Robust Design Optimization of Hydrodynamic Characteristics of Airfoil 791

Chenghu ZHANG,Binjuan ZHAO,Zhongfu HUANG,Yanxia FU,Qi LIU,Huilong CHEN 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.3

In this paper, the influence of the continuous random variation of the flow velocity on hydrodynamic characteristics of airfoil 791 was discussed, and a robust design optimization method was proposed to reduce the influence of uncertain factors on the stability of hydrodynamic performance. Firstly, Bezier curve was used to parameterize the suction side of the airfoil, and its thickness was controlled by four points, which was then taken as the optimization variables. Secondly, the criterion of robustness was given, and then a robust mathematical model was established. Finally, two objective functions of robust optimization were gained on the basis of uncertainty analysis with surrogate model. Combined with multi-objective genetic algorithm, a robust optimal solution with better hydrodynamic characteristics was obtained. The results showed that compared with original case, the thickness near trailing edge altered more smoothly, the resistance and surface wave intensity were obviously decreased, and the maximum reduction of drag-lift ratio and wake unevenness were 6.89% and 25.04% respectively, which contributed to the improvement of wake quality. The change of surface pressure and resistance coefficients were also more stable under the variable inlet flow velocity conditions, and then the robustness was strengthened accordingly. In conclusion, the robust design optimization can obviously improve the hydrodynamic characteristics of the airfoil while reducing the sensitivity to uncertain factors, meanwhile, it can provide better stability during the operating process.

A novel lattice structure topology optimization method with extreme anisotropic lattice properties

Zhang Chenghu,Liu Jikai,Yuan Zhiling,Xu Shuzhi,Zou Bin,Li Lei,Ma Yongsheng 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.5

This research presents a lattice structure topology optimization (LSTO) method that significantly expands the design space by creating a novel candidate lattice that assesses an extremely large range of effective material properties. About the details, topology optimization is employed to design lattices with extreme directional tensile or shear properties subject to different volume fraction limits and the optimized lattices are categorized into groups according to their dominating properties. The novel candidate lattice is developed by combining the optimized elementary lattices, by picking up one from each group, and then parametrized with the elementary lattice relative densities. In this way, the LSTO design space is greatly expanded for the ever increased accessible material property range. Moreover, the effective material constitutive model of the candidate lattice subject to different elementary lattice combinations is pre-established so as to eliminate the tedious in-process repetitive homogenization. Finally, a few numerical examples and experiments are explored to validate the effectiveness of the proposed method. The superiority of the proposed method is proved through comparing with a few existing LSTO methods. The options of concurrent structural topology and lattice optimization are also explored for further enhancement of the mechanical performance.

A Novel Low-cost Thin-film Flat Plate Photobioreactor for Microalgae Cultivation

Chenghu Yan,Qinghua Zhang,Shengzhang Xue,Zhongliang Sun,Xia Wu,Zhihui Wang,Yunming Lu,Wei Cong 한국생물공학회 2016 Biotechnology and Bioprocess Engineering Vol.21 No.1

In this study, a novel thin-film flat plate photobioreactor (FPPBR) mounted with baffles and a 61.2 m2 (2,000 L) photobioreactor system based on the FPPBR were developed. The flow of the fluid in the thinfilm photobioreactor was investigated by means of computational fluid dynamics (CFD). The cultivation of Chlorella sp. and Scenedesmus dimorphus in the thin-film FPPBR was carried out outdoors. The results showed that the flow of culture medium in different channels was uniform. In outdoor cultivation, the biomass productivity in the FPPBR with baffles was 25.2% higher than that in the FPPBR without baffles. In the pilot-scale FPPBR system, the maximum area productivity of Scenedesmus dimorphus reached 21.9 g/m2/day. When the service time of the photobioreactor was 1 and 3 years, the capital cost of the photobioreactor was 4.72 and 2.45 $ kgalgae, respectively. The results demonstrated that the thin-film FPPBR was cost effective, and it has the potential to be used for mass cultivation of microalgae.

