Xây dựng mô hình mô phỏng dòng chảy và truyền chất hai chiều, ứng dụng cho vùng vịnh Hạ Long

He phuong trinh nude nong phi tuyen hai chi6u da dugc nhi^u tac giai sir dung de md phdng bai toan ddng chay hai chi^u trung binh theo dp sau nhu bai toan thuy trieu, bai toan ddng chay

DAI HOC QUOC GIA HA NQI Trudng Dai hoc Khoa hoc Tir nhien

XkY DUNG MO HINH MO PHONG DONG CHAY VA TRUYEN

CHAT HAI CHKU, VTNG DUNG CHO YUNG VINH HA LONG

BAO CAO TOM TAT D £ T A I

1 Ten de tai: Xay dung m6 hinh mo phdng ddng chay va truydn chat hai chieu,

Ihig dung cho viing vinh Ha Long

2 Ma sd: QT.06.34

3 Chu tri de tai: TS Phiing Dang Hieu

4 Cac can bo tham gia:

1) ThS Pham Hoang Lam

a) xay dung mo hinh so mo phong ddng chay va truydn chat hai chieu

- Nghien cihi thuat toan thich hop sai phan giai he phuong trinh nude nong hai chi6u Lap chuong trinh may tinh

- Nghien cuu thuat toan thich hop sai phan giai he phuong trinh truyen chat Lap chuong trinh may tinh

- Tinh toan va kiem nghiem mo hinh so theo cac di6u kien ly thuyet va thuc te b) Ung dung mo hinh tinh toan thir nghiem cho viing vinh Ha Long

- Thu thap va so hoa trudng dp sau viing vinh Ha Long; thu thap cac sd lieu v6 thuy trieu va gid viing bien ven bd Quang Ninh

- ung dung mo hinh tinh toan thir nghiem cho viing vinh Ha Long theo cac kich ban

- Phan tich ket qua, danh gia mo hinh va viet bao cao long ket, nop san pham, nghiem thu

6 Cac ket qua dat dugc:

1) Da utig dung phuong phap CIP (Constraint Interpolation Profile) hien dai cd dp chinh xac bac ba va phat trie'n mot phuong phap sai phan an vao viec sai phan hoa giai

11

h6 phuong trinh nude ndng phi tuy^n cho bai toan ddng chay Viet thanh cong chuong trinh may tinh m6 phdng ddng chay sinh ra do gid va do thuy trilu Tinh toan thu nghidm va ki^m chung md hinh cho cac dieu kien ly thuyet cd nghiem giai tich va kilm chiing trong trudng hop dieu kien thuc te ciia bai toan truydn trieu Bien Dong K^t qua cho tha^y phuong phap CIP sir dung d day cho bai toan mo phdng ddng chay la r^t hop ly va cd d6 chinh xac kha cao Mo hinh chiing to kha nang ung dung tot cho cac viing bi^n nong ven bd

2) Da xay dung thanh cong chuong trinh truyin tai va khuech tan vat cha't su dung phuong phap th^ tich huu han vdi so do TVD (Total Variation Diminishing) cd

dp chinh xac bac hai Viet thanh cong chuong trinh may tinh va kiem chung mo hinh cho cac bai toan ly thuyet cd nghiem giai tich Ket qua cho thay phuong phap TVD siJ dung d day cd dp chinh xac cao hon nhieu so vdi mot sd phuong phap sai phan truyen thdng hay dugc sir dung nhu UPWIND bac mot hay Lax-Wendrof Mo hinh cho phep

md phdng qua trinh truydn tai khuech tan vat cha't dudi tac dpng cua ddng chay trung binh

3) Da thu thap va sd hoa dia hinh viing vinh Ha Long tren ludi vuong gdc trong

toa dp D6 Cac vdi budc ludi 250 m x 250 m Thu thap va phan tich nhung sd lieu v6

tdc dp gid va hudng gid viing ven bd Quang Ninh, sd lieu thiiy tridu LSig dung mo hinh m6 phdng he thdng ddng chay gay ra do gid trung binh mija Dong va miia He va

do tac dpng ciaa thuy trieu trong cac chu ky trilu len va xudng Idn Mo phdng Ian truyen vat cha't dugc thuc hien tren n6n ddng chay long hop ca gid va thuy tri^u vdi gia thiet chat chi thi bin vung khong phan huy va cd sir cd mo trudng thai ra tai mot sd di^m gia dinh Cac ket qua cho ra cac bu'c tranh phan bd trudng ddng chay va phan bd nong dp cha't 6 nhilm khi cd tac dpng ciia cac yeu td dpng lire la gid va thuy trieu

4) Ndi chung md hinh xay dung trong di tai da dap ihig dugc yeu cau v6 mo

phdng ddng chay va truyen chat vdi dp chinh xac dang tin cay va cd kha nang urng dung de nghien cihi cho cac viing bien ven bd khac Ket qua ung dung tinh toan cho viing vinh Ha Long, Quang Ninh cho thay ro kha nang ung dung ciia md hinh da phat trien

5) Dang dugc mot bai bao tren tap chi khoa hpc Dai hoc Qudc Gia

7 Tinh hinh kinh phi cua de tai

Tdng kinh phi dugc cap: 20.000.000 ddng

Da nhan: 20.000.000 ddng

Da thanh toan: 20.000.000 dong

111

XAC NHAN

CUA BAN CHU NHlfiM KHOA CHU TRI D £ TAX

(^>^>t^-^^

XAC NHAN CUA TRU^ONG

OHO HIEU TRUONU

GS.TS.^^rfin/ ^ / ^ / ^

IV

ABSTRACT

1 Project title: Development of a numerical 2-D model based on the shallow

water equation and convection-diffusion equation for the application to the Halong Bay

2 Code number: QT.06.34

3 Project Leader: Dr Phung Dang Hieu

4- Members: 1) M Sc Pham Hoang Lam

2) B.Sc Tran Due Tru

5 Aims and contents of project:

a) Development of a numerical 2-D model

- Development and application of a finite difference scheme for solving the shallow water equation Development of a computer program

- Development and application of a finite volume TVD scheme for solving the conveetion-diffution equation Development of a computer program

- Verification of the numerical model with some analytical and practical conditions

b) Application of the model to the study of tide-induced currents and induced currents, the transportation of tracer in the Halong Bay

wind Collection and digitization of the bathymetry of Halong Bay; Collection of wind and tidal data in the near-shore area of Quang Ninh

- Application of the model to the simulation of tide-induced, wind-induced currents in the Halong Bay Simulation of the propagation and distribution of pollution (tracer) based on some scenarios

- Analysing and assessing the simulated results in order to give conclusions and writing the final report

problems Computed results show that the application of CIP method for the simulation

of shallow water currents is fairly accurate The numerical model can be applied to the near-shore shalow seas

2) A numerical model based on the convection-diffusion equation using the TVD (Total Variation Diminishing) scheme has been successfully developed A computer program has developed Some numerical tests with analytical conditions show that the TVD method used here is more accurate than the conventional methods such as Upwind first order or Lax-Wendrof The numerical model is capable of simulation of the advection and diffusion processes of suspended materials under the driven action of the depth averaged currents

3) Collection and digitization of the bathymetry in the Halong have been done for

an orthogonal mesh with the same mesh size in x and y direction 250 m The wind and

tidal data in the near shore area of Quang Ninh also were collected Then, the numerical model was applied to the simulation of wind induced currents resulted by the averaged wind in the sommer and winter; and by the tide Simulation of propagation and distribution of suspended materials initiated at some locations under the depth averaged currents induced separately by wind and tide, and by both wind and tide was also carried out Simulated resuhs showed resonable pictures of the water current and pollution concentration distribution

