NGHIEN cuu-TRAO D 6 |
NGHIEN CUU PHLfaNG PHAP XAY DU'NG MO HINH TAU 3D TRONG T 6 | U'U HOA DU'ONG HJNH TAU
STUDY OF THE METHOD FOR CREATING 3D MODEL ON THE OPTIMIZING OF SHIP FORMS
Nguyen Vu Ha', Nguyen Qu6c Bao^ Trin Gia Thai^
'Trung tam Dang kiem Tau ca
•^•^Trudng Dai hpc Nha Trang TOM T A T
Bdi bdo trinh bdy nghien cuti xdy dung mo hinh tdu 3D & dinh dgng file. STL de co the su dung ket hpp phuomg phdp dpng luc hpc lieu chdt CFD tinh sue cdn vd phuang phdp bien doi hinh hpc duang hinh tdu cua Lackenby. Nghien cicu ndy la mpt phdn trong nghien cicu ieng dung phuang phdp CFD vd Lackenby de xdc dinh vd bien dot du&ng hinh tdu ban ddu den du&ng hinh tdu toi uu CO vi tri hodnh do tdm noi tuang ung v&i sue cdn tdu la nho nhdt.
Tix khoa: CFD, sue cdn, toi uv., Lackenby, hodnh dp tdm noi.
ABSTRACT
This article presents the study of creating a 3D ship model in. STL file so that it can be used in combination computationalfiuid dynamics (CFD) for the ship resistance prediction and Lackenby's method for the geometric transform of ship lines. This study is a part of study of using CFD and Lackenby's method to determine and geometric transform the original ship's lines to the optimal one having the new longitudinal position of center of buoyancy with the minimum resistance.
Keywords: CFD, resistance, optimal, Lackenby, longitudinal center of buoyancy. "^
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NGHIEN c u u - T R A O DOI
l.DATVANDE
Tdi uu hda dudng hinh la bai toan cd vai yd va y nghia quan ypng trong viec nang cao hieu qua kinh tl - ky thuat va miic do an toan ciia tau thilt kl. Cho din hien nay da cd nhieu cdng trinh nghien cuu tdi uu dudng hinh tau va hiu hit diu dua tten ham myc tieu sire can, cung vdi cac thuat toan tdi uu da biit nhu cua Han (2012), Zakerdoost (2013) hay Scamardella (2014)... Mdt trong cac phucmg phap hieu qua la sir dung phuong phap Lackenby [2] de bien ddi dudng hinh tau ban dau din dudng hinh tau tdi uu cd hoanh dd tam ndi tuong img sire can nhd nhit tinh bing phuang phap sd da biet [3].
Phuang phap nay dan gian va cd do chinh xac cao nhung lai it dugc ap dung. Nguyen nhan do khi tinh sue can bang cac phucmg phap sd nhu phucmg phap tinh ddng luc hgc luu chat CFD (Computational Fluid Dynamics) deu dimg md hinh tau 3D d dang mat de tinh sire can tau nen khdng the ket hgp vdi phucmg phap Lackenby de di chuyen cac sudn khi bien ddi dudng hinh tau. Vi vay, cho den hien nay van chua cd nghien ciiu tdi uu hda dudng hinh tau dua tren ca sd ket hgp phuang phap CFD va phucmg phap Lackenby da neu. Chi cd phuang phap Panel quan ly vi tri va tpa dp cac diem tren cac sudn tau trong panel nen rat thich hgp khi ket hgp phuang phap nay (Krishana, 2009).
Tuy nhien, phucmg phap Panel chi tinh cho ddng the, khdng cd do nhdt nen hau nhu khdng cdn dugc ap dung trong udc tinh sue can tau hien nay [1]. Loat bai bao nay se trinh bay ket qua nghien ciru tdi uu hda dudng hinh tau tren CO sd ket hgp phucmg phap CFD va Lackenby nhd ky thuat xay dung md hinh tau 3D d dang mat de sir dung phuang phap CFD thdng qua viec quan ly tpa dp cac diem tren dudng sudn de su dung phuang phap Lackenby.
