1 ANALYSIS OF ENTROPY GENERATION MINIMIZATION (EGM) IN FLOW OF REE- EYRING NANOFLUID BETWEEN TWO COAXIALLY ROTATING DISKS Muhammad Ijaz KHAN *1 , Riaz MUHAMMAD 2 , Sumaira QAYYUM 1 , Niaz B. KHAN 3 , M. JAMEEL 4 1 Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000, Pakistan 2 Mechanical Engineering Department College of Engineering, University of Bahrain, Bahrain 3 School of Mechanical and Manufacturing Engineering, National University of Sciences and Technology, Islamabad, Pakistan 4 Department of Civil Engineering, College of Engineering, King Khalid University, Abha, Saudi Arabia * Corresponding author; E-mail: mikhan@math.qau.edu.pk The present communication addresses MHD radiative nanomaterial flow of Ree-Eying fluid between two coaxially rotating disks. Both disks are stretchable. Buongiorno model is used for nanofluids. Nanofluid aspects comprise random motion of particles (Brownian diffusion) and thermophoresis. MHD fluid is considered. Furthermore, dissipation, radiative heat flux and Ohmic heating effects are considered to model the energy equation. Total entropy rate is calculated through implementation of second thermodynamics law. Series solutions are developed through homotopy analysis method. Impacts of physical parameters on the velocity, temperature, entropy and concentration fields are discussed graphically. Skin friction coefficient and heat and mass transfer rates are numerically calculated through Tables 2-4. It is noticed that the velocity of liquid particles decreases versus higher estimations of magnetic parameter while it enhances via larger rotational parameter. Temperature field significantly increases in the presence of both Brownian diffusion and thermophoresis parameters. Key words: stretchable rotating disks; Entropy generation; MHD Ree-Eyring nanofluid; Brownian and thermophoresis diffusion effects; Thermal radiation and Ohmic heating. 1. Introduction Several valuable utilizations in biological, engineering, physical and other disciplines stimulated the scientific commune towards the dynamics of non-Newtonian liquids. Such natured liquids nowadays are acknowledged more apposite for technological and scientific exhibitions in comparison to Newtonian liquids. The printing ink, shampoos, emulsions, glues, paints, muds, condensed milk, melts, sugar solution, tomato paste, soaps are a few non-Newtonian type materials. The salient aspects of such materials are problematic to describe as a solo mathematical expression but numerous attempts have been reported by modern researchers to elaborate the rheological aspects of liquids comprising non-Newtonian nature. It is apparent that liquids with non-Newtonian nature are more convoluted and possess extremely non-linear nature. The researchers elaborated numerous models to express the convoluted natured non-Newtonian liquids. Here we have used the Ree-Eyring fluid to investigate the flow between two stretchable rotating disks. The idea about Ree-Eyring fluid was gave by the following researchers [1-3].