A Simplified Method of Water Impact on Elastic Plate in Early Stage

2016 ◽  
Author(s):  
Hua Sun ◽  
Deyu Wang
Keyword(s):  
Elastic Plate ◽  
Early Stage ◽  
Impact Loads ◽  
Arbitrary Lagrangian Eulerian ◽  
Water Impact ◽  
Flat Bottom ◽  
Initial Stage ◽  
Simplified Method ◽  
Bottom Structures ◽  
The Impact

For most flat-bottom marine structures, the impact loads are generated by complex transient coupling effects of solid, air and water. However, there are rare simplified forecasting methods to obtain the impact loads and dynamic response of the flat-bottom structures by considering both hydro elastic and air cushion effects. In the paper, a new simplified analysis method of water impact on the elastic plate is proposed referred to Verhagen’s model of the rigid plate. The analysis is focused on the initial stage during which the highest hydrodynamic loads are generated. The method simulates the interaction between the plate, the air and the water. Also, fluid-structure coupling results from the simplified method are compared to numerical results from Arbitrary Lagrangian–Eulerian method and experimental results to validate the feasibility and accuracy of this simplified method.

scholarly journals Experimental evaluation of the air trapped during the water entry of flexible structures

ACTA IMEKO ◽  
2014 ◽  
Vol 3 (3) ◽  
pp. 63 ◽  
Author(s):  
Riccardo Panciroli ◽  
Giangiacomo Minak
Keyword(s):  
Flexible Structures ◽  
Processing Technique ◽  
Water Entry ◽  
Structural Deformation ◽  
Air Trapping ◽  
Flat Bottom ◽  
Initial Stage ◽  
Entry Velocity ◽  
Bottom Structures ◽  
The Impact

Deformable structures entering the water might experience several fluid-structure interaction (FSI) phenomena; air trapping is one of these. According to its definition, it consists of air bubbles trapped between the structure and the fluid during the initial stage of the impact. These bubbles might reduce the peak impact force. This phenomenon is characteristic for the water entry of flat-bottom structures. Above a deadrise angle of 10°, air trapping is negligible. In this work, we propose a methodology to evaluate the amount of air trapped in the fluid during the water entry. Experiments are performed on wedges with varying stiffness, entry velocity, and deadrise angle. A digital image post- processing technique is developed and utilized to track the air trapping mechanism and its evolution in time. Interesting results are found on the effect of the impact velocity and the structural deformation on the amount of air trapped during the slamming event.

Performance of healthy elderly with Alzheimer's disease at an early stage in executive function and language

2011 ◽  
Vol 26 (S2) ◽  
pp. 498-498
Author(s):  
M.T. Santos ◽  
G.C. Couto ◽  
J.C. Achieri ◽  
C.A. Júnior
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Early Stage ◽  
The Elderly ◽  
Screening Tests ◽  
Healthy Elderly ◽  
Initial Stage ◽  
Significant Difference ◽  
Common Causes ◽  
The Impact

Dementia are increasingly prevalent in population. The most common causes of dementia is Alzheimer's disease (AD). Screening tests have been used for the premature diagnosis of Alzheimer Disease (AD), specifically in the executive functions and language, which are compromised at an initial stage. However, the necessity standardized means and validated for our middle, to show oneself a pressing subject.ObjectiveTo analyze the impact of the length of sentences in the abstraction of proverbs in the Screening Test for Alzheimer's disease with Proverbs (TRDAP), healthy elderly and with Alzheimer's disease at early stage.MethodSurvey document in the database, analyzing the responses of the elderly (abstract or concrete interpretation of proverbs), relating the length of sentences (sayings) of stage B of TRDAP with the diagnosis of Alzheimer's disease and the interference of age and schooling.ResultsHealthy older people showed greater capacity for abstraction than those with AD. There was Significant differences, in the sayings 1 (p = 0.033) and 2 (p = 0.001), corresponding to lower sentences, which did not occur with the proverb 3. As for age no verified significant difference among the healthy and only saying 3 in AD patients, however schooling differenced the healthy.ConclusionElderly with Alzheimer's disease at an initial stage have lower performance in the comprehension of ambiguous sentences, interpretation and abstraction of proverbs, corroborating with the data of the literature. The size of these sentences appears to be inversely proportional to the correctness of interpretation in elderly patients with and without AD.

