1,544 research outputs found

    Experimental and numerical analysis of directional added mass effects in partially liquid-filled horizontal pipes

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    The change of pipe natural frequencies due to added mass effects has been investigated in two cylindrical horizontal pipes from empty to completely water filled cases with various intermediate partially-filled conditions. The added mass coefficients of the three first vertical and horizontal modes of vibration have been determined with both experimental modal analysis and finite element analysis (FEA) acoustic-structural numerical simulations, which showed good agreement. The vertical and horizontal added mass coefficients present different behaviors as a function of the water level. Moreover, the pipe cross sectional dimensions determine the magnitude of these effects. For generalization to any pipe size, dependency of the directional added mass coefficients with new vertical and horizontal added mass estimators has been found. These estimators can be used in practical situations with horizontally mounted cylindrical pipes as a reference to predict and quantify air content.Postprint (author's final draft

    Analysis of coupling vibration characteristics of electrically driven pile hammer linkage system

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    In order to solve the problem that electromechanical coupling had influences on the control effect of multi-pile hammers linkage, the coupling influence rules were studied. With the complex system of hammer-pile-soil being simplified, the dynamic model was constructed for the two pile hammers vibration system. The mathematical equations of systemic electromechanical coupling were established. Based on the Hamilton principle, synchronous operation conditions and system stability were established. Simulation model was developed with MATLAB/Simulink for numerical simulation. The electromechanical coupling processes and the basic system rules were obtained under different electrical motors’ speeds, the initial phase differences, soil parameters and fixing parameters. It could be found that electromechanical coupling might result in self-synchronization under given conditions. Finally, the mathematical model’s validity, theoretical derivation and simulation results were proved by some experiments. The analytical conclusions of electromechanical coupling rules provide the theoretical evidence for making control strategy on electric control linkage mode, and the basis for related engineering applications and experiments

    Photoelastic Stress Analysis

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    Sliding mode force tracking control for active hydro-pneumatic suspension

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    A nonlinear state equation model of Active Hydro-Pneumatic suspension (AHP) system is established basing on power bond graph theory. The nonlinear characteristics of stiffness and friction of the hydro-pneumatic spring actuator and the oil compressibility are considered in modeling. Meanwhile, a theoretical analysis is conducted for dynamic structural characteristics of hydro-pneumatic spring actuator. A sliding mode control (SMC) strategy is presented which has two closed-loops, where the outer loop considers the sprung velocity of skyhook reference model output as tracking target and the inner loop regards the desired force of the sliding mode solver as tracking target. Simultaneously, the sliding mode control laws of inner and outer loops are deduced. Especially, a divergence problem of outer loop sliding model solver caused by time delay is analyzed and a stabilization control algorithm is put forward to solve it. The accurate tracking of desired force of actuator and the improvement of ride quality are realized, while the effectiveness of the proposed sliding mode control law and stabilization control algorithm are verified through simulation studies of relevant contrast test

    Study on water hammer effect in turbulent flow through the pipe system

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    The purpose of this research is to study water hammer effect in turbulent flow through the pipe system. The water hammer occurs when the water flow in the pipeline is suddenly stopped by the valve. Water hammer can cause the pipe to break if the pressure is high enough. An experimental method has been conducted to investigate the effect of design parameters such as difference kind of material properties of pipes and the effect of the flow rate of fluid on the frequency (Hz) and the maximum acceleration of vibration signal (m/s2) during water hammer effect, the vibration signal is captured by using the DEWE-41-T-DSA signal analysis and piezoelectric accelerometer sensor. Data signal is transferred to DEWESoft software to be analyzed using the Fast Fourier Transform (FFT) method. We found that the maximum acceleration vibration signal will increase the flow rate of fluid increase. Besides, the maximum acceleration vibration signal of UPVC pipe is higher than HDPE pipe. Meanwhile, for the frequency, the experimental result shows that the larger frequency is the UPVC pipe compare with the HDPE pipe. This is due to the compressibility of fluid and elasticity of the pipe. Therefore, it can be concluded that the UPVC pipe deal with more water hammer effect compares to the HDPE pipe due to the mechanical properties difference of UPVC and HDPE pipe

    Modal testing and FE-model validation of azimuthing thruster

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    Feasibility Evaluation of a Vibration-Based Leak Detection Technique for Sustainable Water Distribution Pipeline System Monitoring

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    Conventional water pipeline leak-detection surveys employ labor-intensive acoustic techniques, which are usually expensive and less useful for continuous monitoring of distribution pipelines. Based on a comprehensive review of literature and available commercial products, it has been recognized that despite previous studies and products attempting to address the limitations of the conventional surveys by proposing and evaluating a myriad of leak-detection techniques (LDTs), they lacked extensive validation on complex looped systems. Additionally, they offer limited compatibility with some pipe materials such as those made of plastic and may even fail to distinguish leaks from other system disturbances. A novel LDT that addresses some of these limitations is developed and evaluated in the current study using an experimental set-up that is representative of a real-world pipeline system and made of Polyvinyl Chloride (PVC) pipe. The studied LDT requires continuous monitoring of the change in the cross spectral density of surface vibration measured at discrete locations along the pipeline. This vibration-based LDT was hypothesized to be capable of not only detecting the onset of leakage, but also determining its relative severity in complex pipeline systems. Findings based on a two-phase, controlled experimental testing revealed that the proposed LDT is capable of detecting leakages and estimating their relative severities in a real-size, multi-looped pipeline system that is comprised of multiple joints, bends and pipes of multiple sizes. Furthermore, the sustainability merits of the proposed LDT for a representative application scenario are estimated. Specifically, life cycle costs and energy consumption for monitoring the large diameter pipelines in the water distribution system of the Charleston peninsula region in South Carolina are estimated by developing conceptual prototypes of the sensing, communication and computation schemes for practically employing the proposed LDT. The prototype designs are informed by the knowledge derived from the two-phase experimental testing campaign. Overall, the proposed study contributes to the body of knowledge on water pipeline leak detection, specifically to non-intrusive vibration-based monitoring, applications on plastic pipelines, and smart and sustainable network-wide continuous monitoring schemes

    Effect of sink flow on dual-valve electro-hydraulic excitation system

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    In this study, the main goal is to investigate the displacement gain characteristics of novel dual-valve Electro-Hydraulic Excitation system (EHES). Relative to conventional system, the dual-valve system can improve the amplitude range, but the range is always affected by some nonlinear factors. In order to analysis on the issue, a nonlinear mathematical model of dual-valve EHES is established based on Bernoulli and classical electro-hydraulic servo equation. Then, the results of numerical simulations by using of the MATLAB/Simulink software are compared with experimental results. Simulation and experimental results show that the sink flow mainly influences on the flow dynamic characteristics of dual-valve EHES. Because of that, dual-valve EHES only can improve 50 %-70 % of displacement within 5 to 50 Hz of excitation frequency and 45 %-80 % of displacement amplitude within 20 % to 100 % of command value
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