2. PHl/ONG PHAP NGHIEN ClTU Ve mat phuang phap, md hinh sd 3D
dung tinh toan CFD thudng dugc chuan hi d dinh dang file.STL (Stereo Lithography) md ta bl mat ddi tugng bing each ndi lan lugt cac dilm nim tren be mat ddi higng de tao thanh mgt loat mat tam giac phu len toan bg be mat md hinh hinh hgc dang tinh [4].^ File. STL rit phd biln hien nay, nen hau het cac phin mim CAD thdng dyng hien nay nhu Autocad, Rhinoceros... deu cho phep tao dinh dang file nay. Tuy nhien, nhu da nhan xet, viec tao mo hinh hinh hgc 3D cua tau tinh toan theo dinh dang file.STL trong cac phin mdm CAD theo each lam bien nay khdng cho phep dilu chinh vi bri va tga dp cua cac diem tren dudng sudn tau, do dd khdng ap dyng dugc phuang phap chuyin ddi dudng hinh Lackenby. Vdi muc tieu tao ludi chia cac mat tam giac theo dung dinh dang file STL de sao cho vira cd the tinh theo phuang phap CFD, vua cd the dieu chinh vi tri va tpa dp cac diem tren cac sudn tau de tinh theo phucmg phap Lackenby, thay vi ndi diem bat ky de tao cac tam giac be mat nhu each lam hien nay, chung tdi dinh hinh tao va sap xep cac tam giac phii len be mat tau bang each noi lan lugt hai diem nam tren ciing sudn vdi mpt diem d tren sudn ke tiep. De thuan tien khi tinh, chiing tdi cd viet chuang trinh ghi lai tpa dp cac diem tren be mat md hinh tau sang Excel va sap xep cac diem tren cac sudn de tao cac tara giac be mat, sau dd tao dinh dang va luu file nhi phan (ASCII) STL.
3. K £ T Q U A NGHIEN CLf*U
Sir dung mau tau tinh toan la tau ca vo go Viet Nam ky hieu M1317. Qua trinh xay dung md hinh tau nay theo dinh dang file STL nhu sau:
Bu'd'c 1. Xay dung md hinh sd 3D cua tau tinh toan:
Dyng md hinh tau 3D bing phin mem, d day la phin mim thilt kd tau AutoShip va
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NGHIEN CLfU - TRAO OOl
dimg cong cu cua phan mSm xuat toa do giao diem ciia cac sudn vol cac duong nucfc qua Excel 6 dinh dang bang tpa do duong hinh da biet. Hinh 1 la hinh anh mo hinh s6 va bang toa dp trong Excel ciia giao diim giiia 122 sucm tir lai den mui va 50 duong nuoc tir day toi boong tau dang tinh, voi luu y cac giao diSm nay phai nam tren cimg duong sucm va duong nuoc di dinh dang file mo hinh. STL va co thi hieu chinh cac sudn va duong nuac nham kit hgfp phuong phap tinh sire can bjng CFD va thuat toan Lackenby.
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Hinh 1. Md hinh sd vd bdng tpa do du&ng hinh tdu M1S17A.
Bud-c 2. Sap xep vi tri cac diem tr§n md hinh tau theo dinh dang file STL:
Ve nguyen tac, de tao ra dugc mdt tam giac diem trong file.STL da neu, can cd ba diem, vdi hai diem nam tren mdt sudn, diem cdn lai nam tren sudn tiep theo va ba diem phai nim gin nhau nhit cd the dl dam bao dp chinh xac. Do do, tir bang tpa dp dudng binh trong Excel d budc 1, lap cdng thiic tinh ndi timg cap
ba diem thda tinh chat tren vdi nhau theo thii ty tir lai den miii de tao tap hgp cac tam giac dilm phu len bl mat vd tau nhu md ta d hinh 2.
A, B, C - Toa dp cac diem a siron 1;
a, b, c -Toa do cac diem o sucm 2.
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l.DATVANDE
Tdi uu hda dudng hinh la bai toan cd vai trd va y nghia quan trpng ttong viec nang cao hieu qua kinh tl - ky thuat va mite dp an toan cua tau thilt ke. Cho din hien nay da cd nhieu cdng trinh nghien ciiu tdi uu dudng hinh tau va hiu hit diu dya tren bam muc tieu siie can, cung vdi cac thuat toan tdi uu da biet nhu cua Han (2012), Zakerdoost (2013) hay Scamardella (2014)... Mdt trong cac phuong phap hieu qua la sir dyng phuang phap Lackenby [2] de bien ddi dudng hinh tau ban diu den dudng hinh tau toi uu cd hoanh dp tam ndi tuong iing siic can nhd nhat tinh bang phuong phap sd da biet [3].
