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This is a followup post of:
https://sites.google.com/view/olaflowcfd/blog/turbulence-models-for-wave-simulations
Since turbulence is an extremely important physical process, especially when studying wave breaking or wave impacts on a structure, every attempt to enhance two equation models, the most widely used today, takes CFD one step further.
Today olaFlow CFD is updating its turbulence modelling library to include the most recent advances.
This library is part of the olaFlow supplementary materials repository:
It is hosted in the turbulenceMultiphase folder and includes the source code and a tutorial to test the effects of the turbulence models. You can follow the link for full information on how to download and compile this module and use it in you cases.
This repository provides modified versions of k-ε and k-ω SST turbulence models to simulate correctly multiphase systems, accounting for the density of each phase in the equations (kEpsilonMultiphase, kOmegaSSTMultiphase).
Moreover, new variations of the k-ω SST model were recently proposed in two excellent papers by Devolder et al. (2017, 2018) and Larsen & Fuhrman (2018) to model free surface cases (e.g. waves) correctly. The models (kOmegaSSTBuoyancy & kOmegaSSTStable) feature an additional buoyancy term presented in Devolder et al. (2017, 2018) that helps suppress the spurious turbulence generation at the free surface.
The latest addition is kOmegaSSTStable, which also includes the modified nut formulation in Larsen & Fuhrman (2018) to mitigate the instability of the model that causes the turbulence build-up even under potential flow conditions.
As you can observe in the video below, these changes really make a difference!
References
References
Devolder, B., Rauwoens, P. & Troch, P. (2017)
Application of a buoyancy-modified k-ω SST turbulence model to simulate wave run-up around a monopile subjected to regular waves using OpenFOAM®.
Coastal Engineering, 125, 81–94.
Devolder, B., Troch, P. & Rauwoens, P. (2018)
Performance of a buoyancy-modified k-ω and k-ω SST turbulence model for simulating wave breaking under regular waves using OpenFOAM®.
Coastal Engineering, 138, 49–65.
Larsen, B.E. & Fuhrman, D.R. (2018)
On the over-production of turbulence beneath surface waves in RANS models.
Journal of Fluid Mechanics, 853, 419–460.
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