Nghien cufu & Trao doi
M 6 H I N H Ltfdl LONG MO PHONG THUY TRIEU VINH BAC B O
CN. Dffcfng Van Phiic' , PGS.TS. Nguyin Tho Sao^'Phong Bao dam hang hai - Bo Tff lenh Hai quan
^Trffdng Dai hoc Khoa hoc Tif nhien, DHQG Ha Noi Tdm tat: Bdi todn thuy trieu Bien Ddng vd vinh Bac Bd dd dugc nhieu tdc gid nghien cvtu tren md hinh sd, tuy nhien cdn chi tie't hda d cdc vung ven bd cd dia hinh phifc tgp. Trong bdi bdo ndy tdc gid trinh bay viec xdy difng md hinh thdy ddng life sd dung phuong phdp sai phdn hUu hgn vdi ky thuat ludi long. Ky thuat ndy cho phep tinh todn mgt vung chi tiet md khdng cdn tdng do phdn gidi tren todn mien Idn, do dd khac phuc dugc hgn che've bd nhd mdy tinh vd gidm thdi gian tinh todn. Sifphd hgp giUa ke't qud tinh todn vdi thifc do cho thay khd ndng dp dung md hinh rat hien thUc. . . ,
1. MoT dau
Vinh Bac Bd la mdt trong hai vinh Idn d Bien Ddng, dffdc bao boc bdi Viet Nam va Trung Qud'c, nam trong khoang ldnh do 105°40-110°00E, VI do tff 17°00-21030N (hinh 1). Day la vinh nffa kin, thdng ra Bien Ddng qua cffa phia nam va eo bien Quynh Chau. Do sau trung binh ciia vinh Idioang 40 m, day vinh tffdng dd'i bang phang va thoai dan theo hffdng ddng nam. Bd vinh Idiuc khuyu, tao ra nhieu vung, vinh ven bd, cd nhieu dao nhd tap trung d khu vffc phia bac va phia tay (khoang tren 2000). Nhffng dac trffng dia hinh nhff tren lam cho che' do thuy dong life trong vinh trd nen phffc tap [1].
Vinh Bac Bo cd che' do thiiy trieu vao loai dac sac d Bien Ddng vdi nhieu dang, trong do nhat trieu deu chie'm phan Idn dien tich vinh.
Do Idn thuy trieu trung binh d phia bac vinh Idioang 3-4 m, giam dan xudng phia nam de'n gia tri khoang dffdi 1 m. Tinh chat thiiy trieu cung khac nhau giffa phia tay va phia ddng vinh.
Tinh toan thiiy trieu la mot trong nhffng bai toan thiiy dong life kinh dien da dffdc nhieu tac gia nghien cffu, do tam quan trong nd trong
khai thac tai nguyen bien. Md phdng lan truyen trieu bang he phffdng trinh nffdc ndng hai chieu vdi viec giai bang so' tri da trd nen truyen thd'ng, trong dd phffdng phap sai phan hffu ban dffdc nhieu tac gia trong nffdc sff dung.
Cac cdng trinh nghien cffu thiiy trieu hoac hen quan de'n thiiy trieu Bien Ddng cua Sergeev (1964), Nguyen Ngoc Thuy (1969), Dang Cdng Minh (1975), Nguyin Tho Sao (1988), Pham Van Huan (1994), de tai KT.03.03 (1991-1995), Dinh Van Manh [5], Phung Dang Hie'u [2] deu sff dung cac phffdng phap so. Ndi chung, cac sd do so' ndi tren (chii ye'u la sai phan hien, mot so'it la nffa an hoac an) dap ffng viec md phong thuy trieu Bien Ddng. De nang cao do chinh xac cho tinh toan thiiy trieu, dac biet d nhffng Idiu vffc ven bd, ndi cd dia hinh bie'n ddi phffc tap, can cd nhffng cai tie'n theo cac hffdng: thay ddi thuat toan, tang do phan giai ciia Idiu vffc tinh toan hoac sff dung lffdi da cap. Nghien cffu nay tie'p can phffdng phap sai phan hien, sff dung ky thuat lffdi long tffdng tac 2 chieu min - thd. Uu diem ciia ky thuat nay la cho phep nghien cffu mot vung chi tie't ma khdng can phai tang do phan giai cho toan vung bien Idn, do dd nang cao do chinh xac ciia ke't qua nhffng tie't kiem bo nhd va thdi gian tinh toan tren may tinh [4], [5].
