Abstract
When baffle-block-type stilling basins of hydraulic jump-type drops for irrigational canal were designed, drag coefficient CD' was an important factor. The baffle blocks left one or three blocks per row in the horizontal canal and examined drag coefficient CD' with a direct measurement of drag force among the low Froude number (Fr1=3.0-4.5) of the forced hydraulic jump.
The results of this study can be summarized as follows:
1) The related diagram of the flow surface profile classification with parameters that cosisted of φ(=hp/h1, hp=tail-water depth, h1 initial-water depth), (Bh/h1)/β(Bh=height of block, β=Bs/(Bω+Bs), Bs=space of each block, Bω, =wide of block), X0/h1 (X0=horizontal distance from the toe of the hydraulic jump to block), were obtained.
2) Drag force P became smaller as X0/h1 increased. Drag coefficient CD' became exponentially smaller as X0/h1 increased. The relation between drag coefficient CD' and X0/h1 processed with Fr1 with the experimented equation being obtained. And CD'cal.(obtained by a calculation) agreed closely with the CD'exp.(obtained by a direct measurement).
3) The relation between f (=coefficient of energyloss) and β, Bh/h1, X0/h1 were obtained by the experimental equations for the number of blocks (N=1 and N=3). Generally, f tends to increase as (Bh/h1/β on each X0/h1 increases and the rate of increase of f decreases as X0/h1 increases.
4) Tail-water depth of the hydraulic jump can be expressed by the following equation.
φ3-[{2-(1-β) (Bh/h1) CD'} Fr12+1]φ+2Fr12=0
The theoretical water-depth ratio derived from the equation of the tail-water depth, agreed closely with data obtained.
