Pub Date : 2023-07-04DOI: 10.1080/00221686.2023.2232763
Muhammed Hashid, T. Eldho
This paper presents an experimental study focusing on the effect of intake pipe blockage on the critical submergence of lateral dual square intakes under perpendicular uniform approach flow. The pipe blockage is implemented by various intake protrusions into the approach flow, with one of the intakes always kept flush with the channel sidewall. An increase in protrusion of downstream intake alone causes a significant decrease in critical submergence, and an increased protrusion of upstream intake alone causes higher critical submergence when both intakes operate under identical conditions. At higher protrusions of twice the intake size, the mutual influence between the intakes was negligible with multiple vortex formations at both intakes in dual configuration. Based on the results, an empirical equation is proposed for the computation of critical submergence for lateral dual protruded intakes and was found to be in good agreement with the experimental results, which will be useful in the design for fixing the invert level of dual intakes under approach flow condition. The flow blockage due to protrusion can be adopted effectively to reduce the critical submergence for multiple intake structures.
{"title":"Effect of intake pipe blockage on the critical submergence for lateral dual intakes","authors":"Muhammed Hashid, T. Eldho","doi":"10.1080/00221686.2023.2232763","DOIUrl":"https://doi.org/10.1080/00221686.2023.2232763","url":null,"abstract":"This paper presents an experimental study focusing on the effect of intake pipe blockage on the critical submergence of lateral dual square intakes under perpendicular uniform approach flow. The pipe blockage is implemented by various intake protrusions into the approach flow, with one of the intakes always kept flush with the channel sidewall. An increase in protrusion of downstream intake alone causes a significant decrease in critical submergence, and an increased protrusion of upstream intake alone causes higher critical submergence when both intakes operate under identical conditions. At higher protrusions of twice the intake size, the mutual influence between the intakes was negligible with multiple vortex formations at both intakes in dual configuration. Based on the results, an empirical equation is proposed for the computation of critical submergence for lateral dual protruded intakes and was found to be in good agreement with the experimental results, which will be useful in the design for fixing the invert level of dual intakes under approach flow condition. The flow blockage due to protrusion can be adopted effectively to reduce the critical submergence for multiple intake structures.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45637723","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}
Pub Date : 2023-07-04DOI: 10.1080/00221686.2023.2224276
Slaven Conevski, M. Guerrero, A. Winterscheid, Doreen Faltis, C. Rennie, Nils Ruther
Acoustic Doppler current profilers (ADCP) were deployed to investigate the backscattering (BS) signal in three navigable rivers, in different bedload transport conditions. This study aims to demonstrate that the BS strength, as an additional variable to the apparent bedload velocity, improves the characterization of the bedload transport using ADCPs. The M9 –3 MHz and the vertical beam M9 – 0.5 MHz showed decline of the BS strength as the bedload intensity increased, whereas the RDI –1.2 MHz was relatively insensitive. The correlation between the median grain size and the BS strength for the 0.5 MHz was linear, for the 3 MHz the BS strength was attenuated in the active layer, and for 1.2 MHz, it revealed a parabolic distribution. Moreover, the analyses of the ADCP measured variables, using wavelet transformations and unsupervised machine learning, highlighted the importance of the spatial and temporal variance and transient nature of the bedload transport.