4) In general, the numerical model developed in this study meets the requirement

on the simulation of depth averaged currents and pollution propogation with an acceptable accuracy and the model can be applied to other areas of shallow sea

5) Results of the study were published as an article on the Journal of Science, VNU

VI

MUC LUC

Mdd^u 2 Chuong 1 Md hinh md phdng ddng chay hai chilu 4

1.1 H6 phuong trinh ca ban va cac di6u kien bien 4

1.2 Phuong phap sai phan theo so dd CIP cho he phuong trinh nude nong 5

1.3 Kiem chung md hinh sd'theo cac bai toan ly thuyet va thuc te 10

1.4 Nhan xet 16

Chuong 2 Mo hinh mo phdng truydn chat hai chi6u 17

2.1 He phuong trinh coban vacac didu kien bien 17

2.2 He phuong trinh dudi dang rdi rac sir dung phuong phap TVD 17

2.3 Kiem chung mo hinh sd theo cac bai toan ly thuyet 18

Chuong 3: Ung dung md hinh cho vung vinh Ha Long 26

3.1 Gidi thieu viing nghien cuxi 26

3.2 Sdlieu sijrdung trong nghien cuu 35

3.3 Ket qua mo phdng 35

Ket luan va kien nghi 51

Tai lieu tham khao 53

Phuluc 54 Tom tat cac cong trinh NCKH cua ca nhan (Miu 1) 55

Scientific Project (Mlu 2) 56

Phieu dang ky ket qua nghien cuu KH-CN 57

MODAU

O nhidm moi trudng bien hien dang la va'n dl dugc quan tarn ciia hSu het cac qudc gia cd bien tren the gidi Vdi nhu c^u phat trien kinh te hudng vao tiem nang ciia bi^n da ngay cang gia tang ap lire v6 6 nhilm moi trudng bien ndi chung va d nhilm mdi trudng vung ven bien ndi rieng Chinh vi le dd, viec phat trien kinh te ciia mdt viing ludn dugc ddi hoi dat trong bdi canh phat tri^n ben vung Trong dd viec danh gia tac ddng ciia boat dpng kinh te dan sinh d6'n thay doi moi trudng ddi hoi phai dugc thuc hidn mdt each nghiem tiic de cd nhirng chien luge phat trien cung nhu qui hoach phat trien dudi sir quan ly tdng th^ sao cho vira dap ung dugc nhu cau phat trien tat yeu cua kinh te xa hoi, vira dam bao giam thieu dugc tac hai cho moi trudng tir nhien vd'n

cd

Hiu het cac qudc gia phat trien va dang phat trien cd bien (nhu: My, Nhat ban, Anh, Ha Ian, Mexico, Trung Qudc, v.v.) d6u da va dang thuc hien cac dir an khao sat, danh gia va du bao bien dpng moi trudng nham dua ra cac canh bao, cac thong tin trp giiip cho he thdng ra chinh sach, phue vu cho qui hoach phat trien kinh te cua cac viing bi^n va ven bien quan trong (Peterlin va nnk, 2005 [10]; Lozano va nnk, 2005 [7]; Lau,

2005 [8]) Trong dd viec md phdng va danh gia muc dp Ian truyen chat d nhi6m trong mot viing nude cu the la mot trong nhung mat xich quan trpng trong cac chuong trinh quan ly tich hgp phuc vu cho viec xir dung hop ly tai nguyen va phat trien ben vimg d h^u het cac qudc gia tren the gidi trong dd c6 Viet Nam

Cac cong cu md phdng thuy dpng lire va Ian truydn vat cha't noi chung va cac chat

d nhilm ndi rieng (COD, BOD, TSS, ) da va dang dupe rat nhieu trung tam nghien cull cd uy tin tren the gidi phat trien va cho ra cac san phfa thuong mai cd gia tri cao dap ung dugc cac nhu cau ung dung trong quan ly va sir dung hgp ly ngudn nude cung nhu trg giiip cho qui hoach phat trien kinh te Cac san pham cong cu phan mem dai dien nhu SMS (ciia My), MINLAKE (cua My), MIKE 21 (cua Dan mach) Dd la nhung cong cu hiru ich de ting dung tren thuc te

0 nude ta cac chuyen gia ve mo hinh hoa va md phong loan hpc tren may tinh cac qua trinh thuy dpng lire hpc va Ian truyen cac cha't d nhidm da va dang dan tiep can dugc nhimg thanh tuu khoa hpc hien dai tien tien tren the gidi He phuong trinh nude nong phi tuyen hai chi6u da dugc nhi^u tac giai sir dung de md phdng bai toan ddng chay hai chi^u trung binh theo dp sau nhu bai toan thuy trieu, bai toan ddng chay do gio Tuy nhien cac tac gia chu yeu don gian hoa he phuong trinh thanh dang tuyen tinh hoa nhu Nguyln Ngpc Thuy (1969), Dang Cong Minh (1975) [1, 2] hoac giai phuong trinh nude nong d^y dii nhung vdi cac so dd toan don gian nhu UPWIND bac 1 hoac sai phan trung tam cd dp chinh xac khong cao Ddi vdi bai toan truyen tai vat chat thi

va'n dt con khd hon la vdi cac so dd toan don gian thi viec ton tai cac nghiem sd khong

that (thi du nghiem am, hoac nhiiu sd) la va'n de thudng gap Do vay viec phat trien

mdt md hinh md phdng ddng chay va chuydn cha't hai chi6u dang tin cay cho viing ven

bd la v^n di cin thiet phuc vu cho nghien cuu ciing nhu qui hoach moi trudng trong

cac viing nude ven bd

Muc tieu ciia dd tai la phat trien va ung dung thanh cong cac so dd sd tien tien cd

dd chinh xac cao vao xay dung mo hinh sd md phdng dugc ddng chay va truyen chat hai chi^u trong viing ven bd dudi tac dpng ciia gid va thuy tridu Sau dd ung dung tinh toan thii nghiem cho viing vinh Ha Long

Ngoai phSn md ddu, ket luan va kien nghi, tai li6u tham khao, npi dung bao cao cua d^ tai dugc trinh bay trong ba chuong:

Chuong 1 : Md hinh ddng chay hai chidu Trong chuong nay trinh bay co sd ly thuyet, he phuong trinh xua^t phat, cac dieu kien bien ciia md hinh md phdng ddng chay hai chi6u cd tinh den anh hudng ciia gid Trinh bay tdm luge phuong phap sai phan cd

dd chinh xac cao CIP (Constrained Interpolation Profile); phuong phap sai phan an dang SMAC va each ung dung rdi rac hoa giai he phuong trinh nude nong phi tuyen Cac bai toan kiem nghiem md hinh dudi dang ly thuyet va thuc tiln cung dupe trinh bay nham khang dinh tinh on dinh, dung dan cua md hinh so

Chuong 2 : Md hinh truyin cha't hai chidu Trong chuong nay trinh bay he phuong trinh md ta qua trinh truyen tai va khuech tan vat chat hai chieu dudi tac dpng cua ddng chay nen Md ta cac dilu kien bien Trinh bay phuong phap sai phan dang TVD cd dp chinh xac bac hai va ling dung rdi rac hoa giai he phuong trinh xuat phat

Md hinh sd dugc kiem chung thdng qua cac bai toan co ban cd nghiem giai tich nham kiem nghiem kha nang mo phdng qua trinh truydn tai vat chat ciia md hinh

