Computational Modelling Group

Assessment of the performance of novel RANS and hybrid turbulence models on the flow around a cylinder

Started
4th October 2013
Ended
20th September 2013
Research Team
Manuel Diaz Brito

Iso-contour Q = 1 [1/s]

The turbulent flow around a circular cylinder is a widely studied problem in fluid dynamics. At a certain characteristic Reynolds numbers the development of a turbulent wake occurs simultaneously with separation of the laminar boundary layer. The mechanisms defining this critical flow state are very complex to predict computationally. In this project the suitability of novel non-linear eddy viscosity closures and a hybrid Flow Simulation Methodology formulation to face these massively separated flows is studied. The flow predicting capabilities of the baseline EASM, φ-α-EASM and FSM-φ-α-EASM tested are contrasted with the industrial renowned k-ω-SST turbulence model. In the visualisation of the results it is evident that the φ-α-EASM has greater flexibility estimating the components of the Reynolds stresses with respect to the baseline EASM and the k-ω-SST. Although dome differences are observed, the prediction of the critical flow around a cylinder is not accurately achieved by any of these RANS models, but the FSM-φ-α-EASM shows great resemblance with the validation data, demonstrating capabilities of resolving very complex flow phenomena with minimum user input if the computational grid is fine enough. In order to demonstrate even greater advantages of non-linear models it was postulated that the addition of a streamwise impinging vortex hitting the leading edge of the cylinder would make the flow field fully three-dimensional. First attempts were tried in this route but time constraints limited the ultimate scope of the present work.

Categories

Physical Systems and Engineering simulation: CFD

Algorithms and computational methods: FFT, Finite volume

Visualisation and data handling methods: Data Management

Simulation software: OpenFOAM

Visualisation and data handling software: Gnuplot, MS Office Access, TecPlot

Programming languages and libraries: C++, Matlab

Computational platforms: Linux, Lyceum, Windows