KHOAHQC NGHIEN ClTU ANH Hl/dNG CUA CAU KIEN RONG DEN Sy" THAY DOI THONG SO SONG TREN MO H I N H MANG SONG Le Thanh Chmmg, Le Xudn Tu, OS Vdn Dmmg Vien Khoa hgc Thiiy lgi mien Nam Tdm tdt Bdi bdo ndy t[.]
KHOAHQC NGHIEN ClTU ANH Hl/dNG CUA CAU KIEN RONG DEN Sy" THAY DOI THONG SO SONG TREN MO H I N H MANG SONG Le Thanh Chmmg, Le Xudn Tu, OS Vdn Dmmg Vien Khoa hgc Thiiy lgi mien Nam Tdm tdt: Bdi bdo ndy trinh bdy ket qud nghien cdu so sdnh khd ndng triet gidm sdng tieu tdn ndng luang ctia dgng ket cdu de gidm sdng khdc bdng mo hinh vdt ly De co duac su hieu biet lot han vi luang tac song vdi dgng di rong khdc Ket cdu thie nhdt cd cd hai mgt deu bd tri Id rdng hd tgo dieu kiin trao doi mdi trudng tnrdc vd sau cdng trinh Kit cdu thu hai cd mgt trudc duac bd tri Id rdng nhdm hdp thu sdng phdn xg va mat sau ldn khdng cho trao doi moi trudng trudc vd sau cong trinh Trong qud trinh tuang ldc vdi cdng trinh, sdng bi tieu tdn nhieu han bdi kit cdu hdi co mat sau ldn, nhien he sd sdng phdn xg cua kit cdu ndy lgi khd ldn so vai kit cdu thu nhdt Tu khda: Di gidm sdng kit cdu rong, h? so truyen sdng, he sd tieu tdn ndng luang, song phdn xg md hinh vgt ly 2D Summary: This paper presents the research results comparing the ability of reduce wave, energy dissipation of two breakwater structures based on the physical model This experiment is intended to provide a better under-standing of wave interactions and hollow breakwater and closed structure The first structure is opened, it is capable of environmental exchange before and after of the structure, the second structure is closed, il does not allow environmental exchange before and after of the structure In the interactive process between waves and structures Wave energy is dissipated better by second structure but the wave reflected is bigger Keywords: porous breakwater, transmission coe^fficient, dissipation coefficient, wave reflection 2D physical model \ D^T VAN DE Trong bdi cdnh tim Idem gidi phdp bdo vf bd bien va khdi ph\ic rvmg ngdp man ven bien m$t cdch bin viing tai khu v^c Ddng Bdng Sdng Cuu Long Mgt sd nghidn cuu da dua gidi phdp vd ung dgng de gidm sdng kdt cdu rdng gjfip gidm sdng, trao ddi mdi trudng tao dilu kifn thudn lgi cho biin cdt truyen qua cdng hinh vdo ben vd ldng dgng biin cdt hat mjn, ding thdi it cdn trd qua trinh di chuyin cua sinh v$t nudc Ben canh dd d nhthig vg tri can l$ng sdng thi dd dang kin dugc su Ngdy nhan bdi: 29/3/2020 Ngdy thdng qua phan bifn: 17/4/2020 Ngay duyft ddng: 20/4/2020 dung, nhien d ^ g de kin huyen thdng thudng hi han che ve mgt sd vdn dd nhu quy md ldm, nguydn vdt lifu ehu ylu Id dd hge tuang ddi khan hilm d khu virc