• Journal of computational fluids engineering
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• v.11 no.1 s.32
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• pp.57-66
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• 2006

An optimal shape design approach is presented for a subsonic S-shaped intake using aerodynamic sensitivity analysis. Two-equation turbulence model is employed to capture strong counter vortices in the S-shaped duct more precisely. Sensitivity analysis is performed for the three-dimensional Navier-Stokes equations coupled with two-equation turbulence models using a discrete adjoint method For code validation, the result of the flow solver is compared with experiment data and other computational results of bench marking test. To study the influence oj turbulence models and grid refinement on the duct flow analysis, the results from several turbulence models are compared with one another and the minimum number of grid points, which can yield an accurate solution is investigated The adjoint variable code is validated by comparing the complex step derivative results. To realize a sufficient and flexible design space, NURBS equations are introduced as a geometric representation and a new grid modification technique, Least Square NURBS Grid Approximation is applied With the verified flow solver, the sensitivity analysis code and the geometric modification technique, the optimization of S-shaped intake is carried out and the enhancement of overall intake performance is achieved The designed S-shaped duct is tested in several off-design conditions to confirm the robustness of the current design approach. As a result, the capability and the efficiency of the present design tools are successfully demonstrated in three-dimensional highly turbulent internal flow design and off-design conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.12
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• pp.1095-1102
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• 2016

This paper presents the results of the design, fabrication and tether test for a gross weight 20 kg tilt-duct VTOL aerial robot. The tilt-duct vehicle, a tri-ducts air-vehicle, which composed of two main tilt ducts for thrust and an aft-fan for pitch attitude control, has been developed as an aerial platform. The research on the air vehicle has been focused on the hover characteristics and controllability to improve the thrust and stability. The tether test for measuring various performance of vehicle and evaluating controllability have been carried out to figure out effects of modified main-prop linkage, actuator, duct configuration and control surfaces.

• Journal of Ocean Engineering and Technology
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• v.35 no.4
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• pp.247-256
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• 2021

In order to minimize carbon emissions and greenhouse gas, the Energy Efficiency Design Index (EEDI) has become a major factor to be considered in recent years in a ship's design and operation phases. Energy-Saving Devices (ESDs) improve the EEDI of a vessel and make them environmentally friendly. In this research, the performance of an equalizing duct-type ESD installed upstream of a Korea Research Institute of Ships & Ocean Engineering (KRISO) Container Ship (KCS) model's propeller was investigated by computational fluid dynamics (CFD). Open-source CFD libraries, OpenFOAM, were used for computational analysis of the KCS with and without the ESD to verify the performance improvement. The flow field near the stern region and propulsive coefficients were considered for comparison. The results showed a considerable improvement when an ESD was used on the model. Using different sizes of the duct, the performance of the ESD was also compared. It was observed that with an increased duct size, the propulsive performance was improved.

• Computers and Concrete
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• v.21 no.1
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• pp.75-85
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• 2018

To improve the design equation for the evaluation of the bursting force in the post-tensioned anchorage zone, this paper presents the analyses and design of the post-tensioned (PT) anchorage zone on the basis of three dimensional (3D) finite element (FE) analyses. The structural behavior was investigated through linear elastic finite element analyses upon consideration of the change in design parameters such as the bearing plate size, the eccentricity, and the tendon inclination. Moreover, consideration of the duct hole, which causes an increase of the bursting stress with a change in its distribution along the anchorage zone as well, is emphasized. Since that an exact prediction of the bursting force is the primary interest in design practice, additional parametric analyses are carried out to evaluate the relative contribution of all design parameters in determining the bursting force, and a comparison with the design guidelines mentioned in AASHTO-LRFD has been provided. Finally, an improved design guideline that takes into account the influence by the duct hole is suggested.

• Journal of Power System Engineering
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• v.21 no.4
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• pp.84-93
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• 2017

This study was carried out to improve the electric power consumption of HVAC in the blow mold machine(BMM) and work environment. The experiment was conducted with the simulated HVAC system of 1/15 of the actual BMM. The temperature of main facility and two preheaters was fixed at 200 and $60^{\circ}C$ respectively in all test conditions. The measured points of temperature were chosen as critical locations considering the work environment. The tendency of temperature distributions decreases as the duct was closed to the main facility. The reduction rate of power consumption of HVAC increases up to 32.3% when both duct and cooling systems are operated. Also the efficiency of HVAC is improved about 9% through the modified design of duct system. It notes that the electric power consumption of HVAC can be reduced by the optimum design and operating condition of duct and cooling system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.17-25
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• 2019

