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Page 1: Analysis of Laminar Flow through a Porous Channel with Velocity … · 2020. 6. 24. · Analysis of Laminar Flow through a Porous Channel with eloVcity Slip di erential equations

Malaysian Journal of Mathematical Sciences 11 (3): 423�439 (2017)

MALAYSIAN JOURNAL OF MATHEMATICAL SCIENCES

Journal homepage: http://einspem.upm.edu.my/journal

Analysis of Laminar Flow through a Porous

Channel with Velocity Slip

Ashwini B., N. N. Katagi ∗ and A. S. Rai

Department of Mathematics, Manipal Institute of Technology,

MAHE, India

E-mail: [email protected]∗Corresponding author

Received: 15 December 2016

Accepted: 15 September 2017

ABSTRACT

The present paper analyses the problem of laminar �ow in a porouschannel with velocity slip using novel Computer Extended Series (CES)and Homotopy Analysis Method (HAM). The semi-numerical schemedescribed here o�er some advantages over solution obtained by usingtraditional methods such as regular perturbation, shooting method etc.These techniques also reveal the analytic structure of the solution func-tion. The objective is to study the in�uence of non-zero tangential slipvelocity on velocity �eld and pressure gradient. Domb-Syke plot andh-curves enable us in obtaining the domain and rate of convergence ofthe series generated, which are further increased by Padé approximants.The solution presented here is valid for much larger Reynolds number fordi�erent derived quantities compared with earlier �ndings by Singh andLaurence (1979).

Keywords: Computer Extended Series, Homotopy Analysis Method,Velocity slip coe�cient, Domb-Syke plot, h−curve.

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Ashwini B., N. N. Katagi and A. S. Rai

1. Introduction

The problem of �uid �ow in channels and tubes have received considerableattention in recent years, owing to its application in biological and engineeringproblems. Berman (1953) was the �rst researcher who studied the problemof steady �ow of an incompressible viscous �uid through a porous channelwith rectangular cross-section, when the Reynolds number is low. Yuan (1956)extended the problem of two dimensional steady state laminar �ow in channelswith porous walls for the case of various values of suction and injection Reynoldsnumbers. Sellars (1955) extended the problem studied by Berman for largepositive Reynolds number.

Later Yuan (1956) extended the same problem for large negative values ofReynolds number. Terrill (1964) extended Berman's problem and obtained amore accurate numerical solution for fourth order non-linear di�erential equa-tion. Following researchers Terrill (1969), Brady (1984), Robinson (1976), Cox(1991), King and Cox (2001) have extended Berman's problem and obtainedthe solution for large values of suction and injection. In the previous analysisof �ow in porous channels majority have used no slip boundary conditions.

The experiments reported by Beavers and Joseph (1967) proved the ex-istence of slip velocity at porous boundaries. The historical background toBeavers-Joseph conditions at the interface of porous media and clear �uid werereported by Nield (2009). Singh and Laurence (1979) obtained analytic ex-pression for the velocity pro�le and pressure drop in the study of laminar �owthrough porous channels for small values of Reynolds number.

In this manuscript we re-investigate the problem of laminar �ow in a porouschannel with velocity slip (Singh and Laurence (1979)). In the present workwe attempt to study the e�ect of non-zero tangential slip coe�cient on thevelocity �eld, pressure gradient using two novel techniques CES and HAM andpresent some useful, interesting results.

In the �rst method, we use Computer extended series (CES) method tosolve the governing equations for moderately large wall Reynolds number Rand generate large number of universal polynomial coe�cient functions us-ing MATHEMATICA and Domb-Syke's plot reveals convergence of the series.Van Dyke (1974, 1975, 1984) pioneered the use of computer extended seriesanalysis in computational �uid dynamics. In an earlier study Bujurke et al.(2005, 1996) also successfully used this method. In the second method, weemployed Homotopy Analysis Method for the solution of governing equation.Liao (1992) proposed the general analytic method for the solution of non-linear

424 Malaysian Journal of Mathematical Sciences

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Analysis of Laminar Flow through a Porous Channel with Velocity Slip

di�erential equations. Siddheshwar (2010) has used this technique to solveGinzburg-Landau Equation with a time periodic coe�cient. HAM providesan e�cient solution with high accuracy and unlike perturbation method it isindependent of very small or large physical parameters. The domain and rateof convergence is found by a proper choice of the auxiliary parameter h usingh−curve. Finally, Padé approximants of various order give converging sum forsu�ciently large Reynolds number.