Ding Bang Sdng Cuu Long va thai gian thi cdng ldp d^t thudng khd ddi De giai quylt van dl ndy ciia de dang kin truyen thdng, thi gidi phdp dd giam sdng dang kin 112 hinh ban nguyft (clu kifn due sdn) cd mat trudc dugc bd tri cdc l6 rdng nhdm tieu tdn sdng vd giam thieu sdng phdn xa da duac de xudt Nghien cuu hifn tai nhdm ddnh gid hifu qud, so sanh khd nang tieu tan ndng lugng sdng ciia dang kit cdu gjam sdng bdng cdu kifn be tdng diic sdn Kit clu d^ng rdng ddc trung cho xu hudng nghien cuu hifn t^i d Ddng bdng TAP CHf KHOA HOC VA C O N G N G H £ T H O Y LOI S 59 - 2020 81 KHOAHQC sdng Ciru Long, cdn kit ciu d«ng kin dugc lim bing eau kifn be tdng diic sfin ddc tnmg cho dang df truyen thing dugc cii tiin ring bdn cd dudng kmh 4.1 cm trfn mdi mdt (a) Kit ciu dfmg ring hhih chdp tir gidc TGI (b)Kit ciu dfmg kin hinh bdn nguyft BN2 Kit ciu df giim sdng d»ng kin hinh bin nguyft BN2 ed dd rfing mdt trade P,=19.7% hrong img vdi hing l6 rfing trdn duiSmg kinh THifeT LAP THt NGHIDM Kft cau df giim sdng d^ng hd hhih chdp tir giac 5.7cm (Hinh 2.1b) vi mJt sau kin TGI (Hinh 2.1a) c d m d t c h i a r a l i m m d t Ci md hinh cdu kifn dugc diiit ki bdng gd ttudc va mdt sau ttong dd mdt ttudc cd dg vdi dg ddy 20nun vi lifn kit cung vdi long bi mdt Pi=17.6% tuong Ang vdi 1018 tong bi mdt ddy mdng sdng ttdnh hifn tugng bj djch ttdn cd dudng kinh S.7em ttdn mSi mdt vi dg chuyin qui tthih thl nghifm rong mdt sau P2=12.0% hrong ing vdi 10 lo Hinh 2.1: Kit cau de gidm sdng chdp hi gidc Nghifn cdu dugc thyc hifn mdng sdng cua Vifn Khoa hgc Thiiy Igi mifn Nam cd chiiu dii 35m, cao 1.5m vi rgng 1.2m vdi hf thing thiit ldp vi phdn tich dir lifu sdng eiia HR-Wallingford Cich thiet ldp vi tri kim sdng vi ciu kifn df giam sdng duge the hifn Hinh 2.2, mdy t^o sdng dgng co diy Piston ddt cdch ciu kifn 20.5m dugc kit nii vdi hf thing diiu khifn dugc ldp trinh cd chiie ndng hip thy sdng ty dgng giiip ban che sai so t^ bifn diu vio Phia trudc cdng trinh dugc b i tri kim sdng, dd vj tri kim lin lugt WG2, 3,4, cd chuc ndng phan tdch sdng tdi va sdng phdn xa trudc cdng trinh dya vao tinh toan dugc thift lap phin mim sdng ciia HR-Wallingford Sau cdng trinh dugc bd tri kim sdng each deu khoang 4m vd kim gdn nhit each chdn cdng trinh 1.5m cd chuc ndng sy thay ddi sdng truyin sdng edng trinh Phdn cuii mdng sdng dugc thift ldp mii hip thy 82 sdng bdng di ed hf si mai m=6, myc dich df gidm thieu sdng phdn xa dnh hudng din sd lifu Kft qud kiim djnh cho hf si sdng phdn xj tradng hgp khdng cdng trinh ludn nhd hon 10% ddm bdo dnh hudng cda sdng phdn x? din kit qud djc la khdng ddng ki (theo nghifn cim Goda 2010 [21 Chakrabarti 1994 [1]) MOt