Joumal ofScience and Technology. -N. 170(8-2015) - Military University ofScience and Technology
NGHlfiN c t r u AP L i r e CUA SONG NO Du'di NU^dC LI:N cmrdNG NGAI CO D^NG HINH ELIP TRON XOAY
Ddm Trong Thang, Vu Dinh Lgi, To Dire Thg' BU b ^ trinh bay nghien cuu ap luc cua song no du&i nu6c t^c dyng len chucmg ngai co d^g hinh elip tron xoay, xac dinh duoc ap lyc t^i cic diem khio sdt khic nhau tren chii6ng ng^i d^ng nay.
Tie khoa: Ap suat, duidng nggi, nd dudi nudc, hinh elip trdn xoay, nhiiu xg.
l . D a t v i n d e
Nghien ciiu ve no doi vdi cac nha khoa hgc tren the gidi ndi chung va Viet Nam ndi rieng luon la van de khoa hoc phuc t^p do dp khd dirge tich luy tu nhilu nganh khoa hpc t\r nhiSn khac. Cac nghien cuu no dudi nudc gin dSy vS co ban da giai quydt dugc kha nhieu van de quan trpng tren co sd phan tich ly thuyit va kit hpp vdi mgt s6 thu nghi$m thuc tl. Tuy nhien, do sdng nd dirge coi la mpt dang tai trpng dac biet, cd cudng dp va tde dp dien ra rit nhanh, cic tac dgng cua sdng nd len ddi tugng thuang la phd hOiy hojc gay biln d ^ g ldn nen cac bai toan phin nhilu 14 phi tuyln vi khd giai. M6t sl bii todn nd nlu khdng cd cac gia thilt di kim thi hau nhu khdng thi gidi dugc [4], Bai todn tie dung ciia sdng nl len chudng ngji trong mdi hirang xung quanh luon la vin dl gay can trd cho tinh toan, thilt kl lien quan din nd. Tac dung cua sdng nd dudi nudc len chudng ng»i cd hinh d ^ g nhdt dinh ndm trong khu vvc tie dgng cua nd trudc day cung da dugc nhdc den trong cac md hinh todn hpc... Tuy nhien, cdc bai todn dd gdn nhu khdng the gidi neu khdng cd cdc dilu kien di kem. Vdi syr phit triln cua miy tmh trong nhirng nam vita qua, dac bipt la cac phdn mem tinh toin da giiip cho cic bdi toin phuc t?p trudc ddy da cd ldi gidi hgp ly, nang cao dupc hi^u qud tinh todn, thilt kl nd. Tdi trpng nd dudi nudc cOng da dupc md phdng fen mdy tinh qua cdc phdn mim chuyen dung [2].
Thai gian qua, van dl biln ddo trd nen ndng bdng vdi hau hit cdc nudc cd tranh chdp trSn biSn Vipc xdy d^ng cic cong trinh phdng ngu biln ddo chiu dupc tai trgng nl hole thilt ke cic loai vu khi chiia thudc nd nhu: lupng ai, thiiy ldi, ngir ldi... dang Id vln dl cdc nudc uu tien va dly m^nh nghien cihi. Nudc ta cung cd mpt sd nghien ciiu theo djnh hudng ndy [3]. Do vay, nghien ciiu tde dyng sdng nd dudi nudc len chudng ngsi CO y nghia trong phit triln linh vuc khoa hgc vl xay dvmg cdng trinh tren biln dao vd thiet kl vu khi dudi nudc.
• Hpc vicn KTQS.
Tgp chi Khoa hgc vd Ky thudt.-So 170(8-2015) - Hgc viin KTQS
2. Cor s& ly thuyet ap lyc song nS dirdi nu&c len chvdrng ngai 2.2. Tde dung sdng no duci ntr&c len chu&ng nggi cd hinh dgng bdt ky
Khao sat song no phang lan truyen trong chdt long vd tac dung voi chudng ngai co hinh dang bat ky nhu hinh 1. Song phdng lan truyen theo phuang z, dp luc vd toe dp hat chdt long trong song tai cho truac duai dang [4]:
(1)
pA^.') = PJ\t--Mt V„(z,t)=-S!-f\t
"oPo
"oJ ° l "oJ
trong dd, ao - toe dg sdng truyen trong mdi trudng nudc (chat ldng); p^ - mat dp mdi truang nudc (chit long); P„ - ip sudt tren mat sdng xung kich; CTQ t ham sdng don vi dupc md td nhu hinh 2.
