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Applied Mathematics and Nonlinear Sciences 4(1) (2019) 35–42
Applied Mathematics and Nonlinear Sciences
https://www.sciendo.com
Numerical Solutions with Linearization Techniques of the Fractional Harry Dym
Equation
Asıf Yoku¸s1, Sema Gülbahar2
1Department of Actuary, Firat University, 2300, Elazig, Turkey,
E-mail: asfyokus@firat.edu.tr
2Department of Mathematics, Harran University, Sanliurfa, Turkey,
E-mail: semaakkus_mat@hotmail.com
Submission Info
Communicated by Juan Luis García Guirao
Received 14th January 2019
Accepted 21st February 2019
Available online 27th March 2019
Abstract
In this study, numerical solutions of the fractional Harry Dym equation are investigated. Linearization techniques are
utilized for non-linear terms existing in the fractional Harry Dym equation. The error norms L2and L∞are computed.
Stability of the finite difference method is studied with the aid of Von Neumann stabity analysis.
Keywords: Harry Dym equation, finite difference method, von Neumann stability analysis.
1 Introduction
Fractional analysis; is the generalization of the classic analysis of integration and differentiation of process
(noninteger) order. This issue is an old issue as much as differential calculus. G. W. Leibniz and Marquis de
L0Hospital correspondence in 1695, is known as the first exit point of fractional calculus. Leibniz expressed
fractional order derivatives of noninteger order f(x) = emx,m∈R, as follows:
dnemx
dxn=mnemx ,
here, nis a value, where i is the noninteger.
Later, many scientists, such as Liouville, Riemann, Weyl, Lacroix, Leibniz, Grunward and Letnikov (cf. [4]),
expanded the range of this derivative.
Since the beginning of the definition of fractional order derivatives first handled by Leibniz, fractional partial
differential equations have attracted the attention of many scientists and have also shown a progressive develop-
ment.(cf. [1–9,11,13–19]).
ISSN 2444-8656 doi:10.2478/AMNS.2019.1.00004
36 J.P. Ruiz-Fernández et al. Applied Mathematics and Nonlinear Sciences 4(2019) 35–42
Beside these facts, the third order fractional Harry Dym partial differential equation is studied in mathematics
and especially in the theory of solitons. This equation is given as
∂γu
∂tγ=u3∂3u
∂x3.(1.1)
Here, 0 <γ≤1 is the order of fractional derivative and u(x,t)is a function of xand t.
The Harry Dym equation first appeared in a study by Kruskal [10]. Harry Dym equation represents a system
in which dispersion and nonlinearity were coupled. Furthermore, the Harry Dym equation is a completely
integrable nonlinear evolution that may be solved by means of the inverse scattering transform. It does not
possess the Painlevé property.
This paper is organized as follows:
In the second section, some basic facts dealing with the finite difference method are mentioned and three Lin-
earization techniques are presented. In the third section, stability analysis of the proposed method is investigated
and it is shown that the Harry Dym equation is stable under which conditions. Also, numerical examples are
given. In the fourth section, conclusions obtained throughout the paper are discussed.
2 Finite Difference Methods
In this section, we first need to define a set of grid points in a domain Dto obtain a numerical solution to Eq.
(1.1)using finite difference methods as follows:
Let ∆x(h) = b−a
N(Nis an integer) denotes a state step size and ∆tdenotes a time step size. Draw a set of
horizontal and vertical line across D, and get all intersection points (xj,tn)or simply (j,n)where xj=a+j∆x,
j=0,1,2,··· ,N, and tn=n∆t,n=0,1,...,M. If we write D= [a,b]×[0,T]then we may choose ∆t=T
M(M
is an integer) and tn=n∆t,n=0,1,...,M.
Then, an appropriate finite difference approximation is given in Eq. (1.1) instead of derivatives and its vari-
able. In this case, the solution problem of Eq. (1.1) is reduced to solution problem of algebraic differential sys-
tems of linear and nonlinear equations consisting of finite difference equation. But when applied to non-linear
problems, it normally leads to nonlinear system of equations and they cannot be solved directly. Therefore, we
use three linearization techniques for a nonlinear term as given in Eq. (1.1).
