Sadarjoen, AriBoer, Alex J. dePost, Frits H.Mynett, Arthur E.Bartz, Dirk2015-11-192015-11-1919983-211-83209-2-https://doi.org/10.2312/vissym19981006Particle tracing in curvilinear grids often employs decomposition of hexahedral cells into 5 tetrahedra. This method has shortcomings when applied to sigma-transformed grids, a grid type having strongly sheared cells, commonly used in hydrodynamic simulations. This paper describes an improved decomposition method into 6 tetrahedra. It is shown that this method is robust in sigma-transformed grids, however large the shear- ing. Results are presented of applying the technique to a real world sim- ulation. Comparisons are made between the accuracy and speed of the 5-decomposition and the 6-decomposition methods.10.2312/vissym19981006