Xue Deng, Mingming Guo, Yi Zhang, Ye Tian, Jingrun Wu, Heng Wang, Hua Zhang, Jialing Le
To alleviate the problem of high-fidelity data dependence and inexplicability in pure data-driven neural network models, physical informed neural networks (PINNs) provide a new learning paradigm. This study constructs an efficient, accurate, and robust PINN framework for predicting unsteady combustion flow fields based on Navier–Stokes (NS) equation constraints. To achieve fast prediction of a multi-physical field in a scramjet combustion chamber, we propose a U-shaped residual neural network model based on feature information fusion. The model uses a residual neural network module as the backbone, uses jump connection to improve model generalization, and uses the U-shaped structure to fuse the receptive field features with different scales to enhance the feature expression ability of the model. To prevent improper assumptions from leading to wrong method constraints, we consider the flow characteristic mechanism of each physical field to constrain the neural network and verify its accuracy through numerical simulation of the unsteady flow field in the scramjet combustor with Mach number (Ma) 2.0. This method can accurately predict the multi-physical field of unsteady turbulent combustion based on the time, space, Ma and turbulent eddy viscosity coefficients of a small number of samples. Specially, the proposed physical driven and data driven fusion proxy model can predict the unsteady combustion flow field in milliseconds. It has important reference value to solve the problem of low calculation efficiency of a traditional numerical simulation method of a combustion process.
为了缓解纯数据驱动神经网络模型中的高保真数据依赖性和不可解释性问题，物理信息神经网络（PINN）提供了一种新的学习范式。本研究基于纳维-斯托克斯（Navier-Stokes，NS）方程约束条件，构建了一个高效、准确、稳健的 PINN 框架，用于预测非稳态燃烧流场。为了实现对scramjet燃烧室中多物理场的快速预测，我们提出了一种基于特征信息融合的U型残差神经网络模型。该模型以残差神经网络模块为骨干，利用跳跃连接提高模型泛化能力，并利用 U 型结构融合不同尺度的感受野特征，增强模型的特征表达能力。为防止不当假设导致方法约束错误，我们考虑了各物理场的流动特征机理来约束神经网络，并通过对马赫数（Ma）为 2.0 的争气式喷气燃烧器内的非稳定流场进行数值模拟来验证其准确性。该方法可以根据少量样本的时间、空间、马赫数和湍流涡粘系数准确预测非稳定湍流燃烧的多物理场。特别是，所提出的物理驱动和数据驱动融合代理模型可在毫秒级时间内预测非稳定燃烧流场。这对解决传统燃烧过程数值模拟方法计算效率低的问题具有重要的参考价值。
{"title":"Intelligent reconstruction of unsteady combustion flow field of scramjet based on physical information constraints","authors":"Xue Deng, Mingming Guo, Yi Zhang, Ye Tian, Jingrun Wu, Heng Wang, Hua Zhang, Jialing Le","doi":"10.1063/5.0217991","DOIUrl":"https://doi.org/10.1063/5.0217991","url":null,"abstract":"To alleviate the problem of high-fidelity data dependence and inexplicability in pure data-driven neural network models, physical informed neural networks (PINNs) provide a new learning paradigm. This study constructs an efficient, accurate, and robust PINN framework for predicting unsteady combustion flow fields based on Navier–Stokes (NS) equation constraints. To achieve fast prediction of a multi-physical field in a scramjet combustion chamber, we propose a U-shaped residual neural network model based on feature information fusion. The model uses a residual neural network module as the backbone, uses jump connection to improve model generalization, and uses the U-shaped structure to fuse the receptive field features with different scales to enhance the feature expression ability of the model. To prevent improper assumptions from leading to wrong method constraints, we consider the flow characteristic mechanism of each physical field to constrain the neural network and verify its accuracy through numerical simulation of the unsteady flow field in the scramjet combustor with Mach number (Ma) 2.0. This method can accurately predict the multi-physical field of unsteady turbulent combustion based on the time, space, Ma and turbulent eddy viscosity coefficients of a small number of samples. Specially, the proposed physical driven and data driven fusion proxy model can predict the unsteady combustion flow field in milliseconds. It has important reference value to solve the problem of low calculation efficiency of a traditional numerical simulation method of a combustion process.","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141703505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The drop-on-demand electrohydrodynamic (EHD) printing is promising for manufacturing high-resolution dot arrays. Such dot fabrication is commonly achieved through two printing modes (jet/droplet mode), i.e., continuous jet directly flying to or broken jet induced droplet depositing in the substrate. The droplet mode commonly has a higher printing frequency than the jet mode, indicating the