Phuong phap nay don gian va cd dp chinh xac cao nhung lai it dugc ap dung. Nguyen nhan do khi tinh sue can bang cac phucmg phap sd nhu phuang phap tinh ddng lyc bgc luu chat CFD (Computational Fluid Dynamics) deu dimg md hinh tau 3D d dang mat de tinh sue can tau nen khdng the ket hpp vdi phuang phap Lackenby de di chuyen cac sudn khi bien ddi dudng hinh tau. Vi vay, cho den hien nay van chua cd nghien cuu tdi uu hda dudng hinh tau dua tren ca sd ket hop phuong phap CFD va phuong phap Lackenby da neu. Chi cd phuang phap Panel quan ly vi tri va tpa dp cac diem tren cac sudn tau trong panel nen rat thich hgp khi ket hgp phuang phap nay (Krishana, 2009).
Tuy nhien, phuang phap Panel chi tinh cbo ddng the, khdng cd do nhdt nen hau nhu khdng cdn dugc ap dung trong udc tinh sue can tau hien nay [1]. Loat bai bao nay se trinh bay ket qua nghien cuu tdi uu hda dudng hinh tau tren ca sd ket hgp phuong phap CFD va Lackenby nhd ky thuat xay dyng md hinh tau 3D d dang mat de su dung phuang phap CFD thong qua viec quan ly tpa dp cac diem fren dudng sudn de su dung phuang phap Lackenby.
2. PHU'ONG PHAP NGHIEN CUU Vl mat phucmg phap, md hinh sd 3D
dung tinh toan CFD thudng dugc chuan hi 6 dinh dang file.STL (Stereo Lithography) mo ta bl mat ddi tugng bang each ndi lan lugt cac dilm nim tren be mat ddi tupng de tao thanh mdt loat mat tam giac phu len toan bd be mat md hinh hinh hpc dang tinh [4]. File. STL rit phd bien hien nay, nen hau het cac phin mim CAD thdng dung hien nay nhu Autocad, Rhinoceros... deu cho phep tao dinh dang file nay. Tuy nhien, nhu da nhan xet, viec tao m6 hinh hinh hgc 3D ctia tau tinh toan theo djnh dang file.STL trong cac phan mem CAD theo each lam hien nay khdng cho phep dieu chinh vi tri va tpa do cua cac diem tren dudng sudn tau, do dd khdng ap dung dugc phuong phap chuyin ddi dudng hinh Lackenby. Vdi muc tieu tao ludi chia cac mat tam giac theo dung djnh dang file STL de sao cho vira cd the tinh theo phuang phap CFD, vua cd the dieu chinh vi tri va tpa dp cac diem tren cac sudn tau de tinh theo phuong phap Lackenby, thay vi ndi diem bat ky de tao cac tam giac be mat nhu each lam hien nay, chiing tdi dinh hinh tao va sap xep cac tam giac phu len be mat tau bang each noi lan lugt hai diem nam tren cung sudn vdi mot diem d tren sudn ke tiep. De thuan tien khi tinh, chiing tdi cd viet chuang trinh ghi lai tpa do cac diem tren be mat md hinh tau sang Excel va sap xep cac diem tren cac sudn de tao cac tam giac be mat, sau do tao dinh dang va luu file nhj phan (ASCII) STL.
3. KET QUA NGHIEN CUtJ
Sir dung miu tau tinh toan la tau ca vo gd Viet Nam ky hieu Ml317. Qua yinh xay dyng md hinh tau nay theo dinh dang file STL nhu sau:
Budc 1. Xay dmig mo hinh sd 3D cua tau tinh toan:
Dung md hinh tau 3D bang phan mem, d day la phan mim thilt kl tau AutoShip va
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TAP CHf CO KHI VIET NAM, Sd 1+2 nam 2019 www.cokhivietnam.vn
NGHIEN CIJU-TRAO D O I
dimg cdng cu ciia phan mem xuat tga do giao diem cua cac sudn vdi cac dudng nude qua Excel d dinh dang bang tpa do dudng hinh da biet. Hinh 1 la hinh anh md hinh sd va bang tpa do trong Excel ciia giao diem giiia 122 sudn tir lai den mui va 50 dudng nude tir day tdi boong tau dang tinh, vdi luu y cac giao diem nay phai nam tren cimg dudng sudn va dudng nude de dinh dang file md binb. STL va cd the hieu chinh cac sudn va dudng nude nham ket hgp phuong phap tinh siic can bang CFD va thuat toan Lackenby.
