scholarly journals Numerical and analytical assessment of hydraulic pressure on the inner wall of the deep-water caisson under sudden flooding risk

2021 ◽  
pp. 002029402110108
Author(s):  
Jie Hong ◽  
Kai Wei ◽  
Shunquan Qin
Keyword(s):  
Numerical Model ◽  
Deep Water ◽  
Analytical Method ◽  
Structural Safety ◽  
Experimental Program ◽  
Engineering Practice ◽  
Hydraulic Pressure ◽  
Turbulence Effect ◽  
Analytical Assessment ◽  
Flooding Risk

Sudden flooding is one of the major risks for the drainage sinking construction of deep-water caisson. The damage of inner walls due to hydraulic pressure induced by sudden flooding threatens the labor and structural safety. This study developed the numerical model and analytical method to assess the hydraulic pressure on the inner walls of both the balanced and sudden-sinking caisson under sudden flooding risk. An experimental program of sudden flooding into a caisson specimen was conducted in a water basin to validate the numerical model and the analytical method for balanced caisson. The numerical and analytical methods were then illustrated by an actual engineering practice to show the hydraulic pressure on the inner walls for the caisson under balanced and sudden-sinking state, respectively. The experimental validation and engineering illustration prove that the numerical model is effective in the assessment of hydraulic pressure of caisson under sudden flooding, especially for the complicated case that includes the turbulence effect and sudden sinking, while the analytical method can calculate the quasi-static value of the hydraulic pressure more efficiently. The presented methods provide the engineers with alternative tools to learn more about the sudden flooding risk of the deep-water caisson.

scholarly journals Numerical Evaluation of Structural Safety of Linear Actuator for Flap Control of Aircraft Based on Airworthiness Standard

Aerospace ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 104
Author(s):  
Dong-Hyeop Kim ◽  
Young-Cheol Kim ◽  
Sang-Woo Kim
Keyword(s):  
Numerical Analysis ◽  
Analytical Method ◽  
Safety Evaluation ◽  
Experimental Tests ◽  
Structural Safety ◽  
Linear Actuator ◽  
The Finite Element Method ◽  
Margin Of Safety ◽  
Verification Methodology ◽  
The Given

Airworthiness standards of Korea recommend verifying structural safety by experimental tests and analytical methods, owing to the development of analysis technology. In this study, we propose a methodology to verify the structural safety of aircraft components based on airworthiness requirements using an analytical method. The structural safety and fatigue integrity of a linear actuator for flap control of aircraft was evaluated through numerical analysis. The static and fatigue analyses for the given loads obtained from the multibody dynamics analysis were performed using the finite element method. Subsequently, the margin of safety and vulnerable area were acquired and the feasibility of the structural safety evaluation using the analytical method was confirmed. The proposed numerical analysis method in this study can be adopted as an analytical verification methodology for the airworthiness standards of civilian aircraft in Korea.

Focused Plunging Breaking Waves Impact on Cylinder Group in Deep Water

2021 ◽  
Author(s):  
Ting Cui ◽  
Arun Kamath ◽  
Weizhi Wang ◽  
Lihao Yuan ◽  
Duanfeng Han ◽  
...  
Keyword(s):  
Free Surface ◽  
Deep Water ◽  
Breaking Waves ◽  
Surface Elevation ◽  
Relative Distance ◽  
Structural Safety ◽  
Wave Forces ◽  
Free Surface Elevation ◽  
Single Cylinder ◽  
Numerical Wave