An outline of the rest of this paper is as follows. In section 2 a briefmathematical formulation of the proposed problem is explained. Section 3is devoted to approximate solution of the problem by Computer Extendedseries and Homotopy analysis method and in section 4, we compare the resultsobtained and discussed the in�uence of slip coe�cient on velocity pro�les andpressure gradient for di�erent Reynolds number.

2. Mathematical Formulation

Consider a laminar �ow of an incompressible viscous �uid between twoplane parallel porous boundaries. It is assumed that the width of the channelis very large relative to height, thus the �ow is assumed to be two dimensionaland steady. We choose a Cartesian coordinate system (x, y) where x axis isin a plane parallel to channel walls and y axis is perpendicular it(Fig.1). Thedistance between wall is taken to be 2h and channel length is L. The �ow issymmetrical about the mid plane of channel of half thickness h. Under the as-sumed condition and choice of axes, the relevant equations of linear momentum(Navier -Stokes equations) and continuity are,

u∂u

∂x+v

h

∂u

∂λ= −1

ρ

∂p

∂x+ v

(∂2u

∂x2+

1

h2∂2u

∂λ2

)(1)

u∂v

∂x+v

h

∂v

∂λ= − 1

ρh

∂p

∂λ+ v

(∂2v

∂x2+

1

h2∂2v

∂λ2

)(2)

∂u

∂x+

1

h

∂v

∂λ= 0 (3)

where λ = yh is the dimensionless variable.

Malaysian Journal of Mathematical Sciences 425

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Ashwini B., N. N. Katagi and A. S. Rai

Porous Boundary

Porous Boundary

𝝀

Figure 1: Schematic diagram of the problem

The requisite boundary conditions are,

u(x,±1) = −k1/2

αh

(∂u

∂λ

),(

∂u

∂λ

)λ=0

= 0,

v(x, 0) = 0,

v(x,±1) = vw = constant.

(4)

The slip coe�cient is given by relation φ = k1/2

αh α is a dimensionless constantwhich depends on the porous membrane and k is permeability. Following theprocedure of Berman (1953), for constant wall velocity vw, a suitable streamfunction ψ is chosen as,

ψ(x, λ) = [hu(0)− vwx] f(λ)

where U(0) is an arbitrary velocity at x = 0.

The velocity components are given by

u(x, λ) =1

h[hu(0)− vwx] f ′(λ) (5)

v(λ) = vwf(λ) (6)

In these equations f(λ), is some function of the distance parameter λ, which isto be determined.

Substituting Eq.(5) and Eq.(6) into the equations of motion Eq.(1) andEq.(2), results in following equations,

−1

ρ

∂p

∂x=

[u(0)− vwx

h

]{−vwh

[f ′2 − ff ′′]− v

h2f ′′′}, (7)

426 Malaysian Journal of Mathematical Sciences

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Analysis of Laminar Flow through a Porous Channel with Velocity Slip

− 1

∂p

∂λ=

v

h

∂v

∂λ− v

h2∂2v

∂λ2. (8)

On eliminating the pressure p and simplifying, we get

d

{−vwh

[f ′2 − ff ′′]− v

h2f ′′′}

= 0.

After di�erentiation, we have,

f ′′′′ +R(f ′f ′′ − ff ′′′) = 0. (9)

The new boundary conditions are

f ′(1) = −φf ′′(1);

f ′′(0) = 0

f(0) = 0;

f(1) = 1.

(10)

Eq.(9) is one of the Falkner-Skan family of equations. Analytical solutions forhomogeneous counterpart of classical Falkner-Skan equation have been foundby many authors Yang and Chien (1975), Brauner et al. (1982), Sachdev et al.(2008), Kudenatti et al. (2017). Eq. (9) along with boundary condition (10)is solved by a �rst order regular perturbation method by Singh and Laurence(1979), which is valid only for small R. This approach fails for any arbitrary R.The proposed series solution o�ers an attractive alternative approach and alsothe terms of this series method are capable of providing results to any desireddegree accuracy for any moderately arbitrary R.

