In linear science, the wave motion equation with general D’Alembert wave solutions is one of the fundamental models. The D’Alembert wave is an arbitrary travelling wave moving along one direction under a fixed model (material) dependent velocity. However, the D’Alembert waves are missed when nonlinear effects are introduced to wave motions. In this paper, we study the possible travelling wave solutions, multiple soliton solutions and soliton molecules for a special (2+1)-dimensional Koteweg-de Vries (KdV) equation, the so-called Nizhnik-Novikov-Veselov (NNV) equation. The missed D’Alembert wave is re-discovered from the NNV equation. By using the velocity resonance mechanism, the soliton molecules are found to be closely related to D’Alembert waves. In fact, the soliton molecules of the NNV equation can be viewed as special D’Alembert waves. The interaction solutions among special D’Alembert type waves (n-soliton molecules and soliton-solitoff molecules) and solitons are also discussed.

在线性科学中，具有一般D'Alembert波解的波动方程是基本模型之一。D'Alembert波是在与模型（材料）有关的固定速度下沿一个方向移动的任意行波。但是，将非线性效应引入波运动时会错过D'Alembert波。在本文中，我们研究了特殊（2 + 1）维Koteweg-de Vries（KdV）方程（所谓的Nizhnik-Novikov-Veselov（NNV）方程）的可能行波解，多个孤子解和孤子分子。从NNV方程中重新发现错过的D'Alembert波。通过使用速度共振机制，发现孤子分子与D'Alembert波密切相关。实际上，NNV方程的孤子分子可以看作是特殊的D'Alembert波。还讨论了n-孤子分子和孤子-孤子分子和孤子。