• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.73-76
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• 2007

The present paper describes the results of performance analysis for UH-60A rotor blade in hover. For the numerical simulations, commercial CFD software, FLUENT was used with Spalart-Allmaras turbulence model. The flow solver was based on node based scheme and second order spatial accuracy options was used for simulations. For the enhancement of wake capturing capability, high resolution grid was used around tip vortex region. Granting that somewhat over prediction of thrust was observed near blade tip region, performance was well correlated with experimental data within 3% accuracy in the operating region. Finally it was shown that the present flow solver can be used for preliminary performance analysis tool for hovering helicopter rotor blades.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.263-265
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• 2003

The aerodynamic performance of a shrouded tail rotor in hover has been studied by using a compressible inviscid flow solver on unstructured meshes. The numerical method is based on a cell­centered finite-volume discretization and an implicit Gauss-Seidel time integration. The results show that the performance of an isolated rotor without shroud compares well with experiment. In the case of a shrouded rotor, correction of the collective pitch angle is made such that the overall performance matches with experiment to account for the uncertainties of the experimental model configuration. Details of the flow field compare well with the experiment confirming the validity of the present method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.1-9
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• 2003

Detailed flow of a shrouded tail rotor in hover is studied by using a compressible inviscid flow solver on unstructured meshes. The numerical method is based on a cell-centered finite-volume discretization and an implicit Gauss-Seidel time integration. Numerical simulation is made for a single blade attached to the center body and guide by the duct by imposing a periodic boundary condition between adjacent rotor blades. The results show that the performance of an isolated rotor without shroud compares well with experiment. In case of a shrouded rotor, correction of the collective pitch angle is made such that the overall performance matches with experiment to account for the uncertainties of the experimental model configuration. Details of the flow field compare well with the experiment confirming the validity of the present method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.513-520
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• 2014

An unmanned aerial vehicle (UAV) should be designed to be as small and lightweight as possible to optimize the efficiency of changing the blade shape to enhance the aerodynamic performance, such as the thrust and power. In this study, a computational fluid dynamics (CFD) simulation of an unmanned multi-rotor aerial vehicle in hover mode was performed to explore the thrust performance in terms of the blade rotational speed and blade shape parameters (i.e., taper ratio and twist angle). The commercial ADINA-CFD program was used to generate the CFD data, and the results were compared with those obtained from blade element theory (BET). The results showed that changes in the blade shape clearly affect the aerodynamic thrust of a UAV rotor blade.

• Journal of computational fluids engineering
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• v.17 no.2
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• pp.78-84
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• 2012

Numerical calculations were performed to investigate the influence in aerodynamic characteristics of a rotor system by surrounding structures and the ground effect for the rotor blade on a whirl tower is also investigated. Three dimensional Navier-Stokes simulations were carried out by using unstructured overset mesh technique and parallel computation. The calculated hover performance showed good agreement with the experimental result and showed that the structures around the whirl tower did not affect the aerodynamic characteristics of the blade. The ground effect was studied by comparing with the numerical result for the out of ground condition and the result of an analytic model.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.415-421
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• 2006

The unsteady flow calculation around the proprotor of Smart UAV was conducted. Using the flight scenario of SUAV which composed of hover, transition, and airplane mode, the aerodynamic analysis of proprotor were performed for the variation of collective pitch, rpm, forward speed, and tilt angle. The unsteady compressible Navier-Stokes equations were used for the calculation and the dynamic overset grid technique was applied for the rotating proprotor. The aerodynamic performance of proprotor calculated in this way were validated by comparing with the performance data obtained from the blade element momentum method.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.154-164
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• 2017

