3. Ket qua kiem chijfng va ap dung mo hinh
3.2. Kiem chiing vdi trUdng hcTp song dai dijfng trong kenh thang
Do bai toan thuy trieu la mot bai toan md phong lan truyin sdng dai nen nha't
thi^t phai kilm nghiem mo hinh toan d6i vdi trUdng hdp sdng diing. Day la mot trong
nhiing bai toan kilm nghiem ddn gian nhUng lai ra't hOu hieu trong vi§c kilm tra tinh
44 Phitog Dang Hifu
kenh t h i n g c6 do sau khong doi, kin mot diu. Gia thiet phan xa hoan toan va khong co
tac dung ciia lUc eorioHs thi do ket hdp ciia song tdi va song phan xa, trudng sdng dxtng
se xua't hi§n trong kenh vdi cae diim nut va diim bung phan bo theo qui luat. Neu suy giam so CTia mo hinh so la nho thi tai cac diim bung ta phai thu dUdc cac dao dong c6 bien do it nha't la ga'p hai l i n bien do cua sdng tdi. Tai cac diim niit c6 cac dao dong nho. Neu tinh phi tuyen dUdc mo phong tot thi cac dao dong tai diem nut khong bi triet
tieu ma se xua't hien sdng thii ca'p c6 tin so ga'p hai lin tin so ciia song tdi.
Vdi bai toan kilm tra thii hai nay, kenh d i n dUdc chon c6 do dai 1 =1000 m, do
rong b=50m, do sau h =10m, sdng tdi co chu k^ T=30s, bien do A =20cm. Vung kenh
dUdc chia thanh cac lUdi hinh chii nhat 2,5m x 2,5m. Bien tai cuoi kenh dUdc chpn la
bien khong tha'm (phan xa toan phin). Thdi gian tich phan dUdc chon la 250s dii de
sdng truyen het hai l i n chieu dai kenh. Cac ket qua mo phong dao dong mUc nUdc tai
cac diim bung va diim nut (each nhau xen ke bang mot p h i n tu do dai song L == TyJ^
dUdc trinh bay tren cac hinh 3 va 4.
U.u ' 0 . 4 - 0 . 4 - e 0 . 2 - i3 0 - n 1 -o-z • -0.4 • - 0 . 6 - \ .< .Vx' -
Dao d^ng t^i bien |
Dao dOng t^i Ci^m byng'
•V rlhrfSrh/hrj^/-^-'' ••..(] ^•..>y^-^y>4j:-i^ ^-'' ••..(] ^•..>y^-^y>4j:-i^ 1 1 1 1 50 100 150 Tb6igEin(s) 200 250
Hinh 3. Dao d o n g mUc nUdc tai diem bung (diem ngay phia trudc tudng diing) va d a o dong song tdi
Hinh 3 trinh bay dao dong cua mUc nUdc tai diem bung ngay phia trUdc tUdng diing va dao dong ciia song tdi tai bien vao d i u kenh. Tren hinh ve ta tha'y, sau mot khoang thdi gian khoang 100 giay sdng truyen tdi tUdng va hien tUdng phan xa xua't hien. Dao dong tai diem sat tUdng c6 bien do ga'p hai l i n bien do sdng tdi va on dinh sau mot khoang thdi gian ra't ngan. Sau khoang 200 giay, sdng phan xa tii tUdng k^t hdp vdi sdng tdi tai bien va tao thanh mot sdng ket hdp, liic nay dao dong ciia s6ng tai bien khong con la dao dong ciia rieng song tdi nOa, ta c6 t h i tha'y ro sU bien do'i cua dUdng diit n6t tren hinh 3 ciia dao dong tai bien.
Phuong ph^p sai phfln in cho b&i toAn thuy tri^u bi^a ven 45 0.4 -0.2- -0.4 Daod^t^ibifin Dao dOng t^i di^m nut
-r- 50
— I —
100 150 200 250 TbMgian(s) TbMgian(s)
Hinh 4. Dao dong mUc nUdc tai diem nut (each tudng mot khoang SU 4) va dao dong tai bidn
Hinh 4 trinh bay dao dong ciia mUc nUdc tai diem each tUdng mot khoang 5/4 do dai sdng tdi L, tUdng ling vdi diem gin diem nut. Ta th^y sau khi sdng tdi di qua mot khoang thdi gian ngSn cd 130 giay thi sdng phan xa tii tUdng quay lai gap sdng tdi tai diim nay va tao thanh song ket hdp c6 dao dong nho hdn r^t nhieu dao dong ciia sdng tdi. Dac biet ta cd t h i quan sat th^y dao dong co t i n so cao tai diim nay do sU kl^t h<?p phi tuyen gifla sdng tdi va song phan xa chinh vi vay cac dao dong mUc nUdc v l n ton tai d diem niit.
