SOME FLOW VISUALIZATION STUDIES AROUND AN OSCILLATING SQUARE CYLINDER

Purpose The paper aims to study the influence of rounded corners on the flow-induced oscillation of a square cylinder that is free to oscillate in two degrees of freedom. Design/methodology/approach The finite volume code in conjunction with the moving mesh scheme was implemented via a user-defined function to carry out the computations in two dimensions. The Reynolds number (Re) chosen for the present study is fixed at 100, and the frequency ratio, Fr = fs/fn (where fs is the vortex shedding frequency and fn is the natural frequency of cylinder) is used as a varying parameter. The computational model was validated for flow past a stationary cylinder with R/D = 0 and 0.5, and the results showed good agreement with the literature. Findings The aerodynamic characteristics, amplitude response, trajectories of cylinder motion and vortex shedding modes are obtained by conducting a series of simulations under different frequency ratios of the cylinder. It was found that the minimum transverse amplitude, drag force and lift force obtained for a naturally oscillating square cylinder are quite different when compared with a stationary and forced oscillating cylinder, where the maximum drag and lift forces were observed for a square cylinder and a minimum around R/D = 0.2 was observed. Originality/value The present work identified the significant effect of the varying frequency ratio and R/D on the VIV modes of the cylinder. It was observed that the cylinder wake exhibits the (2S) vortex shedding mode for R/D = 0 to 0.2 at all Fr, whereas the C (2S) mode appeared for R/D > 0.2 at Fr = 1.1.

Download Full-text

Interference Between a Square and a Circular Cylinder

Volume 1A: Symposia, Part 2 ◽

10.1115/ajkfluids2015-12677 ◽

2015 ◽

Author(s):

Nithin S. Kumar ◽

R. Ajith Kumar ◽

Jayalakshmi Mohan

Keyword(s):

Circular Cylinder ◽

Flow Visualization ◽

Shear Layer ◽

Flow Pattern ◽

Water Channel ◽

Flow Patterns ◽

Observation Time ◽

Square Cylinder ◽

Circulating Water ◽

Layer Flow

The flow visualization studies around a square cylinder (upstream) and a circular cylinder arranged in tandem configuration is studied experimentally to identify the interference flow patterns. Flow visualization studies are carried out in a re-circulating water channel. The investigations are carried out for tandem arrangement varying the center-to-center distance (L) between the cylinders; L/B ratio is varied from 1 to 5 where B is the characteristic length. Experiments were conduct at a Reynolds number of 2100 (based on B). The results are also obtained for two tandem square cylinder configuration. The flow patterns observed are: Alternate Shear Layer Reattachment with and without gap flow, Simultanous shear layer reattachment and detached shear layer flow pattern. The time of persistence (in percentage) for each flow pattern is estimated over a sufficiently long period of observation time to identify the most influential, predominant flow pattern. Though these patterns are identical for square-square and square-circular tandem configurations, their order of predominance is different for both the configurations.

Download Full-text

The Visual Observation of Vortex Shedding from an In-Line Forced Oscillating Square Cylinder with an Attack Angle of 45 degree

The proceedings of the JSME annual meeting ◽

10.1299/jsmemecjo.2003.2.0_363 ◽

2003 ◽

Vol 2003.2 (0) ◽

pp. 363-364

Author(s):

Yoshifumi YOKOI ◽

Susumu INAGAKI ◽

Toshinori TAMAI ◽

Shunnsuke HAMA ◽

Keiko HIRAO

Keyword(s):

Vortex Shedding ◽

Visual Observation ◽

Attack Angle ◽

Square Cylinder ◽

Oscillating Square Cylinder

Download Full-text