3. Method of Solution

3.1 Computer Extended Series

For the analysis of perturbation series we need su�ciently large number ofcoe�cients in polynomial functions. Manually it is di�cult to calculate beyond�rst order term as it involves complex algebraic calculations. Towards this goal,we consider solution of Eq.(9) in power series of R as,

f(λ) = f0(λ) +

∞∑n=1

Rnfn(λ). (11)

Malaysian Journal of Mathematical Sciences 427

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Ashwini B., N. N. Katagi and A. S. Rai

Substituting (11) in (9) and equating various powers of R on both sides, weget,

f′′′′

n =( n−1∑r=0

frf′′′n−1−r − f ′rf ′′n−1−r

), n = 1, 2, 3, ... (12)

and the relevant boundary conditions are,

f0(1) = 1,

f ′n(1) = −φf ′′n (1),

f ′′n (0) = fn(0) = 0,

fn(1) = 0, for n ≥ 1.

(13)

We solve Eq.(12) recursively using MATHEMATICA and able to generateuniversal polynomial functions (fn(λ), n = 0, 1, 2, 3, . . . , 30) for di�erent valuesof slip coe�cient φ.

The solutions to the above equations, up to the term in R are (Singh andLaurence (1979)):

f0(λ) = − 0.5λ3

3φ+ 1+

3λφ

3φ+ 1+

1.5λ

3φ+ 1,

f1(λ) = −0.0107143λ7φ

(3φ+ 1)3− 0.00357143λ7

(3φ+ 1)3+

0.075λ3φ

(3φ+ 1)3+

0.0107143λ3

(3φ+ 1)3

− 0.0642857λφ

(3φ+ 1)3− 0.00714286λ

(3φ+ 1)3

Velocity pro�les:

From Eq. 5 and 6, expressions for velocity pro�le in the axial and transversedirections are,

U =u

u0=(

1− 4R

Re

x

h

)[f ′0(λ) +

∞∑n=1

Rnf ′n(λ)]

(14)

V =v

vw= f0(λ) +

∞∑n=1

Rnfn(λ) (15)

Also, we have obtained the Normalized axial velocity component as,

us =u

u= f ′(λ) =

[f ′0(λ) +

∞∑n=1

Rnf ′n(λ)]

(16)

428 Malaysian Journal of Mathematical Sciences

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Analysis of Laminar Flow through a Porous Channel with Velocity Slip

For Normalized slip velocity we have,

u0s =(uu

)y=h

(17)

Pressure gradient:

From (5, 6) and (9), an expression for Normalized pressure gradient P alongthe channel length is derived as,

P =−2CPRe

[xh− 2R

Re

(xh

)2](18)

where CP (integrating constant) obtained as,

CP = f ′′′(0) =

∞∑n=0

Rnf ′′′n (0) =

∞∑n=0

Rnan (19)

Coe�cients of the above series (14) and (18) are decreasing in magnitude.We used Domb-Sykes plots to �nd the nature of nearest singularities whichrestricts convergence of the series. Validity of the series is further increased byPadé approximants which gives a converging sum for su�ciently large value ofR.

3.2 Homotopy Analysis Method

To compare the obtained solutions we solve the problem by Homotopy anal-ysis method. All perturbation techniques are based on small parameters so thatat least one unknown must be expressed in a series of small parameters. Unlikeperturbation methods, the HAM is independent of any small physical param-eters. By using HAM we can transfer a non-linear problem into an in�nitenumber of linear sub-problems. The HAM provides a convenient way to guar-antee the convergence of series solution in conjunction with Padé sum, so thatit is valid even if non-linearity becomes rather strong as compared to all otheranalytic methods.

Zeroth-order deformation problem

We seek solution of Eq.(9) by using HAM given by Liao (2004, 2012). Wechoose the base function to express f(λ). The initial guess is written as,

f0(λ) = − λ3

2(3φ+ 1)+

3λφ

3φ+ 1+

2(3φ+ 1)(20)

Malaysian Journal of Mathematical Sciences 429

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Ashwini B., N. N. Katagi and A. S. Rai

and auxiliary linear operator is de�ned as,

L[f ] = f ′′′′ (21)

The above linear operator satisfying the following property,

L[C1λ3

6+ C2

λ2

2+ C3λ+ C4] = 0

where C1, C2, C3 and C4 are constants to be determined. If q ∈ [0, 1] then thezeroth order deformation problem can be constructed as,

