The HyperCASL algorithm: A new approach to the numerical simulation of geophysical flows

Jerome Fontane (1) , David Dritschel (1)

1 University of St Andrews [Scotland]

We describe a major extension to the Contour-Advective Semi-Lagrangian (CASL) algorithm (Dritschel & Ambaum 1997, 2006). The extension, called 'HyperCASL' (HCASL), uses Lagrangian advection of material potential vorticity contours like CASL, but a Vortex-In-Cell (VIC) method for the treatment of diabatic forcing or damping. In this way, HyperCASL is fully Lagrangian regarding advection. A grid is used as in CASL to deal with 'inversion' (computing the velocity field from the potential vorticity field). First, the novel aspects of the algorithm are described including several improvements to the underlying CASL algorithm. All numerical parameters are chosen so as to minimise the computational cost while improving conservation properties. Finally, a thorough intercode comparison is conducted using a two-dimensional inviscid unforced turbulence test-case. This enables us to point out the advantages of this new algorithm in terms of resolution, computational cost and numerical diffusion compared to other existing methods, namely CASL, VIC and Pseudo-Spectral (PS) methods.

Mots clés: Contour dynamics; Vortex methods; Contour advection; Geophysical flows

Domaines: Dynamique des Fluides [physics.flu-dyn]

Jerome Fontane, David Dritschel. The HyperCASL algorithm: A new approach to the numerical simulation of geophysical flows. Journal of Computational Physics, 2009, vol. 228, pp. 6411-6425. ⟨10.1016/j.jcp.2009.05.025⟩. ⟨hal-00786314⟩