The large aspect ratio of a corridor-shaped air cushion surge chamber in hydropower systems results in special hydraulic and heat transfer characteristics that differ from those of cylindrical shapes. The complexities of inflow jet and outflow vortex phenomena at the throttle orifice, along with the thermal energy exchange across the water–air interface during load variations, continue to be areas of limited understanding. The hydraulic and heat transfer processes during the load variation conditions were simulated precisely using the volume of fluid model to address the above knowledge gap by adopting computational fluid dynamics. The effects of various parameters on pressure and flow patterns (including initial water depth, orifice size, aspect ratio of the surge chamber, and unit closure time) and the thermodynamic response of the air during the compression and expansion phases were analyzed. The results indicate that a smaller orifice size has larger Froude numbers, thus intensifying jet heights and exacerbating wave fluctuations. An increased initial water depth or a reduced aspect ratio of the corridor-shaped chamber decreases the angular velocity of the fluid above the orifice during load increase, thus attenuating the vortex intensity. A method for calculating the heat transfer rate in the chamber was developed by considering the heat exchanges between water, chamber wall, and air. The intense heat transfer at the water–air interface is caused by large wave fluctuations due to velocity gradients. In addition, larger orifice size increases the flow rate and heat transfer rate, leading to an increase in the total heat transfer coefficient of the chamber.
{"title":"Hydraulic and heat transfer characteristics in corridor-shaped air-cushion surge chambers in hydropower systems","authors":"Jiachun Liu, Yongguang Cheng, Jianyong Hu, Xiaodong Yu","doi":"10.1063/5.0218288","DOIUrl":"https://doi.org/10.1063/5.0218288","url":null,"abstract":"The large aspect ratio of a corridor-shaped air cushion surge chamber in hydropower systems results in special hydraulic and heat transfer characteristics that differ from those of cylindrical shapes. The complexities of inflow jet and outflow vortex phenomena at the throttle orifice, along with the thermal energy exchange across the water–air interface during load variations, continue to be areas of limited understanding. The hydraulic and heat transfer processes during the load variation conditions were simulated precisely using the volume of fluid model to address the above knowledge gap by adopting computational fluid dynamics. The effects of various parameters on pressure and flow patterns (including initial water depth, orifice size, aspect ratio of the surge chamber, and unit closure time) and the thermodynamic response of the air during the compression and expansion phases were analyzed. The results indicate that a smaller orifice size has larger Froude numbers, thus intensifying jet heights and exacerbating wave fluctuations. An increased initial water depth or a reduced aspect ratio of the corridor-shaped chamber decreases the angular velocity of the fluid above the orifice during load increase, thus attenuating the vortex intensity. A method for calculating the heat transfer rate in the chamber was developed by considering the heat exchanges between water, chamber wall, and air. The intense heat transfer at the water–air interface is caused by large wave fluctuations due to velocity gradients. In addition, larger orifice size increases the flow rate and heat transfer rate, leading to an increase in the total heat transfer coefficient of the chamber.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940554","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}
Right- and left-handed propellers translate in opposite directions when rotated in the same direction. The same phenomenon may occur with enantiomorphic objects. In this paper, enantiomorphic octahedrons and tetrahedrons were fabricated using a 3D printer and rotated in a liquid medium. The rotation axis was determined by solving an eigenvalue problem for the shape tensor that hydrodynamically characterizes the shape of these polyhedrons. The model exhibited propeller-like motion, indicating the possibility of separating enantiomorphic objects.
