Underwater Acoustic Absorption of Composite Anechoic Layers With Inner Holes

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Changzheng Ye ◽  
Xuewei Liu ◽  
Fengxian Xin ◽  
Tian Jian Lu
Keyword(s):  
Theoretical Model ◽  
Material Properties ◽  
High Performance ◽  
Numerical Study ◽  
High Order Mode ◽  
Variable Cross Section ◽  
Geometrical Parameters ◽  
Variable Cross ◽  
Underwater Acoustic ◽  
Rubber Layer

A combined theoretical and numerical study is carried out to quantify the influence of material properties (e.g., real part and loss factor of Young’s modulus, material density) and geometrical parameters (e.g., layer thickness, height of hole) on the sound absorption performance of an underwater rubber layer containing periodically distributed axial holes. A theoretical model is developed based on the method of transfer matrix as well as the concept of equivalent layering of holes with variable cross section. Numerical simulations with the method of finite elements are subsequently carried out to validate the theoretical model, with good agreement achieved. Physical mechanisms underlying the enhanced acoustic performance of the anechoic layer as a result of introducing the periodic holes are explored in terms of the generated transverse waves and the high-order mode of vibration. The results presented are helpful for designing high-performance underwater acoustic layers with periodically distributed cavities by tailoring relevant material properties and geometrical parameters.

Boundary element method in numerical study of three-dimensional Stokes flows in channels of arbitrary shape

2012 ◽  
Vol 9 (1) ◽  
pp. 94-97
Author(s):  
Yu.A. Itkulova
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Cross Section ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cylindrical Tube ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Periodic Flows ◽  
Element Method

In the present work creeping three-dimensional flows of a viscous liquid in a cylindrical tube and a channel of variable cross-section are studied. A qualitative triangulation of the surface of a cylindrical tube, a smoothed and experimental channel of a variable cross section is constructed. The problem is solved numerically using boundary element method in several modifications for a periodic and non-periodic flows. The obtained numerical results are compared with the analytical solution for the Poiseuille flow.

Numerical Study on the Heat Transfer Characteristic in Periodical Variable Cross-Section Channel

2011 ◽  
Vol 243-249 ◽  
pp. 4935-4938
Author(s):  
Li Li ◽  
Xiao Ze Du
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Section ◽  
Heat Transfer Characteristic ◽  
Numerical Study ◽  
Transfer Characteristic ◽  
Variable Cross Section ◽  
Central Line ◽  
Large Reynolds Number ◽  
Variable Cross

The heat transfer characteristic through periodical variable cross-section passage is studied with numerical scheme. The results in multi-period variable cross-section channel show that the heat transfer enhancement can be obtained by forming flow destabilization at large Reynolds number. The parameters include pressure, velocity, temperature in the channel are symmetric about central line at low Reynolds number, then change to asymmetric at high Reynolds number. The variations occur firstly at the downstream near outlet of the channel and move upstream, which could improve the fluid mixing to increase the enhancement of heat transfer in channel.

scholarly journals Experimental and analytical studies to substantiate the blasting operations rational parameters in the hard media destruction

2019 ◽  
Vol 109 ◽  
pp. 00040
Author(s):  
Ihor Kratkovskyi ◽  
Oleksii Ishchenko
Keyword(s):  
Fractional Composition ◽  
Variable Cross Section ◽  
Cumulative Distribution ◽  
Geometrical Parameters ◽  
Sieve Analysis ◽  
Variable Cross ◽  
Composition Distribution ◽  
Explosive Charges ◽  
Regression Correlation ◽  
Explosive Destruction

The method of sieve analysis studied particle size distribution of the products explosive destruction of sand-cement models with elliptical compensatory cavity in its middle that were destroyed with use of various designs explosive charges and built the cumulative distribution curves. It was established that the area of the newly formed surface of these models destruction products, destroyed by an explosion of variable cross section charges, increased 1.45 times as compared with charges of other structures (boiler in the extension of the charge end, solid structure). The middle diameter of particles increased at 50-60 %. According to the results of the fractional composition, distribution of the products models destruction for different designs and geometric parameters of the compensation cavity has been defined by the regression lines. According to the cumulative distribution curves of the products of destruction of a model with different geometrical parameters of the compensation cavity, around which various designs of explosive charges were exploded, the equations of the regression lines was determined. Based on the obtained dependences of the regression-correlation analysis, mathematical models have been developed to optimize the choice of rational parameters of compensation cavities and explosive charge structures. Recommendations for their use in mines are given.

