A low cost, automated, remote monitoring video system built on standard commercial off-the-shelf (COTS) components and implemented with open source software is presented. The system has been implemented in a coastal area to perform image acquisition and processing, generating statistical products and transferring the information from the fi eld to a central node where post-processing and data visualization are made available to the general public. The open structure of the software allows the user to implement new routines and modules appropriate to fi t specifi c needs as well as to adapt the system to study other dynamical processes where continuous observation is required. The software and image data base can be obtained as freeware.
A simple and efficient procedure to obtain the free surface deformation from particle image velocimetry images using basic mathematical and statistical tools is presented. The procedure provides high spatial resolution measurements of the wave profile captured in the digital images. The procedure was tested in a study of wave interaction with a submerged obstacle with satisfactory results. When the free surface is not evenly illuminated the procedure loses accuracy.
Bottom boundary layer effects on the linear wave propagation over mild slope bottoms are analyzed. A modified WKB approximation is presented including boundary layer effects. Within the boundary layer, two cases are considered: laminar (constant viscosity) and turbulent. Boundary layer effects are introduced by coupling the velocity inside the boundary layer to the irrotational velocity in the core region through the bottom boundary condition. This formulation properly accounts for the phase between near bed velocity and bed shear stress. The resulting differential equation for the energy conservation introduces a new term accounting for the energy losses due to the boundary layer effects.
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