Chuong 3: Ung dung md hinh cho viing vinh Ha Long Chuong nay trinh bay tom lupe viing nghien cun, di6u kien gid, thuy treu, dia hinh Lira chpn cac sd lieu dau vao

de md phdng Cac ket qua mo phdng Ian truyen vat chat gia dinh khong bi phan huy theo thdi gian theo cac kich ban dudi tac dpng ciia gid va thuy trieu Cac nhan xet v6 ket qua nghien cun

De tai nay dupe hoan thanh vdi sir hd trp kinh phi tir phia Dai hpc Qudc gia (DHQG) Ha Ndi, sir giiip do ciia Ban Khoa hpc & Cong nghe, DHQG, Phong Khoa hpc Cdng nghe, trudng Dai hpc Khoa hpc Tir nhien, sir ung ho nhiet tinh ciia Hoi ddng Khoa hpc Trai da't, DHQG HN, ciia Ban chu nhiem khoa Khi tugng Thuy van va Hai duong hpc, cung nhu su ddng gop y kien eiia cac nha khoa hpc, cac ddng nghiep tham

gia di tai va tap the can bd cua Bp mdn Hai duong hpc Nhan day chiing tdi xin chan

thanh cam on nhimg giiip do qui bau dd

CHUONG 1:

MO HINH MO PHONG DONG CHAY HAI CHltv

LI H £ PHUONG TRINH CO BAN VA CAC Difiu KI$N BifiN

He phuong trinh xuat phat diroc sir dung trong phat trien md hinh la he phuong

trinh nude ndng phi tuyen, bao gom :

Phuong trinh bao toan dpng lugng

w,v: cac thanh phan van tdc trung binh dp sau theo cac hudng ox va oy\ f: tham sd

Coriolis; (^ : dao dpng muc nude; p : mat dp nude; h : dp sau nude; u^: he sd nhdt rdi

T^Ty la cac thanh phan ung suat gio tren mat theo true x va true y, chung dupe xac

dinh theo cdng thuc sau:

T: =P^C,^\W\W/, T].=P^C\W\W^,^ (1.6) trong dd p^ la mat dp khong khi; w la vector van tdc gid He sd C, dugc xac dinh

theo Smith & Banke (1975) nhu sau :

H6 phuong trinh tren cho phep md phdng ddng chay cd chu ky dai trong viing

nude ndng bao gom ca ddng chay phat sinh do thiiy triSu va do gid

Cac diiu kien bien dugc sir dung trong md hinh nhu sau:

Bi6n cung: sir dung dieu kien khong tha'm, ture la thanh phan van tdc theo phuong

phap tuyen vdi mat bi6n bi triet tieu

Bidn long: dieu kien bien phat xa tir do cho sdng dai dugc sir dung Khi dd gia tri

van tdc thang gdc vdi bien dugc xac dinh theo cdng thirc

a - ^ (1.8)

Bi6n Idng cho dao done thuy trieu: dao dpng muc nude dugc tinh theo cac hang

sd dieu hoa cho tren bien

1.2 PHUONG PHAP SAI PHAN THEO SO DO CIP CHO H £ PHUONG TRINH

NU6C NONG

Va'n d6 kha quan trpng trong viec giai sd he phuong trinh nude ndng phi tuyen la

xa'p xi dugc tot thanh phan binh luu phi tuyen Thuc te giai sd cho thay neu xap xi cac

thanh ph^n phi tuyen nay bang cac so do sai phan trung tam cd dp chinh xac bac hai thi

thudng dan den cac nhilu gia trong ket qua gia sd trong trudng hgp tdn tai cac gradient

Idn ciia muc nude hay ddng chay De khac phuc va'n d^ nay mot trong nhung phep sai

phan thudng dupe sir dung do la phuong phap upwind bac mot hay so dd Quick bac ba

ket hop vdi so do nhdt nhan tao

Gan day mot sd phuong phap sai phan mdi ket hgp giira hai phuong phap

Lagrangian va Euler cd dp chinh xac cao da dupe nhdm tac gia Yabe va Aoki (1991)

[11] cong bd cd ten la CIP (Constrained Interpolation Profile) Phuong phap nay da

dugc chiing minh la co dp chinh xac bac ba va xap xi rat tot cho cac thanh phan truyen

tai phi tuyen Thi du ve mot sd nghien cun sir dung phuong phap CIP da xuat ban nhu

nghien cihi tuong tac sdng va cong trinh ngam (Hieu va Tanimoto, 2006) [9] hay

nghien ciin thuy trieu Quang Ninh (Hieu, 2006) [3] Trong nghien cun nay, phuong

phap CIP dugc sir dung de xap xi thanh phan binh luu phi tuyen trong phuong trinh

chuyen dpng cua he phuong trinh nude nong

Dudi day trinh bay tdm tat tu tudng va npi dung ciia phuong phap CIP (chi tiet

xem Yabe va Aoki, 1991) [11]

1.2.1 Tdm tdt phuong phap CIP

Tren thuc te hau het cae qua trinh vat ly thudng diln ra trong mdi trudng lien tue

nhung giai sd cac qua trinh dd ta phai thuc hien rdi rac hda mi6n tinh toan Muc tieu co

ban CLia thuat giai sd la khdi phuc nhung thong tin bi mat (hay bi bd qua) giira cac

diem rdi rac dd Da sd cac so do sd trudc day d6u khong quan tam den nghiem thuc

phan bd ben trong 6 ludi va do dd mii'c dp chi tiet quan tam la d miJc kich thudc ludi

chia (Ax,Ay) Phuong phap CIP do Yabe va Aoki (1991) [11] trinh bay da cd gang di

xay dung phan bd nghidm trong d ludi sao cho g^n dung nhat vdi phan bd nghiem thuc

cua phuong trinh md ta vdi mot sd phep ap dat cu the De di6n ta phuong phap CIP ta

xet mdt phuong trinh truydn tai dang sau :

va raft khd tudng tugng ra dung profile nghiem, khi dd mot each rat tu nhien ta cd the tudng tugng ra dang profile ciia nghifm nhu dudng lien net tren hinh Lie Nhu the khuech tan sd cd the phat sinh khi ta xay dung dang profile cua nghiem bang phep ndi suy tuyen tinh mac dii ta da dua tren cac nghiem diing tai cac diem ludi (hinh Lie) Qua trinh ndi suy nay dugc thuc hien trong so dd Upwind (ngugc ddng) bac 1 Mat khac neu ta xap xi npi suy bang ham bac hai thi se gap phai ket qua la cac gia tri ndi suy vugt qua gia tri that, qua trinh npi suy nay dupe thuc hien trong cac so dd Lax- Wendroff hay trong so do Leith

uAt

gradient

Hinh 1.1: Nguyen ly cua phucmg phap CIP (a) duong li^n net la duong ban dau, duong dut net

la nghiem dung sau budc thcfi gian At; (b) nghiem tai tung die'm rdi rac; (c) khi noi suy tuyen tinh,

xuat hifin khuech tan so; (d) so do CIP: dao ham khong gian cung di chuydn va profile ciia nghiem

trong o ludi dugc khoi phuc

Dieu gi da lam nghiem kem chinh xac di? Dd la do ta da bd qua co che phan bd nghiem phia trong d ludi va ta da di theo cac nghiem tron Do dd ta thay phuong phap dua dang phan bd nghiem thuc vao trong 6 ludi la rat quan trpng Phuong phap CIP da dua ra each xap xi phan bd nghiem thuc trong 6 ludi nhu sau :

