Shock Response of Ship Section to Underwater Explosion With the Cavitation Effect

2014 ◽  
Author(s):  
Chen Ying-yu ◽  
Xiongliang Yao ◽  
Xiao Wei ◽  
Liu Xiang-dong
Keyword(s):  
Simple Structure ◽  
Underwater Explosion ◽  
Pulse Load ◽  
Wave Load ◽  
Ship Structure ◽  
Structure Response ◽  
Cavitation Effect ◽  
Shock Response ◽  
Simulation Results ◽  
Structural Arithmetic

Besides the shock wave load and the gas bubble pulse load, cavitation effect has a significant influence on the ships subjected to underwater explosion. The goal of this research is to investigate the cavitation effect on the response of ship section using acoustic-structural arithmetic. Comparison between the structure response considering the cavitation effect and not, the formation mechanism of cavitation zone are discussed. The simulation results show acoustic-structural arithmetic can be used to numerical simulate the dynamic response of simple structure and ship section subjected to underwater explosion with the consideration of cavitation effect. And it also can be used to capture the cavitation in the water. Meanwhile, the simulation results show that cavitation zone generated by underwater explosion is very large, and the reloading effect is obvious with the consideration of cavitation effect. The vibration of the ship structure is more severe with the reloading, and thus more serious damage occurs as the result of the prolonged loading time.

scholarly journals Analytical Models for the Response of the Double-Bottom Structure to Underwater Explosion Based on the Wave Motion Theory

2016 ◽  
Vol 2016 ◽  
pp. 1-21 ◽  
Author(s):  
Yingyu Chen ◽  
Xiongliang Yao ◽  
Wei Xiao
Keyword(s):  
Wave Motion ◽  
Underwater Explosion ◽  
Analytical Models ◽  
Basic Unit ◽  
Stress Wave Propagation ◽  
Structure Response ◽  
Cavitation Effect ◽  
Underwater Blast ◽  
Set Up ◽  
Good Agreement

The aim of this paper is to apply the elastic wave motion theory and the classical one-dimensional cavitation theory to analyze the response of a typical double-bottom structure subjected to underwater blast. The section-varying bar theory and the general acoustic impedance are introduced to get the simplified analytical models. The double-bottom structure is idealized by the basic unit of three substructures which include the simple panel, the panel with stiffener (T-shaped), and the panel associated with girder (I-shaped). According to the simplified models, the analytical models for the corresponding substructures are set up. By taking the cavitation effect into account, the process of fluid-structure interaction can be thoroughly understood, as well as the stress wave propagation. Good agreement between the analytical solution and the finite element prediction is achieved. On the other hand, the Taylor predictions for the panel associated with girder (I-shaped) including the effects of cavitation are invalid, indicating a potential field for the analytical method. The validated analytical models are used to determine the sensitivity of structure response to dimensionless geometric parametersα-k,β-k, andγ-k. Based on the dynamic response of the substructures, we establish the approximate analytical models which are able to predict the response of double-bottom structure to underwater explosion.

scholarly journals Vibration Reduction Strategy for Offshore Wind Turbines

2020 ◽  
Vol 10 (17) ◽  
pp. 6091
Author(s):  
Haoming Liu ◽  
Suxiang Yang ◽  
Wei Tian ◽  
Min Zhao ◽  
Xiaoling Yuan ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Output Power ◽  
Wind Turbines ◽  
Reference Signal ◽  
Offshore Wind ◽  
Wave Load ◽  
Offshore Wind Turbines ◽  
Pitch Control ◽  
Simulation Results ◽  
Aerodynamic Torque

The operational environment of offshore wind turbines is much more complex than that of onshore wind turbines. Facing the persistent wind and wave forces, offshore wind turbines are prone to vibration problems, which are not conducive to their long-term operation. Under this background, first, how the wave affects the vibration characteristics of offshore wind turbines is analyzed. Based on the existing wave and wave load models, we analytically show that there exist fluctuating components related to the hydrodynamic frequency in the aerodynamic load and aerodynamic torque of offshore wind turbines. Simulation results based on a GH Bladed platform further validates the analysis. Second, in order to reduce the joint impacts of the wave, wind shear and tower shadow on the wind turbine, a variable pitch control method is proposed. The integrated tower top vibration acceleration signal is superimposed on the collective pitch reference signal, then the triple frequency (3P) fluctuating component of the wind turbine output power and the azimuth angle of each blade are converted into the pitch angle adjustment signal of each blade, which is superimposed on the collective pitch signal for individual pitch control. The simulation results show that the proposed pitch control strategy can effectively smooth the fluctuation of blade root flap-wise load caused by wind and wave, and significantly reduce the fluctuation of aerodynamic torque and output power of offshore wind turbines.

