CFD Analysis of Aerodynamic Drag Effects on Vacuum Tube Trains

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1 Jornal of Appled Fld Mechancs, ol. 1, No. 1, pp , 019. Aalable onlne a.afmonlne.ne, ISSN , EISSN DOI: 10.95/afm CFD Analss of Aerodnamc Drag Effecs on acm Tbe Trans S. A. llan 1,. P. Panlam 1, S. Sadasan 1 and Z. Yaopng 1 School of Mechancal Engneerng, ellore Inse of Technolog, Inda Eacaed Tbe Transpor, Sohes Jaoong Uners, Chengd , Chna. Correspondng Ahor Emal: sreeas66@gmal.com Receed Aprl 10, 018; acceped Sepember 3, 018 ABSTRACT Aerodnamc aspecs of ran shapes sable for acm Tbe Tran Ssem are nesgaed n hs paper. Three feasble geomeres for he acm be ran ssem hae been consdered and modelled n hree dmensons and hae been compaonall sded sng he commercal sofare Anss Flen. Aerodnamc drag loads on hese geomeres hae been calclaed nder dfferen be pressres and speeds of he ran, hch prode nsgh on aros operang parameers ha need o be consdered hle desgnng he acm be ran ssem. The presen compaonal research shos ha, he sable acm pressre, and dfferen shapes of head and al of he ran hae sgnfcanl effecs he drag force of he acm ran n he nnel. Oerall, he ellpcal ran shape h a hegh o base rao of :1 s more effcen for aerodnamc drag redcon of he acm be ran a he acm be pressre of Pa. Keords: CFD; Aerodnamc drag; acm ran; Shoc ae; Naer soes eqaons. NOMENCLATURE e Inernal energ per n mass rblence nec energ p gas Pressre,, eloc componens n, and drecons respecel absole eloc ρ dens of gas τ scos sress λ bl scos coeffcen µ moleclar scos coeffcen rae of dsspaon 1. INTRODUCTION Trans are locomoes sed o carr cargo or passengers from one desnaon o anoher. The conenonal mode of ransporaon s epense or relael slo or a combnaon of boh. Unl recenl, rans hae been lmed o mamm speeds of mph. B, n he crren generaon, here eerhng s mong fas, here s a need for reachng desnaons faser, so ha me s no ased on rael. Ths has led o he formlaon of ne hgh speed ransporaon neors sch as acm Tbe Trans. Thogh, sll a he concepalaon sage, scenss hae made hge progress n hs feld. acm Tbe Trans, heorecall speang, can reach speeds of p o 1000 m/h, Zhang 01. Ths ll hence be he fre of grond ransporaon. The acm be ran ssem needs o ae no consderaon man more parameers n comparson o he conenonal rans. Km e al. 011 and Zhang e al. 011 shos ha he aerodnamc drag, deelopmen of shocs and manenance of lo pressres n he be are he maor drabacs hch need o be conrolled n order o ge a sccessfl ransporaon ssem. Hence here s a reqremen o sd he aerodnamc drag acng on hese bodes n order o fnd o he sable ranges of pressre o be mananed n he nnel, eloc ha he rans can rn and he sable geomer for he rans, Zh-n e al. 005 and Chen e al. 01. Kon e al. 001 hae shoed ha he acm be rans need o rn a lo pressre n order o achee he hgh speed. B mananng he nnel a eremel lo pressres s an nsrmonable as and hence an acheable leel of pressre o be mananed n he nnel needs o be denfed. The speed a hch he rans rn canno eceed a ceran leel as hs old resl n shocs hch old desro he ran ssem. Hence, a sable speed h hch

