Variance of discharge estimates sampled using acoustic Doppler current profilers from moving platforms

GARCÍA, C.M.; TARRAB, L.; OBERG, K.,; SZUPIANY, R.N.; CANTERO, M.I.

JOURNAL OF HYDRAULIC ENGINEERING

ASCE-AMER SOC CIVIL ENGINEERS

Año: 2012 vol. 138 p. 684 - 694

0733-9429

This  paper  presents  a  model  for  quantifying  the  random  errors  (i.e.,  variance)  of  acoustic Doppler  current  profiler  (ADCP)  discharge  measurements  from  moving  platforms  associated with different sampling times. The model focuses on the random processes in the sampled flow field  and  has  been  developed  using  statistical  methods  currently  available  for  uncertainty analysis  of  velocity  time  series.  Analysis  of  field  data  collected  using  ADCP  from  moving platforms from three natural rivers of varying sizes and flow conditions shows that, even though the  estimate  of  the  integral  time  scale  of  the  actual  turbulent  flow  field  is  larger  than  the sampling  interval,  the  integral  time  scale  of  the  sampled  flow  field  is  on  the  order  of  the sampling interval. Thus, an equation for computing the variance error in discharge measurements associated  with  different  sampling  times,  assuming  uncorrelated  flow  fields  is  appropriate. The approach  is  used  to  help  define  optimal  sampling  strategies  by  choosing  the  exposure  time required for ADCPs to accurately measure flow discharg