Abstract The correct estimation of wave loading on a cylinder in a cylinder group under different impact scenarios is essential to determine the structural safety of coastal and offshore structures. This scenario differs from the interaction of waves with a single cylinder but not a lot of studies focus on cylinder groups under different arrangements. In this study, the interaction between plunging breaking waves and cylinder groups in deep water is investigated using the two-phase flow model in REEF3D, an open-source computational fluid dynamics program. The Reynolds-averaged Navier-Stokes equation with the two equation k–Ω turbulence model is adopted to resolve the numerical wave tank, with free surface calculated using the level set method. In this study, focused waves in deep water were modeled with a fixed wave steepness method. Wave breaking occurs when the steepness of the wave crest front satisfies the breaking criteria. The model is validated by comparing the numerical wave forces and free surface elevation with measurements from experiments. The computational results show fairly good agreement with experimental data for both free surface elevation and wave forces. Four cases are simulated to investigate the interaction of breaking waves with a cylinder group with different relative distance, number of cylinders and arrangement. Results show that breaking wave forces on the upstream cylinder are smaller than on a single cylinder with a relative distance of one cylinder diameter. The wave forces on cylinders in the pile group are effected by the relative distance between cylinders. The staggered arrangement has a significant influence on the wave forces on the first and second cylinder. The interaction inside a cylinder group mostly happens between the neighbouring cylinders. These interactions are also effected by the relative distance and the numbers of the neighbouring cylinders.

Optimization of Trimaran Design Configuration in Calm and Deep Water

2020 ◽  
Author(s):  
Renato Skejic ◽  
Sverre A. Alterskjær
Keyword(s):  
Deep Water ◽  
Optimization Procedure ◽  
Wave Theory ◽  
Point Of View ◽  
Engineering Practice ◽  
Total Resistance ◽  
Operational Parameters ◽  
Viscous Effects ◽  
Greenhouse Gasses ◽  
Hard Particles

The field of sea based modern shipping activities is constantly seeking for its improvements to achieve the economically justified operational patterns. In the same time, the sea transportation activities also need to satisfy currently imposed and, as well as, upcoming in the near future, safety and ecologically friendly footprint characteristics when it comes to the emission of greenhouse gasses and hard particles [1]. Fulfilment of the stated requirements consequently asks for the determination of certain vessels operational parameters such as the total resistance of a vessel which estimation is frequently carried out for predefined calm and deep-water environmental scenario. Current work is dealing with investigation of the total resistance parameter in calm and deep water for the preselected types of the trimaran ship hull configurations. The total resistance is estimated according to [2] recommended procedure through applicability of the robust and reliable method which is capable to address the problem of wave resistance prediction in calm and deep water. The method has origin in ordinary and modified Michell thin – ship wave theory by considering the viscous effects [3]. The differences between the utilized theories are discussed from the qualitative and quantitative point of view of the obtained results in comparison to the open source available theoretical experimental data and from the perspective of common engineering practice. Finally, based on the above description, the performed total resistance studies are used as a base for formulation of the optimization procedure which may be used in the trimaran vessel preliminary designs in the range of the forward speeds commonly expected during the normal operational life of the investigated trimaran vessel.

scholarly journals Effect of Steel Fibers on the Hysteretic Performance of Concrete Beams with Steel Reinforcement—Tests and Analysis

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2923 ◽  
Author(s):  
Violetta K. Kytinou ◽  
Constantin E. Chalioris ◽  
Chris G. Karayannis ◽  
Anaxagoras Elenas
Keyword(s):  
Reinforced Concrete ◽  
Steel Reinforcement ◽  
Steel Fibers ◽  
Experimental Program ◽  
Engineering Practice ◽  
Cracking Behavior ◽  
Tension Softening ◽  
Proposed Model ◽  
Hysteretic Performance ◽  
Cracking Performance

The use of fibers as mass reinforcement to delay cracking and to improve the strength and the post-cracking performance of reinforced concrete (RC) beams has been well documented. However, issues of common engineering practice about the beneficial effect of steel fibers to the seismic resistance of RC structural members in active earthquake zones have not yet been fully clarified. This study presents an experimental and a numerical approach to the aforementioned question. The hysteretic response of slender and deep steel fiber-reinforced concrete (SFRC) beams reinforced with steel reinforcement is investigated through tests of eleven beams subjected to reversal cyclic loading and numerical analysis using 3D finite element (FE) modeling. The experimental program includes flexural and shear-critical SFRC beams with different ratios of steel reinforcing bars (0.55% and 1.0%), closed stirrups (from 0 to 0.5%), and fibers with content from 0.5 to 3% per volume. The developed nonlinear FE numerical simulation considers well-established relationships for the compression and tensional behavior of SFRC that are based on test results. Specifically, a smeared crack model is proposed for the post-cracking behavior of SFRC under tension, which employs the fracture characteristics of the composite material using stress versus crack width curves with tension softening. Axial tension tests of prismatic SFRC specimens are also included in this study to support the experimental project and to verify the proposed model. Comparing the numerical results with the experimental ones it is revealed that the proposed model is efficient and accurately captures the crucial aspects of the response, such as the SFRC tension softening effect, the load versus deformation cyclic envelope and the influence of the fibers on the overall hysteretic performance. The findings of this study also reveal that SFRC beams showed enhanced cyclic behavior in terms of residual stiffness, load-bearing capacity, deformation, energy dissipation ability and cracking performance, maintaining their integrity through the imposed reversal cyclic tests.

