• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.491-498
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• 2003

In this paper, dynamic characteristics of an epicyclic gear train considering Coriolis effect have been studied. High speed transmissions such as in an aircraft engines will be strongly influenced by Coriolis effect. Gear meshes were modelled as springs and dampers with periodically varying mechanical constants with time. The loci of planet gear, sun gear. and carrier were analyzed. Maximum values of mesh forces between sun gear and planet gear(S/P) as well as between planet gear and ring gear(P/R) have been simulated as function of rotating speed.

• Journal of Ship and Ocean Technology
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• v.8 no.1
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• pp.10-30
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• 2004

High-fidelity RANS simulations are presented for a ducted marine propulsor, including verification ＆ validation (V＆V) using available experimental fluid dynamics (EFD) data. CFDSHIP-IOWA is used with $\textsc{k}-\omega$ turbulence model and extensions for relative rotating coordinate system and Chimera overset grids. The mesh interpolation code PEGASUS is used for the exchange of the flow information between the overset grids. Intervals V＆V for thrust, torque, and profile averaged radial velocity just downstream of rotor tip are reasonable in comparison with previous results. Flow pattern displays interaction and merging of tip-leakage and trailing edge vortices. In interaction region, multiple peaks and vorticity are smaller, whereas in merging region, better agreement with EFD. Tip-leakage vortex core position, size, circulation, and cavitation patterns for $\sigma=5$ also show a good agreement with EFD, although vortex core size is larger and circulation in interaction region is smaller.

• Journal of Electrical Engineering and Technology
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• v.7 no.3
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• pp.336-341
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• 2012

Deformations in a cage-induction machine are investigated with simulations. The contribution of the Maxwell stress in the air gap and coil regions of the machine on the deformation is studied by comparing results obtained with and without inclusion of the stress into the calculation. The work attests the acceptability of an energy-based magneto-mechanical model for a 2D mesh of two different rotating electrical machines.

• Journal of Aerospace System Engineering
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• v.9 no.4
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• pp.62-66
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• 2015

During the conceptual design of turboprop aircraft, the power effect driven from rotating propeller is typically obtained from empirical data. In the present paper, propeller power effect was obtained by using unsteady three-dimensional Navier-Stokes solver with $k-{\omega}$ turbulence model for the accurate prediction of turboprop aircraft performance. In order to simulate the relative motion between propeller and fuselage, unsteady sliding mesh method was used. During simulation, three flow conditions such as climb, cruise and descending flight were selected considering the flight envelop of the real turboprop aircraft. For the correction of aerodynamic coefficients, the thrust effect of engine exhaust gas was included based on the engine manufacturer's data. Using the computational results, the correction table for the aerodynamic coefficient of turboprop aircraft was suggested for the performance analysis of turboprop aircraft.

• Structural Engineering and Mechanics
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• v.60 no.6
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• pp.1079-1092
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• 2016

In this paper, an electromechanical integrated harmonic piezodrive system is proposed. The operating principle of the drive system is introduced. The equation of the relationship between the displacements of the flexible ring and the rotating angle of the rotor is deduced. Using the equation, the displacements of the flexible ring for the drive system and their changes along with the system parameters are investigated. The results show that the displacements of the flexible ring changes periodically along with the rotation of the vibrator; there are abrupt changes in the displacements of the flexible ring at some points where there are abrupt changes in the number of the mesh teeth pair; the length of the flexible ring, the excitation voltage, and the speed ratio have obvious effects on the displacements of the flexible ring. The results are useful for the design of the drive system. ;

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.65-72
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• 2012

Numerical simulations were performed to study the stall characteristics of turboprop aircraft. Stall characteristics were qualitatively investigated using the computational results of various configurations based on the combinations of propeller and high lift device. For the analysis of stall characteristics, three-dimensional Navier-Stokes solver with Spalart-Allmaras turbulence model was used and the relative motion between propeller and wing was simulated using sliding mesh technique. For the cruise configurations, major flow separation was occurred at the fuselage/wing fairing and the separation was reduced under propeller slipstream condition. For the high lift device configuration without propeller, major flow separation was occurred at the outboard side of nacelle. With rotating propeller, early stall onset due to low relative velocity and high effective angle of attack was observed on the outboard wing section. Regarding rotating direction of propeller, inboard-down direction was preferred due to the stall delay effect of propeller slipstream.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.883-898
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• 2019

