Journal of Turbulence最新文献_第5页

DNS predictions of NOx production in developing turbulent mixing layers with non-premixed hydrogen–air combustion 发展湍流混合层与非预混氢空气燃烧过程中NOx生成的DNS预测

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-12-02 DOI: 10.1080/14685248.2022.2156524

T. Ohta, Ryota Hirata, Yasuyuki Sakai

引用次数: 0

The myth of URANS URANS的神话

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-12-02 DOI: 10.1080/14685248.2023.2225140

Daniel Israel

引用次数: 0

A systematic study of a droplet breakup process in decaying homogeneous isotropic turbulence using a mesoscopic simulation approach 用细观模拟方法系统研究衰减均匀各向同性湍流中液滴破碎过程

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-11-20 DOI: 10.1080/14685248.2022.2146700

Jun Lai, Tao Chen, Shengqi Zhang, Zuoli Xiao, Shiyi Chen, Lianping Wang

{"title":"A systematic study of a droplet breakup process in decaying homogeneous isotropic turbulence using a mesoscopic simulation approach","authors":"Jun Lai, Tao Chen, Shengqi Zhang, Zuoli Xiao, Shiyi Chen, Lianping Wang","doi":"10.1080/14685248.2022.2146700","DOIUrl":"https://doi.org/10.1080/14685248.2022.2146700","url":null,"abstract":"ABSTRACT The breakup of a spherical droplet in a decaying homogeneous isotropic turbulence is studied by solving the Cahn–Hilliard–Navier–Stokes equations. This flow provides a great opportunity to study the interactions of turbulent kinetic energy and interfacial free energy and their effects on the breakup dynamics. Three distinct stages of droplet evolution, namely, the deformation stage, the breakup stage, and the restoration stage, are identified and then analysed systematically from several perspectives: a geometric perspective, a dynamic perspective, a global energetic perspective, and a multiscale energy transfer perspective. It is found that the ending time of the breakup stage can be estimated by the Hinze criterion. The kinetic energy of the two-phase flow during the breakup stage is found to have a power-law decay with an exponent , compared to for the single-phase flow, mainly due to the enhanced viscous dissipation generated by the daughter droplets. Energy spectra of the two-phase flow show power-law decay, with a slope between and , at high wave numbers, both in the Fourier spectral space and in the spherical harmonics space.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"23 1","pages":"567 - 614"},"PeriodicalIF":1.9,"publicationDate":"2022-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49598271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Influence of turbulent structure on the heat transfer of Rayleigh–Bénard convection with triangular roughness element 湍流结构对带有三角形粗糙度单元的Rayleigh–Bénard对流换热的影响

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-11-15 DOI: 10.1080/14685248.2022.2146125

Yuxian Xia, X. Qiu, Y. Qian

{"title":"Influence of turbulent structure on the heat transfer of Rayleigh–Bénard convection with triangular roughness element","authors":"Yuxian Xia, X. Qiu, Y. Qian","doi":"10.1080/14685248.2022.2146125","DOIUrl":"https://doi.org/10.1080/14685248.2022.2146125","url":null,"abstract":"ABSTRACT There is a widely accepted conclusion that the wall roughness do not always enhance the heat transport of the turbulent thermal convection. In this paper, the heat transfer efficiency is statistically investigated from the perspective of turbulent structure. The effect of turbulent structure on the heat transfer of Rayleigh–Bénard convection with triangular rough element on the top and bottom plates is numerically simulated by a lattice Boltzmann method. We use a clustering method to identify complex turbulent structures associated with intense events. The reduction of the Nusselt number is obtained for small roughness height H/L, while the enhancement of heat transport appears for large H/L. For the large H/L case, the positive temperature structures occupying the negative heat transfer events reduce the efficiency of the heat transfer. On the contrary, the negative temperature turbulent structures boost the heat transfer. By analyzing the conditional average field, we found that the enhancement of the heat transfer for large H/L cases is due to that the negative temperature structures play a dominant role. For small H/L cases, the positive temperature structures inhibit the heat transfer. Furthermore, the more positive and negative temperature structures for large H/L cases are generated near the solid wall and the corner of the box. The physical explanation for the Nu enhancement is that the more secondary vortices are generated by the interaction of these turbulent structures and the rough wall, leading to more plumes ejected from the boundary layers to the bulk.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"23 1","pages":"549 - 566"},"PeriodicalIF":1.9,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43544929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Reflections on roughness modelling in turbulent flow 湍流中粗糙度建模的几点思考