scholarly journals Numerical Modeling and Dynamic Analysis of a Wave-Powered Reverse-Osmosis System

2018 ◽  
Vol 6 (4) ◽  
pp. 132
Author(s):  
Yi-Hsiang Yu ◽  
Dale Jenne
Keyword(s):  
Numerical Model ◽  
Reverse Osmosis ◽  
Flow Rate ◽  
Wave Energy ◽  
Energy Resource ◽  
Diffraction Method ◽  
Hydrodynamic Performance ◽  
Water Model ◽  
Hydraulic Pressure ◽  
Water Production

A wave energy converter (WEC) system has the potential to convert the wave energy resource directly into the high-pressure flow that is needed by the desalination system to pump saltwater to the reverse-osmosis membrane and provide the required pressure level to generate freshwater. In this study, a wave-to-water numerical model was developed to investigate the potential use of a wave-powered desalination system (WPDS) for water production. The model was developed by coupling a time-domain radiation-and-diffraction method-based numerical tool (WEC-Sim) for predicting the hydrodynamic performance of WECs with a solution-diffusion model that was used to simulate the reverse-osmosis (RO) process. The objective of this research is to evaluate the WPDS dynamics and the overall efficiency of the system. To evaluate the feasibility of the WPDS, the wave-to-water numerical model was applied to simulate a desalination system that used an oscillating surge WEC device to pump seawater through the system. The hydrodynamics WEC-Sim simulation results for the oscillating surge WEC device were validated against existing experimental data. The RO simulation was verified by comparing the results to those from the Dow Chemical Company’s reverse osmosis system analysis (ROSA) model, which has been widely used to design and simulate RO systems. The wave-to-water model was then used to analyze the WPDS under a range of wave conditions and for a two-WECs-coupled RO system to evaluate the influence of pressure and flow rate fluctuation on the WPDS performance. The results show that the instantaneous energy fluctuation from waves has a significant influence on the responding hydraulic pressure and flow rate, as well as the recovery ratio and, ultimately, the water-production quality. Nevertheless, it is possible to reduce the hydraulic fluctuation for different sea states while maintaining a certain level of freshwater production, and a WEC array that produces water can be a viable, near-term solution to the nation’s water supply. A discussion on the dynamic impact of hydraulic fluctuation on the WPDS performance and potential options to reduce the fluctuation and their trade-offs is also presented.

Reliability analysis for a hypersonic aircraft’s wing spar

2019 ◽  
Vol 91 (4) ◽  
pp. 549-557
Author(s):  
Yuhui Wang ◽  
Peng Shao ◽  
Qingxian Wu ◽  
Mou Chen
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Strength Degradation ◽  
Structural Safety ◽  
Engineering Practice ◽  
Flight Safety ◽  
Content Type ◽  
Hypersonic Aircraft ◽  
Analysis Scheme ◽  
Wing Spar

