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황영모(Y. M. Hawng),이상진(S. J Lee),전재억(J. U. Jun),곽재섭(J. S. Kwak),하만경(M. K. Ha) 한국기계가공학회 2006 한국기계가공학회 춘추계학술대회 논문집 Vol.2006 No.-
When designing an engine part the designer has to choose the proper material and to define the dimensions of the part. in the most rudimentary case he has available as guidelines the collective experience from similar applications. The performance of the part is tested on occasion of the trial runs for the full system, and possibly occurring deficiencies are corrected until a satisfactory usable life and safety of operation is achieved. This procedure is time consuming and costly, and the learning effect is minimal. These requirements have to be condensed into characteristic values ameanable to computation. Since testing and computation are complementary we have to look at the currently existing mathematical models for engine bearing performance.
재순환유동 예측을 위한 k-ɛ 난류모델 개선에 대한 연구
이영모(Y.M. Lee),김철완(C.W. Kim) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.2
The standard k-ɛ and realizable k-ɛ models are adopted to improve the prediction performance on the recirculating flow. In this paper, the backward facing step flows are used to assess the prediction performance of the recirculation zone. The model constants of turbulence model are obtained by the experimental results and they have a different value according to the flow. In the case of an isotropic flow situation, decaying of turbulent kinetic energy should follow a power law behavior. In accordance with the power law, the coefficients for the dissipation rate of turbulent kinetic energy are not universal. Also, the other coefficients as well as the dissipation coefficient are not constant. As a result, a suitable coefficients can be varied according to each of the flow. The changes of flow over the backward facing step in accordance with model constants of the k-ɛ models show that the reattachment length is dependent on the growth rate(λ) and the k-ɛ models can be improved the prediction performance by changing the model constants about the recirculating flow. In addition, it was investigated for the curvature correction effect of the k-ɛ models in the recirculating flow. Overall, the curvature corrected k-ɛ models showed an excellent prediction performance.