Design Improvement of the Splitter Blade in the Centrifugal Pump Impeller Based on Theory of Boundary Vorticity Dynamics

ZHAO, Binjuan,ZHANG, Chenghu,ZHAO, Youfei,FU, Yanxia,LIU, Qi,CHEN, Huilong Korean Society for Fluid machinery 2018 International journal of fluid machinery and syste Vol.11 No.1

To improve the design of the splitter blade in the centrifugal pump impeller, inner flow numerical simulations are performed on the centrifugal pump impeller without splitter blades firstly, inner flow diagnoses are performed based on the theory of the boundary vorticity dynamics, and distributions of the boundary vorticity flux (BVF), friction force as well as vorticity on the inner walls of the impeller are carefully analyzed to find the location of bad flows and their dynamic sources. Later, according to the inner flow diagnosis results, splitter blades are designed and reformed for the original impeller. The inner flow filed in the impellers equipped with the preliminary splitter blade and reformed splitter blade are numerically simulated and diagnosed. Finally, comparisons are made among the three impellers, and it is found that, compared to the original impeller (impeller 0), the BVF, friction force and vorticity distribution in the impeller equipped with the preliminary splitter blade (impeller 1) has no obvious improvement, although the pump head increases, the efficiency decreases; the BVF, friction force and vorticity distribution in the impeller equipped with the reformed blade (impeller 2) has improved obviously, BVF peak decreases evidently and BVF distributes more uniformly, flow separation is inhibited, the hydraulic force acting on the impeller increases, with the pump head and efficiency increasing dramatically. It is proven that, flow diagnosis based on the theory of the boundary vorticity dynamics is an effective supplemental way for the design of the splitter blade in the centrifugal pump impeller, and will provide reference for the design of other turbo machinery as well.

Design Improvement of the Splitter Blade in the Centrifugal Pump Impeller Based on Theory of Boundary Vorticity Dynamics

Binjuan ZHAO,Chenghu ZHANG,Youfei ZHAO,Yanxia FU,Qi LIU,Huilong CHEN 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.1

To improve the design of the splitter blade in the centrifugal pump impeller, inner flow numerical simulations are performed on the centrifugal pump impeller without splitter blades firstly, inner flow diagnoses are performed based on the theory of the boundary vorticity dynamics, and distributions of the boundary vorticity flux (BVF), friction force as well as vorticity on the inner walls of the impeller are carefully analyzed to find the location of bad flows and their dynamic sources. Later, according to the inner flow diagnosis results, splitter blades are designed and reformed for the original impeller. The inner flow filed in the impellers equipped with the preliminary splitter blade and reformed splitter blade are numerically simulated and diagnosed. Finally, comparisons are made among the three impellers, and it is found that, compared to the original impeller (impeller 0), the BVF, friction force and vorticity distribution in the impeller equipped with the preliminary splitter blade (impeller 1) has no obvious improvement, although the pump head increases, the efficiency decreases; the BVF, friction force and vorticity distribution in the impeller equipped with the reformed blade (impeller 2) has improved obviously, BVF peak decreases evidently and BVF distributes more uniformly, flow separation is inhibited, the hydraulic force acting on the impeller increases, with the pump head and efficiency increasing dramatically. It is proven that, flow diagnosis based on the theory of the boundary vorticity dynamics is an effective supplemental way for the design of the splitter blade in the centrifugal pump impeller, and will provide reference for the design of other turbo machinery as well.

The Role of Social Media in Financial Risk Prediction: Evidence from China

Zheng Li,Qi Wang,Chenghu Zhang 한국증권학회 2022 한국증권학회지 Vol.51 No.4

In this paper, we develop an intelligent approach to detect default risk of FinTech lending platforms. Using China’s peer-to-peer (P2P) lending market as an empirical application, we assemble a unique dataset of matched default and non-default platforms. We apply state-of-art techniques to extract sentiment and topic features from several stakeholders’ social media data, which are used as supportive soft information. Our approach exhibits better predictive abilities than those with hard information only, where the value of dynamic soft information is demonstrated. Our approach serves as a proof of concept to complement traditional methods of financial risk prediction.