Methods and systems for characterizing multiple parameters of viscous fluid simultaneously are provided. By imposing an oscillatory deformation profile on a filament formed of the viscous fluid between two plates, a nonlinear fit to the deformation profile captured at different times is analyzed against a filament model dependent upon the plates radius, viscous fluid density, and the oscillation frequency of the imposed deformation profile. The Reynolds number, Weber number, and the aspect ratio of the viscous fluid are thus determined, for identifying the Newtonian fluid.

A system is provided that can include a first tube for communicating a fluid through a wellbore. The system can also include a gap between the first tube and a first electromagnetic acoustic transducer (EMAT). The first EMAT can be positioned to magnetically couple with the first tube. The first EMAT can include a magnet and a wire coil positioned around the magnet. The first EMAT can coupled to a power source and positioned to, responsive to receiving a power from the power source, apply a first magnetic force to the first tube for determining a density or viscosity of the fluid.