单词 | downwash |
释义 | downwashn. 1. Soil, debris, sediment, etc., carried downward or downstream by water; the transport of material in this manner. ΚΠ 1875 J. W. Judd Geol. Rutland (Mem. Geol. Surv.) viii. 218 The unkindly nature of the soil is usually somewhat tempered by the downwash from the overlying strata. 1888 W. A. E. Ussher et al. Geol. Country around Lincoln (Mem. Geol. Surv.) xi. 106 The junction with the Ironstone is almost everywhere concealed by downwash from the friable Carstone. 1912 H. B. Woodward Geol. Soils & Substrata xviii. 221 All slopes are liable to receive a certain amount of downwash or rainwash in the form of earthy débris or angular detritus. 1943 G. Erdtman Introd. to Pollen Anal. xv. 199 Pollen grains of different age may sometimes be found side by side not only as a consequence of downwash or resedimentation, but also as a consequence of the activities of animals, such as earthworms. 2012 Jrnl. Arizona–Nevada Acad. Sci. 30 39/2 In mill sites containing processed tailings it is evident that stormwater has transported sediment downwash from the Eagle Milling Site. 2. Aeronautics. The downward deflection of an airstream by an aircraft wing, rotor blade, etc.; (more widely) the downward deflection of an airflow by an object. Also: air deflected downwards in this way. ΘΚΠ the world > matter > gas > air > moving air > [noun] > a movement of air > a current of air > downward current > deflected by aerofoil, etc. slipstream1913 downwash1914 1914 Rep. & Memoranda No. 128 in Aeronaut.: Techn. Rep. Advisory Comm. Aeronaut. 1913–4 (1915) 356 To investigate the form of the flight-path will use the following symbols..a' = Acutal angle of incidence of tail, taking into account setting, downwash, &c. 1931 Flight 20 Nov. 1148/1 The amazing control of the Autogiros, old as well as new, is very largely due to the downwash from the rotor blades. 1966 D. Stinton Anat. Aeroplane v. 58 To generate a given lift at a given airspeed an aerofoil of long span has to impart a smaller downwash to the air it meets than an aerofoil of shorter span. 1970 D. Dwiggins On Silent Wings vii. 111 The stratospheric lenticular foehnwall hung steady and unmoving, its downwash resembling water overflowing a dam. 2010 Daily Tel. 8 June 27/1 Within minutes several aircraft were..hovering low to use the downwash from their blades to push life rafts away from the burning wreck. Compounds downwash angle n. Aeronautics the angle through which an airstream is deflected downwards by an aircraft wing, rotor blade, etc. ΚΠ 1919 Gloss. Aeronaut. Terms (Royal Aeronaut. Soc.) 21 Downwash angle, the angle through which the airstream relative to the aeroplane is deflected by an aerofoil or other body. Measured in a plane parallel to the plane of symmetry. 1963 Flying Mag. Sept. 96/3 The larger the downwash angle, the greater the deflection of the average relative wind. 2017 S. Corda Introd. Aerospace Engin. vi. 807 The downwash angle, ε, is usually an experimentally derived quantity, often from the results of wind tunnel testing. This entry has been updated (OED Third Edition, December 2018; most recently modified version published online March 2022). downwashv. Aeronautics. rare. transitive (in passive). Of an airstream: to be deflected downwards by an aircraft wing, rotor blade, etc. Cf. downwash n. 2. ΚΠ 1922 Encycl. Brit. XXX. 19/2 The reaction upon the rear plane is therefore inclined backward by the angle through which the air has been ‘downwashed’ by the leading plane. 2007 C. B. Pedersen & R. Żbikowski in R. Liebe Flow Phenomena Nature II. vi. 631 The wake trailed behind the rotor of a hovering helicopter is convected downwards (‘downwashed’). This entry has been updated (OED Third Edition, December 2018; most recently modified version published online March 2022). < n.1875v.1922 |
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