Transient Numerical of Piston Wind in Subway Station. Haitao Bao

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1 Appled Mechancs and Maerals Submed: ISSN: , Vols , pp Acceped: do: / Onlne: Trans Tech Publcaons, Swzerland Transen Numercal of Pson Wnd n Subway Saon Haao Bao Faculy of Transporaon Engneerng, Huayn Insue of Technology, Huaan, Chna bh @163.com Keywords: Tran; Pson wnd; Dynamc Grd; Transen Characerscs Absrac. Compuaonal Flud Dynamcs (CFD) s used for he nvesgaon of he pson wnd. The Naver-Sokes (N-S) equaons and sandard K urbulence model were appled o se up he model. The ran ransen aerodynamc characersc has been research durng he crossng process. The smulaon resuls are rusworhy and numercal smulaon of pson wnd s feasble usng dynamc grd n CFD sofware, whch provdes he bass for he vrual desgn of pson wnd. I s sgnfcan mporance for furher sudyng he srucure of ran, shoren s developmen and gudng sgnfcance for praccal applcaon. Inroducon The characerscs of flow felds n annuluses beween movng and sac walls formed n ran runnng hrough a unnel s he mporan conen of unnel aerodynamcs and also one of he man bases o sudy and solve he problem of he pson wnd n unnels [1]. Aerodynamc problems occur parcularly when a ran moves no a unnel. Wnd ncreases and he pson wnd are formed n fron. Ths compresson wave propagaes oward he ex a he speed hgher han he ran self. The flow feld where a ran moves no a unnel and goes hrough should be nvesgaed for he fuure effecve unnel and ran confguraons. The frs sudy abou hs flow feld s conduced by Tollmen n 1927 [2]. The flow feld around a ran runnng nsde a unnel s analycally suded and he effec of he ran speed on he pressure ncrease n fron of he ran s nvesgaed. The movng boundary confguraon and s unseadness were suded by Takanobu Ogawa and Kozo Fuj n The flow feld s dvded no zones and each zone s solved separaely wh nformaon ransferred usng he Forfed Soluon Algorhm (FSA) a each me sep. Ths mehod can be appled o movng boundary confguraon sraghforward by movng each zone a s own speed. Pson wnd s no only flucuaes n he horzonal drecon, bu also accompanes wh he volaly n he vercal drecon. The wnd flow feld s srucure s very complex, wh unseady flow properes. The use of unseady flow heory s no only a more accurae smulaon of he unseady flow of he pson wnd nsde he unnel, bu also o consder he use of he unnel arflow nera for he unnel venlaon o save energy. On he calculaon mehod of pson wnd, a one-dmensonal subway envronmen smulaon sofware SES (Subway Envronmen Smulaon) sofware, whch was developed by he U.S. Deparmen of Transporaon s used mos recenly. Such as, Chcago, Boson, Hong Kong, Guang Zhou and so on, dozens of subway venlaon desgns have adoped he SES smulaon sofware. In addon, some oher commercal CFD sofware, for nsance, Km and oher auhors carry ou an analyss of he pson wnd caused by subway ran s acceleraon and deceleraon movemen n a unnel by usng CFX4. Ke, and so on, used PHOENICS o analyze he effec on Mero Plaform Screen Doors caused by he pson ar pressure [3]. The Generaon Mechansm of he Pson Wnd When he ran s runnng n he open space, he ar n fron of he ran wll be pushed no he sdes and op of he ran easly, and hen flows around he back of he ran. When ran move no he range of he unnel, for he unnel wall lmng he flow of ar, he ar pressure n fron of he ran ncreases as a resul of squeeze.one par of compressed ar moves forward along he unnel n he All rghs reserved. No par of conens of hs paper may be reproduced or ransmed n any form or by any means whou he wren permsson of Trans Tech Publcaons, (ID: , Pennsylvana Sae Unversy, Unversy Park, USA-18/02/16,17:47:25)

2 468 Machne Tool Technology, Mecharoncs and Informaon Engneerng form of waves, and he oher flows oward he rear of he ran hrough he annular space beween he ran and unnel[3]. A he meanng me, he ar pressure ges hgher n he fron of he ran, and he ar sucon a he rear of he ran wll also reach he maxmum. A hs pon, he ar whch flls he space creaed by he movemen of he rear of he ran parly comes from he annular space. The oher comes from he saon where he subway ran leaves. Such phenomenon s known as he ran pson effec and he formaon of ar s known as he pson wnd. The generaon of pson wnd s closely relaed wh he unnel s srucure and he operaon of rans, parcularly he blockage rao. The volume of he pson ar s affeced by many facors, such as he ran s blockage rao n a unnel, he ran s speed, he ar s ressance coeffcen when ran ravels, he ressance of ar flowng hrough he unnel, he subway sysem s operang mode, he venlaon shaf s exsence, and shafs locaon and number [4]. Numercal smulaon mehod Connuy equaon [5] : Momenum equaon: κ equaon: equaon: ρ ρu = 0 x ρu p u u j + ( ρ uu j ) = + ( µ + µ ) + x x x x j x (2) ( ) ( ) ρk ρ uk µ k + = µ + + G ρ x x σ k x (3) 2 ( ρ ) ( ρu ) µ + = µ + + C1 G C2 ρ x x σ x k k (4) Where s me, u and x are velocy componen and coordnae componen; ρ and µ are densy and vscosy coeffcen of molecular;p s modfcaory pressure; µ s urbulen vscosy, s defned by urbulen knec energy and urbulen dsspaon rae: 2 k µ = ρc µ C µ σ k σ C1 C G s defned as u u j u G µ = + x j x x (6) j and represens he generaon erm of urbulen knec energy caused by mean velocy graden. Dynamc Mesh Conservaon Equaons d dv ( u u g ) da da S dv d ρφ + ρ Φ V Φ = V Γ Φ + V (7) V Where u s he flow velocy vecor; u g s he grd velocy of he movng mesh; Γ s he dffuson coeffcen; S φ s he source erm ofφ. (1) (5)

