Ferrofluids, semi-dilute suspensions of magnetic nanoparticles, are fascinating practically relevant examples of fluids that can be manipulated by magnetic fields. Although ferrofluids have been known since the 1960s, there is still much that is not known in terms of their governing equations, limiting our ability engineer novel applications. Our group has made fundamental contributions to this field through a combination of experimental, theoretical, and simulation approaches. This work led to the demonstration that the description of ferrofluid flows in rotating magnetic fields requires consideration of transport of angular momentum through the so-called couple stress and spin viscosity. Our group was the first to experimentally demonstrate the existence of the spin viscosity and to measure its value for ferrofluids. We have also developed simulation methods to test continuum-level phenomenological models in ways that are currently not possible through experiments.

Related Publications:

• Arlex Chaves-Guerrero, Victor A. Peña-Cruz, Carlos Rinaldi, and David Fuentes-Diaz, “Spin-up Flow of Ferrofluids in Non-Small Magnetic Fields: Numerical Evaluation of the predictions of the common magnetization relaxation equations.” Physics of Fluids, 29:073102, 2017. [http://doi.org/10.1063/1.4993471]
• Bhumika Sule^G, Isaac Torres-Díaz^P, and Carlos Rinaldi, “Flow driven at a ferrofluid/ferrofluid interface due to a rotating magnetic field.” Physics of Fluids, 27(7):073303,2015. [http://doi.org/10.1063/1.4923749]
• Arlex Chaves and Carlos Rinaldi, “Interfacial Stress Balances in Structured Continua and Free Surface Flows in Ferrofluids.” Physics of Fluids, 26:042101, 2014. [http://doi.org/10.1063/1.4869856]
• Isaac Torres-Díaz^P and Carlos Rinaldi, “Recent Progress in Ferrofluids Research: Novel applications of magnetically controllable and tunable fluids.” Soft Matter, 10(43):8584-8602, 2014. [http://doi.org/10.1039/C4SM01308E]
• Isaac Torres-Díaz^G, Angelie Cortes^U, Yarilyn Cedeño-Mattei, Oscar Perales-Perez, and Carlos Rinaldi, “Flows and torques in Brownian ferrofluids subjected to rotating uniform magnetic fields in a cylindrical and annular geometry.” Physics of Fluids, 26:012004, 2014. [http://doi.org/10.1063/1.4863201]
• Darlene I. Santiago-Quiñonez^G, K. Raj, and Carlos Rinaldi, “A Comparison of the Magnetorheology of Two Ferrofluids with Different Magnetic Field Dependent Aggregation Behavior.” Rheologica Acta, 52(8):719-726, 2013. [http://doi.org/10.1007/s00397-013-0715-5]
• Isaac Torres-Díaz^G and Carlos Rinaldi, “Ferrofluid flow in a spherical cavity under an imposed uniform rotating magnetic field: Spherical spin-up flow.” Physics of Fluids, 24:082002, 2012. [http://doi.org/10.1063/1.4734345]
• Isaac Torres-Díaz,^G Carlos Rinaldi, S. Khushrushahi, and Markus Zahn, “Observations of ferrofluid flow under a uniform rotating magnetic field in a spherical cavity.” Journal of Applied Physics, 111:07B313, 2012. [http://doi.org/10.1063/1.3675153]
• Darlene I. Santiago-Quiñonez^G and Carlos Rinaldi, “Enhanced rheological properties of dilute suspensions of magnetic nanoparticles in amphiphilic concentrated surfactant solutions.” Soft Matter, 8:5327-5333, 2012. [http://doi.org/10.1039/C2SM07221A]
• Denisse Soto-Aquino,^G Diego J. Rosso,^U and Carlos Rinaldi, “Oscillatory shear response of dilute ferrofluids: Predictions from rotational Brownian dynamics and ferrohydrodynamics modeling.” Physical Review E, 84: 056306, 2011. [http://doi.org/10.1103/PhysRevE.84.056306]
• Isaac Torres-Díaz^G and Carlos Rinaldi, “Ferrofluid flow in the annular gap due of a multipole rotating magnetic field.” Physics of Fluids, 23:082001, 2011. [http://doi.org/10.1063/1.3611027] This article was highlighted in the Virtual Journal of Nanoscale Science and Technology, Vol. 24, Issue 7, August 15, 2011.
