Discharge Characteristics of V-shaped Multi-slit Weirs PDF Download

Author: Kai Ji
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Languages : en
Pages : 0

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Book Description
V-shaped weirs with small angles are efficient in accurately measuring extremely small discharge rates. The concept of slit weirs to measure discharge rates has been studied in recent investigations. Rectangular multi-slit notches or weirs have been shown to extend the range of flow measurement to include both very low and high discharge rates. It is a well-known fact that V-notches whose sections are narrower at lower heads are preferred to rectangular notches to measure small discharge rates in laboratories. To increase the range of discharges measured, the concept of multi-slit weirs using rectangular weirs has been introduced recently. For rectangular multi-slit weirs, experimental data showed that the discharge coefficient C d for multi-slit weirs or a single weir was a function of the Reynolds number R e when R e is based on the width of rectangular weirs. V-notches are generally used for laboratory flow measurements, as they can very precisely measure discharge rates. Hence, the multi-slit weirs formed by V-notches are expected to measure discharges in a very wide range of discharge rates. To represent a common discharge coefficient C d for multi-slit weirs formed of either rectangular or triangular shaped individual weirs, a new Reynolds number R eR is proposed to unify representation of discharge coefficient data for both rectangular shaped and V-shaped multi-slit weir units. C d data for both rectangular and V-shaped multi-slit weirs fall on a single curve and appear to be the function of R eR . At large Reynolds number, R eR, the discharge coefficient C d approaches a constant value of 0.61. This constant also denotes the contraction coefficient for the narrow two-dimensional slit flow. Present test data show that C d for multi-slit V-shaped weirs is generally a function of R eR for b/B