Advances in Applied Mechanics draws together recent, significant advances in various topics in applied mechanics. Published since 1948, the book aims to provide authoritative review articles on topics in the mechanical sciences. The book will be of great interest to scientists and engineers working in the various branches of mechanics, but will also be beneficial to professionals who use the results of investigations in mechanics in various applications, such as aerospace, chemical, civil, environmental, mechanical, and nuclear engineering. * Includes contributions from world-leading experts that are acquired by invitation only* Beneficial to scientists, engineers, and professionals who use the results of investigations in mechanics in various applications, such as aerospace, chemical, civil, environmental, mechanical, and nuclear engineering.* Covers not only traditional topics, but also important emerging fields

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Advances in Applied Mechanics

By R. Von Mises. Completed by H. Geiringer and G. S. S. Ludford New York : Academic Press Inc. Pp. 514. Price $15.00 The book under review is entirely devoted to an account of the exact theories of fluid flow. It was begun by R. Von Mises who intended it to be a comprehensive work on compressible flow, but when he died in 1953 only the first three chapters had been written.

Mathematical Theory of Compressible Fluid Flow

Structural vibration and fluid-borne noise induced by turbulent flow through a 90° piping elbow with/without a guide vane

Vibro-acoustic characteristics of cylindrical shells with complex acoustic boundary conditions

Vibration analysis of fluid-filled functionally graded material (FGM) cylindrical shells (CSs) is investigated with ring supports The shell problem is formulated by deriving strain and kinetic energies of a vibrating cylindrical shell (CS) The method of variations of Hamiltonian principle is utilized to change the shell integral problem into the differential equation (DE) expression Three differential equations (DE) in three unknown for displacement functions form a system of partial differential equations (PDEs) The shells are restricted along the thickness direction by ring supports The polynomial functions describe the influence of the ring supports and have the degree equal to the number of ring supports Fluid loaded terms (FLT) are affixed with the shell motion equations The acoustic wave equation states the fluid pressure designated by the Bessel functions of first kind Axial modal deformation functions are specified by characteristic beam functions which meet end conditions imposed on two ends of the shell The Galerkin method is employed to get the shell frequency equation Natural frequency of FGM cylindrical shell is investigated by placing the ring support at different position with fluid for a number of physical parameters For validity and accuracy, results are obtained and compared with the data in open literature A good agreement is achieved between two sets of numerical results

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Vibration Characteristics of Fluid-Filled Functionally Graded Cylindrical Material with Ring Supports

The characteristics of the sound radiation and vibrational power flow of the partially submerged cylindrical shell under a harmonic excitation are studied. The approximate acoustic boundary of the free surface is used to solve the fluid domain. The structure-fluid coupling equation is established based on the Flugge and Helmholtz theories. The far-field sound pressure is calculated and compared with that in infinite field. It is found that the far-field sound pressure presents large gap in different immersion status in the presence of the free surface while the results of the input power flow in these cases have less differences.

The Vibro-Acoustic Characteristics of the Cylindrical Shell Partially Submerged in the Fluid

A hybrid numerical method of combining Large Eddy Simulation (LES) and Lighthill’s acoustic analogy theory is utilized to simulate the flow-induced noise at low Mach numbers. The aerodynamic noise generated by flow through a cavity, which is similar to a valve, is simulated and the results are validated by comparing with the open literature. In the simulation, the turbulent flow is computed with LES. After this, the flow field simulation results are used to compute the flow-induced noise with Lighthill’s acoustic analogy theory based on the commercial software ACTRAN. Finally, the simulation results of the flow-induced noise, including the sound pressure level and the peak frequencies, are analyzed and compared with experimental data. It is validated that the hybrid method of combining LES and Lighthill’s acoustic analogy theory used in this paper is feasible and reliable in engineering applications.

Flow-Induced Noise Simulation Based on LES/Lighthill Hybrid Method

Recently, the Euler strut is used as the supporting spring in the low frequency isolation. An Euler spring is a column or strut of steel material which is compressed elastically beyond its buckling load, which makes the ratio of the isolated mass to the mass of the supporting spring maximum, and greatly increasing the internal resonant frequencies of the isolator. In this research, the unique mechanical properties and the expressions of the displacement transmissibility of the Euler strut are deduced. The influences of structural parameters of the strut on the stiffness and vibration isolation characteristics are investigated in detail. The results show that the Euler strut has the potential in low frequency vibration isolation, and the length and breadth of the strut can influence the stiffness, transmissibility and critical loading mass respectively.

Vibration Isolation Characteristics of Euler Strut Spring Used in Low Frequency Vibration Isolation System

In this paper, the vibration and power flow characteristics of stiffened plate and cylindrical shell structures are investigated by using finite element method. The power flow formulas of basic shell structural elements are given at first. Then a simply supported plate and stiffened plate’s input power flow characteristics and power flow vectors are investigated. The effects of stiffeners in plates are discussed. For a simply supported cylindrical shell, the influence of the structural damping, viscous damper and stiffeners on the cylindrical shell’s input power flow characteristics and propagated power flow characteristics are discussed in detail. The power flow vectors are visualized to reveal the distribution of energy in the shell structures. Some useful conclusions are drown and helpful for the vibration control of plate and shell structures.

Vibrational Power Flow Analysis of Stiffened Plate and Shell Structures

Although Eulerian approaches are standard in computational acoustics, they are less effective for certain classes of problems like bubble acoustics and combustion noise. A different approach for solving acoustic problems is to compute with individual particles following particle motion. In this paper, a Lagrangian approach to model sound propagation in moving fluid is presented and implemented numerically, using three meshfree methods to solve the Lagrangian acoustic perturbation equations (LAPE) in the time domain. The LAPE split the fluid dynamic equations into a set of hydrodynamic equations for the motion of fluid particles and perturbation equations for the acoustic quantities corresponding to each fluid particle. Then, three meshfree methods, the smoothed particle hydrodynamics (SPH) method, the corrective smoothed particle (CSP) method, and the generalized finite difference (GFD) method, are introduced to solve the LAPE and the linearized LAPE (LLAPE). The SPH and CSP methods are widely used meshfree methods, while the GFD method based on the Taylor series expansion can be easily extended to higher orders. Applications to modeling sound propagation in steady or unsteady fluids in motion are outlined, treating a number of different cases in one and two space dimensions. A comparison of the LAPE and the LLAPE using the three meshfree methods is also presented. The Lagrangian approach shows good agreement with exact solutions. The comparison indicates that the CSP and GFD method exhibit convergence in cases with different background flow. The GFD method is more accurate, while the CSP method can handle higher Courant numbers.

https://www.preprints.org/manuscript/201701.0115/v1/download

Tian Yun Li

Papers

The Vibro-Acoustic Characteristics of the Cylindrical Shell Partially Submerged in the Fluid

Flow-Induced Noise Simulation Based on LES/Lighthill Hybrid Method

Vibration Isolation Characteristics of Euler Strut Spring Used in Low Frequency Vibration Isolation System

Vibrational Power Flow Analysis of Stiffened Plate and Shell Structures

A Lagrangian Approach for Computational Acoustics with Meshfree Method