Prediction Of Wave Attenuation Research Articles

RECENT ADVANCES IN MODELING WAVE ATTENUATION BY VEGETATION

In the past decade, interest in wave attenuation by vegetation has increased considerably as coastal engineers and scientists search for sustainable solutions to mitigate the impacts of climate change and natural hazards. The interactions of surface weaves and natural vegetation span over a large range of scales, from turbulence and eddies at the vegetation stem scale to wave generation in vast inundated wetlands of hundreds of square miles under hurricane conditions. Restoring coastal wetlands and reducing flood risks of coastal communities require improved understanding and better predictive capability for wave attenuation over inundated coastal landscapes with vegetation. The objective of this paper is to present recent advances in multi-scale modeling of wave attenuation by wetland vegetation. Numerical modeling results ranging from vegetation-resolved large eddy simulation under idealized conditions to incorporating vegetation-induced drag forces into conservation laws of momentum and energy for engineering applications will be shown. Effects of vegetation flexibility and various wave theories on the prediction of wave attenuation and the choice of vegetation drag coefficients will be discussed.

Prediction of Wave Attenuation across Multiple Joints with an Improved Elastic Nonlinear Model

The study on nonlinear displacement discontinuity model has been investigated in the researches of normal incident wave attenuation across rock joints. But the studies were limited only on the effects of joint with single type deformation behavior, without considering the influence of different extent in model nonlinearity. The improved elastic nonlinear normal deformational model can descript the extent of nonlinearity quantitatively. Based on this model, a displacement discontinuity model for normally incident wave propagation across multiple parallel joints was established in an elastic half-space. Using one-dimensional wave equation characteristics method, the time-domain numerical difference scheme of transmitted particle velocity was proposed, making computational programs to obtain semi-numerical solutions, and transmission coefficients. Parameter studies were conducted to get an insight into the effects of number of joints and the extent of nonlinearity, the incident wave maximum amplitude on transmission coefficients and transmission energy rate, waveform distortion and delay time.

Considerations of the discontinuous deformation analysis on wave propagation problems

AbstractIn rock engineering, the damage criteria of the rock mass under dynamic loads are generally governed by the threshold values of wave amplitudes, such as the peak particle velocity and the peak particle acceleration. Therefore, the prediction of wave attenuation across fractured rock mass is important on assessing the stability and damage of rock mass under dynamic loads. This paper aims to investigate the applications of the discontinuous deformation analysis (DDA) for modeling wave propagation problems in rock mass. Parametric studies are carried out to obtain an insight into the influencing factors on the accuracy of wave propagations, in terms of the block size, the boundary condition and the incident wave frequency. The reflected and transmitted waves from the interface between two materials are also numerically simulated. To study the tensile failure induced by the reflected wave, the spalling phenomena are modeled under various loading frequencies. The numerical results show that the DDA is capable of modeling the wave propagation in jointed rock mass with a good accuracy. Copyright © 2009 John Wiley & Sons, Ltd.

Simulation of building drainage system operation under water conservation design criteria

The Water Supply (Water Fittings) Regulations 1999, introduced to encourage innovation and water conservation, will profoundly affect building drainage design. Reduced shower flows and washing machine volumes and 6/3 litre dual flush wc operation will lower through flows, while drop valve wc flushing will affect system operation. Design for water conservation will necessitate the prediction of wave attenuation and its impact on solids transport and, without the safety factor provided by higher throughflows, simulations will ensure efficient design for minimal solid deposition. A simulation employing the method of characteristics solution of the St Venant equations and empirical relationships between solids velocity and the surrounding flow conditions is presented to predict solids transport performance within networks specified by slope, diameter, material, and appliance distribution and discharge characteristics.

Comparison of long-wavelengthT-matrix multiple-scattering theory and size-dependent Maxwell-Garnett formula

Wave attenuation in a dielectric-in-dielectric composite is calculated using the long-wavelength T-matrix multiple-scattering theory and the size-dependent Maxwell–Garnett formula. Results obtained are first compared, and then followed by their comparisons with the experimental results and other theoretical results. An interesting observation made is that the size-dependent Maxwell–Garnett formula predicts monotonically increasing wave attenuation with increasing concentration of inclusions, whereas the computed results from the multiple-scattering theory and other formulas, together with the experimental results, indicate maximum wave attenuation at a certain concentration of inclusions. It is shown that the size-dependent Maxwell–Garnett formula gives good prediction of wave attenuation only up to inclusion concentration of about 2%, and the T-matrix multiple-scattering theory in the long-wavelength approximation gives good prediction of wave attenuation even beyond the inclusion concentration of 2%. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 1–4, 1999.