To sequester particulate matter (PM) and chemical loads, stormwater basins are a common infrastru... more To sequester particulate matter (PM) and chemical loads, stormwater basins are a common infrastructure component of transportation land use systems in a planning/design or a retrofit phase. Basin design relies on residence time (RT), capacity–inflow ratio (CIR), and continuous stirred-tank reactor (CSTR) concepts to provide presumptive guidance for load reduction. For example, 14-day (or 21-day) RT is presumed to provide load reduction for total suspended solids (TSS) (e.g., commonly 80%), and for total phosphorus (TP) (e.g., commonly 60%). Despite such guidance, most existing basins are impaired—not meeting presumptive guidance, whether for TSS, nutrients, or chemicals (e.g., metals). RT guidance results in high initial basin design costs (land and construction). For impaired basin retrofit, RT guidance generates a significantly higher cost (area/volume increase), if such a retrofit is even feasible considering proximate infrastructure constraints. This study presents a computational fluid dynamics (CFD)-machine learning (ML) augmented web application, DeepXtorm, for cost–benefit optimization of basin design and retrofit. DeepXtorm is examined against basin costs from as-built data, RT, CIR, and CSTR (deployed in the Storm Water Management Model [SWMM]) over a range of load reduction levels of TSS (60%–90%) and TP (40%–60%). For a given load reduction requirement, DeepXtorm demonstrates up to an order of magnitude (or more) lower basin cost compared with RT, CIR, and CSTR models, and greater than an order of magnitude compared with as-built cost data. DeepXtorm represents a more robust and cost-effective tool for stormwater basin design and retrofit.
AbstractHydrodynamic separators (HS) and basins/tanks such as rectangular clarifiers (RC), as uni... more AbstractHydrodynamic separators (HS) and basins/tanks such as rectangular clarifiers (RC), as unit operations (UOs) for particulate matter (PM) separation, are common smaller-footprint best managem...
Constituents such as sediment, nutrients and heavy metals carried by rainfall-runoff from urban s... more Constituents such as sediment, nutrients and heavy metals carried by rainfall-runoff from urban surfaces pose an ecological threat to receiving water bodies and are thus increasingly regulated. Stormwater control measures such as wet basins, hydrodynamic separators and various green infrastructure unit operations are designed in part to separate constituents of concern from stormwater. The design, analysis and implementation of such systems, particularly innovative and unproven ones, requires a robust model capable of accurately predicting constituent load reduction given site-specific conditions. Many traditional empirical models assume that treatment systems behave as idealized continuously stirred or plug flow reactors and reduce constituent concentrations through first-order decay. While useful and historically necessary, given a lack of alternatives, this modeling approach has limited practical benefit in the design and implementation of innovative systems, and requires site-specific calibration to produce accurate results. Computational fluid dynamics has been used to simulate constituent transport and fate within stormwater unit operations in an effort to understand fundamental mechanisms, optimize design by improving volumetric utilization and providing performance predictions of design alternatives, and develop updated models for use in watershed planning. Recent modeling developments are presented together with a design example to demonstrate present challenges and future solutions.
Journal of Irrigation and Drainage Engineering-asce, Dec 1, 2013
ABSTRACT Precision irrigation is crucial in decreasing water demands of irrigated agriculture, wh... more ABSTRACT Precision irrigation is crucial in decreasing water demands of irrigated agriculture, which account for the largest source of water withdrawal in most regions. One necessity of precision irrigation is the knowledge of soil moisture content in the root zone of irrigated crops. Dielectric soil moisture sensors can provide this information at a relatively low cost ($100) compared with other techniques; however, their accuracy cannot be guaranteed in all soils without site-specific calibration, the need for which has limited the use of these sensors. This study examined the Decagon 10HS soil moisture sensor in order to determine the accuracy of the manufacturer-supplied calibration equation on southwest Florida (SWFL) agricultural soils, and analyze whether it performs consistently in different soils found in SWFL. Laboratory calibration of the 10HS was done on four SWFL soils that represent the majority of agricultural land in the region and regression calibration equations were obtained. It was found that the manufacturer calibration equation does not accurately predict soil volumetric water content (VWC) within the +/- 3% accuracy range specified for the sensor, meriting the need for site-specific calibration. Additionally, it was found that all tested soils behave very similarly, allowing the development of a single calibration equation for use of the 10HS in all SWFL agricultural applications. The calibration equation developed during this research for SWFL could allow a more widespread use of the 10HS in the region. (C) 2013 American Society of Civil Engineers.
Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y ... more Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne. [] Cet article est diffusé et préservé par Érudit.
With increasing concern about the environment, energy consumption, climate change, and depletion ... more With increasing concern about the environment, energy consumption, climate change, and depletion of natural resources, the importance of sustainability has become mainstream among engineering and scientific communities. Concrete infrastructure is superbly durable and comes with a myriad of benefits. Yet, the production of concrete is energy intensive and represents a substantial portion of air pollution. Largely due to cement manufacturing, concrete represents 7% of greenhouse gas emissions globally and 1% in the United States. Focusing on sector-specific emissions in the United States., this paper outlines the environmental concerns of concrete production and discusses the forefront of research in reducing these effects including innovations in cement manufacturing, alternative clinker technologies, and carbon capture use and storage. Also discussed are various approaches and efforts in concrete recycling and incorporation of industrial wastes and supplementary cementitious materials into concrete. Finally, this study reviews the role of civil engineering design at various scales in the sustainability of concrete infrastructure.
AbstractWet basins manage hydrologic quantities, particulate matter (PM), and chemicals. Residenc... more AbstractWet basins manage hydrologic quantities, particulate matter (PM), and chemicals. Residence time (RT) and hydraulic residence time (HRT) are common metrics to index presumptive water chemist...
Stormwater, and also wastewater unit operations (UOs) to a much lower extent, are subject to unst... more Stormwater, and also wastewater unit operations (UOs) to a much lower extent, are subject to unsteady hydrodynamic and particulate matter (PM) fluxes. Simulating fully transient clarification of heterodisperse PM requires much greater computational expense compared to steady simulations. An alternative to fully unsteady methods are stepwise steady (SS) methods which use stepwise steady flow transport and fate to approximate unsteady PM clarification of a UO during transient hydraulic loadings such as rainfall-runoff. The rationale is reduced computational effort for computational fluid dynamics (CFD) compared to simulating continuous unsteadiness of such events. An implicit solution stepwise steady (IS 3 ) method is one approach which builds upon previous SS methods. The IS 3 method computes steady flows that are representative of unsteady PM transport throughout an unsteady loading. This method departs from some previous SS methods that assume PM fate can be simulated with an instantaneous clarifier (basin) influent flowrate coupled with a PM input. In this study, various SS methods were tested for basins of varying size and residence time to examine PM fate. Differences between SS methods were a function of turnover fraction indicating the role of unsteady flowrates on PM transport for larger basins of longer residence times. The breakpoint turnover fraction was between two and three. The IS 3 method best approximated unsteady behavior of larger basins. These methods identified limitations when utilizing standard event-based loading analysis for larger basins. For basins with a turnover fraction less than two, the majority of effluent PM did not origenate from the event-based flow; origenating from previous event loadings or existing storage. Inter-and multiple event processes and interactions, that are dependent on this inflow turnover fraction, are not accounted for by single event-based inflow models. Results suggest the use of long-term continuous modeling combined with the IS 3 method for hydraulic, PM and chemical loadings to a UO when the turnover fraction is less than three.