Ngffdi phan bien: TS. Pham Van Huan
32 Tap chi Khi ixiijng Thuy van * Thang 5/2008
Nghien ciJu & Trao doi
2. Mo hinh lffdi long tinh toan thuy trieu va chieu, dffdc thie't lap tren he toa do De cac vdi:
dong chay tong hdp htfdng ddng (Ox); hffdng bac (Oy) va hffdng
^ , V , , , , len tren (Oz); cac phffdng trinh chuyen ddng a. HephUdng trinh chu dgo
d day sff dung he phffdng tnnh nffdc ndng 2 la:
tmmaeuiii
. / • • • • • / •
• • • - v / -
TM*M ' /
r"
<•—- {-^
•^.^*^^
/
9w du du ^ 1 9p. 9f ^r-^r xr A n ^
—-hM —+ v > = £ ^ - g - 5 - + ^—'--{-Nf,Au (1) 9f 9x 9v Po ^ ^^ Po^
dv dv dv ^ 1 S o 5 f ^y^'^v Ar A {0\
— -t-M — -i-v— + fu = ^-^-g^- + — --^Nf,Av UJ
dt dx dy PQ dy dy p^D
va phffdng trinh lien tuc la:
dg d(uD) d(yD) at dx - - t - - dy = 0
Hinh 1. Khu vUc nghien ciiu
(3)
trong dd: u,v - cac thanh phan van tdc trung binh do sau theo phffdng x va y, tffdng ffng; D - dd sau tdng cong; A„=(|^-H|^^ toan tff Laplacian;
OX oy
N^ - he sd nhdt rdi ngang;
sua't gid; : Rj^Uyju
^W
-* = R,vylu^+V^
- ffng sua't ma sat day;
- la he sd ma sat gid tffdng ffng la cac thanh
•y - V ^
va ma sat day; U^,V^
phan van td'c gid theo phffdng x va y;
/ G 7,269x10"^ sin^-tham sdCoriohs; tp -\l do dia ly; Po - mat do nffdc bien; Pa - ap sua't khi quyen tai mat bien; g - gia td'c trong trffdng.
Cac dieu kien bien: tai bien cffng sff dung dieu kien bien khdng tham; tai bien long la
dieu kien bien phat xa tff do, hoac mffc nffdc, hoac van td'c; tai mat cd gradien ap sua't Idii quyen va ffng sua't gid; tai day la ffng sua't ma sat day. Trong bai toan thuy trieu thuan tuy cd the bd qua gid va ap sua't khi quyen.
b. PhUdngphdp gidi so'
Lffdi so le khdng gian (sd do Akarawa C) dffdc lffa chon (hinh 2, 3). Gach ngang va gach doc trong hinh nay bieu d i l n diem tinh cho thanh phan van tdc , va dau thap cho mifc nffdc bien . Cac vi phan dao ham rieng dffdc bie'n ddi thanh cac sai phan difa tren khai trien chudi Taylor da dffdc d i n ra trong nhieu tai lieu chuyen nganh toan va vat ly hai dffdng.
Vdi lffdi khdng gian va thdi gian lffa chon nhff tren, he phffdng trinh sai phan cho (1 - 3 ) dffdc viet nhff sau:
llA UJL^-L(U'" D"' -U"" D"" ^--Iv" D" - v " D" ^
j,k j,k
^[(""..+<.)' -fe+«;->.0']-^-"^ fe.i -<.-.)