{"title":"Analysis of the riverbed backscattered signal registered by ADCPs in different bedload transport conditions – field application","authors":"Slaven Conevski, M. Guerrero, A. Winterscheid, Doreen Faltis, C. Rennie, Nils Ruther","doi":"10.1080/00221686.2023.2224276","DOIUrl":"https://doi.org/10.1080/00221686.2023.2224276","url":null,"abstract":"Acoustic Doppler current profilers (ADCP) were deployed to investigate the backscattering (BS) signal in three navigable rivers, in different bedload transport conditions. This study aims to demonstrate that the BS strength, as an additional variable to the apparent bedload velocity, improves the characterization of the bedload transport using ADCPs. The M9 –3 MHz and the vertical beam M9 – 0.5 MHz showed decline of the BS strength as the bedload intensity increased, whereas the RDI –1.2 MHz was relatively insensitive. The correlation between the median grain size and the BS strength for the 0.5 MHz was linear, for the 3 MHz the BS strength was attenuated in the active layer, and for 1.2 MHz, it revealed a parabolic distribution. Moreover, the analyses of the ADCP measured variables, using wavelet transformations and unsupervised machine learning, highlighted the importance of the spatial and temporal variance and transient nature of the bedload transport.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46408915","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}
Pub Date : 2023-07-04DOI: 10.1080/00221686.2023.2235811
G. Müller
Waves are an integral component of teaching in coastal engineering. Some aspects of wave theory are however complex and outside the scope of e.g. introductory courses, so that only the results of the theory are used. For other wave effects such as overtopping, no theory exists, and purely empirical formulas are employed. This limits the students’ understanding of the problems. At Southampton University, we developed simple models for wave effects to improve the teaching. The models rely on basic hydraulic engineering principles such as continuity, conservation of energy and momentum, with the condition that the results are reasonably close to those from more complex theories or from experiments. In this article, two such models for the propagation speed of a solitary wave, and for the shallow water breaking criterion, will be presented. The results from both models are surprisingly close to the textbook formulas or values.
{"title":"Two simple theoretical models for teaching wave mechanics in coastal engineering","authors":"G. Müller","doi":"10.1080/00221686.2023.2235811","DOIUrl":"https://doi.org/10.1080/00221686.2023.2235811","url":null,"abstract":"Waves are an integral component of teaching in coastal engineering. Some aspects of wave theory are however complex and outside the scope of e.g. introductory courses, so that only the results of the theory are used. For other wave effects such as overtopping, no theory exists, and purely empirical formulas are employed. This limits the students’ understanding of the problems. At Southampton University, we developed simple models for wave effects to improve the teaching. The models rely on basic hydraulic engineering principles such as continuity, conservation of energy and momentum, with the condition that the results are reasonably close to those from more complex theories or from experiments. In this article, two such models for the propagation speed of a solitary wave, and for the shallow water breaking criterion, will be presented. The results from both models are surprisingly close to the textbook formulas or values.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48175272","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}
Pub Date : 2023-07-04DOI: 10.1080/00221686.2023.2225462
Daniele Catucci, R. Briganti, V. Heller
Air–water flows are among the most important flow types in hydraulic engineering. Their experimental modelling at reduced size using Froude scaling laws introduces scale effects. This study introduces novel scaling laws for compressible air–water flows in which the air is considered compressible. This is achieved by applying the one-parameter Lie group of point-scaling transformations to the governing equations of these flows. The scaling relationships between variables are derived for the fluid properties and the flow variables including temperature. The novel scaling laws are validated by computational fluid dynamics modelling of a Taylor bubble at different scales. The resulting velocity, density, temperature, pressure and volume of the bubble are shown to be self-similar at different scales, i.e. all these variables behave the same in dimensionless form. This study shows that the self-similar conditions of the derived novel scaling laws for compressible air–water flows have the potential to improve laboratory modelling.