<i(0
Hinhl. Song nd dudi nu&c tde dung v&i Hinh 2. Tdi trong dan vf chu&ng nggi co hinh dgng bdt ky
Tdi trpng tac dung len toan bp vat the khi sdng bi nhieu xa se la tdng cua hai thdnh phan:
F{t)^F„{t) + F„{t) (2) trong dd, F„ (t) - tdi tigng sdng tdi; F„ (() - tai trpng gdy ra do nhieu xa. Cac hdm tren
dupc xdc dinh theo cdc cdng thuc sau:
F„(() = - f f P„(t)cosii7dS = -P,{\ fU-—]cosiiidS (3) vdi 5i la mpt phan be m|t vat the nam trong viing z < flo'-
F„ (t) = - J £ P „ {x,y,z,t)cos^dS = p„ j £ ^ c o s S r f S (4) 181
Journal ofScience and Technology.-N. 170(8-2015) - Military University ofScience and Technology
vdi P^ - qjlvc cua thanh phin sdng nhilu xa;^-thi toe dp, thda man phuong trmh sdng [4]:
a y a v a V _ i a y (5) ar^'^ay^'^az^" «„' ar=
Cdc dieu kien bien:
- Tren be mat vat thi, tde dp hat chat ldng theo phuang phip tuyln vdi bl mat vat the bang 0.
dip
hay dn
dn
- + V COS«Z=:0
=-/ t \<JA t cosnz
- Phit xa sdng d vd cung (xa vdt thi): ^—•0 khi r = yjx'+y'+z^ —• oo 2.2. Tac dgng ctia song no len vgt the dgng hinh elip trdn xoay
Gia thilt sdng lan truyin theo phuang true ddi cua vat thi, vat thi cung vd bdt dpng trong mdi trudng nudc, chilu sau chudng ng^i vd nln diy khdng inh hudng din su phan bd ip suit len chudng ngai.
Hinh 3. Song no dudi nu&c tde difng v&i chu&ng nggi Unh elip trdn xoay Til phuong trinh cic thanh phin ip luc tie dimg len ehudng ngai bit ky, ip dyng cho chudng ngai ta cd dp l\rc tic dyng len elip trdn xoay [4].
- Thanh phin do sdng tdi:
^..(n=
7ta\lJ-r) 0 khi r <2khi T>2 (9)
Tap chi Khoa hQC vd Ky thugt.-So 170(8-2015) - HQC vijn KTQS
- Thanh phan do nhieu xa:
1
U7)- ^IK'-I
A,—-A^-¥B-^C-hD khir<£.
- 4 + 4+C-E
khi«.<r <2 A^—!J^-^A,-E-M khi2<f<2+<.t.
0 khir >2+t.
trong do, doi vdi elip trdn xoay:
ft 3 C, a 2B
„ k' . [e^ FT C. =^5—arcsin.1 ,/—;— k^-l
2k 1
k-— 1 -
k^k
hi V* - l + t - -
k'-l
A^arcsin k'-}
c ^ - 1 ^
4 =
fc^arcsin (1 - ' ) 1-r + t
4 = A^arcsin^
e-
k-(l-f+4)
e-\
1 \ie+}_
( l - F ) l 1-71 4A=
it. J 3 t ( i ' -1)J 3 t ( i ' - l ) "
(i-r+zy ne
31 3 t ( t ' - l ) + 2 - ( +J.(10)
(11)
183
Joumal ofScience and Technology.-N. 170(8-2015) - Mlitary Umversity ofScience and Technology
NSu ky hi^u F^t) Id dac trung thuy dpng co dupc tu iai giai bdi toan nhilu xa d6i vcfi song don vi ob(0 thi doi voi song tai tuy y Pj{t) dac trung thiiy dpng tren (bay gio 1^
hieu la F(t)) se dupc xdc dinh theo tich phan Duamen (cong thuc Simpson). Difiu nay c6 nghta la khi bi§t duac quy luat ham song tac dung len chuang ngai, ta se xdc dinh dupc phan bo dp l^c len no [4]:
F{t) = \F^(t-T)dP,(T) (12)
0
3. Thur nghi$m so tinh ap lyc song no len chvong ng^i co dang hinh clip tron xoay
3.1. Bdi todn
Khio sit bdi todn vdi sdng tdi don vi vd sdng tdi cd quy luat tam gidc (')~^«<ix(l—) (kPa) thu dugc tir thi nghipm thvc hien trong moi trudng nudc biln d Trudng Sa [1,4].
Sd h?u dau vao:
- Toe dp tmyin sdng trpng mdi trudng thi nghipm: a,, = 1535 m/s (thu dupc tir cic thi nghipm [1]).
- Khoing thdi gian khdo sat: t = 0,003 s.
- Sd dilm thdi gian khdo sit: n = 31.
- Sdng tdi dang tam gidc c6:p^ = 1506 kPa, T= 0,0001 s.
- Bin true nhd elip trdn xoay: a = 1,128 m.
- Bin trye ldn elip trdn xoay: b = 2m.
