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辐射加热颗粒槽道湍流两相流的相间传热特性

Acta Mechanica Sinica 2024年第2期40卷 54-64页

作者：唐晓峰潘明杨文武董宇红 Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai UniversityShanghai200072China Shanghai Key Laboratory of Mechanics in Energy Engineering and Shanghai Institute of Aircraft Mechanics and Control Shanghai200072China

本文采用直接数值模拟方法结合拉格朗日点-粒模型研究了携带辐射热惯性颗粒的竖直槽道湍流两相流相间传热特性.研究中采用双向耦合模型描述分散相颗粒与流体之间的动量交换和热交换,辐射强度和颗粒Stokes数范围分别为1≤q/q0≤20,0.36×... 详细信息

本文采用直接数值模拟方法结合拉格朗日点-粒模型研究了携带辐射热惯性颗粒的竖直槽道湍流两相流相间传热特性.研究中采用双向耦合模型描述分散相颗粒与流体之间的动量交换和热交换,辐射强度和颗粒Stokes数范围分别为1≤q/q0≤20,0.36×10^(−1)≤Stf≤2.16×10^(−1).研究发现辐射加热颗粒对流体的动力学调制加速了流体运动,使湍流强度增大.高辐射下的小Stokes数颗粒能显著加热流体.我们从流场时均温度方程出发,导出了两相流系统中相间传热Nusselt数的理论表达式,理论分析表明相间传热引起冷板和热板Nusselt数的差异,并进一步得到了相间传热效率与颗粒Stokes数及颗粒所受辐射强度的标度关系.

关键词：加热流体 Stokes数传热效率辐射加热辐射强度直接数值模拟拉格朗日点理论表达式

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多孔介质传热模型在多孔壁湍流中的适用性

空气动力学学报 2024年第1期42卷 45-54,I0001页

作者：赵泽灏张金龙董宇红上海大学力学与工程科学学院上海市应用数学和力学研究所上海200072 上海市能源工程力学重点实验室上海飞行器力学与控制研究院上海200072

为了考查不同的多孔介质传热模型在不同工况下的适用性,对带有高孔隙率多孔介质壁面槽道湍流及其传热进行了直接数值模拟研究。在多孔介质层外流体区域,通过有限差分方法求解不可压缩Navier-Stokes方程和温度对流扩散方程;在多孔介质层... 详细信息

为了考查不同的多孔介质传热模型在不同工况下的适用性,对带有高孔隙率多孔介质壁面槽道湍流及其传热进行了直接数值模拟研究。在多孔介质层外流体区域,通过有限差分方法求解不可压缩Navier-Stokes方程和温度对流扩散方程;在多孔介质层内,使用修正的Darcy-Brinkman-Forchheimer模型描述高孔隙率多孔介质阻力,以及分别采用局部热平衡(local thermal equilibrium,LTE)模型、局部非热平衡(local thermal non-equilibrium,LTNE)模型、理想金属(ideal metal foams,IMF)模型计算温度分布。通过对所得热场的统计特性的分析比较,探究了不同Biot数下水和空气两类流体介质的多孔介质传热模型的有效性。研究表明:LTE模型不足以准确预测金属泡沫多孔介质内传热问题,其等效导热系数因仅考虑孔隙率因素而低估了多孔介质层的传热能力;IMF模型在小比热容流体介质的算例中表现良好,可以代替LTNE描述多孔介质层内的传热,而在大比热容流体介质的算例中表现不佳,需要考虑比热容以及流固两相间的传热能力对预估的固体相温度分布进行修正。

关键词：传热多孔介质壁面槽道湍流直接数值模拟局部热平衡模型

分流板对圆柱绕流湍流结构演化影响的实验研究

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实验流体力学 2024年第4期38卷 75-89页

作者：周建康邱翔王伯福周全刘宇陆上海大学力学与工程科学学院上海市应用数学和力学研究所上海200072 上海应用技术大学理学院上海201418

采用粒子图像测速(Particle Image Velocimetry,PIV)技术实验研究了带分流板的圆柱绕流流动特性,分析了分流板对圆柱绕流湍流结构演化特性的影响。雷诺数为3.9×10^(3),分流板长度L与圆柱直径D之比L/D为0~2.50。实验结果表明,随着L/D从... 详细信息

