RSS-2-300W User Manual
31
RSS-2-300W Non-Contact Surface Velocity Radar
9
9. Calculating Discharge from
Flow Velocity
Geolux RSS-2-300W surface velocity radar measures flow velocity at the water surface. This
measurement can be used to calculate actual discharge – the total volume of water that passes
through a channel cross-section in a specific period of time. Discharge measurement is important
for a wide variety of purposes including flood and pollution control, irrigation, watercourse
regulations and broadly as an input data for dimensioning of almost any new structure on the open
channel flows.
Discharge is calculated by multiplying mean flow velocity and channel cross-section area. The
cross-section area is the area of the slice in the water column made perpendicular to the flow
direction.
Let us assume a rectangular channel profile, with constant flow velocity at all points, as seen in
Picture 10.
Picture 10. Simple Channel Diagram
Q = V * A
where Q is discharge (for example in m3/s), V is flow velocity (for example in m/s), and A is cross-
section area (for example in m2).
For real-world measurements it is important to understand that the velocity of the moving water
varies both across the stream channel and from the surface to the bottom of the stream due to
friction, as in Picture11.
Picture11. Flow Velocity in a Typical Cross-Section
Summary of Contents for RSS-2-300W
Page 41: ...2021 ...