右旋螺旋桨和左旋螺旋桨在同方向旋转时的平移方向是相反的。对映体也可能出现同样的现象。本文使用 3D 打印机制作了对映体八面体和四面体，并在液体介质中旋转。旋转轴是通过求解形状张量的特征值问题确定的，而形状张量是这些多面体形状的流体力学特征。该模型表现出类似螺旋桨的运动，表明有可能分离对映体。
{"title":"Chiral separation of enantiomorphic objects by rotation in a fluid","authors":"Ryoma Kimura, Tsunehisa Kimura, Kazuya Furusawa","doi":"10.1063/5.0213550","DOIUrl":"https://doi.org/10.1063/5.0213550","url":null,"abstract":"Right- and left-handed propellers translate in opposite directions when rotated in the same direction. The same phenomenon may occur with enantiomorphic objects. In this paper, enantiomorphic octahedrons and tetrahedrons were fabricated using a 3D printer and rotated in a liquid medium. The rotation axis was determined by solving an eigenvalue problem for the shape tensor that hydrodynamically characterizes the shape of these polyhedrons. The model exhibited propeller-like motion, indicating the possibility of separating enantiomorphic objects.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940551","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}
Changming Li, Bingchen Liang, Peng Yuan, Qin Zhang, Yongkai Liu, Bin Liu, Ming Zhao
Efficiently predicting the wake of propellers is of great importance for achieving propeller design optimization. In this work, the deep learning (DL) method called propeller wake convolutional neural networks (PWCNN) is proposed, which combines the transformer encoder and dilated convolutional block to capture the multi-scale characteristics of wakes. Computational fluid dynamics (CFD) simulations are conducted using the delayed detached eddy simulation model for the wake to generate extensive high-fidelity wake data of the propeller operating under different operating conditions required for DL. PWCNN takes the wake predicted at the previous time step to update input and iteratively predicts the wake at future time steps to achieve dynamic wake prediction. The good agreement between DL prediction and CFD simulation results, with the mean relative error of the velocity components less than 2.36% for 15 future time steps, proves that PWCNN can efficiently capture the spatiotemporal evolution characteristic of dynamic wakes. Furthermore, PWCNN can predict the wake dynamic changes with reasonable accuracy under unseen operating conditions, further confirming the generality of the proposed model in forecasting the spatiotemporal evolution of propeller wake.
{"title":"Fast prediction of propeller dynamic wake based on deep learning","authors":"Changming Li, Bingchen Liang, Peng Yuan, Qin Zhang, Yongkai Liu, Bin Liu, Ming Zhao","doi":"10.1063/5.0220551","DOIUrl":"https://doi.org/10.1063/5.0220551","url":null,"abstract":"Efficiently predicting the wake of propellers is of great importance for achieving propeller design optimization. In this work, the deep learning (DL) method called propeller wake convolutional neural networks (PWCNN) is proposed, which combines the transformer encoder and dilated convolutional block to capture the multi-scale characteristics of wakes. Computational fluid dynamics (CFD) simulations are conducted using the delayed detached eddy simulation model for the wake to generate extensive high-fidelity wake data of the propeller operating under different operating conditions required for DL. PWCNN takes the wake predicted at the previous time step to update input and iteratively predicts the wake at future time steps to achieve dynamic wake prediction. The good agreement between DL prediction and CFD simulation results, with the mean relative error of the velocity components less than 2.36% for 15 future time steps, proves that PWCNN can efficiently capture the spatiotemporal evolution characteristic of dynamic wakes. Furthermore, PWCNN can predict the wake dynamic changes with reasonable accuracy under unseen operating conditions, further confirming the generality of the proposed model in forecasting the spatiotemporal evolution of propeller wake.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940490","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}
A new analytical model for the generation of axisymmetric tornado-type vortices has been developed. A solution to the nonlinear equation for the stream function in an unstable stratified atmosphere is obtained and analyzed within the framework of ideal hydrodynamics. The solution is sought by smooth connecting continuous solutions for the internal region (eye), the central region (“wall” with maximum velocities), and the external region of the tornado. Expressions describing radial dependences for the radial and vertical velocity components include combinations of Bessel functions. The vortex is spatially localized by radius and height. Convective instability of a stratified atmosphere leads to an increase in the radial and vertical components of velocities according to the hyperbolic sine law. A downward flow is observed near the tornado axis. The maximum speed of the upward flow is achieved at a certain radial distance at a certain height. Below this height, radial flows converge toward the central part of the tornado, and above this height, there is an outflow from the wall to the axis and to the periphery. The radial structure of the azimuthal velocity is determined by the structure of the initial disturbance and can change with height. Maximum rotation is achieved in the tornado wall at a certain height. The increase in azimuthal velocity can occur according to a superexponential law. Possible structures of movements, scenarios for the development of a tornado, and its dynamics are discussed.
