Tap chi Khoa hoc va Cong nghe BiSn; Tap 14, Sd 1; 2014: 1-9 ISSN: 1859-3097 http://www.vjs.ac.vn/index.php/jmst
NGHIEN CLTU CAC DAC TRLTNG SONG DO BAO KHU VXTC VEN BIEN MIEN TRUNG VIET NAM
Vo Duy Long^"^*, Tran Thu Tam^
Vien Vgt ly thanh phd Hd Chi Minh-Vien Han lam Khoa hgc va Cdng ngh? Viet Nam Dai hge Bach Khoa-Dai hgc Qude gia thanh pho Hd Chi Minh, Viet Nam
Email: [email protected] Ngay nhan bai: 9-9-2013
TOM TAT: Nghien cim nay de cap den vdn de su dung mo hinh so de mo phong trudng gio trong bdo va tinh todn cdc dgc tnmg song do bao, lao ra day so lieu dgc tnrng song da ddi de co the dp dung cdc phuang phdp thong ke ddi han, nham xdc dinh quy luat phan bo xdc sudt cua dg cao song tgi khu v^cc nghien cihi. Kit qua cho thdy hdm phan bo Burr phu hgp nhdt cho chieu cao song trong khu vuc nghien ciru. Cdc ket qud phan bo chieu cao song trong khu vuc, ludn theo phan bd Weibull thudng diing cung dugc cung cdp de tien su dung. Ngodi ra kit qud thong ke hudng song ciing chi ra cdc hudng co do cao song nguy hiem trong bdo.
Tie khoa: Mo hinh song mo hinh gio bdo, dgc trung thong ke sdng, hudng song.
GlOl THIEU
Hinh 1. Khu vuc nghign euu Myc tidu nghien ciiu la md phdng cac dac trung sdng bao tiong nhieu nam de thirc hidn cac thong kd dai bgn, nhim xac dinh quy luat phan bo xac sukt cOa dO cao sdng bao tai khu vyc nghien ctiu, dong thdi xac dinh hudng ed tac dgng sdng nguy hiem.
Cac budc thuc hien gdm: lua ehgn, tdng hgp va phan tich cac con bao lich su anh hudng tdi khu vuc nghien curu. Tti so lieu bao thu thap duge, su dung md hinh trudng gid de md phdng tiudng gid trong cac con bao. Tir sd lieu trudng gid tinh toan dugc se dua vao md hinh sdng de tinh toan trudng sdng, xac dinh do cao sdng, kgt qua duge trich xu4t tai sau vi tri tieu bieu trong khu vuc nghidn euu.
Khu virc nghidn euu thudc khu vuc Bidn Ddng tu Da Nang ddn dao Phu Quy, vT tuydn lOV - 1 6 , 5 H kinh tuydn 106,7°E - 1 10,9''E.
M 6 PHONG TRITCTNG GIO BAG M5 hinh tham so mo phong trirdng gio
Nghien ctiu nay sti dung md hinh tham sd dd md phdng tnrdng gid bao. Trudng gid trong bao la sir tdng hgp bdi hai thanh phSn (hinh 2).
Thanh phan F duge tao ra bdi v^n tdc di ehuydn ciia tam bao Vf va thanh phin van tdc gid gradient W^ do gradient ap suat gay ra.
Vo Duy Long, Tran Thu Tam
dgi, Wmax (m/s) la van tdc gid gradient e\rc dai, r (m) la ban kinh tinh tii tam bao den diem tmh.
We(r) = W „ a x | ^ (2)
Hmh 2. Vector tiudng gid trong con bao So hang F dugc tinh theo cdng thuc (I), de nghj bdi Jelesnianski [3].
_ p_ f —
De xae dinh ^ , nghien ctiu nay dua vao ldi giai tr^c tiep tir phuong tiinh chii dao cua md hinh trudng gid SLOSH, dugc Trin Thu TSm [3] de xuSt, vdi mgt gia thidt dg don gian hoa ldi giai. Phuang tiinh dgn gian hda de tinh ^ dugc thd hi?n d(3).
