Research Article  Open Access
Improved Analysis for Squeezing of Newtonian Material between Two Circular Plates
Abstract
This article presents a scheme for the analysis of an unsteady axisymmetric flow of incompressible Newtonian material in the form of liquid squeezed between two circular plates. The scheme combines traditional perturbation technique with homotopy using an adaptation of the Laplace Transform. The proposed method is tested against other schemes such as the Regular Perturbation Method (RPM), Homotopy Perturbation Method (HPM), Optimal Homotopy Asymptotic Method (OHAM), and the fourthorder Explicit RungeKutta Method (ERK4). Comparison of the solutions along with absolute residual errors confirms that the proposed scheme surpasses HPM, OHAM, RPM, and ERK4 in terms of accuracy. The article also investigates the effect of Reynolds number on the velocity profile and pressure variation graphically.
1. Introduction
The study of squeezing flows has significant applications in the areas of engineering, physics, biology, and material sciences. In the past few years, the study of rheometric properties of fluids has garnered significant attention due to its vast industrial applications. Examples include modelling of lubrication systems involved in squeezing of fluids [1â€“3], compression moulding processes of metals and polymers [4], injection moulding processes, polymer processes [5], hydrodynamical tools and machines, modelling of chewing and eating [6], and modelling of the functions of heart valves and blood vessels. Many of these applications involve the adjustment of rheometric properties using external stimuli such as electric and magnetic fields. For instance, electrorheological fluids (micron size polymer particles in silicon) may solidify or become extremely viscous under an electric field. The same can be said about magnetorheological fluids involving magnetic particles. Under an applied external field, these particles remain suspended due to which fluid particles are not able to exhibit Brownian motion. As a result, the fluid can adopt viscous properties.
Traditional approaches to study flow patterns involve the configuration of two plates of radius that are separated by a narrow gap . Three modes of operations on the plates are commonly used; stationary plates resulting in Poiseuille flow, shear mode resulting in Couette flow, and squeeze mode resulting in compressed flow. Some properties of the flow such as mass and momentum are not affected by deformations due to these operations and they remain conserved. The resulting set of properties such as velocity and pressure can be modelled as various boundary value problems. Some configurations may also focus on the interaction between the samples and the plates. The interactions can result in different types of stresses identified as slip, noslip, or partial slip. Other configurations may also focus on types of fluid such as viscous, plastics (or viscoplastics), and elastic (or viscoelastic) fluids.
The solutions to these different configurations and boundary value problems can be obtained using well known analytical [7â€“14] and numerical schemes [15, 16]. The most common approach involves the usage of perturbation techniques that assume small or large parameters, which may affect the solutions in different scenarios. To overcome this limitation, a method known as the Homotopy Perturbation Method was introduced that combined traditional perturbations with homotopy and was applied to various nonlinear boundary value problems [7, 8, 17â€“19]. Some modifications and extensions to the method have also appeared. Examples include that of dynamical systems of rotating machines [20], nonlinear differential equations [21], singular laneembed equations [22], Cauchy reaction diffusion equation [23], nonlinear undamped oscillators [24], and fractional differential equations [25].
In this article, we present a detailed analysis of squeezing flow of Newtonian fluids using an improved alteration of the Homotopy Perturbation Method with Laplace Transform. We refer to this alteration as HPLM, that is, Homotopy Perturbation Laplace Method. To check the effectiveness of the proposed scheme, a comparison is performed with Regular Perturbation Method (RPM), Homotopy Perturbation Method (HPM), RungeKutta (Explicit) method of fourthorder, and Optimal Homotopy Asymptotic Method (OHAM). Moreover, the effect of Reynolds number on the velocity profile and pressure variation is studied graphically.
2. Mathematical Formulation
The formulation is based on an unsteady squeezing flow of an incompressible Newtonian fluid bearing kinematic viscosity , density , and viscosity . The fluid is squeezed between a pair of circular plates that are at a distance of . The plates operate in a squeezing mode where the plate velocity is . A 2D configuration of squeezing flow in plane is in Figure 1, where the plates move perpendicular to the central axis . With this operation, an axisymmetric behaviour is observed in the flow about . The velocity components (normal and longitudinal) in axial and radial directions are and . The governing equations areTwo kinds of boundary conditions are placed for the velocity components of the fluid. The first is due to noslip at the upper plate, while the second is due to symmetry.By introducing the dimensionless parameter , (1), (2), and (3) are transformed towhere the boundary conditions areAfter eliminating the generalized pressure between (6) and (7), the following is obtained:where is the Laplacian operator.
Defining velocity components as [4](5) is identically satisfied, while (9) becomeswhereIntegrating first equation of (12) giveswhere and are constants affecting the directional movement of the plates. From (12) and (13), it follows that . Now, (11) becomesUsing (8) and (10), the boundary conditions in case of noslip at the upper plate areFurthermore, using (10) in (3) and integrating with respect to while keeping fixed, the variation of pressure iswhere is the pressure at . Similarly, using (10) in (2) and integrating with respect to while keeping fixed lead to the pressure distribution.
3. Basic Theory of HPLM
The basic concept of HPLM can be understood by applying it to the following differential equation:where and are linear and nonlinear operators, while and are known and unknown functions. According to HPLM, a homotopy can be constructed as such that it satisfieswhere is an embedding parameter while . Expanding using a Taylor series about , we obtain an approximate solution:Various order problems can be obtained by substituting (19) into (18) and equating with the coefficients of . The zerothorder problem would beApplying Laplace Transform to (20) givesApplication of the inverse Laplace Transform to (21) givesThe general th order problem would beApplying Laplace Transform to (23)Application of the inverse Laplace Transform to (24) givesUsing the boundary conditions, the approximate solution will beSubstituting (26) into (17), the expression for residual can be obtained as The approach defined in this section minimizes the limitations of the ordinary perturbation methods and, in contrast, can take full advantage of the traditional perturbation techniques.
4. Application of HPLM
Using (11) and (15), various order problems are presented with their solutions in this section. The zerothorder problem iswith boundary conditions , , , and . The solution to (28) is given as
The firstorder problem isFor (30) and the rest of higher order problems , the boundary conditions are set as , , , and , where . The solution to (30) is given as
The secondorder problem isfor which the solution is given as
The thirdorder problem isfor which the solution is given as
The fourthorder problem isto which the solution is given as
In a similar way, higher order problems solutions can be obtained. Considering the fourthorder solution,The use of boundary conditions gives the values of unknown constants and for fixed values of in (38). For , , and , the solution is represented as follows:
The residual error of the problem is
5. Results and Discussion
In this article, an unsteady axisymmetric flow of incompressible Newtonian fluid squeezed between two circular plates is considered. The resulting nonlinear boundary value problem is solved analytically with HPLM and HPM and numerically with ERK4.
Tables 1, 2, and 3 present the comparison of ERK4, HPM, OHAM, and HPLM solutions along with absolute residual errors for fixed values of . These tables indicate that results from the proposed scheme are in good agreement with ERK4. Furthermore, Table 4 represents the comparison of RPM and HPLM solutions and residual errors for fixed values of . All the tables demonstrate that results obtained using HPLM are better in terms of accuracy as compared to other stated schemes. In addition to the abovementioned tables, Table 5 shows various order solutions along with absolute residual errors and confirms the convergence of HPLM solution. Moreover, Table 6 indicates the comparison of HPLM solution with numerical (ERK4) solutions. It shows that HPLM results are in very good agreement with ERK4.


