Ishimura T

Kontani Y

Mori S

Terada T

Terada Tatsumi

Mori Senji

Ishimura Teruo

Kontani Yasuko

寺田 巽

森 仙次

Kanazawa University Repository for Academic Resources

The Scien開 Reportsof the Kanazawa UniverSlty. Vol. V， No. 1， p. 27c-29， October， 19.56 Air Permeability of“Bird Call" used as a Model of“Fabric-Pile" By Tatsumi T.ERA.DA， Senji MORI， Teruo 1S1叩 URAand Yasul王oKONTANI (Received October 21， 1956) 27 In the previous paper(1)， the writers described that the velocity of air-flow through a pile of “Fujiette (plain)" was a Iittle smaller仕mnthat calculated with some assumptioDS， and they also suggested that the decrease was partly attributted to吐leincrease of the distance between two sheets having come to contact each other. To make clear it the the experiments were carried out with a “bird call" in stead of “Fujiette--pile" for the simplicity of its constitution. I1 Fig. 1， Ao a11d A are two metallic circular hollow cylinders of 1.8 cm and 2 cm inside diameter， 7.5 cm and 5 cm in hight respectively， and connected together with another metallic hollow cylinder B， by means of two screws C and D with grease. The cylinder A is fastened to B during the experiments， while the cylinder Ao can be put up and down by its rotation. Two metallic thin plates， about 0.1 cm in thickness， have the circular holes at thier centres， and are respectively soldered i1 parallel across the lower end of Ao and the upper end of A. A stream of air penetrating 出ehole So in出eupper plate impinges centrically UpOl1 the a similar hole S when the plates are held at a distance d. T is a scale attached to the L要~cylinder B， by which the distance d can be read. E To ~ is a tube installed at the distance about 1 cm below 仕letop of cylinder A， and connected to a manometer for the measuremcnt of th.e prcssure difF・er印 ceムPbetween the inside of the cylinder A and the outside of the tubes， a tube F in the bottom of A is connected to an exhaustiol1 arral1gemel1t similar to that used il1 民ianometerF To Exhaust system B D A the previous experiment. Fig 1 ィBirdcal刊 usedin The experimcnts were carried out ul1der the condic the experi即位lts28 T， TERADA， S， MORI， '1.lSHIMuRA AND Y. K'ONTANI tions， the temperature from 250C to 190C and the relative humidity from 72必 to70%， with various sizes of the holes S and So. To begin wi出，仕lerelations of the velocity Q c.c.jmin. versus由epressure differenceムP mmH;.:O were plotted for various distances ι and then taking ムPニニ1 mmH昌ofor each curve， we could obtain the velocity of air-i10w K in c，c，jmin. for the distances d. The curves In Fig個 2have been obtained by thus manner and they were the typical relations between K a吋 dfor S=80ニ 0.78mmふetc・.Even if the experimental co凶 itions，such as the temperature and the humidity in those cases and the thickness of parallel plates soldered at the ends of the cylinders， differed a little， the curves gained would be the type simitar to those. From these， itis clear that the value of K decreases with increasing distance d， rapidly at first and slowly later on， Now， itseems to us that the fact， the observed values of K for “Fujiette-pile" is smaller than those calculated theoreti-cally under the condition of nondeformation of the inner sheet， ispartiy due to the increase of the dIstance between two adjoining sheets. Lastly， vv"e must enquire to what cause仕Jedecrease of出evelocity of air with increasing distance d is due. To attack this problem we must look back upon Rayleigh's(2) suggestion as to the action of “bird call，" that is， "玖Thena symmetrical excrescence reaches the second plate， itis unable to pass the holeもiVithfreedom， and投ledisturbance is thrown back， probably with the velocity of sound， tothe first plate， where it giγes rise to a further disturbance， it?;Jiyt 250 20 ¥…+ 惨旬、ー電-崎竜"'-司、~・守-.150 i∞ ~事由Fー-噂¥;0=肘ニ0.781nm争50トL国持品明喜一L吋Eム叩占ーらー~to grow in its turn during the progress of the Õ~-õ.5~-To'---":i'5~257，."，. jet. But the elucidation of this and many Fig. 2. K-d curvcs obtaned with kindred phenomena remains stil to be effected.ηvarions hol田If Rayleigh's suggestion is in the right for our ca切ら wecan fairly wel1 explaine the experimental rεsults of “Fusiette pile" as follows. “Fujiette" consists of artificial silks and staple fibers， Ccnsequently the inner sheets of a pile may be deformed inwards one after the other owing to a sudden suction at the beginning of a run and the distance between adjoining sheet increases. 1n the case， ifthe excrescence passing through outside sheet reaches the second which is covered with the nap， the disturbance reflected at there will be thrown back to the former and obstruct the ilow of air through it. As a resul AiかrPerm仰匁ze印αbilμit砂:yQザfα凶Sα Modelof'“'F，αb伽ri化c-Piμle円 29 References (1) T. Terada and Y. Kontani，“Flow of Air through a Pile of Textile Fablic"泊 thesame volume as this paper. (2) Lord Rayleigh， Theory of Sound， Vol. II (1896) pp. 412 . . 

Air Permeability of Bird Call used as a Model of Fabric-Pile

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Air Permeability of Bird Call used as a Model of Fabric-Pile

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