Low-Frequency Bandgaps of the Lightweight Single-Phase Acoustic Metamaterials with Locally Resonant Archimedean Spirals

In order to achieve the dual needs of single-phase vibration reduction and lightweight, a square honeycomb acoustic metamaterials with local resonant Archimedean spirals (SHAMLRAS) is proposed. The independent geometry parameters of SHAMLRAS structures are acquired by changing the spiral control equation. The mechanism of low-frequency bandgap generation and the directional attenuation mechanism of in-plane elastic waves are both explored through mode shapes, dispersion surfaces, and group velocities. Meanwhile, the effect of the spiral arrangement and the adjustment of the equation parameters on the width and position of the low-frequency bandgap are discussed separately. In addition, a rational period design of the SHAMLRAS plate structure is used to analyze the filtering performance with transmission loss experiments and numerical simulations. The results show that the design of acoustic metamaterials with multiple Archimedean spirals has good local resonance properties, and forms multiple low-frequency bandgaps below 500 Hz by reasonable parameter control. The spectrograms calculated from the excitation and response data of acceleration sensors are found to be in good agreement with the band structure. The work provides effective design ideas and a low-cost solution for low-frequency noise and vibration control in the aeronautic and astronautic industries.

Analysis of Characteristics of Damping Valve Based on High-Order Discrete Scheme

In this paper, based on the high-order discrete scheme, a two-way fluid-solid coupling numerical simulation is for the damping valve plate. According to the discrete method, the governing equations of fluid structure coupling of damping valve plate are studied, including the basic conservation laws; Meanwhile, it analyzes the discretization of the control equation, including the discretization method and the high-order discretization format when the finite volume method is adopted. And based on this discrete format, a numerical simulation was performed on the damping valve, the oil flow condition is analyzed, and the velocity of the throttling hole at different time points and the throttling pressure are analyzed.

Modal analysis and experimental investigation into vibration of the diamond-beaded rope based on lumped mass

The natural vibration characteristics of the diamond-beaded rope (DBR) based on lumped mass are analyzed both theoretically and experimentally. The dynamic model of the DBR is established by means of the multi-body dynamics theory. According to Lagrange’s equations, the control equation of the DBR is derived. It mainly analyzes the influence of the parameters, such as the motion velocity of the DBR, the tension of the DBR, the length of diamond beads, the quality of diamond beads, and their position in the DBR, on the natural vibration characteristics for the DBR are studied. The results show that the natural frequencies and the corresponding vibration shapes of the DBR based on lumped mass change significantly when the variations of the above parameters are considered. In the process of the movement of the DBR, the random impact force of diamond beaded is the key factor that causes the natural frequency of the DBR to fluctuate., In the high-order modal analysis, the natural frequency and vibration mode of the DBR fluctuate more obviously. The relative error of the result between the calculated and the measured is less than 10%, which validates the proposed method.

Numerical Simulation of Thermal Field in Mass Concrete With Pipe Water Cooling

Water pipe cooling is mainly used to control temperature in the construction of mass concrete structures. It is important to reveal how to accurately stimulate the temperature field of mass concrete under action of this water pipe cooling. This paper presents a new method for this purpose. In this method, the contact surface of the water pipe and the concrete is used as the heat dissipation surface into the control equation and the composite Multiquadrics radial basis function (MQ-RBF) and low-order linear polynomial combination are used to discrete the spatial domain. The heat dissipation surface of the water pipe is included in the boundary conditions so that there is no need to build the refined water pipe modeling. This new method not only reduces the calculation cost but also ensures calculation accuracy. Through four calculation examples, this paper show that the algorithm has advantages in the numerical simulation of the concrete temperature field with water pipe cooling.

Based on a biological particle model to predict the trace behavior of fish

A biological particle model is used to predict the upward trajectory of fish under a dam, the biological particle model refers to a fish as a particle and considers the flow rate, velocity gradient and turbulent energy of the fish, as a condition of retrospective behaviour, a control equation is used to simplify the fish's retroactive behaviour and establish a model programmed in MATLAB to develop a fish traceability prediction program. According to the program, the upward trajectory of the fish under the dam is predicted, there are three types of up-tracking channels under the dam according to the average widths of the up-tracking channels along the right bank of the channel, along the middle of the channel, and along the left bank of the channel and the average widths are 10, 14 and 7 m, respectively. The three existing fish import locations in fishway project are evaluated, and optimization recommendations are provided, it's recommended to add a fishway inlet along the right bank of upstream channel. In addition, this paper provides a feasible technical methodology that a biological particle model can be used to predict the upward trajectory of fish in similar fishway projects.

