Abstract
A surface gravity wave obliquely incident on a sloping beach is broken near the beach and has a smooth surface further out. Viewed in the frame of reference of the transition from the smooth to the broken part, the flow is steady, and the wave is oblique to the free stream. By placing a suitably shaped obstacle in a flume operated at high Froude number, such a wave can be generated. Experiments in which a wave of 18 cm height was generated are described and the wave shape and some of its characteristics presented. In particular, the dividing stream surface separating that part of the flow which curls over into the break from the part that flows smoothly over the obstacle is discussed.Model surfboards can ride this wave unsupported, provided the correctly scaled weight loads them at the right centre-of-mass position. This makes it possible to determine the forces on the board without a balance. A comparison of the measured forces with estimates, particularly of the drag, indicate that viscous and surface-tension phenomena introduce only small scale effects in the Froude number modelling. While the results are not sufficiently accurate to draw definite conclusions about the effects of surf board shape, they indicate clearly that surf board flows may be modelled with quantitative success in the laboratory.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
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