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-10-23 DOI: 10.1080/14685248.2022.2137171

P. Durbin

引用次数: 0

Effects of form-induced velocity in rough-wall turbulent channel flows 粗糙壁湍流通道中形状诱导速度的影响

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-10-11 DOI: 10.1080/14685248.2022.2131799

S. C. Mangavelli, J. Yuan

引用次数: 0

Detailed evaluation of a heat exchanger in terms of effectiveness and second law 根据有效性和第二定律对热交换器进行详细评估

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-10-03 DOI: 10.1080/14685248.2022.2134571

E. Turgut, Uğurcan Yardımcı

{"title":"Detailed evaluation of a heat exchanger in terms of effectiveness and second law","authors":"E. Turgut, Uğurcan Yardımcı","doi":"10.1080/14685248.2022.2134571","DOIUrl":"https://doi.org/10.1080/14685248.2022.2134571","url":null,"abstract":"In this study, experiments were conducted to investigate the effects of semicircular strip turbulators placed in the inner tube of a concentric heat exchanger on its exergy loss rate (E*) and effectiveness (e). The Reynolds number (Re), pitch (p), diameter (d), thickness (t) and arrangement style (a) were the design parameters for the study. The changes in these parameters had significant effects on exergy loss rate and effectiveness compared to the results found with the smooth empty tube. The results of the study are given graphically as the change in the exergy loss rate and the change in effectiveness with the number of transfer units (NTU). The largest exergy loss rate and effectiveness values were found to be 0.263 and 0.556, respectively. It was concluded that the effectiveness of the heat exchanger increased with increasing NTU, while the exergy loss rate is decreased. Since the increase in effectiveness will mean an increase in heat transfer, it can also cause an increase in irreversibility. For this reason, multi-performance characteristics have been determined since evaluating the effectiveness together with the exergy loss rate caused by irreversibility will provide more realistic results. Thus, the optimum parameter combination was found, where the maximum effectiveness and the smallest exergy loss rate values were obtained. Finally, the artificial neural network (ANN) model of the study was created and the hyperparameters of the model were determined by the Bayesian optimisation method. In the created ANN model, MSE and R values of effectiveness and exergy loss rate were found as 5.3238e-04, 2.18177e-06 and 0.963, 0.998, respectively. According to these results, it has been confirmed that the proposed ANN model can be used successfully in the modelling of the heat exchanger.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"23 1","pages":"515 - 547"},"PeriodicalIF":1.9,"publicationDate":"2022-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45447587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Effect of slip length on flow dynamics and heat transport in two-dimensional Rayleigh–Bénard convection 滑移长度对二维rayleigh - bsamadard对流流动动力学和热传输的影响

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-09-30 DOI: 10.1080/14685248.2022.2128360

Maojing Huang, Xiaozhou He

{"title":"Effect of slip length on flow dynamics and heat transport in two-dimensional Rayleigh–Bénard convection","authors":"Maojing Huang, Xiaozhou He","doi":"10.1080/14685248.2022.2128360","DOIUrl":"https://doi.org/10.1080/14685248.2022.2128360","url":null,"abstract":"We report a direct numerical simulation (DNS) study of the heat transport and temperature profiles of the plume ejecting and impacting regions in the two-dimensional turbulent Rayleigh–Bénard (RB) convection with slippery plates and horizontally periodic boundary conditions. The numerical study is conducted in the parameter range of Rayleigh number from to and the slip length b from 0 (NS) to ∞ (FS) for the top and bottom plates. Two distinct flow patterns can be seen depending on b, namely convection roll state and zonal flow, which affect the Nusselt number and the Reynolds number . We show that the zonal flow occurs when the normalised slip length , where is the thermal boundary layer thickness for the no-slip (NS) plates. and increase with increasing , and can reach the optimum before the generation of the zonal flow. It is observed that with the effective scaling exponent for the convection roll state, and for the zonal flow. Furthermore, for the convection roll state, the power-law scaling of the local heat flux is in the plume ejecting region, while in the plume impacting region, for varying slip length . The DNS data with different slippery plates for both plume ejecting and impacting regions agree well with the predicted temperature profiles by Huang et al. (J Fluid Mech. 2022;943:A2).","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"23 1","pages":"492 - 514"},"PeriodicalIF":1.9,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"60060999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Drag reduction using velocity control in Taylor–Couette flows 泰勒-库埃特流中使用速度控制的减阻