"wmax" ff2
k,W, •s'^'^g
Vgn tdc gid gradient Wg dugc tinh theo md hinh trudng gid eua Jelesnianski [2], tiong do phuong ciia vgn tdc gid gradient W lech vao tam mgt gdc ^ so vdi phuong tigp tuydn cua vdng dang ap. Dg ldn cua v|n tdc gid gradient Wg dugc eho d edng thiic (2), vdi R^max (m) la ban kinh tii tam bao ddn vi tri cd van tdc gid cue
/
c o s ^
W„ dW„ k„W, dr
g cosip
(3)
Vdi: f la thdng so Coriolis (don vi: rad/s). ks va I^ (don vi la 1/m) la h# sd ma sat theo phuong tidp tuydn va vudng gdc vdi quj^ dgo lay theo Jelesnianski [1]. Don vi ciia Wg, Vf: m/s.
Thurc hi^n mo phdng tnrdrng gid trong CCD
Hinh 3 Kdt qua mo phong truong gio trong con bSo Frizt
Vdi so lidu track bao cua con bao Frizt dd 18:00 ngay 25/09/1997. Tren hinh 3 the hi?n bg vao Da Nang 23/09/1997. Nghidn euu md trudng gid trong bao dugc tinh ra t^ ket qua phong trudng gid cua con bao nay trong thdi - ' • • . - ^ • .
gian 54 gid tir 12:00 ngay 23/09/1997 ddn
md phdng con bao Frizt (1997).
Nghien cihi cac dac tmng smg do bao ..
TINH TOAN T R i r d N G S 6 N G CHO M O T CON BAG D I I : N HINH
De md phdng trudng sdng do bao, ph4n mdm Delft3D dugc su d\ing. Delft3D la mdt b9 md hinh ba chieu dugc dung de nghidn euu vd thuy dOng Ivc hgc, v§n chuyen biin cat, hinh thai... ciia Vi$n nghien ciru ung dung Deltares, Ha Lan. Delft3D cd nhieu module chay dge lap vdi nhau. Module tinh sdng DelftSD - WAVE sti dung md hinh SWAN de tinh sdng.
Lirdi tinh to^n
Hinh 4. Ludi dugc su dung de tinh toan sdng Ludi tinh la ludi cong true giao trong he tga dg UTM mui chieu 49 N, khoang each ludi dugc lay thua d ngoai khoi (khoang 900 m) va min dan khi vao bd (khoang 200 m), (hinh 4).
De lira ehgn dg rgng mien tinh tir bd ra ngoai khoi, nghien ciiu thu nghigm tinh toan vdi cac ludi cd dg rgng khac nhau gdm 700, 550, 400 va 200 km. Kdt qua tinh toan cho con bao mang s6 higu 195227 do bg vao Khanh Hoa nam 1952 cho thay: tai thdi didm ed dg eao sdng cao nhat, dg cao sdng vdi ludi tinh 200 km nhd hon trudng hgp ludi 700 km 30,25%; dg eao sdng ludi 400 km nhd hon tnrdng hgp ludi 700 km khoang 7,46%. Ket qua tinh toan trong bon trudng hgp duge thd hi^n trong hinh 5. De tiet kifm thdi gian tinh toan ludi cd dO rgng 400 km dugc l\ra ehgn.
Hinh 5. Kdt qua tinh toan do cao sdng vdi cac ludi cd do rdng khac nhau Birdc thdi gian
II:
^ , « . ID phiit / N ^ 50 phut
^~- "
Hinh 6. Kdt qua kidm dinh tinh toan vdi cac bude thdi gian khae nhau.
