European Journal of Mechanics B-fluids最新文献_第4页

A unidirectional phase-resolved wave prediction model based on deep Koopman embeddings 基于深库普曼嵌入的单向相位分辨波预测模型

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-12-12 DOI: 10.1016/j.euromechflu.2025.204429

Zhongying Feng , Ye Wang , Chenghao Fu , Ruipeng Li , Kun Zheng , Zhan Wang

The phase-resolved wave prediction is of vital importance for improving the safety and operations of structures in ocean engineering, such as floating wind turbines and wave energy converters. However, it is challenging for traditional physical methods to predict wave elevation accurately and efficiently in high sea states where the nonlinearity plays an important role. Inspired by the capability of the Koopman theory in solving nonlinear problems, a phase-resolved wave prediction model by combining deep learning with Koopman operator, referred to as DKWP, is designed. The high-order spectral method is employed for providing training and test data. To illustrate the effectiveness of the proposed method, we compare it with another four phase-resolved wave prediction models, including the models based on artificial neural network, long short-term memory, U-Net and linear wave theory. The models are trained under the sea states 3–5 with wide ranges of significant height, peak period and peak factor. Comparisons between the predicted wave elevation and true wave elevation indicate that DKWP outperforms the other models in terms of accuracy. The generalization of the DKWP is validated when it predicts the wave elevation under the sea states 6–7. In addition, to improve the interpretability of the DKWP, the eigenvalues of the Koopman operator in the proposed model are further analyzed.

相分辨波浪预报对于提高海上工程结构的安全性和运行性能具有重要意义，如浮式风力发电机组和波浪能变流器。然而，在非线性起重要作用的高海况下，传统的物理方法难以准确有效地预测海浪高程。受Koopman理论解决非线性问题能力的启发，设计了一种结合深度学习和Koopman算子的相位分辨波预测模型，简称DKWP。采用高阶谱法提供训练和测试数据。为了说明该方法的有效性，我们将其与另外四种相位分辨波预测模型进行了比较，包括基于人工神经网络、长短期记忆、U-Net和线性波理论的模型。模型在3-5海况下进行训练，显著高度、峰值时段和峰值因子范围较大。预测波高与真实波高的比较表明，DKWP模型在精度上优于其他模型。通过对6 ~ 7海况下波浪高程的预测，验证了DKWP的泛化效果。此外，为了提高DKWP的可解释性，进一步分析了该模型中Koopman算子的特征值。

{"title":"A unidirectional phase-resolved wave prediction model based on deep Koopman embeddings","authors":"Zhongying Feng , Ye Wang , Chenghao Fu , Ruipeng Li , Kun Zheng , Zhan Wang","doi":"10.1016/j.euromechflu.2025.204429","DOIUrl":"10.1016/j.euromechflu.2025.204429","url":null,"abstract":"<div><div>The phase-resolved wave prediction is of vital importance for improving the safety and operations of structures in ocean engineering, such as floating wind turbines and wave energy converters. However, it is challenging for traditional physical methods to predict wave elevation accurately and efficiently in high sea states where the nonlinearity plays an important role. Inspired by the capability of the Koopman theory in solving nonlinear problems, a phase-resolved wave prediction model by combining deep learning with Koopman operator, referred to as DKWP, is designed. The high-order spectral method is employed for providing training and test data. To illustrate the effectiveness of the proposed method, we compare it with another four phase-resolved wave prediction models, including the models based on artificial neural network, long short-term memory, U-Net and linear wave theory. The models are trained under the sea states 3–5 with wide ranges of significant height, peak period and peak factor. Comparisons between the predicted wave elevation and true wave elevation indicate that DKWP outperforms the other models in terms of accuracy. The generalization of the DKWP is validated when it predicts the wave elevation under the sea states 6–7. In addition, to improve the interpretability of the DKWP, the eigenvalues of the Koopman operator in the proposed model are further analyzed.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204429"},"PeriodicalIF":2.5,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837009","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

PCM energy storage considering nanofluid volumetric radiation and natural convection in an inclined non-uniformly heated enclosure: LBM simulation 考虑纳米流体体积辐射和自然对流在倾斜非均匀加热封闭环境中的PCM储能：LBM模拟

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-12-10 DOI: 10.1016/j.euromechflu.2025.204444

Masoud Sobhani , Javad Abolfazli Esfahani , Hashem Ahmadi Tighchi

This study presents a comprehensive numerical investigation of the melting behavior of a phase change material during heat transfer and storage. This material is located in an inclined enclosure filled with nanofluid, under non-uniform wall heating conditions. For the nanofluid medium, the influence of natural convection and volumetric thermal radiation is considered using real radiative properties of nanoparticles. The Lattice Boltzmann Method is utilized to simulate the coupled heat transfer and phase change processes. The effects of Planck numbers (

Pl

= 0.01–1), Rayleigh numbers (

Ra

= 10⁴ and 10⁵), and inclination angles (

γ

= 0°–90°) are examined at different times to assess temperature distribution, melting front propagation, velocity profile, liquid fraction, and total heat transfer performance. The results show that at the highest Planck number (

Pl

= 1), natural convection dominates, with melting starting from boundaries aligned with the heated nanofluid flow. However, at Planck numbers less than 0.1, radiation significantly enhances the temperature distribution and melting rate, resulting in up to 8.3 and 7.5 times increases in the liquid fraction and total Nusselt number, respectively. At

Pl

= 1, the inclination angle of 0° yielded the highest melting performance with a liquid fraction of 31 % and 22 % for

Ra

= 10⁴ and 10⁵, respectively. While at

Pl

= 0.01, the inclination angle of 45° achieved the maximum melting with values exceeding 60 % due to the intensified radiative heat transfer and enhancement of the total Nusselt number by about 8 times. The interplay between radiation intensity and enclosure angle offers an influential mechanism for enhancing thermal performance. These findings provide valuable insights into the optimized design of advanced latent heat storage systems under multi-mode heat transfers.

