Multiphysics Code TransAT© by Ascomp
TransAT© is a multi-physics, finite-volume code based on solving single and multi-fluid Navier-Stokes equations on structured multi-block meshes. The grid arrangement is collocated and can thus handle more easily Body-Fitted Coordinates (BFC) grids. The solver is pressure based (Projection Type), corrected using the Karki-Patankar technique for subsonic to supersonic compressible flows. High-order time marching and convection schemes can be employed; up to 3rd order Monotone and TVD-bounded schemes in space and 5thorder RK in time. An algebraic multigrid algorithm is employed for the pressure equation, involving relaxation, restriction and prolongation up to 6 levels, to achieve high rates of convergence and error estimation. Multiphase flows can be tackled using (i) interface tracking techniques (Level Set, VOF with interface reconstruction, and Phase Field), (ii) N-phase, phase-averaged mixture with Algebraic Slip, and (iii) Lagrangian particle tracking (one-to-four way coupling). Re-distancing of level set is ensured via 3rd order WENO scheme in Cartesian meshes and via fast marching BFC grids. Mass conservation is enforced using global and local mass and volume conserving schemes.
Besides BFC meshing, TransAT also uses the Immersed Surfaces Technique (IST) to map complex geometries into a rectangular Cartesian grid (IST was used in the 3D problems treated here). Near wall regions are treated with Block Mesh Refinement (BMR), a sort of geometrical multi-grid approach in which refined grid blocks or manifolds are placed where adequate. This multigrid is different from the algebraic multigrid algorithm discussed above, in that each BMR block is separately solved and the solutions are passed from one block to the next as an initial flow field. The connectivity between blocks can be achieved in parallel up to 8-to-1 cell mapping. The combination IST/BMR saves up to 70% grid cells in selected 3D problems and allows for conjugate-heat transfer and rigid body motion.
TransAT can be used to predict fluid flow and heat transfer in various industries, oil & gas, nuclear safety engineering, microfluidics, mechanical and chemical engineering, renewable energy and water technology.