Solving Nonlinear Boundary Value Problems Using He′s Polynomials and Padé Approximants
Abstract
We apply He′s polynomials coupled with the diagonal Padé approximants for solving various singular and nonsingular boundary value problems which arise in engineering and applied sciences. The diagonal Padé approximants prove to be very useful for the understanding of physical behavior of the solution. Numerical results reveal the complete reliability of the proposed combination.
1. Introduction
With the rapid development of nonlinear sciences, many analytical and numerical techniques have been developed by various scientists for solving singular and nonsingular initial and boundary value problems which arise in the mathematical modeling of diversified physical problems related to engineering and applied sciences. The application of these problems involves physics, astrophysics, experimental and mathematical physics, nuclear charge in heavy atoms, thermal behavior of a spherical cloud of gas, thermodynamics, population models, chemical kinetics, and fluid mechanics see [1–68] and the references therein. Several techniques [1–68] including decomposition, variational iteration, finite difference, polynomial spline, differential transform, exp-function and homotopy perturbation have been developed for solving such problems. Most of these methods have their inbuilt deficiencies coupled with the major drawback of huge computational work. He [19–24] developed the homotopy perturbation method (HPM) for solving linear, nonlinear, initial and boundary value problems. The homotopy perturbation method was formulated by merging the standard homotopy with perturbation. Recently, Ghorbani and Saberi-Nadjafi [15, 16] introduced He’s polynomials by splitting the nonlinear term and also proved that He’s polynomials are fully compatible with Adomian’s polynomials but are easier to calculate and are more user friendly. The basic motivation of this paper is to apply He’s polynomials coupled with the diagonal Padé approximants for solving singular and nonsingular boundary value problems. The Padé approximants are applied in order to make the work more concise and for the better understanding of the solution behavior. The use of Padé approximants shows real promise in solving boundary value problems in an infinite domain; see [42, 50, 56–59]. It is well known in the literature that polynomials are used to approximate the truncated power series. It was observed [42, 50, 56–59] that polynomials tend to exhibit oscillations that may give an approximation error bounds. Moreover, polynomials can never blow up in a finite plane and this makes the singularities not apparent. To overcome these difficulties, the obtained series is best manipulated by Padé approximants for numerical approximations. Using the power series, isolated from other concepts, is not always useful because the radius of convergence of the series may not contain the two boundaries. It is now well known that Padé approximants [42, 50, 56–59] have the advantage of manipulating the polynomial approximation into rational functions of polynomials. By this manipulation, we gain more information about the mathematical behavior of the solution. In addition, the power series are not useful for large values of x. It is an established fact that power series in isolation are not useful to handle boundary value problems. This can be attributed to the possibility that the radius of convergence may not be sufficiently large to contain the boundaries of the domain. It is therefore essential to combine the series solution with the Padé approximants to provide an effective tool to handle boundary value problems on an infinite or semi-infinite domain. We apply this powerful combination of series solution and Padé approximants for solving a variety of boundary value problems. Precisely the proposed combination is applied on boundary layer problem, unsteady flow of gas through a porous medium, Thomas-Fermi equation, Flierl-Petviashivili (FP) equation, and Blasius problem. It is worth mentioning that Flierl-Petviashivili equation has singularity behavior at x = 0 which is a difficult element in this type of equations. We transform the FP equation to a first-order initial value problem and He’s polynomials are applied to the reformulated first-order initial value problem which leads the solution in terms of transformed variable. The desired series solution is obtained by implementing the inverse transformation. The fact that the proposed algorithm solves nonlinear problems without using Adomian’s polynomials is a clear advantage of this technique over the decomposition method.
2. Homotopy Perturbation Method and He’s Polynomials
3. Padé Approximants
A Padé approximant is the ratio of two polynomials constructed from the coefficients of the Taylor series expansion of a function u(x). The [L/M] Padé approximants to a function y(x) are given by [42, 50, 56–59]
4. Numerical Applications
In this section, we apply He’s polynomials for solving boundary layer problem, unsteady flow of gas through a porous medium, Thomas-Fermi equation, Flierl-Petviashivili equation, and Blasius problem. The powerful Padé approximants are applied for making the work more concise and to get the better understanding of solution behavior.