8Ax
f.b,m
(4)
(5)
+ ^ ( " j . . . * + « ; - . . * + « ; . . ! + < . - : - 4 < . )
N,Tap chi Khi ttfgfng Thuy van * Thang 5/2008
33Nghifen citu & Trao dd'i
v " : ' - v ; . _ 1
-fuj
T 2Ax
1 (Pal,,,-Pal,) g
« M ( V ; U - V ; U ) - ^
fe.,+v;,) -fc4v;,_,)^
h
r^'"'
h,m (6)/? P.D:_J, P,D:.^^
+ !lL(v'" -fv'" 4v'" 4v"' -4v"' ) N
Trong dd: ; 7 / = 0,25(v;^, 4v;_,,, 4v;_,,,_, 4v^Vi)
«,/=o,25«,, +<,„+<,,,,, +«;,,,,)
(7)
Ap sua't khi quyen, ffng sua't gid, do sau dffdc xac dinh tai tam d. Tai cac diem tinh van tdc, do sau dffdc xac dinh bang each lay trung binh, vi du tai diem tinh dffdc xac dinh bang,
£)„^, =0,5(D^,4Z)^_iJtai diem tinh v lai)„,^.,=0,5(D,,,4Z)^_,_,).
k * 1 -
k -
k-1
1 1
- • ^ -
1
1 - -t- -
+ \ -
1
1
\ - + —
vaw i
— 1 —
— i — -1- -
- + -
—1—
t-2 H r 1
Hinh 2. Ludi so le theo khdng gian
l=m+1
m
i .
^ ^ ^ ^ ^ -^ ^>^-'^.--^ ^ ^
^^ ^ ^ ^ ^
^ ^ .^ ^ ^
^ J>^-"^ ^ ^
^^ ^^ ^>-^ ^^ ^^
^ ^ ^ ^ ^
^ J>^"^.y^ ^ ^
^ ^ ^ ^ ^
^ ^ ^ .^ ^
^ ^''^^ ^ ^
^ / ^ ^ ^ ^ Hinh 3. LUdi tinh khdng - thdi gian Dd'i vdi sd do sai phan hien, tieu chuan dn dinh xac dinh thdng qua md'i hen he giffa bffdc
Ididng gian (h), bffdc thdi gian (I) va van td'c lan truyen sdng dai C = ^[gH qua bieu thffc (8), dffdc goi la dieu Iden Courant-Friedrichs-Levy (CFL):'
T < h h
2 V i ^ 2C
(8)c. Ky thuat lUdi long vd quy trinh gidi
Qua trinh lan truyen sdng dai xay ra tren quy md khdng gian rong. Ne'u giai toan bo khdng gian mot each chi tie't bang each tang do phan giai, thi thdi gian may tinh ddi hdi se cffc Idn. Mot each giai quye't van de nay la chia mien tich phan tdng quat ra cac mien con nhd hdn. Vi xem xet qua trinh trong cac mien khac nhau vdi do phan giai khdng gian khac nhau, ta se can de'n bien phap ke't ndi mien cd do phan giai thd vdi mien cd do phan giai min, va di nhien vdi bffdc thdi gian tinh toan khac nhau.
Ky thuat ke't ndi cac mien cd do phan giai khac nhau nay chinh la ky thuat lffdi long. Diem quan trong la phai dam bao sff bie'n ddi trdn, Uen tuc d hai mien va tren bien chung.
Trong lffdi long tffdng tac 2 chieu, cac bie'n tff lffdi thd cd the truyen vao lffdi min thong qua noi suy tuye'n tinh tai bien lffdi min, va cac bie^n tinh toan tff lffdi min dffdc cap nhat cho lffdi thd trong cac bffdc thdi gian ke tie'p. Diem dang lffu y d day la cac bie'n ciia lffdi thd da dffdc chinh xac hda them trong cac tinh toan tren lffdi min d quy md khdng gian va thdi gian chi tie't hdn. Chinh sff tac dong trd lai nay lam 34
Tap chi Khi ttftfng Thuy van * Thang 5/2008
/ v ' .
Nghien ciJu & Trao doi
cho ke't qua tinh toan tren lffdi thd dffdc cai thien khi cd mat lffdi min. Mot each ke't nd'i giffa cac bie'n tren lffdi thd- min dffdc trinh bay dffdi day.