lo?t cdc thi nghifm vdi diiu kifn sdng khdng diu dugc thyc hifn d muc nudc khdc (myc nude ttung binh, cao, thdp) Sdng dugc t?o theo d?ng phi JONSWAP vdi hf sd gamma (peak enhancement factor) bdng 3.3, chu ky dinh sdng dugc thay ddi tir 2s ^ 2.5s, chiiu cao sdng y nghia tir 0.07m 0.17m, dg die sdng tuong ung H,VL thay dii tu 0.015 0.043 (trong dd gid trj chiiu ddi sdng L phy thugc vio chu ky sdng vi df sdu nude) Qui ttinh thu thdp vi phdn tich dCr lifn dugc thyc hifn bdng phin mim HR DAO ( • TAI>CHlKHOAHQCVAC0NaNGHClHUYL0IS6S9-2020 KHOA HOC HR-Waliingfi)rd) Thdi gjan dac cho mdi tuang ung vdri gia hi chilu cao luu khdng chuSi thl nghifm dugc thyc hifn khodng 500 dinh de Re ={-K).14m, -K).07m, Om} (dugc xdc sdng tuong tag Tdo=500xTp (s), vdi tan sd dinh bdng hifu giOa cao trinh dinh dd vd m\rc Id SOHz Ba gid tq myc nudc thi nghifm nud'c thilt kl) o o oo o B O O H.(tn).Tti(.) o o 0 o 00 o OD O OOP ) > ^ ^ Hinh 2.2: Sa thiel lap thi nghiem Rc=Om —Mvc nirirc cao Ro=0.07m -—MvcnuOclmngU Ro=0 14m 'M^c nuAc thdp KfiT CAU G I A M S N G T H I NGHIDM Q O O O O O O O O O O O r I I I I I I I I I I I I ) I I I I I I I I I I I I I I I I I I I I I Hinh 2.3: Miic nudc thi nghifm Lo^i ddng chay qua kit eiu giam sdng dugc xdc djnh bing chi si Reynolds vdi tde nhdm sdng) chay qua lo rong, d Id dudng kinh Id rdng, v la hf so nhdt dgng Re=i^, dd u la vdn tde sdng (van " ' 'ô?'= "ãã'?' "'9 20°C (0.0101 cm^/s) Kit qud tinh todn cho TAP CHf KHOA HOC VA CONG N G H E T H O Y LOI Sfl 59 • 2020 83 I KHOAHQC" gii tri Re=31237+59239, eho thiy Re,M, giim sdng iing vdi cie kjch bin Id ddng ioig>10000 nfn ddng chiy qua eiu kifn chiy roi Bing 2.1: Thdng si thi nghifm Tham >h thi nehifm Kit ciu df giim sdng Dg rfing mdtttirdccdu kifn Pi Dd rfin;; mdt sau ciu k i ^ Pi Chiiu cao ciu kifn, h Chiiu cao luu khdng Re Chiiu cao sdng Hi Chu ky dinh sdng, T^ DO die sdng, H„o/L GUtri TG1,BN2 17.6% 19.7% 12%, 0% 0.47m 0.00m, •H).07m,+0.I4m 0.07m-K).l7m 1.2s + 2.5s 0.015*0.043 Chi si Reynolds qua df gidm sdng R e = — 31237*59239 ld:T QUA THI NGHI$M \k THAO LUAN cdng trinh (Hmo,i) trfn gid trj chiiu cao sdng tdi (H„o.i); 3.1 Tifu chi dinh gii hifu qui cdng trinh Sdng va ehfun vdi bit ky d^ng cdng ttinh df giim sdng ndo thi mft phin ndng lugng sdng sf bj phin X9 phia tnrdc edng trinh, mgt phin sf bj tifu tdn, hip thy bdi edng trinh vi phin cdn 1^ sf dugc truyin qua phia sau cdng trinh v i mdt 1;^ thuyit tiii vin di tiiiiy dgng lye hgc niytaidntiiddjnh ludt bdo toin ndng lugng va cd thi dirge thi hifn dudi d ^ g todn hgc ldng cdng thue cdn bdng ndng lugng (Burchanh and Hughes 2003): E,=E,+E+E (1) Trong dd, Et E„ E, va E,i Id ndng lugng cua sdng din, sdng