull at one instant in time to be associated with other positions at other instants in time (as determined from several different point pressure measurements). Morabito (2014) presents an empirical method for calculating the pressure distribution on the bottom of prismatic planing hulls. The method can be extended to the impact problem by use of an “equivalent” planing velocity. This paper compares the planing pressures predicted by Morabito's empirical method with the recreated pressure distribution determined from Rosen's method.

scholarly journals Is the Viscoelastic Sheet for Slamming Impact Ready to Be Used on Glass Fiber Reinforced Plastic Planning Hull?

2020 ◽  
Vol 10 (18) ◽  
pp. 6557 ◽  
Author(s):  
Patrick Townsend ◽  
Juan Carlos Suárez Bermejo ◽  
Paz Pinilla ◽  
Nadia Muñoz
Keyword(s):  
Structural Damage ◽  
High Speed ◽  
Damage Threshold ◽  
Fluorescent Light ◽  
Glass Fiber Reinforced Plastic ◽  
Additional Layer ◽  
Glass Fiber Reinforced ◽  
Weight Drop ◽  
Viscoelastic Layers ◽  
The Impact

Planing hull vessel built with polymer matrix laminates and fiberglass reinforcements (GFRP) suffer structural damage due to the phenomenon of slamming during navigation, due to the impact of the boat hull on the free surface of the water at high speed. A modification in the manufacture of the laminates for these fast boats is proposed, consisting of the insertion of an additional layer of a hybrid material, formed by elastomer encapsulated in an ABS polymer cell. Using GFRP specimens made from pre-impregnated material and reproducing the characteristic impacts of slamming, it is possible to compare the modified material with the introduction of the viscoelastic layers with the response under the same conditions as the unmodified laminates. Additionally, the panels have been tested using impacts due to weight drop at different energies, which allow determining the material damage threshold as a function of the energy absorbed, and to establish a comparison with the GFRP panels modified by observation in fluorescent light. It is verified that the proposal to reduce the effect of these impacts on the generation of damage to the material and its progression throughout the service life of the vessel is effective.

scholarly journals Sources of the Measurement Error of the Impact Pressure in Sloshing Experiments

2019 ◽  
Vol 7 (7) ◽  
pp. 207
Author(s):  
Dong Hwi Kim ◽  
Eun Soo Kim ◽  
Sung-chul Shin ◽  
Sun Hong Kwon
Keyword(s):  
Integrated Circuit ◽  
Measurement Errors ◽  
High Speed ◽  
Pressure Sensors ◽  
Pressure Measurements ◽  
Sensor Surface ◽  
Experimental Conditions ◽  
Surface Conditions ◽  
Peak Pressures ◽  
The Impact

Sloshing experiments have increasingly received academic attention. Understanding the measurement errors in the sloshing impact pressures is an important parts of the sloshing experiments since these errors, which arise from experimental conditions, affect the subsequent results. As part of the research on the sources of the measurement errors, focused on the effects of surface conditions of pressure sensors on the measurement of impact pressures. Thirty-six integrated circuit piezoelectric pressure sensors were placed on the upper surfaces of a two-dimensional tank to measure the sloshing impact pressures under surge or pitch motions. For each motion, the experimental conditions were divided in two based on whether the surfaces of the sensors were dry or wet. The peak pressures of each test were measured as twenty repeated experiments to ensure reliability. The flow in the tank was visualized using a high-speed camera to observe and analyze macroscopic and microscopic phenomena along the sensor surface. Thermal shock effects were confirmed by varying the experimental temperature and that of the sensor surface. The effects of the wet surface and droplets formed on the sensor surface on pressure measurements are discussed.

High-Speed Sealift Technology

1998 ◽  
Vol 35 (03) ◽  
pp. 135-150
Author(s):  
Colen Kennell ◽  
David R. Lavis ◽  
Michael T. Templeman
Keyword(s):  
High Speed ◽  
Empirical Method ◽  
Qualitative Assessment ◽  
Sea Transport ◽  
Relative Risks ◽  
Speed Range ◽  
Near Term ◽  
Design Characteristics ◽  
Impact Of Technology ◽  
The Impact

This paper describes a process that is currently being used within DoD and industry to examine the possibilities offered by technology to enhance the transport performance of high-speed commercial and military sealift. Technology projections are presented for both the near-term and the far-term. The impact of technology projections on transport performance properties is assessed both quantitatively and qualitatively. These assessments provide significant insight into the overall transport performance potential of hullforms and other technologies of interest, considerably in advance of detailed design studies. The quantitative assessment uses a derivation of the empirical method published by Kennell[1]4, which provides simple parametric relationships between mission requirements, expressed in terms of speed, range and payload, and design characteristics, expressed in terms of displacement, installed power and fuel weight, to compare the various hullforms and other technologies of interest. The qualitative assessment applies an established decision-making method to ascertain the relative capabilities and relative risks of hullforms and other technologies of interest for significant aspects of sea transport, other than speed, range and payload. While the methods used are generic, the data selected and results presented are aimed at ships capable of rapidly transporting heavy cargo over long distances.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Some aspects of rock cutting by high speed water jets