(1− q)L[f(n, q)− f0(λ)] = qhH(λ)N [f(λ, q)] (22)

subject to boundary conditions,

f(0, q) = 0

f(1, q) = 1

f ′(1, q) = −φf ′′(1, q)f ′′(0, q) = 0

(23)

where 0 ≤ q ≤ 1 is an embedding parameter, h and H are non-zero auxil-iary parameter and auxiliary function respectively. Further, N is a non-lineardi�erential operator de�ned as,

N [f(λ, q)] =∂4f(λ, q)

∂λ4+R

∂f(λ, q)

∂λ

∂2f(λ, q)

∂λ2−R∂

3f(λ, q)

∂λ3(24)

For q = 0 and q = 1, Eq.(22) has solution,

f(λ, 0) = f0(λ)

f(λ, 1) = f(λ)(25)

As q varies from 0 to 1, f(λ, q) varies from initial guess f0(λ) to exact solutionf(λ). By Taylor's theorem, Eq.(25) can be expressed as

f(λ, q) = f0(λ) +

∞∑m=1

fm(λ)qm (26)

where, fm(λ) = 1m!

∂mf∂qm

∣∣∣∣∣q=0

. Convergence of the above series (26) depends on

the convergence control parameter h, which is chosen in such a way that (26)is convergent at q = 1. Then we have,

f(λ) = f0(λ) +

∞∑m=1

fm(λ) (27)

430 Malaysian Journal of Mathematical Sciences

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Analysis of Laminar Flow through a Porous Channel with Velocity Slip

mth-order deformation problem

Di�erentiating the zeroth order deformation problem equation (22) `m'times with respect to q and lastly setting q = 0. The resulting mth orderdeformation problem becomes,

L[fm(λ)− χmfm−1(λ)] = hH(λ)<m(λ) (28)

and the homogeneous boundary conditions are,

fm(0) = 0, fm(1) = 0, f ′m(1) = −φf ′′m(1), f ′′m(0) = 0 (29)

where

<m(λ) = f ′′′′m−1 +R

m−1∑n=0

[f ′nf′′m−n−1 − fnf ′′′m−n−1] (30)

and

χm =

{0, m ≤ 1

1, m > 1(31)

We used Mathematica software to solve the system of linear equations (28)with appropriate boundary conditions (29) and obtain the solution as follows,

f1(λ) = R

(λ7

(3hφ

280(3φ+ 1)3+

h

280(3φ+ 1)3

)+ λ3

(−

3hφ

40(3φ+ 1)3−

3h

280(3φ+ 1)3

)+λ

(9hφ

140(3φ+ 1)3+

h

140(3φ+ 1)3

)) (32)

f2(λ) = λ11(

3h2R2φ2

30800(3φ+ 1)5+

h2R2

92400(3φ+ 1)5+

h2R2φ

15400(3φ+ 1)5

)+ λ9

(−

3h2R2φ3

560(3φ+ 1)5

−h2R2φ2

160(3φ+ 1)5−

h2R2φ

420(3φ+ 1)5−

h2R2

3360(3φ+ 1)5

)+ λ7

(9h2R2φ2

2800(3φ+ 1)5

+3h2R2φ

1960(3φ+ 1)5+

3h2R2

19600(3φ+ 1)5+

27h2Rφ3

280(3φ+ 1)5+

27h2Rφ2

280(3φ+ 1)5

)+ λ7

(9h2Rφ

280(3φ+ 1)5+

h2R

280(3φ+ 1)5+

27hRφ3

280(3φ+ 1)5+

27hRφ2

280(3φ+ 1)5

+9hRφ

280(3φ+ 1)5+

hR

280(3φ+ 1)5

)+ λ3

(9h2R2φ3

140(3φ+ 1)5+

51h2R2φ2

1400(3φ+ 1)5

+73h2R2φ

7700(3φ+ 1)5+

73h2R2

107800(3φ+ 1)5−

27h2Rφ3

40(3φ+ 1)5−

153h2Rφ2

280(3φ+ 1)5

)+ λ3

(−39h2Rφ

280(3φ+ 1)5−

3h2R

280(3φ+ 1)5−

27hRφ3

40(3φ+ 1)5−

153hRφ2

280(3φ+ 1)5

−39hRφ

280(3φ+ 1)5−

3hR

280(3φ+ 1)5

)+ λ

(−

33h2R2φ3

560(3φ+ 1)5−

2063h2R2φ2

61600(3φ+ 1)5

Malaysian Journal of Mathematical Sciences 431

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Ashwini B., N. N. Katagi and A. S. Rai

