there are different methods to reduce drag in high speed hulls. one of these methods is a change in the shape of the body by adding longitudinal side tunnels. in this paper it has been attempted to determine the influence of the tunnel height on hydrodynamic characteristics of the hull to achieving an optimum shape for the tunnel. to achieve this purpose, numerical simulation of the problem has...

efflux time measurements are carried out for gravity draining of a liquid from a large cylindrical tank (where the flow is essentially laminar) through single exit pipe in the absence and presence of cetyl pyridinium chloride (cpc) surfactant solutions. the variables considered are initial height of liquid in the tank, dia. of tank, length of the exit pipe and concentration of surfactant. the d...

This paper numerically investigates the resistance at full-scale of a zero-emission, high-speed catamaran in both deep and shallow water, with Froude number ranging from 0.2 to 0.8. The numerical methods are validated by two means: (a) Comparison available model tests; (b) blind validation using different flow solvers. resistance, sinkage, trim catamaran, as well wave pattern, longitudinal cuts...

The Mesoscale Alpine Programme (MAP) was conducted over the European Alps in September-November 1999. During autumn, heavy rains and floods can occur when baroclinic troughs move over the region, and moist air flows from the Mediterranean Sea toward the southern Alps. Dual-polarimetric Doppler and vertically pointing radar data collected during MAP on the Mediterranean side of the Alps provided...

Snow avalanches and other hazardous geophysical granular flows, such as debris flows, lahars and pyroclastic flows, often impact on obstacles as they flow down a slope, generating rapid changes in the flow height and velocity in their vicinity. It is important to understand how a granular material flows around such obstacles to improve the design of deflecting and catching dams, and to correctl...

Over a large range of Rossby and Froude numbers, we investigate the dynamics of initially balanced decaying turbulence in a shallow rotating fluid layer. As in the case of incompressible two-dimensional decaying turbulence, coherent vortex structures spontaneously emerge from the initially random flow. However, owing to the presence of a free surface, a wealth of new phenomena appear in the sha...