An intake of Aircraft becomes S-shaped geometry due to spatial limitation or procuring survivability. But curvature of the S-shaped geometry makes secondary flow or flow separation which is the cause of non-uniform pressure distribution. In this study, boundary layer suction is applied to RAE M 2129 S-Duct by attaching sub duct. Design variable is suction location and angle. A mass flow rate drawn out by suction at the sub duct outlet is constant over every model. A grid dependency test was conducted to verify validity of computation. The comparison among the CFD (Computation Fluid Dynamics), ARA experimental result, and ARA computation result of non-dimensional pressure distribution on the Port side and Starboard Side confirmed the validity of CFD. In this study, Distortion Coefficient was used for evaluating aerodynamic performance of S-Duct. The analysis, which was about flow separation, vortex, mass flow rate distribution, and pressure distribution were also investigated. Maximum 26.14% reduction in Distortion Coefficient was verified.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.3
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• pp.145-152
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• 2013

Recently, with oil price jumping and environmental issues, Green ship is paid deep attention to by ship owner, operator, builder, class and government. Fuel efficiency and reduction of $CO_2$ emissions are expected to have a strong influence on the design and operation of merchant ships. Many ship owners and operators are seeking the more economic method by the best operating route and the application of reliable and effective energy saving devices. With the Energy Efficiency Design Index (EEDI) in 2013 attention will more than ever be focused at achieving maximum fuel economy in the hydrodynamic design of hull forms, their appendages and propellers. IMO requirements for $CO_2$ emission for ships will now be implemented for vessels ordered from 1st January 2013. So far, a lot of new idea and patents have been proposed, tested, claimed and applied for various kinds of ship type. This paper shows numerical and experimental work related to a study on a energy saving devices particularly for fuller ship such as merchant vessel of Tanker and Bulker. From the bare hull wake measurements, typical upper/lower asymmetry of hull wake at the propeller disk was found. The pre-swirl duct have been designed and reviewed to recover the loss of propeller running in that condition. The general function of the pre-swirl duct was set to work against this asymmetry of wake and generate pre-swirled flow into the propeller against the propeller rotating direction.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.124-131
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• 2019

A design study of gas turbine engine simulation duct was conducted to investigate the operating characteristics and control gain tunning of the Altitude Engine Test Facility(AETF). The simulation duct design involved testing variable spike nozzle and ISO standard choking nozzle to verify the measurements such as mass flow rate and thrust. The simulation duct air flow area was designed to satisfy Ma 0.4 at the aerodynamic interface plane(AIP) at engine design condition. The test conditions for verifying the AETF controls and measurement devices were deduced from 1D analysis and CFD calculation results. The spike-cone driving part was designed to withstand the applied aero-load, and satisfy the axial traversing speed of 10 mm/s at whole operation envelops.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.373-377
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• 2005

The Performance of in-line duct fan depends on the design parameters of impeller and guide vane. such as sweep back angle of impeller, the number of blades, outlet blade angle, guide vane angle etc. In this experimental study total four kinds of impellers having different sweep back angles, $90^{\circ},\;72.5^{\circ},\;55^{\circ},\;37.5^{\circ}$ with 8 guide vanes, different the number of blades, 6ea, 8ea, 10ea, 12ea, different kinds of outlet blade angles, $30^{\circ},\;45^{\circ}.\;60^{\circ}$ and different kinds of guide vane angles, $15^{\circ},\;30^{\circ},\;45^{\circ}$ were selected and their performance measured to investigate the effects of them. The results were non-dimensionalized to compare their performance.

• KIEAE Journal
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• v.9 no.4
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• pp.17-22
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• 2009

It is common to design the duct branches where to supply the required air flow for individual room in residential apartment house. However it is difficult to adjust the air volume adequately in small air duct branches in residential ventilation system. The purpose of this study is to figure out the performance of Multidrop chamber coupling system for the residential ventilation system. The experiments were designed to simulate apartment of $84m^2$ and established multidrop chamber duct and general duct on the ceiling of the apartment. Distribution performance of air supply rate were evaluated in this experiments. As a result, distribution performance of air supply rate in the general duct is different from designed air supply rate by about 35% ~ 50% and about 10% in the multidrop chamber system. In additional the sound insulation performance of the multidrop chamber system decreased about 20% compared with general duct system. Therefore, the multidrop chamber system is considered to satisfy proper air supply rate of each room and to improve the sound insulation performance in apartment Houses.