本文对相变材料在传热和储存过程中的熔化行为进行了全面的数值研究。这种材料位于一个充满纳米流体的倾斜外壳中，在不均匀的壁加热条件下。对于纳米流体介质，利用纳米粒子的真实辐射特性，考虑了自然对流和体积热辐射的影响。利用晶格玻尔兹曼方法模拟了传热与相变的耦合过程。在不同时间考察了普朗克数（Pl = 0.01-1）、瑞利数（Ra = 104和105）和倾角（γ = 0°-90°）的影响，以评估温度分布、熔化锋传播、速度分布、液体分数和总传热性能。结果表明，在最高普朗克数（Pl = 1）时，自然对流占主导地位，熔化从与加热纳米流体流动对齐的边界开始。然而，在普朗克数小于0.1时，辐射显著增强了温度分布和熔化速率，导致液体分数和总努塞尔数分别增加了8.3倍和7.5倍。在Pl = 1时，当倾角为0°时，Ra= 104和Ra= 105的熔液分数分别为31%和22%，熔融效果最好。而在Pl = 0.01时，45°倾角下，由于辐射传热加剧，总努塞尔数增加了约8倍，最大熔化值超过60%。辐射强度和围护角之间的相互作用为提高热工性能提供了一个有影响的机制。这些发现为多模式传热下先进潜热存储系统的优化设计提供了有价值的见解。

{"title":"PCM energy storage considering nanofluid volumetric radiation and natural convection in an inclined non-uniformly heated enclosure: LBM simulation","authors":"Masoud Sobhani , Javad Abolfazli Esfahani , Hashem Ahmadi Tighchi","doi":"10.1016/j.euromechflu.2025.204444","DOIUrl":"10.1016/j.euromechflu.2025.204444","url":null,"abstract":"<div><div>This study presents a comprehensive numerical investigation of the melting behavior of a phase change material during heat transfer and storage. This material is located in an inclined enclosure filled with nanofluid, under non-uniform wall heating conditions. For the nanofluid medium, the influence of natural convection and volumetric thermal radiation is considered using real radiative properties of nanoparticles. The Lattice Boltzmann Method is utilized to simulate the coupled heat transfer and phase change processes. The effects of Planck numbers (<span><math><mi>Pl</mi></math></span> = 0.01–1), Rayleigh numbers (<span><math><mi>Ra</mi></math></span> = 10<sup>4</sup> and 10<sup>5</sup>), and inclination angles (<span><math><mi>γ</mi></math></span> = 0°–90°) are examined at different times to assess temperature distribution, melting front propagation, velocity profile, liquid fraction, and total heat transfer performance. The results show that at the highest Planck number (<span><math><mi>Pl</mi></math></span> = 1), natural convection dominates, with melting starting from boundaries aligned with the heated nanofluid flow. However, at Planck numbers less than 0.1, radiation significantly enhances the temperature distribution and melting rate, resulting in up to 8.3 and 7.5 times increases in the liquid fraction and total Nusselt number, respectively. At <span><math><mi>Pl</mi></math></span> = 1, the inclination angle of 0° yielded the highest melting performance with a liquid fraction of 31 % and 22 % for <span><math><mi>Ra</mi></math></span>= 10<sup>4</sup> and 10<sup>5</sup>, respectively. While at <span><math><mi>Pl</mi></math></span> = 0.01, the inclination angle of 45° achieved the maximum melting with values exceeding 60 % due to the intensified radiative heat transfer and enhancement of the total Nusselt number by about 8 times. The interplay between radiation intensity and enclosure angle offers an influential mechanism for enhancing thermal performance. These findings provide valuable insights into the optimized design of advanced latent heat storage systems under multi-mode heat transfers.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204444"},"PeriodicalIF":2.5,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Aerodynamic and aeroacoustic evaluation of slat and slot separation control on a small-scale HAWT: A computational study 小型HAWT狭缝分离控制的气动与气动声学评价：计算研究

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-12-09 DOI: 10.1016/j.euromechflu.2025.204443

Sami Bouterra , Riyadh Belamadi , Abdelouaheb Djemili , Adrian Ilinca

The global push toward clean energy has intensified the search for efficient, innovative technologies to harness renewable resources. Small-scale horizontal-axis wind turbines (HAWTs) offer a promising solution to meet growing urban energy demands with minimal environmental impact. This computational study investigates the aerodynamic and aeroacoustic effects of two passive flow separation control techniques, slat and slot, applied to the blades of a small-scale HAWT. Using the NREL S809 Phase II rotor as a benchmark, simulations are conducted using the steady Moving Reference Frame (MRF) and the unsteady Sliding Mesh Motion (SMM) approaches. The k-ω SST turbulence model is validated against experimental data for multiple inflow conditions. The results demonstrate that flow separation is significantly mitigated by both control methods, particularly at higher wind speeds and at specific locations along the blade span. Quantitatively, the slat and slot configurations yield power output increases of 8.74 % and 21.07 %, respectively, compared to the baseline case. However, aeroacoustic analysis reveals that the slot introduces a sound pressure level (SPL) increase of up to 20 dB near 1 kHz, while providing a more balanced performance in terms of noise and energy gain. These findings highlight the slot configuration as a particularly effective solution for enhancing aerodynamic efficiency, while the slat provides a more balanced aeroacoustic profile. The choice between them involves a trade-off between maximum power gain and noise-control requirements in small-scale wind energy systems.