Purpose This paper aims to present a novel structural reliability analysis scheme with considering the structural strength degradation for the wing spar of a generic hypersonic aircraft to guarantee flight safety and structural reliability. Design/methodology/approach A logarithmic model with strength degradation for the wing spar is constructed, and a reliability model of the wing spar is established based on stress-strength interference theory and total probability theorem. Findings It is demonstrated that the proposed reliability analysis scheme can obtain more accurate structural reliability and failure results for the wing spar, and the strength degradation cannot be neglected. Furthermore, the obtained results will provide an important reference for the structural safety of hypersonic aircraft. Research limitations/implications The proposed reliability analysis scheme has not implemented in actual flight, as all the simulations are conducted according to the actual experiment data. Practical implications The proposed reliability analysis scheme can solve the structural life problem of the wing spar for hypersonic aircraft and meet engineering practice requirements, and it also provides an important reference to guarantee the flight safety and structural reliability for hypersonic aircraft. Originality/value To describe the damage evolution more accurately, with consideration of strength degradation, flight dynamics and material characteristics of the hypersonic aircraft, the stress-strength interference method is first applied to analyze the structural reliability of the wing spar for the hypersonic aircraft. The proposed analysis scheme is implemented on the dynamic model of the hypersonic aircraft, and the simulation demonstrates that a more reasonable reliability result can be achieved.

Analytical Method for Hydrodynamic Force in Finite-Length Tilting-Pad Journal Bearing Including Turbulence Effect

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Yingze Jin ◽  
Xiaoyang Yuan
Keyword(s):  
Finite Length ◽  
Analytical Method ◽  
Nonlinear Dynamic ◽  
Separation Of Variables ◽  
Dynamic Performance ◽  
Published Data ◽  
Hydrodynamic Bearing ◽  
Low Viscosity ◽  
Tilting Pad ◽  
Turbulence Effect

Abstract To improve the efficiency in nonlinear dynamic calculation of finite-length tilting-pad journal bearings (TPJBs) under dynamic loads, an analytical method for hydrodynamic bearing forces, which considers the turbulence effect, is proposed using the method of separation of variables under the dynamic Gümbel boundary condition. No thermal effects are considered because this method is designed for the low viscosity case. The infinitely long bearing pressure is introduced as the circumferential pressure, and a general solution of the nonhomogeneous Reynolds equation is derived as the axial pressure. The turbulence model of Ng and Pan is characterized by a linear function of film thicknesses. A complete analytical expression of hydrodynamic bearing forces is derived. The analytical simulation shows slight differences and extremely low time expense in lubricating and dynamic performance compared to published data and finite difference method (FDM) simulation. The analytical method could be used to fast evaluate the nonlinear dynamic performance of a TPJB-rotor system in the low viscosity environment, supporting the nonlinear dynamic design of the system.

The Floating Harbour Transhipper: New-Generation Transhipment of Bulk Ore Products

2015 ◽  
Author(s):  
Gregor J. Macfarlane ◽  
Nicholas T. M. Johnson ◽  
Lauchlan J. Clarke ◽  
Ross J. Ballantyne ◽  
Kevin A. McTaggart
Keyword(s):  
Deep Water ◽  
Scale Model ◽  
Experimental Program ◽  
Material Transfer ◽  
Mining Operations ◽  
Sea Transport ◽  
Large Bulk ◽  
Physical Scale ◽  
Seakeeping Performance ◽  
Feeder Vessel

Bulk products such as iron ore and coal are usually shipped directly from shore facilities using large bulk carriers. This often involves significant cost due to major dredging operations, long jetties, large storage sheds and the acquisition of large tracts of coastal land. The costs of direct shore to an ocean-going export vessel (OGV) loading often run into billions of dollars — prohibitive for small- to medium-scale mining operations, particularly in remote regions with only distant access to deep water ports. The current industry standard for mitigating these issues is transhipping; the bulk cargo is transported from a smaller shore based facility to the export vessel moored in deep water by a small feeder vessel. Transhipment, while mitigating many of these issues, does introduce other concerns with respect to limiting seastate, environmentally harmful dust and potential spillage during materials transfer. The Australian company Sea Transport Corporation and the Australian Maritime College at the University of Tasmania are developing new technology for bulk ore transhipment: the floating harbour transhipper (FHT). The FHT is essentially a large floating warehouse with an aft well dock to support material transfer operations from the feeder vessel. The major advantages to the mining export industry are in the form of environmental and economic improvements, in some cases completely avoiding expensive dredging while minimising the environmentally invasive onshore infrastructure. In addition, the whole process is enclosed, therefore eliminating grab spillage and dust transport issues common to other transhipping methods. This paper presents an overview of the main hydrodynamic issues currently being investigated: primarily the interaction between multiple floating bodies close to one another in a seaway. The two primary ship-to-ship interactions that are being investigated are the effects experienced by the feeder vessel when it is docking or undocking within the FHT well dock and the interactions between the three vessels when operating in close proximity in an open seaway. A combination of physical scale model experiments and numerical techniques is employed, with a significant portion of the experimental program dedicated to the validation of the numerical simulation codes used to investigate the behaviour of the vessels. ShipMo3D is an object based library developed by DRDC for the purpose of analysing the seakeeping performance of vessels operating in a seaway in either the frequency or time domain. The capabilities of ShipMo3D are applied to this novel application in an attempt to provide realistic simulations of the interaction between the vessels of the FHT system. DualSPHysics, an open source Smoothed Particle Hydrodynamics (SPH) code, is being applied to the domain within the very restricted water environment of the FHT well dock to investigate the fluid flow behaviour and the effect that this has on the feeder vessel when entering/exiting.

