| 释义 |
▪ I. streamline, n.
Also stream-line.
1. Hydrodynamics and Aerodynamics.
a. (See quot. 1906.) In mod. use, a line such that, at any instant, the direction of the tangent at any point is the direction of the flow of fluid at that point. (This definition is equivalent to that in quot. 1906 for the special case of steady flow.)
1868W. J. Rankine in Engineer 16 Oct. 285/1 A stream-line is the line, whether straight or curved, that is traced by a particle in a current of fluid. 1873J. C. Maxwell Electr. & Magn. §648 II. 260 If ϕ is constant for any curve, there is no current across it. Such a curve is called a Current-line or a Stream-line. 1882Minchin Unipl. Kinematics 151 When the motion becomes steady, each line of flow becomes the actual path of a fluid particle, which is called a stream-line. 1906H. Lamb Hydrodynamics (ed. 3) 17 A ‘line of motion’ or ‘stream-line’ is defined to be a line drawn from point to point, so that its direction is everywhere that of the motion of the fluid. Footnote, Some writers prefer to restrict the use of the term ‘stream-line’ to the case of steady motion. 1945R. von Mises Theory of Flight ii. 23 In the case of an unsteady flow the streamlines, i.e., the curves whose tangents have the velocity direction are, in general, not the pathways of the particles. 1971G. M. Hidy Waves iv. 47 Streamlines generally bear no relation to particle paths because different fluid elements form different streamlines at given times. 1980Bober & Kenyon Fluid Mech. iv. 124 If the flow is steady then a fluid particle will move along a streamline.
b. attrib. (a) Designating motion of a fluid that is free from turbulence, so that it can be represented by a pattern of streamlines that either is constant or changes steadily with time.
1898Hele-Shaw in Rep. Brit. Assoc. 136 Stream-line Motion of a Viscous Film. 1916H. Barber Aeroplane Speaks 62 To secure a stream-line motion of the air free from eddies. 1957G. E. Hutchinson Treat. Limnol. I. v. 251 The only simple way of observing regular streamline or laminar flow is adjacent to some smooth surface over which a slow current is passing. 1979A. L. Lydersen Fluid Flow & Heat Transfer i. 2 This type of motion, where the velocity at a certain point is constant and independent of time, is termed laminar flow. It is sometimes called streamline flow or viscous flow.
(b) Having or being a shape such that the flow of a fluid round it is smooth, and there is no separation of streamlines from the surface; more widely, shaped so as to reduce air or water resistance; streamline wire, a wire of elongated cross-section.
1907F. W. Lanchester Aerodynamics i. 20 In an actual fluid, bodies of other than streamline form experience resistance apart from that directly due to viscosity. Ibid. iii. 102 In the hydrodynamic theory of an inviscid fluid, every conceivable body is of stream-line form. 1909C. C. Turner Aerial Navig. To-day viii. (1910) 131 Bodies having ‘streamline’ form present the least resistance to the air. Pure streamline form is, roughly speaking, pear-shaped, the blunt end foremost. 1914Automobile Topics 30 May (Advt., back cover), That beautiful stream-line Car. 1918W. L. Cowley Aeronautics iv. 93 The following table gives the resistance coefficients of aeroplane stream line wires, of fineness ratio 3:1. 1919G. Whale Brit. Airships 160 The remaining two engines are carried in a small streamline car situated amidships. 1928E. Cadbury in C. F. S. Gamble Story North Sea Air Station xxii. 408, I..seized a scarf, goggles and helmet, tore off my streamline coat, and semi-clothed..took a running jump into the pilot's seat. 1929Jrnl. R. Aeronaut. Soc. XXXIII. 360 In aeronautical nomenclature a ‘streamline body’ is one about which the flow of a real fluid..approximates very closely to a steady flow of the hypothetical inviscid fluid, except in a very thin layer called the ‘boundary layer’, surrounding the exposed surfaces. Ibid. 361 The ideally streamline aeroplane cannot exist. 1936J. C. Corlett Rigging & Airframes v. 108 On the final inspection of streamline wires they must be checked for ‘safety’. 1953M. Rauscher Introd. Aeronaut. Dynamics vi. 259 The theory of the ideal fluid comes very close to representing the actual flow conditions about a streamline body in a fluid of low viscosity.