Trudc h6't l£y dao ham phuong trinh (1.9) theo bien x ta thu dugc :

^ + 3 = - ^ ^ (1.10)

dt dx dx

Trong dd g = df Idx la dao ham khong gian ciia / Trong trudng hgp don gian

nh^t u = const thi phuong trinh (1.10) gidng nhu (1.9) la md ta chuye'n ddng cua dao

ham khdng gian theo van tdc u Bang each siir dung phuong trinh nay ta cd the duoi

theo cac tien trien thdi gian cua / va g dua tren phuong trinh co sd (1.9) Neu g tinh

dupe va di chuyen nhu trinh bay bang mui ten tren hinh L i d , thi ta de dang sir dung

cac dao ham g nay de hinh dung ra phan bd nghiem va dudng profile se gan dung vdi

dudng ban d^u (nghiem diing) hon rat nhidu

Neu ca hai gia tri ciia / va g dupe cho trudc tai hai diem ludi thi dang profile

cua nghiem cd the dupe npi suy bang mdt da thuc bac ba (Nakamura va nnk, 2001):

^ =^,up-X,

iup = /-sgn(w,)

X = x-x,

sgn(w) la ham lay da'u ciia w x la tpa dp phia ngupc ddng cua diem xet sau budc

thdi gian A/ Nhu vay profile tai budc thdi gian (« + l) d^ dang thu dugc bang each

dich chuyen profile di mot doan w^A/ (tuong tu nhu phuong phap Lagrangian) vi the

/"*' =F"{x, -u,At) va g;^' =dF"{x, - w , A / ) / ^ Do dd ta cd :

fr'=ci,^!^b,^'+g:^,+f: ( L I 4 )

gr'=3a,^,^+2Z),^,+g; (1.15)

Trong dd <f, =-u^At

Nhu the phuong phap CIP sir dung phap tinh tien Lagrangian tren ndn ludi Euler

va do dd nd thupc vao dang phuong phap Semi-Lagrangian Thirc te tinh toan sir dung

phuong phap CIP da cho thay vdi phuong phap CIP hien cd the sir dung vdi sd Courant

- Friedrichs - Lewy (CFL) kha Idn ma so d6 van rat on dinh

1.2.1 Ung dung phuong phap CIP cho he phuong trinh nude ndng

Vdi he phuong trinh nude ndng ta co the bieu di6n tong quat dudi dang nhu sau:

7

^^u^^^^^G (1.16)

dt dx dy

trong dd G bao gdm cac sd hang cdn lai ciia phuong trinh chuyen ddng (gradient muc

nude, ung su^ft gid, ung sua't day, lire Coriolis, lire nhdt)

Sir dung thuat toan tach ta tim nghiem ciia phuong trinh (1.16) theo hai budc

(Yabe va Aoki, 1991):

Budc A: Pha truyen tai (Advection phase)

df df df ^ , -^ + u^^ + v^^ = 0 (1.17)

dt dx dy

Budc B: Pha khdng truy6n tai (Non-Advection phase)

^ = G (1.18)

dt

Sau khi budc A dupe giai cho pha truyen tai thi budc B dugc tinh toan cho pha

khong truydn tai dua tren cac gia tri vira tinh tir budc A Trong budc A ta sir dung

nghidm giai tich dja phuong ciia phuong trinh (1.17) dudi dang Lagrangian:

f{x,,y,J + At) = f{x^,^y^„J) (1.19)

vdi x^„ =x, + ^ , y^„ =y, +;;, ^ = -w,A/, rj = -v,At

Nhu the phuong trinh (1.19) cd the thu dupe bieu thurc hien theo cdng thure (1.14)

va bang each diing so do CIP nay luan chuyen cho timg hudng ox va oy cho bai toan

hai chidu

Sau khi tim dugc f"*^' = f{x,,y ,t+ At) a budc 1 thi gia tri ciia / tai budc thdi

gian n +1 that bao ham ca cac ddng gdp ciia cac yeu td khdng thupc pha truyen tai se

dugc giai theo phuong trinh (1.18) la:

/ r ' =fr'' +GAt (1.20)

Ddi vdi ham gradient g ciia / (tii'c la — = g^,— = g ) cung duoc thuc hien

dx dy

tuong tu nhu ham / nhung sir dung cong thuc CIP phuong trinh (1.15)

Trong nghien cuu nay de tang tinh on dinh eiia bai toan trong budc giai phuong

trinh (1.19) va phuong trinh lien tuc da sir dung phep sai phan an nhu sau:

Trudc het ta lira chpn vi tri cac bien dat tren he ludi so le: cac bien w, v dugc dat

tai cae canh ciia d ludi chu* nhat con bien ^ dupe xac dinh tai tam ciia d ludi (nhu so dd

Akagawa-C) Phuong trinh (1.1) va (1.2) dugc viet lai dudi dang don gian nhu sau:

^ = -F(u,v,h, )-g^ (1.21)

dt dx

n trudng van tdc du doan cho budc thdi gian tiep theo dupe xac dinh hien thdng qua

cac phuong trinh ddng lupng gpi la budc 1

Chi sd dau sao d tren cho biet trudng van tdc du doan ban dau (predicted velocity)

d budc thdi gian « +1 Trudng van tdc du doan nay sai lech so vdi trudng van tdc thuc

do cd sir thay ddi ciia dao dpng muc nude A^ d thdi diem mdi, do dd van tdc d thdi

di^m n +1 dupe xac dinh tir trudng van tdc du doan ban di\x\

(1.25), (1.26) vdi dai lugng {hA-Q va lay dao ham tuong ung theo x va theo y roi cdng lai ta thu dugc phuong trinh Poisson cho gia sd At^ nhu sau:

Neu la'y xap xi sai phan cho dao ham thdi gian eiia ^ va sir dung phuong trinh

(1.27) ta thu dugc phuong trinh sau:

^n la dp tang muc nude AC ta thu dugc mot he phuong trinh dai sd tuyen tinh vdi ma tran ddi xiing cd he sd tren dudng cheo chinh xac dinh duong He phuong trinh dai sd tuyen tinh nay cd the giai lap bang phuong phap SOR hay CG rat hieu qua Trong

nghiSn cun nay da sir dung phuong phap BiCGSTAB (Bi-Conjugate Gradient ciia van derVort(1992)

Vdi phep sai phan nhu tren, ta cd the tdm luge qui trinh tim nghiem nhu sau: Budc 1: tinh toan trudng van tdc du doan ban dau sir dung phuong trinh (8) va (9) Trong dd cac thanh ph^n binh luu phi tuyen, nhdt, coriolis va ma sat dupe xac dinh theo cac so dd tuy chon, d day da sir dung phuong phap xap xi CIP cua Yabe va Aoki (1991) [3]

Budc 2: giai he phuong trinh dai sd tuyen tinh cho A^ tir phuong trinh (1.29) vdi cac gia tri H va w'"^"', v*"^"* da biet tir budc 1

Budc 3: cac gia tri w"*', v"^' va 4'"*' d budc thdi gian can tim dupe xac dinh tir phuong trinh (1.25), (1.26) va (1.27)

