Abstract

Two types of analytical undular bore solutions, of the initial value problem for the modified Kortewegde Vries (mKdV), are found. The first, an undular bore composed of cnoidal waves, is qualitatively similar to the bore found for the KdV equation, with solitons occuring at the leading edge and small amplitude linear waves occuring at the trailing edge. The second, a newly identified type of undular bore, consists of finite amplitude sinusiodal waves, whihc have a rational form. At the leading edge is the mKdV algebraic soliton, while, again, small amplitude linear waves occur at the trailing edge. The initialboundary value (IBV) problem for the mKdV equation is also examined. The solutions of the initial value problem are used to cosntruct approximate analytical solutions of the IBV problem. An alternative analytical solution for the IBV problem, based on the assumption of an uniform train of solitons, is also developed. The parameter regimes, in which the different types of solition occur, for both the initial value and IBV problem are identified and excellent comparisions are obtained between the numerical and approximate solutions, for both problems.