341
Tuyin tap cdng trinh Hdi nghi Cff hoc todn qudc Ky niem 30 ndm Vien Cff hge vd 30 ndm Tgp chi Cff hoc Hd Ndi, ngdy 8-9/4/2009
Vi dii tinh thanh phan nguon nuoc trung binh ciia mang luoi song phiic tap anh huong trieu tren co* so" he so khuech tan tong hop
Huynh Chiic
Trudng Cao ddng Tdi nguyin — Mdi tnedng Dili Viet Hung
Trung tdm diiu hdnh chuang trinh chdng ngap niedc Tp HCM
Tom tat: Sau phep trung binh hod cho mdt vdi con trieu (nica tudn trdng, mdt tudn trdng...), cluing tdi dd dica vdo he sd khuech tdn tdng hgp chung cho cdc thdnh phdn ngudn nicdc trong he thdng sdng vimg trieu phicc tgp vd cd the phdt trien bdi todn hodn chinh tinh cdc thdnh phdn ndy. Bdi bdo dica ra cdch ddt bdi todn vd dudng ldi gidi bdi todn dd thdng qua mdt vi du.
\. M6- dau
Trong [2,3] ehiing tdi da lap phuong trinh tfnh thanh phan nguon nude trung binh cho nira hoac ea tuan trang trong he thdng song viing trieu va Idi giai ciia phuong trinh nay sau khi chirng minh rang cac he sd khuech tan Dj eiia tirng thanh phan ngudn nirdc la ddng nhat vdi nhau [4,5] va ki hieu chung la D, cho dudi dang tong quat:
m, - P, {x,) = [m, - p, (x, )}e " (1) trong do:
Vf - luu tdc trung binh doan 1 — 2
m,: la ti le luu luong ngudn ddng chay thir i trong tdng luu lugng ddng chay doan song dang xet.
Khac vdi djnh nghTa chua diing ve m; trong [5] d day n\ duge tfnh nhu sau:
Nguon i tir bien tren dd vao chua tron lan vdi ngudn nude thugng luu khac (tren nhanh don tir bien vao) thi: /77, = /
Vf du: Ngudn Diu tiing tren sdng Sai Gon tii' chan cdng trinh den nhap luu ciia sdng Thj Tfnh: niirr =./
Tir bien khdng ed ngudn nude thudng xuyen (trung binh nira hoac ea tuan trang) nen d cira sdngy'.' nisj = 0
Ci chd mit hgp luu ciia cae nhanh song (n nhanh vao va i nhanh ra) vdi gia thiet xao tron hoan toan tai mit ta ed tai cae nhanh ra k (xem hinh 1).
J)42 Huynh Chiec, Bui Viet Hung
T"\mQj
' " ( 0 A ' = -,/=' ,K = I,2....1
7 = 1
(2)
Hinh 1. Niit hgp luu
Nhu vay: Tren nhanh do vao j e ( l , 2 n) nao do khdn'g pha tron ngudn i thi khi tfnh xem
m,fi, ~ 0.
Trong [5] ehiing tdi da so bp thiet lap bai toan tfnh thanh phan ngudn nude trung binh pi vdi cac dieu kien bien.
Bien tren: P , ( „ . ) = ^ l - -
W. nguoc(i) W, f(i) trong do:
W„j;,ioc(i): Tong lugng chay ngugc trong thdi gian lay trung binh.
Wf(i): Tong lugng ngudn thugng luu trong thdi doan T.
Bien duoi: W,
P.. ngiioc(S) w..„
trong dd:
W„g„oc(S): Tong lugng nguIn biin.
Wra: Tong lugng trong cae pha trieu chay ra.
Dilu can luu y la dp chfnh xac eiia dilu kien bien tren gia trj I-p,(i,) rat nhd, gan vdi sai so tfnh toan eho nen sai s6 d bien nay se lam cho trj so I -p, a doan dudi bj khuech dai do
l-pXx) = [\~pXb)V^ = K[\-p,{b)\ (3)
Vi du tinh thdnh phdn ngudn medc trung binh ciia mgng liedi sdngphiec tgp anh hudng triiu tren co sd he sd khuech tdn tdng hgp
vdi he sd:
343
(4) vdi K » l khi x di dan xudng dudi va khi do, sai so: Spi(x) » Sp^ipien) la dieu noi len tfnh khong ben vu'ng (dn djnh) ciia so' dd tfnh.