2 304 he ran can rn ho he formaon of nconrolled shocs need o be denfed as ell. The geomer of he ran s anoher parameer ha s crcal o he modellng of he acm be ran ssem. Dfferen geomeres of rans hae been denfed and modelled. Bbn e al. 013 fond ha a blocage rao of 0.5 old be mos approprae for acm be ransporaon. Ths effec ang no consderaon h he assmpon ha he flo s sead hree dmensonal, compressble. The Naer-Soes eqaons copled h -epslon rblen modellng ere soled o calclae he aerodnamc drag acng on he ran.. METHODOLOY.1 Eqaons Of Fld Moon The compressble flo Naer Soes Eqaons copled h he - eqaons for rblen modellng hae been soled sng he Flen sofare. The follong assmpons hae been consdered drng he process: Sead flo Compressble flo Three dmensonal, rblen flo Flo smlar o ha of a calorcall perfec gas The aros goernng eqaons hch hae been sed n he analss are as follos: Conn Eqaon: 0. 1 Momenm Eqaon: X-Momenm p Y-Momenm p Z-Momenm p Energ Eqaon...5. p p p T T T q e e Eqaon:...6 M b S Y EQUATION: S C C C b. Deals of acm Tbe Tran Ssem The schemac represenaon of acm be ran ssem consdered n he presen sd s shon n Fg. 1. The aros dmensons of he acm be ran ssem are as follos: Tran Dameer = m Tran Lengh = 40 m Tnnel Dameer = 3. m Tnnel Lengh = 00 m Blocage Rao = 0.4 The ran shape has been assmed as an asmmerc bod. Addonall he flo ndced b he ran moon has been aen as hree dmensonal n nare. The smlaons hae been carred o o replcae he nd nnel es of a hree dmensonal ran shape. Ths he bod has been aen as saonar and he nle of he

3 compaonal doman has been se h eloc correspondng o ran speed and nnel amben pressre. The oer srfaces of he ran ere reaed as no slp alls. Pressre ole condon has been se for he ole of he compaonal doman. The nnel nner srface has been consdered as a all mong n drecon. Fg. 1a. acm Tbe Tran Ssem..3 eomer and Mesh Deals The meshng of he acm be ran ssem has been carred o sng ICEM CFD Sofare. The enre compaonal doman has been meshed sng heahedral mesh and a he nle and ole of he ran O-rd has been sed n order o deelop een fner meshes as hese locaons are sense o hgh flcaons of shocs. Ths also prodes proper meshng a hese cred enes as he meshng mgh no be eenl placed along he cre. The meshed model srface mesh of he opmed ran model s porraed n Fg. a and ha of slce mesh n Fg. b. Fg. 1b. Bondar condons n he compaonal doman. Fg. a. Meshng of he acm be ran ssem. Fg. b. Slce mesh of he acm be ran ssem..4 Bondar Condons The aros pars of he acm be ran ssem hae been shon n Fg. 1 and he dfferen bondar condons specfed n compaonal doman of he crren smlaons are also shon n Fg.. The pressre has been ared beeen 10135, , and Pa and each me he smlaons hae been performed. Smlarl, he Mach nmber has been ared based on he desred speed of he ran and each me he smlaons hae been performed. The dfferen Mach nmbers sed are 0.7, 0.79, 0.864, and The aros bondar condons sed are as follos: Inle: Pressre nle h a pressre of Pa and a a Mach nmber of Tran: Consdered o be a all mong n drecon. Ole: E of he nnel s specfed as pressre ole. Tnnel: Consdered o be saonar all h no slp condon. 3. RESULTS AND DISCUSSION In he presen compaonal sd, he man dea s o fnd sable parameers manl, operang acm pressre, speed of he ran and he shape for he acm be ran ssem. Ths noles solng he eqaons menoned earler sng he Flen Sofare. Once he smlaons hae been carred o, he resls hae o be analsed n order o ge he sable parameers. 3.1 Comparson of Pressre In hs sage, he ellpcal ran h a hegh o base rao of :1 has been aen and sng hs geomer and eepng he eloc of he nnel as 50 m/s, he smlaons ere carred o on dfferen pressre leels o be mananed n he nnel sch as Pa, Pa, Pa and Pa. The drag force ales ere comped and hae been ploed h respec o he pressre ales n Fg. 3. I s sble ha as he pressre ncreases, he force also ncreases. I can also be noed ha as pressre decreases beond a ceran pon, he drop n force s neglgble. Consderng he cos and mplemenaon ease facors, rng o manan er lo pressres hn he enre lengh of he nnel ll be er epense and s er dffcl o achee. Hence, consderng all hese facors, s safe o manan nnel amben pressre almos 100 mes lesser han he amospherc pressre. 3. Comparson of Mach Nmber The crren rans rn a mamm speeds of abo 100 m/s. B he acm be rans can rn mch faser han hs b s necessar o compe he sable eloc h hch hese rans can rael as here are nmeros drabacs of rnnng a hgh speeds. Hence n he ne sage of he smlaon and analss, he sable eloc h hch he ran can rael ho mch shocs and dsrbances as deermned, hch n rn helped 305