scholarly journals Analysis of thin-walled beams with variable monosymmetric cross section by means of Legendre polynomials

2019 ◽  
Vol 41 (1) ◽  
pp. 1-12
Author(s):  
Józef Szybiński ◽  
Piotr Ruta
Keyword(s):  
Cross Section ◽  
Legendre Polynomials ◽  
Variable Cross Section ◽  
Free Vibrations ◽  
Variable Coefficients ◽  
Beam Axis ◽  
Geometrical Parameters ◽  
Beam Model ◽  
Variable Cross ◽  
Thin Walled

AbstractThis article deals with the vibrations of a nonprismatic thin-walled beam with an open cross section and any geometrical parameters. The thin-walled beam model presented in this article was described using the membrane shell theory, whilst the equations were derived based on the Vlasov theory assumptions. The model is a generalisation of the model presented by Wilde (1968) in ‘The torsion of thin-walled bars with variable cross-section’, Archives of Mechanics, 4, 20, pp. 431–443. The Hamilton principle was used to derive equations describing the vibrations of the beam. The equations were derived relative to an arbitrary rectilinear reference axis, taking into account the curving of the beam axis and the axis formed by the shear centres of the beam cross sections. In most works known to the present authors, the equations describing the nonprismatic thin-walled beam vibration problem do not take into account the effects stemming from the curving (the inclination of the walls of the thin-walledcross section towards to the beam axis) of the analysed systems. The recurrence algorithm described in Lewanowicz’s work (1976) ‘Construction of a recurrence relation of the lowest order for coefficients of the Gegenbauer series’, Applicationes Mathematicae, XV(3), pp. 345–396, was used to solve the derived equations with variable coefficients. The obtained solutions of the equations have the form of series relative to Legendre polynomials. A numerical example dealing with the free vibrations of the beam was solved to verify the model and the effectiveness of the presented solution method. The results were compared with the results yielded by finite elements method (FEM).

Application of the Three-Parameter Differential Model of Turbulence for Solving Problems of Flow and Heat Transfer in Channels of Variable Cross-Section. Part 2

2021 ◽  
Vol 12 (2) ◽  
pp. 89-106
Author(s):  
V. G. Lushchik ◽  
◽  
M. S. Makarova ◽  
A. I. Reshmin ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Numerical Study ◽  
Narrow Channel ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Differential Model ◽  
Heat Transfer Intensification ◽  
Flow And Heat Transfer ◽  
Shear Turbulence

A description of the method of numerical study in the approximation of a narrow channel of the problems of flow and heat transfer in flat and circular channels of variable cross-section using a differential three-parameter model of shear turbulence is presented. The main results of numerous studies using the proposed method are described, one of the goals of which was to substantiate the possibility of using the narrow channel approximation. This review study is carried out in two parts. In the second part the results of the study of laminarization during flow in the con-fuser and the pipe, heat transfer intensification during flow in diffusers and in a plate heat exchanger with diffuser channels are presented.

INTENSIFICATION AND STUDY OF HEAT TRANSFER AND FRICTION IN THE PLATE HEATING SURFACES OF THE KMS-2 AIR HEATER WITH A PRESSURE GRADIENT

2021 ◽  
Vol 11 (2) ◽  
pp. 23-29
Author(s):  
Nadezhda P. PETROVA ◽  
Anna A. TSYNAEVA ◽  
Valeriya V. BELAYA
Keyword(s):  
Heat Transfer ◽  
Pressure Gradient ◽  
Numerical Study ◽  
Initial Section ◽  
Variable Cross Section ◽  
Variable Pressure ◽  
Variable Cross ◽  
Average Value ◽  
Effi Ciency ◽  
Plate Heating

A numerical study of heat transfer and friction in the heat exchanger channels in the presence of a variable pressure gradient is performed. The research was carried out in software complexes (Code_Saturne, Salome). The results of the validation of the research method are presented and they showed that the deviation of the numerical simulation results from the calculation data according to the known criterion equations is within the error of generalization of the experimental data by the criterion equations. According to the results of studies at Red=3000, Red=4177, Red=6000, it was found that the average value of the heat transfer coeffi cient of the channel of variable cross-section is up to 20 % higher than for the channel at dp/dx0. At the same time, the thermal-hydraulic effi ciency of the alternating channel (L=117 mm, l=58.5 mm, n=2) in the initial section at x =0...0.08 is lower than in the channel with dp/dx>0 by 26.7 %, and at x =0.08...1 it is higher by 5 ... 15 %, at dp/dx

scholarly journals A Numerical Study on Structural Performance of Railway Sleepers Using Ultra High-Performance Concrete (UHPC)