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-08-06 DOI: 10.1080/14685248.2022.2109653

O. Khawar, M. F. Baig, S. Sanghi

{"title":"Drag reduction using velocity control in Taylor–Couette flows","authors":"O. Khawar, M. F. Baig, S. Sanghi","doi":"10.1080/14685248.2022.2109653","DOIUrl":"https://doi.org/10.1080/14685248.2022.2109653","url":null,"abstract":"Direct numerical simulation of Taylor–Couette flow subject to opposition control is investigated at Reynolds number (Re) of 3000. The idea is to impose exact opposite velocities of the detection plane at the walls to counteract near-wall stream-wise vortices. In this study, various velocity control strategies, namely wall-normal, axial, combined and blowing only, have been investigated from the viewpoint of skin-friction drag reduction. Further, the effects of skipping spatial points in azimuthal and axial directions and in time have been investigated from a drag reduction point of view. Based on the emergence of a virtual wall that hinders the vertical transport of momentum (i.e. on reduction of Reynolds shear stress production as well as sweep ejection events), flow physics has been explained via statistical analysis of fluctuations, Reynolds shear stresses, and near-wall coherent structures. The spatial density of near-wall vortical structures shows a marked reduction, followed by quadrant contribution analysis of Reynolds shear stresses reveals a decrease in ejection and sweep events, leading to reduced production of Reynolds shear stresses and skin-friction drag.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"23 1","pages":"467 - 491"},"PeriodicalIF":1.9,"publicationDate":"2022-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46596631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Turbulence modulation by finite-size particles of different diameters and particle–fluid density ratios in homogeneous isotropic turbulence 均匀各向同性湍流中不同直径的有限大小颗粒和颗粒-流体密度比的湍流调制

IF 1.9 4区工程技术

Journal of Turbulence Pub Date : 2022-08-03 DOI: 10.1080/14685248.2022.2096223

Jie Shen, Cheng Peng, Jianzhao Wu, K. Chong, Zhiming Lu, Lian-Ping Wang

{"title":"Turbulence modulation by finite-size particles of different diameters and particle–fluid density ratios in homogeneous isotropic turbulence","authors":"Jie Shen, Cheng Peng, Jianzhao Wu, K. Chong, Zhiming Lu, Lian-Ping Wang","doi":"10.1080/14685248.2022.2096223","DOIUrl":"https://doi.org/10.1080/14685248.2022.2096223","url":null,"abstract":"In this paper, the influence of particle-fluid density ratio and particle diameter on the turbulence modulation by finite-size particles in forced homogeneous isotropic turbulence is investigated. Results show that the presence of finite-size particles always attenuate the turbulence, and the attenuation is larger for particles with larger density when the particle diameter is fixed. But the attenuation is smaller for particles with larger diameter if the density is fixed, and the weaker attenuation is due to the wake fluctuation when the particle Reynolds number is large enough. The turbulence kinetic energy is attenuated at the large scales and augmented at the small scales. The radial dissipation profiles show that the region affected by the particles with same diameter is identical, but the dissipation near the particle surface is larger if the density is larger due to larger slip velocity and particle Reynolds number. For particles with same density, smaller particles have smaller dissipation near the particle surface but the influence region is larger, and the combined effect leads to the result that the contribution of dissipation in the influence region of smaller particles to the total dissipation is larger. The influence region mainly depends on the particle diameter.","PeriodicalId":49967,"journal":{"name":"Journal of Turbulence","volume":"23 1","pages":"433 - 453"},"PeriodicalIF":1.9,"publicationDate":"2022-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44379033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 3