Muhammet Yürüsoy

Approximate analytical solutions for the flow of a third-grade fluid in a pipe

Abstract The flow of a third-grade fluid in a pipe with heat transfer is considered. Constant viscosity, Reynolds model viscosity and Vogels model viscosity cases are treated separately. Approximate analytical solutions are presented for each case using perturbations. The criteria for which the solutions are valid are determined for the dimensionless parameters involved. The analytical solutions are contrasted with the finite difference solutions given in Massoudi and Christie (Int. J. Non-Linear Mech. 30 (1995) 687–699) and within admissible parameter range, a close match is achieved.

Lie group analysis of creeping flow of a second grade fluid

The two-dimensional equations of motion for the slowly flowing second grade fluid are written in cartesian coordinates neglecting the inertial terms. By employing Lie group analysis, the symmetries of the equations are calculated. The Lie algebra consists of four finite parameter Lie group transformations, one being the scaling symmetry and the others being translations. Two different types of solutions are found using the symmetries. Using the translations in x and y coordinates, an exponential type of exact solution is constructed. For the scaling symmetry, the outcoming ordinary differential equations are more involved and only a series type of approximate solution is presented. Finally, some boundary value problems are discussed.

Similarity Transformations for Partial Differential Equations

The importance of similarity transformations and their applications to partial differential equations is discussed. The theory has been presented in a simple manner so that it would be beneficial at the undergraduate level. Special group transformations useful for producing similarity solutions are investigated. Scaling, translation, and the spiral group of transformations are applied to well-known problems in mathematical physics, such as the boundary layer equations, the wave equation, and the heat conduction equation. Finally, a new transformation including the mentioned transformations as its special cases is also proposed.

SYMMETRY REDUCTIONS OF UNSTEADY THREE- DIMENSIONAL BOUNDARY LAYERS OF SOME NON-NEWTONIAN FLUIDS

Three-dimensional, unsteady, laminar boundary layer equations of a general model of non-Newtonian fluids are treated. In this model, the shear stresses are considered to be arbitrary functions of velocity gradients. Using Lie Group analysis, the infinitesimal generators accepted by the equations are calculated for the arbitrary shear stress case. The extension of the Lie algebra, for the case of Newtonian fluids, is also presented. A general boundary value problem modeling the flow over a moving surface with suction or injection is considered. The restrictions imposed by the boundary conditions on the generators are calculated. Assuming all flow quantities to be independent of the z-direction, the three-independent-variable partial differential system is converted first into a two-independent-variable system by using two different subgroups of the general group. Lie Group analysis is further applied to the resulting equations, and final reductions to ordinary differential systems are obtained.

Comparison of Approximate Symmetry Methods for Differential Equations

Two current approximate symmetry methods and a modified new one are contrasted. Approximate symmetries of potential Burgers equation and non-Newtonian creeping flow equations are calculated using different methods. Approximate solutions corresponding to the approximate symmetries are derived for each method. Symmetries and solutions are compared and advantages and disadvantages of each method are discussed in detail.

Entropy Analysis for Non-Newtonian Fluid Flow in Annular Pipe: Constant Viscosity Case

In the present study, non-Newtonian flow in annular pipe is considered. The analytical solution for velocity and temperature fields is presented while entropy generation due to fluid friction and heat transfer is formulated. The third grade fluid with constant properties is accommodated in the analysis. It is found that reducing non-Newtonian parameter increases maximum velocity magnitude and maximum temperature in the annular pipe. Total entropy generation number attains high values in the region close to the inner wall of the annular pipe, which becomes significant for low non-Newtonian parameters. Increasing Brinkman number enhances entropy generation number, particularly in the region close to the annular pipe inner wall.

Similarity solutions for creeping flow and heat transfer in second grade fluids

Abstract The two-dimensional equations of motions for the slowly flowing and heat transfer in second grade fluid are written in cartesian coordinates neglecting the inertial terms. When the inertia terms are simply omitted from the equations of motions the resulting solutions are valid approximately for Re ⪡1. This fact can also be deduced from the dimensionless form of the momentum and energy equations. By employing Lie group analysis, the symmetries of the equations are calculated. The Lie algebra consist of four finite parameter and one infinite parameter Lie group transformations, one being the scaling symmetry and the others being translations. Two different types of solutions are found using the symmetries. Using translations in x and y coordinates, an exponential type of exact solution is presented. For the scaling symmetry, the outcoming ordinary differential equations are more involved and only a series type of approximate solution is presented. Finally, some boundary value problems are discussed.

Group classification of a non-Newtonian fluid model using classical approach and equivalence transformations

Abstract Boundary layer equations of a non-Newtonian fluid model in which the shear stress is an arbitrary function of the velocity gradient is considered. Group classification of the equations with respect to shear stress is done using two different approaches: (1) classical theory and (2) equivalence transformations. Both approaches yield identical results. It is found that the principle Lie algebra extends only for cases of Newtonian and Power-Law flows.

Symmetry groups of boundary layer equations of a class of non-Newtonian fluids

Abstract A non-Newtonian fluid model in which the stress is an arbitrary function of the symmetric part of the velocity gradient is considered. Symmetry groups of the two-dimensional boundary layer equations of the model are found by using exterior calculus. The complete isovector field corresponding to some cases, such as arbitrary shear function, Newtonian fluids, and powerlaw fluids, are found. Similarly, solutions for some special transformations are presented. Results obtained in a previous paper [M. Pakdemirli, Int. J. Non-Linear Mech. 29, 187 (1994)] using special groups of transformations (scaling, spiral) are verified in this study using a general approach.

Perturbation solution for a third-grade fluid flowing between parallel plates

The flow of non-Newtonian fluid in between two parallel plates at different temperatures is considered. A third-grade fluid with temperature-dependent viscosity is considered in the analysis and the Reynolds model used to account for it. Approximate analytical solutions for the velocity and temperature profiles are found using perturbation techniques. It is found that the influence of the non-Newtonian parameter and viscosity index is more pronounced in the region of the plate surfaces where the rate of fluid strain and temperature gradients are high.