ORIGINAL PAPER Transverse transport of Fe 3 O 4 –H 2 O with viscosity variation under pure internal heating R Mehmood* and R Tabassum Department of Mathematics, Faculty of Natural Sciences, HITEC University, Taxila Cantt, Pakistan Received: 29 November 2017 / Accepted: 02 February 2018 Abstract: Smart fluids are the fluids whose properties can be changed by applying an electric or a magnetic field. Such type of fluid finds tremendous applications in electronic devices, semi-active dampers, magnetic resonance imaging, in space craft propulsion and many more. This communication addresses water based magneto ferrofluid striking at a stretching surface in an oblique manner. In order to present physically realistic analysis, viscosity is assumed to be dependent upon temperature as well as volume fraction of magnetite nanoparticle. The flow governing problem is altered into nonlinear coupled system of ordinary differential equations via scaling transformation which is then solved numer- ically by means of Runge–kutta Fehlberg scheme. Impact of sundry parameters such as magnetic field parameter, nanoparticle volume fraction, heat generation parameter and variable viscosity parameter on velocity and temperature profile of magneto ferrofluid is presented graphically and discussed in a physical manner. Practical measures of interest namely skin friction and heat flux at the surface are computed. Streamline patterns are traced out to examine the flow pattern. It is found that skin friction and rate of heat transfer at the wall enhances by strengthening the applied magnetic field. Local heat flux can also be enhanced with increasing the volume fraction of magnetite nanoparticles. Keywords: Magneto nanoparticles; Variable viscosity; Transverse flow; Internal heating PACS Nos.: 47.63.-b; 47.15.G-; 75.75.Fk 1. Introduction Smart fluids are the fluids whose properties can be changed by applying an electric or a magnetic field. Such fluids are having tremendous latent applications in engineering, medical and industrial appliances such as bearings, lasers, pumps, fiber optics, X-ray machines and many more. Fer- rofluid is a liquid that becomes strongly magnetized in the presence of a magnetic field. Ferro fluids are commonly used in voice coils, semi-active dampers, as contrast agents in magnetic resonance imaging, for magnetic hyperthermia and in telescopes. It is a well-known fact that boundary layer phenomenon is significantly influenced by the inter- action of an externally applied magnetic field with elec- trically conducting fluid. Plasma flows and liquid metals are controlled by applying transverse magnetic field. Keeping in view all these salient features, numerous scientists and researchers have devoted their attention on magneto fluids. Shima [1] computed that heat transfer and flow rate can be delimited by controlling the thermo- magnetic convection current. Shankar [2] examined the stagnation flow influenced by magnetic field and heat transfer in a nanofluid and noticed that rise in velocity ratio parameter leads to an increase in Nusselt number, skin friction and Sherwood number. They also observed increase in heat transmit rate at the surface with magnetic field strength. Insertion of nanometer size particles within traditional base fluids having poor thermal conductivity is a common practice in several industrial, technological and manufacturing processes. These tiny nanoparticles with much greater thermal conductivity compare to base fluids make them highly effective heat transfer agents. The problem of fluid over a stretching sheet has been a topic of global interest for quite some time now due to its useful- ness in numerous fields such as paper production, polymer processing, dye roller and many more. In some cases fluid meets the wall at an orthogonal angle but in most of the cases it strikes the wall at any angle. This makes the *Corresponding author, E-mail: rashid.mehmood@hitecuni.edu.pk Indian J Phys https://doi.org/10.1007/s12648-018-1206-4 Ó 2018 IACS