3D numerical investigation on flow boiling characteristics in large length-to-diameter ratio microchannelHuang, Zhen; Chen, Li; Peng, Xiaohai; Wang, Songchao; Zhao, Dan; Zhao, Changying; Liu, Gang
doi: 10.1088/1742-6596/2599/1/012024pmid: N/A
To meet the demand of thermal management with large power and high heat flux in the future engineering applications, more and more attentions have been draw to develop the two-phase microchannel cooling technology. In this work, a three dimensional numerical investigation is performed to study the influence of mass flux and heat flux on the two phase flow boiling characteristics in a single microchannel with large length-to-diameter ratio. The related calculation results show that the Volume of Fluid (VOF) model coupled with Lee model can predict the two phase pressure drop and heat transfer coefficient of the microchannel well. And the flow patterns in the microchannel are classified as bubbly flow, slug flow and annular flow, which can be captured by this numerical model precisely. Besides, the transient pressure drop augments with the increase of mass flux. But the effect of mass flux on the amplitude of quasi-steady pressure drop and the peak value of time-averaged heat transfer coefficient along the microchannel is small. At last, the amplitude of quasi-steady pressure drop increases with the augmentation of heat flux. The maximum and fully developed time-averaged heat transfer coefficients along the microchannel increase with the heat flux.
Prefacedoi: 10.1088/1742-6596/2599/1/011001pmid: N/A
2023 the 7th International Conference on Fluid Mechanics and Industrial Applications (FMIA 2023) included original and peer-reviewed research papers and held on May 27-28, 2023 in Taiyuan, China. FMIA 2023 is co-organized by Northeast Petroleum University, Huazhong University of Science and Technology, Chongqing University, and sponsored by China Wanxiang Group Research Institute, Asian Union of Information Technology. It was attended by academicians, researchers, entrepreneurs, government agencies and policy-makers, postgraduates.FMIA is an annual international conference devoted to the discussion of recent developments and applications of parallel computing in the field of fluid mechanics, CFD, fluid power, fluid flow and related disciplines. The field of fluid mechanics is vast and covers numerous and diverse applications. The conference covered a wide range of topics, including basic formulations and their computer modelling as well as the relationship between experimental and analytical results. The meeting provided a forum for discussing new work on fluid mechanics and in particular for promoting the interchange of novel ideas and the presentations of the latest developments in this field. This conference would also provide an ideal environment to develop new collaborations and meet experts on the fundamentals, applications, and products of the mentioned fields.This two-day conference was organized in technical association with the Asian Union of Information Technology and included invited keynote talks and oral paper presentations from both academia and industry. The topics covered in this FMIA 2022 are: 1. Aerodynamics; 2. Thermodynamics and Heat Transfer; 3. Fluid Theory and Related Algorithms. Each keynote speakers lasted for 30 minutes, including 5 minutes for Q&A. and for other sessions, there was 20 minutes for each presentation, including 5 minutes for Q&A. The book is useful to professionals and scientists involved or interested in fluid mechanics and industrial applications. Hopefully, all participants and other interested readers would benefit scientifically from the proceedings and also find it stimulating in the process.We would like to thank all the author submitted papers to this FMIA 2023 and thank all the reviewers for their time and effort in reviewing articles. Especially we would like to thank the organizing committee for their valuable advices in the organization and helpful peer review of the papers.Conference Organizing Committee,Wuhan, ChinaList of Committees are available in this pdf.
Influence of parameterization method and optimization algorithm on airfoil optimizationZhou, Jinxin; Jia, Hongyin; Wu, Xiaojun; Zhang, Peihong; Yu, Jing; Zhou, Guiyu; Chen, Bing; Luo, Lei; Mo, Tao; Jiang, Anlin
doi: 10.1088/1742-6596/2599/1/012005pmid: N/A
In this study, the impact of parameterization methods and optimization algorithms on the optimization results of the RAE2822 airfoil is examined. Specifically, how variations in the number of design variables, spacing of control points, the scaling scale of the objective function, and line search step of different FFD parameterization methods affect the resistance convergence process are investigated. The results indicate that the number of design variables and the spacing of control points play a significant role in the speed and minimum value of resistance convergence. In contrast, the scaling scale of the objective function and the line search step has a relatively minor impact on resistance optimization.
Influence of hydrodynamic retarder blade angle on vortex structureWang, Yuze; Wei, Wei; An, Yuanyuan; Tao, Tianlang; Yan, Qingdong
doi: 10.1088/1742-6596/2599/1/012026pmid: N/A
The internal flow of the hydrodynamic retarder cavity is a complex three-dimensional turbulent flow, and the evolution of vortices in its internal two-phase flow field is closely related to the generation of braking torque and the dissipation of kinetic energy. In this study, a periodic flow channel model is used to investigate the influence of different blade angles on vortex structure characteristics. The vortex structure identification method with Q criterion is employed to compare and analyze the distribution and development of the vortex structure. Particle image velocimetry (PIV) tests are conducted to observe the evolution of the vortex structure inside the retarder and validate the simulation analysis. Results show that the increase of the vortex structure scale, intensity, and transformation speed caused by the increase of the blade angle, which affects the energy dissipation and transfer of the flow field and explains the reason for the change of the braking torque. This provides a theoretical basis for the study of the braking performance mechanism and design optimization of the hydrodynamic retarder.
