Measurements for Water: Discharge streamflow

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  • 1. Measurements for waterA.M.J. CoendersWaterbalans: Discharge streamflow
  • 2. Discharge & Streamflow measurements-Point velocity & velocity area method A n Q = ∫ u ⋅ dA ≈ ∑ u i ⋅ ∆Ai • Three point measurement (measured away from the water surface): u = 1 / 3{u 0.2 + u 0.6 + u 0.8 } or u = 1 / 4{u 0.2 + 2 ⋅ u 0.6 + u 0.8 }
  • 3. Figure 5.4: Influence number ofFigure 5.3: Influence number of points in the vertical verticals in the cross-section
  • 4. Pendulum FNtan ϕbody = hence G FN = C N ⋅ 1 / 2 ⋅ ρ ⋅ u 2 ⋅ A 2u = coefficient ⋅ tan ϕ body ϕbody G
  • 5. Cub and propeller current meterCub propellor
  • 6. Wading
  • 7. Cable way
  • 8. Bridge support
  • 9. Electromagnetic streamflow U = K x B x vwater x L
  • 10. Electromagnetic streamflow measurements (pipe flow) U *L Q=K* B
  • 11. Schematic view of electromagnetic gauge with coil installed below channel bed
  • 12. Acoustic Doppler Current Profiler ADCP The principles of doppler v F =F ⋅ d s c Fd is the Doppler shift frequency Fs is the frequency of the sound under stagnant condition v is the relative velocity between the sound source and the sound receiver [m/s] c is the speed of sound [m/s] detected frequency increases for objects moving toward the observerin water: v Transmitting and receiving: Fd = 2 ⋅ Fs ⋅ c Component parallel to flow: v Fd = 2 ⋅ Fs ⋅ ⋅ cos A c
  • 13. ADCPPro’s:-continuous-almost complete vertical-velocity in 3-dimensionsCons:-Deep water-Expensive, trained personnel
  • 14. Floats:
  • 15. Floats:Scheldt fieldwork, tidal movement
  • 16. Integrating rising bubble techniqueD vw L D T= = v w vr q = v w D = vr L Q = vr A
  • 17. •Integrating rising•bubble technique L
  • 18. L