Budc 4: gan cac gia tri budc thdi gian n +1 cho budc n rdi tiep tuc qui trinh cho

cac budc thdi gian tiep theo

1.3 KI^M C H U N G M 6 HINH SO THEO B A I TOAN L V THUYET VA THlTC TE Tr6n thuc te tinh toan nhi6u khi gap nhung trudng hgp tdn tai cac gradient muc nude Idn, thi du nhu cac front nude tran len cac viing dat thap (nude dang d cac bai tri^u, sdng nude dang do bao v.v.), do dd viec kiem tra xem kha nang mo phdng cua

mo hinh toan mo ta d tren cd sir dung phuong phap CIP ddi vdi cac trudng hpp cd gradient Idn ciia muc nude la rat can thiet De thuc hien dieu nay bai toan sdng vo dap dupe sir dung lam dieu kien kiem tra thu* nhat

Muc tieu ciia md hinh la mo phong ddng chay trong viing ven bd do dd viec kiem

tra kha nang md phdng sdng dai ciia mo hinh cung la van di dugc dat ra Yeu cau quan

trpng ciia md hinh sd la phai md ta dupe tuong tac phi tuyen ciia sdng dai va hon nira phai bao toan nang lupng ciia cac sdng dai nay d miic dp chap nhan dupe De thuc hien kiem nghiem cho muc tieu dat ra thi bai toan sdng truyen trong kenh thing kin mot d£u, trong kenh gia thiet khdng co ma sat, khong cd lire coriolis, sdng dung hoan toan dugc gia thiet va sir dung lam bai toan kiem tra thii hai

Bai toan thu: ba diing de kiem nghiem kha nang md phdng thiiy trieu vdi dieu kien thuc te ciia Bien Ddng Tinh toan dugc thuc hien cho truyen trieu tren Bien Dong va ket qua dugc so sanh vdi sd lieu muc nude thuc do d mot sd tram hai van ven bien 1.3.1 Kiem chung vdi bai toan vd dap

Trudc tien, md hinh sd dupe kiem nghiem qua viec mo phdng sd bai toan vo dap Day la mot trong nhung bai toan kinh dien diing de kiem tra cac mo hinh sd rat hun hieu Bai toan dupe gia thiet la co hai viing nude d thdi diem ban dau cd dp cao cot

nude la /?, d phia trai va K dphia phai (h^>h._) TiJc thi, vach ngan giira hai viing nude

dupe rut bd, do tac dung eiia lire trpng trudng nude tir phia trai tran sang phi'a phai Bai toan nay cd nghiem giai tich cho sir bien dang va di chuyen ciia cot nude Viec md

10

phdng qua trinh nay la kha khd ddi vdi md hinh nude ndng khi sir dung phuong phap sai phan hiiu han do ton tai gradient Idn tai diem ngan each hai viing nude

Di kiim tra so dd toan trong md hinh sd d day da sir dung viing nude chu nhat cd

dd dai 1000 m, dp cao h^ =3m d phia trai va /z2=lm d phia phai, hai viing nude cd dp

rdng bang nhau la 500m (xem hinh 1.2) Ket qua md phdng sd va nghiem giai tich cho thdi di^m 50 giay sau khi dap ngan giira hai viing nude bi vo, dugc trinh bay tren hinh

2 Hinh 2 cho tha'y cac nghiem sd sir dung cac so do khac nhau cho cac ket qua rat khac nhau va khac vdi nghiem giai tich, trong dd nghiem sd cua phuong phap sai phan

in six dung trong nghien cun nay ket hgp vdi so do CIP (xem hinh 1.3) cho ket qua gdn

triing vdi phan bd cua nghiem giai tich Hon nira cae nhidu gia do so dd sd khdng xuat

hien tai cac diem front cua cot nude Diiu nay cho ta mdt co sd tin cap de tin tudng vao

su 6n dinh va kha nang ung dung ciia md hinh cho cac bai toan thuc te

1.3.2 Kiem chumg vdi trudng hgp sdng dai dumg trong kenh thang

Do bai toan thuy trieu la mdt bai toan md phdng Ian truydn sdng dai nen nhat

thi^^t phai ki^m nghi6m md hinh toan ddi vdi trudng hgp sdng dung Day la mot trong nhirng bai toan kiem nghiem don gian nhung lai ra't hihi hieu trong viec kiem tra tinh

bao toan nang lugng eiia so do sd Bai toan dat ra la khi cd mot sdng dai truyen vao mot kenh thang cd dp sau khdng doi, kin mot dau Gia thiet phan xa hoan toan va khdng cd tac dung ciia luc coriolis thi do ket hgp ciia sdng tdi va sdng phan xa, trudng sdng dung se xu£t hien trong kenh vdi cac diem nut va diem bung phan bd theo qui luat Neu suy giam sd cua md hinh sd la nhd thi tai cac diem bung ta phai thu dupe cac dao ddng cd bidn dd it nha't la ga'p hai Ian bien dp eiia sdng tdi Tai cac diem nut cd cac dao ddng nhd Neu tinh phi tuyd'n dupe md phdng tot thi cac dao ddng tai diem nut

khdng bi triet tieu ma se xuat hien song thir ca'p cd t^n sd ga'p hai \in t^n sd ciia song

tdi

Vdi bai toan kiem tra thur hai nay, kenh din dugc chpn cd dp dai /=1000 m, dp

rdng b =50m, dp sau h =10m, sdng tdi cd chu ky r = 3 0 s , bien dp A =20cm Viing kenh

dugc chia thanh cac ludi hinh chir nhat 2,5m x 2,5m Bien tai cudi kenh dugc chpn la bien khdng tha'm (phan xa toan phdn) Thdi gian tich phan dupe chpn la 250s du de sdng truyen het hai Ian chieu dai kenh Cac ket qua md phdng dao dpng muc nude tai

cac di^m bung va diem nut (each nhau xen ke bang mot phan tu dp dai sdng L x T^fgh

dupe trinh bay tren cac hinh 1.4 va hinh 1.5

- Dao dpng tai bien Dao dong tai diem bung

T r

100 150 Thoi gian (s)

Hinh 1.4: Dao dpng mUc nu6c tai diem bung (diem ngay phia tru6c tu6ng diing) va dao

dong song t6i

Hinh 1.4 trinh bay dao dpng ciia muc nude tai diem bung ngay phia trudc tudng diing va dao dpng cua sdng tdi tai bien vao dau kenh Tren hinh ve ta thay, sau mot khoang thdi gian khoang 100 giay song truyen tdi tudng va hien tuong phan xa xuat hien Dao dpng tai diem sat tudng co bien dp gap hai Ian bien dp sdng tdi va on djnh sau mot khoang thdi gian rat ngdn Sau khoang 200 giay, sdng phan xa tir tudng ket hgp vdi sdng tdi tai bien va tao thanh mot song ket hpp, luc nay dao dpng ciia sdng tai

12

bidn khdng cdn la dao dpng cua rieng sdng tdi nira, ta cd the thay rd sir bien ddi ciia dudng dtJt net trdn hinh 1.4 cua dao ddng tai bien

Hinh 1.5 trinh bay dao dpng cua muc nude tai diem each tudng mdt khoang 5/4

dd dai sdng tdi ^ , tuong ung vdi diem gdn diem niit Ta tha'y sau khi sdng tdi di qua mot khoang thdi gian ngin co 130 giay thi sdng phan xa tir tudng quay lai gap sdng tdi tai dilm nay va tao thanh sdng ket hpp cd dao ddng nho hon rat nhidu dao ddng cua sdng tdi Dae biet ta cd the quan sat thay dao dpng cd tan sd cao tai diem nay do sir ket hpp phi tuy6'n giira sdng tdi va sdng phan xa chinh vi vay cac dao dpng muc nude van tdn tai d diem niit

