A KdV-like advection-dispersion equation with some remarkable properties

TL;DR

This paper introduces a new nonlinear PDE called SIdV, which exhibits properties bridging advection, diffusion, and dispersion, and shares features with KdV and mKdV equations, offering a novel model for studying wave phenomena.

Contribution

The paper presents SIdV, a novel PDE with unique symmetry and conservation properties, discovered via genetic programming, expanding the family of equations related to KdV with potential for further research.

Findings

SIdV admits solitary and periodic traveling waves.

Numerical simulations show recurrence properties akin to integrable systems.

SIdV shares the KdV solitary wave solution and connects to known dispersive equations.

Abstract

We discuss a new non-linear PDE, u_t + (2 u_xx/u) u_x = epsilon u_xxx, invariant under scaling of dependent variable and referred to here as SIdV. It is one of the simplest such translation and space-time reflection-symmetric first order advection-dispersion equations. This PDE (with dispersion coefficient unity) was discovered in a genetic programming search for equations sharing the KdV solitary wave solution. It provides a bridge between non-linear advection, diffusion and dispersion. Special cases include the mKdV and linear dispersive equations. We identify two conservation laws, though initial investigations indicate that SIdV does not follow from a polynomial Lagrangian of the KdV sort. Nevertheless, it possesses solitary and periodic travelling waves. Moreover, numerical simulations reveal recurrence properties usually associated with integrable systems. KdV and SIdV are the simplest in an infinite dimensional family of equations sharing the KdV solitary wave. SIdV and its generalizations may serve as a testing ground for numerical and analytical techniques and be a rich source for further explorations.