2.1 Linearization 1
First, we use the Caputo fractional derivative approximation for ∂γu
∂tγdefined by
∂γu
∂tγ'1
h2
(∆t)−γ
Γ(2−γ)
n
∑
k=0un+1−k
m−un−k
mh(k+1)1−γ−k1−γin≥1
(∆t)−γ
Γ(2−γ)u1
m−u0
mn=0,
and Crank–Nicolson derivative approximation given by
u=un+1+un
2,
in Eq. (1.1) at the nodal point (m,n+1)[12]. Then, if we discretize time derivative of the fractional Harry Dym
equation by using Caputo fractional derivative formula between two successive time levels nand n+1, Crank
Nicolson derivative formula and usual finite difference formula between two successive time levels nand n+1,
Numerical Solutions with Linearization Techniques of the Fractional Harry Dym Equation 37
respectively, we obtain
(∆t)−γ
Γ(2−γ)
n
∑
k=0hun+1−k
m−un−k
mih(k+1)1−γ−k1−γi(2.1)
="u3n+1
m+u3n
m
2#un
m+2−2un
m+1+2un
m−1−un
m−2
2h3.
The nonlinear term in the above mentioned equation is linearized by using the following equation:
u3n+1
m=3u2nun+1−2u3n.
If the necessary arrangements are made in Eq. (2.1), we have the following equation:
(∆t)−γ
Γ(2−γ)
n
∑
k=0hun+1−k
m−un−k
mih(k+1)1−γ−k1−γi(2.2)
=1
4h3h3u2n
mun+1
m−u3niun
m+2−2un
m+1+2un
m−1−un
m−2.
2.1.1 Linearization 2
Let us use the Caputo fractional derivative approximation for ∂γu
∂tγ., Crank–Nicolson derivative approximation
and usual finite difference approximation for Uxxx given by
Uxxx '1
2h3un
m+2−2un
m+1+2un
m−1−un
m−2,
in Eq. (1.1) at the nodal point (m,n+1), respectively [12]:
If we use the following linearization technique for the non-linear term U3Uxxx:
U3Uxxx '(Un
m)31
2h3un
m+2−2un
m+1+2un
m−1−un
m−2,
then we have the following system of algebraic equation:
(∆t)−γ
Γ(2−γ)
n
∑
k=0hun+1−k
m−un−k
mih(k+1)1−γ−k1−γi(2.3)
= (Un
m)31
2h3un+1
m+2−2un+1
m+1+2un+1
m−1−un+1
m−2.
Eq. (2.3) can be solved using an approximate algorithm.
2.1.2 Linearization 3
Let us use the Caputo fractional derivative approximation for ∂γu
∂tγand usual finite difference approximation
for Uxxx in Eq. (1.1) at the nodal point (m,n+1)respectively [12]: If we use the following linearization technique
for the nonlinear term U3Uxxx, then we have
U3Uxxx '(Un
m+Un
m+1
2)31
2h3un
m+2−2un
m+1+2un
m−1−un
m−2.
Thus, we get the following system of algebraic equation:.
(∆t)−γ
Γ(2−γ)
n−1
∑
k=0hun−k
m−un−k−1
mih(k+1)1−γ−k1−γi(2.4)
= (Un
m+Un
m+1
2)31
2h3un
m+2−2un
m+1+2un
m−1−un
m−2.
Eq. (2.4)can be solved using an approximate algorithm.
38 J.P. Ruiz-Fernández et al. Applied Mathematics and Nonlinear Sciences 4(2019) 35–42
3 Stability analysis
In this section, we investigate whether this method is stable based on von-Neumann analysis. If the Fourier
method analyzes the stability, then the growth factor of a typical Fourier mode is defined as:
un
m=ξne`mϕ, ` =√−1,(3.1)
where ξnis considered as the amplification factor. First, by substituting the Fourier mode (3.1)into the recur-
rence relationship (2.3), one can obtain
4h3(∆t)−γ
Γ(2−γ)
n−1
∑
k=0h(k+1)1−γ−k1−γihξn−k+1−ξn−kie`mϕ
= (ξne`mϕ)3ξn+1e`(m+2)ϕ−2ξn+1e`(m+1)ϕ+2ξn+1e`(m−1)ϕ−ξn+1e`(m−2)ϕ.(3.2)
Next, if we assume that ξn+1=ζ ξ nand ζ=ζ(ϕ)are independent of time, we can easily obtain the
following expression:
4h3(∆t)−γ
Γ(2−γ)
n−1
∑
k=0h(k+1)1−γ−k1−γihζ−k−3n+1−ξ−k−3ni
=ξe3`mϕe2`ϕ−2e`ϕ+2e−`ϕ−e−2`ϕ.(3.3)
Hence, we get
ξ=X1+iX2
Y1+iY2
,(3.4)
X1=2(∆t)−γ
Γ(2−γ)
n−1
∑
k=0h(k+1)1−γ−k1−γihζ1−3n−k−ζ−3n−ki,
X2=0,
Y1=−24cos2[mγ]sin [mϕ]sin2hϕ
2isin[ϕ] + 8 sin3[mϕ]sin2hϕ
2isin[ϕ],
Y2=−24cos [mγ]sin2[mϕ]sin2hϕ
2isin[ϕ] + 8 cos3[mϕ]sin2hϕ
2isin[ϕ],(3.5)
which shows that
|ζ|=
X1+X2
Y1+Y2
.(3.6)
For the Fourier stability definition and for the examined scheme to be stable, the condition |ξ|≤1 must be
gratified. Therefore, if the following inequality is provided, the schema is unconditionally stable.
