• 한국전산유체공학회:학술대회논문집
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• 2000.10a
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• pp.170-175
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• 2000

Parametric studies are performed of the factors influencing the afterbody drag. To display the effect of differing afterbody shapes, several ogive boattails with combinations of the base area and the angle of boattail end are computed using axisymmetric Navier-Stokes equations with central differencing and a DADI scheme. And Chien's $\kappa-\epsilon$ model is employed used for computations of turbulent flows around the base region. The effects of base area, boattail angle and jet on/off are illustrated on afterbody drag at transonic speed.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.625-636
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• 2019

Recently, research on projectiles with wings for precision guidance is actively underway. In this study, we analyzed how the tail fins attached to the projectile affect the base drag. Aerodynamic analysis was performed with RANS(Reynolds Averaged Navier-Stokes) equations using FLUENT, a commercial CFD(Computational Fluid Dynamics) code. Through the aerodynamic analysis, the base drag characteristics of the projectile by parameters (number, length, thickness, position, shape of tail fin) were investigated. The results of this study are expected to be applicable to aerodynamic design of tail fins mounted on projectiles.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.253-258
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• 2001

Control of drag force on a circular cylinder using a detached splitter plate is numerically studied for laminar flow. A splitter plate with the same length as the cylinder diameter(d) is placed horizontally in the wake region. Its position is described by the gap ratio(G/d), where G represents the gap between the cylinder base point and the leading edge of the plate. The drag varies with the gap ratio; it has the minimum value at a certain gap ratio for each Reynolds number. The drag sharply increases past the optimum gap ratio; this seems to be related to the sudden change in the bubble size in the wake region. This trend is consistent with the experimental observation currently available in case of turbulent flow. It is also found that the net drag coefficient significantly depends on the variation of base suction coefficient.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.43-46
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• 2004

Numerical analysis for pressure drag on boattail afterbodies have been studied by Mach number, boattail angle and length ratio of body diameter and base diameter using CFD-FASTRAN that the commercial external flow CFD code. The numerical results have been compared with the experimental data that have been shown pressure drag reduction and supersonic turbulent flow characteristics for boattail afterbodies. And the prediction equation tot boattail base drag has been made by the numerical results about Mach number and boattail configuration parameters.

• 한국전산유체공학회:학술대회논문집
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• 2001.05a
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• pp.60-65
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• 2001

The projectile afterbodies for zero-lift drag reduction has been analyzed using the Navier-Stokes equations with the $\kappa-\epsilon$ turbulence model. The numerical method of a second order upwind scheme has been used on unstructured adaptive meshes. Base drag reduction methods that have been found effective on axisymmetric bodies include boattailing, base bleed, base comustion, locked vortex afterbodies and multistep afterbodies. In this paper, the charateristics of turbulence flow have been studied for geomeries of multistep afterbodies. The important geometrical and flow parameters relevant to the design of such afterbodies have been identified by number, length and height of step. The flow over multistep afterbodies has been analyzed including expansion waves, recompression waves, recirculating flow, shear flow and wake flow. The numerical results have been compared and analyzed with the experimental datum.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.92-97
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• 2007

Numerical simulations were carried out to investigate the base drag characteristics of a base bleed projectile with a central propulsive jet by considering the base burning process. Overall fluid dynamic process is modeled by Navier-Stokes equations for reacting flows with two-equation $k-{\omega}$ SST turbulence closure. The combustion process is modeled by finite-rate chemistry with a given partially burned exit condition of the BBU (base-bleed unit). Besides the demonstrating the capability of the present CFD solver for the base drag and the interaction of the base flow with a rocket plume, present study gives an insight into the fluid dynamics and the combustion process of the hybrid-propulsion projectile.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1632-1639
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• 2001

Control of drag farce on a circular cylinder using a detached splitter plate is numerically studied for laminar flow. A splitter plate with the same length as the cylinder diameter(d) is placed horizontally in the wake region. Its position is described by the gap ratio(G/d), where G represents the gap between the cylinder base point and the leading edge of the plate. The drag varies with the gap ratio; it has the minimum value at a certain gap ratio for each Reynolds number. The drag sharply increases past the optimum gap ratio; this seems to be related to the sudden change in bubble size in the wake region. This trend is consistent with the experimental observation currently available in case of turbulent flow. It is also found that the net drag coefficient significantly depends on the variation of base suction coefficient.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.479-483
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• 2005

BBU is the weapon system for the extension of range through the reduction of base drag in 155mm. It has been mass-produced since 2000. The purpose of this research is productivity increase through the reduction of process lead time. Development process is as follows. First, formulation tests about propellent and liner, Second, spin test and final firing test about end products.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.652-655
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• 2010

BBU attached to the 155mm is the weapon system for the extension of range through the reduction of base drag. This research focus on the development of inhibitor formulation changing cure agent from DDI to IPDI. Development process is as follows. First, the formulation test about basic property Second, the study on the application of process. Third, the tests for the quality and aging properties. The test results are satisfied with the all of the requirments. In results, this research is contributed to the stable manufacturing in the instability of supplying of cure agent.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.817-832
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• 2021

In this paper, a simple practical method to estimate the drag of Super-Cavitating Underwater Vehicles (SCUV) is proposed that can obtain the drag with only principal dimensions in an initial design stage. SCUV is divided into cavitator, forebody, afterbody, base, and control fin and the drag of each part is estimated. The formulas for the drag coefficient are proposed for the disk and cone type cavitators and wedges used as control fins. The formulas are a function of cavitation number, cone or wedge angle, and Reynolds number. This method can confirm the drag characteristics of SCUV that the drag hump appears according to the coverage of the body by the cavity and the cavitator drag remains only when the entire body is covered by cavity. Applying this method to SCUV of various shapes, it is confirmed that the effects of cavitating and non-cavitating conditions, cavitator and body shape, and speed could be found.