h above the undisturbed water level h o the water can flow into the reservoir from pool 7 or it may be drawn through pipes from sump 21 in either case the level of the pool water is not noticeably reduced when the hydraulic head reaches the desired height h the butterfly valve is suddenly opened to admit atmospheric air into reservoir 3 so that the stored water is released and the energy of its downward flow is transformed into a surf wave we have had tests of the operation of our new surf pool design conducted to determine if it would function as desired the pool was built on a 1 10 scale was 5 m in length 50 cm wide and the reservoir projected about 70 cm out of the water suction was obtained from an industrial vacuum cleaner and a flap closing the top of the reservoir was manually opened when the desired head height was achieved a cross sectional sketch of the pool is shown in fig2 the depth l k of pool reservoir for these tests was 47 cm it should be noted that some of the symbols used in fig1 were used in reporting these test results but given different definitions in the tests in these tests h is the depth of the undisturbed water which was 25 cm the test model included a shutter 31 that could be vertically adjusted to different depths below the surface of the water in these tests the shutter projected into the water a distance s of 4 cm in the tests the.