Discharge Estimation in An Adverse Slope Condition Using Entropy
Concept: An Experimental Analysis
Abstract
Flow measurement is critical in hydraulic engineering for developing and
managing water resources. The mean flow velocity and cross-sectional
flow area at the measurement location are two major metrics required for
discharge estimation. River bathymetric surveys or advanced technologies
such as the Acoustic Doppler Current Profiler (ADCP) might be used to
determine the cross-sectional area. The mean flow velocity can be
measured using different techniques depending on whether the
measurements are taken from a distance (non-contact) or a contact method
(traditional approach). Non-contact velocity measuring techniques are
becoming increasingly common in recent years since they are less
time-consuming and easier to utilize while dealing with heavy flows and
inclement weather. One such modern approach is the entropy-based
concepts (such as Shannon entropy, Tsallis entropy and Renyi entropy)
used to calculate the discharge from non-contact observations, yielding
superior results to classic approaches such as the velocity area method.
Entropy-based velocity distribution depends on the crucial parameter
called entropy parameter (a function of the ratio of the mean and
maximum velocity), which is linked to the channel and flow
characteristics. Its value is surmised to be constant for a particular
river reach. Due to this fact, the entropy-based approach was used in
this study to evaluate the discharge in case of the adverse bed slope
condition that may arise due to several reasons, and one among them is
the excessive mining in the particular river reach. This study collected
the experimental velocity data for the mild, horizontal and adverse bed
slope conditions from a rectangular flume fitted with a mechanical
apparatus to change the bed slope. Results concluded that the mild and
horizontal slope conditions depicted only a slight variation in entropy
parameter value, i.e., almost constant. The same was adopted for finding
the mean velocity for the adverse bed slope condition to calculate the
discharge. Furthermore, the discharge error analysis presented a
substantial justification for the utilized single constant value of the
entropy parameter for the whole cross-section, and the same can be
employed for future explorations on the same channel stretch.