APPROXIMATION OF SOLUTIONS FOR GENERALIZED WIENER-HOPF EQUATIONS AND GENERALIZED VARIATIONAL INEQUALITIES

Guanghui Gu,Yongfu Su 한국전산응용수학회 2010 Journal of applied mathematics & informatics Vol.28 No.1

The purpose of this article is to introduce a new generalized class of the Wiener-Hopf equations and a new generalized class of the variational inequalities. Using the projection technique, we show that the generalized Wiener-Hopf equations are equivalent to the generalized variational inequalities. We use this alternative equivalence to suggest and analyze an iterative scheme for finding the solution of the generalized Wiener-Hopf equations and the solution of the generalized variational inequalities. The results presented in this paper may be viewed as significant and improvement of the previously known results. In special, our results improve and extend the resent results of M.A. Noor and Z.Y.Huang[M.A. Noor and Z.Y.Huang, Wiener-Hopf equation technique for variational inequalities and nonexpansive mappings, Appl. Math. Comput.(2007), doi:10.1016/j.amc.2007.02.117 ].

APPROXIMATION OF SOLUTIONS FOR GENERALIZED WIENER-HOPF EQUATIONS AND GENERALIZED VARIATIONAL INEQUALITIES

Gu, Guanghui,Su, Yongfu The Korean Society for Computational and Applied M 2010 Journal of applied mathematics & informatics Vol.28 No.1

The purpose of this article is to introduce a new generalized class of the Wiener-Hopf equations and a new generalized class of the variational inequalities. Using the projection technique, we show that the generalized Wiener-Hopf equations are equivalent to the generalized variational inequalities. We use this alternative equivalence to suggest and analyze an iterative scheme for finding the solution of the generalized Wiener-Hopf equations and the solution of the generalized variational inequalities. The results presented in this paper may be viewed as significant and improvement of the previously known results. In special, our results improve and extend the resent results of M.A. Noor and Z.Y.Huang[M.A. Noor and Z.Y.Huang, Wiener-Hopf equation technique for variational inequalities and nonexpansive mappings, Appl. Math. Comput.(2007), doi:10.1016/j.amc.2007.02.117].

2-(2-Cyanopropyl) Dithiobenzoate-mediated Grafting Polymerization of Methyl Methacrylate from Vinyl Modified Silica

Deling Li,Guanghui Li,Qing Zhang,Guixian Su,Hongxia Zhang 한국고분자학회 2016 폴리머 Vol.40 No.4

Grafting polymerization of methyl methacrylate (MMA) from vinyl modified silica mediated by 2-(2-cyanopropyl) dithiobenzoate was first conducted. Surface radicals generated by the addition reaction of “free” polymeric radicals with surface vinyl could initiate reversible addition-fragmentation chain transfer (RAFT) grafting polymerization of MMA from silica. The RAFT grafting polymerization of MMA from silica exhibited a living character, evident from the linear relationship of grafting ratio with monomer conversion. Grafting polymerization rate appeared dependent on target molecular weight and initiator concentration because of diffusion-controlled RAFT process on silica. The PMMA-grafted silica allowed for a second-step grafting polymerization due to the existence of dithioester group on the chain ends of grafted PMMA. In this case, surface radicals were generated by the reaction of “free” polymeric radicals with the surface RAFT agents, which differed from the RAFT process of grafting polymerization from vinyl modified silica. This method could be extended to prepare a variety of block copolymers from silica.

Thermal-fluid-structure coupling analysis for plate-type fuel assembly under irradiation. Part-I numerical methodology

Li, Yuanming,Yuan, Pan,Ren, Quan-yao,Su, Guanghui,Yu, Hongxing,Wang, Haoyu,Zheng, Meiyin,Wu, Yingwei,Ding, Shurong Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.5

