viscosity
(vɪˈskɒsɪtɪ)
Also 5–6 viscosite, 6 -tye, 6–7 -tie.
[a. OF. viscosite (F. viscosité) or ad. med.L. viscōsitās, f. L. viscōs-us viscous: see -ity. So It. viscosità, Sp. viscosidad, Pg. -idade.]
1. a. The quality or fact of being viscous; viscidity.
| a 1425 tr. Arderne's Treat. Fistula, etc. 65 Bole with his drynes and viscosite consumiþ þe moistenes. c 1530 Judic. Urines iii. vi. 50 b, Suche maner of froth sheweth alway more viscosite..of humours in y⊇ body, than doyth ony other maner of froth. 1582 J. Hester Secr. Phiorav. iii. iv. 9 It taketh awaie the viscositie in the Stomacke, and openeth the powres. 1620 Venner Via Recta iv. 80 The Perch is..a little inferiour.., by reason of some viscosity in it. 1669 Boyle Contn. New Exp. ii. (1682) 140 That liquor is very thin, and hath no viscosity to resist the pervading body. 1686 Goad Celest. Bodies i. ix. 31 Rarity is nothing but a Privation of Density,..Friability of Viscosity. 1733 Cheyne Eng. Malady iii. iv. (1734) 304 The phlegm in the Glands..is nothing but the Viscosity of the Serum of the Blood. 1771 T. Percival Ess. (1777) I. 190 To dissolve a general lentor and viscosity of the whole mass of fluids. 1821 W. P. C. Barton Flora N. Amer. I. 65 The extreme viscosity of its pubescence, has caused it to receive the specific name it bears. 1899 Allbutt's Syst. Med. VII. 245 The resistances due to the viscosity of the blood in the arteries. |
| fig. 1662 M. W. Marriage-Broaker v. i, So I, by my viscosity, Labouring for life in love-lime [am] drown'd in Cupid's galli-pot. 1902 Spectator 29 Nov. 825/1 Vehicular traffic..will..block itself from its inherent viscosity. |
| attrib. 1898 Allbutt's Syst. Med. V. 461 The determination of the viscosity coefficient of the blood. |
b. magnetic viscosity, tendency on the part of a magnetic medium to retard the magnetizing force.
| 1892 Electrical Engineer 16 Sept. 287/1 Up to the frequency tried—i.e., about 125 per second—there is no sign of magnetic viscosity; the magnetic cycle is unaffected [etc.]. |
c. In scientific use, the tendency of a liquid or gas to resist by internal friction the relative motion of its molecules and hence any change of shape; the magnitude of this, as measured by the force per unit area resisting a flow in which parallel layers unit distance apart have unit speed relative to one another; also called
absolute viscosity or
dynamic viscosity;
kinematic viscosity, the dynamic viscosity divided by the density of the fluid.
| 1866 J. C. Maxwell in Phil. Trans. R. Soc. CLVI. 249 The viscosity of a body is the resistance which it offers to a continuous change of form, depending on the rate at which that change is effected. Ibid. 254 Suppose that this friction is equal to a tangential force f on every square foot, then f = µυ/a, where µ is the coefficient of viscosity, υ the velocity of the upper plane, and a the distance between them. 1880 Proc. London Math. Soc. XI. 58 If ν be the kinematic viscosity. 1913, etc. [see poise n.2]. 1921 A. W. Judge Automobile & Aircraft Engines viii. 309 The kinematical viscosity of air is thirteen times that of water. 1927 Schoder & Dawson Hydraulics xvi. 275 The unit of absolute viscosity is called a poise. 1943 R. C. Binder Fluid Mech. v. 50 Viscosity = shearing stress/rate of shearing strain. Sometimes the foregoing term is called absolute viscosity. Probably a better term would be dynamic viscosity. 1962 J. M. McKelvey Polymer Processing ii. 41 In general, liquid viscosities decrease and gas viscosities increase with increasing temperature. 1964 [see stokes n.4]. 1979 C. A. Marchaj Aero-Hydrodynamics of Sailing ii. 169 The kinematic viscosity of water..needed for Reynolds Number computation at the ‘normal’ temperature of 15°C is..1·23 × 10-5 ft2/sec. |
2. A viscous substance; a collection of viscous matter.
Cf. viscidity 2.
| 1545 T. Raynalde Byrth Mankynde 56 Linesede oyle, or oyle of fenegreke, or the viscosite of holioke, and suche other. 1597 A. M. tr. Guillemeau's Fr. Chirurg. 27 b/2 When the stomacke is burthened with anye cruditye of vndigested meat or drincke, or with anye other viscositye whatsoever. 1646 Sir T. Browne Pseud. Ep. 80 As is observable in drops of syrup, oyle and seminall viscosities. 1651 French Distill. v. 143 It openeth obstructions, and purgeth viscosities of the stomack and bowells. 1707 Floyer Physic. Pulse-Watch 297 These Viscosities depend on Heat. 1794 R. J. Sulivan View Nat. I. 493 The sand..has, by the means of a calcareous viscosity infiltrated by the sea, become so hard, as to become stone. |
3. Special
Comb.:
viscosity index, a number expressing the degree to which the viscosity of an oil is unaffected by temperature.
| 1929 Dean & Davis in Chem. & Metallurgical Engin. XXXVI. 618/1 This system of classification permits expressing the viscosity-temperature coefficient of an oil as a simple function of its Saybolt Universal viscosities at 100 and 210 deg. F. This function, hereafter referred to as the ‘viscosity index’, is independent of the actual viscosity of the oil. 1977 Lubricants Business (Shell Internat. Petroleum Co.) 3 These [additives] are chemical compounds which supplement the properties of the mineral base oil; for example, to reduce wear of moving parts..and to improve viscosity index. |