droplet mode's advantage in drop-on-demand EHD printing. However, most research on EHD printing focuses on the jet mode, which causes the mechanism of droplet production through jet pinch-off remains unclear. This study employs an arbitrary Lagrangian–Eulerian method capable of getting a sharp interface to reveal the pinch-off mechanism. First, the development of a tip streaming from a meniscus to the pinch-off is analyzed. It is found that the high pressure at the neck is the main reason for the pinch-off of the jet into the droplet. Second, the EHD phase diagram in the parameter space of We–Cae is plotted, where We is the Weber number and Cae is the electric capillary number. Finally, the important influences of the charge relaxation on the EHD tip streaming jet's breakup behavior and the generated droplets' properties are revealed. Evolutions of the droplet's properties, including radius, velocity, and charge, with varying charge relaxation parameters are offered. These properties of the droplet show their relationships with extreme values as a function of the charge relaxation parameter. This work can serve as the theoretical basis for tuning the EHD printing manufacturing performance.
{"title":"Pinch-off dynamics of an electrohydrodynamic tip streaming jet transforming into the microdroplet","authors":"Guozhen Wang, Wei Chen, Jiankui Chen, Chao Hu, Hao Chen, Zhouping Yin","doi":"10.1063/5.0215316","DOIUrl":"https://doi.org/10.1063/5.0215316","url":null,"abstract":"The drop-on-demand electrohydrodynamic (EHD) printing is promising for manufacturing high-resolution dot arrays. Such dot fabrication is commonly achieved through two printing modes (jet/droplet mode), i.e., continuous jet directly flying to or broken jet induced droplet depositing in the substrate. The droplet mode commonly has a higher printing frequency than the jet mode, indicating the droplet mode's advantage in drop-on-demand EHD printing. However, most research on EHD printing focuses on the jet mode, which causes the mechanism of droplet production through jet pinch-off remains unclear. This study employs an arbitrary Lagrangian–Eulerian method capable of getting a sharp interface to reveal the pinch-off mechanism. First, the development of a tip streaming from a meniscus to the pinch-off is analyzed. It is found that the high pressure at the neck is the main reason for the pinch-off of the jet into the droplet. Second, the EHD phase diagram in the parameter space of We–Cae is plotted, where We is the Weber number and Cae is the electric capillary number. Finally, the important influences of the charge relaxation on the EHD tip streaming jet's breakup behavior and the generated droplets' properties are revealed. Evolutions of the droplet's properties, including radius, velocity, and charge, with varying charge relaxation parameters are offered. These properties of the droplet show their relationships with extreme values as a function of the charge relaxation parameter. This work can serve as the theoretical basis for tuning the EHD printing manufacturing performance.","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141711094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we investigate the concentration and cavitation phenomena of Riemann solutions for the generalized Chaplygin gas equations in the presence of flux approximation. The concentration and cavitation are fundamental and physical phenomena in fluid dynamics, which can be mathematically described by delta shock waves and vacuums (or constant density states), respectively. The main objective of this paper is to rigorously investigate the formation of delta shock waves and constant density states and observe the concentration and cavitation phenomena. First, the Riemann problem for the generalized Chaplygin gas equations under the flux approximation is solved constructively. Although the system is strictly hyperbolic and its two characteristic fields are genuinely nonlinear, the delta shock wave arises in Riemann solutions. The formation of mechanism for delta shock wave is analyzed, that is, the 1-shock wave curve and the 2-shock wave curve do not intersect each other in the phase plane. Second, it is rigorously proved that, as the pressure vanishes, the Riemann solutions for the generalized Chaplygin gas equations under the flux approximation tend to the two kinds of Riemann solutions to the transport equations in zero-pressure flow under the flux approximation, which include a delta shock wave formed by a weighted δ-measure and a constant density state.