全球对清洁能源的推动加强了对利用可再生资源的高效、创新技术的探索。小型水平轴风力涡轮机（HAWTs）提供了一个有前途的解决方案，以满足日益增长的城市能源需求，同时对环境的影响最小。本文研究了窄缝和狭缝两种被动流动分离控制技术在小型HAWT叶片上的气动和气动声学效果。以NREL S809二期转子为基准，采用稳态移动参考系（MRF）和非定常滑动网格运动（SMM）方法进行了仿真。k-ω海温湍流模型在多种入流条件下进行了实验验证。结果表明，两种控制方法都显著减轻了流动分离，特别是在高风速和沿叶跨的特定位置。从数量上看，与基线情况相比，槽形和槽形配置的功率输出分别增加了8.74 %和21.07 %。然而，气动声学分析表明，该槽在1 kHz附近引入了高达20 dB的声压级（SPL）增加，同时在噪声和能量增益方面提供了更平衡的性能。这些发现强调了狭缝结构是提高气动效率的特别有效的解决方案，而狭缝提供了更平衡的气动声学剖面。在它们之间的选择涉及到在小型风能系统中最大功率增益和噪声控制要求之间的权衡。

{"title":"Aerodynamic and aeroacoustic evaluation of slat and slot separation control on a small-scale HAWT: A computational study","authors":"Sami Bouterra , Riyadh Belamadi , Abdelouaheb Djemili , Adrian Ilinca","doi":"10.1016/j.euromechflu.2025.204443","DOIUrl":"10.1016/j.euromechflu.2025.204443","url":null,"abstract":"<div><div>The global push toward clean energy has intensified the search for efficient, innovative technologies to harness renewable resources. Small-scale horizontal-axis wind turbines (HAWTs) offer a promising solution to meet growing urban energy demands with minimal environmental impact. This computational study investigates the aerodynamic and aeroacoustic effects of two passive flow separation control techniques, slat and slot, applied to the blades of a small-scale HAWT. Using the NREL S809 Phase II rotor as a benchmark, simulations are conducted using the steady Moving Reference Frame (MRF) and the unsteady Sliding Mesh Motion (SMM) approaches. The k-ω SST turbulence model is validated against experimental data for multiple inflow conditions. The results demonstrate that flow separation is significantly mitigated by both control methods, particularly at higher wind speeds and at specific locations along the blade span. Quantitatively, the slat and slot configurations yield power output increases of 8.74 % and 21.07 %, respectively, compared to the baseline case. However, aeroacoustic analysis reveals that the slot introduces a sound pressure level (SPL) increase of up to 20 dB near 1 kHz, while providing a more balanced performance in terms of noise and energy gain. These findings highlight the slot configuration as a particularly effective solution for enhancing aerodynamic efficiency, while the slat provides a more balanced aeroacoustic profile. The choice between them involves a trade-off between maximum power gain and noise-control requirements in small-scale wind energy systems.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204443"},"PeriodicalIF":2.5,"publicationDate":"2025-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Numerical investigation on the suppression mechanism of tip leakage vortex and cavitation via tip water injection 叶尖注水抑制泄漏涡和空化机理的数值研究

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-12-08 DOI: 10.1016/j.euromechflu.2025.204442

Yigan Zhang, Zehui Qu, Yonghao Ye, Baiyan He, Huaping Liu

Tip-leakage vortex (TLV) and TLV cavitation have a significant negative impact on the efficiency and stability of hydraulic machinery. This study proposes an active flow control strategy based on tip water injection. The NACA0009 hydrofoil, with two representative tip clearance sizes of 2 mm and 10 mm, is employed to systematically investigate the influence of injection angle on TLV suppression. The SST-CC turbulence model and the ZGB cavitation model are used to capture unsteady cavitating flows. The results reveal that the water injection operates through two primary control mechanisms involving momentum mixing and channel blockage. These mechanisms collectively reduce the tip leakage flow velocity and increase the local pressure, thereby suppressing the development of the TLV and the associated cavitation. As the injection angle β increases, the blockage effect becomes more pronounced, thereby enhancing the suppression effect of the TLV. Under small clearance condition (2 mm), the water injection induces the multiple smaller TLV, which weakens the primary TLV strength. Under large clearance condition (10 mm), the water injection remains effective in reducing tip leakage velocity and suppressing TLV cavitation.