Cach dat bai toan la cho m, tai eae bien, vdi bien nguon i, inj(t,j^i,)=l va bien dudi m,(s)=0 Cling dieu kien bien dudi tai cii'a sdng
W.
A = • nyuoctS)
w„
w.
w,
(kbiWf«W,„,,„e(S,) (5)nguoc(S)
Sai so tfnh ps(x) bj giam dan khi chuyen dpng ngugc len vdi he sd K"' (K>1 va khi khoang each dii dai K » l ) vay ludn cd dieu kien ben vung.
Sp^{x) <5p^(bien)
Trong tfnh toan tiep theo cho doan kenh song giu'a 2 mit hgp luu M va N cac tri so m, khong doi va gia sir doan nay chia ra lam n doan nho bdi eae mat cat 1,2 , n+1 (hinh ve 2)
(6) 1 2 n n+f
Hinh 2. Doan sdng giu'a hai nut hgp luu.
Bay gid ta c6:
KMN~K.I.2 K2-3 K|,_„-n = 1 1 A.^^^.^1
, / = l • "
trong do: KMN : la he sd cho mpi thanh phan nguon nude.
Ta xem xet mdt sd vi du tfnh toan dudi day.
2. Vi du tinh toan nhanh song don
Vf du 1: Gia su' ta cd nhanh sdng don ndi tii' ngudn den eiia bien vdi 6 doan va 7 mat eat.
Cae he sd K eiia tirng doan (udc lugng theo [5]) eho trong bang sau:
Doan Sdng He S6 K
1 - 2 1,60
Bang 1. He sd K ciia doan 2 - 3
3,32
3 - 4 4,96
song 4 - 5 4,22
5 - 6 2,02
6 - 7 1,80
344 Huynh Chiec, Bid Viet Himg
vdi be so K eho toan sdng tir nguon den cira la:
./=i
vdi dieu kien bien cira sdng (lay theo [1]) P(S)7 = 92,82%
Bay gVapfsji se la
P(S)X=P(S)TK;1I = 9 2 , 8 2 x 4 0 4 , 2 7 " ' = 0 , 2 3 0 %
Til' day, so lieu thanh phan p ngudn va ps bien tai cac mat cat cho trong bang 2 (1-p tinh xudi va Ps tinh ngugc).
Mat cat 1 - p P Ps
1 0,230 99,770 0,230
Bang 2 2 0,368 99,632 0,367
Trj sd p, Ps 3 1,222 98,778 1,220
tai eae mat eat (%) 4
6,060 93,940 6,049
5 25,573 74,427 25,528
6 51,657 48,342 51,567
7 92,983
7,017 92,820 Dimg nhu bien luan ve phat trien sai sd khi tfnh p, sai sd lam tron 0.0005 thi d mat cat 7 sai so tinh p cd the la 0.202 {S f,) mat cat 7 (sai so Idn nhat).
P- + P'(S)7 =7,017 + 92,820 = 99,837
Sai sd la: -0,163 % eo the chap nhan dugc. De tranh thii tuc tinh xudi ddng (nhan vdi Kjj+i>l ) gay khong on djnh (ben) ta tfnh cae thanh phan truyen nguge (chia vdi Kjj+i) va cac ngudn thugng luu vdi trj so bang phan bu den 1 cua p^.
Vi du 2: Sdng chia doan nhu trong vi du 1 va dugc biet Qf = 30m^/s. Bay gid tai mat eat 4 CO lugng nude thai tap trung Qt = 6 mVs. Ta udc lugng trudc bien cac bien ddi he sd K ciia cac doan song.