4 Table 1 Drag force and drag coeffcen correspondng o aros eloces eloc Mach Nmber Drag ForceN Drag Coeffcen m/s n calclang he Mach nmber and Renold s nmber. In hs case oo, he ellpcal ran geomer h a hegh o base rao of :1 as consdered for he smlaons and he pressre mananed n he nnel as Pa. Smlaons ere carred o for dfferen eloces sch as 50 m/s, 75 m/s, 300 m/s, 35 m/s, 350 m/s and 375 m/s and he force acng n each case has been ablaed n Table 1. Fg. 3. Force acng a dfferen pressre ales h a eloc of 50 m/s and a blocage rao of 0.4. The Renold s nmber as calclaed for he nddal eloces and hese ales of Renold s nmber ere ploed h respec o he drag force and hs graph s shon n Fg. 4. speeds normal shocs ll be formed hch affec he sabl of he ran. On ncreasng he Mach nmber frher, reaches he spersonc regon. If he rans ere o rn n spersonc condons, more shocs old be prodced and ll be er dffcl o sable he ran. The sbsonc range hch s beeen Mach nmber 0.3 and 0.8 s beer as here old no be an shocs creaed b he am of he acm be ran s o achee er hgh speeds and ha s no possble f he ran rns n he sbsonc range. The Mach conors correspondng o dfferen eloces are shon n Fgs. 4a-f. The Mach nmber conors clearl sho he spersonc nare of he flo donsream of he ran bod. Ths can be arbed o he flo pah araon reslng from he presence of ran shape nsde he consan area nnel. As he ran speed ncreases he shoc srcre donsream of he ran become more comple. Sch srong shoc neracons on he nnel all can rpre he nnel n long rn. Moreoer, hs saon ma eleae he dffcl leel n preparng he nnel for anoher rn. One possble solon o aod sch comple shoc srcre, hle mananng hgh ran speed s heang of he nnel. Hoeer, he economc feasbl and comfor leel of hs need o be addressed before proceedng h hs proposal. Fg. 4a. Mach conor correspondng o a eloc of 50 m/s. Fg. 4. Force acng correspondng o dfferen eloces 4.. I can be noed ha he force ncreases gradall nl a Renold s nmber of afer hch he force ale shoos p. Ths ale of Renold s nmber corresponds o a Mach nmber of and a eloc of 35 m/s. Mach nmbers rangng from 0.8 o 1.0 corresponds o he ransonc range. When he ran rns a sch Fg. 4b. Mach conor correspondng o a eloc of 75 m/s. 306

5 The drag force eperenced b he ran needs o be assessed before choosng a parclar ran speed for real me rn. The man drag conrbor o he oal drag on he ran s pressre drag. Hence o ndersand he pressre araon oer he ran bod a dfferen ran speeds, a srface pressre comparson s made n Fg. 4g. As s clear from hs fgre, he mamm pressre s acheed a he fron sagnaon pon of he ran a all speeds. Moreoer, he srface pressre ales fond o be ncreasng h ran speed, especall a he fron regon of he ran. The pressre a he head secon of he ran reman almos nalered a all speeds. In Fg. 4c, he shoc aes are esng a he rear sde of he acm ran and he oblqe shoc aes coe h he normal shoc aes ha are deeloped b he connos refecon and neracons beeen he nnel and he acm ran alls. Hoeer, he srengh of hose neracons s comparael less p o he eloc of ran s 35 m/s. I s o be noed ha he drasc ncrease n aerodnamc drag s generang hen he Mach no eceed one or speed of acceleraed flo feld eceeds 35 m/s as n Table1. There s a consderable ncrease n srface pressre hen eloc ncreased from 35 m/s o 350 m/s. Ths old be de o formaon of shoc aes. Ths nference s agan ell sppored b he sdden rse n drag obsered n Fg. 4g. Afer ang hese aerodnamc aspecs no consderaon he sable ran eloc has been proposed as 35 m/s. Fg. 4f. Mach conor correspondng o a eloc of 375 m/s. Fg. 4g. Pressre araon along he ran for dfferen eloc a Pa. 3.3 Smlaon Of Tran h Dfferen Shapes The ne sep s o decde on hch geomer old be feasble for he ran. There are hree dfferen geomeres consdered and he are shon n Fgs. 5a-c Fg. 4c. Mach conor correspondng o a eloc of 300 m/s. Fg. 5a. Ellpcal head and al h a hegh o base rao of 1:1. Fg. 5b. Ellpcal head and al h a hegh o base rao of :1. Fg. 4d. Mach conor correspondng o a eloc of 35 m/s. Fg. 5c. Tranglar head and al h a boom o hegh rao of 1:. Fg. 4e. Mach conor correspondng o a eloc of 350 m/s. In hs sage, he smlaons hae been carred o h he sable pressre of Pa, eloc of 35 m/s and Mach nmber of on he hree dfferen geomeres and her resls are ablaed n Table. 307

