Physics of Fluids最新文献_第9页

Droplet impinging on sparse micropillar-arrayed non-wetting surfaces 撞击稀疏微柱阵列非润湿表面的液滴

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0226032

Jialong Wu, Longfei Zhang, Yingfa Lu, Yingsong Yu

{"title":"Droplet impinging on sparse micropillar-arrayed non-wetting surfaces","authors":"Jialong Wu, Longfei Zhang, Yingfa Lu, Yingsong Yu","doi":"10.1063/5.0226032","DOIUrl":"https://doi.org/10.1063/5.0226032","url":null,"abstract":"Wettability of droplets and droplet impinging on sparse micropillar-arrayed polydimethylsiloxane (PDMS) surfaces were experimentally investigated. For droplets wetting on these surfaces, the contact line density model combining stability factor and droplet sagging depth was developed to predict whether the droplets were in the Wenzel or Cassie–Baxter wetting state. It was found that droplets on the sparser micropillar-arrayed PDMS surfaces were in the Wenzel wetting state, indicating that a complete rebound cannot happen for droplets impinging on these surfaces. For the case of droplets impinging on sparse micropillar-arrayed PDMS surfaces, it was found that there existed a range of impact velocity for bouncing droplets on the micropatterned surfaces with a solid fraction of 0.022. To predict the upper limit of impact velocity for bouncing droplets, a theoretical model considering the immersion depth of liquid into the micropillar structure was established to make the prediction, and the lower limit of impact velocity for bouncing droplets can be obtained by balancing kinetic energy with energy barrier due to contact angle hysteresis. In addition, the droplet maximum spreading parameter was fitted and found to follow the scale law of We1/4.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"3 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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

Prediction model for self-starting of hypersonic inlets with soft critical unstart mode 具有软临界非启动模式的高超音速进气口自启动预测模型

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0222577

Shu-Zi Yang, Wen-Zhong Xie, Cheng-Long Xu

{"title":"Prediction model for self-starting of hypersonic inlets with soft critical unstart mode","authors":"Shu-Zi Yang, Wen-Zhong Xie, Cheng-Long Xu","doi":"10.1063/5.0222577","DOIUrl":"https://doi.org/10.1063/5.0222577","url":null,"abstract":"The acceleration self-starting performance of hypersonic inlets is of critical importance for the stable operation of scramjet engines. The occurrence of soft unstart during the transition from hard unstart to start is an important flow state that has yet to be fully elucidated. The stability mechanism and corresponding self-starting characteristics of soft unstart remain poorly understood, and there is a pressing need for detailed modeling research in this area. This paper presents a rapid prediction model for the self-starting Mach number of two-dimensional hypersonic inlets with soft critical unstart mode, fully considering the influence of various geometric parameters and Reynolds number in the internal contraction section, and achieving a quantitative analysis of the two-dimensional soft unstart critical flow field. Given the incoming flow conditions and the inlet geometry, the prediction model is capable of accurately representing the actual viscous unstart flow field. It can fully map the unstart separation bubble and its surrounding critical wave structures, and calculate the minimum pressure rise required to maintain the current scale of the main separation bubble and the pressure rise exerted on the unstart separation bubble by the current actual flow field structure. Comparing the relative magnitude of these two pressures determines whether the inlet can transition from soft unstart to start. The proposed prediction model was validated using results from unsteady numerical simulations. The predicted results align well with the simulation results and are significantly better than previous prediction methods.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"4 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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

An improved smoothed particle hydrodynamics method for modeling multiphase flows 用于多相流建模的改进型平滑粒子流体力学方法

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0226148

Yongze Li, Ting Long

引用次数: 0

Dynamics of an acoustically levitated fluid droplet captured by a low-order immersed boundary method 用低阶沉浸边界法捕捉声悬浮液滴的动力学特性

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0223790

Jacqueline B. Sustiel, David G. Grier

引用次数: 0

Development of backward compatible physics-informed neural networks to reduce error accumulation based on a nested framework 基于嵌套框架开发向后兼容的物理信息神经网络，减少误差累积