采用粒子图像测速(Particle Image Velocimetry,PIV)技术实验研究了带分流板的圆柱绕流流动特性,分析了分流板对圆柱绕流湍流结构演化特性的影响。雷诺数为3.9×10^(3),分流板长度L与圆柱直径D之比L/D为0~2.50。实验结果表明,随着L/D从0增大至1.00,圆柱后方回流区长度和回流区面积显著增大;当L/D>1.00时,L/D对圆柱后方回流特性的影响较小。分流板影响圆柱绕流湍流结构的演化特性:当L/D<1.00时,分流板抑制尾涡脱落,斯特劳哈尔数Sr减小,L/D从0增大至1.00,Sr减小了26.34%。此外,圆柱尾涡在分流板后缘诱导形成旋转方向相反的二次涡,二次涡沿分流板向上游运动。1.00≤L/D<2.00时,分流板作用于圆柱尾涡,尾涡发生破碎,形成一些小尺度尾涡。L/D≥2.00时,尾涡附着于分流板上,二次涡主要分布于圆柱后方。随着L/D增大,分流板减小了圆柱后方的湍流脉动强度。

关键词：圆柱绕流分流板尾涡二次涡粒子图像测速

A rescaling algorithm for multi-relaxation-time lattice Boltzmann method towards turbulent flows with complex configurations

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Applied Mathematics and Mechanics(English Edition) 2023年第9期44卷 1597-1612页

作者： Haoyang LI Weijian LIU Yuhong DONG Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai UniversityShanghai 200444China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai UniversityShanghai 200072China Shanghai Frontier Science Center of Mechanoinformatics Shanghai UniversityShanghai 200072China Shanghai Institute of Aircraft Mechanics and Control Shanghai 200092China

Understanding and modeling flows over porous layers are of great industrial *** accurately solve the turbulent multi-scale flows on complex configurations,a rescaling algorithm designed for turbulent flows with the Chapman-Enskog analysis is *** mesh layout and the detailed rescaling procedure are also *** numerical simulations(DNSs)for a turbulent channel flow and a porous walled turbulent channel flow are performed with the three-dimensional nineteen-velocity(D3Q19)multiple-relaxation-time(MRT)lattice Boltzmann method(LBM)to validate the accuracy,adaptability,and computational performance of the present rescaling *** results,which are consistent with the previous DNS studies based on the finite difference method and the LBM,demonstrate that the present method can maintain the continuity of the macro values across the grid interface and is able to adapt to complex *** reasonable time consumption of the rescaling procedure shows that the present method can accurately calculate various turbulent flows with multi-scale and complex configurations while maintaining high computational efficiency.

关键词： slattice Boltzmann method(LBM) direct numerical simulation(DNS) rescaling algorithm complex configuration

Coupling framework for a wind speed forecasting model applied to wind energy

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Science China(Technological Sciences) 2022年第10期65卷 2462-2473页

作者： DENG Ying CHONG KaiLeong WANG BoFu ZHOU Quan LU ZhiMing Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai 200072China

Wind energy is the burgeoning renewable energy. Accurate wind speed prediction is necessary to ensure the stability and reliability of the power grid for wind energy. This study focuses on developing a novel hybrid forecasting model to tackle adverse effects caused by strong variability and abrupt changes in wind speed. The hybrid model combines data decomposition and error correction strategy for a wind speed forecasting model applied to wind energy. First, wavelet packet decomposition is applied to wind speed series to obtain stationary subseries. Next, outlier robust extreme learning machine is implemented to predict subseries. Finally, an error correction strategy coupled with data decomposition is designed to repair preliminary prediction results. In addition, four measured datasets from China and USAwind farms with different time intervals are used to evaluate the performance of the proposed approach. Experimental analysis indicates that the proposed model outperforms the compared models. Results show that(1) the prediction accuracy of the proposed model is remarkably improved compared with other conventional models;(2) the proposed model can reduce the influence of the end effect in the decomposition-based forecasting model;(3) the coupling framework is successful for enhancing performance of hybrid forecasting model.

关键词： wind speed forecasting artificial intelligence hybrid model data preprocessing error correction wavelet packet decomposition

Tuning turbulent convection through rough element arrangement

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Journal of Hydrodynamics 2022年第2期34卷 308-314页

作者： Jian-zhao Wu Dao-liang Dong Bo-fu Wang Yu-hong Dong Quan Zhou Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai Key Laboratory of Mechanics in Energy EngineeringShanghai UniversityShanghai200072China

The tuning of turbulent Rayleigh-Bénard(RB)convection in a box is realized numerically by designed rough element *** the nonlinear dynamics of the thermal turbulence system,five models with rough elements of different widths and the same height are proposed to tune the fluid flow heat-transport *** simulations are performed using spectral element method for Rayleigh number in the range 10^(6)≤Ra≤10^(9) and a fixed Prandtl number Pr=*** is found that heat transport is enhanced for large roughness widths as the interaction between the large-scale circulation and secondary flows inside the cavity regions between the rough elements promotes the eruptions of thermal plumes,but is suppressed for small ones as more heat are trapped inside the *** all the rough models studied,different scaling exponents for the heat transport are identified and the influences of roughness arrangement on flow structure are studied.

