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Проектирование и конструкция судов / Ship Design and Construction
Trieu Van Nguyen, Yoshiho Ikeda
TRIEU VAN NGUYEN, Ph.D. candidate, Department of Marine System Engineering, Graduate School of Engineering, Osaka Prefecture University, Osaka 599-8531, Japan, e-mail: dx102001 @edu.osakafu-u.ac.jp
YOSHIHO IKEDA, Professor, Dean of Graduate School of Engineering, Osaka Prefecture University, Osaka 599-8531, Japan, e-mail: [email protected]
A development of high lift rudder sections
In this paper, the hydrodynamics characteristics of several types of high lift rudder sections are numerically investigated. These include: fishtail rudder, wedge tail rudder and flat plate at the tail shape. A computational fluid dynamics commercial code, ANSYS FLUENT, is used to calculate the forces and moments. The numerical results show that all developed rudder sections give higher lift and maximum lift than the NACA 0024 rudder section. However, they accompany higher drag force. The small size of tail shape can improve the lift while the drag does not increase significantly. The results can be applied for the 3-D rudder models in further development of marine high lift performance rudders.
Key words: numerical method, marine rudder, lift, drag, fishtail, wedge tail, flat plate.
Introduction
For better maneuverability or a smaller rudder of ships, rudder with higher lift and smaller drag have been sought. The way to increase lift force of lift surfaces were comprehensively introduced in the text books written by Hoerner and Borst [3] and by Molland and Turnock [5].
Recently, Nguyen and Ikeda [7-10] numerical studied on hydrodynamic characteristics of different high lift rudder sections includes the fishtail rudder, wedge tail, and trailing edge with a flat plate by using a CFD commercial code, ANSYS FLUENT. Before applying CFD method, the validation has been done for NACA 0012 case by comparing the simulation data with the other experimental and numerical data [1, 2, 4, 6]. The numerical results showed that the modification of rudder cross-section can significantly improve lift and maximum lift.
In this paper, the hydrodynamic characteristics of different high lift rudder sections are compared and validated in order to select the appropriate type and size of rudder section for the further development of marine high lift rudders.
High lift rudder sections
Is this section, the three different types of high lift rudder sections are introduced.
(1) Fishtail rudder
The fishtail sections are defined as follows:
The maximum lift is located at 20% of the chord length (c) from the head, taper to 80%, concave to 90% and flare to 100%.
The profiles of the developed fishtail rudder sections and NACA 0024 are shown in Fig. 1.
(2) Wedge tail rudder
©Trieu Van Nguyen, Yoshiho Ikeda, 2015
New rudder section with a wedge at the tail is created on the base of the NACA 0024 as shown in Fig. 2.
(3) Trailing edge with flat plate
A small flat plate is vertically attached at the trailing edge of the NACA 0024 airfoil. The developed rudder sections is shown in Fig. 3.
The rudder sections and their parameters are listed in Table 1.
Fig. 1. Fishtail shape section with NACA0024 Fig. 2. Rudder cross section with
Where c is the chord length, t_max is the maximum a wedge tail
thickness, h is the wedge size
Fig. 3. Trailing edge with flat plate
Table 1
Ruddersections parameters
Name Maximum thickness Trailing edge thickness
NACA 0024 0
Fishtail 3.0 (FT 3.0) 24%c
Wedge Tail 3.0 (WT 3.0) 3.0%c
Flat Plate Tail (FPT 3.0)
Computational fluid dynamics (CFD)
A CFD commercial code, ANSYS FLUENT, is used to calculate the forces and moments of rudder sections. The k-omega SST turbulence model is applied.
The physical and boundary conditions for simulation are listed in Tables 2 and 3.
Table 2
Physical conditions for CFD calculation
Parameter Value Unit
Fluid Water
Density 998.2 kg/m3
Viscosity 0.001003 kg/m-s
Velocity 6 m/s
Reynolds number 6,000,000
Table 3
Boundary conditions for CFD calculation
Boundary Type
Left, Upper, Lower edges Velocity inlet
Right edge Pressure outlet
Rudder sections No-slip wall
The unstructured mesh with near wall resolution around the rudder sections can be seen as Figs. 4-7.
Fig. 4. Computational mesh
Fig. 5. Mesh near the trailing edge of fishtail
Fig. 6. Mesh near the trailing edge of wedge tail
Fig. 7. Mesh near the trailing edge of flat plate tail
CFD validation
Validation of CFD calculation are carried out. NACA 0012 is selected as the cross section for the validation and the calculated results are compared with the experimental and computed data show by Gregory [2], Ladson [4], and CFL3D [6].
Figs. 8 and 9 show the comparison of the lift and the drag coefficients with other data. As shown in Fig. 8, the calculated result of the lift shows a good agreement with Ladson and CFL3D data up to stall angle and can give an accurate maximum lift. However, after stall the calculated lift coefficient is higher than that of Ladson's experimental data. This is consistent with the conclusion by Douvi [1] and may be caused by the turbulent model, k-omega SST model, in the present computation.