{"title":"An analytical model of tornado generation","authors":"S. N. Artekha","doi":"10.1063/5.0213431","DOIUrl":"https://doi.org/10.1063/5.0213431","url":null,"abstract":"A new analytical model for the generation of axisymmetric tornado-type vortices has been developed. A solution to the nonlinear equation for the stream function in an unstable stratified atmosphere is obtained and analyzed within the framework of ideal hydrodynamics. The solution is sought by smooth connecting continuous solutions for the internal region (eye), the central region (“wall” with maximum velocities), and the external region of the tornado. Expressions describing radial dependences for the radial and vertical velocity components include combinations of Bessel functions. The vortex is spatially localized by radius and height. Convective instability of a stratified atmosphere leads to an increase in the radial and vertical components of velocities according to the hyperbolic sine law. A downward flow is observed near the tornado axis. The maximum speed of the upward flow is achieved at a certain radial distance at a certain height. Below this height, radial flows converge toward the central part of the tornado, and above this height, there is an outflow from the wall to the axis and to the periphery. The radial structure of the azimuthal velocity is determined by the structure of the initial disturbance and can change with height. Maximum rotation is achieved in the tornado wall at a certain height. The increase in azimuthal velocity can occur according to a superexponential law. Possible structures of movements, scenarios for the development of a tornado, and its dynamics are discussed.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940557","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}
Reduced-order models (ROMs) can effectively balance the accuracy and efficiency of computational fluid dynamics (CFD). The nonlinear flow field characteristics cannot be captured accurately by traditional ROMs, such as proper orthogonal decomposition (POD). Combining isometric mapping (ISOMAP) and local linear embedding (LLE), a novel manifold learning method (ISOMAP-Local LLE) is proposed, performing global and accurate reconstruction of the nonlinear flow field. First, the nonlinear dimensionality reduction is derived by considering the global isometric characteristic and the local reconstruction relationship simultaneously. Then, the local interpolation model is constructed to improve the interpolation accuracy introduced by the global interpolation model. Finally, the flow field reconstruction is accomplished based on the inverse mapping. Furthermore, the criteria of hyperparameters have been established to achieve high-precision prediction. Several examples covering full speed flow field are carried out to demonstrate the accuracy and efficiency of ISOMAP-Local LLE. The proposed manifold learning-based ROM achieves prediction accuracy that surpasses that of other ROMs (such as POD, ISOMAP, LLE, etc.), resulting in significant time cost savings for CFD simulations.