De lira chon bude thdi gian tinh sdng, nghien ciiu cung da thue hien vdi eae trudng hgp bude thdi gian 10, 30, 40 va 60 phiit. Kdt qua tinh toan cho eon bao Frizt cho thay trudng hgp cac bude thdi gian tu 10 phut tdi 40 phut su chenh leeh do eao sdng khdng dang kg (hinh 6). VI thg, budc thdi gian 40 phiit dugc ehgn cho cac tinh toan sdng.
Dieu kien bien, dieu kien ban dau Gia thiet bd qua sdng lan truydn tu ben ngoai vao mign tinh tai cac bidn Idng, didu kidn bidn duge xem nhu didu kien bidn Neumann.
Md huih tinh sdng dugc thuc hien bat dSu tii liie bao di vao ludi tinh, trudng sdng liic nay bang 0. Md hinh thue hien lam ndng trudng sdng bang each gia dinh eho ecm bao dn dinh t£ii bign cua khu vuc nghign eiiu dii lau va gay ra trudng sdng dn dinh trudc khi tinh diln bien theo thdi gian d eae budc sau.
Kiem dinh ket qua ti'nh toan vdi gia tri thuc do '
Kdt qua tinh toan dugc kigm dinh vdi sd lieu sdng thuc do do TEDI va JICA thuc hidn thang 9 nam 1997 tjii eiia vinh Da Ning (tga dd 16'ir34"N, 108°15'27,7"E) thdi didm didn ra
Vo Duy Long, Tran Thu Tam
con bao Frizt, khoang thdi gian so sanh tir 12:00 phdng^eon bSo Frizt dugc cho tren hmh 7. So 23/09/1997 ddn 18:00 25/09/1997, kdt qua md ligu kiem dinh dugc tham khao tu [1].
Hinh 7. Ket qua md phdng trudng sdng trong eon bao Frizt Bang 1. Ket qua kidm dinh dg cao sdng ed nghta
23/09/97 12,00 23/09/97 ie.00 24/09/97 0:00 24/09/97 6:00 24/09/9712 00 24/09/97 IB 00 25/09/97 0 00 25/09/97 6 00 25/09/97 12 00 25/09/9718 00
Hs(m) 1.8 2.1 2,2 2,6 3,3 4,2 5,1 4,1 2,7 2,3
Hv6ng
ssw sw sw
wsw wsw sw
Hs(m) 0,62 0,86 1,32 1,B9 3,19 3,87 4,87 4,2 1,51 0,74
Hirfrng SSW
sw wsw wsw wsw wsw wsw wsw w w
do dugc tai cac thdi diem khac so sanh vdi ket qua tinh toan eho thiy: hudng sdng tiong trudng hgp thuc do va tinh toan khdng cd sai lech dang kd.
f ; '1.
3
- T I
.i:*i
. TJ»I-
.,
^3/03,31 ui^*f09/97,^.Qo "'^S'S^ftoo " ' " ^ ' S ' iam
Ket qua so sanh dugc trinh bay trong bang 1 va hinh 8. So sanh dO eao song tinh toan vdi gid trj th\rc do, ket qua nhSn thay nhu sau:
H^ so tuong quan giiia gia tii thuc do va gia tri tinh toan la: R^ = 0,95 eho thay moi tuong quan giiia gia trj th\rc do va gia tii tinh toan la kha eao.
_Gia tri do eao sdng cao nhSt trong suot ehudi tinh toan ciia trudng hgp tinh toan va th\re do ehdnh nhau 4,5%.
Kdt qua th^c do huong sdng khdng duge diy dii tir thdi diem 06:00 24/09/1997 den 00:00 25/09/1997. Tuy nhien vdi nhiing ket qua
Hinh 8. Dd thi the hign ket qua th\rc do va ket qua tinh toan dg cao sdng cd nghTa Ket qua kiem djnh cho thay vige ket hgp md hinh gid va mo hinh sdng vdi cac thdng so da ehgn la phu hgp. Phuong phap md phdng sdng do gid bao nay se dugc ap d\ing cho tinh toan hang loat cac con bao lich sit d phan thong kg cac dac tnmg sdng.
