Abstract
In this research, we first show the actual flow rate differences due to the difference in observation method in real observation about the observed flow velocity. Based on the results, we classified the flow velocities for each observation method and derived a new theory about these relationships. Numerical calculations were carried out to verify the theory and quantitatively evaluate.
In the past, the standard high-water level river discharge measurement method in Japan had been the float method. However, recently measurement methods using doppler radar or image processing had been seriously studied and been applied to practical river discharge measurement. Until now a lot of studies had been done on the accuracy of these measurement methods, but few focus on what kind of velocity (the discharge are usually calculated by the velocity and cross-section area) has been measured. Because there is more than one definition of velocity to describe river flow. The result can be quite different when measuring the different kind of velocity
In the present study, we will firstly show that the discharge which been measured by different measurement method are actually different. Based on the result, we will study which kind of velocity and discharge have been measured by the popular measurement methods. We had also studied the relation between different kinds of velocity both theoretically and numerically. As the result, the numerical experiment agree with the theory very well. The observation based on Euler's definition of velocity shows a bigger value than the observation based on lagrange's definition of velocity.
