**Sunmi Lee**

Department of Applied Mathematics, Kyunghee University, Yongin-si, Korea; sunmilee@khu.ac.kr; Tel.: +82-31-201-2409

Received: 27 March 2018; Accepted: 23 April 2018; Published: 24 April 2018

**Abstract:** The forced Korteweg-de Vries equation is considered to investigate the impact of bottom configurations on the free surface waves in a two-dimensional channel flow. In the study of shallow water waves, the bottom topography plays a critical role, which can determine the characteristics of wave motions significantly. The interplay between solitary waves and the bottom topography can exhibit more interesting dynamics of the free surface waves when the bottom configuration is more complex. In the presence of two bumps, there are multiple *trapped solitary wave solutions*, which remain stable between two bumps up to a finite time when they evolve in time. In this work, various stationary trapped wave solutions of the forced KdV equation are explored as the bump sizes and the distance between two bumps are varied. Moreover, the semi-implicit finite difference method is employed to study their time evolutions in the presence of two-bump configurations. Our numerical results show that the interplay between trapped solitary waves and two bumps is the key determinant which influences the time evolution of those wave solutions. The trapped solitary waves tend to remain between two bumps for a longer time period as the distance between two bumps increases. Interestingly, there exists a nontrivial relationship between the bump size and the time until trapped solitary waves remain stable between two bumps.

**Keywords:** forced Korteweg-de Vries equation; trapped solitary wave solutions; numerical stability; two bumps or holes; finite difference method