−703h2R2φ

80850(3φ+ 1)5−

703h2R2

1293600(3φ+ 1)5+

81h2Rφ3

140(3φ+ 1)5

)+ λ

(9h2Rφ2

20(3φ+ 1)5

+3h2Rφ

28(3φ+ 1)5+

h2R

140(3φ+ 1)5+

81hRφ3

140(3φ+ 1)5+

9hRφ2

20(3φ+ 1)5

+3hRφ

28(3φ+ 1)5+

hR

140(3φ+ 1)5

)(33)

Convergence of HAM

The series (27) contains the auxiliary parameter h which is known as con-vergence control parameter and it in�uences the convergence rate and regionof the series. To ensure that this series converges, we need to choose propervalue for h. To obtain the permissible ranges of the parameter h, h-curves areplotted (Fig. 9).

4. Results and Discussion

The problem of laminar �ow in a channel of porous walls with velocity slip isstudied using two novel semi-numerical and Semi-analytical methods:computerextended series method and Homotopy analysis method (HAM). The motion of�uid is governed by a nonlinear ordinary di�erential equation (9) with boundaryconditions (10).

Using recurrence relation and MATHEMATICA we generate large number(n = 30) of universal polynomial functions fn(λ) for di�erent slip coe�cients φ.This enables one in obtaining large number of universal polynomial functionsfn(λ) for di�erent slip coe�cient φ. The series (14)-(15) representing velocitypro�les are analyzed using Padé approximants for di�erent Reynolds numberR and also the e�ect of slip coe�cient on these pro�les are shown in �gures 3, 4and 6. Domb-Sykes plot (Fig. 2) shows the singularity restricting convergenceof the series representing velocity pro�les.

432 Malaysian Journal of Mathematical Sciences

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Analysis of Laminar Flow through a Porous Channel with Velocity Slip

VELOCITY PROFILE

Radius of Convergence: 12.518, 12.65 and 14.480

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0.2 0.4 0.6 0.8 1

|An|^(1/n)

1/n

φ=0.1 φ=0.3 φ=0.5

Figure 2: Domb-Syke plot for velocity pro�les

Figures 3 and 4 show in�uence of the slip velocity on the channel �ow withsuction and injection. The no slip case corresponds to φ = 0. It is observedthat the slip velocity is more sensitive to changes in the slip coe�cient for smallvalues and seems to approach an asymptotic value for large slip coe�cient, thatis, increasing slip leads to �attening of pro�les and reduced wall shear stresses.Also, increasing suction results in �atter pro�les and velocity pro�les restrictedto thinner boundary layer. Whereas, �uid injection does not result in markedchanges in the velocity pro�les but decreases the wall shear rate. The in�uenceof normalized slip velocity for various values of R are shown in Figure 5, whichshows Us increases with φ and approaches asymptotic values.

VELOCITY PROFILES FOR DIFFERENT VALUES OF REYNOLD’S NUMBER: (For different φ

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 0.2 0.4 0.6 0.8 1

Us

Velocity profiles for R=1 for channel flowλ

φ=0 φ=0.1 φ=0.2 φ=0.3 φ=0.5

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.2 0.4 0.6 0.8 1

Us

λ

Velocity profiles for R=50 for channel flow

φ=0 φ=0.1 φ=0.2 φ=0.3 φ=0.5

Figure 3: Velocity pro�les for channel �ow with suction

Malaysian Journal of Mathematical Sciences 433

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Ashwini B., N. N. Katagi and A. S. Rai

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.2 0.4 0.6 0.8 1

Us

λ

Velocity profiles for R=-5 for channel flow

φ=0 φ=0.1 φ=0.2 φ=0.3 φ=0.5

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.2 0.4 0.6 0.8 1

Us

λ

Velocity profiles for R=-10 for channel flow

φ=0 φ=0.1 φ=0.2 φ=0.3 φ=0.5

Figure 4: Velocity pro�les for channel �ow with injection

EFFECT OF φ ON NORMALIZED SLIP VELOCITY FOR DIFFERENT VALUES OF R

0

0.2

0.4

0.6

0.8

0 0.1 0.2 0.3 0.4 0.5

Us

φ

Effect of slip coefficient on Normalized slip velocity

R=0.1 R=1 R=5 R=10

R=-0.1 R=-1 R=-5 R=-10

Figure 5

Figure 6 is a plot of dimensionless transverse velocity with λ, shows the e�ectof axial slip coe�cient on the mid channel transverse velocity pro�le. Largesuction rate results in linear transverse velocity pro�les whereas injection makeonly small deviations in the shape.