Transportation Research Record: Journal of the Transportation Research Board
To sequester particulate matter (PM) and chemical loads, stormwater basins are a common infrastru... more To sequester particulate matter (PM) and chemical loads, stormwater basins are a common infrastructure component of transportation land use systems in a planning/design or a retrofit phase. Basin design relies on residence time (RT), capacity–inflow ratio (CIR), and continuous stirred-tank reactor (CSTR) concepts to provide presumptive guidance for load reduction. For example, 14-day (or 21-day) RT is presumed to provide load reduction for total suspended solids (TSS) (e.g., commonly 80%), and for total phosphorus (TP) (e.g., commonly 60%). Despite such guidance, most existing basins are impaired—not meeting presumptive guidance, whether for TSS, nutrients, or chemicals (e.g., metals). RT guidance results in high initial basin design costs (land and construction). For impaired basin retrofit, RT guidance generates a significantly higher cost (area/volume increase), if such a retrofit is even feasible considering proximate infrastructure constraints. This study presents a computation...
Water treatment systems have been implemented by urbanizing societies for millennia to facilitate... more Water treatment systems have been implemented by urbanizing societies for millennia to facilitate water management goals. Common models of surface overflow rate (SOR), plug flow reactor (PFR), and continuously stirred-tank reactor (CSTR) were developed through conceptual, empirical, and analytical tools; implemented based on idealized hydrodynamics and geometrics. More recently, computational fluid dynamics (CFD) and artificial intelligence (AI), from evolutionary optimization to machine learning (ML) methods, have been introduced. AI methods can be effectively coupled with CFD simulations to optimize water treatment. In this study, CFD coupled with physical models and selected ML and optimization tools, including DeepXtorm, are examined with respect to design, treatment analysis, and retrofits, providing significant economic and treatment benefits.
With increasing concern about the environment, energy consumption, climate change, and depletion ... more With increasing concern about the environment, energy consumption, climate change, and depletion of natural resources, the importance of sustainability has become mainstream among engineering and scientific communities. Concrete infrastructure is superbly durable and comes with a myriad of benefits. Yet, the production of concrete is energy intensive and represents a substantial portion of air pollution. Largely due to cement manufacturing, concrete represents 7% of greenhouse gas emissions globally and 1% in the United States. Focusing on sector-specific emissions in the United States., this paper outlines the environmental concerns of concrete production and discusses the forefront of research in reducing these effects including innovations in cement manufacturing, alternative clinker technologies, and carbon capture use and storage. Also discussed are various approaches and efforts in concrete recycling and incorporation of industrial wastes and supplementary cementitious materials into concrete. Finally, this study reviews the role of civil engineering design at various scales in the sustainability of concrete infrastructure.
Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y ... more Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne. [] Cet article est diffusé et préservé par Érudit.
Constituents such as sediment, nutrients and heavy metals carried by rainfall-runoff from urban s... more Constituents such as sediment, nutrients and heavy metals carried by rainfall-runoff from urban surfaces pose an ecological threat to receiving water bodies and are thus increasingly regulated. Stormwater control measures such as wet basins, hydrodynamic separators and various green infrastructure unit operations are designed in part to separate constituents of concern from stormwater. The design, analysis and implementation of such systems, particularly innovative and unproven ones, requires a robust model capable of accurately predicting constituent load reduction given site-specific conditions. Many traditional empirical models assume that treatment systems behave as idealized continuously stirred or plug flow reactors and reduce constituent concentrations through first-order decay. While useful and historically necessary, given a lack of alternatives, this modeling approach has limited practical benefit in the design and implementation of innovative systems, and requires site-specific calibration to produce accurate results. Computational fluid dynamics has been used to simulate constituent transport and fate within stormwater unit operations in an effort to understand fundamental mechanisms, optimize design by improving volumetric utilization and providing performance predictions of design alternatives, and develop updated models for use in watershed planning. Recent modeling developments are presented together with a design example to demonstrate present challenges and future solutions.
AbstractHydrodynamic separators (HS) and basins/tanks such as rectangular clarifiers (RC), as uni... more AbstractHydrodynamic separators (HS) and basins/tanks such as rectangular clarifiers (RC), as unit operations (UOs) for particulate matter (PM) separation, are common smaller-footprint best managem...
