Advances in Mathematical Physics

Volume 2018, Article ID 9248174, 6 pages

https://doi.org/10.1155/2018/9248174

## Expanded () Expansion Method to Solve Separated Variables for the 2+1-Dimensional NNV Equation

College of Science, Ningbo University, Ningbo 315211, China

Correspondence should be addressed to Yong Meng; nc.ude.ubn@0241701161

Received 28 May 2018; Accepted 16 July 2018; Published 9 August 2018

Academic Editor: Ping Li

Copyright © 2018 Yong Meng. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

The traditional (G/G^{2}) expansion method is modified to extend the symmetric extension to the negative power term in the solution to the positive power term. The general traveling wave solution is extended to a generalized solution that can separate variables. By using this method, the solution to the detached variables of the symmetric extended form of the 2+1-dimensional NNV equation can be solved, also the soliton structure and fractal structure of Dromion can be studied well.

#### 1. Introduction

The nature of this world is nonlinear, and linearity is only an approximation under certain conditions. And the reason why this large world is so colorful and varied is that there is a nonlinear relationship between things. In nonlinear science we start from the actual nonlinear phenomena; according to the laws of physics, the corresponding mathematical models are established under reasonable approximations, and then the corresponding laws are obtained by studying these mathematical models. A large part of these equations is nonlinear partial differential equations. It is not easy to solve these partial differential equations. For many years people have done a lot of work for this and have achieved a series of important results, such as the Inverse Scattering Transformation(IST) [1], Darboux transform [2, 3], Lie group and nonclassical Lie group method [4, 5], Hirota bilinear method [6–8], and other important methods. Among them, the function expansion [9–19] has the advantages of simplicity, directness, and ease of operation. So there is a lot of use in solving nonlinear partial differential equations.

Li proposed an expansion method in [20] to solve the new traveling wave solution for the Vakhnenko equation. However, for a large number of nonlinear systems, it is difficult to fully describe only the traveling wave solution, and it will inevitably lose other solutions with a rich structure. This paper reconstructs this method and extends the expansion of the solution symmetrically to negative power. Moreover, the variable is separated by the solution, and more forms of solutions are obtained. The symmetric extension of the 2+1-dimensional NNV equation is solved by using this method. A solution of this equation is studied to get soliton solution and fractal structure solution.

#### 2. Separation Variable Solutions to Symmetric Extensions of 2+1-Dimensional NNV Equations

The 2+1-dimensional NNV equationis a Lax integrable generalization of all isotropic properties of the 1+1-dimensional KdV equation. We first determine the maximum power of the expansion term in expansion formula by the principle of homogeneous equilibrium [21–23] to be 2 and extend the symmetry extension of the solution to the negative power term (-2). Then set the expression for towhere are functions of .

At the same time achieves an ordinary differential equationIt can be obtained from (7)In order to achieve the separation of variables, we setSubstituting (4)~(6) into (1)~(3), if there is a high-order derivative of , then use the ordinary differential equation (7) to replace the first derivative of G. That is, That is, (1)~(3) become three power polynomials about . Let the coefficient of each power of of this polynomial be zero, resulting in a set containing partial differential equations. Then, (11) is substituted into the partial differential equation group, and finally the partial differential equation group is solved to obtain three sets of solutions.

First group isSecond Group isThe third group iswhere is any function about .Then (12)~(14) are substituted into (4)~(5) and three solutions to the 2+1-dimensional NNV equation are obtained.where is the expression in (8)~(10).

#### 3. Soliton Structure and Fractal Structure of the 2+1 Dimensional NNV Equation

Substituting (8) into (15) givesThen select the parameters selected asas well asThe periodic wave background Dromion soliton and double Dromion soliton can be obtained as shown in Figure 1.