Preface

*"A teacher can never truly teach unless he is still learning himself. A lamp can never light another lamp unless it continues to burn its own flame. The teacher who has come to the end of his subject, who has no living traffic with his knowledge but merely repeats his lessons to his students, can only load their minds; he cannot quicken them."* 

—Rabindranath Tagore

 In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that de‐ scribes the flow of fluids, liquids, and gases. It has several subdisciplines, including aerody‐ namics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modeling fis‐ sion weapon detonation. In this book, we provide readers with the fundamentals of fluid flow problems. Specifically, Newtonian, non-Newtonian and nanofluids are discussed. Sev‐ eral methods exist to investigate such flow problems. This book introduces the applications of new, exact, numerical and semianalytical methods for such problems. The book also dis‐ cusses different models for the simulation of fluid flow.

 **Chapter 1** is an introductory chapter, providing a brief discussion of fluid flow problems and their application in society.

 **Chapter 2** is a brief description of existing viscoelastic models, starting with the classical differential and integral models, and then focusing on new models that take advantage of the enhanced properties of the Mittag–Leffler function (a generalization of the exponential function). The generalized models considered in this work are the fractional Kaye–Bern‐ stein, Kearsley, Zapas integral model and the differential generalized exponential Phan-Thien and Tanner (PTT) model. The integral model makes use of the relaxation function obtained from a step-strain applied to the fractional Maxwell model, and the differential modelgeneralizes thefamiliar exponential-PTT constitutive equation by substitutingthe ex‐ ponential function of the trace of the stress tensor by the Mittag–Leffler function.

 In **Chapter 3**, a magnetohydrodynamic flow of a viscous and conducting fluid confined be‐ tween two parallel differentially moving boundaries is considered. The whole system is in a strong magnetic field chosen in such a way that the Hartmann boundary layers that form in this problem become singular at the points where the magnetic field becomes tangent to the boundary. Two geometries are taken into account: plane and spherical. Within the class of such configurations the velocity field of the fluid and the influence of the conductivity of the boundaries on the fluid's motion are reviewed here.

 The aim of the study in **Chapter 4** is to coat a stretching cylinder with the help of a liquid film spray. Casson fluid has been chosen for the coating phenomena. The thickness of the liquid film has been used variably and the influence of heat and mass transmission under the impact of thermophoresis has been encountered in the flow field. The required pressure term for the spray pattern during variable thickness is the main focus. Using suitable simi‐ larity transformations the basic flow equations for fluid motion have been converted into high-order non-linear coupled differential equations. A series of solutions to subsequent problem have been obtained using a controlling procedure optimal approach.

 The relationship of compressive behavior according to manufacturing process parameters of GeoNet is investigated in **Chapter 5**. The drainage behavior of the bi-and triplane GeoNet used for planar drainage analyzed and investigated the changes of the drainage behavior due to the restraining load. The data showed that there is no critical manufacturing factor that affects the compressive strength of the biplanar GeoNet. All of these parameters are affected in a very complicated way. The strand inclination mainly affects the after-compres‐ sive strength, i.e. roll-over behavior. The results considering site-specific conditions of the landfill system explain that temperature has an influence on the compressive behavior of the GeoNet. Compressive strength was reduced and the strain at yield increased gradually with temperature for both bi- and triplanar GeoNets.

 This text is suitable for senior undergraduate students, postgraduate students, engineers, and scientists.

 I am grateful to many friends, colleagues, and students around the world who offered their suggestions and help at various stages of the preparation of the book. I express my sincere thanks to my student Mr. Nadeem Ahmad Sheikh, lecturer at City University of Science and IT, Peshawar, for making this project successful. In spite of the best efforts of everyone in‐ volved, some typographical errors doubtless remain. Finally, I wish to express my special thanks to the staff of IntechOpen for their help and cooperation.

> **Dr. Farhad Ali**  Head of Department of Mathematics City University of Science and Information Technology Peshawar, Pakistan
