Waka, Ryoji

Yoshino, Fumio

Tottori University Research Result Repository

Pressure Distribution on the Surface near theCylinder一Body JunCturebyFunlio YosEINO*and RyoェWAKA*(Received M ay 31,198のThis investigation is concerned with the static‐PreSSure dis ribu ions on twosurfaces, i.e,, those of a side‐wall and a circular cylinder with blowing. Itwas found that the results of this investigation were quite consistent with theflow pattern established by a series of investigations conducted in our labO_ratory.l lntroductio■It has been 、vell known that the cOmplex flow pattern near the high‐■fting―surface‐body juncture becomes further complex because of the secondary flo、vo Andit is extremely difficult to analyse that flo、7 qu titatively. Then an attempt wasmade to visualize the flow around a circular cylinder with blowing by means ofseveral techniques,that is, the dye‐injection method,the tuft lnethod and the oil,flowmethod. In a series of these investigationsl).り'3)and Others,4),5),6) the fio、v patternnear the tuncture has been mostly established.In this report we describe the pressure distributions on the side‐wall and he cy―linder with and without blo、ving in order to further confirnl those results of investi一gations.2  NomenclaturesC′σ =  Sectional lift coefficient at the■lid‐span,C, =  Static‐pressure coefficient ,Cμ = ヽIomentum coefficient of the jet iD = Diameter of the cyhnder,亀 =Rey401dS number based on D and U∞;U∞ = Main flow speed;* Department of MechanicaI EngineeringRcPortS Of the Faculty of Engineering,Tottori University,Vol. 11           15x,y and z =  Distances froni the ■lid―span in streanュwise, spanwise and upwarddirections, respettively,yω = Distance froni the side‐wall in pan、vise direction,θ′ =  Angular position of the blowing slot,3  Experi】mental ins絢しllument and methOdThe apparatus fOr this experilnent、vas the same One described in the references2)and 4), and is not repeated here in detail.The cross section of the circular cylinder and the assembly drawing of the modelare shown in Figs. l and 2, respectively. The model cOnsists of t、vo partitio■―plat scalled the side―wall from mow on and a cylinder、vith a blowing slot,0.59 1nn■、vidth,along he whole spaniThe arrangements of 166 static‐pressureholes on the starboard side‐、vall and 335static―pressure holes on the cylinder aresho、vn in Fig.3 and Tablel,respectively.The experilnent 、vas made by properlyvarylng ,r  nd θブat the fixed values ofthe aspect ratio of eigh and the ReyIIcjldsnumbers of l.5x105 and 2,l x 10。 . Theranges of tt and θ′vere from O to O.37and from 50° to 120°, respectively.F10w directiOnFig。l ctOss seCtiOn of the cylinder.⇒!呼“tiOn_pにteFig,3 Arrangement of the static‐pressureholes on the side―wall.Uф導.        150n‐‐????????????‐‐?‐‐Fig。2 Asseコnbly drawing of the model.Fumio YOSHINO and Ryoji WAKA I Pressure Distribution on the Surface nearthe Cylinder―Bo y JunctureTable I  Arrangement of the static_pressureholes on the cylnder.*There is the first silltic―pressure hotelli O=9,46.614The pressure on the side‐walland 5,respectively. The circlesthey take the values assigned toResults and Discussionwhen Cμ= O and Cμ= 0.25 are shown in Figs, 4in these figures indicate the positions at whichin the figures. Those positions were obtained byRe=生5x1050,=90°Cμ Q25Cp=-05X/DXrDPressure distributiOn on the side―wa11when Cμ=0.25,?????Re=|.5X1050j=90°Cμ=0 ????ぅ?cp -05H34総ョIB予瞥ギ:ユhi°n on the dde―wallRowyw(mm)Anqutαr pOsitionTotQt牡♂キ| 鳥ゞ態Il'1:m24th and of 15°fromthe 24th io the 31stヽ1553 20.340.373091.010.341!|十1き,帯∫吝II°iキ:m28th clnd of 15°fromthe 29th to the 31st.1245 55_3111.0164040a0ヽt intervats of 6°fr m thefirst holきtO the 56thFig,5Reports Of the Faculty OE Engineering, Tottori University,Vol. 11           17proportional distribution among measured values at the nearby positions illustratedin Fig.3.The solid lines are those obtained by smoothly connecting the symbols.The values on the cylinder surface are replaced by those at the distance of 3 ■1lnfroni the juncture.When Cμ= 0, the pressure distribution seems to be sy■llnetrical with respect tox‐axis,The lowest pressure region exists rigtt behind the cylnder,ユ.e., at x/D≒ 0.8 and the pressure gradually increases downstreamo This pressure distributionis qualttatively equal to that at the■lid―span。3)It is naturally thought that this pres―sure distribution induces the secondary flow on the side―wall.  