Motion of fluids with very little viscosity By L. Prandtl (794397), страница 2

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1-4 show the flow pastThe separating or boundarylayer, which passes off from the edge, is apparent.In No. 1 itis very small;, in No. 2, concealed by strong disturbances; in No,,.3, the vortex spreads over the whole picture; in No. 4, the pepmanentcondition is shown.the wall.A disturbance is also evident aboveSince a higher pressure prevails in the corner, due——1:–——- .—9N.

A. C.A.,Technical LlemoraildumNo. 452to theoobstruction of the water flow, even here the flow sepa–ra”tes frem””’thewall after awhile ,(Cf. Figs. 1-.4). The variousstriae visible in the vortex-free portion of the flow (especiallyin Nos. 1-2) are~Luetothefact that, at the inception of theflow, the liquid was not entirely quiet.Nos. >6show the flowaround a curved obsta”cle or, from another viewpoint, throug’nacontinuously narrowing and then widening channel.. No. 5 was takenshortly after the inception of the flow.developedOne boundary layer hasinto a spiral, while the other ‘has elongated and broken[.1up into very regular vortices.I7 shows the beginning of the separation;On the convex side, near theright end, t’nebegiiming of the separation can be seen.No.

6shows the permanent condition in which the flow begins to separate about at the riarrowest cross section.,/fiTos.7–10 show the flow around a cylind-rical obstacle.No.Nos. 8-9, subsequentstages.Between ”the two vortices there is a line of water whichbelongedto the transition layer before the beginning of the sep-aratio-n. No. 10 shows the permanent condition.The wake of tur–bulent water behind the cylinder swings back and forth, whencethe momentary unsymmetrical appearance.The cylinder has a ‘slotalong one of its generatri.ces. If this is,placed as shown inNos.

.11-12 a,nd water is drawn out through a tube, the transitionlayer on one si:.ecan be intercepted.When this is missing, itseffect, the separation, is eliminated. In No. 11, which correqxzck,,in point of time, to No. 9, there is seen only one vortex and the.-N.A.C.A. Technicnl,,—’——u——.————/“”rFig.1.\u.,.Figoaf,i.,.._.-..Fi.:s.3\--—.

------------- -- ..,. . ..-----------------------i.Fig.4----------------& 4Fig’s.5& 6N.A.C.A. Technical l!ernoran~.uznN0,452m.--———----Fi:<.5Fig.6..—N.A.C.A. Technical Memorandum No.452..Fig.7Fig.8.N.A. C.A. Technicnl]leiT!O?7~ll~.Lliii.No. ~152Fig.9Fig.10N.A,c .L. Technical lki~or~nd.uzuNo.452I23456,!1“1.

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