Presenters

Johan Roenby

FloatStepper : A robust algorithm for computational floating body dynamics

CFD is potentially a very powerful tool for assessing floater-wave dynamics when designing floating offshore wind floaters.
However, the so-called added mass instability problem can under some circumstances be a big nuisance causing simulations to crash apparently out of nowhere. The problem is particularly pronounced when the body is much lighter than the surrounding fluid. The traditional remedy in OpenFOAM is to introduce underrelaxation of the calculated body acceleration and outer correctors, where both fluid and body motion are calculated multiple times within each time step. This is computationally expensive, and stability is still not guaranteed. To overcome this problem, we device a new algorithm, dubbed FloatStepper, where we conceptually divide the forces on the floater into an added mass term and everything else, and then calculate each term separately before taking the actual CFD time step. This removes the root cause of the added mass instability, and we demonstrate with simple benchmarks that the solver works and is stable for arbitrarily low body mass. Finally, we demonstrate the capabilities of the solver on various more advanced benchmark cases with real floaters and discuss current limitations and future improvements.

 

Tom Fahner

Wind Assessment Tool - Pedestrian wind comfort studies for non OpenFOAM experts

Urban planning in recent years is focusing on more densely populated areas, where high-rise buildings are replacing medium to low-rise buildings to accommodate more residents on a smaller surface area. These changes result in challenges in terms of city planning and quality of life for people living in these areas.

One of the aspects that becomes important in the case of tall buildings is pedestrian wind comfort. Predicting the effect of the change in the built environment typically requires a CFD or wind tunnel study. Most architects however lack the technical knowledge to carry out these studies. On the other hand they are interested in a quick assessment of their design in terms of the wind climate effects. Our Wind Assessment Tool provides this service in early stage development. All that is necessary from the architect is a model of their building, the surrounding buildings and some details about the location. Within hours the wind climate is assessed and can be compared to other design variants in a web browser. For more detailed analysis of the results, 3D data can be downloaded. The WAT is a dedicated tool combining the design knowledge of the architect with our knowledge on CFD and OpenFOAM.

 

Sebastiaan Kuipers

MultiRegionFoam: solving multiphysics problems of the multi-region coupling type within OpenFOAM

 

Eduard Montella

Modeling granular flow dynamics and structure interaction Insights from sedFoam solver.pdf