The experiments on the damage of gentle-slope sea dike were conducted by using the irregular waves.The gentle-slope dikes of 1/3, 1/4 and 1/5 slope were constructed at the shoreline and the offshore side .The mutual relationship between the damage of sea dike and the relative maximum scoring (hmax/Ho) in front of dike was sufficiently estimated from the result of experiments. In the case of l t/Lo=-0.2, as the value of slope angle increase, the value of hmax/Ho becomes large and damage of dike becomes early.On the other, in the case of l t/Lo=0.0, as the value of slope angle increase, the value of hmax/Ho becomes small, but the damage of dike did not occurs within the limits of these experiments.Damage proceeded in the order as follows:(1) vanishing of sands on the slope, (2) damage of foundation works, (3)piping of backfilling stones, (4) subsidence of armor unit. This damage process agreed well with the result of experiments by the regular waves.
Experiments on a saltwater flow running up over a trench are carried out on the basis of a flow-visualization technique to consider the local hydraulic characteristics of flows around the trench, which is necessary for maintaining or reproducing the function of trench as a habitat. The flow regime inside and outside the trench significantly depends on the aspect ratio of a opening length to a step height of trench. In case that the opening length of trench is shorter than the reattachment length, large eddy motions induced periodically inside the trench by the vortex shedding from the step. The eddies have direct effects upon momentum exchange through the trench-mouth, and reduce the magnitude of velocity inside the trench.
2 正会員 東北工業大学教授 都市マネジメント科 (宮城県仙台市太白区八木山香澄町 35-1) 3 正会員 東北工業大学助手 都市マネジメント科 (同上) Wind forces acting on a ship that harbors behind a big building is studied experimentally using an open channel instead of a wind tunnel. For the purpose of safety mooring, the effect of this wind force must be investigated sufficiently. The flow profile of 1/7 law are made in a channel by means of roughness set on floor. Then, a ship and a building of a fence or a warehouse are set in a flow. A ship is allowed sway only. Measurements show the following. The length of regurgitation area of a wake of fence is about double of that of a warehouse. When the position of ship is near the building behind, time-averaged wind forces on a ship are pulling forces and when a ship leaves from a building, wind forces change to pushing forces. As the distance between a ship and a building becomes large, time-averaged wind forces become large and fluctuating wind loads become large as well as ship motions do. In addition, in case of a fence, pushing forces of wind on a moored ship is found to be larger a little than on a ship fixed.
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