• International Journal of Aeronautical and Space Sciences
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• v.4 no.1
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• pp.45-52
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• 2003

A three-dimensional aerodynamic shape optimization technique in inviscid compressible flows is developed by using a parallel continuous adjoint formulation on unstructured meshes. A new surface mesh modification method is proposed to overcome difficulties related to patch-level remeshing for unstructured meshes, and the effect of design sections on aerodynamic shape optimization is examined. Applications are made to three-dimensional wave drag minimization problems including an ONERA M6 wing and the EGLIN wing-pylon-store configuration. The results show that the present method is robust and highly efficient for the shape optimization of aerodynamic configurations, independent of the number of design variables used.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.3
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• pp.288-295
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• 2011

This paper addresses minimum-fuel, two-dimensional trajectory optimization for a soft lunar landing from a parking orbit to a desired landing site. The landing site is usually not considered when performing trajectory optimization so that the landing problem can be handled. However, for precise trajectories for landing at a desired site to be designed, the landing site has to be considered as the terminal constraint. To convert the trajectory optimization problem into a parameter optimization problem, a pseudospectral method was used, and C code for feasible sequential quadratic programming was used as a numerical solver. To check the reliability of the results obtained, a feasibility check was performed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.262-265
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• 2005

A shape optimization of flow guide is accomplished to minimize the wear rate of die in three-dimensional flat-die extrusion processes. In order to achieve the balanced flow and the uniformed distribution of the effective strain during the extrusion, a multi-objective optimization is implemented. During the process of optimization formulation, the flow balance and the deviation of strain is considered as constrained conditions. The proposed approach is applied to an extrusion of H section. Through the optimization, it has been confirmed that the wear rate of die can be minimized satisfying the constraint.

• Advances in aircraft and spacecraft science
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• v.10 no.3
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• pp.245-256
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• 2023

In order to improve aerodynamic performance of multi-stage axial flow turbines used in aircraft engines, a one-dimensional aerodynamic design and optimization framework is constructed. In the method, flow path is generated by solving mass continuation and energy conservation with loss computed by the Craig & Cox model; Also real gas properties has been taken into consideration. To obtain an optimal result, a multi-objective genetic algorithm is used to optimize the efficiencies and determine values of various design variables; Final design can be selected from obtained Pareto optimal solution sets. A three-stage axial turbine is used to verify the effectiveness of the developed optimization framework, and designs are checked by three-dimensional CFD simulation. Results show that the aerodynamic performance of the optimized turbine has been significantly improved at design point, with the total-to-total efficiency increased by 1.17% and the total-to-static efficiency increased by 1.48%. As for the off-design performance, the optimized one is improved at all working points except those at small mass flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.5
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• pp.630-639
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• 1998

The present research aimed at development of a computer code for the optimal design of ventilation system based on one-dimensional analysis of the air flow. Model experiment and three-dimensional flow analysis have been implemented to determine loss coefficients that were needed for the optimization technique. A research on optimum shape of ventilation shaft has been also carried out through the three-dimensional analysis of the flow.

• Journal of Mechanical Science and Technology
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• v.15 no.11
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• pp.1541-1547
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• 2001

The non-dimensional fin length for optimum heat loss from a thermally asymmetric rectangular fin is represented as a function of the ratio of the bottom surface Biot number to the top surface Biot number, fin tip surface Biot number and the non-dimensional fin width. Optimum heat loss is taken as 98% of the maximum heat loss. For this analysis, three dimensional separation of variables method is used. Also, the relation between the ratio of the bottom surface Biot number to the top surface Biot number and the ratio of the right surface Biot number to the left surface Biot number is presented.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1995.10b
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• pp.33-39
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• 1995

One dimensional optimization problem is considered, we propose a method to find the global minimum of one-dimensional function with on gradient information but only the finite number of input-output samples. We construct a learning network which has a good learning capability and of which global maximum(or minimum) can be calculated with simple calculation. By teaching this network to approximate the given function with minimal samples, we can get the global minimum of the function. We verify this method using some typical esamples.

• Journal of Aerospace System Engineering
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• v.7 no.3
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• pp.1-6
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• 2013

Numerical optimization of two dimensional high lift configuration was performed with flow solver and optimization method based on RSM(Response Surface Model). Navier-Stokes solver with Spalart-Allmaras turbulence model was selected for the simulation of highly complex and separated flows on the flap. For the simultaneous optimization of both flap shape and setting (gap/overlap), 10 design variables (eight variables for flap shape variation and two variables for flap setting) were chosen. In order to generate the response surface model, 128 experimental points were selected for 10 design variables. The objective function considering maximum lift coefficient, lift to drag ratio and lift coefficient at specific angle of attack was selected to reduce flow separation on the flap surface. The present method was applied to two dimensional fowler flap in landing configuration. After applying the present method, it was shown that the optimized high lift configuration had less flow separation on the flap surface and lift to drag ratio was suppressed over entire angle of attack range.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.684-689
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• 2001

In this study, three-dimensional viscous flow analysis and optimization are presented for the design of a mixed-flow fan. Steady, imcompressible, three-dimensional Reynolds averaged Navier-Stokes equations are used as governing equations, and standard $k-{\varepsilon}$ turbulence model is chosen as a turbulence model. Governimg equations are discretized using finite volume method. Upwind difference scheme is used for the discretization of the convective term and SIMPLEC algorithm is used as a velocity-pressure correction procedure. The computational results are compared with the results obtained by TASCflow. For the numerical optimization of the design, objective function is defined as a ratio of generation of the turbulent energy to pressure head. Sweep angles are used as design variables.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.9
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• pp.1337-1343
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• 2004

Shape optimization was performed to obtain a precise shape of cutouts including the internal shape of cutouts in a laminated composite plate by three dimensional modeling using solid element. Volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. It makes Tsai-Hill failure index at each element uniform in laminated composites under the predetermined volume a designer requires. Shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study; (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminate composite, (2) The optimal shapes of the various load conditions and cutouts were obtained, (3) The maximum Tsai-Hill failure indices of the optimal shapes were remarkably reduced comparing with those of the initial shapes.