H-Allegro Gallery

3D NSCBC modeling for transverse and corner outflows

The limitations of usual three dimensional Navier–Stokes Characteristic Boundary Conditions (3D-NSCBC) for flows traveling in a direction that is oblique to the boundary may induce flow deformation at the vicinity of the outflow/ To limit errors generated at boundaries with flows having any arbitrary direction, we propose to organize the wave decomposition in a coordinate system that is attached to the local flow streamline crossing the boundary, because some modeled expressions are not frame independent. Compared to previous 3D-NSCBC, the modified strategy accounting for oblique waves is found to improve the outflow treatment for transverse outgoing vortices, up to vortices crossing an outflow corner. The method is also applied to an expanding laminar flame.

TOM strategy compared to 3D-NSCBC & NSCBC

• E. Albin, Y. D'Angelo & L. Vervisch, Flow streamline based Navier-Stokes Characteristic Boundary Conditions: modeling for transverse and corner outflows, Computers and Fluids, 51, 1, pp. 115-126, 2012 http://dx.doi.org/10.1016/j.compfluid.2011.08.005

• E. Albin, Y. D'Angelo & L. Vervisch, Using staggered grids with acoustic boundary conditions when solving compressible reactive Navier-Stokes equations, International Journal for Numerical Methods in Fluids, 2012 http://dx.doi.org/10.1002/fld.2520

Direct simulation of propagating flames: 3D expanding or converging front

Three dimensional simulation of a propane/air stoichiometric expanding flame. Iso-contours of vorticity (blue to red) and of reaction rate (green). Physical times range here from 0.49 to 7.28 ms.

• DNS of propane/air 3D expanding flame
• Mesh 480 x480 x 480 (~110 million grid points) ; dx~60 microns; 3x3x3 cubic cm
• Initial Passot-Pouquet spectrum then cold flow DNS for obtaining decreasing turbulence
• 512 proc, 70 000 CPU hours
• albin.mp4

• E. Albin & Y. D’Angelo, Assessment of the Evolution Equation Modelling approach for three-dimensional expanding wrinkled premixed flames, Combustion & Flame, Vol. 159, Issue 5, pp 1932–1948, May 2012 http://dx.doi.org/10.1016/j.combustflame.2011.12.019