Nhu vay md hinh sd cd the mo phdng tot trudng hpp Ian truyen song dai va md phdng dugc cac tuong tac giira cae sdng vdi sir suy giam sd khong dang ke Ket qua nay cho phep ta tin tudng vao md hinh de cd the ap dung cho cac bai toan truyen sdng dai tren thuc te

1.3.3 Kiem chumg vdi bai toan thuy trieu Bien Ddng

Md hinh sd da kiem nghiem d tren dugc ap dung tinh toan thir cho truyen trieu trong Bien Ddng Viing bien dupe chia thanh cac ludi hinh vudng vdi Ax =1/5 dp

Ay =1/5 dp, cac true dupe chpn xap xi hudng theo kinh tuyen va vi tuyen tren he toa dp

Di Cac Bien ciing dupe xap xi vdi didu kien thong lupng bang khdng Cac bien long

dupe cho cac dao dpng muc nude theo cac hang sd dieu hoa ciia 4 sdng chinh Cd ba bien long dugc sir dung cho mo hinh la eo Dai Loan, eo Basi va eo Malaea Cae hang

sd di6u hoa tren cac eo bien nay dugc lay theo bang thuy trieu Admiralty Tidal Tables [6] Cac toa dp diem la'y hang sd dilu hoa va cac bien dupe trinh bay trong bang 1.1

13

Bang 1.1: Cdc bifin long va cac hang s6 6iiu hoa

M2 H(cm)

Hinh 1.6: TrUcJng dong ehay trieu mo phong tren bien Dong

(luc 0 gid ngay 12/2/1988; mien tinh dUdc chia thanh 1116 theo kinh dp v6i bu6c lu6i 1/5

do va 116 6 theo vi do v6i bu6c lu6i 1/5 dp; go'c (0,0) tai toa dp (0,8'N;98,8°E))

14

600

Hinh 1.8: Dao dong mUc nu6c do trieu tai Qui Nhdn (bit dau tijf 0 gid 15/5/2002; Toa dp:

VI dp 13*'45'N, kinh dp 109n3'E )

Tren cac hinh 1.7 va 1.8 trinh bay so sanh dao dpng muc nude giira tinh toan theo

md hinh va thuc do tai hai tram hai van Hdn Dau va Qui Nhon Tren hinh ve ta thay dao dpng muc nude tinh toan kha phii hgp vdi sd lieu thuc do Dao dpng muc nude the

hien rd tinh nhat trieu diu a khu virc Hon Dau va xu the thay doi ciia dao dpng muc

nude tinh toan rat phii hgp vdi thuc te Tren hinh ve so sanh ta cung thay cd sir sai khac

nho vi bien dp tri6u giira md phdng sd va sd lieu thuc do, nguyen nhan co the giai

thich do vi tri lay ket qua md phdng sai lech kha Idn so vdi vi tri co sd lieu vi ludi la 1/5 dp va hon nira do ludi md phdng eon kha thd nen chua md ta dupe het nhimg anh hudng phi tuyen cua viing nude ndng va sir thay ddi dia hinh phu'e tap len dao dpng muc nude trilu Ndi chung md hinh da mo phdng dupe kha chinh xac dao dpng ciia tri^u tren Bien Ddng

15

1.4 NHi^N XET

Cac k6t qua ki^m chung md hinh cho mot sd bai toan ly thuyet va thuc te da

chung td phuong phap sd sir dung de phat trien md hinh la rat phii hgp Md hinh cd kha nang md phdng tot sdng dai trong vimg ven bd va ddng chay hai chi6u trong viing bien ndng Ket qua kiem chung d tren cho ta su tin tudng vao kha nang ung dung ciia md

hinh cho cac bai toan thuc l6

16

CHirONG 2:

MO HINH MO PHONG TRUYEN CHAT HAI CHl£u

2.1 H$ PHl/ONG TRINH CO BAN VA CAC DI^U K I £ N BIEN

He phuong trinh co ban dugc sir dung de phat trien md hinh md phdng Ian truyen

vat cha't trong nude la he phuong trinh truyen tai va khuech tan vat chat dudi dang hai

chi^u H^ phuong trinh dugc viet nhu sau :

dC dC dC d (^ dC\ d A-U— + v — = — D — +

' dy ^Q-oC (2.1)

dt dx dy dx\ dx) dy

Trong dd C(x,y,r) la ndng dp vat cha't trong nude; D^, Dy la he sd khuech tan

theo phuong cac true tpa dd; Q la ham ngudn; a la he sd phan huy

Cac dieu kien bien dupe sir dung la: tai bien cung cho rang thdng lupng truyen tai

vudng gdc vdi bien bang khdng; tai bien md truyen tai tu do va khuech tan tu do

2.2 H £ PHl/ONG TRINH DUdi DANG R O I RAC SIT DUNG PHl/ONG PHAP TVD

He phuong trinh (2.1) tuy don gian song de thu dupe nghiem sd hgp ly va ed dp

chinh xac cao lai khdng phai la van de don gian chut nao Thuc te tinh toan cho thay

neu sijr dung cac so dd toan thong thudng cd dp chinh xac hon bac 1 cho thanh ph^n

truy6n tai thi trong khdng gian nghiem thudng ton tai cae nhilu gia tao ra cac nghiem

am hay cac nghiem vugt qua cao so vdi nghiem dung De giai quyet van de nay thi mdt

sd tac gia da di sir dung so do ngugc ddng bac 1 de giai Tuy nhien phuong phap ngupc

dong (Upwind) bac 1 nay lai mdc phai sir khuech tan sd rat Idn lam cho nghiem sd

thudng nhd hon nhidu so vdi thuc va viing phan bd thi rdng hon De khac phuc van de

nay trong nghien cun nay chiing toi di sir dung so do FLUX-LIMITING cd dang TVD

vdi dp chinh xac bac 2 nhung khong gay nhi^u sd Dudi day trinh bay so dd toan nay

De don gian xet phuong trinh truyen tai mot chilu dang bao toan sau

Trong dd tham sd r dupe xac dinh theo bieu thure

Ddi vdi trudng hpp cd thanh ph^n khuech tan tham gia vao phuong trinh xuat

phat thi sau khi giai phuong trinh (2.3) theo so dd TVD rdi se them bieu thu'e sai phan

trung tam bac hai thdng thudng cho thanh phan khuech tan Cdn ddi vdi bai toan hai

chieu thi ta sir dung phuong phap tach, tire la ta di giai luan chuyen cho hai hudng x va

hudng y dudi dang bai toan mot chieu Ket qua eiia phep giai cho chilu thii: nhat se la

ban dau cho phep giai d ehilu thur hai Phuong phap trinh bay d tren tuy don gian

nhung lai ra't hiru hieu Dudi day se trinh bay mot sd kiem chung cho bai toan truyen

tai va khuech tan vat cha't cd nghiem giai tich

2.3 KI^M C H C N G M 6 HINH SO THEO CAC BAI TOAN L ^ THUYET

Tren thuc te qua trinh truyen tai va khuech tan vat chat lien quan den hai di6u

kien ban dau chinh: mot la phan bd vat chat cd gradient Idn cua nong dp theo khdng

gian tren mot pham vi hep (d gin ngudn thai - tuong ung vdi bai toan shock); hai la

phan bd vat chat cd gradient khdng Idn va phan bd trong pham vi rpng (d xa ngudn thai

- tuong ung vdi bai toan smooth) Do dd mot so d6 toan tot phai md phdng dupe tot ca

hai trudng hpp tren, cac nghiem sd khdng vi pham ban chat vat ly ciia hien tugng dugc

md ta (chang han vat cha't bi am, hay nhilu sd gia)

