Transition to Turbulence in the Wake of a Circular Cylinder
Steady incoming flow past a slender bluff body is one of the most classical problems in fluid mechanics. In addition to its fundamental significance, this scenario also has various practical applications involving bluff bodies such as offshore platforms and subsea pipelines. In this project, the transition to turbulence in the wake of a circular/square cylinder has been investigated through direct numerical simulations (DNS) and large eddy simulations (LES). Specifically, two main topics have been studied: (i) the transition to turbulence in the wake of a circular cylinder at a Reynolds number of 3900, and (ii) the wake transition of an inclined square cylinder, where the difference to a circular or a square cylinder is investigated. A comprehensive understanding of the turbulent wake of a circular cylinder will guide the practical design of subsea pipelines, cables, risers, etc., which is beneficial to Australia's oil and gas industry.
Area of science
Systems used
Magnus and Zeus
Applications used
The Challenge
Three-dimensional DNS and LES are routinely used to investigate the transient and unstable wakes of a circular/square cylinder. High-quality 3D DNS and LES, especially for flows with relatively high Reynolds numbers, are extremely time-consuming. High computational mesh resolution and long integration time for the flow are necessary to capture the flow characteristics. Even by using the supercomputers, this would require a significant amount of computational time. For example, the computational cost for a typical OpenFOAM case (at Reynolds number of 1000) on a Cray XC40 supercomputer Magnus up to ~ 400 vortex shedding cycles is ~ 50,000 core hours.
The Solution
The resources provided by the Pawsey Supercomputing Centre enabled the expensive 3D numerical simulations to be carried out. In particular, the use of Magnus allows large-scale simulations to be carried out with highly parallelised computation (~ 200 – 500 cores).
The Outcome
The resources provided by the Pawsey Supercomputing Centre enabled the expensive 3D numerical simulations to be carried out. In particular, the use of Magnus allows large-scale simulations to be carried out with highly parallelised computation (~ 200 – 500 cores). By analysing the simulated data, a number of flow characteristics have been revealed and the underlying physical mechanisms have been unveiled.
Four high-quality journal papers have been published in 2019 and early 2020 based on this project, with the acknowledgement of the Pawsey Supercomputing resources.
List of Publications
Jiang, H., 2020. Separation angle for flow past a circular cylinder in the subcritical regime. Physics of Fluids 32, 014106.
2. Jiang, H., Cheng, L., 2020. Flow separation around a square cylinder at low to moderate Reynolds numbers. Physics of Fluids (in press).
3. Jiang, H., Cheng, L., 2020. Transition to chaos in the cylinder wake through the Mode C flow. Physics of Fluids 32, 014103.
4. Jiang, H., Cheng, L., 2019. Transition to the secondary vortex street in the wake of a circular cylinder. Journal of Fluid Mechanics 867, 691–722.