• Denisse Soto-Aquino^G and Carlos Rinaldi, “Transient magneviscosity of dilute ferrofluids,” Journal of Magnetism and Magnetic Materials, 323:1319-1323, 2011. [http://doi.org/10.1016/j.jmmm.2010.11.038]
• Denisse Soto-Aquino^G and Carlos Rinaldi, “Magnetoviscosity in dilute ferrofluids from rotational Brownian dynamics simulations.” Physical Review E, 82(4):046310, 2010. [http://doi.org/10.1103/PhysRevE.82.046310]
• Arlex Chaves^G, Isaac Torres-Díaz^G, and Carlos Rinaldi, “Flow of a ferrofluid in an annular gap in a rotating magnetic field.” Physics of Fluids, 22:092002, 2010. [http://doi.org/10.1063/1.3483598]
• Jorge H. Sánchez^G and Carlos Rinaldi, “Magnetoviscosity of dilute magnetic fluids in oscillating and rotating magnetic fields.” Physics of Fluids, 22:043304, 2010. [http://doi.org/10.1063/1.3370119]
• Carlos Rinaldi, “An invariant general solution for the magnetic fields within and surrounding a small spherical particle in an imposed arbitrary magnetic field and the resulting magnetic force and couple.” Chemical Engineering Communications, special issue in honor of Prof. Howard Brenner, 197:92-111, 2010. [http://doi.org/10.1080/00986440903285621]
• Darlene I. Santiago^G, Aldo Acevedo, and Carlos Rinaldi, “Magnetic and magnetorheological characterization of a polymer liquid crystal ferronematic.” Journal of Applied Physics, 105:07B512, 2009. [http://doi.org/10.1063/1.3056575]
• Jorge H. Sánchez^G and Carlos Rinaldi, “Magnetoviscosity of dilute suspensions of magnetic ellipsoids obtained through rotational Brownian dynamics simulations.” Journal of Colloid and Interface Science, 331:500-506, 2009. [http://doi.org/10.1016/j.jcis.2008.11.061]
• Arlex Chaves^G, Markus Zahn, and Carlos Rinaldi, “Spin-up flow of ferrofluids: Asymptotic theory and experimental measurements.” Physics of Fluids, 20:053102, 2008. [http://doi.org/10.1063/1.2907221]
• Carlos Rinaldi and Arlex Chaves^G, “Comment on: ‘Tangential Stresses on the Magnetic Fluid Boundary and Rotational Effect,’” Magnetohydrodynamics, 43(1):135-141, 2007.
• Arlex Chaves^G, Fernando Gutman^U, and Carlos Rinaldi, “Torque and Bulk Flow of a Ferrofluid in an Annular Gap Subjected to a Rotating Magnetic Field,” ASME Journal of Fluids Engineering, 129(4):412-422, 2007. [http://doi.org/10.1115/1.2567918]
• Arlex Chaves^G, Carlos Rinaldi, Shehaab Elborai, Xiaowei He, and Markus Zahn, “Bulk flow in ferrofluids in a uniform rotating magnetic field,” Physical Review Letters, 96(19): 194501, 2006. [http://doi.org/10.1103/PhysRevLett.96.194501]
• Carlos Rinaldi, Arlex Chaves^G, Sheehab Elborai, Xiaowei He, and Markus Zahn, “Magnetic fluid rheology and flows,” Current Opinion in Colloid & Interface Science, 10: 141-157, 2005. [http://doi.org/10.1016/j.cocis.2005.07.004]
• Carlos Rinaldi, Fernando Gutman^U, Xiaowei He, Adam D. Rosenthal, Markus Zahn, “Torque measurements on ferrofluid cylinders in rotating magnetic fields,” Journal of Magnetism and Magnetic Materials, 289C: 307-310, 2005. [http://doi.org/10.1016/j.jmmm.2004.11.087]
• Thomas Franklin, Carlos Rinaldi, John M.W. Bush, and Markus Zahn, “Deformation of ferrofluid sheets due to an applied magnetic field transverse to jet flow,” Journal of Visualization, 7(3):175, 2004. [http://doi.org/10.1007/BF03181628]
• Cory Lorenz, Carlos Rinaldi and Markus Zahn, “Hele-Shaw ferrohydrodynamics for simultaneous in-plane rotating and vertical DC magnetic fields,” Journal of Visualization, 7(2): 109, 2004. [http://doi.org/10.1007/BF03181581]
• Carlos Rinaldi and Markus Zahn, “Ferrohydrodynamic instabilities in DC magnetic fields,” Journal of Visualization, 7(1): 8, 2004. [http://doi.org/10.1007/BF03181479]
• Adam D. Rosenthal, Carlos Rinaldi, Thomas Franklin, and Markus Zahn, “Torque measurements in spin-up flow of ferrofluids.” ASME Journal of Fluids Engineering, 126(2): 198-205, 2004. [http://doi.org/10.1115/1.1669030]
• Carlos Rinaldi and Markus Zahn, “Effects of spin viscosity on ferrofluid duct flow profiles in alternating and rotating magnetic fields” Journal of Magnetism and Magnetic Materials, 252: 172-175, 2002. [http://doi.org/10.1016/S0304-8853(02)00704-7]
• Carlos Rinaldi and Markus Zahn, “Effects of spin viscosity on ferrofluid flow profiles in alternating and rotating magnetic fields,” The Physics of Fluids, 14(8): 2847-2870, 2002. [http://doi.org/10.1063/1.1485762]