Overview

Cocoa (Coastal and Ocean Circulation on Accelerators) solves the 2D depth-integrated shallow water equations on unstructured triangular meshes.

Model Capabilities

Cocoa is designed for simulating:

• Tidal circulation in coastal and estuarine environments

• Storm surge from tropical and extratropical cyclones

• Coastal flooding and inundation

• Tide-surge interaction in complex geometries

Physical Processes

The model includes the following physical processes:

Hydrodynamics

• 2D depth-integrated momentum equations

• Generalized Wave Continuity Equation (GWCE)

• Advection and diffusion

Forcing Mechanisms

• Tidal boundary forcing with multiple constituents

• Astronomical tide potential (direct Moon/Sun computation)

• Atmospheric pressure gradients

• Wind stress (Garratt drag law)

Bottom Friction

• Quadratic bottom friction

• Variable friction coefficients

Wetting and Drying

• Element-based wet/dry algorithm

• Maintains mass conservation

Computational Features

GPU Acceleration

Cocoa leverages Kokkos for GPU acceleration:

• NVIDIA GPUs via CUDA

• AMD GPUs via HIP

• Multi-core CPUs via OpenMP

• Serial execution for debugging

See Performance for benchmark results comparing Cocoa with ADCIRC.

Scalable Solvers

Linear systems are solved using Trilinos:

• Belos iterative solvers (CG)

• Ifpack2 preconditioners (Jacobi)

• Tpetra linear algebra structures

• Kokkos for performance portability