Design of Multi-Mode PID Controller and Application in Time-Delay Process

2014 ◽  
Vol 511-512 ◽  
pp. 637-642
Author(s):  
Yu Mei Chen ◽  
Fei Tan ◽  
Tao Fan
Keyword(s):  
Time Delay ◽  
Transient Response ◽  
Intelligent Control ◽  
Pid Controller ◽  
Control Algorithm ◽  
Simple Structure ◽  
Excitation Control ◽  
New Type ◽  
Simulation Results ◽  
Multi Mode

Through brief analysis of characteristics of conventional control, a new type of multi-mode intelligent control algorithm based on error information is put forward. The algorithm consists of proportional acceleration control for rapidity of transient response, differential deceleration control for stationarity of transient response and steady state excitation control for accuracy of steady response. The control algorithm is applied to time-delay process, compared with other algorithms. Simulation results show its good performance with MATLAB language. The algorithm has simple structure, good generality and easy adjustment.

Pressure Load on Rigid Structure Induced by Double Underwater Explosions

2016 ◽  
Author(s):  
Rui Han ◽  
Aman Zhang ◽  
Shiping Wang
Keyword(s):  
Shock Wave ◽  
Underwater Explosion ◽  
Time Difference ◽  
Wave Load ◽  
Underwater Explosions ◽  
Rigid Structure ◽  
Pressure Load ◽  
Adjacent Structures ◽  
Explosive Source ◽  
Source Case

Underwater explosion is a severe threat to nearby ocean structures, such as underwater construction, floating vessels. The pressure load produced by underwater explosion of explosives consists of shock wave load and the explosion bubble pulsation pressure load. After the detonation, there will be a shock wave propagating radially outwards and it’s followed by a large oscillating bubble. The shock wave has the first damaging effect on adjacent structures. Then, the collapse and high-speed jet of oscillating bubbles will cause the second damage to structures. When there are double explosive sources near a rigid structure, the mutual superposition of shock waves and the interaction between two bubbles may improve the explosive damage. If the distance between one explosive source and the rigid structure is fixed, the damage force produced by double underwater explosions is related to many factors, like the detonation time difference and the distance between two explosive sources. At first, the pressure field in single explosive source case is numerically simulated by using the AUTODYN in this paper. Next, pressure fields of underwater explosion detonated by double sources at the same time and with time difference are calculated, respectively. The flow fields in double explosive sources case are compared with that in single explosive source case. The effect of the detonation time difference and the distance between explosive sources on the damage force is investigated and analysed in detail.

scholarly journals The Fluid-Solid Interaction Dynamics between Underwater Explosion Bubble and Corrugated Sandwich Plate

2016 ◽  
Vol 2016 ◽  
pp. 1-21
Author(s):  
Hao Wang ◽  
Yuan Sheng Cheng ◽  
Jun Liu ◽  
Lin Gan
Keyword(s):  
Shock Wave ◽  
Failure Modes ◽  
Sandwich Structures ◽  
Numerical Models ◽  
Near Field ◽  
Three Dimensional ◽  
Underwater Explosion ◽  
Bubble Collapse ◽  
Fe Model ◽  
Wave Load

Lightweight sandwich structures with highly porous 2D cores or 3D (three-dimensional) periodic cores can effectively withstand underwater explosion load. In most of the previous studies of sandwich structure antiblast dynamics, the underwater explosion (UNDEX) bubble phase was neglected. As the UNDEX bubble load is one of the severest damage sources that may lead to structure large plastic deformation and crevasses failure, the failure mechanisms of sandwich structures might not be accurate if only shock wave is considered. In this paper, detailed 3D finite element (FE) numerical models of UNDEX bubble-LCSP (lightweight corrugated sandwich plates) interaction are developed by using MSC.Dytran. Upon the validated FE model, the bubble shape, impact pressure, and fluid field velocities for different stand-off distances are studied. Based on numerical results, the failure modes of LCSP and the whole damage process are obtained. It is demonstrated that the UNDEX bubble collapse jet local load plays a more significant role than the UNDEX shock wave load especially in near-field underwater explosion.