Dudi day se trinh bay cae kiem nghiem mo hinh vdi cae bai toan shock va smooth

neu tren cho cac trudng hgp mot chilu va hai ehilu

2.3.1 Bai toan mot chieu

a) Bai toan Smooth

Dieu kien ban dau ciia bai toan la eo mot ngudn vat chat phan bd dudi dang tron

tren nin ddng chay cd van tdc U =0.75m/s Gia sir he sd khuech tan bang khdng Ta di

m6 phong sir di chuyen cua ngudn vat chat nay Hinh 2.1 trinh bay phan bd ban dau

ciia vat chat Vdi dieu kien cho thi do khdng cd khuech tan nen dang phan bd n6ng dp

ban dIu phai giii* nguyen va chi tinh tien di theo trudng van tdc Do dd ta d6 dang tim

dupe nghiem giai tich

Hinh 2.2: phan bo n6ng dp theo thai gian tinh theo so d6 Upwind

(tnJcfng hop phan bd' ban dau tran)

— Lax-Wendrof

o Giai tich

x ( m )

Hinh 2.3: phan bo ndng 66 theo thcfi gian tinh theo so do Lax-Wendrof

(truong hop phan bo ban dau tron)

Ket qua md phdng so sanh vdi nghiem giai tich trinh bay tren hinh 2.2 khi sir dung so dd Upwind thdng thudng, hinh 2.3 ket qua sir dung so d6 Lax-Wendroff va hinh 2.4 la cua so dd Flux-Limiting TVD Ta thay vdi so dd Upwind suy giam sd rat

19

Idn, k^t qua md phdng khac xa so vdi nghiem giai tich Cdn vdi so dd Lax-Wendroff va Flux-Limiting thi khdng khac mSiy so vdi nghiem giai tich

Hinh 2.4: phan b6' n6ng d6 theo thcfi gian tinh theo so d6 Flux-Limiter (TVD)

(tnrcfng hop phan bd' ban d^u tron)

b) Bai toan Shock

Diiu kien ban d^u ciia bai toan la cd mdt ngudn vat chat phan bd dudi dang song

hinh vudng tren nin ddng chay cd van tdc U =0.75m/s Gia sir he sd khuech tan bang

khdng Ta di md phdng sir di chuyen ciia nguon vat chat nay Hinh 2.5 trinh bay phan

bd ban dSu ciia vat cha't Vdi dieu kien cho thi tuong tu nhu trudng hpp phan bd tron ta cung biet dupe nghiem giai tich

X(m)

Hinh 2.5: Phan bo nong do ban dau dang Shock

Ket qua md phdng so sanh vdi nghiem giai tich trinh bay tren hinh 2.6 khi sir dung so dd Upwind thdng thudng, hinh 2.7 ket qua sir dung so dd Lax-Wendroff va hinh 2.8 la cua so dd Flux-Limiting TVD Ta thay vdi so dd Upwind suy giam sd rat Idn dang md phdng khac xa vdi dang nghiem dung Vdi so do Lax-Wendroff thi t6n tai cac nhiau giai din den cac nghiem khdng thuc (hinh 2.7) Cdn vdi so dd Flux-Limiting thi cho nghiem gan dung nhat so vdi nghiem giai tich

20

Hinh 2.6: Phan bd' ndng dd theo thcri gian tinh theo so do Upwind

(tnrcmg hap phan bd' ban d^u Shock; U=0.75m/s, he sd' khuS'ch tan D=0.)

X(ni) Hinh 2.7: Phan bo nong dd iheo thcfi gian tinh theo sa dd Lax-Wendrof

(tnrcmg hgp phan bd' ban d^u Shock; U=0.75m/s, he so khuech tan D=0.)

Hinh 2.8: Phan bo nong dp theo thai gian tinh theo sa dd Flux-Umiter (TVD)

(trircmg hgp phan bo ban dau Shock; U=0.75m/s he so khuech tan D=0.)

21

Hinh 2.9 trinh bay ket qua md phdng so vdi nghiem giai tich trong trudng hpp ket hpp ca truyen tai va khu6'ch tan vdi he sd khuech tan la 0.15m2/s

2.3.2 Bai toan hai chieu

Bai toan hai chilu dupe tinh toan de kiem nghiem mo hinh so vdi nghiem giai tich vdi dieu kien ban d^u la nong dp phan bd dang trdn, trudng dong ehay dong nhat vdi f;=lm/s, K=lm/s He sd khuech tan la 0.2mVs Hinh 2.10 trinh bay phan bd n6ng

do va cac diiu kien ban dau

K^t qua trdn cac hinh 2.11, 2.12, 2.13 trinh bay phan bd nghiem sd va nghiem

giai tich d cac thdi diim gidng nhau Ta thay dang phan bd nghiem sd rat gidng vdi

phan bd cua nghidm giai tich

25

CHUONG 3:

tJNG DUNG MO HINH CHO VUNG VINH HA LONG

3.1 GI6I THifiU VUNG NGHlfiN CtfU

Vinh Ha Long thupc tinh Quang Ninh la mdt trong nhung ky quan cua the gidi da dupe UNESCO cdng nhan la di san thi6n nhien cua the gidi vao nam 1994 Ha Long

khdng chi noi tieng v^ thang canh tuyet dep ma noi day cdn dupe biet den vi nhirng truyen thuy6't, huy^n thoai ve lieh sir, vi tinh yeu, hanh phiic, ve van hoa va con ngudi

Witt Nam Ben canh dd, khu virc Cat Ba dupe xem nhu la mot viing du tru ngudn gen

cua bien Chinh vi vay, vimg Ha Long cd mdt tiem nang Idn cho phat trien kinh te du lich (hien nay, khu vuc Quang Ninh- Hai Phong thu hiit hon 25% tong lupng khach qudc te den so vdi toan viing ven bien va 13,4% sd lupt khach npi dia va du kien cdn tang manh trong nhung nam tdi, (Bao cao Bd Tai nguyen & Mdi trudng, 2004)) Khu vuc Quang Ninh la mot khu khai thae than Idn dang tren da phat trien (nam 2003 dat 18,5 trieu ta'n, du kien san lupng 2010 cd the len den 20 trieu tan, Bao cao Bd Tai nguyen & Mdi trudng, 2004), giao thdng van tai dudng thuy qua cae cang cd luu lupng Idn, tdc dp dd thi hoa eiia Quang Ninh vao hang cao ciia ca nude (Mai Trpng Thong,

1999) [5] Vdi nhung ly do tren thi iiim nang d nhi6m ngudn nude ven bien Quang

Ninh noi chung va d nhilm Vinh Ha Long noi rieng la van de cap bach dat ra can phai xem xet mot each than trpng de cd dupe nhung dinh hudng phat trien kinh te hpp ly Vdi muc tieu ung dung md hinh mo phdng ddng ehay va lan truyen vat chat vao tinh toan thir nghiem cho viing Vinh Ha Long, trong phan nay se trinh bay mot sd kei qua tinh toan ve trudng ddng chay trong vinh phat sinh do gid va thiiy tri6u Sau dd la cac ket qua md phdng lan truyin vat chat gia dinh gay ra do trudng ddng chay tong hpp