{"title":"Concentration and cavitation phenomena of Riemann solutions for the generalized Chaplygin gas equations under the flux approximation","authors":"Zhiqiang Shao, Meixiang Huang","doi":"10.1063/5.0216565","DOIUrl":"https://doi.org/10.1063/5.0216565","url":null,"abstract":"In this paper, we investigate the concentration and cavitation phenomena of Riemann solutions for the generalized Chaplygin gas equations in the presence of flux approximation. The concentration and cavitation are fundamental and physical phenomena in fluid dynamics, which can be mathematically described by delta shock waves and vacuums (or constant density states), respectively. The main objective of this paper is to rigorously investigate the formation of delta shock waves and constant density states and observe the concentration and cavitation phenomena. First, the Riemann problem for the generalized Chaplygin gas equations under the flux approximation is solved constructively. Although the system is strictly hyperbolic and its two characteristic fields are genuinely nonlinear, the delta shock wave arises in Riemann solutions. The formation of mechanism for delta shock wave is analyzed, that is, the 1-shock wave curve and the 2-shock wave curve do not intersect each other in the phase plane. Second, it is rigorously proved that, as the pressure vanishes, the Riemann solutions for the generalized Chaplygin gas equations under the flux approximation tend to the two kinds of Riemann solutions to the transport equations in zero-pressure flow under the flux approximation, which include a delta shock wave formed by a weighted δ-measure and a constant density state.","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141691975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to enhance the performance of the two-dimensional exhaust system during high-speed cruising and enhance aircraft survivability against infrared-guided weaponry, this study undertakes a systematic optimization of the geometric and thermodynamic parameters governing the two-dimensional exhaust system. The optimization objectives encompass augmenting both the discharge coefficient and the thrust coefficient of the nozzle while concurrently mitigating the infrared radiation intensity emanating in the tail direction. Imposing limitations on the infrared radiation intensity across diverse detection angles, the study further imposes constraints on the thrust efficiency and deflection efficiency of the thrust vectoring nozzle subsequent to a 15° deflection. Such measures ensure the maintenance of optimal stealth capabilities across all detection angles while preserving the unhampered thrust vectoring performance of the nozzle. This study employs the optimal Latin hypercube method and Kriging surrogate models in conjunction with collaborative optimization techniques to address multidisciplinary design optimization challenges. Comparative analyses with the initial design revealed significant enhancements: up to a 2.88% increase in the discharge coefficient, a maximum 0.53% increase in the thrust coefficient, and a notable reduction of up to 17.09% in tail direction dimensionless infrared radiation intensity, validating the effectiveness of the optimized exhaust system design.