This work conducts a validation study for the XH-59A helicopter using a rigid coaxial rotor system in order to establish the techniques of the conceptual design and performance analysis for the lift-offset compound rotorcraft. As a tool for conceptual design and performance analysis, NDARC (NASA Design and Analysis of Rotorcraft) is used for the present study. An assumed mission profile is considered for the conceptual design of the XH-59A. As a validation result of the design, the dimensions and weight of the XH-59A are appropriately designed when compared to the target values since the relative error is less than 0.5%. Then, performance analyses are conducted for the designed XH-59A model with and without auxiliary propulsion in hover and forward flight conditions. The present analyses show good validity since the prediction results compare well with both the flight test and previous analyses. Therefore, the techniques for the conceptual design and performance analysis of the lift-offset compound helicopter are overall considered to be appropriately established. In addition, this study investigates the influence of the lift-offset on the rotor effective lift-to-drag ratio of the XH-59A helicopter with auxiliary propulsion. As a result, the improvement of the rotor effective lift-to-drag ratio can be obtained by appropriately increasing the lift-offset in high-speed flight.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.221-231
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• 2021

In the present study, numerical simulation was performed to investigate aerodynamic characteristics of a ducted fan-upper/lower vanes system in hover. Sensitivity analysis of aerodynamic forces for a system component was conducted with the deflection angle of upper vanes varying but at the constant rotational speed and the collective pitch angle of fan blades. Then, vane control performance and duct airload distributions were analyzed in detail to physically understand operating mechanisms of individual vane and interference effect between duct and vanes. Finally, new control concept of operating upper vanes has been proposed to improve the control performance of the full configuration. It is found that the side force and rolling moment of upper vanes increase linearly with the variation of those deflection angle; however, the total side force is significantly small due to the reaction force acted on the duct. It is also found that upper vanes close to the duct contraction side have a key role in changing vane control forces. It is revealed that the duct suction pressure is induced by the interaction with the suction side of upper vanes, while duct pressure recovery by the interaction with the pressure side, leading to increase in duct asymmetric force. When four upper vanes are kept in situ at 0° deflection angle or removed, the total control performance was improved with duct asymmetric force reduced and the total magnitude of roll remarkably increasing up to 80%.

• Journal of Computing Science and Engineering
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• v.7 no.2
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• pp.122-131
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• 2013

The MPI CyberMotion Simulator provides a unique motion platform, as it features an anthropomorphic robot with a large workspace, combined with an actuated cabin and a linear track for lateral movement. This paper introduces the simulator as a tool for studying human perception, and compares its characteristics to conventional Stewart platforms. Furthermore, an experimental evaluation is presented in which multimodal human control behavior is studied by identifying the visual and vestibular responses of participants in a roll-lateral helicopter hover task. The results show that the simulator motion allows participants to increase tracking performance by changing their control strategy, shifting from reliance on visual error perception to reliance on simulator motion cues. The MPI CyberMotion Simulator has proven to be a state-of-the-art motion simulator for psychophysical research to study humans with various experimental paradigms, ranging from passive perception experiments to active control tasks, such as driving a car or flying a helicopter.

• The Journal of the Acoustical Society of Korea
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• v.16 no.1E
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• pp.29-34
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• 1997

Numerical prediction of aerodynamic noise radiated by subsonic rotors are carried out. A computer program has been developed which incorporates both the discrete frequency noise as well as the broadband noise arising from the ingestion of turbulence. Acoustic analogy is used in conjunction with Homicz's formulation of turbulence ingestion noise. Formulation 1A of Farassat is used to enhance the numerical analysis performance of Ffowcs-Williams Hawkings equation by eliminating the numericla time differentiation. Homicz's trubulence ingestion noise prediction technique is used to understand the characteristics of broadband noise radiated by isotropic trubulence in gestion. Numerical predictions are carried out for a number of rotor configurations and compared with experimental data. Monopole consideration of transonic rotor agrees well with both the experimental data and the linear theory. Noise radiation characteristics of rotor at lifting hover are investigated utilizing simple blade loading obtained by thin wing section theory. By incorporating discrete noise prediction of steady loading with broadband spectrum, much better agreement with experimental data is obtained in the low frequency region. The contributions from different noise mechanisms can also be analyzed through this method.