叶尖泄漏涡（TLV）及其空化对液压机械的效率和稳定性有显著的负面影响。本文提出了一种基于尖端注水的主动流动控制策略。采用2 mm和10 mm两种典型叶尖间隙的NACA0009型水翼，系统研究了注入角对TLV抑制的影响。采用SST-CC湍流模型和ZGB空化模型捕捉非定常空化流动。结果表明，注水主要通过动量混合和通道堵塞两种控制机制进行。这些机制共同降低了叶尖泄漏流动速度，增加了局部压力，从而抑制了TLV的发展和相关的空化。随着注入角β的增大，堵塞效应更加明显，从而增强了TLV的抑制作用。在小间隙条件下（2 mm），注水诱发了多个较小的TLV，削弱了原生TLV的强度。在大间隙条件下（10 mm），注水仍能有效降低叶尖泄漏速度，抑制TLV空化。

{"title":"Numerical investigation on the suppression mechanism of tip leakage vortex and cavitation via tip water injection","authors":"Yigan Zhang, Zehui Qu, Yonghao Ye, Baiyan He, Huaping Liu","doi":"10.1016/j.euromechflu.2025.204442","DOIUrl":"10.1016/j.euromechflu.2025.204442","url":null,"abstract":"<div><div>Tip-leakage vortex (TLV) and TLV cavitation have a significant negative impact on the efficiency and stability of hydraulic machinery. This study proposes an active flow control strategy based on tip water injection. The NACA0009 hydrofoil, with two representative tip clearance sizes of 2 mm and 10 mm, is employed to systematically investigate the influence of injection angle on TLV suppression. The SST-CC turbulence model and the ZGB cavitation model are used to capture unsteady cavitating flows. The results reveal that the water injection operates through two primary control mechanisms involving momentum mixing and channel blockage. These mechanisms collectively reduce the tip leakage flow velocity and increase the local pressure, thereby suppressing the development of the TLV and the associated cavitation. As the injection angle <em>β</em> increases, the blockage effect becomes more pronounced, thereby enhancing the suppression effect of the TLV. Under small clearance condition (2 mm), the water injection induces the multiple smaller TLV, which weakens the primary TLV strength. Under large clearance condition (10 mm), the water injection remains effective in reducing tip leakage velocity and suppressing TLV cavitation.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204442"},"PeriodicalIF":2.5,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

CFD-guided design and performance evaluation of a mobile aerator for delaying channel ice formation cfd导向的移动缓冰器设计与性能评价

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-30 DOI: 10.1016/j.euromechflu.2025.204428

Fangpeng Zhao , Zhihong Li , Yang Chen , Wei Cui

Addressing the ice formation issue in open-channel water conveyance during winter in cold regions, this study guided the design of a mobile device integrating both propulsion and aeration functions. By enhancing water surface flow velocity and temperature distribution, the developed apparatus effectively delays the ice formation process and extends the normal water conveyance period. In this study, the CFD approach was conducted to investigate the hydrodynamic and thermal performance of the mobile aeration device in an open channel environment. The overset mesh method was applied to simulate the rotational motion of aeration components, while the Eulerian mixture model was used to capture the changes in the channel’s physical fields, including velocity and temperature distribution. Simulation results demonstrated that the device significantly improves flow characteristics and temperature distribution in the surface layer of open channels. Through systematic parametric analysis, the optimal combination scheme of key operational parameters (travel speed and longitudinal spacing) was determined, achieving enhanced flow velocity and temperature rise effects over extensive water areas.

针对寒冷地区冬季明渠输水结冰问题，本研究指导设计了集推进与曝气功能于一体的移动装置。该装置通过提高水面流速和温度分布，有效地延缓了冰的形成过程，延长了正常输水周期。在本研究中，采用CFD方法研究了移动曝气装置在开放通道环境下的水动力和热性能。采用复置网格法模拟曝气部件的旋转运动，采用欧拉混合模型捕捉通道物理场的变化，包括速度和温度分布。仿真结果表明，该装置显著改善了明渠表层的流动特性和温度分布。通过系统的参数分析，确定了关键运行参数（行程速度和纵向间距）的最优组合方案，在大面积水域实现了增强的流速和温升效果。

{"title":"CFD-guided design and performance evaluation of a mobile aerator for delaying channel ice formation","authors":"Fangpeng Zhao , Zhihong Li , Yang Chen , Wei Cui","doi":"10.1016/j.euromechflu.2025.204428","DOIUrl":"10.1016/j.euromechflu.2025.204428","url":null,"abstract":"<div><div>Addressing the ice formation issue in open-channel water conveyance during winter in cold regions, this study guided the design of a mobile device integrating both propulsion and aeration functions. By enhancing water surface flow velocity and temperature distribution, the developed apparatus effectively delays the ice formation process and extends the normal water conveyance period. In this study, the CFD approach was conducted to investigate the hydrodynamic and thermal performance of the mobile aeration device in an open channel environment. The overset mesh method was applied to simulate the rotational motion of aeration components, while the Eulerian mixture model was used to capture the changes in the channel’s physical fields, including velocity and temperature distribution. Simulation results demonstrated that the device significantly improves flow characteristics and temperature distribution in the surface layer of open channels. Through systematic parametric analysis, the optimal combination scheme of key operational parameters (travel speed and longitudinal spacing) was determined, achieving enhanced flow velocity and temperature rise effects over extensive water areas.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204428"},"PeriodicalIF":2.5,"publicationDate":"2025-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Macroscopic quantum-like behavior of a turbulent jet 湍流射流的宏观类量子行为