T H 6 N G K E C A C » A C TRITNG S 6 N G DO BAO
Ngudn so lif u bao
DG li$u track bao dugc liy tti Trung tam lien hgp canh bao cua My (JTWC) vdi mdi 6
gid mdt so li?u, tii dd cd the tii'ch xuat ra tga do tam bao va toe do gid ldn nhat. Sd lieu dugc khao sat tu 1952 - 2012. Viec lua chon cae eon bao anh hudng tdi khu vuc tinh toan dua tren cac tieu chi sau:
Cac con bao do bg vao mien tinh cd v$n toe gid c\rc dai ldn ban 25 knot.
Cac con bao do bg vao khu vgc each hai diem tinh Da Nang hoac dao Phii Quy 200 km va cd tdc dg gid cue d^i Idn hon 25 knot.
Dd ed dugc sd ligu cac dae trung sdng do bao, nghien ciiu tien hanh tinh toan trudng sdng ciia tong cgng 112 con bao da lua ehgn tiong suot 60 nam, vdi quy trinh tfnh toan tung con bao dugc th\ic hidn tuong tu nhu tinh toan con bao kidm dinh da du^c gidi thi?u trong phan trudc. De cd dugc kgt qua nghign ctiu ve ckc d&c trung sdng khu vue nghidn ctiu, sau digm tinh toan tai viing nudc sau duge lira ehgn trai deu dgc khu vuc nghien
Nghign ctiu cac dSc trung song do bSo ...
ctiu. Cac digm nay nam d ngoai vung nudc sau gan cac khu v\rc Da Nang; Nui Thanh - Quang Nam; Phu My - Binh Dinh; Quy Nhon - Binh Djnh; vmh Van Phong - Khanh Hda; dao Phii Quy - Binh Thu|n.
Phan bo sac suat chieu cao song.
Tir cac gia tri dg eao sdng tinh dugc tai 6 didm trong 112 con bao, thuc hidn tinh toan tin suat vugt cua chidu eao sdng tai cac didm va xip xi cac gia trj xac suit thuc nghigm sd nay vdi cac ham phan bd ly thuydt khac nhau dk ehgn phan bd phii hgp nhat.
Dd xac dinh cae ham phan bd xae suat ly thuyet phii hgp nhit, nghien curu da dua vao sai sd trung phuong RMS de danh gia s^r phii hgp eua 6 ham phan bd ly thuydt gdm: phan bd Weibull, phan bd Burr, phan bd LogPeason3, phan bd Exponential, ham phan bo Johnson SB, phan bd GEV (Generalized Extieme Value).
Bang 2. Sai sd RMS ciia cac ham phan bd xac suat khae nhau ciia do eao sdng (dan vf: m)
Dd NSng PhCi My Quy Nho-n V3n Phong Ddo PhCi Quy
Weibull Burr LogPeason3 Johnson SB Exponential GEV
1,7523 1,696 2,1748 1,2552 1,575 3,8395
2,3923 2,033 2,2161 1,7287 2,026 3,8356
3,0935 1,51 1.8369 3,0278 3,256 1,7653
1.7174 1,113 1,2 1,3798
3,023 1,7226
1,5756 1,438 1,615 1,7518
3,55 1,8134
2,1191 1,9839 2,2765 3,1383 2,624 2,0808
Hinh 9. Phan bd xac suSt gia trj c\rc tii dg cao sdng tai tr^m Da Nang
Ket qua dugc thd hijn tren bang 2 eho thay tai cac digm tinh Da Nang va Niii Thanh, ham phan bd Johnson SB cd gia tri sai sd nhd nhSt.