(c) fig.
1933S. Spender Poems 44 Where only a low streamline brightness Of phosphorus on the tossing hills is white. 1942R.A.F. Jrnl. 2 May 21 The camp is the last word in streamline modernity. 1967B. J. Banfill Pioneer Nurse xi. 129 Snow, in long streamline drifts, covered the now familiar objects.
c. Used predicatively as adj. in preceding senses.
1907F. W. Lanchester Aerodynamics i. 27 If..we assume continuity as hypothesis, then all bodies must be streamline. 1922Daily Mail 3 Nov. 2 The body of the car is streamline according to British practice. 1929Jrnl. R. Aeronaut. Soc. XXXIII. 366 The b.h.p. required..should not be seriously influenced by interference, provided that the interference does not cause the flow to cease being streamline. 1936B. Jones Elem. Pract. Aerodynamics vii. 115 Wherever possible the airplane parts that would cause parasite drag are made streamline in shape. 1971J. W. Ireland Mech. of Fluids viii. 234 Oil of specific gravity 0·9 and viscosity 1 poise is pumped through a 5 cm diameter pipe at the rate of 280 litres/min. Show that the flow is streamline.
d. A contour of a body that is coincident with a streamline of flow round it; loosely, a smooth, flowing outline.
1917D. W. Thompson Growth & Form xvi. 673 The naval architect learns a great part of his lesson from the investigation of the stream-lines of a fish; and the mathematical study of the stream-lines of a bird..has helped to lay the very foundations of the modern science of aeronautics. 1936B. Jones Elem. Pract. Aerodynamics vii. 117 Any non-streamlined body can have its resistance or drag greatly reduced merely by the addition of a blunt nose and a tapered tail. If the contour is also a continuous curve the shape approaches the ideal streamline. 1943Koestler Arrival & Departure ii. 41 He was able to re-draw in his mind the curve of Odette's knees.., the streamlines of her jumper. 1944W. Fortescue Mountain Madness xxiv. 162 If my curls were grey, at least I had kept my stream-line.
2. (See quot.)
1885Tait Prop. Matter iv. §83. 70 The line of steepest slope at any point of a surface is represented on the map by the shortest line which can be drawn to the nearest contour line. Thus it cuts the contour lines at right angles, and is the path along which a drop of water would trickle down. It is therefore called a Stream-line.
▪ II. ˈstreamline, v.
Also stream-line.
[f. the n.]
1. trans. To give a streamline form to. Chiefly as streamlined ppl. a., streamlining vbl. n.
1918H. Barber Aeroplane Speaks (ed. 6) 61 From the designer's point of view it always pays to stream-line detrimental surface. 1927Haldane & Huxley Anim. Biol. xiii. 316 The air-sacs..are used to stream-line the body. 1927Daily Tel. 27 Sept. 9/5 It appears that Flight-Lieut. Kinkead came down because the spinner, a metal fitting streamlining the propeller boss, came off.
2. fig.
a. To slim; to remodel on smooth, uncluttered lines. Also absol.
1935P. B. Hawk (title) Streamline for health. 1937Denver Post 27 Jan. (Mag. Section) 9 (heading) Streamline your dance frock.
b. To simplify, esp. in order to make more efficient or better organized.
1936Sun (Baltimore) 2 Nov. 13/5 Those who watch financial fashion observe a tendency to streamline capital set-ups for tax purposes. 1947Hansard Commons Written Answers 2 Dec. 46, I am anxious to do all I can to streamline controls. 1950A. Huxley Let. 16 Mar. (1969) 620 Chapters might be ‘streamlined’. 1957New Yorker 26 Oct. 60/2 The producers got panicky and decided to ‘streamline’ the production, stressing professional finish. 1958Post Office Mag. Apr. 117/2 The Ministry are co-operating with us all..on streamlining general building methods. 1974Whitaker's Almanack 1975 812/1 Through its advisory services, it helps its member governments to..streamline health services. |