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-29 DOI: 10.1016/j.euromechflu.2025.204427

Laurent Nottale, Thierry Lehner

We apply the scale-relativity theory of turbulence to round jets. For a flow reaching scales much larger than the integral scale, which is the case in jets, we find that fluid particle trajectories become fractal beyond the integral scale. On this basis, the Navier–Stokes equations can be integrated under the form of a macroscopic Schrödinger-type equation, which is solved in terms of a wave function whose modulus squared yields the concentration profile. The solution obtained is in excellent agreement with the experimentally observed turbulent free jet concentration. Then we have performed a new experiment, in order to put to the test such a macroquantum-like behavior. The free turbulent jet has a natural conic self-similar structure with opening angle

α_{S} \approx 0.235

. We have performed an experiment consisting of confining a turbulent jet inside its own cone: this is, according to the scale-relativity approach, a macroscopic analog of a quantum particle in a cylindrical box. Thanks to the infinite potential well thus achieved, excited states can be reached. In the first one, we predict from the Schrödinger equation a vanishing concentration on the centerline of the jet, while it is highest for the free jet. This new theoretical prediction is validated with high statistical significance in our jet experiment, which therefore brings strong support to the existence of macroscopic quantum-like phenomena driven by (effective) nondifferentiability of a medium and its induced fractality.

我们将湍流的尺度相对论应用于圆形射流。对于比积分尺度大得多的流动，如射流，我们发现流体粒子轨迹在积分尺度之外就变成了分形。在此基础上，可以将Navier-Stokes方程积分为宏观Schrödinger-type方程，该方程用波函数求解，其模量平方得到浓度剖面。所得到的解与实验观察到的湍流自由射流浓度非常吻合。然后我们进行了一个新的实验，以测试这种类似大量子的行为。自由湍流射流具有自然锥型自相似结构，开口角αS≈0.235。我们进行了一项实验，将湍流射流限制在其自身的锥内：根据尺度相对论的方法，这是一个圆柱形盒子中量子粒子的宏观模拟。由于得到了无限的势能，就可以达到激发态。在第一种情况中，我们从Schrödinger方程预测射流中心线上的浓度会消失，而自由射流的浓度最高。这一新的理论预测在我们的射流实验中得到了高统计意义的验证，从而有力地支持了由介质的（有效）不可微性及其诱导分形驱动的宏观类量子现象的存在。

{"title":"Macroscopic quantum-like behavior of a turbulent jet","authors":"Laurent Nottale, Thierry Lehner","doi":"10.1016/j.euromechflu.2025.204427","DOIUrl":"10.1016/j.euromechflu.2025.204427","url":null,"abstract":"<div><div>We apply the scale-relativity theory of turbulence to round jets. For a flow reaching scales much larger than the integral scale, which is the case in jets, we find that fluid particle trajectories become fractal beyond the integral scale. On this basis, the Navier–Stokes equations can be integrated under the form of a macroscopic Schrödinger-type equation, which is solved in terms of a wave function whose modulus squared yields the concentration profile. The solution obtained is in excellent agreement with the experimentally observed turbulent free jet concentration. Then we have performed a new experiment, in order to put to the test such a macroquantum-like behavior. The free turbulent jet has a natural conic self-similar structure with opening angle <span><math><mrow><msub><mrow><mi>α</mi></mrow><mrow><mi>S</mi></mrow></msub><mo>≈</mo><mn>0</mn><mo>.</mo><mn>235</mn></mrow></math></span>. We have performed an experiment consisting of <em>confining a turbulent jet inside its own cone</em>: this is, according to the scale-relativity approach, a macroscopic analog of a quantum particle in a cylindrical box. Thanks to the infinite potential well thus achieved, excited states can be reached. In the first one, we predict from the Schrödinger equation a vanishing concentration on the centerline of the jet, while it is highest for the free jet. This new theoretical prediction is validated with high statistical significance in our jet experiment, which therefore brings strong support to the existence of macroscopic quantum-like phenomena driven by (effective) nondifferentiability of a medium and its induced fractality.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204427"},"PeriodicalIF":2.5,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Kelvin–Helmholtz instabilities and mixing in surface-propagating gravity currents 表面传播重力流中的开尔文-亥姆霍兹不稳定性和混合

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-28 DOI: 10.1016/j.euromechflu.2025.204422

Paul A. Jarvis , Allan Fries , Carolina Diaz-Vecino , Jonathan Lemus , Amanda Clarke , Irene Manzella , Jeremy Phillips , Costanza Bonadonna

Gravity currents are stratified shear flows common in various geophysical settings. During propagation, mixing between the current and the ambient fluid can occur via Kelvin–Helmholtz instabilities, leading to the formation of billows (vortices) on the current surface. Although the Kelvin–Helmholtz instability has implications for the transport of heat, solutes and sediments, the properties of the billows remain poorly quantified, particularly for free-surface gravity currents. This study presents laboratory experiments on buoyant, full-depth, lock-release gravity currents propagating at a free surface during the slumping regime. By varying the density contrast, we show that current propagation speeds and mean shapes align with two-layer shallow water theory, with most of the fluid contained in a temporally thinning, spatially uniform thick head. Kelvin–Helmholtz billows consistently form at the current front, becoming more coherent with increasing current velocity. We find that billows are generated at intervals equal to the time required for the current to advance a distance equal to its thickness, and they propagate forward at 25% of the current speed. Billows also undergo merging, with spacing approaching the total flow depth. Volume-based entrainment coefficients increase with Reynolds number, mirroring trends in basal currents. These findings quantify key properties of finite-amplitude Kelvin–Helmholtz billows in free-surface gravity currents and provide a foundation for understanding mixing and transport in environmental stratified shear flows.

