Wind chime Japanese glass wind bells known as "fūrin" () have been produced since the Edo period, and those at Mizusawa Station are one of the 100 Soundscapes of Japan. Wind chimes are thought to be good luck in parts of Asia and are used in Feng Shui. Wind chimes started to become modernized around 1100 B.C. after the Chinese began to cast bells. A bell without a clapper, called a "yong-zhong", was crafted by skilled metal artisans and primarily used in religious ceremonies. Afterwards, the Chinese created the "feng-ling", which is similar to today's modern wind bell. Feng-lings were hung from
Wind gradient the blades nearest to the ground level compared to those at the top of blade travel, and this in turn affects the turbine operation. The wind gradient can create a large bending moment in the shaft of a two bladed turbine when the blades are vertical. The reduced wind gradient over water means shorter and less expensive wind turbine towers can be used in shallow seas. It would be preferable for wind turbines to be tested in a wind tunnel simulating the wind gradient that they will eventually see, but this is rarely done. For wind turbine engineering, a polynomial