3.2. Kh qud
Sir dvmg phin mim VBA, thilt IJp chuang trinh tinh eho ba phuong trinh (2), (9), (10) vdi cdc CO sd du lipu nhu ttgn, ta thu dupc cic kit qud thi hipn trong cic hinh 4, 5, 6 vd bing 1,2, 3.
Tgp chi Khoa hgc vdKy thugt.-Sd 170(8-2015) - Hoc vien KTQS
u c A n c k n Ehuongotai c l p tien ID
Hinh 5. Do thi phdn bd dp sudt doi vol sdng quy ludt tam gidc len chudng nggi elip tron xoay Bdng 1. Ket gud khdo sdt
doi vdi song tdi dan vi
m
00,0001 O.O002 0,0003 0,0004 0,0005 0,0006 0,0007 0,0008 0,0009 0,0010 0,0011 0.0012 0,0013 0.0014 0,0015 0,0016 0,0017 0,0018 0.0019 0.0020 0,0021 0,0022 0,0023 0,0024 0,0025 0.0026 0.0027 0.0028 0,0029 0.0030 0.0031 0.0032 0,0033 0.0034 0,0035 O.tKMd
P«(KPa) 0 0,590 1,133 1,629 2,078 2,479 2.834 3.141 3,402 3.615 3,781 3.900 3.972 3,997 3,975 3,906 3,790 3,626 3,416 3,158 3 3 2 2 I 1 0 0 0 0 0 0 0 0 0 0 0
Pn.(KPa) 0 -1,385
•0,941 -0,578 -0,289 -0,069 0,086 0,179 0,213 0,202 0,192 0,178 0,152 0,109 0,047 -0,036
•0,140
•0.260 -0,395 -0,537 -0,680 -0,813 -0,922 -0,989 -0,988
•0,881 -0.609 1,122 0,901 0,690 0 0,323 0,178 0,069 0,008 0 0
P(KPa) 0 -0,795
0,192 1.051 1.788 2,410 2,920 3.320 3.614 3.817 3,973 4.079 4,125 4.107 4,022 3,869 3,650 3,366 3,021 2,620 2,173 1,688 1,180 0,667 0,175 -0.258 -0,573 1,122 0,901 0,690 0 0,323 0,178 0,069 0,008 0 0
Bang 2. Kit qud khdo sdt doi vdi sdng tdi quy lugt tam gidc
t ( s ) 0 0,0001 0,0002 0,0003 0.0004 0,0005 0,0006 0.0007 0.0008 0,0009 0,0010 0,0011 0,0012 0,0013 0,0014 0,0015 0,0016 0,0017 0,0018 0,0019 0.0020 0,0021 0,0022 0.0023 0,0024 0.0025 0,0026 0.0027 0,0028 0,0029 0.0030 0,0031 0,0032 0,0033 0,0034 0,0035 0,0040
Pn (KP») 0 888.60 1706,28 2453,04 3128,87 3733.79 4267.78 4730,85 5123,00 5444,23 5694,53 5873,91 5982,38 6019,92 5986.53 5882.23 5707,01 5460,86 5143,79 4755,80 4296.89 3767,05 3166,30 2494,62 1752,02 938.50 54,06 0 0 0 0 0 0 0 0 0 0
P „ ( K P a ) 0 -2086,56 -1417,28 -870,70 -435,52 -104,14 129,18 269,17 320,12 303,64 289,25 268,43 229.40 164,80 70.53 -54,81 -210,13 -392,04 -594,64 -809,39 -1024,57 -1224.61 -13S8.SS -1489,49 -1487,95 -1327,52 -916,93 1690,12 1356,27 1039,74 747.03 486,24 267,48 103.68 11,88 0 0
P ( K P a >
0 -1197.96
289,00 1582,34 2693.35 3629,65 4396,96 5000.02 5443,11 5747.87 5983,78 6142,34 6311,78 6184,72 6057,06 5827,43 5496,87 5068,82 4549,15 3946,41 3272,32 2542,45 1777,45 1005,13 264,07 -389.02 -862,88 1690.12 1356,27 1039.74 747.03 486,24 267,48 103,68 11,88 0 0
185
Joumal ofScience and Technology.-N. 170(8-2015) - Military University ofScience and Technology
Nhdn xet: Tu bdng 1, bdng 2 va hinh 4, hinh 5, ta thdy rdng bilu db dp sudt t6ng hpp bdng tdng cua dp suat song nhieu xa vd song t6i. Khi song toi vua qua khoi chudng ngai elip tron xoay thi n6 se bang khong. Khi do, dp su4t len chuang ng^i chi la anh huang ciia song nhieu xa, c6 nghia la iap suat tong chinh bang dp suat nhieu x^. Dieu ndy hoan todn diing trong th^c tiln vd cdc tinh todn theo chuang trinh. Tir ket qud tinh todn bdng thir nghidm so, ta ciing xac djnh duac su phdn bo ^ l\rc theo vi tri truySn s6ng cua song xung kich doi voi chudng ngai elip tr6n xoay.
