Modified Adomain Decomposition Method for the Generalized Fifth Order KdV Equations

New modified Adomian decomposition method is proposed for the solution of the generalized fifth-order Korteweg-de Vries (GFKdV) equation. The numerical solutions are compared with the standard Adomian decomposition method and the exact solutions. The results are demonstrated which confirm the efficiency and applicability of the method.


Introduction
The fifth-order (or generalized) KdV is the essential a model foe several physical phenomena including shallow-water waves near critical value of surface tension and waves in nonlinear LC circuit with mutual inductance between neighbouring inductors [1].Although no general solution is known, the exact solution of the fifth order KdV equation has been found for the special case of solitary waves in [2].In general, the fifth order KdV need to be solved numerically.Commonly used numerical methods to approximate the solutions of (gfKdV) include finite difference methods, collection methods and Galerkin methods.Kawahara [3] investigated the steady solutions of this equation on the basis of numerical calculations.Boyd [4] and Haupt and Boyd [5] reduced this equation to an ordinary differential equation and then a variety of analyticl and numerical methods are developed.The numerical methodes are based on Newton-Kantorovich pseudo-spectral method and Newton-Kantorovich Galerkin method.In [6] K. Djidjeli et al. proposed finite deference schemes based on a predictorcorrector algorithm and a linearized implicit method for the third and fifth order KdV equations.
However, some of these methods are not easy to use and sometimes require tedious work and calculation [7,8].In recent years, Adomian decomposition methods (ADM) [9] have emerged as a powerful tool for a wide class of nonlinear equation [10].G. Adomian in [11] applied his method to the 5th order KdV equation.In [12,13], D. Kaya calculated the explicit and numerical solutions of some fifth-order KdV equation by decomposition method and Kaya and El-Sayed in [14] proved the convergence of (ADM) applied to (gfKdV) equation.

A comparative study between (ADM) and Crank
Nicholas method presented in [15].(ADM) has led to several modifications on the method made by various researches in order to improve the accuracy or expansion of the application of the original method.Wazwaz [16] presented a reliable modification of the Adomian decomposition method.
In 2001, Wazwaz presented another type of modification [17] to the (ADM).Wazwaz modifications arises in the initial definition of the operator when applying the (ADM) to the nonlinear equation.
To the best of our knowledge, no attempt is made regarding the solution of generalized fifth order KdV equations by using modified decomposition method.So our main aim in this paper is used the modification ADM to solve the five particular class of the (gfKdV) equations.We generalized an appropriate Adomian's polynomials for (gfKdV) equation will be handle more easily, quickly, and elegantly by implementing the new modified (ADM) rather than traditional methods for the exact solution of which is to be obtained subject to initial condition.

Fifth-Order KdV Equations
The well-known fifth-order KdV (fKdV) equations can be shown in the form Typical examples widely used in various fields such as solid state physics, plasma physics, fluid physics and quantum field theory.A variety of the (fKdV) equations can be developed by changing the real values of the parameters a, b and c [18]. the derivation of these fifthorder forms are derived specific bilinear forms of the so-called Hirota's D-operators.However, five will known forms of the (fKdV) that are of particular interest in the literature.These forms are: 1) The Sawada-Kotera (SK) equation is given by [19] 2 45 15 15 0 2) The Caudrey-Dodd-Gibbon (CDG) equation is given by [20] 2 180 30 30 0 3) The Lax equations [21] 2 30 30 10 0 4) The Kaup-Kuperschmidt (KK) equation [22,23] 2 20 25 10 0 5) The Ito equation [24] 2 2 6 3

Adomian Decomposition Method
In this section, we give outline and implement Adomian decomposition method for nonlinear equations to obtain analytic and approximate solutions which are obtained in a rapidly convergent series with elegantly computable components by this method.The Adomian approximation series converge quickly.In general, convergence regions of the series are small.Now we outline of the method here in order to obtain the solutions using (ADM), consider the fifth-order KdV Equation ( 1) in an operator form where the notations 2 ,

N uu 
x By symbolizing the nonlinear term, respectively.The notation t L t the linear differential operators.Assuming the inverse of operator exists and it can conveniently be taken as the definite integral with respect to from 0 to , i.e., Thus, applying the inverse operator to (7) yields; Therefore, it follows that Since initial value is known and we decompose the unknown function   , u x t as a sum of components defined by the decomposition series with identified as . The nonlinear terms u K u M and u can be decomposed into infinite series of polynomial given by , n A and are the so-called Adomian polynomials of defined by Substituting (11)(12)(13)(14) into (10) gives rise to The solution   , u x t must satisfy the requirements imposed by the initial conditions.Based on the (ADM), we constructed the solution as The decomposition method provides a reliable technique that requires less work if we compared with the traditional techniques.

New Modified Adomian Decomposition Method
In the new modification by Wazwaz [17], we can replace the process of identified 0 u as by dividing by a series of infinite components.We therefore suggest that A new recursive relationship expressed in the form We can observe that algorithm (19) reduces the number of terms involved in each component, and hence the size of calculations is minimized compared to the standard (ADM) only.Moreover this reduction of terms in each component facilitates the construction of Adomian polynomials for nonlinear operators.the new modification overcomes the difficulty of decomposing   ,0 u x and introduces an efficient algorithm that improves the performance of the standard (ADM).

Numerical Experiments
In this section, we consider some (gfKdV) equations for numerical comparisons based on the new modifications of (ADM).In this paper, we illustrate how the approximate solutions of the (gfKdV) equations are close to exact solutions.

Example (1): (Sawada-Kotera Equation)
we consider the (S-K) Equation [25], with initial condition is given by and the exact solution Table 1 shows the difference of the analytical solution and numerical solution of the absolute errors only for 5 iterative.

Example (2): (Caudrcy-Dodd-Gbbon (C-D-G) Equation)
we consider the (C-D-G) equation, with initial condition and the exact solution Table 2 shows the numerical results for example (2) for .0.01 k 

Example (3): (The Lax Equation)
we consider Lax's fifth order KdV equation with the initial condition: and the exact solution Table 3 shows the numerical results for example (3) for 0.01 k  , 0 0.0 x  .

Example (4): (Kaup-Kuperschmidt (K-K) Equation)
We consider the (K-K) equation with the initial condition   Table 4 shows the numerical results for example (4) for 0.01 k  .
Table 5 shows the numerical results for example (5) for 0.01 k  and 0 0.0 x  .

Conclusions and Remarks
In this work, we proposed new modification of Adomian decomposition method.We solved the five well known forms of the (fKdV) equation with initial conditions.The method has been shown to computationally efficient in these examples that are important to researchers in applied sciences.The obtained results in examples indicted that the new modification of (ADM) was feasible and effective.The method overcomes the difficulties arising in the modified decomposition method established in [16].
The results show that the presented method is powerful mathematical tool for finding good approximate solu-      tions of (gfKdV) equation with initial conditions and results are found to be in good agreement with the exact solution as shown from Figures 1-5.In addition, no linearization or perturbation is required by the method.