The crest height complies with the certain minimum value. The weirs under this category are; round nose horizontal broad crested weir, rectangular broad crested weir, Romign measuring and regulating weir, trapezoidal profile weir, Fayoum standard weir and V-shaped broad crested weir.
The length of the crest is 1 to 2 mm, for this reason they are also called thin plate weirs. The nape is free from weir body after passing the weir, and the streamline above the crest are strongly curved. The atmospheric pressure should prevail in the air filled area below the underside of the out flowing jet. Amongst these weirs are; horizontal sharp crested weir, rectangular sharp crested weir, V-shaped sharp crested weir, trapezoidal sharp crested weir, circular sharp crested weir and proportional weir (Sutro weir).
They look like broad crested and sharp crested weirs. The streamline along the crest is curved. These include; weir still with rectangular control section, V-notch weir still, triangular profile weir, flat V-weir butchers movable standing wave weir, Wes- standard spill ways, cylindrical crested weir, streamlined triangular profile weir, flap gates and Rossum weir.
Application and Importance of weirs ...