Numerical Analysis of Impact Loads on Subsea Structures During Water Entry in Presence of Waves

2020 ◽  
Author(s):  
Gustavo Garcia Momm ◽  
Ivan Fábio Mota de Menezes
Keyword(s):  
Constant Velocity ◽  
Oil And Gas ◽  
Free Fall ◽  
Water Entry ◽  
Gas Production ◽  
Rigid Bodies ◽  
Bottom Surface ◽  
Impact Loads ◽  
Flat Bottom ◽  
The Impact

Abstract Subsea structures employed on offshore oil and gas production systems are likely to be subject to severe loads during deployment. Lowering these structures through the wave zone is a critical operation and the prediction of the loads associated is complex as it involves accelerations of these bodies induced by the vessel motion and the sea surface displacements. This work presents a numerical approach to assessment of the effect of waves on the impact loads that subsea structures are subject to during water entry. A 2D one degree of freedom model using the SPH method was developed to estimate slamming loads on rigid bodies during water entry considering both calm and wavy surfaces. Initially the model was employed to simulate the water entry of wedge considering both free fall and constant velocity cases, obtaining loads profile similar to experiments and numerical simulations from the literature. Later, the constant velocity model was configured to a flat bottom surface rigid body in order to represent a subsea manifold. A regular waves generator provided different wavelength, height and phase enabling slamming load assessment in various situations.

scholarly journals Comparison between numerical analysis and the levitation mass method measurement test of a spherical structure early impacting water

2018 ◽  
Vol 10 (1) ◽  
pp. 168781401774807 ◽  
Author(s):  
Yonghu Wang ◽  
Dongwei Shu ◽  
Yusaku Fujii ◽  
Akihiro Takita ◽  
Tsuneaki Ishima ◽  
...  
Keyword(s):  
Finite Element ◽  
Contact Stiffness ◽  
Experimental Results ◽  
Impact Loads ◽  
Arbitrary Lagrangian Eulerian ◽  
Water Impact ◽  
Step Size ◽  
Time Step ◽  
Time Step Size ◽  
Spherical Structure

In order to precisely measure water impact loads of a spherical structure vertically dropping onto a calm water surface, a new validity check of the analysis using the levitation mass method experiment is proposed. The main feature of levitation mass method experiment is to obtain a better estimation of early water impact loads through the application of Doppler effect. Experimental results of different heights are verified based on the Assessment Index and are in comparison with the classical experimental data for validation purpose. It shows that the levitation mass method measurement is useful and effective to obtain the water impact loads for the crashworthiness analysis. Besides, early water impact hydrodynamic behaviors are simulated based on the nonlinear explicit finite element method, together with application of a multi-material arbitrary Lagrangian–Eulerian solver. A penalty coupling algorithm is utilized to realize fluid–structure interaction between the spherical body and fluids. Convergence studies are performed to construct the proper finite element model by the comparison with experimental results, where mesh sensitivity, contact stiffness, and time-step size parametric studies are thoroughly investigated. The comparisons between experimental and numerical results show good consistency by the prediction of the water impact coefficients on the structure.

Hydrodynamic Theories of Ship Slamming Review and Extension

1961 ◽  
Vol 5 (01) ◽  
pp. 9-21 ◽  
Author(s):  
Wen-Hwa Chu ◽  
H. Norman Abramson
Keyword(s):  
Experimental Data ◽  
Surface Boundary ◽  
Ellipse Fitting ◽  
Water Impact ◽  
Ship Slamming ◽  
Free Surface Boundary Condition ◽  
Initial Stage ◽  
Surface Boundary Condition ◽  
The Impact ◽  
Compressibility Effects

A critical review and evaluation of existing hydrodynamic theories of body-water impact is presented. It is shown, partly by comparison with available experimental data, that fitting methods are adequate only for bodies of reasonably large deadrise angle during later stages of the impact process. The ellipse-fitting technique is extended to a much broader class of body forms and more accurate formulations of the general problem are proposed that avoid linearization of the free-surface boundary condition and can account for compressibility effects during the initial stage of impact, although numerical procedures must be employed.

A Simple Numerical Method for Evaluation of Water Impact Loads on Decks of Large-Volume Offshore Platforms

2005 ◽  
Author(s):  
Rolf Baarholm
Keyword(s):  
Diffraction Analysis ◽  
Large Volume ◽  
Transfer Functions ◽  
Added Mass ◽  
Second Order ◽  
Suggested Method ◽  
Impact Loads ◽  
Water Impact ◽  
Simple Method ◽  
The Impact

A simple method for solving water impact loads underneath decks of offshore structures is developed. In the present paper the emphasis is on the vertical loads, but in principle the suggested method can also be applied to horizontal loading. The suggested method is three-dimensional and valid for general deck geometries and arbitrary incoming wave direction. First and second order wave amplification due to the large-volume structure is included in the analysis. An important feature of the present approach is that added mass of the instantaneous wetted deck area is approximated by the added mass of thin rectangular or elliptical plates. A numerical tool for solving the impact loads is implemented. This tool uses the results from an a priori second order diffraction analysis of the platform hull. In particular the wave-in-deck simulation program applies linear and quadratic transfer functions from the diffraction analysis as input. Since pre-computed hydrodynamic quantities are used in the simulations, very fast computations can be performed. The method is validated against experiments. Results from scaled model tests of the Statfjord A gravity-based structure (GBS) have been compared to numerical results. The comparisons are limited to regular waves. Satisfactory results are obtained from the numerical simulations. The theoretical results compare well with the experiments for the most severe cases. The vertical loads on the deck are well reproduced both during the water entry phase and the water exit phase. Moreover, the duration of the wave-in-deck event is satisfactorily predicted.