X2
1
Y2
1+Y2
2≤1.(3.7)
Other schemes can be studied by following a similar way.
3.1 L2and L∞error norms
The equation of the numerical results was obtained for the test problem used in this study and all computa-
tions have been run on using double precision arithmetic. To show how accurate the results, both the error norm
L2
Numerical Solutions with Linearization Techniques of the Fractional Harry Dym Equation 39
L2=
Uexact −UN
2=sh
N
∑
J=0Uexact
j−(UN)j
2
,
and L∞
L∞=
Uexact −UN
∞=max
jUexact
j−(UN)j,
are going to be computed and presented.
3.2 Test Problem
The analytical solution of the fractional Harry Dym equation is given as follows [11].
u(x,t) = 4−3
2(x+t)2
3
,t≥t0,0≤x≤1.(3.8)
In our computations, for the numerical solution of the test problem three different linearization techniques
have been applied. The values of the error norms L2and L∞have been computed at t=1 for different values of
∆t,h. The comparison of the error norms L2and L∞obtained by the linearization techniques is summarized in
Table 1. As summarized in Table 1, it is obvious that the obtained results using linearization 1 are better than the
obtained results using other linearizations. As shown in Figure 1, one can compare the exact and approximate
solution of the collocation method using four radial basis functions for h=0.01.Similarly, as shown in Figures
2 and 3 the exact and approximate solutions can be compared for linearization 2 and linearization 3 successively.
Table 1 Comparison of the error norms L2and L∞that are obtained using the linearization techniques at t=1,α=0.9
for different values of ∆t,h.
Lin. I Lin. II Lin. III
L2×102L∞×102L2×102L∞×102L2×102L∞×102
4t=h=0.001 0.00002 0.00002 0.00566 0.05664 0.00565 0.05659
4t=h=0.05 0.05254 0.08344 0.64556 0.94172 0.58516 0.84499
4t=h=0.04 0.02957 0.05128 0.50690 0.82106 0.47224 0.76100
4t=h=0.03 0.01418 0.02773 0.36800 0.68391 0.35113 0.65086
4t=h=0.02 0.00506 0.01186 0.23124 0.52313 0.22502 0.50855
4t=h=0.01 0.00088 0.00285 0.10161 0.32318 0.10046 0.31945
4t=h=0.2 2.44568 0.00285 3.12756 3.78842 0.80756 1.29370
4t=h=0.1 3.27620 0.41645 1.31211 1.41287 0.94027 0.94563
4 Conclusions
Finite difference methods based on using three different linearization techniques have been proposed for the
numerical solutions of the fractional Harry Dym equation. In addition, numerical results were obtained by using
three different linearization techniques. The proposed method has been tested on a problem and demonstrated
how effective it is. The error norms L2and L∞have been calculated and given. The third linearization technique,
as shown in Figure 3, yielded better results. Because the third linearization technique gives better results, this
technique can be suggested in the next problems and the situation of the problem should be considered. The
obtained results show that the error norms are sufficiently small during all computer runs. It has been observed
that the considered method is a power numerical scheme to solve the fractional Harry Dym equation.
40 J.P. Ruiz-Fernández et al. Applied Mathematics and Nonlinear Sciences 4(2019) 35–42
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
x
0
0.5
1.0
1.5
2.0
2.5
u(x,t)
0.460 0.473 0.486 0.500
x
1.40
1.45
1.50
1.55
u(x,t)
Exact Solution
Approximate Solution
Fig. 1 Comparison of the exact and approximate solution for linearization 2 at h=0.01
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
x
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
u(x,t)
0.465 0.475 0.485 0.495
x
2.195
2.200
2.205
2.210
2.215
u(x,t)
Exact Solution
Approximate Solution
Fig. 2 Comparison of the exact and approximate solution for linearization 3 at h=0.01
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