Nhu vay mo hinh so co the mo phong tot trUdng hdp lan truyen song dai va mo phong dUdc cac tUdng tac giQa cac song vdi sU suy giam so khong dang kl. Ket qua nay cho phep ta tin tucfng vao mo hinh de c6 the ap dung cho cac bai toan truyen song dai tren thUc te.
3.3. Ap d u n g m o h i n h c h o b a i t o a n thiiy t r i e u
Mo hinh so da kiem nghiem d tren dUdc ap dung tinh toan thii cho truyen trieu trong biln Dong. Viing biln dUdc chia thanh cac lUdi hinh vuong vdi Ax = 175 do Ay = 175 do, cac true dUdc chon xa'p xi hUdng theo kinh tuyen va vi tuyen tren he toa do De Cac. Bien ciing dUdc xa'p xi vdi dieu kien thong lUdng bang khong. Cac bien long dUdc cho cac dao dong muc nUdc theo cac hang s^ diiu boa ciia 4 sdng chinh. C6 ba bien long dUdc sii dung cho mo hinh la eo Dai Loan, eo Basi va eo Malaea. Cac hang so dilu hoa tren cac eo biln nay dUde la'y theo bang thuy trilu Admiralty Tidal Tables [5). Cac toa do diim la'y hang so dilu hoa va cac bien dUdc trinh bay trong bang 1.
46 Phitog Dang Hitfo
Bing 1. Cac bien long va cac hing so dieu hoa
Ddi Loan Basi Malaea Vido 23*33' 2r58' ^''\v Kinh do 119^3' 120°45' 108*'59* M2 H(cm) 87 26 26 G" 326 188 125 S2 H(cm) 23 11 5 G' 15 214 199 K1 H(cni) 25 23 14 G- 278 262 66 01 H(cm) 21 18 16 G- 236 224 10
Hinh 5 trinh bay tnl6ng v4n toe dong trung binh tai luc 10 gid ng4y 1 thang 1 nam 2004.
Hinh 5. Ket qua mo ph&ng tn/dng van toe trung binh tren biln Dong luc 10 gid ngay 1/1/2004
Ke-t qua mo phong dao dong m^c nUdc tai Hon Dau dUdc so sanh vdi so heu thUc do tai tram Hon Dau trong thang 1 n i m 1988. Hinh 6 trinh bay dao dong mUc n u ^ trilu tai khu vuc Hon Dau trong thang 1 n i m 1988. Tren hinh ve ta th^y dao dpng mUc
nuac tinh toan kha p h . h ^ v6i so^heu thuc do. Dao ^^^ ^^.^^'^^^J^^ ^ ' ^ ^
nhat tri lu d i u va xu the^ thay do'i cua dao dong mUc nU6c trnh toan r&t phU hop ven thu J ' T r e n M n ^ vg so sanh ta cOng tha'y c6 sU sai khac nho v l bi.n d tneu g^Ua mo rh6ng so-va so^Ueu thUc do, nguyen nhan co t h i giai thich do v, t n lay ket qua m
Phuong phiip sai phan Ai cho bai toto thuy tri^u bidn ven 47
phong con kha tho nen chUa mo ta dUdc het nhiJng anh hudng phi tuy^n cua viing nUdc nong va sU thay doi dia hinh phtic tap len dao dong mUc nUdc trieu.