降阶模型（ROM）能有效平衡计算流体动力学（CFD）的精度和效率。传统的 ROM（如适当正交分解（POD））无法准确捕捉非线性流场特征。本文结合等距映射（ISOMAP）和局部线性嵌入（LLE），提出了一种新型流形学习方法（ISOMAP-局部 LLE），对非线性流场进行全局和精确的重建。首先，通过同时考虑全局等距特征和局部重建关系，得出了非线性降维方法。然后，构建局部插值模型，以提高全局插值模型带来的插值精度。最后，根据反映射完成流场重建。此外，还建立了超参数标准，以实现高精度预测。为了证明 ISOMAP-Local LLE 的准确性和效率，我们进行了几个涵盖全速流场的示例。所提出的基于流形学习的 ROM 预测精度超过了其他 ROM（如 POD、ISOMAP、LLE 等），为 CFD 模拟节省了大量时间成本。
{"title":"Manifold learning-based reduced-order model for full speed flow field","authors":"Ruixue Li, Shufang Song","doi":"10.1063/5.0211689","DOIUrl":"https://doi.org/10.1063/5.0211689","url":null,"abstract":"Reduced-order models (ROMs) can effectively balance the accuracy and efficiency of computational fluid dynamics (CFD). The nonlinear flow field characteristics cannot be captured accurately by traditional ROMs, such as proper orthogonal decomposition (POD). Combining isometric mapping (ISOMAP) and local linear embedding (LLE), a novel manifold learning method (ISOMAP-Local LLE) is proposed, performing global and accurate reconstruction of the nonlinear flow field. First, the nonlinear dimensionality reduction is derived by considering the global isometric characteristic and the local reconstruction relationship simultaneously. Then, the local interpolation model is constructed to improve the interpolation accuracy introduced by the global interpolation model. Finally, the flow field reconstruction is accomplished based on the inverse mapping. Furthermore, the criteria of hyperparameters have been established to achieve high-precision prediction. Several examples covering full speed flow field are carried out to demonstrate the accuracy and efficiency of ISOMAP-Local LLE. The proposed manifold learning-based ROM achieves prediction accuracy that surpasses that of other ROMs (such as POD, ISOMAP, LLE, etc.), resulting in significant time cost savings for CFD simulations.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940657","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}
In this article, based on finite element discretization, we propose some improved defect-correction algorithms for solving the stationary Navier–Stokes equations with small viscosity. The proposed algorithms are mainly inspired by the idea of the grad-div stabilized method and error correction technique. Maintaining the benefit of the usual defect-correction method, the proposed algorithms further improve the ability to solve problems with small viscosity and have a fast convergence rate. Moreover, stability analysis and error estimation of these algorithms are provided under the uniqueness requirement. Finally, some numerical experiments are tested to illustrate the effectiveness of the presented algorithms for small viscosity problem.
{"title":"Improved defect-correction algorithms for the Navier–Stokes equations at small viscosity","authors":"Qi Zhang, Pengzhan Huang","doi":"10.1063/5.0221701","DOIUrl":"https://doi.org/10.1063/5.0221701","url":null,"abstract":"In this article, based on finite element discretization, we propose some improved defect-correction algorithms for solving the stationary Navier–Stokes equations with small viscosity. The proposed algorithms are mainly inspired by the idea of the grad-div stabilized method and error correction technique. Maintaining the benefit of the usual defect-correction method, the proposed algorithms further improve the ability to solve problems with small viscosity and have a fast convergence rate. Moreover, stability analysis and error estimation of these algorithms are provided under the uniqueness requirement. Finally, some numerical experiments are tested to illustrate the effectiveness of the presented algorithms for small viscosity problem.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940628","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}
Lin Huang, Jiahui Dong, Qi Wang, Haili Liao, Mingshui Li
The Π-type steel-concrete composite girder, a commonly used bridge deck composed of an upper concrete slab and two lower lateral I-side steel girders, often suffers from severe vortex-induced vibrations (VIVs). Herein, the VIV response and triggering mechanism of a Π-type girder are systematically investigated, by adopting 1:50 scale section model wind tunnel tests and flow-field numerical simulations. Afterward, several aerodynamic measures were designed to mitigate the significant VIVs present in the original section, and an effective measure composed of the G-shaped apron and lower central stabilizer plate was found. Numerical simulation results show that the Π-type girder's upper and lower surfaces both exhibit severe vortex shedding, and both contribute significantly to the occurrence of VIVs. Consequently, the aerodynamic measures introduced for the Π-type girder must be able to simultaneously improve the flowing bypassing situation around the upper and lower surfaces of the section, and the G-shaped apron and the lower central stabilizer plate could both accomplish this simultaneously. The results show that the VIV suppression effect of this G-shaped apron combination measure is greatly affected by the height of the G-shaped apron's vertical plate and the height of the lower central stabilizer plate. Only both of them to a certain height, this measure can entirely prevent the Π-type girder from VIVs. After shape optimization, a G-shaped apron combination aerodynamic measure that can eliminate completely the Π-type girder's VIVs at low damping ratios of about 0.5% is proposed, of which the vibration-suppressing effect was verified by wind tunnel testing of 1:20 section model.