Ta nhd rang:
" / i j . j ^ i ) ( ^ ' ; - i - - ' ^ y '
^./,7.i = ^ (7)
Vi khoang each Xj+i ,Xj khdng thay dii, gia sir vdi biin ddi nhd ve luu lugng Djj+i bien doi khdng dang kl (he sd khuich tan chii ylu do dao ddng trieu tren doan sdng gay nen). Nhu vay, ehi eon Vf biin doi, tir mat eat 4 trd xudng luu lugng tang 6/30 = 20%, nhung Vf khong phai tang vdi ti le 1,2 ma do mue nude Zf eung tang nen udc lugng Vf tang 1,05 lan va
< , . . = ( ^ / . , . i r v d i j . 4
Vidu tinh thdnh phdn nguon medc trung binh cita mgng ludi sdngphiec tgp dnh hiedng trieu trin co sd hi sd khuich tdn tdng hgp
345
Tuong tu nhu vay, tir mat eSt 4 trd len Qf van la 30in7s, nhung do nude ir len phfa ha luu, Vf bj giam cdn 0,98 Vf, va d doan nay
^;,„,=(^„J"v«j=:3
Trong khi do tir mat cat 4 trd xudng, be sd ngudn m nhu sau;
Nude ngudn : m = 83,33%) Nude thai: m, = 16,67%
Tir mat eat 1 den 4, chi ed he sd m nude ngudn, m = 100%
Ta ki hieu cac dae trung tfnh toan eho trudng hgp nay vdi dau phay.
Dau tien ta tinh K , sau dd tfnh p s tir mat eat 7 len tdi mat eat 1. Lay phan bii tdi 100% ciia p s ta dirge p' + p'lVa tir doan 4 trd xudngp vap, chia theo ti le ngudn (theo m hoac theo Q, Q,) - Tir mat cat 4 trd len tinhp,truyen tir mat eat nay trd len (nit = 0) va trii' vdip' + p',dc co P-
Tai mat eat 7 trj sop'^ bien ddi nhu sau: Theo vf du 1 (chua ed nude thai) ta eo Wf _ „
Psi = 1 Wf
w,„
• - >
w...
\Tu" day khi xem Wnguoc bien doi khong dang ke, Wftang len 1,2 lan ta du'gc:
Wf
w,.
w
= 1 0 0 - 9 2 , 8 2 = 7,18%
^ = 1,2x7,18 = 8,62%
w„,
Vay p 's? = 100-8,62 = 91,38%
Ta ed bang tfnh sau:
,,Bang 3. Thanh phan gnuon nude khi ed them nude thai Mat eat
1 2 3 4 5 6 7
K 1,60 3,32 4,96 4,22 2,02 1,80
K' 1,585 3,241 4,804 4,535 2,092 1,854
P's 0,210 0,334 1,081 5,195 23,560 49,288 91,380
Ps 0,230 0,367 1,220 6,049 25,528 51,567 92,820
P'+P't 99,790 99,666 98,919 94,805 76,440 50,712 8,620
P't 0,625 0,991 3,289 15,801 12,740 8,452 1,437
P' 99,165 98,675 95,630 79,004 63,700 42,260 7,183
P 99,770 99,633 98,780 93,151 74,472 48,433 7,480
346 Huynh Chiec, Bin Viet Himg
Trong bang 3 ta dan ra ti le ps va p trudng hgp khdng ed nude thai dl so sanh. Ta thiy, nlu dp man trung binh ciia sdng la S=28 /oo, va nude thai ed ndng dp BOD la 450mg/l thi tai cac mat cat 1,2,3 ta cd:
Bang 4. Dp man va ndng dp BOD Mat cit
1 2 3 4 5
S(°/oo) 0,0644 0,1028 0,0416 1,6900 7,1400
S'(°/oo) 0,0588 0,0935 0,3027 1,4300 6,6000
C(mg/1) 2,81 4,46 14,80 71,10 57,33
Neu xem tri so max eua S va C vdi dao ddng dieu hda theo trieu va khong cd gia trj am gap doi trj sd trung binh thi tai mat cat 2 cd the dat tram lay nude tieu dimg S,„a.x = 0,2 (%o) va C.nax s 9mg/l nhung tai mat eat 3 ndng dp BOD max len tdi 30mg/l vupt qua mue eho phep dii dp man chi cd 0,6 °/oo
3. H e thong kenh song phu'c tap
3.1. Tinh todn thiiy lire
Cho mang ludi phire tap khi trung binh hoa ta cd bai toan ddng dn djnh, vdi bien tren la cac luu lugng Qfbien va bien dudi la muc nude trung binh Zj tai cae cira sdng. Ldi giai cua bai toan nay cho ta Qf tai cac nhanh song, Zf tai eae mat eat va tir dd dien tfch mat eat irdi Af va suy ra Vf.