{"title":"Numerical validation of novel scaling laws for air–water flows including compressibility and heat transfer","authors":"Daniele Catucci, R. Briganti, V. Heller","doi":"10.1080/00221686.2023.2225462","DOIUrl":"https://doi.org/10.1080/00221686.2023.2225462","url":null,"abstract":"Air–water flows are among the most important flow types in hydraulic engineering. Their experimental modelling at reduced size using Froude scaling laws introduces scale effects. This study introduces novel scaling laws for compressible air–water flows in which the air is considered compressible. This is achieved by applying the one-parameter Lie group of point-scaling transformations to the governing equations of these flows. The scaling relationships between variables are derived for the fluid properties and the flow variables including temperature. The novel scaling laws are validated by computational fluid dynamics modelling of a Taylor bubble at different scales. The resulting velocity, density, temperature, pressure and volume of the bubble are shown to be self-similar at different scales, i.e. all these variables behave the same in dimensionless form. This study shows that the self-similar conditions of the derived novel scaling laws for compressible air–water flows have the potential to improve laboratory modelling.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46647537","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}
Pub Date : 2023-07-04DOI: 10.1080/00221686.2023.2231420
Yifei Huang, G. Guan, Kang Wang, Zhonghao Mao, Zhonghua Yang
In recent years, China has been building several inter-basin water conveyance projects across mountains and deep valleys, leading to the extensive use of long tunnels and inverted siphons. The dynamics of mixed free-surface-pressurized flows are critical for tunnel design and operational safety. However, traditional numerical computation schemes cannot precisely and efficiently capture the pressure interface because the tunnel may be more than 70 km long. This study aims to develop a hybrid scheme that is as fast as the large-time-step Preissmann four-point scheme (FDM) and has the approximate interface accuracy of the finite volume method (FVM) by dynamic grid meshing. A dynamic mesh domain model (DM) is proposed by adopting an FVM mesh with a small time step to dynamically capture the interface and applying an FDM mesh with a large time step to improve computational efficiency. The results show that the method can simulate flow patterns, such as transcritical and pressurized flows, by ignoring the acceleration convection terms and capturing mixed free-surface-pressurized flows conveniently, accurately and efficiently. Furthermore, it can accelerate the computational speed of the transient mixed flow by a factor of approximately 100 when the target tunnel length exceeds 1200 m. The proposed scheme cannot capture the water hammer pressure because of the large time step. However, it can be effectively utilized in large cascade water delivery systems where the flow changes gradually.
{"title":"Hybridizing FDM and FVM scheme of high-precision interface fast capture for mixed free-surface-pressurized flow in large cascade water delivery system","authors":"Yifei Huang, G. Guan, Kang Wang, Zhonghao Mao, Zhonghua Yang","doi":"10.1080/00221686.2023.2231420","DOIUrl":"https://doi.org/10.1080/00221686.2023.2231420","url":null,"abstract":"In recent years, China has been building several inter-basin water conveyance projects across mountains and deep valleys, leading to the extensive use of long tunnels and inverted siphons. The dynamics of mixed free-surface-pressurized flows are critical for tunnel design and operational safety. However, traditional numerical computation schemes cannot precisely and efficiently capture the pressure interface because the tunnel may be more than 70 km long. This study aims to develop a hybrid scheme that is as fast as the large-time-step Preissmann four-point scheme (FDM) and has the approximate interface accuracy of the finite volume method (FVM) by dynamic grid meshing. A dynamic mesh domain model (DM) is proposed by adopting an FVM mesh with a small time step to dynamically capture the interface and applying an FDM mesh with a large time step to improve computational efficiency. The results show that the method can simulate flow patterns, such as transcritical and pressurized flows, by ignoring the acceleration convection terms and capturing mixed free-surface-pressurized flows conveniently, accurately and efficiently. Furthermore, it can accelerate the computational speed of the transient mixed flow by a factor of approximately 100 when the target tunnel length exceeds 1200 m. The proposed scheme cannot capture the water hammer pressure because of the large time step. However, it can be effectively utilized in large cascade water delivery systems where the flow changes gradually.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46091619","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}
Pub Date : 2023-07-04DOI: 10.1080/00221686.2023.2227442
Jian Zhang, Long Chen, Yongguang Cheng, Hui-yong Xu, Xu-yun Chen, Dongliang Hu
Hydraulic oscillation is a fluctuating phenomenon of pressure and discharge in pipes, which can threaten the safety of hydropower, pumping and water conveyance systems. To analyse the associated problems, new methods with simple form and clear physics are needed. This paper presents a water-hammer reflection coefficient-based criterion for stability evaluation of free-vibration of hydraulic systems. The stability (or attenuation) condition for a single pipe system is that the modulus of the product of the reflection coefficients at the inlet and outlet should be smaller than 1. For a complex pipe system, the condition necessary for stability is that every single pipe system is stable. To apply this new criterion to stabilizing the reservoir-single pipe-constant power turbine system by adding a head loss valve in the pipe, a formula for the critical head loss is proposed and verified. This new method is theoretically consistent with conventional methods, but more convenient in application.