scholarly journals Evaluation of Water Impact For Symmetric Wedge by Experimental and Numerical Methods

2019 ◽  
Vol 24 (1) ◽  
pp. 221-230
Author(s):  
M. Nikfarjam ◽  
J. Koto ◽  
O.B. Yaakob ◽  
M.S. Seif ◽  
A. Aref
Keyword(s):  
Experimental Tests ◽  
Water Entry ◽  
Impact Loads ◽  
Water Impact ◽  
Wave Surface ◽  
Effective Parameters ◽  
Hydrodynamic Impact ◽  
Impact Speed ◽  
Marine Vehicles ◽  
The Impact

Abstract Evaluation of impact loads when a ship hull contacts the wave surface is one of the main issues for researchers who are going to design the structure of marine vehicles. In this paper, the results of experimental tests and numerical modeling of the distribution of pressure on different wedge-shaped models are reported and the effect of related parameters such as the deadrise angles, the weight and drop heights, is assessed. The output of analyses and the results can give appropriate approximations of the maximum impact pressures for the geometries that are similar to marine vehicle’s hull sections to estimate the hydrodynamic impact loads in different sea-states. In addition, other effective parameters such as the impact speed, acceleration and water entry process can be used for evaluating the performance of such crafts.

Anisotropy of interfacial defects in the initial stage of MOVPE GaAs growth On Si

1990 ◽  
Vol 48 (4) ◽  
pp. 592-593
Author(s):  
C. Vannuffel ◽  
C. Schiller ◽  
J. P. Chevalier
Keyword(s):  
Early Stage ◽  
Threading Dislocations ◽  
Mbe Growth ◽  
Detailed Mechanism ◽  
Si Substrates ◽  
Initial Stage ◽  
Interfacial Defects ◽  
Interfacial Dislocations ◽  
Step Growth ◽  
Essential Problem

Recently, interest has focused on the epitaxy of GaAs on Si as a promising material for electronic applications, potentially for integration of optoelectronic devices on silicon wafers. The essential problem concerns the 4% misfit between the two materials, and this must be accommodated by a network of interfacial dislocations with the lowest number of threading dislocations. It is thus important to understand the detailed mechanism of the formation of this network, in order to eventually reduce the dislocation density at the top of the layers.MOVPE growth is carried out on slightly misoriented, (3.5°) from (001) towards , Si substrates. Here we report on the effect of this misorientation on the interfacial defects, at a very early stage of growth. Only the first stage, of the well-known two step growth process, is thus considered. Previously, we showed that full substrate coverage occured for GaAs thicknesses of 5 nm in contrast to MBE growth, where substantially greater thicknesses are required.

KAJIAN DAMPAK KEBIJAKAN PENUTUPAN LOKALISASI TELEJU OLEH PEMERINTAH KOTA PEKANBARU

2017 ◽  
Vol 15 (2) ◽  
pp. 78
Author(s):  
M. Zainuddin
Keyword(s):  
Social Order ◽  
Qualitative Method ◽  
Negative Impact ◽  
Early Stage ◽  
Policy Research ◽  
Research Approach ◽  
Policy Content ◽  
The Government ◽  
Closure Policy ◽  
The Impact

This research to analyze the impact of closure policy Teleju brothel by Pekanbaru govermentin 2010. Guidelines for works are Pekanbaru Local Regulations No. 12 of 2008 on Social Order-liness. Closure this brothel inflicts positive and negative impact for society.The research wasconducted to obtain early stage formula for the government to take action against the prostitu-tion activities. This research uses policy research approach with a qualitative method, becausein prostitution activities and prohibition by goverment is an assessment that needs to be done byanalyzing documents and unstructured interview.The results showed that after the closing of the Teleju brothel have an impact on the deploy-ment of a prostitution and affect the economy of the surrounding residents. Government seeksto tackle prostitution in Pekanbaru by moving the brothel, conduct regular raids and providetraining. The effort is considered to be less than the maximum because the handling is not basedon the root of the problem and not programmed properly. There are several causes of failure ofgovernment to overcome the prostitution problem in Pekanbaru, including: policy content isless focus on the prostitution problem, the government did not proceeds with data, lack of finan-cial support, contra productive programs between local government with the police and TNI,and the policy object is difficult to be given understanding.

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