Bdng 3. Phdn bo dp luc theo vi trl truyen sdng len elip trdn xoay
P(KN) aot/b P(KN)
agt/b P(KN) s,t/b P(KN)
a«t/b 0 0 1496,95 0,7675 818,631 1,535 186,883 2.3025
-299,69 0,0768 1536,6 0,8443 636.04 1.6118 121,64 2,3793
72.298 0,1535 1554 0,921 444,66 1.6885 66.915 2,456
395,85 0,2303 1547,2 0,9978 251,45 1,7653 25,938 2,5328
673.79 0,307 1515,3 1,0745 66,063 1,842 2,971 2,6095
908,02 0,3838 1457,8 1,1513 -97,32 1,9188 0 2,6863
1099,98 0,4605 1375,14 1,228 -215,86
1,9955 0 2,763
1250,85 0,53725 1268,06 1,30475 422,814 2,07225 0 2,83975
1361,69 0,614 1138,05
1,3815 339,295 2,149
1437,93 0,69075 987,268 1.45825 260,109 2,22575 0 3,07
Do thi phan bl ip luc len chudng ngai elip trdn xoay theo hinh 6.
1700 Phan hn ap luc thpn
Hinh 6. Phdn bo dp life len be mat chu&ng ngai htnh elip Iron xoay Nhdn xet: Vdi sd lipu tinh toin d tren, khi sdng truyin dugc khoing 0,0012 giay, tuong ling vdi vi tri 1,842 m tinh tir khi mjlt sdng tic dung thi ^ lire dat gii trj c^c dai (vi tri gin den mat phing tpa dg xOy). Dilu niy cd dupc la do kit hgp tie dgng ciing chilu tit sdng tdi va nhieu xa. Qua vi tri nay, ip luc giim din vi qua khdi vit thi dp Ivrc bi tript tieu. Dilu niy phu hpp vdi thvtc tiln va cac kit qud tinh todn.
Tgp chi Khoa hgc vd Ky thugt. -Sd 170(8-2015) - Hgc viin KTQS
4. K^t lu^n
Gidi bdi todn tac d^ng ciia song nd duai nuac vai chuang ngai c6 dang hinh elip tron xoay giup cbo viec xdc dinh ban chat c a hpc cua tac dung va dp lan cua cdc hpp luc s6ng n6 len chudng ngai dang ndy dupc ro rang hon. Cdc nhd thigt k l v l no hodc xay dimg cong trinh co the can cii vdo bdi todn cu the de xdc djnh dieu kipn pha huy cho bdi toan no, dieu kien an toan cho cac cong trinh xay d\mg. Han niia, can cii vao nghien Cliu nay co the gidm thieu dupc viec phai tien hanh thi nghiem no thuc te de xdc dinh khd nang tde dung giira luang no va ket cau, giiip tilt kiem dupc chi phi vd ddm bdo an toan v l ngudi vd phuang tien khi th\rc hi6n no thuc t l .
Ngodi ra, vdi mot vdn de nghien cmi ve no, khi ket hpp cac yeu to: nghien cuu ly thuyit, nghign ciiru d ^ tren cac p h i n mem mo phdng chuyen d\ing va ket hpp no thur nghiem trong d i l u ki?n cho phep thi van de nghien cuu nd do dupc gidi quyet ddy dii, trpn ven, chinh xdc vd phdn dnh dupc cdc ^ n tai trong vdn de nghidn cuu dd.
T^i lifu tham khao
1. Bdo cdo tdng hgrp so lieu thuc nghiem no dual nudc tgi Bdo San Ca - Truang Sa. De tdi cap nhd nudc KC-09.06/11-15,2013.
2. To 0UC Thp, Trinh Tnmg Tiln. Mo phdng tdi trgng nd trong moi trudng nudc. Tuyen t j ^ cong trinh Hpi n ^ Co hpc 1^ thuat todn qudc. Tap 2: Co hpc vat ran biai d^g. Ha Npi, 6-2014.
3. Vii Dinh Lpi, To Diic Thp, Le Anh Tuan, Ph^ra Cong Nghj. Mgt sd kit qud nghien dm thuc nghidm nd trong vung nudc nong tgi khu vuc Trudng Sa. Tuyen tap cong trinh H^i nghj Ca hpc ky thuat todn qudc, Tgip 2: Co hpc vgt r3n biln dang. Hd Npi, 6-2014.
4. B. V. Zamyshlyaev, et al. Dyruimic loads in underwata- aq)losion. Washington, D.C, 2-1973.
Ng^ nhgn bdi: 17 thdng 6 ndm 2015 Ngdy nhgn bdn sda ldn cudi: 24 thdng 7 ndm 2015
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