6 Table Force ales correspondng o aros geomeres EOMETRY FORCE N ISCOUS COEFFICIENT Sem crclar 1: Ellpse : Trangle From he Table, s noced ha among he hree pe of sreamlned geomer,he ran h semcrclar al and head possess he mamm drag force, hle he ellpcal geomer h a hegh o base rao of :1 has he loes ale of drag force. Ths resl shos ha, he aerodnamc drag of s hghl affeced b he head and al shape of he ran. The pressre conors of all he geomeres are shon n Fgs. 6a-c. Fg. 6a. Pressre conor correspondng o he ellpcal ran h a hegh o base rao of :1. Fg. 6b. Pressre conor correspondng o he ellpcal ran h a hegh o base rao of 1:1. Fg. 6c Pressre conor correspondng o he ran h a ranglar head and al. On analss of he Mach and pressre conors, can be seen ha he ellpcal geomer h a hegh o base rao of :1 seems more feasble becase of he loer ales of Mach nmber and pressre occrrng hrogho he acm be ran ssem. The srface pressre araon ploed n Fg. 6g also shos he sabl of aboe menoned ellpcal model. The negraed pressre force can be obsered o be mnmm for hs model. Fg. 6g - Pressre araon along he ran for hree dfferen shapes of head and al. 4. CONCLUSION A compaonal sd has been performed on he acm be ran ssem and aros sable parameers hae been denfed. The drag force acng n he ssem eeps arng and needs o be a opmm leels. Throgh he smlaons as sble ha he drag force ncreases h decreasng pressre and hence he pressre has o be mananed a a lo ale hch s acheable and feasble n erms of cos and consrcon. The fases eloc h hch he ran can rael h lle shocs and braons has also been analsed and fond o be 35 m/s, hch corresponds o a Mach nmber of hch s n he ransonc regon, beond hch he ssem old rn no a spersonc regon here he effecs of shocs old be more seere. A comparson beeen hree dfferen ran shapes has also been gen and based on he ales of drag force he sable geomer has been arred a, hch s he ellpcal ran h a hegh o base rao of :1. REFERENCES Bbn, S. and S. K. Mherea 013. Nmercal Inesgaon of Aerodnamc Drag on acm Tbe Hgh Speed Tran. In ASME 013 Inernaonal Mechancal Engneerng Congress and Eposon pp. 013T14A T14A048. Amercan Soce of Mechancal Engneers. Chen, X., L. Zhao, J. Ma and Y. L 01. Aerodnamc smlaon of eacaed be magle rans h dfferen sreamlned desgns. Jornal of Modern Transporaon 0, Km, T. K., K. H. Km and H. B. Kon 011. Aerodnamc characerscs of a be ran. Jornal of nd engneerng and ndsral aerodnamcs 991, Kon, H. B., K. H. Jang, Y. S. Km, K. J. Yee and D. H. Lee 001. Nose shape opmaon of hgh-speed ran for mnmaon of nnel sonc boom. JSME Inernaonal Jornal Seres C Mechancal Ssems, Machne 308

7 Elemens and Manfacrng 443, Zhang, Y. 01. Nmercal smlaon and analss of aerodnamc drag on a sbsonc ran n eacaed be ransporaon. Jornal of Modern Transporaon 01, Zhang, Y., D. Oser, M. Kmada, J. Y and S. L 011. Ke acm echnolog sses o be soled n eacaed be ransporaon. Jornal of Modern Transporaon 19, Zh-n, S. H. E. N On Deelopng Hgh- Speed Eacaed Tbe Transporaon n Chna [J]. Jornal of Sohes Jaoong Uners,,