V Notch Water Flow Measurement

For a triangular or v notch weir the flow rate can be expressed as.

V notch water flow measurement.

Head h should be measured at a distance of at least 4h upstream of the weir. When water flows through some open channel then sometimes it is required to find the flow rate occurring through the channel. The triangular or v notch thin plate weir is an accurate flow measuring device particularly suited for small flows. In other words a weir is essentially a partial dam.

Skrenter r instrumentation handbook water and wastewater treatment plants astm d 5242 92 2001. Sharp crested weir background. A weir as defined in the usbr measurement manual is simply an overflow structure built perpendicular to an open channel axis to measure the rate of flow of water. Thicker than this the nappe may collapse against the downstream face of the weir due to insufficient aeration causing the weir to under indicate the actual flow rate.

Standard test method for open channel flow measurement of water with thin plate weirs nappe may cling to downstream weir face 90º v notch weir discharge table 2 5 accuracy channel floor 3 5 hmax hmax weir pool point of measurement. To find the flow rate through o. V notch and flow meters reference products codes. Qv qvml qvliv p252q water flow monitoring in open channels is widely employed in environmental and geotechnical field.

Leakage measurement is one of the most important indicator of the overall performance of earth rock fill and concrete dams. Q 8 15 c d 2 g 1 2 tan θ 2 h 5 2 2 where. It is used to meter flow of water in the channel by measuring the head of water over the v notch crest. θ v notch angle.

Water flow monitoring in open channels is widely employed in environmental and geotechnical field. Leakage measurement is one of the most important indicator of the overall performance of earth rock fill and concrete dam. It works by raising the water level upstream of the weir and then forcing the water to spill over. Go to the left column then come down the left column till you reach 60 then across to the right to the 5 column your now at 60 5 65.

Quick ref table for v notch weir 0 to 125 l s53ov height above cease to flow point in mm discharge in l s litres per second if the water level when measured is say 65mm above the cease to flow level. It doesn t matter how thick the weir is except where water flows over the weir through the v the weir should be between 0 03 and 0 08 inches 0 8 to 2 mm thick in the v. Usbr 1997 suggests using the v notch weir equations for the following conditions. The v notch weir is especially good for measuring a low flow rate because the flow area decreases rapidly as the head over the v notch gets small.