Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
ANALYSIS OF THE FREE END FLOW ON THE BISTABILITY PHENOMENON AFTER TWO SIDE BY SIDE FINITE CYLINDER WITH MID ASPECT RATIO
Submission Author:
Marcos Woyciekoski , RS , Brazil
Co-Authors:
Marcos Woyciekoski, Jeferson Diehl de Oliveira, Roberta Fatima Neumeister, Sergio Viçosa Möller
Presenter: Jeferson Diehl de Oliveira
doi://10.26678/ABCM.COBEM2023.COB2023-0916
Abstract
For the purpose of studying the impact of three-dimensional flow on the bistable flow, several flow visualization experiments were conducted around a cylinder with a finite height. The free ends of the cylinder induced a three-dimensional flow which influenced the flow pattern along the height of the cylinder. The bistable phenomenon, in which the flow forms two wakes behind the cylinders (a large wake behind one cylinder and a narrow wake after the other), can occur in circular cylinders placed side by side, and is relevant in many practical engineering situations. This phenomenon results in a flip-flopping wake with a polarized flow that changes at irregular intervals. This can lead to additional sources of dynamic instabilities in the flow. However, the bistable phenomenon in finite cylinders is still not fully understood. In some cases where the bistable phenomenon can occur in infinite cylinders, it may not occur in finite cylinders due to downwash flow from the free end. To address this issue, an experimental study was conducted in a wind tunnel using hot wire anemometry techniques to analyze the flow around circular finite cylinders with a diameter of 0.032 m arranged side by side with aspect ratio 4 and spacing ratio p/d = 1.26. Then, an experimental study with dry ice in a wind tunnel were used to visualize the flow around circular finite cylinders with the same diameter. The vortex shedding frequency is obtained through the auto spectral density function, using hot wire anemometry. The velocity fluctuations in an aerodynamic channel were measured using the hot wire anemometry technique, and the results were compared with those obtained using the dry ice flow visualization technique. The experimental data from the aerodynamic channel were analyzed using statistical tools, spectral and wavelet analysis. The results of the experiment confirmed the occurrence of the bistable phenomenon in the configuration of finite cylinders with aspect ratio 4.
Keywords
Turbulent flow, hot wire anemometry, aspect ratio