3 Appled Mechancs and Maerals Vols Model Buldng A case sudy of a ceran saon of Nanjng mero, subway Island-plaform for numercal smulaon of pson wnd, he saon's oal floor space s 11602m 2, saon lengh m, Wdh 21.20m, saon hegh 4.50 m. Accordng o he equaons of moon, use rgd body dynamcs equaons, se he rgd body moon rajecory and spors law, and couple hem o solve. Tran movemens wll be smplfed as rgd body moon, by usng C language makng self-defned funcons (UDF) fle o conrol he ran movemen. The Se of Soluon Conrol Parameers RNG urbulence model s chosen, he equaons of he second-order upwnd scheme for convecon, dffuson usng cenral dfference forma of dscree spaal doman, ransen whch adops he full-mplc me negraon for a dscree me doman, usng he PISO algorhm Transen Numercal Smulaon of Mahemacal calculaon adops urbulence model of equaon, fne volume mehod and second-order upwnd scheme; whle couplng numeraon of velocy feld and ress was based on Smplex. The se of Inal Condons and Boundary Condons Inal condons: he nal wnd s speed n each drecon s zero, gnorng he effecs of gravy on he flow.boundary condons: The flow ex a boh ends of he mero unnel s consdered as he pressure ex boundary condons. Defned he expor n relaon o amospherc pressure 0 Pa, hs s no addonal pressure effec. The nerval unnel wall nsde keeps fxed boundary condons, choose boundary condons for subway ran s mobly and execse speed of 40m/s. Fg.1 Smplfed model of sland subway plaform Fg.2 Velocy Curve of he Tran Resuls and Dscusson Analyss of he enry ran nsananeous pson wnd The resuls show ha: Fgure 3 s passenger of mpor and expor of pson wnd speed conours, can see: due o passengers lef mpor and expor s locaed n ran mpors unnel mouh of rgh above, away from ran enered saon of unnel mouh more near, so pson wnd of speed s larger, s reached 8 m/s around, arflow dsrbuon s no unform, he maxmum speed and he mnmum speed of poor value n 4 m/s around. Close o he ran, due o he effec of pson wnd, gas along he lef of passenger mpors and expors were squeezed ou of he plaform. Impors of he ran unnel dsance farher, he pson s relavely small n he rgh of he mpor mouh and he expor mouh, a some pon, s almos 0. Relave pressure of passengers abou he mpor and expor value of 0 has he followng analyss of known passengers mpor and expor o "dscharge" effec, par of pson wnd flowng from he mpor mouh and expor mouh of passenger plaforms. (a) he lef (b) he Rgh Fg.3 Passenger of mpor and expor of pson wnd speed conours

4 470 Machne Tool Technology, Mecharoncs and Informaon Engneerng Analyss he pson wnd Snce he decelerang ran Fgure4 presens smulaon came of passengers lef, and rgh mpor and expor deparmen of pson wnd of speed equvalen lne fgure see: due o passengers lef mpor and expor s locaed n ran mpors unnel mouh of rgh above, away from unnel mouh more near, so pson wnd of speed comparson bg, reached 8m/s around; passengers ou enrance of arflow dsrbuon does no unform, near ran sde, due o pson wnd of role, arflow along sars mouh was squeeze o saon offce. Impors of passenger ran unnel mpor and expor rgh dsance farher, hus he relavely small pson wnd, almos 0. (a) he lef (b) he Rgh Fg.4 Passenger mpor and expor rae conour map Analyss he pson wnd Snce he sop movng ran Fg.6 for smulaon came of passengers lef, and rgh mpor and expor Deparmen of pson wnd of speed conour map can see: due o passengers lef mpor and expor s locaed n ran mpors unnel mouh of rgh above, away from unnel mouh more near, so pson wnd of speed comparson bg, reached 4 around; passengers ou enrance of arflow dsrbuon does no unform, near ran sde, due o pson wnd of role, arflow along sars mouh was squeeze o saon offce. And passengers mpor and expor rgh of pson wnd was 4%, a hs pon abou he mpor and expor of equal wnd speed. (a) he lef speed (b) he Rgh speed Fg.5 Passenger lef or rgh speed conour map References [1] LI Yan, GAO Meng-l, ZHOU Mng-d, LI Jan-xa Characerscs of Flow Feld n Annulus Space beween Tran and Tunnel. Journal of he Chna Ral- Way Socey.2009(6):117~120 [2] Zhang Yng-chao,Fu L-mn,Transen aerodynamc numercal smula on of smplfed shape cars under condon of oppose mee sde by sde n unnel.journal of J ln Unversy.2006.(36)3: [3] Wang Fu-jun.Compuaon hydrodynamcs analyss-cfd sofware prncple and applcaon [M].Bejng:Tsnghua Unversy Publshng House,2004. [4] Takanobu OGAWA, Kozo FUJII. Numercal Smulaon of Compressble Flows Induced by a Tran Movng Ino a Tunnel. Compuaonal Flud Dynamcs JOURNAL.1994,3(1):63-82 [5] Bao Ha-ao.Numercal Smulaon of Vehcle Aerodynamc drag Coffcen Based on Dynamc Grd.Tracor Farm Transporer,2008,35(6):88-90

5 Machne Tool Technology, Mecharoncs and Informaon Engneerng / Transen Numercal of Pson Wnd n Subway Saon /