ORIGINAL PAPER Hydromagnetic transport of iron nanoparticle aggregates suspended in water M Marin 1 * , M M Maskeen 2 , A Zeeshan 2 , O U Mehmood 3 and M Hassan 4 1 Department of Mathematics and Computer Science, Transilvania University of Brasov, 500188 Brasov, Romania 2 Department of Mathematics and Statistics, International Islamic University, Islamabad 44000, Pakistan 3 Department of Mathematics, COMSATS Institute of Information Technology, Wah Cantt 47040, Pakistan 4 Department of Mathematics, COMSATS Institute of Information Technology, Lahore 54000, Pakistan Received: 09 December 2017 / Accepted: 03 May 2018 Abstract: The current communication is reports about the transport phenomenon of iron metal (Fe) nanoparticle aggre- gates in water under the impact of an external imposed magnetic field over a stretching cylinder. The governed problem modeled using nonlinear coupled ordinary differential equations which are then tackled by the Mathematica software package bvph 2.0 based on the homotopy scheme. The impact of chemical dimension (d l ), fractal dimension (d f ) and radius of gyration (R g ) on flow and temperature profiles are presented through graphs. Numerical results are computed for the skin friction coefficient and heat transfer coefficients corresponding to the sundry parameters. It is concluded from the results that by increasing the number of particles in the back bone the heat transfer rate is improved, while by increasing the dead end particles the wall shear stress is improved but the heat transfer rate is decreased. Keywords: Particles aggregates; Nanofluid; Stretching cylinder; MHD PACS Nos.: 51.30.?i; 51.35.?a; 81.10.Bk List of symbols e Aspect ratio of the ellipsoid (–) d l Chemical dimensions (–) u, v Velocity in x and r direction (ms -1 ) e Curvature parameter (–) q Density (kg m -3 ) T Dimensional temperature (K) h Dimensionless temperature (–) f 0 Dimensionless velocity (–) l Dynamic viscosity (kg m -1 s -1 ) Ec Eckert number (–) d f Fractal dimensions (–) M 11 , M 33 Geometrical factors (–) Gr Grashof number (–) q Heat flux (J s -1 ) A k Kapitza radius (m) m Kinematic viscosity (m 2 s -1 ) B 0 Magnetic field strength (T) M Magnetic number (–) r Magnetic permeability (NA -2 ) k Mixed convection parameter (–) / int Nanoparticles volume fraction within an aggregate (–) / Nanoparticles volume fraction (–) N int Number of particles within an aggregate (–) N Number of particles (–) Nu Nusselt number (–) Pr Prandtl number (–) R g Radius of gyration (m) a  Radius of primary particle (m) Re Reynolds number (–) s Shear stress (kg s -2 m -1 ) g Similarity variable (–) C f Skin friction coefficient (–) c p Heat capacity (m 2 s -2 K -1 ) b Stretching rate (s -1 ) k Thermal conductivity (W m -1 K -1 ) b Thermal expansion coefficient (K -1 ) / Volume fraction of nanoparticles (–) U w Wall velocity (ms -1 ) *Corresponding author, E-mail: m.marin@unitbv.ro Indian J Phys https://doi.org/10.1007/s12648-018-1259-4 Ó 2018 IACS