Slope- watershed coupling simulation under different vegetation coverage based on GAST model

A non-equilibrium sediment transport soil erosion model based on finite volume method (FVM) coupled with two-dimensional hydrodynamic process is proposed, application of the GPU techniques in the numerical model, making it possible to simulate the sediment transport and bed evolution in a high resolution but efficient way. The first-order Gudonov format FVM is used to discreting the control equation. The variables on both sides of the unit interface are obtained by limiting slope interpolation. An efficient and robust non-negative depth reconstruction algorithm is used to solve the dry-wet boundary problem. This algorithm makes the model have second-order accuracy in space, and also effectively suppresses the numerical oscillation. Harten, Lax van Leer Contact (HLLC) approximate Riemann solver is used to calculate mass and momentum flux, and the friction source term is calculated by the proposed split point implicit method. These values are evaluated by a novel 2D edge-based MUSCL scheme. The code is programmed using C++ and CUDA, which can be run on GPU to greatly accelerate the calculation speed. In this paper, two numerical experiments show that the model performs well in accuracy and robustness of the algorithm in the process of slope erosion and watershed erosion. The constructed model can simulate the soil erosion of slope and watershed gully under different vegetation coverage, and characterize the erosion process of interaction between slope and gully.

Design and Optimization of the Resonator in a Resonant Accelerometer Based on Mode and Frequency Analysis

This study aims to develop methods to design and optimize the resonator in a resonant accelerometer based on mode and frequency analysis. First, according to the working principle of a resonant accelerometer, the resonator is divided into three parts: beam I, beam II, and beam III. Using Hamilton’s principle, the undamped dynamic control equation and the ordinary differential dynamic equation of the resonant beam are obtained. Moreover, the structural parameters of the accelerometer are designed and optimized by using resonator mode and frequency analysis, then using finite element simulation to verify it. Finally, 1 g acceleration tumbling experiments are built to verify the feasibility of the proposed design and optimization method. The experimental results demonstrate that the proposed accelerometer has a sensitivity of 98 Hz/g, a resolution of 0.917 mg, and a bias stability of 1.323 mg/h. The research findings suggest that according to the resonator mode and frequency analysis, the values of the resonator structural parameters are determined so that the working mode of the resonator is far away from the interference mode and avoids resonance points effectively. The research results are expected to be beneficial for a practical resonant sensor design.

Influence of the weight coefficients of measurements on the consistency of the assessment and calculation results of the power supply system steady-state operation conditions

The aim of this work is to develop an improved procedure for assessing the state of power supply systems based on adjusting the weight coefficients of measurements. To this end, non-linear optimisation methods were used. The control equations and the solution of the simultaneous linear equations were performed using the Crout method. The results of the calculation of the electrical power steady-state mode were considered as a reference. The lower the difference between the evaluation and steady-state calculation results, the higher the accuracy of the overall state assessment procedure. The problem of correcting the weight factors is set and solved as a nonlinear optimisation problem, where the optimisation parameters are taken as the dispersion of the measurements. The objective function was formulated as follows: to minimise the measurement evaluation dispersions that are part of a single control equation by maximising the active power measurements dispersion in the swing bus of the power supply system. In this study, limitations in the form of equation and inequality are monitored. The problem of optimising the dispersions is solved after the first iteration of the state assessment; starting with the second iteration, the state assessment is performed with new measurement weight factors. The calculations were performed on a 6-node test circuit. The control equations are drawn from the current measurements. The measurements data on the selected control equation of the test circuit are used to calculate the target function. The accuracy of the dispersions redistribution and their extreme values are controlled by the limitations. The results showed that, when adjusting the dispersion of measurements, the power assessments at all nodes are closer to the steady-state mode calculation results.