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2979
Author(s):  
Moochul Shin ◽  
Younghoon Bae ◽  
Sukhoon Pyo
Keyword(s):  
Cross Section ◽  
High Performance ◽  
High Performance Concrete ◽  
Numerical Study ◽  
Structural Performance ◽  
Geometrical Parameters ◽  
Ultra High Performance Concrete ◽  
Direct Tension ◽  
Design Factor ◽  
The Cross

This numerical study investigates the structural performance of railway sleepers made of ultra high-performance concrete (UHPC). First, numerical concrete sleepers are developed, and the tensile stress-strain relationship obtained from the direct tension test on the UHPC coupons is used for the tensile constitutive model after applying a fiber orientation reduction factor. The numerical sleeper models are validated with the experimental data in terms of the force and crack-width relationship. Second, using the developed models, a parametric study is performed to investigate the performance of the UHPC sleepers while considering various design/mechanical/geometrical parameters: steel fiber contents, size of the cross-section, and diameter and strength of prestressing (PS) tendons. The simulation results indicate that the size of the cross-section has the most impacts on the performance, while the effect of yielding strengths of PS tendons is minimal among all the parameters. Engineers need to pay attention to efficiency and an economical factor when using a larger cross-section, since sleepers with larger cross-sections can be an over-designed sleeper. This study suggests an economical design factor for engineers to evaluate what combination of parameters would be economical designs.

scholarly journals Static, Vibration, and Transient Dynamic Analyses by Beam Element with Adaptive Displacement Interpolation Functions

2012 ◽  
Vol 2012 ◽  
pp. 1-25
Author(s):  
Shuang Li ◽  
Jinjun Hu ◽  
Changhai Zhai ◽  
Lili Xie
Keyword(s):  
Cross Section ◽  
Material Properties ◽  
Polynomial Interpolation ◽  
Mass Matrix ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Lumped Mass ◽  
Beam Elements ◽  
Dynamic Analyses ◽  
Interpolation Functions

An approach to analyzing structures by using beam elements is developed with adaptive displacement interpolation functions. First, the element stiffness matrix and equivalent nodal loads are derived on the basis of the equilibrium between nodal forces and section forces rather than the compatibility between nodal deformations and section deformations, which avoids discretization errors caused by the limitation of conventional polynomial interpolation functions. Then, six adaptive element displacement interpolation functions are derived and extended to include several cases, such as beams with variable cross-section, variable material properties, and many different steps in cross-section and/or material properties. To make the element usable in dynamic analyses, consistent mass matrix (CMM) and diagonally lumped mass matrix (LMM) are constructed using the presented adaptive displacement interpolation functions. All these features have made the element elegant, which is tested with a number of simple static, vibration, and dynamic examples to show its accuracy.

scholarly journals Numerical Study of Detonation Wave Propagation in the Variable Cross-Section Channel Using Unstructured Computational Grids

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Alexander Lopato ◽  
Pavel Utkin
Keyword(s):  
Detonation Wave ◽  
Cross Section ◽  
Large Scale ◽  
Numerical Study ◽  
Variable Cross Section ◽  
Approximation Order ◽  
Computational Grids ◽  
Detonation Waves ◽  
Variable Cross ◽  
Two Dimensional

The work is dedicated to the numerical study of detonation wave initiation and propagation in the variable cross-section axisymmetric channel filled with the model hydrogen-air mixture. The channel models the large-scale device for the utilization of worn-out tires. Mathematical model is based on two-dimensional axisymmetric Euler equations supplemented by global chemical kinetics model. The finite volume computational algorithm of the second approximation order for the calculation of two-dimensional flows with detonation waves on fully unstructured grids with triangular cells is developed. Three geometrical configurations of the channel are investigated, each with its own degree of the divergence of the conical part of the channel from the point of view of the pressure from the detonation wave on the end wall of the channel. The problem in consideration relates to the problem of waste recycling in the devices based on the detonation combustion of the fuel.

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