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0223510

Lei Gao, Yaoran Chen, Guohui Hu, Dan Zhang, Xiangyu Zhang, Xiaowei Li

{"title":"Development of backward compatible physics-informed neural networks to reduce error accumulation based on a nested framework","authors":"Lei Gao, Yaoran Chen, Guohui Hu, Dan Zhang, Xiangyu Zhang, Xiaowei Li","doi":"10.1063/5.0223510","DOIUrl":"https://doi.org/10.1063/5.0223510","url":null,"abstract":"Physical information neural network (PINN) provides an effective method for solving partial differential equations, and many variants have been derived, the most representative of which is backward compatible physical information neural network (BC-PINN). The core of BC-PINN is to use the prediction of the previous time period as the label data of the current time period, which leads to error accumulation in the process of backward compatibility. To solve this problem, a nested backward compatible physical information neural network (NBC-PINN) is proposed in this paper. NBC-PINN has an overlap region between the computation domain of the previous time period and the computation domain of the current time period, which is trained twice in total. Numerical experiments on four representative time-varying partial differential equations show that NBC-PINN can effectively reduce error accumulation, improve computational efficiency and accuracy, and improve the L2 relative error of the numerical solution with fewer residual allocation points. The development of NBC-PINN provides a theoretical basis for the scientific calculation of partial differential equations, and promotes the progress of PINN to a certain extent.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"26 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 force on an accelerating flat plate at low Reynolds numbers 低雷诺数时加速平板上的阻力

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0223050

Wenjie Liu, Mao Sun

{"title":"Drag force on an accelerating flat plate at low Reynolds numbers","authors":"Wenjie Liu, Mao Sun","doi":"10.1063/5.0223050","DOIUrl":"https://doi.org/10.1063/5.0223050","url":null,"abstract":"The accelerating flat plate is a useful model for studying the drag-based flapping flight (where drag is used to provide the weight-supporting force or thrust). Previous studies have mainly focused on the high Reynolds number (Re) regime pertaining to the flight of relatively large insects and birds. In this study, we numerically investigate the unsteady drag and flows of a uniformly accelerating flat plate at low Re that is typical of miniature insect flight (Re = 10–40). The following is shown. Unlike high-Re cases where the acceleration effect on drag is insensitive to Re, at low Re, the effect exhibits a strong dependence on Re: As Re decreases below 100, the acceleration effect increases rapidly, becoming 33%–56% greater than that of high-Re cases in the Re range of 10–40, before gradually decreasing. A simple model that consists of the quasi-steady, added-mass, and history force terms is proposed for drag at low Re. The scalings of the quasi-steady and added-mass force terms are well known; we find that the history force term scales approximately with the square root of the acceleration and velocity. The above result that relatively large drag is produced by the accelerating wing at Re = 10–40 is especially interesting and might explain why miniature insects fly in this Re range.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"20 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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

Thermal effect on the flow induced by a single-dielectric-barrier-discharge plasma actuator under steady actuation 单介质阻挡放电等离子体致动器在稳定致动下对流动的热效应

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0220507

Longxiang Zhao, Zuoli Xiao, Feng Liu

{"title":"Thermal effect on the flow induced by a single-dielectric-barrier-discharge plasma actuator under steady actuation","authors":"Longxiang Zhao, Zuoli Xiao, Feng Liu","doi":"10.1063/5.0220507","DOIUrl":"https://doi.org/10.1063/5.0220507","url":null,"abstract":"The thermal effect of a single-dielectric-barrier-discharge plasma actuator under steady actuation is numerically investigated. A new actuator model is proposed and validated using experimental data. A discrete Galerkin method based on high-order flux reconstruction schemes is employed to solve the flow governing equations and the actuator model equations on unstructured quadrilateral grids. By comparing the induced heated and cold flow fields of the actuator with and without a plasma thermal source, its thermal effect is revealed. The actuator generates a thermal wall jet with rich vorticity, forming a monopolar starting vortex with a high-temperature and low-density core. Over time, the starting vortex becomes unstable and transforms into a dipole. Actuator heating enhances jet velocity and width, as well as vortex stability, while slowing down vorticity generation. The relative change in density and temperature fields due to actuator heating is four orders of magnitude greater than that without actuator heating. Additionally, the actuator heating causes the background thermodynamic fields to increase approximately linearly with time. Two stages in the actuator's thermal effect are distinguished due to time accumulation. Initially, the actuator heating minimally affects the monopolar starting vortex motion, and the temperature and density fields are treated as passive variables driven by the velocity field. During this stage, the momentum and thermal effects of the actuator can be studied separately. However, after the starting vortex becomes unstable, the actuator heating significantly impacts its motion and morphology, and these two effects are coupled with each other.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"38 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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

Turbulent pipe flow and heat transfer of a binary mixture at supercritical pressure: Influences of cross-diffusion effects 超临界压力下二元混合物的湍流管道流动和传热：交叉扩散效应的影响