Ky hieu cac bie'n trong lffdi thd bdi cac chff cai viet hoa, gach dai, chff thap Idn va trong lffdi min la chff thffdng, gach ngan, chff thap nhd (hinh 4).
Hinh 4. Lien ke't mien liidi min vd lUdi thd Nhan tha'y cac gia tri tren bien ciia lffdi min cd the d l dang nhan dffdc bang each noi suy tuye'n tinh tff cac bien tren lffdi thd. Vi du:
chung cho lffdi min tff gia tri ciia cac bie'n tren lffdi thd, tinh toan mffc nffdc , ? / ' " / > ^/ cho lffdi min vdi quy trinh tffdng tff cho mien lffdi thd. Viec tinh toan nay dffdc lap lai mot so'lan tren lffdi min phu thuoc bffdc thdi gian lffa chon tren hai lffdi.
Bffdc 3: Gan cac gia tri tinh toan dffdc d bffdc thdi gian m+1 cho bffdc thdi gian m, trong dd da cap nhat cac gia tri tff lffdi min, lap lai cac tinh toan cho lffdi thd tie'n trien theo thdi gian.
3. Ket qua ap dung mo hinh tinh toan thuy trieu cho vinh Bac Bo
- - " a. Cdc ddc tning cua mien tinh
Mien lffdi thd (bffdc lffdi 0,1 do a 11,1 km) gidi ban trong khoang tff 17°00 - 22°00 N, 105°30 - 110°00 E, mien lffdi min (0,0333 do
« 3,7 km) gidi ban trong khoang tff 20°12 - 21°48 N, 106^30 - 108^30 E. So heu dia hinh dffdc xff ly tff ngudn sd heu TOPEX2. Tdng sd d lffdi cho mien lffdi thd la 45 x 50 d va cho mien lffdi min la 60 x 45 d.
u(JS,k2) = v(j7,k2) =
" ^U(J5,K2) + ^^U(J5,K3) 2a
a- 2a
2a (9)
^V(J5,K2) + ^^V(J4,K3) (10) 2a
Trong cac cdng thffc tren, gia thie't khoang each lffdi tff lffdi min sang lffdi thd tang a lan (tren hinh 4, or = 3 ). Uu the ciia each tie'p can nay d chd, bat ky sff tang do phan giai khong gian tff lffdi thd de'n lffdi min, ne'u dffdc bieu thi bang so'nguyen le a = 3,5,7,... deu cd the thifc hien theo cung thuat toan tren [4].
Vdi each sai phan va ky thuat lffdi long da trinh bay, ta cd the tdm Iffdc quy trinh giai nhff sau:
Bffdc 1: Tinh toan mffc nffdc S""^' tff phffdng tnnh hen tuc (4),^'"+' tff phffdng tnnh (5),
v"*' tff phffdng trinh (6) cho mien lffdi thd.
Bffdc 2: Noi suy gia tri cac bie'n tren bien
Mat do nffdc lay khdng ddi cho toan bien la 1026 kg/m^, he soma sat gid: =0,0006 - 0,003, he soma sat day: /?y=0,001 - 0,003, he sdnhdt rdi Nf^ =1 - lOOmVs. Thdi gian tinh toan la 720 gid (30 ngay). Bffdc thdi gian la 30s tren lffdi thd va 6s tren lffdi min, bffdc khdng gian tffdng ffng tren 2 lffdi la 0,1 va 0,0333 do (11,1km va 3,7km).