重力流是在各种地球物理环境中常见的分层剪切流。在传播过程中，电流和周围流体之间的混合可以通过开尔文-亥姆霍兹不稳定性发生，导致电流表面形成波浪（漩涡）。尽管开尔文-亥姆霍兹不稳定性对热、溶质和沉积物的输运有影响，但波浪的性质仍然很难量化，特别是对自由表面重力流。本研究介绍了在滑塌状态下在自由表面传播的浮力、全深度、锁释放重力流的实验室实验。通过改变密度对比，我们发现电流传播速度和平均形状与两层浅水理论一致，大部分流体包含在一个时间变薄、空间均匀的厚头中。开尔文-亥姆霍兹波浪在当前锋面持续形成，随着流速的增加而变得更加连贯。我们发现，波浪产生的间隔等于电流前进一段等于其厚度的距离所需的时间，并且它们以电流速度的25%向前传播。波浪也经历合并，其间距接近总流动深度。基于体积的夹带系数随着雷诺数的增加而增加，反映了基流的趋势。这些发现量化了自由表面重力流中有限振幅开尔文-亥姆霍兹波浪的关键特性，并为理解环境分层剪切流中的混合和输运提供了基础。

{"title":"Kelvin–Helmholtz instabilities and mixing in surface-propagating gravity currents","authors":"Paul A. Jarvis , Allan Fries , Carolina Diaz-Vecino , Jonathan Lemus , Amanda Clarke , Irene Manzella , Jeremy Phillips , Costanza Bonadonna","doi":"10.1016/j.euromechflu.2025.204422","DOIUrl":"10.1016/j.euromechflu.2025.204422","url":null,"abstract":"<div><div>Gravity currents are stratified shear flows common in various geophysical settings. During propagation, mixing between the current and the ambient fluid can occur via Kelvin–Helmholtz instabilities, leading to the formation of billows (vortices) on the current surface. Although the Kelvin–Helmholtz instability has implications for the transport of heat, solutes and sediments, the properties of the billows remain poorly quantified, particularly for free-surface gravity currents. This study presents laboratory experiments on buoyant, full-depth, lock-release gravity currents propagating at a free surface during the slumping regime. By varying the density contrast, we show that current propagation speeds and mean shapes align with two-layer shallow water theory, with most of the fluid contained in a temporally thinning, spatially uniform thick head. Kelvin–Helmholtz billows consistently form at the current front, becoming more coherent with increasing current velocity. We find that billows are generated at intervals equal to the time required for the current to advance a distance equal to its thickness, and they propagate forward at 25% of the current speed. Billows also undergo merging, with spacing approaching the total flow depth. Volume-based entrainment coefficients increase with Reynolds number, mirroring trends in basal currents. These findings quantify key properties of finite-amplitude Kelvin–Helmholtz billows in free-surface gravity currents and provide a foundation for understanding mixing and transport in environmental stratified shear flows.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204422"},"PeriodicalIF":2.5,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Electroosmotic-driven unsteady mass transport of non-Newtonian fluids flow through a microchannel under the influence of thermal buoyancy and slip-induced zeta potential 在热浮力和滑移诱导zeta电位的影响下，电渗透驱动的非牛顿流体在微通道中的非定常质量输运

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-28 DOI: 10.1016/j.euromechflu.2025.204425

Raju Sen, Rishi Raj Kairi

The present work investigates the concentration profile of a passive contaminant in Casson biofluid flow through an electrically actuated medium. Specifically, we examine buoyancy-driven unsteady solute dispersion in electroosmotic electromagnetohydrodynamic flow within a microchannel. Also, the solute transport is influenced by the presence of slip-dependent zeta potential and temperature-induced heat sources. At the boundary, a first-order heterogeneous reaction governs the behavior of the tracer concentration. The time-dependent convection–diffusion equation is tackled by an advanced numerical scheme, Aris’s method of moments, to frame the moment equations, which are then solved by an implicit finite difference scheme. The first four central moments, expressed through a Hermite polynomial, are used to calculate the tracer’s mean concentration distribution. The results indicate that with enhanced internal heating and buoyancy force dispersion of solute increased, and thus, the peak of the mean concentration reduced. Under combined flow (steady + unsteady), the dispersion coefficients of the solute are hardly adjusted by the magnetic influence for slip-independent zeta potential. However, the effect of magnetic damping is comparatively stronger for slip-dependent zeta potential. In the presence of a weak internal heat source, for the small Casson parameter, the kurtosis approaches a Gaussian distribution, while for strong internal heating, the kurtosis stays negative throughout the chosen range, indicating a non-Gaussian behavior. In particular, an appropriate variation of thermally driven solute dispersion will provide much-needed control to biochemical reactions and diagnostics integrated into lab-on-a-chip devices and the separation of chemical species, and hence, speed up medical test results and make them reliable.