Guidelines for the Use of Approximations in Shock Response Analysis of Electronic Assemblies

1993 ◽  
Vol 115 (1) ◽  
pp. 124-130 ◽  
Author(s):  
R. F. Keltie ◽  
K. J. Falter
Keyword(s):  
Finite Element Analysis ◽  
Rigid Body ◽  
Simple Structure ◽  
Response Analysis ◽  
Element Analysis ◽  
Simply Supported ◽  
Inappropriate Use ◽  
The Finite Element Analysis ◽  
Shock Response ◽  
Electronic Assemblies

In order to reduce the time and effort to create models and prevent excessive computer run times, approximations and simplifications are often used in the finite element analysis of the shock response of electronic assemblies. Typical approximations which might be used include neglecting components which have small masses and considering highly stiff connections as rigid connections. It is difficult to determine under what conditions approximations may be applied and to what extent they affect a model’s accuracy. Rather than depending only on an analyst’s experience or intuition, guidelines are desirable to prevent the inappropriate use of approximations. To illustrate the methodology for developing guidelines, this paper examines approximations involving a simple structure which is representative of structures found in electronic assemblies. This structure consists of a rigid body attached by a flexible connection to a beam. Approximations considered were: approximating the stiffness of the connection, neglecting the mass of the rigid body, and approximating the boundary conditions of the beam as either simply-supported or clamped. In developing guidelines a large number of individual analyses were necessary. An important aspect of this investigation is our proposal for a concise format for presenting the results of many analyses. The techniques which were used to reduce the amount of data to be presented are discussed.

The Design of a MEMS Surface Resonant Magnetometer

2009 ◽  
Vol 60-61 ◽  
pp. 265-269
Author(s):  
Mu Zhi Hu ◽  
Zheng You ◽  
Jian Zhong Yang ◽  
Ling Qi Wu
Keyword(s):  
Mechanical Model ◽  
Sensitive Element ◽  
Simple Structure ◽  
Theoretical Calculations ◽  
High Sensitivity ◽  
Harmonic Excitation ◽  
First Order ◽  
Good Accordance ◽  
Simulation Results ◽  
The Magnetic Field

In this paper, a MEMS surface resonant magnetometer based on Lorentz force is presented. This magnetometer has three current carriers to sense the magnetic field and changes into deflection of beams which will be detected by the comb-capacitance. The alternating current carried by oscillate beams has the same frequency as resonant frequency of the magnetometer structure to make the deflection magnified Q (Quality-factor) times, therefore, it becomes more easily to measure. In this paper, the mechanical model of the sensitive element is established. The equations of stiffness of the system, deflection, first-order resonance frequency and sensitivity are setup and simulated in ANSYS, as well as second-order to fourth-order modal, and harmonic excitation response simulation. It can be seen that the simulation results are in good accordance with the theoretical calculations, which proves the feasibility and the rationality of the theoretical model. The dimensions of the structure are designed, as well as the processing sequence Anodic Silicon-Glass Bonding and Silicon DRIE Multi-user Bulk Micromachining Process which will be used to manufacture the magnetometer. The MEMS surface resonant magnetometer has a high sensitivity, simple structure and easy to manufacture. The prototype sensors are being manufactured in NEDI now.

Numerical Simulation of the Transient Flow in a Pump-Turbine During the Load Rejection Process With Special Emphasis on the Cavitation Effect

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Xiaolong Fu ◽  
Deyou Li ◽  
Hongjie Wang ◽  
Guanghui Zhang ◽  
Zhenggui Li ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Single Phase ◽  
Pressure Pulsation ◽  
Phase Flow ◽  
Cavitation Flow ◽  
Single Phase Flow ◽  
Pump Turbine ◽  
Cavitation Effect ◽  
Simulation Results ◽  
Load Rejection Process

Abstract At present, pumped-storage power technology is the only available and effective way for the load balancing and energy storage in the grid network scale. During the frequent switch back and forth conditions, there are severe pressure pulsation and cavitation in pump-turbines. However, their generation mechanism has not been determined yet. This work contributes to the numerical simulation of the transient behaviors in a prototype pump-turbine during the load rejection process with special emphasis on cavitation effect. In this study, the two-dimensional dynamic remesh and variable speed slide mesh methodologies were employed to perform the simulation of the transient single-phase flow and cavitation flow in a pump-turbine. The simulation results of single-phase flow and cavitation flow were both consistent with the experimental data except in local regions based on the experimental validation of prototype tests. However, the numerical results considering cavitation effects have a better behavior than those of single-phase flow in the predictions of pressure pulsation and rotational speed. Then, the cavitation flow simulation results were analyzed deeply, especially in pressure pulsation and cavitation flow field. Analysis revealed that three typical complex frequency components of pressure were captured in the cavitation flow, which significantly affect the axial hydraulic thrust on the runner. And it is validated that they are primarily induced by the cavity collapse near the trailing edges of the runner blades in reverse pump mode and the interaction between cavitation and vortex rope in draft-tube in turbine mode.

Sign in / Sign up

Export Citation Format

Share Document