The conduit equation : hyperbolic approximation and generalized Riemann problem
Résumé
The conduit equation is a dispersive non-integrable scalar equation modeling the flow of a low-viscous buoyant fluid embedded in a highly viscous fluid matrix. This equation can be written in a special form reminiscent of the famous Godunov form proposed in 1961 for the Euler equations of compressible fluids. We propose a hyperbolic approximation of the conduit equation by retaining the Godunov-type structure. The comparison of solutions to the conduit equation and those to the approximate hyperbolic system is performed : the wave fission of a large initial perturbation of a rectangular or of gaussian form. The results are in good agreement. New generalized solutions to the conduit equation are discovered composed of a finite set of waves of the same period and linked with a constant solution by generalized Rankine-Hugoniot relations. Such multi-hump structures interact which each other almost as solitary waves : they collide, merge and reconstruct after the interaction. This partly indicates the stability of such multi-hump solutions under small perturbations. Both the exact and approximate hyperbolic system describe such an interaction with good accuracy.
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