本研究调查了卡森生物流体中被动污染物通过电驱动介质的浓度分布。具体来说，我们研究了微通道内电渗透电磁流体动力流动中浮力驱动的非定常溶质分散。此外，溶质输运还受到依赖于滑移的zeta电位和温度诱导的热源的影响。在边界处，一阶非均相反应支配着示踪剂浓度的行为。随时间变化的对流扩散方程采用一种先进的数值格式，即Aris的矩量法来构造矩量方程，然后用隐式有限差分格式求解。通过Hermite多项式表示的前四个中心矩用于计算示踪剂的平均浓度分布。结果表明：随着内加热和浮力的增强，溶质的分散性增加，平均浓度峰值减小；在稳态+非稳态复合流动条件下，溶质的色散系数几乎不受与滑移无关的zeta势的磁影响。然而，磁阻尼对滑移相关zeta电位的影响相对较强。在弱内热源存在的情况下，对于小的Casson参数，峰度接近高斯分布，而对于强内加热，峰度在整个选择范围内保持负值，表明非高斯行为。特别是，热驱动溶质分散的适当变化将为集成到芯片实验室设备中的生化反应和诊断以及化学物质的分离提供急需的控制，从而加快医学测试结果并使其可靠。

{"title":"Electroosmotic-driven unsteady mass transport of non-Newtonian fluids flow through a microchannel under the influence of thermal buoyancy and slip-induced zeta potential","authors":"Raju Sen, Rishi Raj Kairi","doi":"10.1016/j.euromechflu.2025.204425","DOIUrl":"10.1016/j.euromechflu.2025.204425","url":null,"abstract":"<div><div>The present work investigates the concentration profile of a passive contaminant in Casson biofluid flow through an electrically actuated medium. Specifically, we examine buoyancy-driven unsteady solute dispersion in electroosmotic electromagnetohydrodynamic flow within a microchannel. Also, the solute transport is influenced by the presence of slip-dependent zeta potential and temperature-induced heat sources. At the boundary, a first-order heterogeneous reaction governs the behavior of the tracer concentration. The time-dependent convection–diffusion equation is tackled by an advanced numerical scheme, Aris’s method of moments, to frame the moment equations, which are then solved by an implicit finite difference scheme. The first four central moments, expressed through a Hermite polynomial, are used to calculate the tracer’s mean concentration distribution. The results indicate that with enhanced internal heating and buoyancy force dispersion of solute increased, and thus, the peak of the mean concentration reduced. Under combined flow (steady + unsteady), the dispersion coefficients of the solute are hardly adjusted by the magnetic influence for slip-independent zeta potential. However, the effect of magnetic damping is comparatively stronger for slip-dependent zeta potential. In the presence of a weak internal heat source, for the small Casson parameter, the kurtosis approaches a Gaussian distribution, while for strong internal heating, the kurtosis stays negative throughout the chosen range, indicating a non-Gaussian behavior. In particular, an appropriate variation of thermally driven solute dispersion will provide much-needed control to biochemical reactions and diagnostics integrated into lab-on-a-chip devices and the separation of chemical species, and hence, speed up medical test results and make them reliable.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204425"},"PeriodicalIF":2.5,"publicationDate":"2025-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Study on the dynamic evolution process of entrainment vortex at the horizontal inlet of a large low-head pump station 某大型低扬程泵站水平进口带涡动态演化过程研究

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-26 DOI: 10.1016/j.euromechflu.2025.204426

Fusheng Lv, Pingping Li, Weihua Xiao, Luoping Pan

Understanding hydraulic transients during the inlet process of a pump station is crucial for identifying the adverse effects of strong turbulence on its operation. Such an understanding can enhance the overall quality of the pump system and mitigate potential risks associated with hydraulic transients. This paper investigates the formation mechanism of suction vortices in the forebay of a pumping station under high flow rates and their impact on the inflow regime through numerical simulation. By employing the coupled three-dimensional Volume of Fluid (VOF) + Level Set method, the dynamic evolution of the entrained flow vortex was calculated, and the causes and impacts of the vortex on the hydraulic characteristics of the pump station inlet were analyzed. The significant correlation between the development of entrained vortices and the excessive inflow angle caused by severe flow deviation in the forebay was elucidated. This study provides a visualization method for the spatiotemporal evolution of internal vortices at the horizontal inlet of large low-head pumping stations. It aids in identifying the causes of uneven flow and vibration in the inlet system, thus offering theoretical support for the safe operation of pumping stations.

了解泵站入口过程中的水力瞬变对于确定强湍流对泵站运行的不利影响至关重要。这样的理解可以提高泵系统的整体质量，降低与液压瞬变相关的潜在风险。本文通过数值模拟研究了大流量下泵站前湾吸涡的形成机理及其对入流流态的影响。采用耦合三维流体体积(VOF) + 水平集方法，计算了夹带流涡的动态演化过程，分析了夹带流涡产生的原因及其对泵站进口水力特性的影响。阐明了夹带涡的发展与前湾严重的流偏引起的过大入流角之间的显著相关性。本研究为大型低水头泵站水平进水口内涡的时空演变提供了一种可视化方法。有助于查明进水口系统流动不均匀和振动的原因，为泵站的安全运行提供理论支持。

