scholarly journals NON-CONSERVATIVE WAVE INTERACTION WITH FIXED SEMI-IMMERSED RECTANGULAR STRUCTURES

1978 ◽  
Vol 1 (16) ◽  
pp. 133
Author(s):  
Robert B. Steimer ◽  
Charles K. Sollitt
Keyword(s):  
Wave Interaction ◽  
Wave Structure ◽  
Variable Structure ◽  
Dimensional Structure ◽  
Solution Technique ◽  
Vertical Force ◽  
Computationally Efficient ◽  
Reflection And Transmission ◽  
Single Wave ◽  
Transmission Coefficients

Previous attempts to analytically describe wave reflection and transmission at surface penetrating structures have neglected losses due to flow expansion, contraction, and skin drag along the structure boundaries (Black and Mei, 1970; Ijima, et al., 1972). The model described in this study includes these effects and allows for the inclusion of a dissipative medium such as rubble or closely spaced piles in the region beneath the structure. The problem of a fixed, two-dimensional structure in a train of monochromatic incident waves is modeled, as shown in Figure 1. The solution allows for 1) variable structure length and draft, 2) different depths in the regions fore, aft, and beneath the structure, 3) variable wave amplitude and period, and 4) turbulent and inertial damping in the region beneath the structure. An equivalent work technique is applied to linearize the damping beneath the structure, yielding a potential flow problem in all three regions. Amplitudes for the resulting series of eigenfunctions in each region are determined by matching pressure and horizontal mass flux at the region interfaces, orthogonalizing these expressions over the depth, and simultaneously solving the resulting equations to yield complex reflection and transmission coefficients. Complex horizontal and vertical force coefficients for the structure are also determined from the integrated Bernoulli equation. The solution technique is computationally efficient. In general, five modes in the eigen series provide satisfactory convergence for the various hydrodynamic parameters. Approximately six-tenths of a computer system second are required to solve for a single wave-structure condition. The results compare favorably with variational methods used by others.

Extension of forward modeling phase-screen code in isotropic and anisotropic media up to critical angle

Geophysics ◽  
2007 ◽  
Vol 72 (5) ◽  
pp. SM107-SM114 ◽  
Author(s):  
James C. White ◽  
Richard W. Hobbs
Keyword(s):  
Critical Angle ◽  
Model Space ◽  
Anisotropic Media ◽  
Forward Modeling ◽  
Phase Screen ◽  
Computationally Efficient ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Phase Corrections ◽  
Converted Phases

The computationally efficient phase-screen forward modeling technique is extended to allow investigation of nonnormal raypaths. The code is developed to accommodate all diffracted and converted phases up to critical angle, building on a geometric construction method. The new approach relies upon prescanning the model space to assess the complexity of each screen. The propagating wavefields are then divided as a function of horizontal wavenumber, and each subset is transformed to the spatial domain separately, carrying with it angular information. This allows both locally accurate 3D phase corrections and Zoeppritz reflection and transmission coefficients to be applied. The phase-screen code is further developed to handle simple anisotropic media. During phase-screen modeling, propagation is undertaken in the wavenumber domain where exact expressions for anisotropic phase velocities are available. Traveltimes and amplitude effects from a range of anisotropic shales are computed and compared with previous published results.

Propagation of Gravity Waves Past Multiple Bottom-Standing Barriers

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
D. Karmakar ◽  
C. Guedes Soares
Keyword(s):  
Gravity Waves ◽  
Water Waves ◽  
Wave Interaction ◽  
Offshore Structures ◽  
Least Square ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Edge Conditions ◽  
Linearized Theory ◽  
Flexible Barriers

The interaction of oblique surface gravity waves with multiple bottom-standing flexible porous breakwaters is analyzed based on the linearized theory of water waves. Using the method of eigenfunction expansion and the least square approximation, the wave propagation in the presence of single bottom-standing barriers is analyzed considering the upper edge to be: (i) free and (ii) moored, whereas the lower edge is considered to be clamped at the bottom. The wide-spacing approximation is used to analyze the wave interaction with multiple porous bottom-standing flexible barriers to understand the effect of the submerged flexible barriers as an effective breakwater. A brief comparison of both the upper edge conditions is carried out to analyze the effect of wave dissipation due to the presence of multiple barriers. The numerical results for the reflection and transmission coefficients along with the free surface vertical deflection are obtained for the case of two and three multiple bottom-standing barriers. The attenuation in the wave height due to the presence of porosity, change in barrier depth, and distance between the barriers are analyzed. The present study will be helpful in the analysis of proper functioning of porous bottom-standing barrier as an effective breakwater for the protection of offshore structures.