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Hinh 1. Mo hinh so vd bdng tpa dp duang hinh tdu Ml317A.
Budc 2. Sap xdp vi tri cac dilm tren mo hinh tau theo dinh dang file STL:
Vl nguyen tic, dl tao ra dugc mdt tam giac dilm trong file.STL da neu, cin cd ba dilm, vdi hai dilm nam tren mdt sudn, diem cdn lai nim tren sudn tilp theo va ba diem phai nim gin nhau nhit cd the de dara bao do chinh xac. Do dd, tir bang tga dp dudng hinh trong Excel d budc 1, lap cdng thtic tinh ndi firag cap
ba diem thda tinh chat tren vdi nhau theo thii tu tir lai den miii de tao tap hgp cac tam giac diem phu len be mat vd tau nhu md ta d hinh 2,
A, B, C - Toa do cac diem a siron 1;
a,b,c -Toa do cac diem o suon 2.
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NGHIEN c i i u - T R A O D 6 I
Hinh 3, bieu dien cac tam giac diem tren cac dudng sudn va ludi chia tam giac ciia file STL hinh thanh tir cac tam giac diem tren be mat vd tau.
(a) Cdc tam gidc diim (b) Lu&i chia tam gidc Hinh 3. Cdc tam gidc diim vd lu&i chia trong file STL.
Bu'd'c 3. Tao file STL tir cac tpa do giao dilm:
Viet doan code chuong trinh chay cac vdng lap de tao cac tam giac diem phu len hen be mat vd tau tir tpa do cua cac giao diem da xac dinh d budc 2, vdi mgt vdng lap se cd dugc mdt tam giac gdm 03 diem, do do trong file.
STL cd bao nhieu tam giac diem thi se cd b§y nhieu vdng lap d dang nhu tren. Doan code tren dugc dinh dang tren phan mem Excel, h-ong dd tga do ba dinh tam giac trong cac d dinh (vertex) d phan Output se dugc lay tii bang tpa do giao diem giiia cac dudng sudn va dudng nude d phan Input (hinh 4).
Hinh 4. Cdng thiec bdng tri so STL lap bang Excel.
Buffc 4. Tao file STL cua be mat vo tau:
Copy van ban tren trong Excel va dan sang file.txt de luu md hinh tau d dinh dang file .STL nhu md ta tren hinh 5.
Hinh 5. Mo hinh 3D cua tdu Ml 317A xay dung & dinh dang file STL.
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4. KET LUAN
Ket qua nghien ciru cho thay, md hinh 3D tau tinh toan d dang file STL hoan toan dap ung dugc myc tieu de ra khi cd the tinh siic can bang CFD, ddng thai do cac tam giac dilm phii be mat vd tau dugc ldng ghep vdi tga do cac sudn nen ciing cd the sut dung phucmg phap Lackenby de thay ddi vi tri va tga do cua cac dudng sudn tau, tir dd thay ddi dudng binh tau ban dau den dudng hinh cua tau tdi uu nhu se dugc trinh bay trong bai bao tiep theo. • Ngay nhan bai: 29/01/2019
Ngay phan bien: 15/02/2019
Tai lieu t h a m k h a o :
[ 1 ], Krishana M. (2009); Hull Shape Optimization for Wave Resistance Using Panel Method,
University of New Orleans.
[2]. Lackenby. H (1950); On the Systematic Geometrical Variation of Ship Forms, RINA Transactions, Vol.92.
[3]. Trin Gia Thai (2014); Ly thuyet CFD vd img dung trong ngdnh Ky thudt tdu thuy, Tai lieu giang day Sau dai hpc, Tnrdng Dai hpc Nha Trang.
[4]. http://en.wikipedia.org/wiki/STL], 23 August 2016.
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