Cac dieu kien bien ciia md hinh thuy dong life la tac nhan quye't dinh sff chuyen dong cua nffdc bien. Tai bien cffng, cac thanh phan van tdc phap tuye'n lay bang khdng. Tai bien long, md hinh sff dung duy nha't dieu kien bien dao ddng mffc nffdc. Lffu y rang, ngoai hai bien long phia nam va phia ddng vinh, eo Quynh Chau cung dffdc coi la bien long, vi theo danh gia ciia Nguyin Ngoc Thuy [3], nang Iffdng thiiy trieu qua eo nay rat dang ke. Hai chudi mffc nffdc dffdc tinh toan tff md hinh Delft-3D
Tap chi Khi tufi^ng Thuy van * Thang 5/2008
35Nghidn cuTu & Trao doi
cho 4 diem bien Cffa Tiing, Tram A, Tam A va Cape Kami trong thdi gian ffng vdi 2 thdi ky cd sdlieu thffc do de hieu chinh tai Bach Long VT nam 2001 va kiem chffng tai Tra Cd nam 2000.
b. Hieu chinh md hinh
Chuoi mffc nffdc thifc do tai Bach Long VT tff OOh/23/06/2001 - 23h/24/07/2001 dffdc chon de hieu chinh md hinh. Cac tham sd ciia md hinh la he sd ma sat day Rf va he sd nhdt rdi N^ , trong dd he sd ma sat day la tham sd nhay cam va quan trong hdn nhieu so vdi he sdnhdt rdi. He soma sat day tff 0,001 - 0,003 vdi bffdc thay ddi 0,0002 dffdc sff dung de hieu chinh md hinh, he sdnhdt rdi ngang dffdc chon khdng ddi A'^^ =10mVs. Qua danh gia sai sd've pha va do Idn giffa tinh toan va thffc do tai Bach Long VT, i?^ =0,0016 cho ke't qua tinh toan phu hdp nha't, sai so' quan phffdng theo cdng thffc (11) la ±18,0 cm.
m=± [vv]
= ±18,0 cm
(11) Trong dd, v cac hieu giffa mffc nffdc tinh toan va mffc nffdc thffc do, n _sd' Iffdng quan trac; da'u lay tdng theo thdi gian tff tj de'n tjj.
20 1.5
I rn I as
I 0.0
I -°'
0 50i 1'Q0 1:50 200 250^ 300 350 400' 450 500' 550'- 600 Sm 700 750^
thm ^an iqiaif
Hinh 5. Miic nUdc thUc do vd tinh todn tgi Bach Long Vi (td 06h ngdy 23/06/2001) c. Kiem chiing md hinh
0 5D 10Ot50 2 0 O 2 5 0 3 0 O 3 6 O « ) 0 4 5 0 5 0 O 6 S 0 6 0 O 8 5 O 7 O 0 7 5 O l l i M BBn Igio)
ITinh 6. Miic nUdc thiic do vd tinh todn tgi Trd Cd(til05h ngdy 20/05/2000) Ke't qua tinh toan mifc nffdc tff md hinh dffdc so sanh vdi chudi so heu thffc do 30 ngay tai Tra cd (hinh 6) cho tha'y kha phii hdp vdi thffc do, dac biet la ky nffdc cffdng. Sai so' quan phffdng ve bien do la m^ = ± 23,0 cm. Thdng qua ke't qua hieu chinh va kiem chffng tren day, he sd ma sat day va he so' nhdt rdi ngang phu hdp cho md hinh tffdng ffng la Rf = 0,0016 va /V^ =10 mVs.
Cac ke't qua tinh toan dao dong mffc nffdc tff md hinh cho Bach Long VT nam 2001 va cho Tra cd nam 2000 rat phu hdp vdi thffc do, do dd cd the khang dinh rang sd heu dia hinh cho vinh Bac Bo va cac tham so' lffa chon la phu hdp.
d. ThUc nghiem so'tren md hinh vdi ky trieu thdng 7/2007
Da chon thang 7 nam 2007 de thffc nghiem sd'ciia md hinh tren cd sd so sanh ke^t qua tinh toan vdi thffc do va ke't qua tinh toan tff md hinh Delft-3D tai Hdn Da'u. Tren hinh 7 tha'y rang mffc nffdc tinh toan tff chffdng trinh so vdi thffc do cd sai sdm^ = ± 30cm, trong khi sai sd giffa tinh toan tff md hinh Delft-3D vdi thffc do la m^. = ± 27cm. Khi so sanh tinh toan tff chffdng tnnh vdi tinh toan tff md hinh Delft-3D tha'y rang hai ke't qua nay kha triing nhau ca ve bien do va pha. Dieu nay cho ta by vong rang ne'u thiet lap dffdc dieu kien bien long td't hdn (sff dung nhieu sdng hdn thay vi 4 sdng trieu M2, S2, KI, 0 1 ) ke't qua tinh toan cd the chinh xac hdn.