Π型钢-混凝土组合梁是一种常用的桥面结构，由上部混凝土板和下部横向两片工字钢梁组成，经常会产生严重的涡激振动（VIVs）。本文采用 1:50 比例截面模型风洞试验和流场数值模拟，系统研究了 Π 型梁的 VIV 响应和触发机制。随后，设计了几种空气动力措施来缓解原断面存在的显著 VIV，并找到了一种由 G 型挡板和下部中央稳定板组成的有效措施。数值模拟结果表明，Π 型大梁的上表面和下表面都出现了严重的涡流脱落现象，这两种现象对 VIVs 的发生有很大的影响。因此，为 Π 型大梁引入的空气动力措施必须能够同时改善截面上下表面的绕流情况，而 G 型挡板和下部中央稳定板可同时实现这一目标。结果表明，这种 G 型围裙组合措施的 VIV 抑制效果受 G 型围裙竖板高度和下中央稳定板高度的影响很大。只有两者都达到一定高度，该措施才能完全防止Π型梁发生 VIV。经过形状优化，提出了一种在约 0.5% 的低阻尼比下可完全消除 Π 型大梁 VIV 的 G 型围裙组合气动措施，并通过 1:20 截面模型的风洞试验验证了其抑振效果。
{"title":"Investigation of vortex-induced vibration of a Π-type bridge girder and its suppression using G-shaped apron combination measure","authors":"Lin Huang, Jiahui Dong, Qi Wang, Haili Liao, Mingshui Li","doi":"10.1063/5.0219497","DOIUrl":"https://doi.org/10.1063/5.0219497","url":null,"abstract":"The Π-type steel-concrete composite girder, a commonly used bridge deck composed of an upper concrete slab and two lower lateral I-side steel girders, often suffers from severe vortex-induced vibrations (VIVs). Herein, the VIV response and triggering mechanism of a Π-type girder are systematically investigated, by adopting 1:50 scale section model wind tunnel tests and flow-field numerical simulations. Afterward, several aerodynamic measures were designed to mitigate the significant VIVs present in the original section, and an effective measure composed of the G-shaped apron and lower central stabilizer plate was found. Numerical simulation results show that the Π-type girder's upper and lower surfaces both exhibit severe vortex shedding, and both contribute significantly to the occurrence of VIVs. Consequently, the aerodynamic measures introduced for the Π-type girder must be able to simultaneously improve the flowing bypassing situation around the upper and lower surfaces of the section, and the G-shaped apron and the lower central stabilizer plate could both accomplish this simultaneously. The results show that the VIV suppression effect of this G-shaped apron combination measure is greatly affected by the height of the G-shaped apron's vertical plate and the height of the lower central stabilizer plate. Only both of them to a certain height, this measure can entirely prevent the Π-type girder from VIVs. After shape optimization, a G-shaped apron combination aerodynamic measure that can eliminate completely the Π-type girder's VIVs at low damping ratios of about 0.5% is proposed, of which the vibration-suppressing effect was verified by wind tunnel testing of 1:20 section model.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940623","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}
This study investigates magnetosonic shock waves in a spin-polarized three-component quantum plasma using the quantum magnetic hydrodynamic model. We explore the influence of spin effects, specifically spin magnetization current and spin pressure, on shock wave behavior. Numerical analysis of the linear dispersion relation under varying parameters such as positron imbalance, spin polarization ratio, plasma beta, quantum diffraction, and magnetic diffusivity reveals differential impacts, with diffusion exerting significant influence on the plasma frequency. Our findings highlight the sensitivity discrepancy between the real and imaginary parts of the dispersion relation. Furthermore, nonlinear behavior of magnetosonic shock waves is examined via the Korteweg–de Vries–Burgers equation, showcasing transitions between oscillatory and monotonic wave patterns based on changes in dimensionless parameters. Notably, we observe the combined effects of spin-up and spin-down positrons with spin-up and spin-down electrons on shock wave dynamics, contributing to a deeper understanding of spin-plasma interactions with implications across various fields.
