In the physical model study of Stonecutters Island main pumping station of the Hong Kong Harbour Area Treatment Scheme (HATS), a key design consideration is the avoidance of strong vortices and pre-swirl in the approach flow-which could impair the efficiency of pump operation. A swirl meter has been successfully developed to measure the swirl angle in the pump suction pipes. The performance of the swirl meter is tested in a swirling pipe flow with known angular momentum. LDA measurements of flow velocity are carried out to verify the swirling flow pattern. The rotational speed of the swirl meter is shown to be linearly proportional to discharge and depends on the inlet vane angle and associated velocity profile. The predictions of the rotational speed are in excellent agreement with data over a wide range of vane angles and discharges.
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