{"title":"Simple criterion for evaluating stability of hydraulic oscillation based on water-hammer reflection coefficients","authors":"Jian Zhang, Long Chen, Yongguang Cheng, Hui-yong Xu, Xu-yun Chen, Dongliang Hu","doi":"10.1080/00221686.2023.2227442","DOIUrl":"https://doi.org/10.1080/00221686.2023.2227442","url":null,"abstract":"Hydraulic oscillation is a fluctuating phenomenon of pressure and discharge in pipes, which can threaten the safety of hydropower, pumping and water conveyance systems. To analyse the associated problems, new methods with simple form and clear physics are needed. This paper presents a water-hammer reflection coefficient-based criterion for stability evaluation of free-vibration of hydraulic systems. The stability (or attenuation) condition for a single pipe system is that the modulus of the product of the reflection coefficients at the inlet and outlet should be smaller than 1. For a complex pipe system, the condition necessary for stability is that every single pipe system is stable. To apply this new criterion to stabilizing the reservoir-single pipe-constant power turbine system by adding a head loss valve in the pipe, a formula for the critical head loss is proposed and verified. This new method is theoretically consistent with conventional methods, but more convenient in application.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46850572","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}
Pub Date : 2023-07-04DOI: 10.1080/00221686.2023.2222095
Zheng-hui Cui, Lei Huang, H. Fang, F. Bombardelli, Dianchang Wang, Xinghua Wu
Interactions among natural fine sediment particles are essential to the flocculation process, and are affected significantly by surface heterogeneity. In this study, a series of mathematical sediments are generated to characterize the natural particles with different sizes and surface heterogeneities of micro-morphology and charge distribution. The total particles interactions are calculated with Derjaguin–Landau–Verwey–Overbeek (DLVO) theory to theoretically estimate the attachment efficiency (α), where the irreversible and reversible attachment are distinguished. The results show that approaching particles are easier to attached to after collision with increasing particle size (with a fixed size ratio between particles) or increasing similarity in size of both particles. Meanwhile, the electrostatic interactions increase significantly with the presence and enlargement of surface heterogeneities, especially at large separations, which reduces the more approachable reversible attachment, and thus mitigates the flocculation in aquatic systems. This study gives an insight into the mechanism of attachment among sediment considering surface heterogeneities, and provides a quantitative estimation of attachment efficiency which is adaptable for sediment flocculation modelling.
{"title":"Attachment efficiency among fine sediment considering surface heterogeneity","authors":"Zheng-hui Cui, Lei Huang, H. Fang, F. Bombardelli, Dianchang Wang, Xinghua Wu","doi":"10.1080/00221686.2023.2222095","DOIUrl":"https://doi.org/10.1080/00221686.2023.2222095","url":null,"abstract":"Interactions among natural fine sediment particles are essential to the flocculation process, and are affected significantly by surface heterogeneity. In this study, a series of mathematical sediments are generated to characterize the natural particles with different sizes and surface heterogeneities of micro-morphology and charge distribution. The total particles interactions are calculated with Derjaguin–Landau–Verwey–Overbeek (DLVO) theory to theoretically estimate the attachment efficiency (α), where the irreversible and reversible attachment are distinguished. The results show that approaching particles are easier to attached to after collision with increasing particle size (with a fixed size ratio between particles) or increasing similarity in size of both particles. Meanwhile, the electrostatic interactions increase significantly with the presence and enlargement of surface heterogeneities, especially at large separations, which reduces the more approachable reversible attachment, and thus mitigates the flocculation in aquatic systems. This study gives an insight into the mechanism of attachment among sediment considering surface heterogeneities, and provides a quantitative estimation of attachment efficiency which is adaptable for sediment flocculation modelling.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48436498","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}
Pub Date : 2023-07-04DOI: 10.1080/00221686.2023.2222313
L. Pitorac, K. Vereide, B. Svingen, L. Lia
The need for more energy storage in the transition to a renewable energy system leads to increasing interest in upgrading existing hydropower plants to pumped storage plants. Such upgrades result in stronger hydraulic transients in the tunnel system, including increased mass oscillation amplitudes. In this study, a generalized tunnel system with multiple brook intakes/surge tanks is analysed to assess the influence of the brook intakes on the mass oscillation stability. The variables that are assessed are the number of brook intakes, cross section area, the amount of inflow, and throttling of the brook intakes/surge tanks. The study is carried out using frequency-response analysis, where the excitation is the oscillation of the guide vane position, and the response is the product of the measured head and discharge (equivalent to the hydraulic power). The results show that brook intakes are generally beneficial for the stability of the mass oscillations. Existing hydropower plants with brook intakes may have sufficient stability margins to allow upgrade and reconstruction without the need for upgrading of the surge tank with regard to mass oscillation stability.