{"title":"Magnetosonic shock waves in degenerate electron–positron–ion plasma with separated spin densities","authors":"Mansoor Ahmad, Muhammad Adnan, Anisa Qamar","doi":"10.1063/5.0216452","DOIUrl":"https://doi.org/10.1063/5.0216452","url":null,"abstract":"This study investigates magnetosonic shock waves in a spin-polarized three-component quantum plasma using the quantum magnetic hydrodynamic model. We explore the influence of spin effects, specifically spin magnetization current and spin pressure, on shock wave behavior. Numerical analysis of the linear dispersion relation under varying parameters such as positron imbalance, spin polarization ratio, plasma beta, quantum diffraction, and magnetic diffusivity reveals differential impacts, with diffusion exerting significant influence on the plasma frequency. Our findings highlight the sensitivity discrepancy between the real and imaginary parts of the dispersion relation. Furthermore, nonlinear behavior of magnetosonic shock waves is examined via the Korteweg–de Vries–Burgers equation, showcasing transitions between oscillatory and monotonic wave patterns based on changes in dimensionless parameters. Notably, we observe the combined effects of spin-up and spin-down positrons with spin-up and spin-down electrons on shock wave dynamics, contributing to a deeper understanding of spin-plasma interactions with implications across various fields.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940630","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}
To comprehensively understand the dynamic behavior of muzzle bubbles during underwater launching, an emptying process aligned with the muzzle flow characteristics is established and an evaporative condensation mechanism is modeled according to the high temperature and pressure properties of the propellant gas. Utilizing the spherical bubble theory, which comprises the inflation process and evaporative condensation effects, the dynamics of muzzle bubbles and their corresponding pressure waves are investigated. The numerical simulation results well agree with the experimental observations in terms of bubble radius and near-field pressure waves. Furthermore, the influence of two key factors on the bubble dynamics is examined: underwater launching depth and initial muzzle pressures. The results illustrate that the inflation process needs to be accurately described for precise pressure wave predictions. Using the evaporation condensation model, the bubble radius and frequency can be accurately characterized. Moreover, the launching depth influences the free expansion radius and oscillation frequency mostly due to the increase in hydrostatic pressure, which decreases by 33% and increases by 150% in the 1–20 m range, respectively. The initial muzzle pressure affects the initial expansion velocity and initial shock wave mainly due to the increase in the mass flow rate, which increase by 56% and 82% in the 35–65 MPa range, respectively.