关键词： Rayleigh-Bénard(RB)turbulence heat transport roughness arrangement

Lagrangian coherent structures and their heat-transport mechanism in the turbulent Rayleigh-Bénard convection

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Science China(Technological Sciences) 2022年第4期65卷 966-976页

作者： CHENG Hang SHEN Jie ZHANG YiZhao ZHOU Quan CHONG Kai Leong LIU YuLu LU ZhiMing Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy Engineering and School of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China The School of Sciences Shanghai Institute of TechnologyShanghai 200072China

In this paper,we investigate the Lagrangian coherent structures(LCSs)and their heat-transport mechanism in turbulent Rayleigh-Bénard(RB)*** numerical simulations(DNS)are performed in a closed square cell with Rayleigh numbers(Ra)ranging from 10^(6) to 10^(9) and Prandtl(Pr)number fixed at Pr=***,our results show the power-law relationship between Nusselt number(Nu)and Ra,Nu=0.99Ra^(0.30±0.02),confirming the results from previous *** gain insights into the material transport,LCSs are extracted using the finite-time Lyapunov exponent(FTLE)***,lobe structures are widely present,and we elucidate their role in transporting heat from the corner rolls to large-scale ***,the relationships between LCSs and thermal plumes are examined,and we identify two behaviors of thermal plumes:first,most plumes transport along the LCSs;second,few plumes are exposed to the bulk and subsequently mix with the turbulent ***,we quantify the heat flux along the LCSs,which contributes to about 85%of the total flux regardless of *** suggests that LCSs play a significant role in heat ***,the viscous(thermal)dissipation rate along the LCSs is quantified,which is larger than 80%(60%)of the total value,suggesting that LCSs are responsible for the large viscous and thermal dissipations.

关键词： Rayleigh-Bénard convection finite-time Lyapunov exponent Lagrangian coherent structures

Transport of dissolved oxygen at the sediment-water interface in the spanwise oscillating flow

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Applied Mathematics and Mechanics(English Edition) 2021年第4期42卷 527-540页

作者： Kunpeng WANG Qingxiang LI Yuhong DONG Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai Key Laboratory of Mechanics in Energy EngineeringShanghai UniversityShanghai 200072China

The distribution and concentration of dissolved oxygen(DO)play important roles in aerobic heterotroph activities and some slow chemical reactions,and can affect the water quality,biological communities,and ecosystem functions of rivers and *** this work,the transport of high Schmidt number DO at the sediment-water interface of spanwise oscillating flow is *** volume-averaged Navier-Stokes(VANS)equations and Monod equation are used to describe the flow in the sediment layer and the sediment oxygen demand of *** phase-averaged velocities and concentrations of different amplitudes and periods are *** dependence of DO transfer on the amplitude and period is analyzed by means of phase-average statistical *** is shown that the concentration in the sediment layer is positively correlated with the turbulence intensity,and the DO concentration and penetration depth in the sediment layer increases when the period and amplitude of the oscillating flow ***,in the presence of oscillating flow,a specific scaling relationship exists between the Sherwood number/oxygen consumption of aerobic heterotrophs and the Reynolds number.

关键词： dissolved oxygen(DO) turbulent channel flow oscillating flow mass transfer

The driven cavity turbulent flow with porous walls: Energy transfer, dissipation, and time-space correlations

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Journal of Hydrodynamics 2021年第4期33卷 712-724页

作者： Wen-wu Yang Bo-fu Wang Quan Zhou Yu-hong Dong Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai Key Laboratory of Mechanics in Energy EngineeringShanghai UniversityShanghai200072China

The energy transfer and dissipation as well as the turbulent structures in a lid-driven cavity flow with porous walls are investigated via the lattice Boltzmann method, with direct numerical simulation (DNS) for an isothermal incompressible flow for which the Reynolds number (Re) is 50 000. A generalized Navier-Stokes equation with the Brinkman-Forchheimer-extended Darcy model is implemented, in which the presence of permeable walls is taken into account. This study focuses on the modulations of the flow field due to porous walls, by comparing with the results from the cavity flow bounded with smooth walls. Firstly, we derived the exact expression of the kinetic energy dissipation rate in a cavity to study the budget balance of the induced and dissipated kinetic energy. By decomposing the total kinetic energy dissipation into the componential contributions of the viscous and porous medium layer, we found that the kinetic energy dissipated in the thin porous layer occupies 37% of the total driven lid-induced kinetic energy in the present parameters. Then we found that the time-averaged kinetic energy, turbulent kinetic energy (TKE), as well as the strength of the large-scale energy-containing eddy, and secondary eddies are significantly attenuated. Furthermore, it is found that the momentum and kinetic energy transfer near the corners are vastly decreased. Finally, the space-time velocity correlation functions are also provided to examine the decorrelation property of small eddies by means of convection and distortion motions in the cavity turbulent field.

关键词： Cavity turbulent flow porous medium energy transfer dissipation time-space correlations