• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1064-1074
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• 1992

Eliminating the under-cut caused by interference between a mold and a product in designing a mold for in jection molding processes is a very important problem. In general, the under-cut problem can be avoided by side cores which are the principal members of a mold assembly. In this research, a procedure has been developed by which the side cores and the corresponding core and cavity plates of a mold are generated after identifying the mold faces preventing product faces from moving while being discharged. The characteristic features of the procedure suggested in this paper are as follows. One is that the interference faces between the product and the mold are derived only from the core plate(or cavity plate) alone without considering the product together. The other is that the algorithm in the designing of side cores and modifying molds, is very efficient because it uses Euler operations instead of Boolean operations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.2
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• pp.99-104
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• 2008

This study performed robust design optimization of fighter wing planform, considering uncertainty based on neural network model. To construct uncertainty model, aerodynamic performance and their sensitivity were evaluated by 3-dimensional Euler equations and adjoint variable method at experimental points selected from central composite design. In addition, because a neural network model has the advantage of capturing non-linear characteristic, it was possible to predict sensitivity of the aerodynamic performance efficiently and accurately . From the results of robust design optimization, it could be confirmed that the robustness of the objective function and constraints were improved if the variation of uncertainty and sigma level were increased.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.10
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• pp.939-946
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• 2008

Euler codes or Navier-Stokes codes for compressible flows suffer severe degradation in convergence as Mach number approaches zero. The convergence problem arose from the wide disparity in characteristic speeds can be solved using preconditioning methods without large modifications. In this paper, a preconditioned RANS(Reynolds Averaged Navier-Stokes) solver is developed for analysis of low Mach number flows. In order to validate the method, computational examples are chosen and the results are compared with the experimental data and the existing computed results showing a good accuracy and convergence characteristics for steady inviscid, laminar and turbulent flows at low Mach number.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.3
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• pp.183-191
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• 2022

A design method for a propeller type rim-driven axial-flow turbine for a micro-hydropower system is presented. The turbine consists of pre-stator, impeller and post-stator, where the pre-stator plays a role as a guide vane to provide circumferential velocity to the on-coming flow, and the impeller as a rotational power generator by absorbing angular momentum of the flow. BEM(Blade Element Method), which is based on the turbine Euler equation, is employed to design the pre-stator and impeller blades. NACA 66 thickness form and a=0.8 mean camber line, which is widely accepted as a marine propeller blade section, is used for the pre-stator and turbine blade section. A CFD method, derived from the discretization of the RANS equations, is applied for the analysis of the designed turbine system. The design conditions of the turbine is confirmed by the CFD calculation. Turbine characteristic curve is calculated by the CFD method, in order to provide the performance characteristics at off-design operation conditions. The proposed procedures for the design of a propeller type rim-driven axial-flow turbine are established and confirmed by the CFD analysis.