{"title":"Collaborative optimization of two-dimensional convergent divergent exhaust system based on Kriging model","authors":"Lan Bo, Qiang Wang, Haiyang Hu","doi":"10.1063/5.0215032","DOIUrl":"https://doi.org/10.1063/5.0215032","url":null,"abstract":"In order to enhance the performance of the two-dimensional exhaust system during high-speed cruising and enhance aircraft survivability against infrared-guided weaponry, this study undertakes a systematic optimization of the geometric and thermodynamic parameters governing the two-dimensional exhaust system. The optimization objectives encompass augmenting both the discharge coefficient and the thrust coefficient of the nozzle while concurrently mitigating the infrared radiation intensity emanating in the tail direction. Imposing limitations on the infrared radiation intensity across diverse detection angles, the study further imposes constraints on the thrust efficiency and deflection efficiency of the thrust vectoring nozzle subsequent to a 15° deflection. Such measures ensure the maintenance of optimal stealth capabilities across all detection angles while preserving the unhampered thrust vectoring performance of the nozzle. This study employs the optimal Latin hypercube method and Kriging surrogate models in conjunction with collaborative optimization techniques to address multidisciplinary design optimization challenges. Comparative analyses with the initial design revealed significant enhancements: up to a 2.88% increase in the discharge coefficient, a maximum 0.53% increase in the thrust coefficient, and a notable reduction of up to 17.09% in tail direction dimensionless infrared radiation intensity, validating the effectiveness of the optimized exhaust system design.","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141714429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The gas wave rotor was usually designed and performed on the ideal gas model. However, the real gas effect could not be ignored anymore under high-pressure ratio conditions. In this study, for the first time, a two-dimensional computational model of a double-opening gas wave refrigerator (GWR) using a multi-parameter Benedict–Webb–Rubin equation of state is established and the influence of the real gas effect on gas wave dynamics and energy transfer processes in the GWR with discontinuous boundary conditions is thoroughly investigated. The numerical results show that the wave dynamics of the ideal gas and the real gas are similar under different operating conditions, but compression waves and expansion waves in real gas obviously lag behind the ideal gas. In addition, the low-temperature real gas is completely discharged earlier than the ideal gas and the difference between them gradually increases as the pressure ratio gets higher, which benefits the GWR compact structure design and cost reduction. At the same time, the temperature of the real gas being discharged is lower than that of the ideal gas. Therefore, the refrigeration efficiency of the isentropic expansion of the real gas will be improved compared with the operation in ideal gas. The research results on the real gas effect reveal the mechanism of wave dynamics and energy transfer, providing support for the optimization design of GWR.
{"title":"Effects of real gas models on the wave dynamics and refrigeration of gas wave rotor","authors":"Yihui Zhou, Feng Gao, Zhijun Liu, Dapeng Hu","doi":"10.1063/5.0215325","DOIUrl":"https://doi.org/10.1063/5.0215325","url":null,"abstract":"The gas wave rotor was usually designed and performed on the ideal gas model. However, the real gas effect could not be ignored anymore under high-pressure ratio conditions. In this study, for the first time, a two-dimensional computational model of a double-opening gas wave refrigerator (GWR) using a multi-parameter Benedict–Webb–Rubin equation of state is established and the influence of the real gas effect on gas wave dynamics and energy transfer processes in the GWR with discontinuous boundary conditions is thoroughly investigated. The numerical results show that the wave dynamics of the ideal gas and the real gas are similar under different operating conditions, but compression waves and expansion waves in real gas obviously lag behind the ideal gas. In addition, the low-temperature real gas is completely discharged earlier than the ideal gas and the difference between them gradually increases as the pressure ratio gets higher, which benefits the GWR compact structure design and cost reduction. At the same time, the temperature of the real gas being discharged is lower than that of the ideal gas. Therefore, the refrigeration efficiency of the isentropic expansion of the real gas will be improved compared with the operation in ideal gas. The research results on the real gas effect reveal the mechanism of wave dynamics and energy transfer, providing support for the optimization design of GWR.","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141704442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Erratum: “Up, down, and round again: The circulating flow dynamics of flux-driven fractures” [Phys. Fluids 36, 036622 (2024)]","authors":"C. M. Chalk, J. L. Kavanagh","doi":"10.1063/5.0218681","DOIUrl":"https://doi.org/10.1063/5.0218681","url":null,"abstract":"","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141693869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jotam Bergfreund, Ciatta Wobill, Frederic M. Evers, B. Hohermuth, Pascal Bertsch, Laurent Lebreton, Erich J Windhab, Peter Fischer
Anthropogenic plastic waste heavily pollutes global water systems. In particular, micron-sized plastic debris can have severe repercussions for the ocean flora and fauna. Microplastics may also affect physical processes such as wave breaking, which are critical for air–sea interaction and albedo. Nevertheless, the effects of micron-sized plastic debris on geophysical processes are widely unexplored. Herein, we investigate the effect of microplastic collected from the North Pacific and a surfactant mimicking surface active materials present in the ocean on the stability of foam generated by breaking wave experiments. We found that microplastic particles increase foam stability. In particular, an increased foam height was found in a column foaming setup, while an increased foam area was observed in a laboratory-scale breaking wave channel. We propose that microplastic particles assemble at the air–water interface of foam bubbles, form aggregates, presumably decrease the liquid drainage in the liquid film, and thus change the lifetime of the liquid film and the bubble. The effect of surfactants is generally larger due to their higher surface activity but still in a range where synergistic effects can be observed. Our results suggest that microplastic could influence oceanic processes essential for air–sea interaction, sea spray formation, and albedo.