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0221800

Yangjian Ren, Mingfei Xiao, Zhan-Chao Hu

{"title":"Turbulent pipe flow and heat transfer of a binary mixture at supercritical pressure: Influences of cross-diffusion effects","authors":"Yangjian Ren, Mingfei Xiao, Zhan-Chao Hu","doi":"10.1063/5.0221800","DOIUrl":"https://doi.org/10.1063/5.0221800","url":null,"abstract":"Cross-diffusion effects, including Soret and Dufour effects, are enhanced around the pseudo-critical temperature (Tpc) of a binary mixture. Their influences on heat transfer at supercritical pressure have been scarcely studied. To bridge this gap, large-eddy simulations (LES) are conducted to investigate forced convective heat transfer of a CO2–ethane mixture at supercritical pressures in a circular pipe subject to a uniform heat flux. Both heating and cooling conditions, along with varying initial concentrations and thermodynamic pressures, are included in the simulations. The LES results reveal that the Soret effect causes concentration separation, resulting in a concentration boundary layer. The magnitudes of the thermodiffusion factor (kT) and the radial temperature gradient control the intensity of separation, which is more pronounced at near-critical pressure and high heat flux. Since kT is significant only around Tpc, downstream decay of the concentration separation is observed as the loci of T=Tpc migrate away from the wall so that the local radial temperature gradient diminishes. The primary factors affecting heat transfer are the variations in thermal conductivity and isobaric specific heat resulting from concentration separation. In contrast, the Dufour effect and the accompanying inter-diffusion play negligible roles. In deterioration scenarios, the bulk Nusselt number (Nub) shows a maximum relative drop of 8%, whereas in enhancement scenarios, Nub shows a maximum relative increase in 10%, with both deterioration and enhancement decaying downstream. Cross-diffusion effects have negligible impacts on density and streamwise velocity, but noticeably alter streamwise velocity fluctuation and turbulent kinetic energy.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"9 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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

Mechanisms of fluid–structure interaction in an underwater muzzle brake 水下枪口制动器中流体与结构的相互作用机理

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0227525

Zhiqun Sun, Qiang Li, Pu Qu

{"title":"Mechanisms of fluid–structure interaction in an underwater muzzle brake","authors":"Zhiqun Sun, Qiang Li, Pu Qu","doi":"10.1063/5.0227525","DOIUrl":"https://doi.org/10.1063/5.0227525","url":null,"abstract":"A fluid–structure interaction (FSI) mechanism of a shock-type underwater muzzle brake is examined. A bidirectional coupling interior ballistic approach is employed to achieve accurate projectile velocity. A velocity–pressure separation solution algorithm, semi-implicit method for pressure-linked equations and the Schnerr–Sauer cavitation model are used to address the volume of fluid multiphase Navier–Stokes equations with compressible cavitation. The full ballistic muzzle flow field distribution is comprehensively modeled. Analyzing the force and flow parameters of the T-shaped underwater muzzle brake based on the numerical solution reveals detailed insights. The underwater muzzle brake provides significant braking force in the interior ballistic period due to the presence of the water medium, which is quite different from air launch. Moreover, while both the internal and intermediate ballistic periods utilize the kinetic energy of the fluid against the wall, the muzzle brake principle in the interior ballistic period is a positive kinetic impact of water, mainly dependent on the flow velocity inside the barrel, and provides 17% recoil impulse. The side holes are significantly affected by cavitation phenomena. In contrast, during the intermediate ballistic period, the kinetic impact of gas, primarily dependent on the high-pressure gas expansion, decreases exponentially with time and provides 36% recoil impulse.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"33 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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

On particle dispersion statistics using unsupervised learning and Gaussian mixture models 利用无监督学习和高斯混合物模型研究粒子弥散统计

IF 4.6 2区工程技术

Physics of Fluids Pub Date : 2024-09-10 DOI: 10.1063/5.0229111

Nicholas Christakis, Dimitris Drikakis

{"title":"On particle dispersion statistics using unsupervised learning and Gaussian mixture models","authors":"Nicholas Christakis, Dimitris Drikakis","doi":"10.1063/5.0229111","DOIUrl":"https://doi.org/10.1063/5.0229111","url":null,"abstract":"Understanding the dispersion of particles in enclosed spaces is crucial for controlling the spread of infectious diseases. This study introduces an innovative approach that combines an unsupervised learning algorithm with a Gaussian mixture model to analyze the behavior of saliva droplets emitted from a coughing individual. The algorithm effectively clusters data, while the Gaussian mixture model captures the distribution of these clusters, revealing underlying sub-populations and variations in particle dispersion. Using computational fluid dynamics simulation data, this integrated method offers a robust, data-driven perspective on particle dynamics, unveiling intricate patterns and probabilistic distributions previously unattainable. The combined approach significantly enhances the accuracy and interpretability of predictions, providing valuable insights for public health strategies to prevent virus transmission in indoor environments. The practical implications of this study are profound, as it demonstrates the potential of advanced unsupervised learning techniques in addressing complex biomedical and engineering challenges and underscores the importance of coupling sophisticated algorithms with statistical models for comprehensive data analysis. The potential impact of these findings on public health strategies is significant, highlighting the relevance of this research to real-world applications.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":"19 1","pages":""},"PeriodicalIF":4.6,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142218305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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