A study on performances of an uneven dual-screen windbreak near a cliff edge against typhoon attacks

摘要

Performance of the uneven dual-screen windbreak (UDSW) to protect agricultural products from the strong wind was tested when the typhoon 0310 attacked Okinawa. The test area surrounded by the UDSW is located on a plateau near a cliff. Wind speed was measured by ultrasonic anemometers at 6m high from the ground outside of the test area and 3m and 6m high inside. The relations between the distance from the cliff edge and the average wind speed were indicated a quadratic function of the distance in the range of 400m from the edge. These calculated data by a quadratic function were compared with the measured data. The wind speed at 28m leeward from the UDSW was reduced by 25% at a height of 6m, and that at 90m leeward was reduced by 17%. The wind speed ratio at a height of 3m to 6m was increased with distance from the UDSW about 0.83 to 0.92.