• The KSFM Journal of Fluid Machinery
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• v.3 no.3 s.8
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• pp.31-40
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• 2000

A computer program is developed for the prediction of the aerodynamic performance and the noise characteristics in the basic design step of axial flow fan. The flow field and the performance of fan are analyzed by using the streamline curvature computing scheme with total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuations induced by wake vortices of fan blades and to radiate via dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted performances, sound pressure level and noise directivity patterns of fan by the present method are favorably compared with the test data of actual fan. Furthermore, the present method is shown to be very useful in optimizing design variables of fan with high efficiency and low noise level.

• Smart Structures and Systems
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• v.14 no.4
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• pp.659-678
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• 2014

The study is aimed at investigating the feasibility of a high TRL solution for a wing flap segment characterized by morphable camber airfoil and properly tailored to be implemented on a real-scale regional transportation aircraft. On the base of specific aerodynamic requirements in terms of target airfoil shapes and related external loads, the structural layout of the device was preliminarily defined. Advanced FE analyses were then carried out in order to properly size the load-carrying structure and the embedded actuation system. A full scale limited span prototype was finally manufactured and tested to: ${\bullet}$ demonstrate the morphing capability of the conceived structural layout; ${\bullet}$ demonstrate the capability of the morphing structure to withstand static loads representative of the limit aerodynamic pressures expected in service; ${\bullet}$ characterize the dynamic behavior of the morphing structure through the identification of the most significant normal modes. Obtained results showed high correlation levels with respect to numerical expectations thus proving the compliance of the device with the design requirements as well as the goodness of modeling approaches implemented during the design phase.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.34.1-34.1
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• 2011

풍력발전기 블레이드 설계에 적용하기 위한 에어포일의 선택 혹은 설계에 있어서 가장 중요한 요소 가운데 하나는 표면 거칠기 변화에 따른 에어포일 성능의 민감도이다. 블레이드 표면은 대기 중의 먼지, 곤충 시체 등에 따라 계속적으로 오염되며 이는 에어포일의 설계 당시의 성능을 계속적으로 저감시킨다. 이러한 표면 거칠기의 증가는 에어포일의 종류에 따라 성능을 50% 이상 저감시키며 이는 블레이드의 설계 성능을 저감시키므로 블레이드 설계를 위한 에어포일 선정 단계에서 표면거칠기 민감도가 가능한 낮은 에어포일을 선정하여 블레이드의 공력 설계를 수행하게 된다. 본 연구에서는 표면 거칠기 변화로 인한 에어포일의 성능 저감이 실제 블레이드의 성능에 어떠한 영향을 주는지를 살펴 보았다. 에어포일은 표면이 깨끗한 상태와 ZZ 테입을 부착하여 표면이 심각하게 오염된 상황을 모사하여 두 경우 모두를 풍동 시험한 DU 에어포일 시리즈를 선정하였다. 3MW 급의 블레이드에 대하여 두께비 40%~18%의 에어포일을 적용하여 설계를 수행하였으며 두께비 30%~18%에어포일에 대하여 표면이 깨끗한 경우와 오염된 경우의 데이터를 적용하여 블레이드 성능 변화 및 다른 성능 변수들의 변화를 살펴보았다. 블레이드 성능에 대하여는 BEMT를 적용하여 설계 및 시뮬레이션을 수행하였다. 연구 결과 에어포일의 성능 저하는 블레이드 공력 효율에 있어서 8%의 저감을 나타내며 7%의 극한하중 저감을 보이는 것으로 나타났다.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1874-1889
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• 2022

In this study, we evaluate the thermal-hydraulic performance and economics of Printed Circuit Heat Exchanger (PCHE) according to the channel types and associated shape variables for the design of recuperators with Sodium-cooled Fast Reactors (SFRs). To perform the evaluations with variables such as the Reynolds number, channel types, tube diameter, and shape variables, a code for the heat exchanger is developed and verified through a comparison with experimental results. Based on the code, the volume and pressure drop are calculated, and an economic assessment is conducted. The zigzag type, which has bending angle of 80° and a tube diameter of 1.9 mm, is the most economical channel type in a SFR using CO₂ as the working fluid. For a SFR using N₂, we recommend the airfoil type with vertical and horizontal numbers of 1.6 and 1.1, respectively. The airfoil type is superior when the mass flow rate is large because the operating cost changes significantly. When the mass flow rate is small, volume is a more important design parameter, therefore, the zigzag type is suitable. In addition, we conduct a sensitivity analysis based on the production cost of the PCHE to identify changes in optimal channel types.