The calculated drag is also in good agreement with other data up to stall angle as shown in Fig.
9.
The present validation demonstrates that the present CFD calculations give us accurate lift and drag in the region of angle of attack below stall angle of the foil.
ВЕСТНИК ИНЖЕНЕРНОЙ ШКОЛЫ ДВФУ. 2015. № 1 (22) / FEFU: SCHOOL OF ENGINEERING BULLETIN. 2015. N 1/22
Fig. 10 shows the comparison of pressure coefficients on face and back surfaces of NACA 0012 foil between the present CFD results and Gregory data at 15 degrees of angle of attack. The agreement of them are fairly good.
The calculated results of the skin friction coefficient are shown in Fig. 11 with other calculated results, CFL3D. The agreement is fairly good except both ends of the tails, leading and tail ends. This fact suggests that the present calculations can accurately calculate the boundary layer around the airfoil.
и 1,80 1,60 1,40 1,20 1,00 0,80 0,60 0,40 0,20 0,00
N ACA0012-CI
♦ Fluent BLadson A CFL3D
5 10
AoA (deg.)
15
20
Fig. 8. Comparison of the present CFD results and other data for lift coefficients of NACA 0012
C
0,50
0,45
0,40
0,35
0,30
0,25
0,20
0,15
0,10
0,05
0,00 A 0
NACA0012-Cd
♦ Fluent ■ Ladson a CFL3D
10
AoA (deg.)
15
20
Fig. 9. Comparison of the present CFD results and other data for drag coefficients of NACA 0012
NACA0012-Cp
NACA0012-Cf
2 1 0 -011 -2 -3 -4 -5 -6 -7
1,6 0,7 0,80,9 1 1,1
Fig. 10. Longitudinal distribution of pressure coefficient on face and back surface of NACA 0012 at 15 deg. of angle of attack
0,06
♦ Fluent k-w SST 0,05 * ■ CFL3D
0,04
C
0,03 0,02 0,01
Fig. 11. Longitudinal distribution of calculated skin friction coefficient on surfaces of NACA 0012 at 15 deg. of angle of attack
5
0
0
Numerical results
This section present about the numerical results of three developed rudder sections in comparison with the NACA 0024 foil section. (1) Lift and drag forces
[17] vestnikis.dvfu.ru/eng
The hydrodynamic force coefficients of the developed rudder sections are compared with those of the NACA 0024 airfoil. The comparison is shown in Fig. 12.
All of the modified rudder sections give higher lift and maximum lift than that of the NACA 0024 at the angle of attack below 15 degrees. The rudder section with a small flat plate tail generates much higher maximum lift than others. It should be noted that stall angle depends on the tail shape.
The drag coefficients of them are presented in Fig. 13. At the angle of attack below 10 degrees, the flat plate tail and the wedge tail one give a little larger drag than that of the NACA 0024 while the fishtail one gives much larger than others.
NACA 0024 WT 3.0
FPT 3.0 FT 3.0
1,80 1,60 1,40 1,20 1,00 û 0,80 0,60 0,40 0,20 0,00 -0,20
10 20 AoA[deg.]
30
Fig. 12. Lift coefficients of different tail shape sections
Fig. 13. Drag coefficients of different tail shape sections
NACA 0024 WT 3.0
FPT 3.0 FT 3.0
60 50 40 30 20 10 0 -10
10 20 AoA[deg.]
30
Fig.14. Lift to Drag ratio of different tail shape sections
Fig. 15. Pressure distribution at 15 deg. angle of attack Top: Left: NACA 0024, Right: Flat plate tail Bottom: Left: Wedge tail, Right: Fishtail
0
0
The lift to drag ratios of them are shown in Fig. 14. The fat plate tail rudder section and the wedge tail one give higher maximum lift/drag than the NACA 0024 while the fishtail gives smaller. The flat plate tail rudder section gives the better lift/drag characteristic than the wedge tail and fishtail ones. (2) Flow visualizations
ВЕСТНИК ИНЖЕНЕРНОЙ ШКОЛЫ ДВФУ. 2015. № 1 (22) / FEFU: SCHOOL OF ENGINEERING BULLETIN. 2015. N 1/22
The pressure distribution of four rudder sections at 15 degrees of angle of attack are shown in Fig. 15. The high pressure acts on the face side near the trailing edge because of the flat plate at the tail. The high pressure increase the lift.
Dead water
If?
Dead water
A
Dead water
4
Dead water
Dead water
Dead water
Dead water
Fig. 16. Velocity distribution at 0 deg. of angle of attack
Fig. 17. Velocity distribution at 15 deg. of angle of attack
-4,
Vortices
vui Lices
&
Vortices
A
Vortices
Fig. 18. Streamlines at zero degree of angle of attack Fig. 19. Streamlines at 15 degrees of angle of attack
Figs. 16 and 17 show the velocity distribution of the four rudder sections at zero and 15 degrees of angle of attack. At zero degree of angle of attack, the dead water behind the flat plate tail increases the drag force but the dead water in front of the tail may cancel the drag force. It may be the reason why the drag force is unexpectedly small. At 15 degrees of angle of attack, dead water of the fishtail is larger than those of the other tails. The larger dead water may cause the larger drag force of the fishtail rudder shown in Fig. 17.