36
Tap chi Khi ttfgfng Thuy van * Thang 5/2008
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 Thdi gian (gio)
Nghien cihi & Trao doi
Hinh 7. Ket qud tinh todn miic niidc tUchUdng trinh, md hinh Delft-3D vd thiic do tgi Hon Ddu thdng 7 ndm 2007
22
21 :
•m •
i a 7
XT
IQB 107 IDS KJnIide
Hinh 8. Trieu liiu trong vinh Bac Bg thdng 7 luc chan trieu, dinh trieu
a) Chan trieu
Ke't qua tinh toan ddng trieu cho vinh Bac Bd thang 7 nam 2007 dffdc trinh bay tren hinh 8 cho 2 thdi diem dinh trieu va chan trieu.
Theo dd tdc do ddng trieu trung binh tren toan vinh Bac Bo khoang 0,3m/s, hai khu vffc cd ddng chay manh la eo Quynh Chau va ven bd phia tay dao Hai Nam. Td'c do Idn nha't d eo Quynh Chau khoang l,3m/s va Idn nha't d phia tay dao Hai Nam khoang 0,8m/s. Hffdng va tdc do ddng trieu the hien ro nha't vao thdi gian nffdc dang hoac nffdc rut, vao thdi gian nay hffdng ddng chii ye'u chay doc theo true vinh.
e. Ddnh gid hi^u qud md hinh
Nhieu phan mem thffdng mai ve thuy dong lffc hien dai nhff Delft-3D, Mike 21..deu sff dung ky thuat lffdi long. Nd dem lai nhffng hieu qua he't sffc ro ret khi tinh toan cho cac viing bien chi tie't can do phan giai cao. Xet 2 trffdng hdp: 1) tinh toan cho toan vinh Bac Bo vdi
b) Dinh trieu
bffdc khdng gian 3,7 km va 2) sff dung ky thuat lffdi long vdi mien tinh thd va min nhff da trinh bay tren hinh 1.
Kich thffdc mien tinh cho trffdng hdp 1 la:
135 X 150 = 20250 6, trong khi kich thffdc mien tinh cho trffdng hdp 2 la: 45 x 50 + 60 x 45 = 4950 d. Nhff vay bd nhd can cho trffdng hdp 2 chi cdn bang mot phan tff so vdi trffdng hdp 1, giam khoang 75 % ve dyng Iffdng nhd.
Ne'u thdi ky tinh la 1 ngay thi vdi bffdc thdi gian 6 giay, trffdng hdp 1 can 712 giay; trffdng hdp 2 can 117 giay, giam khoang 83 % thdi gian tinh toan.
Ky thuat lffdi long khong chi tie't kiem bo nhd may tinh, thdi gian tinh toan ma each thffc tffdng tac chu dong (qua lai giffa lffdi min-thd) cua ky thuat nay con cai thien dffdc do chinh xac cua ket qua tinh toan. Hinh 6 va 9 tnnh bay
Tap chi Khi tvii^ng Thuy van * Thang 5/2008
37Nghidn cuTu & Trao doi
cac ke't qua tinh toan mffc nffdc cho trffdng hdp trffdng hdp khdng cd lffdi long la m2 = ± 29 cm cd lffdi long va khdng cd lffdi long so vdi thffc va m^ = ±23 cm cho trffdng hdp cd lffdi long, do. Sai so' trung binh so vdi thffc do trong
J ThLfC do Tinh toan_kh6n9 lu-oi longl
Hinh 9. Miic nUdc thUc do vd tinh todn tgi Trd Co trUdng hgp khdng co ludi long (td 05h ngdy 20/05/2000)
0 50 100 150 2QO 250 3QO 350: 400 450 500 550 600 650 700 750 TTioi giian (gio^
Hieu qua ciia lffdi long tie'p tuc dffdc khang chi tie't hdn d cac khu vffc ven dao trong lffdi dinh tren hinh 10 va 11. Nhan tha'y gia tri ciia min. Dieu dd chffng to md hinh da dam bao cac dffdng dang mffc nffdc tren lffdi min hoan dffdc sff bie'n ddi trdn, lien tuc cua cac qua trinh toan phii hdp vdi lffdi thd, cac vec td ddng chay thuy ddng life qua bien chung giffa lffdi min va ngoai sff phii hdp ve hffdng va do Idn cdn dffdc thd.