The plate-type fuel assembly adopted in nuclear research reactor suffers from complicated effect induced by non-uniform irradiation, which might affect its stress conditions, mechanical behavior and thermal-hydraulic performance. A reliable numerical method is of great importance to reveal the complex evolution of mechanical deformation, flow redistribution and temperature field for the plate-type fuel assembly under non-uniform irradiation. This paper is the first part of a two-part study developing the numerical methodology for the thermal-fluid-structure coupling behaviors of plate-type fuel assembly under irradiation. In this paper, the thermal-fluid-structure coupling methodology has been developed for plate-type fuel assembly under non-uniform irradiation condition by exchanging thermal-hydraulic and mechanical deformation parameters between Finite Element Model (FEM) software and Computational Fluid Dynamic (CFD) software with Mesh-based parallel Code Coupling Interface (MpCCI), which has been validated with experimental results. Based on the established methodology, the effects of non-uniform irradiation and fluid were discussed, which demonstrated that the maximum mechanical deformation with irradiation was dozens of times larger than that without irradiation and the hydraulic load on fuel plates due to differential pressure played a dominant role in the mechanical deformation.

Code development and preliminary validation for lead-cooled fast reactor thermal-hydraulic transient behavior

Wang Chenglong,Wang Chen,Tian Wenxi,Su Guanghui,Qiu Suizheng 한국원자력학회 2024 Nuclear Engineering and Technology Vol.56 No.6

Lead-cooled fast reactors (LFRs) have a wide range of application scenarios, which require the thermal-hydraulic characteristics of LFRs to be reliable. In the present paper, the Lead-cooled fast reactor Thermal-Hydraulic Analysis Code LETHAC was developed, including the models of pipe, heat exchanger, and pool. To verify the correctness of LETHAC, two experimental facilities and three experimental cases were selected, including GFT and PLOFA tests for NACIE-UP and Test-1 for CIRCE. The calculated results show the same and consistent trend with the experimental data, but there are some discrepancies. It can be found that LETHAC is suitable and reliable in predicting the transient behavior of lead-cooled system.

Thermal-fluid-structure coupling analysis on plate-type fuel assembly under irradiation. Part-II Mechanical deformation and thermal-hydraulic characteristics

Li, Yuanming,Ren, Quan-yao,Yuan, Pan,Su, Guanghui,Yu, Hongxing,Zheng, Meiyin,Wang, Haoyu,Wu, Yingwei,Ding, Shurong Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.5

The plate-type fuel assembly adopted in nuclear research reactor suffers from complicated effect induced by non-uniform irradiation, which might affect stress conditions, mechanical behaviors and thermal-hydraulic performance of the fuel assembly. This paper is the Part II work of a two-part study devoted to analyzing the complex unique mechanical deformation and thermal-hydraulic characteristics for the typical plate-type fuel assembly under irradiation effect, which is on the basis of developed and verified numerical thermal-fluid-structure coupling methodology under irradiation in Part I of this work. The mechanical deformation, thermal-hydraulic performance and Mises stress have been analyzed for the typical plate-type fuel assembly consisting of support plates under non-uniform irradiation. It was interesting to observe that: the plate-type fuel assembly including the fuel plates and support plates tended to bend towards the location with maximum fission rate; the hot spots in the fuel foil appeared at the location with maximum thickness increment; the maximum Mises stress of fuel foil was located at the adjacent location with the maximum plate thickness increment et al.

Experimental investigation on heat transfer of nitrogen flowing in a circular tube

Chenglong Wang,Yuliang Fang,Wenxi Tian,Guanghui Su,Suizheng Qiu Korean Nuclear Society 2024 Nuclear Engineering and Technology Vol.56 No.2

Average and local convective heat transfer coefficients of nitrogen are measured experimentally in an electrically heated circular tube for a range of Reynolds number from 1.08 × 10⁴ to 3.60 × 10⁴, and wall-to-bulk temperature ratio from 1.01 to 1.77. The exit Mach number is up to 0.17, and the heat flux is up to 46 kW·m^-2. The molybdenum test section has a 62 diameters heated section with an inside diameter of 5 mm and a 30 diameters entrance section to ensure the fully-developed flow. Uncertainty of Nusselt number is less than 1.6 % in this study. The results indicate that the average heat transfer correlations evaluated by both the bulk and the modified film Reynolds numbers agree well with the experimental data. The local heat transfer results based on bulk properties are compared with previous empirical correlations. New prediction correlations are recommended which are significantly affected by the property variation and heated length. The comparison between the proposed correlations and experimental points shows that 88 % of experimental data fall into an error of 10 %, and almost all data are within an error of 20 %.

