Kyozo Suga

FUNDAMENTAL STUDY ON 3-D STRUCTURE IN ORGANIZED TURBULENT MOTION AT THE BOUNDARY OF BANK VEGETATION BY CONDITIONAL SAMPLING METHOD

Conditional sampling method was adapted to clarify the three 3-D structure in periodical large vortices at the boundary between a river flow and vegetation zone along the river has a strong upward flow. It was shown that an upward flow and downward flow occur at the both edges of the free shear layer and main flow zone, and their intensity amounts to 80% of the turbulence intensity lateral velocity component.

PLANNING OF FLOOD PLAIN ROADS AND BRIDGES IN UNDERDEVELOPED COUNTRIES FROM THE POINT OF VIEW OF RIVER DISASTER PREVENTION

In developing countries, elevated roads on embankments that cross flood plains and approach roads to bridges which thrust out into river channels are often seen. Such structures interfere with flood flow, causing scouring around piers and soil embankments. One possible solution to this problem would be the construction of bridges completely over flood plains or rivers; however, this is not entirely realistic due to limited financial conditions in the affected countries.When designing such roads and bridges, two facts must be taken into account: rivers are in their natural state (i, e., without flood control) and there is a high probability of floods occuring beyond a design flood discharge due to insufficient hydrological data. Design criteria in Japan cannot simply be applied to the local situation. In this paper, such problems actually occuring at individual locations are analyzed and feasible countermeasures are proposed from the point of view of river disaster prevention.

Fundamental Study on Flow Fields with Meandering Vegetated Zones on Alternate Sandbars

Laboratory experiments were performed to study the effects of meandering vegetation zone along alternate sandbars. It is shown that the flow structure consists of horizontal free sheer layer along vegetated zone and secondary currents in meandering flow. Momentum transfer due to turbulence and that due to secondary currents were compared, which indicates importance of the latter.