truyin, sdng phan x? va sdng bj tifu tdn Va hdm cdn bdng ndng lugng cd thi duge viit l^i nhu sau: •mm (2) \ = K^+K;+K„ (3) K, = " '' Hf si sdng phdn xa dugc xdc djnh bdng gid trj chiiu eao sdng phan x? trudc cdng trinh (H„o.r) tren gid trj chiiu cao sdng tdi (Hm0.i)l Kd dugc xde djnh dya vdo kit qua cua cdng tiiirc biin dii tir cdng thirc (3): K, = \-K^-K,' (4) Cdc sdng bifn dii xung quanh cdng trinh sdng tdi tuong tde vdi cdng trinh sf tao thdnh chi dd sdng ttudc cdng ttinh Sy biin dii tilf hifn qua hf sd sdng ttudc edng ttinh dugc xdc djnh bdng ty sd giOa chiiu cao sdng ttudc edng ttinh (H„„.,) va chiiu cao sdng tdi (Hmo.i)tiieocdngfliirc(5): ^.0./ /C, = - (5) Trong dd: Trong dd chiiu cao sdng trade cdng tnnh dugc xde dinh t,i vj tri kim si trudc cdng trinh K, =—=2i Hf sd trayin sdng dugc xic djnh 3.2 Qui trinh truyin sdng bing gii trj chiiu eao sdng ttiiyin phia sau Sy fliay dii hf sfi ttuyin sdng K phy thu^c 84 TAPCHlKHOAHOCVAC»^e ^v thay ddi Id **°"8 ^"^ **°So sdnh giua kit cdu TGI vd BN2 cd thl nh§n thdy sdng phdn xa cua kit cdu gidm sdng BN2 cd xu hudng ldn hon so vdi kit ciu TGI Kit qud phan tich cho thdy kit ciu TGI ludn cho hf sd sdng phdn xa nhd hern 0.3 Hs=0.10m,Tp-1.50s Hs=0.12m,Tp=1.60s _1.0 1.0 £ 0.8 ;£o.8 e 0.6 = 0.6 b ^0.4 0.4 BSe '^0.2 SQO , -1 OTGl aBK2 gĐi? ãloj = 0.0 Rc/HmO,! 1 Rc/HmO,! Hinh 3.2: /fp so sdng phdn xg Kr img vdi tham sd thi nghidm khdc TAP CHf KHOA HOC VA C O N G N G H E T H O Y L O I S6 - 2020 85 KHOAHQC 3,4 Tifa tin ning Inyiig sdng Kit ciu gidm sdng BN2 cho hf sd tifu tdn Quan hf ding biin dugc nhdn thiy giiia chiiu ndng lugng sdng tit hon so vdi kil cau cao luu khdngttrongdii dinh df Rc/Hmw vd hf TGI, hiy nhifn sy chSnh Ifch cua hf sd tieu sd tifu tdn ndng lugng sdng qua biiu dd Hinh tan ndng lugng giOa kit ciu cd xu hudng 3.3, tire la df cing nhd cao khd ndng tifu giam din chiiu cao lim khdng dinh df tang Ifn tan ndng Itrgng sdng cua kit ciu cang ldn I D D g -'-0 ^0.8 J ZOA g Hs=0.12m, Tp= 1.60s Hs=0.10m,Tp=1.50s Hs=0.07m,Tp=1.20s 30.8 -' o° O ° S 0.6 -' n°(5 0° = 0.4 "SOJ -So J "SoJ J X 0.0 1 'o.o 1 RcmmOJ OTGl aBN2 I Rc/HmO,! Htnh 3.3: Hf sd lieu tdn ndng lupng sdng Kd ling vdl tham sd thi nghifm khdc 3.5 Sdng biin dii tni*c cdng trinh Kit qud phdn tich hf si sdng biin ddi ttudc cdng ttinh dugc tiii hifn qua Hinh 3.4, cho fliiy hf si Kr>l tiii hifn chiiu cao sdng ttudc cdng ttinh ludn Idn hon chiiu cao sdng tdi, hf si Kf cua kit ciu la khdng khac nhiiu hiu hit cdc tnrdng hgp thi n^if m, Hs=0.07m,Tp=1.20s 1.2 Hs=0.10m,Tp=1.50s Hs'O.nm Tp=l fiO» 1.2 88 1.0 dd df BN2 cd hf si Kr ldn hon df TGI 1^ '* ^°' "'f '^ '•''j' ™ *0 rang 16n sdng ttuyin "l"^ " ^ [ ^ ''™'