Direct Scaling of Measure on Vortex Shedding through a Flapping Flag Device in the Open Channel around a Cylinder at Re∼103: Taylor's Law Approach.

Giuseppe Roberto Tomasicchio,Massimo De Vittorio,Andrea Notaro,Samuele De Bartolo,Francesco Guido,Elisa Leone,Vincenzo Mariano Mastronardi,Antonio Francone

doi:10.3390/s21051871

Abstract

The problem of vortex shedding, which occurs when an obstacle is placed in a regular flow, is governed by Reynolds and Strouhal numbers, known by dimensional analysis. The present work aims to propose a thin films-based device, consisting of an elastic piezoelectric flapping flag clamped at one end, in order to determine the frequency of vortex shedding downstream an obstacle for a flow field at Reynolds number in the open channel. For these values, Strouhal number obtained in such way is in accordance with the results known in literature. Moreover, the development of the voltage over time, generated by the flapping flag under the load due to flow field, shows a highly fluctuating behavior and satisfies Taylor’s law, observed in several complex systems. This provided useful information about the flow field through the constitutive law of the device.

Highlights

IntroductionThe development of fluid-dynamic measuring instruments has been steadily increasing
In the previous years, the development of fluid-dynamic measuring instruments has been steadily increasing
It is observed that these vortices are shed periodically, and the shedding frequency is proportional to the average flow velocity

Summary

Introduction

The development of fluid-dynamic measuring instruments has been steadily increasing. It is observed that these vortices are shed periodically, and the shedding frequency is proportional to the average flow velocity This suggests that the flow rate can be determined by generating vortices in the flow by placing an obstruction along the flow and measuring the shedding frequency [1]. The flow measurement devices that work on this principle are called vortex flowmeters. They consist of a sharp-edged bluff body (strut) placed in the flow that serves as the vortex generator, and a detector (such as a pressure transducer that records the oscillation in pressure) placed within a short distance downstream on the inner surface of the casing aiming to measure the shedding frequency.

Methods

Results

Conclusion