1966 ◽  
Vol 260 (1110) ◽  
pp. 295-310 ◽  
Keyword(s):  
Pressure Distribution ◽  
High Speed ◽  
Frictional Heating ◽  
Water Jet ◽  
Short Exposure ◽  
Maximum Pressure ◽  
Steam Turbines ◽  
Target Plate ◽  
Water Jets ◽  
The Impact

When rocks are cut in coal mines by steel picks, frictional heating sometimes causes ignition of methane; high speed water jets may provide a method of cutting which is free from this hazard. A high speed water jet emerging from a nozzle slows down with increasing distance from the nozzle and breaks up into water drops. Studies were made of the behaviour of water jets: in most of the experiments the jets were produced by pressures of 600 atm., but some results are given of experiments at pressures up to 5000 atm. The jets were examined by short exposure optical photography with several different methods of illumination (parallel transmitted, diffuse, and schlieren) and by X-ray photography. In order to find out how the jet velocity decays with distance from a nozzle, and to compare nozzle designs, a target plate containing a hole smaller than the jet diameter was placed so that the jet impinged at right angles on to it, and the target plate was moved until the maximum pressure at the hole was found: this was measured for different distances from the nozzle. Nozzle shapes suggested in literature for minimizing jet dispersion were studied and an empirical investigation of a variety of nozzle shapes was carried out. Several nozzle shapes were found which gave good results, i.e. the maximum pressure on the target plate was half the pump pressure at a distance of about 350 nozzle diameters. In many cutting applications the first stage in the process would be the impingement of a water jet on a surface at right angles. The initial cutting would depend upon the stress distribution within the target, which in turn would depend upon the pressure distribution produced by the water jet on the surface. A theory is given of the pressure distribution on the target plate, which predicts that the pressure will fall to zero at about 2.6 jet radii: this was found to be in good agreement with experiments. Preliminary studies were made of the penetration of several types of rock by water jets of velocities up to about 1000 m/s (pressures about 5000 atm). It was found that a 1 mm diameter jet drills a cylindrical hole about 5 mm in diameter. The pressure that the water jet produces at the bottom of such holes was measured and shown to fall off to about one-tenth of the nozzle pressure at a hole depth of about 4 cm.

The role of ‘splashing’ in the collapse of a laser-generated cavity near a rigid boundary

1999 ◽  
Vol 380 ◽  
pp. 339-361 ◽  
Author(s):  
R. P. TONG ◽  
W. P. SCHIFFERS ◽  
S. J. SHAW ◽  
J. R. BLAKE ◽  
D. C. EMMONY
Keyword(s):  
High Speed ◽  
Vital Role ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Liquid Jet ◽  
Rigid Boundary ◽  
Jet Impact ◽  
Pressure Peak ◽  
Peak Pressures ◽  
The Impact

Vapour cavities in liquid flows have long been associated with cavitation damage to nearby solid surfaces and it is thought that the final stage of collapse, when a high- speed liquid jet threads the cavity, plays a vital role in this process. The present study investigates this aspect of the motion of laser-generated cavities in a quiescent liquid when the distance (or stand-off) of the point of inception from a rigid boundary is between 0.8 and 1.2 times the maximum radius of the cavity. Numerical simulations using a boundary integral method with an incompressible liquid impact model provide a framework for the interpretation of the experimental results. It is observed that, within the given interval of the stand-off parameter, the peak pressures measured on the boundary at the first collapse of a cavity attain a local minimum, while at the same time there is an increase in the duration of the pressure pulse. This contrasts with a monotonic increase in the peak pressures as the stand-off is reduced, when the cavity inception point is outside the stated interval. This phenomenon is shown to be due to a splash effect which follows the impact of the liquid jet. Three cases are chosen to typify the splash interaction with the free surface of the collapsing cavity: (i) surface reconnection around the liquid jet; (ii) splash impact at the base of the liquid jet; (iii) thin film splash. Hydrodynamic pressures generated following splash impact are found to be much greater than those produced by the jet impact. The combination of splash impact and the emission of shock waves, together with the subsequent re-expansion, drives the flow around the toroidal cavity producing a distinctive double pressure peak.