Experimental Program of Indoor Model Research about Single Pile Negative Friction

2014 ◽  
Vol 501-504 ◽  
pp. 160-165
Author(s):  
Chang Liu Chen ◽  
Song Qi Wei ◽  
Shuai Hua Ye ◽  
Yan Liu
Keyword(s):  
Skin Friction ◽  
Pile Foundation ◽  
Scale Model ◽  
Experimental Program ◽  
Engineering Practice ◽  
Negative Skin Friction ◽  
Friction Resistance ◽  
Model Research ◽  
Reduced Scale ◽  
Selection Of

This article aims to study the influence of negative skin friction resistance of waterishlogged pile foundation, through indoor scale model test of pile foundation in the loess areas. The program involved in the model similar than design, the model groove design, the selection of test materials, the design of the ground soil, the layout of measuring points and the research of load method in the test. Through the experimental study on the reduced scale model, we can deepen the understanding of the action mechanism of negative skin friction resistance of the pile, which could guide the engineering practice and design.

scholarly journals Improved Analytical Method for Longitudinal Strain Analysis of Buried Pipelines Subjected to Thaw Slumping Load

2021 ◽  
Vol 9 ◽  
Author(s):  
Beilei Ji ◽  
Xiaoben Liu ◽  
Dinaer Bolati ◽  
Yue Yang ◽  
Jinxu Jiang ◽  
...  
Keyword(s):  
Internal Pressure ◽  
Wall Thickness ◽  
Analytical Method ◽  
Analytical Methods ◽  
Longitudinal Strain ◽  
Compressive Strain ◽  
Slope Angle ◽  
Structural Safety ◽  
Buried Pipelines ◽  
Permafrost Regions

Thawing landslide is a common geological disaster in permafrost regions, which seriously threatens the structural safety of oil and gas pipelines crossing permafrost regions. Most of the analytical methods have been used to calculate the longitudinal stress of buried pipelines. These analytical methods are subjected to slope-thaw slumping load, and the elastic characteristic of the soil in a nonlinear interaction behavior is ignored. Also, these methods have not considered the real boundary at both ends of the slope. This study set out to introduce an improved analytical method to accurately analyze the longitudinal strain characteristics of buried pipelines subjected to slope-thaw slumping load. In this regard, an iterative algorithm was based on an ideal elastoplastic model in the pipeline-soil interaction. Based on field monitoring and previous finite element results, the accuracy of the proposed method was validated. Besides, a parametric analysis was conducted to study the effects of wall thickness, internal pressure, ultimate soil resistance, and slope angle on the maximum longitudinal strain of the pipeline. The results from the compression section showed that the pipeline is more likely to yield, indicating an actual situation in engineering. Moreover, the maximum longitudinal tensile and compression strain of pipelines decrease with increasing the wall thickness, internal pressure, ultimate resistance of soil, and slope angle. Finally, based on the pipeline limit state equations in CSA Z662-2007 and CRES which considered the critical compression factor comprehensively, the critical slumping displacements for both tensile and compressive strain failures were derived for reference. The research results attach great significance to the safety of pipeline under slope.

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