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The Noh problem (Noh 1987) is a standard verification problem for hydrocodes. A sphere of a gamma-law gas is uniformly compressed, testing a codes ability to transform kinetic energy into internal energy, and the ability to follow supersonic flows. This code released under LA-CC-05-101.
In the Noh problem, a spherical, cold ideal gas is initialized with a uniform, radially inward speed of 1 cm/s. A shock forms at the origin and propagates outward as the gas stagnates. For an initial gas density of 1 g/cc, the analytic solution for gamma = 5/3 predicts a density in the stagnated gas, after passage of the outward shock, of 64 g/cc. Most hydrodynamics codes, produces anomalous "wall-heating" neat the origin. This heating causes premature stagnation, with densities much lower than predicted in the centermost cells.
 3d noh |
 analytical and numerical |
 convergence study |
 evolution movie |
noh.f solves the Noh problem |
Density uniform mesh:
 density 200x200 cells |
 density 400x400 cells |
 density 800x800 cells |
 density error 200x200 cells |
 density error 400x400 cells |
 density error 800x800 cells |
 density asymmetry 200x200 |
 density asymmetry 400x400 |
 density asymmetry 800x800 |
Pressure uniform mesh:
 pressure 200x200 cells |
 pressure 400x400 cells |
 pressure 800x800 cells |
 pressure error 200x200 cells |
 pressure error 400x400 cells |
 pressure error 800x800 cells |
 pressure asymmetry 200x200 |
 pressure asymmetry 400x400 |
 pressure asymmetry 800x800 |
Material Speed uniform mesh:
 speed 200x200 cells |
 speed 400x400 cells |
 speed 800x800 cells |
 speed error 200x200 cells |
 speed error 400x400 cells |
 speed error 800x800 cells |
Density adaptive mesh:
 density 200x200 cells |
 density 400x400 cells |
 density 800x800 cells |
 density error 200x200 cells |
 density error 400x400 cells |
 density error 800x800 cells |
Pressure adaptive mesh:
 pressure 200x200 cells |
 pressure 400x400 cells |
 pressure 800x800 cells |
 pressure error 200x200 cells |
 pressure error 400x400 cells |
 pressure error 800x800 cells |