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RISS 인기검색어
- 검색키워드
- 저자 : Ngoc T. B. Hoang (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Ngoc T. B. Hoang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.10
The evaluation of the variation in aerodynamic load on a wing under the effect of elastic deformations requires solving the problem of wing deformation when wings are subjected to distributed aerodynamic load. This paper presents the calculation of coupling the aeroelastic system for 3D wings. The aerodynamic problem was solved by the doublet–source method for 3D wings, with wing thickness considered. The problem of elastic deformation was solved by the finite element method for hollow 3D wings, with beams arranged inside. Results concerning aerodynamic load on the wing were considered input parameters for the calculation concerning the problem of wing deformation, and those about the deformed wing geometry were deemed input parameters for the calculation regarding the problem of wing aerodynamics for the second calculation. The calculations concerning these problems were repeated until the wing twist angle converged. Analyses and comparisons were performed on the distributions of aerodynamic loads on the rigid and deformed wings to examine the change of the aerodynamic load depending on the structure (aerodynamic loads being functions of the external geometry of the wing, the incidence angle, and the velocity at infinity are solutions of the pure aerodynamic problem). Results regarding wing twists and stress distributions for hollow wings with and without beams inside were presented to assess the cause of changes in aerodynamic load and wing static durability. Aeroelastic calculations were formulated with different velocities at infinity to indicate the need for a suitable structural solution when the aerodynamic load is expected to reach a high value.
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Experimental and numerical studies of wingtip and downwash effects on horizontal tail
Ngoc T. B. Hoang,Binh V. Bui 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.2
Studying wing downwash, which is caused by the wingtip effect, and its influence on horizontal tail is important for aircraft design. In this work, wing downwash was investigated using experimental and numerical methods. Sets of main wings and horizontal tails were fixed in a tunnel test chamber. For determining the wingtip effect and the wing downwash affecting the horizontal tail, experiments were performed, in which the pressure distributions near the main wingtip and on the upper and lower surfaces of the tail were measured. These experimental models were used in numerical calculations by the solving of differential equations for viscous flows and use of a singularity method for potential flows. The singularity method can be applied to determine the wing lift, as indicated by comparisons between the experimental and numerical results of the pressure distribution on the wing. Moreover, the wingtip and wing downwash effects influencing the horizontal tail should be determined with use of experimental and numerical methods that solve differential equations of viscous flow. In addition to the results regarding the pressure distributions near the main wing and on the horizontal tail, the longitudinal velocity, downwash velocity, and downwash angle distributions in the main wing wake were analyzed. We also investigated the kinetic parameters of the flow in mixed zones between the main wing downwash and the tail upwash.
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Ngoc T. B. Hoang,Binh V. Bui 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6
The calculation of aerodynamic characteristics of a wing is the basic problem for aerodynamic design of aircraft. Wing aerodynamics can be determined experimentally and numerically. The method of fixing the wing in the test chamber of wind tunnel is related to disturbance of flow through the wing. When the wing is entirely fixed in the test chamber, the disturbance is usually caused by the sting connecting the wing to the test chamber. The experiments in this paper fixed the wing by clamping to the wind tunnel wall at the wing symmetry surface (root section). With this wing fixation, it was possible to take advantage of the wingspan twice, but to obtain the 3D wing experiment results, it was necessary to evaluate the impact of the wind tunnel wall effect. As for aircrafts, the aerodynamic force of the aircraft’s wing will have certain difference than that of the wing alone. The intersection region between the wind tunnel wall and wing root (for the experiment), as well as between the fuselage and wing root have complex interactions of boundary layers, in particular separation phenomena in the boundary layers. By solving the differential equation for viscous flows, it was possible to visualize the picture of streamlines and flow separations in this interference region and the aerodynamic characteristics of the wing. The singularity method was also used to compare results within its application range. The aerodynamic coefficients in the two cases with and without interference were analyzed. Complex interactions in the interference region could alter the predicted aerodynamic force calculated for the wing alone, which should be estimated. Very strong separations in the wing-fuselage interference region at large angles of attack turned into vortices at the rear impacting on the horizontal tail aerodynamics that is related to the balance problem of the aircraft.
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Numerical investigations of solidification around a circular cylinder under forced convection
Truong V. Vu,Anh V. Truong,Ngoc T. B. Hoang,Duong K. Tran 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.11
We present numerical investigations of solidification around a cooled circular cylinder in the presence of forced convection. The numerical method is based on the front-tracking/finite difference and interpolation techniques. The solidification interface is represented by connected elements that move on a fixed, rectangular grid. The no-slip and Dirichlet temperature boundary conditions are imposed by the linear interpolation. The interpolation method was first validated through comparisons of the present results with some other numerical results for flow in an annulus, flow in an enclose with a conduction solid body and flow over a heated cylinder. We then used the method to investigate the solidification process around a cold cylinder by varying various parameters such as the Reynolds number Re, the Prandtl number Pr, the Stefan number, the thermal conductivity ratio k sl , the non-dimensional temperature of the introduced liquid q 0 , and the solid-to-liquid density ratio r sl . Numerical results indicate that an increase in any of Re, Pr and q 0 results in a decrease in the area of the solidification region around the cylinder. In contrast, increasing k sl increases the region of the solid phase. Investigation on St and r slreveals that the solidification rate increases with an increase in St or a decrease in r sl . However, St and r sl have a minor effect on the final product of the solidification process.
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