The adverse pressuregradient downstreanl the cylinder on x‐axis may cause the reverse flow toward thecylinder, 、vhich results in the formation of a pair of vortices.1)'2)Vヽhen CP> 0,the pressure distribution is 40 10nger syn■■etrical with respect tox‐axis. In general, the pressure on the upper‐half of the side‐wall becomes lowerand that on the lower‐half b comes higher than those of the corresponding sides inthe case of吻=0,respectively.Thねpressure distribution also resembles that inthe mid‐span3). The lowest pressure region moves from the rear part toward theshoulder of the cylinder and the pressure drop there, 、vhich seems to be caused alsoby suction effect of the blowing jet, is in particular remarkable. Therefore it isthought that the change of the pressure distribution on the side‐wall changes thepattern of the secondary flo、v.The lo、ver pressure on the upper―half of the side―、vall than on the lo、ver―half willinduce the upward secondary fk)、v, namel the upwash near the tuttture, 、vhichwill cawse a pair of vortices to move up、ard. The stronger pressure drop near theshoulder may induce the stronger upper vortex of a pair of vortices in the placenearer to the cylindeF Vヽhile th  allmost invisible adverse pressure gradient will re―duce the strength of the lower vortex of the■l in the place arther downstream.These are correspondingヽvith the behavior of a pair of vortices formed behind thecylinder on the side―、vallり,2). Namely the upper one of a pair of vortices movescounterclockwise with increasing ttS strength and the lo、ver one moves clock、vise、vith decreasing its strength as C″ inc ases. After all the k)、ver vortex disappearsand the upper one only remains when C″ is extremely strong as already mentionedin detaill)'3).Figs. 6 and 7 show the pressure distributions on the side―wall、vhen the values Ofθブ and Cμare properly adiusted under constant R♂so as to obtain nearly the samelift coefficients with each other at the mid―span.It is seen froIIn these figures thatit is not the mere inference that if the lift coefficients at the mid‐span are qualto each other, the pressure must be distributed much the same way on the side‐wallindependently of θブ and Cμ. This result is very interesting and seems to be con―■ected with the silnilarity of the flow6)near the juncture in his case.Fumio YOSHINO and Ryoti ?VAKA I PresSure Distribution on the Surfacethe Cylinder―Bo y Juncture〔ど:路105o,=90°Cμ=0,3Fig.6 Pressure distribution on the side―wallwhen clc =6.24.The pressure distribution on the cylindernear the starboard side‐wall ls shown inFig.8,The upper and lower separationlines move upstreani and do、7nStre i asthe side―、vall is approached, respectively.It is thOught that his movement of theseparation lines near the side‐wall has adO圧?nant effect on three dimensionality ofthe wake.The lo、vest pressure point in the separatedregion lies on the upper side near the side‐wall,that is,y″/D≒0,6 and θ≒ 170°.This point seems to be at the position ofthe center of the vortex shed directly fromthe cylinder surface since that position iscorresponding to the central position(cOre)of the trailing vortex visualized with thedye―iniectiOn lnethod and the tuft rnethodl)'3).The secondary flo、v toward the lo、vest pres―sure point in the separated region oughtto be induced counterclockwise due to theX/DFig.7 Pressure distribution on the side―wallwhen CIc =6.35.Re=2.Ix105 8j=90°  Cμ=0.3yw/D   1       0S ot(90°)-3.0~I.U´SepGrationti300°C=〕Hg.8rと互二SI:録ぎ農塁電P&屋翠露ュデylinder〔[::♀二105町=120°Cμ=0。2??「????ぅ??．?―?||Reports of the Faculty of Engineering,Tottori University,VoI, 11           19downwash on the left side of that point and the up、vash on the right side, andentrained into the core of the vortex (the 10ヽVest pressure region)mentiOned above.The secOndary flo、v near the cylinder‐side‐wall jultlcture becomes stronger withincrease of CP, since this three dilnensionality of the pressure distribution near thejullcture is strengthened with increase of Cμ.5  Co■cluding remarksThe pressure distributions on the surfaces of the cylinder and the side wall weremeasured to confirェl the flow pattern already visualized by means of several tech―niques, Consequently it is found that tLe results obtained in this investigation areconsistent with the visualiZed flo、v pattern and vortex system near the juncture,andthe results of the other investigatiottsl)～6).Referencesl)Yoshino,マVaka and Hayashi,6th Symposium on FIow Visualization,(1978-7),43,2)Yoshino and others,Preprint of Bulletin of JSヽこE, N .775-2(1977-10),136.3)Yoshino and Waka, RepOrts oだ the Facuhy of Engineering, Tottori University,6-1 (1976-3),1.4)Furuya,Yoshino and Waka,Preprint of Bulletin of JSヽlE a d JSPE,(1974-11),7.5)Yoshino and others,Preprint ott Bulletin of JSME,No.775-2(1977-10),133.6)Yoshino and others,Preprint of Bulletin of」SME,N .808-2(1980-5),140.

Pressure Distribution on the Surface near the Cylinder-Body Juncture

http://repository.lib.tottori-u.ac.jp/files/public/0/1914/20180622143441549162/rfetu11(1)_14(1).pdf

Pressure Distribution on the Surface near the Cylinder-Body Juncture

Abstract

Similar works

Full text

Available Versions

Tottori University Research Result Repository