{"title":"Muzzle bubble dynamics characterization of underwater launching","authors":"Zhiqun Sun, Qiang Li, Xuewei Zhang, Pu Qu, Lin Lu","doi":"10.1063/5.0222463","DOIUrl":"https://doi.org/10.1063/5.0222463","url":null,"abstract":"To comprehensively understand the dynamic behavior of muzzle bubbles during underwater launching, an emptying process aligned with the muzzle flow characteristics is established and an evaporative condensation mechanism is modeled according to the high temperature and pressure properties of the propellant gas. Utilizing the spherical bubble theory, which comprises the inflation process and evaporative condensation effects, the dynamics of muzzle bubbles and their corresponding pressure waves are investigated. The numerical simulation results well agree with the experimental observations in terms of bubble radius and near-field pressure waves. Furthermore, the influence of two key factors on the bubble dynamics is examined: underwater launching depth and initial muzzle pressures. The results illustrate that the inflation process needs to be accurately described for precise pressure wave predictions. Using the evaporation condensation model, the bubble radius and frequency can be accurately characterized. Moreover, the launching depth influences the free expansion radius and oscillation frequency mostly due to the increase in hydrostatic pressure, which decreases by 33% and increases by 150% in the 1–20 m range, respectively. The initial muzzle pressure affects the initial expansion velocity and initial shock wave mainly due to the increase in the mass flow rate, which increase by 56% and 82% in the 35–65 MPa range, respectively.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940625","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}
The present study concerns the numerical modeling of microbubble oscillation within an elastic microvessel, aiming to enhance the safety and efficacy of ultrasound-mediated drug delivery and diagnostic imaging. The success of such applications depends on a thorough understanding of microbubble–vessel interactions. Despite some progress, the critical impact of the stabilizing shell around gas core has remained underexplored. To address this, we developed a novel numerical approach that models the stabilizing shell. Additionally, there is novelty in modeling consequent vascular deformation in response to complicated spatiotemporal microbubble oscillations. The novel approach was implemented for shear stress evaluation as a critical factor in vascular permeability. Finally, our unique approach offered novel insights into microbubble–vessel interactions under diverse acoustic conditions. Results indicated substantial impact of shell properties and acoustic parameters on induced shear stress. With a fourfold increase in acoustic pressure amplitude, 15.6-fold and sixfold increases were observed in maximum shear stress at 1 and 3 MHz, respectively. Also, the peak shear stress could reach up to 15.6 kPa for a shell elasticity of 0.2 N/m at 2.5 MHz. Furthermore, decreasing microvessel/bubble size ratio from 3 to 1.5 increased maximum shear stress from 5.1 to 24.3 kPa. These findings are crucial for optimizing ultrasound parameters in clinical applications, potentially improving treatment outcomes while minimizing risk of vessel damage. However, while our model demonstrated high fidelity in reproducing experimental observations, it is limited by assumptions of vessel geometry and homogeneity of vessel properties. Future work can improve our findings through in vitro experimental measurements.
{"title":"Numerical analysis of ultrasound-mediated microbubble interactions in vascular systems: Effects on shear stress and vessel mechanics","authors":"Zeinab Heidary, Claus-Dieter Ohl, Afsaneh Mojra","doi":"10.1063/5.0213656","DOIUrl":"https://doi.org/10.1063/5.0213656","url":null,"abstract":"The present study concerns the numerical modeling of microbubble oscillation within an elastic microvessel, aiming to enhance the safety and efficacy of ultrasound-mediated drug delivery and diagnostic imaging. The success of such applications depends on a thorough understanding of microbubble–vessel interactions. Despite some progress, the critical impact of the stabilizing shell around gas core has remained underexplored. To address this, we developed a novel numerical approach that models the stabilizing shell. Additionally, there is novelty in modeling consequent vascular deformation in response to complicated spatiotemporal microbubble oscillations. The novel approach was implemented for shear stress evaluation as a critical factor in vascular permeability. Finally, our unique approach offered novel insights into microbubble–vessel interactions under diverse acoustic conditions. Results indicated substantial impact of shell properties and acoustic parameters on induced shear stress. With a fourfold increase in acoustic pressure amplitude, 15.6-fold and sixfold increases were observed in maximum shear stress at 1 and 3 MHz, respectively. Also, the peak shear stress could reach up to 15.6 kPa for a shell elasticity of 0.2 N/m at 2.5 MHz. Furthermore, decreasing microvessel/bubble size ratio from 3 to 1.5 increased maximum shear stress from 5.1 to 24.3 kPa. These findings are crucial for optimizing ultrasound parameters in clinical applications, potentially improving treatment outcomes while minimizing risk of vessel damage. However, while our model demonstrated high fidelity in reproducing experimental observations, it is limited by assumptions of vessel geometry and homogeneity of vessel properties. Future work can improve our findings through in vitro experimental measurements.","PeriodicalId":20066,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141940622","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}
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