Example 4.1 (see [51], [59].)Consider the following nonlinear third-order boundary layer problem which appears mostly in the mathematical modeling of physical phenomena in fluid mechanics [51, 59]
Example 4.2 (see [51], [57].)Consider the following nonlinear differential equation which governsthe unsteady flow of gas through a porous medium
n | [2/2] | [3/3] | [4/4] | [5/5] | [6/6] |
---|---|---|---|---|---|
0.2 | −0.3872983347 | −0.3821533832 | −0.3819153845 | −0.3819148088 | −0.3819121854 |
1/3 | −0.5773502692 | −0.5615999244 | −0.5614066588 | −0.5614481405 | −0.561441934 |
0.4 | −0.6451506398 | −0.6397000575 | −0.6389732578 | −0.6389892681 | −0.6389734794 |
0.6 | −0.8407967591 | −0.8393603021 | −0.8396060478 | −0.8395875381 | −0.8396056769 |
0.8 | −1.007983207 | −1.007796981 | −1.007646828 | −1.007646828 | −1.007792100 |
n | α |
---|---|
4 | −2.483954032 |
10 | −4.026385103 |
100 | −12.84334315 |
1000 | −40.65538218 |
5000 | −104.8420672 |
α | B[2/2] = y′(0) | B[3/3] = y′(0) |
---|---|---|
0.1 | −3.556558821 | −1.957208953 |
0.2 | −2.441894334 | −1.786475516 |
0.3 | −1.928338405 | −1.478270843 |
0.4 | −1.606856838 | −1.231801809 |
0.5 | −1.373178096 | −1.025529704 |
0.6 | −1.185519607 | −0.8400346085 |
0.7 | −1.021411309 | −0.6612047893 |
0.8 | −0.8633400217 | −0.4776697286 |
0.9 | −0.6844600642 | −0.2772628386 |
x | ykidder | y[2/2] | y[3/3] |
---|---|---|---|
0.1 | 0.8816588283 | 0.8633060641 | 0.8979167028 |
0.2 | 0.7663076781 | 0.7301262261 | 0.7985228199 |
0.3 | 0.6565379995 | 0.6033054140 | 0.7041129703 |
0.4 | 0.5544024032 | 0.4848898717 | 0.6165037901 |
0.5 | 0.4613650295 | 0.3761603869 | 0.5370533796 |
0.6 | 0.3783109315 | 0.2777311628 | 0.4665625669 |
0.7 | 0.3055976546 | 0.1896843371 | 0.4062426033 |
0.8 | 0.2431325473 | 0.1117105165 | 0.3560801699 |
0.9 | 0.1904623681 | 0.04323673236 | 0.3179966614 |
1.0 | 0.1587689826 | 0.01646750847 | 0.2900255005 |
Padé approximants | Initial slope y′(0) | Error (%) |
---|---|---|
[2/2] | −1.211413729 | 23.71 |
[4/4] | −1.550525919 | 2.36 |
[7/7] | −1.586021037 | 12.9 × 10−2 |
[8/8] | −1.588076820 | 3.66 × 10−4 |
[10/10] | −1.588076779 | 3.64 × 10−4 |
Degree | Roots |
---|---|
[2/2] | −1.5 |
[4/4] | −2.50746 |
[6/6] | −2.390278 |
[8/8] | −2.392214 |
Degree | Roots |
---|---|
[2/2] | −2.0 |
[4/4] | −2.0 |
[6/6] | −2.0 |
[8/8] | −2.0 |
Degree | Roots |
---|---|
[2/2] | 0.0 |
[4/4] | −.2197575908 |
[6/6] | −1.1918424398 |
[8/8] | −1.848997181 |
Example 4.3 (see [56].)Consider the following Thomas-Fermi (T-F) equation [6–13, 17, 31, 33, 34, 54] which arises in the mathematical modeling of various models in physics, astrophysics, solid state physics, nuclear charge in heavy atoms, and applied sciences:
Example 4.4 (see [42].)Consider the generalized variant of the Flierl-Petviashivili equation [37]
n | [8/8] roots | n | [8/8] roots |
---|---|---|---|
1 | −2.392213866 | 7 | −1.000708285 |
2 | −2.0 | 8 | −1.000601615 |
3 | −1.848997181 | 9 | −1.000523005 |
4 | −1.286025892 | 10 | −1.000462636 |
5 | −1.001101141 | 11 | −1.000262137 |
6 | −1.000861533 | n → ∞ | −1.0 |
Example 4.5 (see [58], [59].)Consider the two-dimensional nonlinear inhomogeneous initial boundary value problem for the integro-differential equation related to the Blasius problem
Padé approximant | α |
---|---|
[2/2] | 0.5778502691 |
[3/3] | 0.5163977793 |
[4/4] | 0.5227030798 |
5. Conclusion
In this paper, we applied a reliable combination of He’s polynomials and the diagonal Padé approximants for obtaining approximate solutions of various singular and nonsingular boundary value problems of diversified physical nature. The proposed algorithm is employed without using linearization, discretization, transformation, or restrictive assumptions. The fact that the suggested technique solves nonlinear problems without using Adomian’s polynomials is a clear advantage of this technique over the decomposition method.
Acknowledgment
The author is highly grateful to Brig (R) Qamar Zaman, the Vice Chancellor of HITEC University, Taxila Cantt, Pakistan for providing excellent research environment and facilities.