{"title":"Stability of mass oscillations in hydropower plants with brook intakes","authors":"L. Pitorac, K. Vereide, B. Svingen, L. Lia","doi":"10.1080/00221686.2023.2222313","DOIUrl":"https://doi.org/10.1080/00221686.2023.2222313","url":null,"abstract":"The need for more energy storage in the transition to a renewable energy system leads to increasing interest in upgrading existing hydropower plants to pumped storage plants. Such upgrades result in stronger hydraulic transients in the tunnel system, including increased mass oscillation amplitudes. In this study, a generalized tunnel system with multiple brook intakes/surge tanks is analysed to assess the influence of the brook intakes on the mass oscillation stability. The variables that are assessed are the number of brook intakes, cross section area, the amount of inflow, and throttling of the brook intakes/surge tanks. The study is carried out using frequency-response analysis, where the excitation is the oscillation of the guide vane position, and the response is the product of the measured head and discharge (equivalent to the hydraulic power). The results show that brook intakes are generally beneficial for the stability of the mass oscillations. Existing hydropower plants with brook intakes may have sufficient stability margins to allow upgrade and reconstruction without the need for upgrading of the surge tank with regard to mass oscillation stability.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43696354","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}
Transient flows with water-flow-induced multi-point cavitation inside an undulating pipeline are investigated experimentally under conditions of fast valve closure for three typical test cases by using high-precision pressure transducers, high-speed photography and particle image velocimetry (PIV) techniques. For low initial velocity condition, the transient pressure at the monitoring point (PT1) downstream the valve quickly decreases to the cavitation pressure and fluctuates near it. The leading-edge velocity of the dispersed bubble-like cavitation group first increases with its occurrence and then accelerates and reaches an extreme value before decreasing to zero due to the viscous force and the decrease of water flow inertia, and finally the water flows upstream in reverse, i.e. the leading-edge accelerates and collapses behind the valve. At the same time, the transient pressure rises sharply to maximum 81.86 m due to the return of the compression wave and then decreases sharply to cavitation again because of the switch of the pressure waves. Then, the second cavitation intensity is weak and the corresponding pattern is fog-like, and finally decreases gradually with a cyclic period of about 0.38 s. The transient pressure at the monitoring point (PT2) at the peak of the undulating pipeline also maintains at the cavitation pressure corresponding to the big bubble occurrence moment in addition to its fluctuation near the cavitation pressure including first and second cavitation. Its maximum pressure is 72.16 m and the corresponding cavitation pattern is small and bigger bubbles at different cavitation stages. For middle initial velocity, the typical pattern of the corresponding cavitation is the large cavity with free surface at PT2, the corresponding higher maximum pressures are 102.36 m at PT1 and 84.81 m at PT2. The evolution process of the cavity including bubble mergence, morphological deformation, motion and collapse is analysed based on the broken wave and hydraulic dynamic theories. For high initial velocity, larger cavities occur both downstream the valve and at the peak point of undulating pipeline, and thus the corresponding higher maximum pressures due to larger cavity collapse are 140.56 m at PT1 and 127.98 m at PT2. In particular, complete water column separation with transparent large cavity occur downstream the valve.