Figs. 18 and 19 show the streamline distribution of the rudder sections. At zero angle of attack, the vortices develop in front of and behind the flat plate tail.
Conclusion
In this paper, the hydrodynamic characteristics of the three high lift rudder sections are investigated and compared with the NACA 0024 one. The following conclusions are obtained:
(1) The rudder sections with a fishtail, wedge tail and flat plate increase lift and maximum lift by the high pressure before the trailing edge on the face surface.
(2) The developed rudder sections accompany higher drag force due to the dead water behind the trailing edges.
(3) Appropriate size of the trailing edge can increases the lift while the drag does not increase so much.
(4) At a maximum thickness of 24% and trailing edge thickness of 3% (based on the chord length), the rudder section with a small fat plate tail is superior to the fishtail and the wedge tail ones from the high lift and small drag point of view.
(5) The results of this study can be applied for further development of high lift rudders.
REFERENCES
1. Douvi C.E., Tsavalos I. Athanasios and Margaris P. Dionissios. Evaluation of the turbulence models for the simulation of the flow over a National Advisory Committee for Aeronautics (NASA) 0012 airfoil. J. of Mechanical Engineering Research. 2012;4(3): 100-111.
2. Gregory N., O'Reilly C.L. Low-speed aerodynamic characteristics of NACA 0012 aerofoil sections, including the effects of upper-surface roughness simulation Hoar Frost. Ministry of defence, Aeronautical Research Council, London: her majesty's stationery office, 1973.
3. Hoerner S.F., Borst H.V. Fluid dynamic lift. 1975.
4. Ladson C.L. Effect of independent variation of March and Reynolds numbers on the low-speed aerodynamic characteristics of the NACA 0012 airfoil section. NASA TM 4074. 1988.
5. Molland A.F., Turnock S.R. Marine rudder and control surface. 2007.
6. NASA LaRC. Turbulence modeling resource-2D NACA 0012 airfoil validation case.
7. Nguyen V.T., Ikeda Y. Development of fishtail rudder sections with higher maximum lift coefficients. Proceeding of the 24th International Ocean and Polar Engineering Conference (ISOPE). 2014;4:940-947.
8. Nguyen V.T., Ikeda Y. Hydrodynamics characteristic of rudder sections with high lift force. Proceeding of the Japan Society of Naval Architects and Ocean Engineering (JASNAOE). 2013;17:121-124.
9. Nguyen V.T., Ikeda Y. Hydrodynamics characteristic of rudder sections with high lift force. Part 2: The wedge tail shape. Proceeding of JASNAOE. 2014;18:171-174.
10. Nguyen V.T., Ikeda Y. Hydrodynamics characteristic of rudder sections with high lift force. Part 3: The trailing edge with flat plate. Proceeding of JASNAOE. 2014;19:403-406.
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ВЕСТНИК ИНЖЕНЕРНОЙ ШКОЛЫ ДВФУ. 2015. № 1 (22) Проектирование и конструкция судов
Чьеу Ван Нгуен, Йошико Икеда
ЧЬЕУ ВАН НГУЕН - аспирант, кафедра морских инженерных сооружений, Высшая техническая школа, Университет префектуры Осака. Осака, Япония, 599-8531, e-mail: [email protected] ЙОШИКО ИКЕДА - профессор, декан Высшей школы инженерии, Университет префектуры Осака. Осака, Япония, 599-8531, e-mail: [email protected]
Проектирование судовых рулей с высокой подъемной силой
Рассматриваются вопросы численного моделирования профилей, обладающих повышенной подъемной силой и используемых при проектировании судовых рулей. Исследовались такие типы профилей, как «хвост рыбы» (классический вариант), профиль в форме хвоста рыбы с клином в районе выходящей кромки, а также профиль с плоской пластиной на конце выходящей кромки, расположенной перпендикулярно набегающему потоку. Для вычисления гидродинамических сил и моментов использовался программный продукт ANSYS FLUENT. Результаты численных экспериментов показали, что предлагаемые профили судовых рулей обладают большей подъемной силой по сравнению с профилем NACA 0024. Однако увеличение подъемной силы сопровождается увеличением силы лобового сопротивления. Результаты расчетов показывают, что в определенных пределах предлагаемые конструктивные решения в районе выходящей кромки профиля пера руля позволяют увеличить подъемную силу без значительного увеличения силы лобового сопротивления. Результаты исследования планируется протестировать на реальных моделях судовых рулей, обладающих повышенной подъемной силой.
Ключевые слова: численное моделирование, перо руля, подъемная сила, сопротивление, плавник, клиновидный плавник, плоская пластина.