Tai cac digm tinh Phu My, Quy Nhon, Van Phong va dao Phu Quy, ham phan bd Bun cd sai sd nhd nhat. Nhu vay ham phan bd Burr la kha phii hgp de diing chung cho ca khu vuc nghien ciru. Hinh 9 thg hien dudng cong phan bd xac suat gia tri cue tij dg eao sdng t^i tram Da Nang dugc tinh tu ham phan bd Burr.
Trong nghidn ctiu vg sdng bien, phan bd Weibull duge su dung phd bien hon phan bd Burr. De thuan tien cho vi$e su dung, cac ket qua phan bd xac suat chieu cao sdng irng vdl ham Weibull eung dugc cung cap va ddng thdi so sanh vdi ham Biur tien hinh 10.
V5 Duy Long, Tran Thu Tam
' " \ - -
- -
N^
0 (.
'°"=*===-^
^ - - !
a) Dk Nang
-
•
-
j) Nui Thanh
X
" " ^ ^ i i :jo O O m "
Sr
c) Phil My
\
\
\
\ I
16 0 oo
:£?^
•
\
\
\
d) Quy Nhon
V
l?-H_5S."SS'
1
e) Van Phong f) Dao Phu Quy Hinh 10. Bidu dien dudng eong Weibull va Burr t^i cac tr^m Ket qua tdng hgp nhu sau:
Dang ham Weibull:
P%=e''^ " '^''.100%
Dgng ham Burr:
mj-^'
(5)Cac tham sd tuong ting cho sau tr^m dugc (4) lidt kg trong bang 3. Cac kSt qua tuong t\f cho chu ky sdng cung d5 dugc thyc hign nhung khdng tihih bky d day.
Nghien ciiu cac d§c trung song do bao ., g 3. Cac tham sd trong ham xac suat vugt Burr va Weibull cua chidu cao sdng.
DiHSng NO)Thknh PhClMjr Quy N h o n VSn P h o n g C d o Phti Quy
k 4,84 1,514 1,091 2.597 15,83 3,889
B u r r a 1,115
1,55 2,043 1,652 1,435 1,303
P
7,553 2,39 1,812 3,618 14,01 3,251
a 1,0082
1,096 1,249 1,4659 1,2961 1,1532
Weibull
P
1,915 2,2769 2,3165 2,3511 2,023 1,2927
Y 0,0717 0,10131 0,103
0 0,0634
0
Ket qua so sanh dg cao sdng cd nghTa irng Weibull va dudng cong Burr dugc bidu didn vdi tan suat vugt Hs (1%) tinh tu dudng cong tidn hinh 11.
• Hs(l%)Biin-
Hinh II. BQ cao sdng cd nghTa iing vdi tan suat vugt 1% tai cae digm duge tinh tu ham Burr va Weibull
Hirdng sdng nguy hiem
Hoa sdng the hign tan suit xuat hien dg eao sdng nguy hiem theo eae hudng tai 6 diem dugc bieu didn trong hinh 12. S\r xuat hign dO cao sdng do bao theo cac hudng t^i 6 diem nhu sau: Tai khu vuc Da Nlng sir xuat hien dg cao sdng nguy hidm (cao hon 4 m) chu yeu tap tiling d hudng,Tay TSy Nam (WSW), Tay (W) va Tay Tay BSc (WNW) vdi tan suat xuat hign khoang 10,8%. Tai khu virc Nui Thanh s\c xuat hi?n dg cao sdng nguy hiem ehu yeu tap trung tur hudng Nam (S] tdi hudng Tay Tay Bac (WNW) vdi tan suat xuat hien khoang 18,9%.