Numerical simulation of the effect of elastic deformation on the fairing separation processWang, Hao; Hong, Junwu; Meng, Dehong; Li, Wei; Yue, Hao
doi: 10.1088/1742-6596/2599/1/012007pmid: N/A
In view of the potential impact of structural deformation on the separation safety of elastic fairing at low altitude and high speed, the aerodynamic/deformation/motion coupling analysis method is established. The numerical simulation of the separation process of the fairing considering elastic deformation after disengaging is carried out. The motion characteristics and structural response characteristics of the elastic fairing in the separation process are obtained. Moreover, the impact of elastic deformation on the attitude and trajectory of the fairing is studied. The results indicate that the elastic deformation has an impact on the attitude and trajectory of the fairing after hinge decoupling. However, for the calculation conditions in this paper, elastic deformation has no subversive effect on the separation safety.
A fractional derivative aerodynamic model at high angles of attackYu, Jing; Wu, Xiaojun; Liu, Shenshen; Kong, Yinan; Hao, Dong
doi: 10.1088/1742-6596/2599/1/012003pmid: N/A
A fractional derivative aerodynamic model is put forward based on Grünwald-Letnikov fractional derivative in this paper. In order to express the hysteresis property of aerodynamic coefficients, a fractional derivative state-space equation is developed from Goman’s differential equation. A fast and high-accuracy calculation method of Grünwald-Letnikov fractional derivative is proposed. Then, the model is demonstrated by several experiments data from literatures. The simulation results show that the presented fractional derivative aerodynamic model can preferably express the nonlinear unsteady aerodynamic characteristics of airfoils and aircrafts. The proposed modelling framework is meaningful to the designation of flight and control system.
Flow Characteristic Study on Wake Flow of High-speed vehiclesZhou, Guiyu; Zhang, Jie; Yang, Yueyue; Chen, Hongyang; Mo, Tao; Liu, Liang; Jia, Chuan; Jiang, Anlin; Chen, JianJun; Cui, Pengcheng
doi: 10.1088/1742-6596/2599/1/012001pmid: N/A
Based on the general CFD software NNW-FlowStar of national numerical wind tunnel engineering, this paper adopts anisotropic unstructured hybrid mesh to simulate the wake field characteristics of aircraft in high-speed flight. NNW-FlowStar software in high resolution numerical format, gaussian type node gradient calculation method, massively parallel and a series of numerical algorithm in terms of development and improvement to ensure the fine simulation of the hypersonic flow field. The numerical method can clearly aircraft wake flow field, the main shock, the corner expansion area, shear layer and the shock wave, clearly shows the wake flow field structure. With the increase of Mach number, the wake flow is getting more and more strong, the backwater area range is more and more small, after the stagnation point, the shock wave is also much greater compressibility.
Study on the mechanism and simulation of slurry diffusion in fractured rock mass based on detour effectLu, Guozhi; Ni, Ping; Hu, Fei
doi: 10.1088/1742-6596/2599/1/012040pmid: N/A
The grout diffusion law and grouting effect of fractured rock mass are affected by the roundabout effect. In this paper, based on the power law fluid theory, the formula of slurry diffusion mechanism in fractured rock mass considering the circuitous effect is derived; Further, based on COMSOL numerical simulation software, the influence of grouting pressure and grouting time on the slurry diffusion range is studied; Finally, through comparative analysis, the correctness and feasibility of the theoretical analysis are verified based on the numerical simulation results. The research results can provide theoretical reference and technical support for the design and construction of grouting engineering.
Numerical Simulation of Supercritical Carbon Dioxide Dry Gas SealCao, Yue; Jin, Jian; Chang, Yinhui; Wang, Xiaojing
doi: 10.1088/1742-6596/2599/1/012014pmid: N/A
A theoretical model of the dry gas seal (DGS) was established, considering real gas, inertia, turbulence, and choked flow effects. The steady-state performance of supercritical carbon dioxide DGSs under high-pressure and high-speed operating conditions was analyzed. The results show that: the increase in groove depth will result in higher opening force and leakage; the opening force and leakage initially increase and then decrease with the increase in the spiral angle; the opening force and leakage increase with the increase in the inlet pressure; the increasing rotation speed leads to an increase in opening force and leakage.
Numerical simulation of the leading edge bump for the cavity flowLi, Wei; Meng, Dehong; Hong, Junwu; Wang, Hao
doi: 10.1088/1742-6596/2599/1/012033pmid: N/A
Based on the IDDES method, the M219 cavity is simulated in flux-mixed scheme, with the main purpose of studying the mechanism of the noise generation in the cavity flow and proposing corresponding suppression measures. The study mainly includes the grid resolution study and the numerical simulation of the leading edge bump. Through the comparative analysis with the experimental results provided by Henshaw et al. and the LES results from Haase et al. it is known that the different grids in this paper can all obtain the flow characteristics of the cavity flow, and the different grids show the convergence. The leading edge bump can significantly raise the shear layer, reduce the disturbance flowing into the cavity, and play a role in suppressing both the cavity tones and the broadband of the cavity flow.