{"title":"Impact of microplastic pollution on breaking waves","authors":"Jotam Bergfreund, Ciatta Wobill, Frederic M. Evers, B. Hohermuth, Pascal Bertsch, Laurent Lebreton, Erich J Windhab, Peter Fischer","doi":"10.1063/5.0208507","DOIUrl":"https://doi.org/10.1063/5.0208507","url":null,"abstract":"Anthropogenic plastic waste heavily pollutes global water systems. In particular, micron-sized plastic debris can have severe repercussions for the ocean flora and fauna. Microplastics may also affect physical processes such as wave breaking, which are critical for air–sea interaction and albedo. Nevertheless, the effects of micron-sized plastic debris on geophysical processes are widely unexplored. Herein, we investigate the effect of microplastic collected from the North Pacific and a surfactant mimicking surface active materials present in the ocean on the stability of foam generated by breaking wave experiments. We found that microplastic particles increase foam stability. In particular, an increased foam height was found in a column foaming setup, while an increased foam area was observed in a laboratory-scale breaking wave channel. We propose that microplastic particles assemble at the air–water interface of foam bubbles, form aggregates, presumably decrease the liquid drainage in the liquid film, and thus change the lifetime of the liquid film and the bubble. The effect of surfactants is generally larger due to their higher surface activity but still in a range where synergistic effects can be observed. Our results suggest that microplastic could influence oceanic processes essential for air–sea interaction, sea spray formation, and albedo.","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141710157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Lie invariance method is used to analyze the one-dimensional, unsteady flow of a cylindrical shock wave in a rotating, self-gravitating, radiating ideal gas under the influence of an axial or azimuthal magnetic field, with an emphasis on adiabatic conditions. The analysis assumes a stationary environment just ahead of the shock wave and considers variations in fluid velocity, magnetic field, and density within the perturbed medium just behind the shock front. In the governing equations, the impact of thermal radiation under an optically thin limit is integrated into the energy equation. Utilizing the Lie invariance method, the set of partial differential equations governing the flow in this medium is transformed into a system of nonlinear ordinary differential equations (ODEs) using similarity variables. Two distinct cases of similarity solutions are obtained by selecting different values for the arbitrary constants associated with the generators. Among these cases, one yields similarity solutions assuming a power-law shock path and the other an exponential-law shock path. For both cases, the resulting set of nonlinear ODEs are numerically solved using the 4th-order Runge–Kutta method in MATLAB software. The article thoroughly explores the influence of various parameters, including γ (adiabatic index of the gas), Ma−2 (Alfvén–Mach number), σ (ambient density exponent), l1 (rotational parameter), and G0 (gravitational parameter) on the flow properties. The findings are visually presented to offer a comprehensive insight into the effects of these parameters.