{"title":"Cavitation evolution and flow field characteristics of transient flows with multi-point water-column separations in undulating pipeline","authors":"Guohong Wu, Xuelin Tang, Xiaoqin Li, Q. Zhong, Jian-qun Zhu, Xiao-yan Shi","doi":"10.1080/00221686.2023.2224275","DOIUrl":"https://doi.org/10.1080/00221686.2023.2224275","url":null,"abstract":"Transient flows with water-flow-induced multi-point cavitation inside an undulating pipeline are investigated experimentally under conditions of fast valve closure for three typical test cases by using high-precision pressure transducers, high-speed photography and particle image velocimetry (PIV) techniques. For low initial velocity condition, the transient pressure at the monitoring point (PT1) downstream the valve quickly decreases to the cavitation pressure and fluctuates near it. The leading-edge velocity of the dispersed bubble-like cavitation group first increases with its occurrence and then accelerates and reaches an extreme value before decreasing to zero due to the viscous force and the decrease of water flow inertia, and finally the water flows upstream in reverse, i.e. the leading-edge accelerates and collapses behind the valve. At the same time, the transient pressure rises sharply to maximum 81.86 m due to the return of the compression wave and then decreases sharply to cavitation again because of the switch of the pressure waves. Then, the second cavitation intensity is weak and the corresponding pattern is fog-like, and finally decreases gradually with a cyclic period of about 0.38 s. The transient pressure at the monitoring point (PT2) at the peak of the undulating pipeline also maintains at the cavitation pressure corresponding to the big bubble occurrence moment in addition to its fluctuation near the cavitation pressure including first and second cavitation. Its maximum pressure is 72.16 m and the corresponding cavitation pattern is small and bigger bubbles at different cavitation stages. For middle initial velocity, the typical pattern of the corresponding cavitation is the large cavity with free surface at PT2, the corresponding higher maximum pressures are 102.36 m at PT1 and 84.81 m at PT2. The evolution process of the cavity including bubble mergence, morphological deformation, motion and collapse is analysed based on the broken wave and hydraulic dynamic theories. For high initial velocity, larger cavities occur both downstream the valve and at the peak point of undulating pipeline, and thus the corresponding higher maximum pressures due to larger cavity collapse are 140.56 m at PT1 and 127.98 m at PT2. In particular, complete water column separation with transparent large cavity occur downstream the valve.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46717070","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}
Pub Date : 2023-07-04DOI: 10.1080/00221686.2023.2231413
Saiyu Yuan, Guanghui Yan, Hongwu Tang, Yang Xiao, H. Rahimi, Moe Nandar Aye, C. Gualtieri
Confluences are common components of river networks and are characterized by a highly complex flow structure. Two confluence geometries, without and with the floodplain in the tributary, were comparatively investigated to highlight the effects of floodplain on confluence hydrodynamics. The three-dimensional velocity field and the spatial distribution of turbulent kinetic energy and Reynolds shear stresses were analysed. In the second geometry, a tilted shear layer was observed, which was related to the flow expansion from the main channel into the tributary. Significant secondary motions are mainly related to the fluid upwelling in the lee of the floodplain step and streamline curvature. A wider flow separation zone was found, while the length of the separation zone was not affected by the floodplain flow. The results could be useful to understand the complex hydrodynamics of the large confluence between the Yangtze River and the Poyang Lake, characterized from a floodplain under high flow conditions.
{"title":"Effects of tributary floodplain on confluence hydrodynamics","authors":"Saiyu Yuan, Guanghui Yan, Hongwu Tang, Yang Xiao, H. Rahimi, Moe Nandar Aye, C. Gualtieri","doi":"10.1080/00221686.2023.2231413","DOIUrl":"https://doi.org/10.1080/00221686.2023.2231413","url":null,"abstract":"Confluences are common components of river networks and are characterized by a highly complex flow structure. Two confluence geometries, without and with the floodplain in the tributary, were comparatively investigated to highlight the effects of floodplain on confluence hydrodynamics. The three-dimensional velocity field and the spatial distribution of turbulent kinetic energy and Reynolds shear stresses were analysed. In the second geometry, a tilted shear layer was observed, which was related to the flow expansion from the main channel into the tributary. Significant secondary motions are mainly related to the fluid upwelling in the lee of the floodplain step and streamline curvature. A wider flow separation zone was found, while the length of the separation zone was not affected by the floodplain flow. The results could be useful to understand the complex hydrodynamics of the large confluence between the Yangtze River and the Poyang Lake, characterized from a floodplain under high flow conditions.","PeriodicalId":54802,"journal":{"name":"Journal of Hydraulic Research","volume":null,"pages":null},"PeriodicalIF":2.3,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44020733","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}
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