Neu cd quan he tim D, ta se tinh ngay dugc eae Kjj+i va K ciia cac doan sdng kenh, giua cac niit hgp luu.
Cach giai cac bai toan thiiy luc dn djnh la sir dung cae phan mem tinh ddng khong on djnh (MIKEl 1, VRSAP, SAL, KODOl...) vdi cac dilu kien bien dn djnh va dirng khi ldi giai hpi tu, ehi can vai chuc budc tfnh la dat dugc kit qua.
3.2. Triedng hgp dong song phan Igch cd cii lao a giiia
Tacd:Qf=Q, + Qp
Hinh 3. Doan sdng phan laeh
va he so K cua hai laeh tir M din N la Kt va Kp, trong trudng hgp tdng quat K, ^ Kp va vi du K, >
K„
Vidu tinh thdnh phdn ngudn nude trung binh eiia mgng ludi sdngphiec tgp dnh hiedng triiu tren ca sd hi sd khuich tdn tdng hgp
Tfnh Ps tir dudi len, ta cd:
, _ 2_
P .SU) - PSN- „
347
P'^ S{p) 'SN •
K.
trong do: p 's(i), p 's(pj la trj sd ps d dau cii lao theo cac nhanh.
Tir day:
PSU - Q P S{l)+Q P S(p)
I
P.s, Ks
trong do:
K.. s(MN)
a 1
Qp
I— 7 ^ + 7^ 7f~ VO' ^t > ^P till P's(t) < p's(p) va khi hda chung tai mit Qf ^1 Qf Kp
M, de truyen nguge len, ed su khuech tan ngang manh tir dau nhanh phai qua dau nhanh trai.
Viec nay thire hien bang cac chuyen ddng ngang tir nhanh phai sang nhanh trai d dau cii lao trong cac pha trieu len nhu da nhan xet trong [7] bang quan trae.
Tinh PN ciia ngudn thugng luu ed ti le ngudn tren doan sdng la m. Tinh tir tren xudng ta CO tai N cudi cae nhanh.
m-p;N = (m-pM)Ki m-p'if.,^ (m-puJKp va sau hgp luu d dudi eii lao
m-pi,={m-p^). Q-K,. Qp, Qf ' Qf "J
^^ Kl,, = ^ K , . ^ K Qf Qf QI "
(9)
vdi Kt > Kp thi m -p',N> m - p 'M hay p'pN>p'
va d dudi eii lao cd hien tugng khuich tan manh tii' duoi nhanh phai qua duoi nhanh trai bing ddng chay ngang tir nhanh phai sang nhanh trai d day vao cac pha trilu xiilng.
348 Huynh Chiec, Bid Viit Hung
3.3. Cdch tinh cho he song kenh phirc tgp
Trude tien xuat phat tii' cac bien thugng luu de tinh nij
Tir eae nhanh bien ngudn i vdi pi= 1, tatfnh dan inj xuong dudi tai niit hgp luu vdi n nhanh vao va 1 nhanh ra, ta ed cdng thii'c (2).
i:Qr"\
y=i .K = l,2 /
Hoan thanh phep tfnh nay ta eo in; tai tat ea cac nhanh sdng eho mpi ngudn nude i.
Tinh cac thanh phan Psk tii' cae cua sdng len bang phep tinh truyen tir niit hgp luu dudi len niit hgp luu tren.
PSKdrin) = PSKfclir&i/Kclogn mil 2 mil Imp km
Tri so pks bien lay theo (5)
Tai niit hpp vdi n nhanh vao va / nhanh ra, ta cd:
UPSK-Q,
Psj = A' = l , J = l , 2 , . . . , n
Vay cong thiie tren ed nghTa la Psk eua mpi nhanh thire thu do vao liiit hgp luu la nhu nhau.
Tinh Pi eiia nguon thugng luu cho cae nhanh song Sau khi cd mpi p^k tai cac mat cat tren nhanh tatinh
P, = "h
f "
\ K=\
va hoan tat viec tinh toan 4. T h a o luan
1. Tuy dua ra vf du tfnh toan nhung thirc chit la trinh bay each giai bai toan thanh phan nguon nude trung binh mang ludi he thdng sdng kenh bao gdm:
- Bai toan thiiy lire ddng dn djnh vdi bien nguon d tren va muc nirdc trieu trung binh tai cac cira song.