Tai khu v\ic Phii My s^r xuAt hl$n do cao sdng
nguy higm ehu ydu tap trung tu hudng Nam Tay Nam (SSW) cho tdi hudng Tay Tay Bae (WNW) va hudng Nam Ddng Nam (SSE) vdi tin suat xuat hign khoang 12,6%. Tai khu vue Quy Nhon su xuat hien dg cao sdng nguy hiem ehii yeu tap trung tir hudng Nam (S) tdi hudng Tay Tay Bac (WNW) vdi tan suat xuat hien khoang 8,1%. Tai khu vue Van Phong sir xuat hien do eao sdng nguy hiem ehu ydu tSp trung tir hudng Nam Tay Nam (SSW) tdi hudng Tay Tay Bae (WNW) vdi tSn suat xuat hien khoang 10,8%. Tai khu vv:e Dao Phii Quy sir xuSt hien do cao sdng nguy hidm chu ydu tap trung d hudng Nam (S) vdi tan suit xuat hl?n khoang 2,7%.
Vo Duy Long, Tran Thu Tam
N N W ^ - D - l — - y j N E
Da Nang
ss^jS-^-'isE
PhiiMS'
Quy Nhon Van Phong Dao Phu Quy
Hinb 12. Hoa sdng tan suat xuat hign dg cao sdng nguy hiem theo cac hudng tai 6 didm K t X L U ^
Nghidn eim da d\ia vao md hinh sd de md phdng trudng gid bao va trudng sdng cua cac eon bao lieh su va da dua ra dugc cac kdt qua vg cac d^c trung sdng bao tai khu vuc ven bien Midn Trung, t?io eo sd eho nhung nghidn ciiu tiep theo trong tuong lai t?ii khu vuc nay, noi ma van cdri it dugc quan tam nghien euu. Kdt qua cho thay ham phan bd xac suat ly thuyet Burr phii hgp vdi eae gia tri xac suSt thuc nghigm so eiia do eao sdng t^i khu vuc nghien ctiu. Nghien euu da dua ra dugc cae ham phSn bo^ xac suat cua chieu cao sdng t^i 6 digm Da Nang, Niii Thanh, Phii M^, Quy Nhon, Van Phong va dao Phu Quy. Kdt qua phan bo xac suat theo Weibull ciing dugc cung cap de so sanh. Nghign euu cung da xac djnh dugc cac hudng ed tac dgng sdng nguy higm eho tiing tram. Van de nghign ciiu can th\ic hign tiong
tugng lai la keo dai so lidu cac eon bao bang each thu thap them sd li?u bao va tao ra cac con bao gia djnh nhSm dgt dugc kdt qua cd dO tin cg.y cao hon.
TAI L i f U THAM KHAO
1. Jelesnianski C. P., 1967. Numerical computation of storm surges with bottom stiess. Mon. Wea. Rev., 95, pp. 740-756.
2. Jelesnianski C. P., Chen J, Shaffer W. A., 1992. SLOSH: Sea, Lake, and Overland Surges from Hurricanes. NOAA Technical Report NWS 48, April.
3. Trdn Thu Tam, 2011. Md Hinh hoidng gid bao don gian hi$u chinh theo s6 ligu bao ljeh su ciia RSMC-TOKYO. Ky yeu hgi nghi khoa hgc va cdng nghg lan thii 12 D^i hgc Bach Khoa Tp. Hd Chi Minh.
Nghign ciiu cac dac tnmg swig do b3o ..
RESEARCH ON STORM WAVE CHARATERISTICS IN CENTRAL COAST OF VIETNAM
Vo Duy Long'*^, Tran Thu Tam^
'Ho Chi Minh eity Institute of Physics-VAST
^Ho Chi Minh city University of Technology
ABSTRACT: In this research, the numerical model was used to simulate the wind field, and then the wave field of the storm. Using historical best tracks of the storm, the characteristic waves along the coast have been collected after each storm simulation In this way, we created long series of wave characteristics, and then the statistical method was used to obtain the probability distribtdion Junctions of the wave heigla. The results show that the Burr distribution function fitted well to simulated value of wave heights. The results written inform of popular Weibull distribution function are also showed for practical purpose. Furthermore, this research also determined the
dangerous direction of wave in storm, based on the statistical characteristics of the wave storm.
Keywords: Storm wind model, wave model, statistical wave characteristics, wave direction.