Identification of Adhesive Bond in A Multi-Layered Structure Via Sound Insulation Characterestics

2010 ◽  
Vol 26 (3) ◽  
pp. 363-372 ◽  
Author(s):  
S. Malakooti ◽  
N. Mohammadi ◽  
M. J. Mahjoob ◽  
K. Mohammadi
Keyword(s):  
Transmission Loss ◽  
Wave Interaction ◽  
Adhesive Bond ◽  
Sound Insulation ◽  
Solution Technique ◽  
Layered Plates ◽  
Adhesive Bonds ◽  
Transmission Coefficients ◽  
Time Harmonic ◽  
Experimental Values

AbstractIn this paper, adhesive bonds in multi-layered plates are identified based on experimental values of their sound insulation characteristics. An exact model based on two-dimensional elasticity theory is formulated. The problem is a time harmonic plane acoustic progressive wave interaction with an isotropic multi-layered infinite elastic plate with interlaminar bonding imperfections. The T-matrix solution technique, which involves a system global transfer matrix, is formed as the product of individual transfer matrices. This is accomplished by applying continuity of the displacement and stress components at the interfaces of neighboring layers along with the relevant boundary conditions at the left and right interfaces of the plate with the surrounding acoustic fluid (air). The resulting equations are then solved for the unknown plane wave reflection and transmission coefficients. The experimental values of sound transmission loss (TL) are measured by a modified B&K impedance tube. Results are presented for a double-layered (lead-steel) plate while the layers are bonded together with metal glue. The normal and transverse adhesive spring constants of the metal glue are then identified in an inverse manner. The agreement of experiments with the analytical TL values predicted for a new triple-layered plate (based on the identified bond properties) confirms the validity of the method.

Reflection and Transmission Coefficients of Plane Waves in Magnetoelectroelastic Layered Structures

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
J. Y. Chen ◽  
H. L. Chen ◽  
E. Pan
Keyword(s):  
Piezoelectric Materials ◽  
Plane Waves ◽  
Layered Structures ◽  
Organic Glass ◽  
Reflection And Transmission Coefficients ◽  
Material Structure ◽  
Layered System ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Novel Material

Reflection and transmission coefficients of plane waves with oblique incidence to a multilayered system of piezomagnetic and/or piezoelectric materials are investigated in this paper. The general Christoffel equation is derived from the coupled constitutive and balance equations, which is further employed to solve the elastic displacements and electric and magnetic potentials. Based on these solutions, the reflection and transmission coefficients in the corresponding layered structures are subsequently obtained by virtue of the propagator matrix method. Two layered examples are selected to verify and illustrate our solutions. One is the purely elastic layered system composed of aluminum and organic glass materials. The other layered system is composed of the novel magnetoelectroelastic material and the organic glass. Numerical results are presented to demonstrate the variation of the reflection and transmission coefficients with different incident angles, frequencies, and boundary conditions, which could be useful to nondestructive evaluation of this novel material structure based on wave propagations.

scholarly journals Propagation Characteristics of Oblique Incident Terahertz Wave in Nonuniform Dusty Plasma

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Yunhua Cao ◽  
Haiying Li ◽  
Zhe Wang ◽  
Zhensen Wu
Keyword(s):  
Dusty Plasma ◽  
Terahertz Wave ◽  
Dust Particles ◽  
Number Density ◽  
Propagation Characteristics ◽  
Absorption Coefficients ◽  
Reflection And Transmission ◽  
Transmission Coefficients ◽  
Propagation Matrix ◽  
Transmission And Absorption

Propagation characteristics of oblique incident terahertz wave from the nonuniform dusty plasma are studied using the propagation matrix method. Assuming that the electron density distribution of dusty plasma is parabolic model, variations of power reflection, transmission, and absorption coefficients with frequencies of the incident wave are calculated as the wave illuminates the nonuniform dusty plasma from different angles. The effects of incident angles, number density, and radius of the dust particles on propagation characteristics are discussed in detail. Numerical results show that the number density and radius of the dust particles have very little influences on reflection and transmission coefficients and have obvious effects on absorption coefficients. The terahertz wave has good penetrability in dusty plasma.

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