Modeling of the acoustic waves propagation in non-homogeneous medium

Research and development in WaterSide Security (WSS) are being carried out in many countries around the World. However, the R & D activities are frequently scattered and uncoordinated from country to country. Therefore, there is still a strong need for a better coordination of development of equipment and procedures for WSS and for exchange of most recent research results in order to obtain a world-wide view over the state-of-the-art in technologies and their applications. To meet this need several conferences have been held over the past decade ranging from its early start in Poland and via 3 international conferences on WaterSide Security held in 2008, 2010 and 2012, to the situation of today. This presentation will comprise an exposition on criminality at sea and its abatement today with a concentration on terror and piracy. What have we learned and what can we do

Acoustic Propagation Through Bubbles: An Exploration of the 1st and 2nd Moments in Various Flow Conditions

The classic theory for the propagation of acoustic waves in bubbly fluids, which is the 1st moment of the multiple scattering solution, is well known. An integral equation describing the 2nd moment can also be formulated using the multiple scattering approach, although solutions to this equation are difficult and typically require approximations. In this paper, the multiple scattering approach is used to derive a solution to the 2nd moment in a slightly different fashion. This is done by first considering the solution to the 2nd moment for the single scatterers only, following with the solution for the double scatterers, and eventually generalizing to the complete solution. The solutions to both the 1st and 2nd moments require no knowledge of any flow parameters, although they do require averaging over all bubble configurations. The time required for enough bubble configurations to be observed forms the basis for an indirect link between the multiple scattering theory and the flow. This relationship between the statistics of the propagation through bubbles and the flow in which the bubbles exist is explored in a laboratory environment. Multi-frequency attenuation measurements are inverted to estimate the bubble population distribution, which in turn is used to predict the 2nd moment. The predicted 2nd moment is then compared to the measured 2nd moment. The time scales associated with the convergence of the measurements to the prediction is then estimated for the flow conditions investigated, providing an estimate of the mixing time of the flow. Although these time scales are specific to the laboratory studies described herein, it is hoped that they will serve to help illustrate the relationship between the multiple scattering theory of bubbles and the flow in which they reside. Read More: http://www.worldscientific.com/doi/abs/10.1142/9789812702609_004