{"title":"Study on the dynamic evolution process of entrainment vortex at the horizontal inlet of a large low-head pump station","authors":"Fusheng Lv, Pingping Li, Weihua Xiao, Luoping Pan","doi":"10.1016/j.euromechflu.2025.204426","DOIUrl":"10.1016/j.euromechflu.2025.204426","url":null,"abstract":"<div><div>Understanding hydraulic transients during the inlet process of a pump station is crucial for identifying the adverse effects of strong turbulence on its operation. Such an understanding can enhance the overall quality of the pump system and mitigate potential risks associated with hydraulic transients. This paper investigates the formation mechanism of suction vortices in the forebay of a pumping station under high flow rates and their impact on the inflow regime through numerical simulation. By employing the coupled three-dimensional Volume of Fluid (VOF) + Level Set method, the dynamic evolution of the entrained flow vortex was calculated, and the causes and impacts of the vortex on the hydraulic characteristics of the pump station inlet were analyzed. The significant correlation between the development of entrained vortices and the excessive inflow angle caused by severe flow deviation in the forebay was elucidated. This study provides a visualization method for the spatiotemporal evolution of internal vortices at the horizontal inlet of large low-head pumping stations. It aids in identifying the causes of uneven flow and vibration in the inlet system, thus offering theoretical support for the safe operation of pumping stations.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204426"},"PeriodicalIF":2.5,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Modulating cerebrospinal fluid flow by magnetohydrodynamic force 磁流体动力对脑脊液流量的调节

IF 2.5 3区工程技术 Q2 MECHANICS

European Journal of Mechanics B-fluids

Pub Date : 2025-11-24 DOI: 10.1016/j.euromechflu.2025.204424

Mohammad Shamsodini Lori , Seyed Farzad Maroufi , Mohamad Ali Bijarchi , Mark G. Luciano , Zohreh Habibi , Jiangtao Cheng

Approximately one in 20,000 individuals experiences a neurological disorder each year due to disturbances in cerebrospinal fluid (CSF) flow within the brain's ventricles. Consequently, developing treatment methods to modify and regulate CSF flow is crucial for addressing these dilemmas. In this study, the effect of MagnetoHydroDynamic (MHD) force on the fluid flow characteristics of CSF inside a three-dimensional (3D) model of the Cerebral Ventricular System (CVS) is numerically investigated. Magnetic Resonance Imaging (MRI) is employed to rebuild the brain's geometry via image reconstruction software. Both invasive methods, which involve inserting electrodes and magnets into the brain, and non-invasive methods, which involve placing electrodes and magnets on the brain's surface, are studied numerically. The results of these two methods are then compared. Under MHD force, the pressure inside the third and lateral ventricles is reduced by 18 %. Additionally, there is a significant local increase in the CSF transportation speed from the third ventricle to the fourth ventricle. Furthermore, incorporating nanoparticles (NPs) strengthens the MHD force, resulting in an increased pressure differential between the third and fourth ventricles.

由于脑室内脑脊液（CSF）流动紊乱，每年大约有20,000人中有一人患有神经系统疾病。因此，发展治疗方法来改变和调节脑脊液流动是解决这些困境的关键。在本研究中，研究了磁流体动力（MHD）力对脑室系统（CVS）三维模型内脑脊液流体流动特性的影响。磁共振成像（MRI）通过图像重建软件重建大脑的几何形状。对侵入性方法和非侵入性方法进行了数值研究，前者涉及将电极和磁铁插入大脑，后者涉及将电极和磁铁放置在大脑表面。然后比较了这两种方法的结果。在MHD力作用下，第三脑室和侧脑室内的压力降低了18. %。此外，脑脊液从第三脑室到第四脑室的局部运输速度显著增加。此外，加入纳米颗粒（NPs）增强了MHD力，导致第三和第四心室之间的压差增加。

{"title":"Modulating cerebrospinal fluid flow by magnetohydrodynamic force","authors":"Mohammad Shamsodini Lori , Seyed Farzad Maroufi , Mohamad Ali Bijarchi , Mark G. Luciano , Zohreh Habibi , Jiangtao Cheng","doi":"10.1016/j.euromechflu.2025.204424","DOIUrl":"10.1016/j.euromechflu.2025.204424","url":null,"abstract":"<div><div>Approximately one in 20,000 individuals experiences a neurological disorder each year due to disturbances in cerebrospinal fluid (CSF) flow within the brain's ventricles. Consequently, developing treatment methods to modify and regulate CSF flow is crucial for addressing these dilemmas. In this study, the effect of MagnetoHydroDynamic (MHD) force on the fluid flow characteristics of CSF inside a three-dimensional (3D) model of the Cerebral Ventricular System (CVS) is numerically investigated. Magnetic Resonance Imaging (MRI) is employed to rebuild the brain's geometry via image reconstruction software. Both invasive methods, which involve inserting electrodes and magnets into the brain, and non-invasive methods, which involve placing electrodes and magnets on the brain's surface, are studied numerically. The results of these two methods are then compared. Under MHD force, the pressure inside the third and lateral ventricles is reduced by 18 %. Additionally, there is a significant local increase in the CSF transportation speed from the third ventricle to the fourth ventricle. Furthermore, incorporating nanoparticles (NPs) strengthens the MHD force, resulting in an increased pressure differential between the third and fourth ventricles.</div></div>","PeriodicalId":11985,"journal":{"name":"European Journal of Mechanics B-fluids","volume":"117 ","pages":"Article 204424"},"PeriodicalIF":2.5,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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