The aspect of the flow around a circular cylinder in a free surface water flow

National Defense Academy of Japan, Department of Mechanical Engineering, 1-10-20 Hashirimizu, Yokosuka 239-8686, Japan

^* Corresponding author: yokoi@nda.ac.jp

Published online: 24 October 2022

Abstract

The purpose of this study is in collection of the basic data for development of the simple flow velocity measurement equipment. A 10mm diameter circular cylinder was inserted into the free surface stream, and investigation of the water surface height and the relationship of the flow velocity which creep up the circular cylinder surface were performed. The experiment performed in the closed circuit water channel apparatus (the range of stream velocity is 0.07 - 0.98m/s) and carried out image-processing measurement using the video recording apparatus. In the insertion depth of various circular cylinders, observation of the height which creeps up the circular cylinder when varying the flow velocity was carried out. As a result, it became clear that the height of the water surface which creeps up by the increase in the flow velocity increases. And it also became clear for the phenomenon not to be based on the insertion depth. It was obtained that measured rising height and the flow velocity is required from Bernouilli's equation using the value. In the measurement, it became clear that 5 or more times of the cylinder diameter are required for the required insertion depth.