Experimental and numerical study on hydrodynamic impact of a disk in pure and aerated water

2020 ◽  
pp. 147509022093370
Author(s):  
Yao Hong ◽  
Benlong Wang ◽  
Hua Liu
Keyword(s):  
Pressure Distribution ◽  
Void Fraction ◽  
High Speed ◽  
Numerical Study ◽  
Pure Water ◽  
Equation Model ◽  
Impact Loads ◽  
Temporal Pressure ◽  
Drop Tests ◽  
The Impact

The hydrodynamic loads of a disk impacting pure and aerated water are investigated experimentally and numerically. Experiments are performed on a rigid disk with different aeration levels and focus on the spatial and temporal pressure distribution. Drop tests are conducted by a specially designed apparatus to prevent the variation of velocity during the slamming period. A specially designed bubble generator, able to adjust the void fraction, is utilized to generate uniform and tiny bubbles. A high-speed camera is utilized to record the water spray and splash curtain. A homemade compressible multiphase solver based on the reduced five equation model is adopted to evaluate the impact loads, which assumes the water and bubbles sharing the same velocity and pressure. The results show that bubbles in the water have a significant influence on the impact loads. As the void fraction increases from zero to nearly 1%, the peak impact pressure is reduced considerably and the impact duration is becoming obviously longer. In aerated water impact, the disk has a more uniform pressure distribution on the surface. However, the pressure impulse in aerated impact tests is basically unchanged compared with that in pure water.

Safety evaluation of buildings under flood impact

2021 ◽  
Author(s):  
Youtong Rong ◽  
Paul Bates ◽  
Jeffrey Neal
Keyword(s):  
Structural Damage ◽  
High Speed ◽  
Flow Direction ◽  
Interaction Model ◽  
Dam Break ◽  
Maximum Pressure ◽  
Two Phase ◽  
Maximum Deformation ◽  
Flood Impact ◽  
The Impact

<p>The flood caused by a dam-break event generally contains a large amount of energy, and it can be destructive to the downstream buildings and structures. An experiment-validated three-dimensional numerical model was designed to investigate the impact of dam-break flood on structures with different arrangements. The Eulerian two-phase flow model and the smooth particle dynamics method are applied separately to solve the flow motion, and  the deformation characteristics of buildings under the flood impact are evaluated by fluid-structure interaction model. An experiment is constructed to validate the numerical simulation. The results show that the structure suffers a large instantaneous impact pressure when the flood water first contacts the structure, and the value of this pressure can reach 1.5-3.0 times that of the maximum pressure after the first impact, and the maximum total pressure of the upstream building surface is about 1800N. The deformation near the door and windows is obvious, and the maximum deformation can reach 600μm, which further results in the large deformation of the gable and roof on both sides. Moreover, the arrangement of buildings has different blocking effect on flood. The back-row buildings arranged in alignment along the flow direction still has to bear 20% flood impact, and the front row buildings arranged alternately bear 90% high-speed flow impact. The structural damage is evaluated by the material failure criterion, and the weak position of buildings is identified, providing an optimal design of buildings.</p>

Influence of the distribution of the shear walls on the seismic response of the buildings

2020 ◽  
Vol 15 (1) ◽  
pp. 37-44
Author(s):  
El Mehdi Echebba ◽  
Hasnae Boubel ◽  
Oumnia Elmrabet ◽  
Mohamed Rougui
Keyword(s):  
Structural Analysis ◽  
Seismic Response ◽  
Natural Frequency ◽  
Structural Design ◽  
Structural Response ◽  
Shear Walls ◽  
Structural Elements ◽  
Analysis Software ◽  
Ansys Apdl ◽  
The Impact

Abstract In this paper, an evaluation was tried for the impact of structural design on structural response. Several situations are foreseen as the possibilities of changing the distribution of the structural elements (sails, columns, etc.), the width of the structure and the number of floors indicates the adapted type of bracing for a given structure by referring only to its Geometric dimensions. This was done by studying the effect of the technical design of the building on the natural frequency of the structure with the study of the influence of the distribution of the structural elements on the seismic response of the building, taking into account of the requirements of the Moroccan earthquake regulations 2000/2011 and using the ANSYS APDL and Robot Structural Analysis software.

Modeling of Tread Block Contact Mechanics Using Linear Viscoelastic Theory3

2008 ◽  
Vol 36 (3) ◽  
pp. 211-226 ◽  
Author(s):  
F. Liu ◽  
M. P. F. Sutcliffe ◽  
W. R. Graham
Keyword(s):  
High Speed ◽  
Slip Rate ◽  
Material Model ◽  
Contact Forces ◽  
Block Modeling ◽  
Rate Dependent ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
The Impact ◽  
Good Agreement

Abstract In an effort to understand the dynamic hub forces on road vehicles, an advanced free-rolling tire-model is being developed in which the tread blocks and tire belt are modeled separately. This paper presents the interim results for the tread block modeling. The finite element code ABAQUS/Explicit is used to predict the contact forces on the tread blocks based on a linear viscoelastic material model. Special attention is paid to investigating the forces on the tread blocks during the impact and release motions. A pressure and slip-rate-dependent frictional law is applied in the analysis. A simplified numerical model is also proposed where the tread blocks are discretized into linear viscoelastic spring elements. The results from both models are validated via experiments in a high-speed rolling test rig and found to be in good agreement.

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