1. A computer program product tangibly embodied in a computer readable medium, the computer program product including instructions that, when executed, simulate a physical process, the computer program product configured to cause a computer to: store, in a computer-accessible memory, state vectors for voxels, the state vectors corresponding to a model and comprising a plurality of entries that correspond to particular momentum states of possible momentum states at a voxel; perform interaction operations on the state vectors, the interaction operations modeling interactions between elements of different momentum states according to the model; and perform move operations on the state vectors to reflect movement of elements to new voxels according to the model, wherein the model is adapted to simulate a high-Knudsen number flow that has a Knudsen number greater than 0.1.