Colloquium: Sampath Raghunathan Srikumar (AWEP)

26 september 2019 16:00 - Locatie: Lecture Room D, Faculty of Aerospace Engineering, Kluyverweg 1, Delft

LES of a novel wing/body junction : Anti-fairing

Large Eddy Simulations (LES) of a novel type of wing/body junction called the anti-fairing are performedin the current thesis to study the complex turbulent flow physics involved in the junction area and also toobtain a clear understanding of the drag reduction capabilities of the anti-fairing. In regards to that, twoseparate LES are performed: one for the baseline case with a Rood wing/flat plate combination and anotherwith the Rood wing/anti-fairing combination. A detailed comparative study is performed between the twocases to observe important differences in junction flow characteristics. Both the simulations are performedon a 25 million immersed boundary Cartesian mesh by solving the incompressible Navier-Stokes equationsusing the in-house finite volume LES solver called INCA. Results from the LES study confirms the existenceof the propulsive pressure mechanism of drag reduction for the anti-fairing case, previously proposed by Bel-ligoli et al. However, the results also shows that there exists a secondary drag reduction mechanism causedby a combination of increase in approach boundary layer momentum thickness and dampening of the tur-bulence associated with the horseshoe vortex (HSV) upstream of the wing. This secondary mechanism hasbeen found to be caused by the convex dent present at the start of the anti-fairing geometry. The total dragreduction for the anti-fairing case comes out to be 1.8%. A new parameter called junction drag is definedwhich accounts for the drag only due to the presence of a junction. The reduction in junction drag obtainedfor the anti-fairing case is about 6.8%. Apart from the LES analysis, a RANS analysis has also been performedto further investigate the drag reduction capabilities of anti-fairing for different approach boundary layerthicknesses and anti-fairing depths. All the RANS analysis have been performed on a 5 million body-fittedmesh by solving the incompressible Navier-Stokes using the open source finite-volume solver OpenFOAM.Results from the RANS analysis indicate that there exists an optimum depth for the anti-fairing which cor-responds to the least drag. Furthermore, it is found that the effect of approach boundary layer thickness ismostly on changing the base drag of the case where no anti-fairing is present, rather than actually affectingthe performance of the anti-fairing at different depths.