Prediction of flow boiling heat transfer coefficient in horizontal channels varying from conventional to small-diameter scales by genetic neural network

Jing Zhang,Yichao Ma,Mingjun Wang,Dalin Zhang,Suizheng Qiu,Wenxi Tian,Guanghui Su 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.8

Three-layer back propagation network (BPN) and genetic neural network (GNN) were developed in this study to predict the flow boiling heat transfer coefficient (HTC) in conventional and small-diameter channels. The GNN has higher precision than BPN (with root mean square errors of 17.16% and 20.50%, respectively) and other correlations. The inputs include vapor quality x, mass flux G, heat flux q, diameter D and physical parameter φ, and the predicted flow boiling HTC is set as the outputs. Influences of input parameters on the flow boiling HTC are discussed based on the trained GNN: nucleate boiling promoted by a larger saturated pressure, a larger heat flux and a smaller diameter is dominant in small channels; convective boiling improved by a larger mass flux and a larger vapor quality is more significant in conventional channels. The HTC increases with pressure both in conventional and small channels. The HTC in conventional channels rises when mass flux increases but remains almost unaffected in small channels. A larger heat flux leads to the HTC growth in small channels and an increase of HTC was observed in conventional channels at a higher vapor quality. HTC increases inversely with diameter before dry out.

Numerical study of laminar flow and friction characteristics in narrow channels under rolling conditions using MPS method

Muhammad Abdul Basit,Wenxi Tian,Ronghua Chen,Suizheng Qiu,Guanghui Su 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.8

Modern small modular nuclear reactors can be built on a barge in ocean, therefore, their flow charac-teristics depend upon the ocean motions. In the present research, effect of rolling motion on flow and friction characteristics of laminar flow through vertical and horizontal narrow channels has been studied. A computer code has been developed using MPS method for two-dimensional Navier-Stokes equations with rolling motion force incorporated. Numerical results have been validated with the literature and have been found in good agreement. It has been found that the impact of rolling motions on flow characteristics weakens with increase in flow rate and fluid viscosity. For vertical narrow channels, the time averaged friction coefficient for vertical channels differed from steady friction coefficient. Furthermore, increasing the horizontal distance from rolling pivot enhanced the flow fluctuations but these stayed relatively unaffected by change in vertical distance of channel from the rolling axis. For horizontal narrow channels, the flow fluctuations were found to be sinusoidal in nature and their magnitude was found to be dependent mainly upon gravity fluctuations caused by rolling.

Molecular dynamics study of liquid sodium film evaporation and condensation by Lennard-Jones potential

Wang Zetao,Guo Kailun,Wang Chenglong,Zhang Dalin,Tian Wenxi,Qiu Suizheng,Su Guanghui 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8

Deeply understanding the phase change of thin liquid sodium film inside wick pore is very important for further studying high-temperature sodium heat pipe's heat transfer. For the first time, the evaporation and condensation of thin liquid sodium film are investigated by the Lennard-Jones potential of molecular dynamics. Based on the startup and normal operation of the sodium heat pipe, three different cases are simulated. First, the equilibrium is achieved and the Mass Accommodation Coefficients of the three cases are 0.3886, 0.2119, 0.2615 respectively. Secondly, the non-equilibrium is built. The change of liquid film thickness, the number of gas atoms, the net evaporation flux (Jnet), the heat transfer coefficient (h) at the liquid-gas interface are acquired. Results indicate that the magnitude of the Jnet and the h increase with the basic equilibrium temperature. In 520e600 K (the startup of the heat pipe), the h has approached 5 e6Wm2 K1 while liquid film thickness is in 11e13 nm. The fact shows that during the initial startup of the sodium heat pipe, the thermal resistance at the liquid-gas interface can't be negligible. This work is the complement and extension for macroscopic investigation of heat transfer inside sodium heat pipe. It can provide a reference for further numerical simulation and optimal design of the sodium heat pipe in the future.