Fnm. loiim «»-»« •Mtir
T n w j I i j j v r T i 6*5 S o l j c ^-.irtTiQVfC^.fJi&f.-'t'i ~t -.,
a) Lffdi thd b) Lffdi min
Hinh 10. Ke't qud tinh todn trUdng dong chay vinh Bac Bd luc nUdc rut.
>i I Qt UvMbS vwtH-
Tif^j^^j'/tt t^y Be l<j; O ' l r»j^5*0i5/D&^XO 7 ^.^
I C i n l i d e i
a) Lffdi thd
ztz
r
/ :iiit
--.*^.i>
4CUirZ0>» I'MW
_ *«*E8
iiT- -if fk list n
1! R / J
8 *
Hinh 11. Ke't qud tinh todn trUdng dong chay vinh Bdc Bg luc nUdc ddng.
b) Lffdi min
38
Tap chi Khi tifc/ng Thuy van * Thang 5/2008
Nghien cvtu & Trao doi
4. Ket luan
Tac gia da xay dffng thanh cdng md hinh tinh toan ddng chay tdng hdp trung binh theo do sau cd sff dung ky thuat lffdi long. Sff lien ke't giffa cac mien lffdi thd - min dam bao tinh hen tuc, bie'n ddi trdn qua bien chung. Hieu qua lffdi long the hien rd thdng qua viec chi tie't hda khu vffc bien quan tam, tie't kiem bo nhd may tinh va thdi gian tinh toan. Md binh nay cd the sff dung trong tinh toan thuy trieu, ddng chay tdng hdp va tinh toan nffdc dang.
Khi tinh toan trffdng ddng chay cho vinh Bac Bo, eo Quynh Chau cd anh hffdng Idn. Can
md eo Quynh Chau de cd dffdc cac ke't qua tinh toan phu hdp vdi thffc te.
Thanh phan ma sat khdng the thie'u trong tinh toan ddng chay trong thiiy vffc ndng, dia hinh phffc tap. Dd'i vdi vinh Bac Bo he s o m a sat day phu hdp nam trong khoang 0,0014 - 0,0018.
Tdc do ddng trieu trung binh cho toan vinh khoang 0,3m/s. Hai khu vffc cd ddng chay manh la eo Quynh Chau va phia tay, tay nam dao Hai Nam (Idn nha't tffdng ffng khoang
l,3m/s va 0,8 m/s ).
Tai lieu tham khao
1. Ban Bien gidi - Bd Ngogi giao (2003), Tdi lieu tap huan quan ly bien trong vinh Bac Bd, 2003.
2. Phiing Ddng Hie'u (2006), "PhUdng phdp sai phdn dn cho bdi todn thuy trieu bien ven ", Tgp chi khoa hoc DHQGHN, (sd2B PT), tr. 39-49.
3. Nguyen Ngoc Thuy (1976), Thuy trieu vinh Bac Bd, Nhd xuat bdn Tong cue KM tugng Thuy vdn, Hd Ndi.
4. Z. Kowalik (1996), Numerical Modeling of Ocean dynamics, World Scientific.
5. Dinh Van Manh and Tetsuo Yanagi (1997), "A three - dimensional numerical model of tide and tidal current in the Gulf ofTongking", La mer 35, pp. 15-22.