{"title":"Similarity solution for the magnetogasdynamic shock wave in a self-gravitating and rotating ideal gas under the influence of radiation heat flux","authors":"V. K. Vats, D. B. Singh, Mrigendra Manjul","doi":"10.1063/5.0214647","DOIUrl":"https://doi.org/10.1063/5.0214647","url":null,"abstract":"The Lie invariance method is used to analyze the one-dimensional, unsteady flow of a cylindrical shock wave in a rotating, self-gravitating, radiating ideal gas under the influence of an axial or azimuthal magnetic field, with an emphasis on adiabatic conditions. The analysis assumes a stationary environment just ahead of the shock wave and considers variations in fluid velocity, magnetic field, and density within the perturbed medium just behind the shock front. In the governing equations, the impact of thermal radiation under an optically thin limit is integrated into the energy equation. Utilizing the Lie invariance method, the set of partial differential equations governing the flow in this medium is transformed into a system of nonlinear ordinary differential equations (ODEs) using similarity variables. Two distinct cases of similarity solutions are obtained by selecting different values for the arbitrary constants associated with the generators. Among these cases, one yields similarity solutions assuming a power-law shock path and the other an exponential-law shock path. For both cases, the resulting set of nonlinear ODEs are numerically solved using the 4th-order Runge–Kutta method in MATLAB software. The article thoroughly explores the influence of various parameters, including γ (adiabatic index of the gas), Ma−2 (Alfvén–Mach number), σ (ambient density exponent), l1 (rotational parameter), and G0 (gravitational parameter) on the flow properties. The findings are visually presented to offer a comprehensive insight into the effects of these parameters.","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141716802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study delves into the utilization of jet fans in underground parking structures for smoke management during fires, with a specific focus on enhancing smoke control near critical areas adjacent to dead-end sections through innovative jet fan designs. Through the analysis of airflow patterns and computational fluid dynamic simulations, the research aims to effectively contain smoke and prevent its dispersion to unaffected zones. Findings underscore the significance of parking layout designs in ventilation strategies and soot dispersion rates. Altering the downward orientation of the jet fan outlet results in a notable portion of smoke being confined within the parking facility. Additionally, widening the jet fan outlet, as proposed in the design, can enhance smoke evacuation in all directions. Two hazard detection scenarios were executed within the parking structure following the British standard (BS), with one scenario simulated as a fire ignition source. The chosen scenario considers all escape routes and evacuation procedures within the underground parking area based on architectural specifications. By employing OpenFOAM software with the buoyantBoussinesqPimpleFOAM solver, the study assesses the efficacy of this approach, achieving a reduction in airflow irregularities of over 30%. It also provides valuable insights for designers to refine their comprehension of jet fan design, recommending tailored designs for specific zones. This research offers practical guidance for designers to optimize jet fan configurations for effective smoke control in underground parking facilities.
{"title":"Enhancing smoke management in underground parking areas using jet fan systems with a focus on dead-end areas","authors":"Saeed Hazrati Chakheirlou, Abdolnaser Omrani, Behnam Heydari Param, Roghayyeh Motallebzadeh","doi":"10.1063/5.0213475","DOIUrl":"https://doi.org/10.1063/5.0213475","url":null,"abstract":"This study delves into the utilization of jet fans in underground parking structures for smoke management during fires, with a specific focus on enhancing smoke control near critical areas adjacent to dead-end sections through innovative jet fan designs. Through the analysis of airflow patterns and computational fluid dynamic simulations, the research aims to effectively contain smoke and prevent its dispersion to unaffected zones. Findings underscore the significance of parking layout designs in ventilation strategies and soot dispersion rates. Altering the downward orientation of the jet fan outlet results in a notable portion of smoke being confined within the parking facility. Additionally, widening the jet fan outlet, as proposed in the design, can enhance smoke evacuation in all directions. Two hazard detection scenarios were executed within the parking structure following the British standard (BS), with one scenario simulated as a fire ignition source. The chosen scenario considers all escape routes and evacuation procedures within the underground parking area based on architectural specifications. By employing OpenFOAM software with the buoyantBoussinesqPimpleFOAM solver, the study assesses the efficacy of this approach, achieving a reduction in airflow irregularities of over 30%. It also provides valuable insights for designers to refine their comprehension of jet fan design, recommending tailored designs for specific zones. This research offers practical guidance for designers to optimize jet fan configurations for effective smoke control in underground parking facilities.","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141694129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ammonia has been identified as a promising fuel to diminish greenhouse gas emission. However, ammonia combustion presents certain challenges including low reactivity and high NO emission. In the present study, three-dimensional direct numerical simulations (DNS) of ammonia/air premixed slot jet flames with varying Karlovitz numbers (Ka) and cracking ratios were performed. Three cases were considered, including two pure ammonia/air flames with different turbulence intensities and one partially cracked ammonia/air flame with high turbulence intensity. The effects of turbulence intensity and partial ammonia cracking on turbulence–flame interactions and NO emission characteristics of the flames were investigated. It was shown that the turbulent flame speed is higher for the flames with high turbulence intensity. In general, the flame displacement speed is negatively correlated with curvature in negative curvature regions, while the correlation is weak in the positive curvature regions for highly turbulent flames. Most flame area is consumed in negatively curved regions and produced in positively curved regions. It was found that the NO mass fraction is higher in the flame with partial ammonia cracking compared to the pure ammonia/air flames. The NO pathway analysis shows that the NH → NO pathway is enhanced, while the NO consumption pathway is suppressed in the partially cracked ammonia/air flame. The NO mass fraction is higher in regions of negative curvature than positive curvature. Interestingly, the NO mass fraction is found to be negatively correlated with the local equivalence ratio, which is consistent in both the DNS and the corresponding laminar premixed flames.