This paper employs computational tools to predict power increase (or speed loss) and propulsion performances in waves of KVLCC2. Two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved using finite volume method; and a realizable k-ε model has been applied for the turbulent closure. The free-surface is obtained by solving a VOF equation. Sliding mesh method is applied to simulate the flow around an operating propeller. Towing and self-propulsion computations in calm water are carried out to obtain the towing force, propeller rotating speed, thrust and torque at the self-propulsion point. Towing computations in waves are performed to obtain the added resistance. The regular short head waves of λ/LPP = 0.6 with 4 wave steepness of H/λ = 0.007, 0.017, 0.023 and 0.033 are taken into account. Four methods to predict speed-power relationship in waves are discussed; Taylor expansion, direct powering, load variation, resistance and thrust identity methods. In the load variation method, the revised ITTC-78 method based on the 'thrust identity' is utilized to predict propulsive performances in full scale. The propulsion performances in waves including propeller rotating speed, thrust, torque, thrust deduction and wake fraction, propeller advance coefficient, hull, propeller open water, relative rotative and propulsive efficiencies, and delivered power are investigated.

• Journal of Energy Engineering
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• v.22 no.1
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• pp.28-37
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• 2013

Stirred tank is widely used in various industries for mixing operations and chemical reactions for single- or multi-phase fluid systems. For designing agitator of high performance, quantity data of internal flow characteristics influenced by mixing performance are definitely confirmed but quantity analysis about the transient flow characteristics of complicate structure is recognized as difficult problem in the present. In this study, two models of commercial CFD code Fluent 6.3 used to propose suitable for the tank analysis. Agitation of Stirred tank is analyzed using a mixed model and the flow in the stirred tank is analyzed using a standard k-${\varepsilon}$ model. Multiple reference frame(MRF) and Sliding mesh(SM), the analysis techniques were used For compare a result of CFD with a visualization experiment result, to grasp internal flow and mixing characteristic in stirred tank and to present fundamental analysis method.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.396-401
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• 2004

In this paper, a 1MW HAWT(FIL-1000) rotor blade has been designed by BEMT(Blade Element Momentum Theory) with Prandtl's tip loss. Also, a 3-D flow and performance analysis on the FIL-1000 rotor blade has been carried out by using the 3-D Navier-Stokes commercial solver (CFX-5.7) to provide more efficient design techniques to the large-scale HAWT engineers. The rated power and itsapproaching wind velocity at design point (TSR=7.5) are 1MW and 9.99m/s respectively. The rotor diameter is 54.5m and the rotating speed is 26.28rpm. Airfoils such as FFA W-301, DU91-W-250, DU93-W-210, NACA 63418, NACA 63415 consist of the rotor blade from hub to tip. Recent CFX version, 5.7 was adopted to simulate 3-D flow field and to analyze the performance characteristics of the rotor blade. Entire mesh node number is about 730,000 and it is generated by ICEM-CFD to achieve better mesh quality The predicted maximum power occurringat the design tip speed ratio is 931.45kW. Approaching to the root, the inflow angle becomes large, which causesthe blade to be stalled in the region. Therefore, k-$\omega$ SST turbulence model was used to predict the quantitative flow information more accurately. Application of commercial CFD code to optimum blade design and performance analysis was proved to be more effective environment to HAWT blade designers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.113-120
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• 2009

To numerically simulate aerodynamics of rotor-airframe interaction in a rigorous manner, we need to solve the Navier-Stokes system for a rotor-airframe combination in a single computational domain. This imposes a computational burden since rotating blades and a stationary body have to be simultaneously dealt with. An efficient alternative is a momentum source method in which the action of rotor is approximated as momentum source in a stationary mesh system built around the airframe. This makes the simulation much easier. The magnitude of the momentum source is usually evaluated by the blade element theory, which often results in a poor accuracy. In the present work, we evaluate the momentum source from the simulation data by using the Navier-Stokes equations only for a rotor system. Using this data, we simulated the time-averaged steady rotor-airfame interaction and developed the unsteady rotor-airframe interaction. Computations were carried out for the simplified rotor-airframe model (the Georgia Tech configuration) and the results were compared with experimental data. The results were in good agreement with experimental data, suggesting that the present approach is a usefull method for rotor-airframe interaction analysis.