434 Malaysian Journal of Mathematical Sciences

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Analysis of Laminar Flow through a Porous Channel with Velocity Slip

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

V

λ

Transverse Velocity profiles for R=0.1

φ=0 φ=0.1 φ=0.2

φ=0.3 φ=0.4 φ=0.5

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

V

λ

Transverse Velocity profiles for R=50

φ=0 φ=0.1 φ=0.2

φ=0.3 φ=0.4 φ=0.5

Figure 6: The e�ect of slip coe�cient on dimensionless transverse velocity for Re = 1000

PRESSURE GRADIENT

Radius of Convergence: 12.272, 12.406 and 14.24

0

0.5

1

1.5

2

2.5

3

3.5

0 0.2 0.4 0.6 0.8 1

|An|^(1/n)

1/n

φ=0 φ=0.1 φ=0.5

Figure 7: Domb-Syke plot for pressure gradient

The coe�cients an of the series (18) represents the pressure gradient P aredecreasing in magnitude, but have no regular sign pattern. Domb-Syke plot(7) after extrapolation, con�rms the radius of convergence of series (18) to beR = 12.27, 12.40, 14.24 (with an error of 10−5) for di�erent slip coe�cients(φ = 0, 0.1, 0.5) respectively. Direct sum of the series is valid only up to R < 12.We obtained the results of P for su�ciently large R (up to 50) using Padéapproximants (Bender and Orszag (1987)) as compared to earlier �ndings.

Figure 8 shows that the magnitude of pressure gradient P , increases withxh for �xed entrance Re = 1000. Inspection of �gure reveals that the valuesof P decrease with the in�uence of slip coe�cient φ, at the porous wall whichleads to reduction in the shear stress at the membrane surface. This leads tothe fact that, the e�ect of velocity slip at the porous binding wall is to decrease

Malaysian Journal of Mathematical Sciences 435

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Ashwini B., N. N. Katagi and A. S. Rai

magnitude of the pressure gradient. Another interesting trend in evidence inthe graph is that an increase in R will result in decrease of shear stress whichin-turn reduces P .

EFFECT OF φ ON AXIAL PRESSURE GRADIENT FOR DIFFERENT R

0

1

2

3

4

5

6

0 100 200 300 400 500 600 700 800 900 1000

P

x/hEffect of Slip coefficient on axial pressure gradient for R=0.1

φ=0 φ=0.1 φ=0.3 φ=0.5

-900

-800

-700

-600

-500

-400

-300

-200

-100

00 100 200 300 400 500 600 700 800 900 1000

P

x/h

Effect of Slip coefficient on axial pressure gradient for R= 50

φ=0 φ=0.1 φ=0.3 φ=0.5

Figure 8: Variation in pressure gradient as a function of slip coe�cient φ

To con�rm certainty, to validate accuracy and e�ciency of the results ob-tained by Computer extended Series method , the problem is also analyzed byan elegant homotopy analysis method (HAM) in conjunction with Padé sum toaccelerate convergence of the series. We plot h-curves to �nd the convergencerange and also the rate of approximations for the series representing f ′(0) andP when R = 0.1, φ = 0 respectively from 10th order HAM approximations.The range for admissible values of h for di�erent values of R and φ is di�erent.From the �gure 9 it is observed that series representing f ′(0) and f ′′′(1) areconvergent when −2.2 ≤ h ≤ −0.3.

Figure 9: h-curves for 10th order approximations

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Analysis of Laminar Flow through a Porous Channel with Velocity Slip

5. Concluding Remarks

In the present work, we employed two semi-numerical methods, known asComputer Extended Series method and Homotopy Analysis Method to solvefourth order non-linear di�erential equation modeling laminar �ow throughporous channels. The e�ect of non-zero tangential slip velocity on velocity �eldand pressure gradient are analyzed. The study con�rms that the proposedmethods converges to the solution for moderately large values of Reynolds num-ber as compared to the earlier �ndings. The results obtained were comparedand an excellent agreement was observed.

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