• Journal of Ocean Engineering and Technology
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• v.37 no.4
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• pp.129-136
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• 2023

To evaluate manoeuvring performance of merchant ships, the mathematical modeling group (MMG) or computational fluid dynamics (CFD) simulations are used. However, it is difficult to use the MMG to evaluate the manoeuvring performance of fishing vessels, thus research using CFD simulations is necessary. Also, since the course-changing and turning ability is crucial in fishing operations, a rudder design suitable for fishing vessels is necessary. This study designs a rudder using National Advisory Committee for Aeronautics (NACA) airfoil sections and evaluates its manoeuvring performance. A CFD model is used to evaluate the manoeuvring performance of the fishing vessel, and turning and zig-zag tests are conducted. The effectiveness of using CFD simulations based on Reynolds averaged Navier-Stokes equations to assess the manoeuvring performance of fishing vessels was validated. No significant difference was found in the manoeuvring performance for hull forms and rudder designs for course-changing ability. However, the original hull form showed superior turning performance. Among five rudders with varying aspect ratios and shapes, the rudder with 5.5% aspect ratio had the best turning performance. Regarding the rudder design for fishing vessels, NACA airfoil was employed, and a rudder aspect ratio of 5.5% based on the immersed hull side area is recommended.

• Structural Engineering and Mechanics
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• v.88 no.4
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• pp.301-309
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• 2023

In this paper, a new modified conjugate gradient (MCG) method is presented which is based on a new gradient regularizer, and this method is used to identify the dynamic load on airfoil structure without and with considering random structure parameters. First of all, the newly proposed algorithm is proved to be efficient and convergent through the rigorous mathematics theory and the numerical results of determinate dynamic load identification. Secondly, using the perturbation method, we transform uncertain inverse problem about force reconstruction into determinate load identification problem. Lastly, the statistical characteristics of identified load are evaluated by statistical methods. Especially, this newly proposed approach has successfully solved determinate and uncertain inverse problems about dynamic load identification. Numerical simulations validate that the newly developed method in this paper is feasible and stable in solving load identification problems without and with considering random structure parameters. Additionally, it also shows that most of the observation error of the proposed algorithm in solving dynamic load identification of deterministic and random structure is respectively within 11.13%, 20%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.648-651
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• 2010

Propeller shall have high efficiency and improved aerodynamic characteristics to get the thrust to fly at high speed for the FAR25 turboprop aircraft. That is way Clark-Y airfoil which is used to conventional turboprop aircraft propeller is selected as a blade airfoil. Javaprop program based on the Adkins method is used for aerodynamic design and analysis of propeller, Adkins method is based on the vortex-blade element theory which design the propeller to satisfy the condition for minimum energy loss. Slipstream displacement don't change and consider a rigid body. High efficiency propeller geometry is generated by varying chord length and pitch angle at design point of FAR25 turboprop aircraft. The propeller design results indicate that could be applied to the FAR25 turboprop aircraft, through analysis of propeller aerodynamic characteristics using the CFD(Computational Fluid Dynamic).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.5
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• pp.465-475
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• 2012

This study was carried out with two goals. One was the development of a model of a wind turbine blade airfoil and the other was the application of this folding blade. In general, in large-sized (MW) wind turbines, damage is prevented because of the use of a pitch control system. On the other hand, pitch control is not performed in small wind turbines since equipment costs and maintenance costs are high, and therefore, the blade will cause serious damage. The wind turbine proposed in this study does not require maintenance, and the blades do not break during high winds because they are folded in accordance with changes in the wind speed. But generators are not cut-out, while maintaining a constant angle will continue to produce. The focus of this study, the wind turbine is continued by folding blade system in strong winds and gusts without stopping production.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.6
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• pp.424-432
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• 2023

This study deals with the design of a safety device around a leisure boat propeller. The safety device is to be designed to minimize performance degradation attached to propulsors in coastal waters. These devices, important for preventing propeller accidents, negatively gives influence boat performance, especially at higher speeds. In order to minimize the negative effect, the accelerating ducts, normally used in ESDs (Energy Saving Devices) have been chosen as a safety device. The present study aims to design an optimal duct (minimizing negative effect) through the parametric study. Based on the Marine 19A nozzle, the nozzle's thickness and angle were varied to obtain the optimum parameter in the preliminary design by the computational fluid dynamics program Star-CCM+ Ver. 15.02. In the detailed design, a NACA 4-digit Airfoil shape resembling the Marine 19A by modification at the trailing edge was chosen and the optimum shape was chosen according to variation of camber, thickness, and incidence angle for optimization. The optimally designed duct shows a speed decrease of about 10% in the sea trial result, which is much smaller than the normal speed decrease of at least 30%. The present designing method can give wide applications to the leisure boat because the wake is almost the same due to using the outboard propulsor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.37-46
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• 2004

Several notes on ground effects drawn from Navier-Stokes analyses and their aerodynamic interpretations were addressed here; For two-dimensional ground effect, the change of surface pressure due to image vortex, the venturi effect due to thickness and the primary inviscid flow phenomena of ground effect, and for three-dimensional ground effect, strengthened wing tip vortices, increased effective span and the outward drift of trailing vortices. Irodov's criteria were evaluated to investigate the static longitudinal stability of conventional NACA 6409 and DHMTU 8-30 airfoils. The analysis results demonstrated superior static longitudinal stability of DHMTU 8-30 airfoil. The DHMTU airfoil has quite lower value of lrodov's criterion than the conventional NACA airfoil, which require much smaller tail volume to stabilize the whole WIG-craft at its design stage.