3.1.1 Gidi ban viing nghien curu

Gidi han viing nghien cuu la vinh Ha Long va Bai Tir Long, nam trong pham vi tu kinh tuyen 106°50' den 107°30', vi dp tir 20M5' den 2 r 0 5 ' Trong vijng nghien cuu cd dia hinh rat phu'e tap vdi nhidu dao Idn nhd nam rai rac vdi nhi6u hinh thu khac nhau Hinh 3.1 trinh bay so lupe ban dd vung nghien curu

3.1.2 Mot sd dac diem khi tuong thuy van vung nghien curu

Che dp thiiy van viing nghien cuu chiu anh hudng manh ciia thiiy Xniu va gid

miia Trong dd noi Irdi la cae hudng gid dong bac va ddng nam Ddng chay tu cac sdng

d6 ra vinh ddng vai trd khdng Idn den bien ddi che do thiiy van ciia vimg do luu lupng

tit cac sdng nhd va chi cd gia tri trong mua lu va tap trung chii yeu vao cac thang 6,7,8

26

Do vay trong nghien cihi nay chi di cap den ddng chay gay ra do gid miia va thiiy trieu

ma khdng tinh dS'n anh hudng ciia ddng chay trong cac sdng do ra

Hinh 3.1: Viing vinh Ha Long Quang Ninh

a) Gid trong vimg nghien cuu

Gid mua dong bac la yeu td quan trpng chi phdi thdi tiet Quang Ninh Trung binh mdi nam d Quang Ninh cd 20 den 25 dpt gid miia Trong miia ddng trung binh mdi thang cd 3 dpt gid miia ddng bac Nam nhieu nhat mdi thang co 4 den 5 dpt, nam ft nha't cung ed tir 1 den 2 dpt Khi cd gid mua, gid chuyen hudng dong bac, bac hoac tay bac Tdc dp gid Idn nhat thudng tren 15m/s Gio miia dong bac thudng xuat hien trong

cac thang 11, 12 va thang 1 Trong cae thang 2, 3 gid miia vi thudng gay ra mua phiin,

ed khi mua keo dai hang tuan Hau het cac dpt gid miia ve thudng gay ra giam nhiet dp dot ngdt trong 24 gid Chenh lech nhiet dp trudc va sau khi gid miia ve thudng khoang

4 den 5 dp C cd khi len den lO'C (Nguyln Van Tan, 1997) [41

Gid thdng ke do dac tai tram khi tupng thiiy van Hdn Gai dupe chpn lam dai dien cho vimg vinh Ha Long Bang 3.1 trinh bay thdng ke tdc dp gio trung binh cac thang theo tam hudng tai tram Hdn Gai trong vong 35 nam Bang 3.2 trinh bay tan suat gio xuat hien theo tam hudng tai tram Hon Gai Bang 3.3 trinh bay gia tri tdc dp gid manh nha't do dupe tai tram Hdn Gai

27

Bang 3.1: Toe dp gio trung binh cac thang theo 8 hudng (1960-1995) (m/s)

NE 2.8 2.9 2.7 2.7 2.7 2.8 3.2 3.5 3.6 3.6 2.9 2.7 3.0

E 2.4 2.3 2.3 2.5 2.4 2.5 2.4 2.4 2.7 2.7 2.5 2.5 2.5

SE 2.7 2.4 2.5 2.7 3.1 3.2 3.3 2.9 2.7 2.9 3.2 3.0 2.9

S 2.7 2.6 2.4 2.6 3.2 3.4 3.6 3.2 2.9 2.8 3.0 3.0 2.9

SW 2.5 2.1 1.8 2.1 3.4 3.4 3.6 3.3 2.9 3.5 2.8 2.2 2.8

W 1.4 1.5 1.8 2.3 3.5 2.4 2.1 2.9 1.7 3.0 3.0 4.0 2.5

NW 2.9 2.7 2.5 2.2 2.4 2.3 2.5 2.2 2.4 3.1 2.9 2.6 2.6

B a n g 3.2: T a n s u a t gid t h e o 8 htfdng (1960-1995) (%) Thang

E 10.3 11.2 8.5 9.6 10.2 7.3 5.3 5.3 4.7 7.6 7.4

7

SE 11.7 13.0 12.2 21.1 33.0 31.8 29.1 15.0 13.8 8.8 9.0 8.4

S 7.2 7.8 13.1 15.2 16.2 14.7 19.4 15.2 10.8 8.6 7.3 10.2

SW 1.3 1.8 1.4 1.6 1.0 2.7 4.4 4.6 1.6 0.5 0.5 0.6

W 0.2 0.4 0.2 0.3 0.4 0.8 1.3 1.2 0.4 0.2 0.1

0

NW 7.6 5.6 6.6 6.0 6.5 8.3 10.4 17.2 19.4 17.1 15.0 11.8

Lang 10.0 18.9 28.0 23.7 12.0 12.6 11.0 15.4 11.9 7.1 8.6 9.4

N

T4 40.0 SSE

T5 40.0

SE

T6 34.0 NNE

T7 45.0

SW

T8 40.0

SW

T9 40.0 NNE

TIO 28.0

N

Til 18.0

N

T12 20.0

N

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Thdng k€ v6 tdc dd gid trung binh nhieu nam trong cac thang va theo hudng tai

*> tram Hdn Gai ciing dupe th^ hien tren cac hinh ve ve hoa gid tir thang 1 den thang 12 tr6n cac hinh 3.2 den hinh 3.13

N NE E SE S SW W NW

Hudng gi6

Tan suat gio theo 8 hudng

Hinh 3.2: Hoa gio va to'c do gio trung binh theo cac hudng trong thang 1

£ 2

Si

^ #•-.>

"S™*' ' 5^'va

N NE E SE S SW W NW

Hucfng gio

Tan suat gio theo 8 hudng

Hinh 3.3: Hoa gio va toe do gio trung binh theo cac hudng trong thang 2

29

^ ^E

Tan suat gid theo 8 hi/dng

N NE E SE S SW W NW

Hiring gio

Hinh 3.4: Hoa gid va to'c do gio trung binh theo cac hu6ng trong thang 3

O Tan suat gio theo 8 hudng

Tin suat gid theo 8 hudng

Tan suat gid theo 8 hudng

N NE E SE S SW W NW

Hui'tng gio

Hinh 3.8: Hoa gid va to'c do gio trung binh theo cac hudng trong thang 7

Tan suat gid theo 8 hudng

N NE E SE S SW W NW

Hui'mg gio

Hinh 3.9: Hoa gid va toe do gio trung binh theo cae hadng trong thang 8

32

Tan suit gid theo 8 hudng

N NE E SE S SW W NW

HiK'mg gio

Hinh 3.10: Hoa gid va to'c do gio trung binh theo cac hudng trong thang 9

El Tan suat gio theo 8 hudng

N NE E SE S SW W NW

Hut'mg gio

Hinh 3.11: Hoa gid va to'c do gio trung binh theo cac hudng trong thang 10

33

N NE E SE S SW W NW

Hut'mg gio

Hinh 3.12: Hoa gid va to'c do gid trung binh theo cac hudng trong thang 11

Tan suat gid theo 8 hudng

Hinh 3.13: Hoa gid va tdc do gio trung binh theo cac hudng trong thang 12

Tir cac thdng ke ve gid ta thay hai hudng gio chinh chiem tan suat Idn nhat la d6ng bac (NE) va ddng nam (SE) cae hudng gio nay ed gia tri tdc dp trung binh tuong ung la 3.0 m/s va 2.9 m/s Trong nghien eihi d day se lira chpn hai hudng gid chinh nay vdi tdc dp trung binh de md phdng trudng ddng chay va lan truyen vat chat trong vjnh

Ha Long

34