氨被认为是一种有希望减少温室气体排放的燃料。然而，氨燃烧面临着某些挑战，包括低反应性和高氮氧化物排放。本研究对不同卡尔洛维茨数（Ka）和裂解率的氨/空气预混合槽形喷射火焰进行了三维直接数值模拟（DNS）。共考虑了三种情况，包括两种不同湍流强度的纯氨/空气火焰和一种高湍流强度的部分裂解氨/空气火焰。研究了湍流强度和部分氨裂解对湍流-火焰相互作用和火焰氮氧化物排放特性的影响。结果表明，湍流强度高的火焰湍流速度更高。一般来说，在负曲率区域，火焰位移速度与曲率呈负相关，而在高湍流火焰的正曲率区域，相关性较弱。大部分火焰面积在负曲率区域被消耗，而在正曲率区域产生。研究发现，与纯氨/空气火焰相比，部分氨裂解火焰中的 NO 质量分数更高。NO 途径分析表明，在部分裂解的氨/空气火焰中，NH → NO 途径增强，而 NO 消耗途径受到抑制。负曲率区域的 NO 质量分数高于正曲率区域。有趣的是，NO 质量分数与局部等效比呈负相关，这在 DNS 和相应的层流预混火焰中都是一致的。
{"title":"Direct numerical simulations of pure and partially cracked ammonia/air turbulent premixed jet flames","authors":"Tingquan Tian, Haiou Wang, K. Luo, Jianren Fan","doi":"10.1063/5.0215258","DOIUrl":"https://doi.org/10.1063/5.0215258","url":null,"abstract":"Ammonia has been identified as a promising fuel to diminish greenhouse gas emission. However, ammonia combustion presents certain challenges including low reactivity and high NO emission. In the present study, three-dimensional direct numerical simulations (DNS) of ammonia/air premixed slot jet flames with varying Karlovitz numbers (Ka) and cracking ratios were performed. Three cases were considered, including two pure ammonia/air flames with different turbulence intensities and one partially cracked ammonia/air flame with high turbulence intensity. The effects of turbulence intensity and partial ammonia cracking on turbulence–flame interactions and NO emission characteristics of the flames were investigated. It was shown that the turbulent flame speed is higher for the flames with high turbulence intensity. In general, the flame displacement speed is negatively correlated with curvature in negative curvature regions, while the correlation is weak in the positive curvature regions for highly turbulent flames. Most flame area is consumed in negatively curved regions and produced in positively curved regions. It was found that the NO mass fraction is higher in the flame with partial ammonia cracking compared to the pure ammonia/air flames. The NO pathway analysis shows that the NH → NO pathway is enhanced, while the NO consumption pathway is suppressed in the partially cracked ammonia/air flame. The NO mass fraction is higher in regions of negative curvature than positive curvature. Interestingly, the NO mass fraction is found to be negatively correlated with the local equivalence ratio, which is consistent in both the DNS and the corresponding laminar premixed flames.","PeriodicalId":509470,"journal":{"name":"Physics of Fluids","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141691319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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