Cach tfnh thanh phan ngudn nude vdi eae dieu kien: ehi sd bien ngudn i la nii = 1 va nguon bien ins = 0 cimg dieu kien bien dudi ps.
1 - - Wf
w..
Vidu tinh thdnh phdn ngudn medc trung binh cita mgng ludi sdngphiec tgp 349 dnh hiedng triiu tren ca sd hi sd khuich tdn tdng hgp
2. Thuat toan dupe xay dirng mang tinh ben virng (dn djnh) do la tfnh nij tii' tren xudng va tinh Ps va tii' do pi tir dudi len.
3. Bang vi du tfnh toan tiro'ng doi do'n gian ebo song don, khong cd hay cd thanh phan nude thai bai bao ebo thay tinh irng dung thuc te cua phuong phap tinh toan de ra.
Ngoai ra, bang phan tich truyen ngudn nude eho doan sdng phan laeh khdng chi co co' sd dl khang dinh ed chuyen ddng ngang rd ret d dau cii lao khi trieu len ma ea hien tugng tuong tir d duoi eii lao trong cae pha trieu nit.
5. Ket luan
Bang chuoi bai bao ve bai toan thanh phan ngudn nude trung binh eho mang ludi sdng phire tap viing anh hudng trieu chiing tdi trong bai bao nay da hoan tat each giai bai toan mdt khi da xac dinh dupe he sd khuech tan tdng hgp, ddng thdi cung lam rd tinh irng dung eiia nd.
Tai lieu tham khiio
[1] Tang Dire Thang (2002). Nghien cieu bdi todn cd he thdng nhieu ngudn nicdc tdc ddng - vi du icng dung cho DBSCL vd Ddng Nam Bd. Luan an Tien sT Ky thuat.
[2] Nguyin An Nien, Nguyin Anh Diic (2006). "Cac phuong phap trung binh hoa dac trung thi'iy krc va nong do chSt ciia bai toan mot chiiu va ii'ng dung viing cii'a bien". Tuyen tap kit qud Khoa hoc Cdng nghe. Vien Khoa hoc Thiiy loi Miln Nam. Nha xuSt ban Nong Nghiep.
[3] Huynh Chirc, Nguyin An Nien (2007). "Tinh toan dac trung Uung binh thanh phan nguon nuoc ciia he thing song vimg trilu" Tuyen tap cdng trinh Hdi nghi khoa hoc Ca hoc Thuy Khi todn qudc ndm 2007. Nha xuSt ban Khoa hoc Tir nhien va Cong nghe, Ha Noi, 2008.
[4] Nguyin An Nien, Tang Diic ThSng, Huynh Chiie (2007). "Vai tro ciia trilu trong phan bl thanh phSn nuoc a hai luu song" Tuyin tap cdng trinh khoa hoc - Hdi nghi Ca hoc todn qudc lan thic 8.
Tap 3, Ca hoc Thiiy khi. Nha xuk ban Bach khoa Ha Npi.
[5] Huynh Chiic, Nguyin An Nien (2008). "Vl he s6 phan tan truyin thanh phin nude vimg trilu va each giai bai toan cho mang luoi song phirc tap" Tuyen tap ket qud khoa hoc cdng nghe. Vien Khoa hoc Thiiy loi Miln Nam. Nha xuSt ban Nong nghiep.
[6] Huynh Chirc (2008). "Sir hgp li ciia he s6 khuylch tan ting hpp trong viing anh huong trieu qua vi du tinh toan thanh phin ngudn nuoc ha du he thong song D6ng Nai" Giri bao cao Hoi nghj khoa hoc Co Thiiy khi nhan kj) niem 30 nam ngay thanh lap Vien Co hoc (4/2009). '
[7] Nguyen Anh Due, Savenije H.H.G (2006). "Salt intrusion, tides and mixing in multi-channel estuaries. A case study in the Mekong Delta Vietnam". Hydrology and Earth System Sciences, No
10.