3 2 4 2 4 2 -1 I -2 •T£nh to6n Thuc do • 50 100 150 200 250 Thdi ^an (gijy)
300 350 400
Hinh 6. Dao dong mUc nUdc tai khu vi/c Hdn Dau (b^t diu tCrO gid ng^y 01/1/1988)
Mo hinh cung dUdc tinh toan thuy trieu thii cho v t o g vinh Ha Long. Gidi han vtog vinh dUdc chon la toan bo vung vinh Ha Long va Bai T i Long. Vung ap dung tfnh toan thtt nghiem dUdc chia thanh eac 6 lUdi vuong vdi bUdc lUdi 250m. Cac bien long
dUdc sii dung la eac dao dong mUc nUdc trich ra tii mo hinh Idn tinh cho viing vinh Bac
Bo vdi ludi la 1/30 do. Tai cac diem bien tren mien tinh nho khong triing vdi dilra lUdi Idn c6 so* lieu trich ra thi dUdc npi suy tuyen tinh theo cac so Heu tren cac diem ciia lUdi 16n. Tren hinh 7, 8 trinh bay ddng chay tai hai thdi diem nUdc xuong va nUdc len trong vung vinh Ha Long.
(Delta X-250 m)
Phiing Dang Hi^u
imJk
X (DeKaz-250m)
Hinh 8. TrUdng van toe ddng chSy vung vjnh Ha Long luc pha trieu len
Tren cac hinh 7 va 8 ta tha'y toe do dong chay trieu tai eac khe hep giiJa cac dao va tai nhiing vung nUdc nong la kha Idn. K^t qua nhin chung kha phu hdp vdi qui luat cua dong chay do tac dong ciia thuy trieu. Do nguon so' Ueu thUc do ve dong chay tai cac eo khe dao d tai viing Ha Long khong c6 nen viec so sanh giiia ket qua mo phong va so lieu thUc te chUa thUc hien dUdc. Tuy nhien ket qua bude d^u cho tha'y phUdng phap sai phin ^n trinh bay 5 bai bao nay la ra't hieu qua va de dang ap dung. Dieu nay chiing to mtic do on dinh ciing nhU kha nang ap dung vao thUe te ciia phUdng phap sai phan trinh bay cl tren.
4. Ket l u a n
•
PhUdng phap sai phan in trinh bay 6 tren ra't ddn gian, de sii dung va co do chinh
xac ciing nhu do on dinh kha tin cay. Ket qua sii dung phUdng phap nay cho mot so bai toan 1^ thuyet ciing nhu thUc te trinh bay d tren da chiing to kha nang ting dung thuc
te ciia mo hinh toan phat triln trong nghien ciiu nay la ra't hien thUc. Tuy nhien de di
den hoan thiSn thanh ph^n mim iing dung mo hinh toan c i n dUdc kiem chiing them niia vdi cac so heu thUc te.
Ldi cam an
Noi dung bai bao trinh bay cl day la mot phfin cua de tai nghien ciiu khoa hoc ca'p Dai hoc Quoc gia do tac gia chii tri. Nhan day tac gia giii ldi cam dn tdi phong khoa hoc trudng Dai hoc KHTN va Dai hoc Quoc gia Ha Noi da trd giiip kinh phi va tao dieu kien cho tac gia thUc hien de tai ma so QT-06-34.
phuong phip sai phan fc cho Mi todn thuy tri^u bi^n ven .q
TAI L I E U T H A M KHAO
[1]. Pham v a n Ninh va nnk, Bien Dong Tap 11: Khi tuang thuy van dong lUc bien, ChUdng
trinh dieu tra nghien ctiu bien c^p nha nu6c KHCN-06 (1996-2000), NXB Dai hoc Quoc gia Ha N6i, Ha N o i , 2003, 565 tr.
[2]. Nguyin Thi Viet Lien, M6 hinh so tri bai toan thuy trieu bien Dong, LuAn an Ph6 tien si
khoa hoc, Vien Cd hoc, 1997.
[3]. Yabe T., T. Aoki., A universal solver for hyperbolic equations by cubic-polynomial
interpolation, Comp, Phys. Communications, Vol. 66, Elsevier, 1991, p. 219-232.
[4]. Hieu P. D., K Tanimoto, C. T. Vu., Numerical simulation of breaking waves using a
two-phase flow model. Int. J. Applied Math. Modeling, Elsevier, Vol. 28, No.ll(2004)
p.983-1005.
[5]. Admiraty Tidal Tables, Pacific Ocean And Adjacent Seas, Vol. 3, 1971.
VNU. JOURNAL OF SCIENCE. Nat, Sci., & Tech., T.XXII. No2B AP. 2006