Experimental investigation of flow behind a cube for moderate Reynolds numbers

TL;DR

This study experimentally investigates the wake behind a cube at moderate Reynolds numbers, identifying flow bifurcations and vorticity sources, and compares results with previous numerical simulations.

Contribution

It provides new experimental data on flow bifurcations and vorticity components behind a cube, validating and extending prior numerical findings.

Findings

Confirmed two flow bifurcations within Re 100-400.

Identified vorticity sources from cube corners and instability effects.

Compared experimental results with earlier numerical simulations.

Abstract

The wake behind a cube with a face normal to the flow was investigated experimentally in a water tunnel using laser induced fluorescence visualisation (LIF) and particle image velocimetry (PIV) techniques. Measurements were carried out for moderate Reynolds numbers between 100 and 400 and in this range a sequence of two flow bifurcations was confirmed. Values for both onsets were determined in the framework of Landau`s instability model. The measured longitudinal vorticity was separated into three components corresponding to each of the identified regimes. It was shown that the vorticity associated with a basic flow regime originates from corners of the bluff body, in contrast to the two other contributions which are related to instability effects. The present experimental results are compared with numerical simulation carried out earlier by Saha (Phys. Fluids, vol. 16, 2004, pp. 1630-1646).