Nano- and Microtechnology from A - Z: From Nanosystems to Colloids and Interfaces

F

Fallout

A process in atmospheric aerosols in which particles or droplets that are larger than about 40 μm in diameter (in the “precipitable” range), fairly quickly settle out and are removed from the atmosphere.

Falling Ball Viscometer

An instrument used for the measurement of viscosity in which the time for a solid sphere to drop, through a fluid, between reference points in an angled cylindrical measuring tube is measured. The tube is usually placed at an angle of 10° to the vertical direction. This method is most suited to the determination of Newtonian viscosities. There are various designs, among which is the Höppler type. The rising bubble viscometer operates on the same principle except that the bubble rises rather than falling (example: the Gardner Timer Tube and determining Gardner seconds). A variation that can be used for non-Newtonian fluids is the falling needle, or piston viscometer. In this case, a needle or piston falls within the cylinder, so the shear rate is known (example: Norcross and Mobilometer viscometers). See also Orifice Viscometer and Table 13.

Falling Needle Viscometer

See Falling Ball Viscometer and Table 13.

Fann Viscometer

A commercial instrument brand-name that has become a general use term; better known than the Saybolt type. The basic model is a direct torque-reading, mechanically simple viscometer of the concentric-cylinder type, which is used under laboratory and field conditions for determining the viscosities of materials over ...