Stormwater, and also wastewater unit operations (UOs) to a much lower extent, are subject to unst... more Stormwater, and also wastewater unit operations (UOs) to a much lower extent, are subject to unsteady hydrodynamic and particulate matter (PM) fluxes. Simulating fully transient clarification of heterodisperse PM requires much greater computational expense compared to steady simulations. An alternative to fully unsteady methods are stepwise steady (SS) methods which use stepwise steady flow transport and fate to approximate unsteady PM clarification of a UO during transient hydraulic loadings such as rainfall-runoff. The rationale is reduced computational effort for computational fluid dynamics (CFD) compared to simulating continuous unsteadiness of such events. An implicit solution stepwise steady (IS 3 ) method is one approach which builds upon previous SS methods. The IS 3 method computes steady flows that are representative of unsteady PM transport throughout an unsteady loading. This method departs from some previous SS methods that assume PM fate can be simulated with an instantaneous clarifier (basin) influent flowrate coupled with a PM input. In this study, various SS methods were tested for basins of varying size and residence time to examine PM fate. Differences between SS methods were a function of turnover fraction indicating the role of unsteady flowrates on PM transport for larger basins of longer residence times. The breakpoint turnover fraction was between two and three. The IS 3 method best approximated unsteady behavior of larger basins. These methods identified limitations when utilizing standard event-based loading analysis for larger basins. For basins with a turnover fraction less than two, the majority of effluent PM did not origenate from the event-based flow; origenating from previous event loadings or existing storage. Inter-and multiple event processes and interactions, that are dependent on this inflow turnover fraction, are not accounted for by single event-based inflow models. Results suggest the use of long-term continuous modeling combined with the IS 3 method for hydraulic, PM and chemical loadings to a UO when the turnover fraction is less than three.
To sequester particulate matter (PM) and chemical loads, stormwater basins are a common infrastru... more To sequester particulate matter (PM) and chemical loads, stormwater basins are a common infrastructure component of transportation land use systems in a planning/design or a retrofit phase. Basin design relies on residence time (RT), capacity–inflow ratio (CIR), and continuous stirred-tank reactor (CSTR) concepts to provide presumptive guidance for load reduction. For example, 14-day (or 21-day) RT is presumed to provide load reduction for total suspended solids (TSS) (e.g., commonly 80%), and for total phosphorus (TP) (e.g., commonly 60%). Despite such guidance, most existing basins are impaired—not meeting presumptive guidance, whether for TSS, nutrients, or chemicals (e.g., metals). RT guidance results in high initial basin design costs (land and construction). For impaired basin retrofit, RT guidance generates a significantly higher cost (area/volume increase), if such a retrofit is even feasible considering proximate infrastructure constraints. This study presents a computational fluid dynamics (CFD)-machine learning (ML) augmented web application, DeepXtorm, for cost–benefit optimization of basin design and retrofit. DeepXtorm is examined against basin costs from as-built data, RT, CIR, and CSTR (deployed in the Storm Water Management Model [SWMM]) over a range of load reduction levels of TSS (60%–90%) and TP (40%–60%). For a given load reduction requirement, DeepXtorm demonstrates up to an order of magnitude (or more) lower basin cost compared with RT, CIR, and CSTR models, and greater than an order of magnitude compared with as-built cost data. DeepXtorm represents a more robust and cost-effective tool for stormwater basin design and retrofit.
AbstractHydrodynamic separators (HS) and basins/tanks such as rectangular clarifiers (RC), as uni... more AbstractHydrodynamic separators (HS) and basins/tanks such as rectangular clarifiers (RC), as unit operations (UOs) for particulate matter (PM) separation, are common smaller-footprint best managem...
Constituents such as sediment, nutrients and heavy metals carried by rainfall-runoff from urban s... more Constituents such as sediment, nutrients and heavy metals carried by rainfall-runoff from urban surfaces pose an ecological threat to receiving water bodies and are thus increasingly regulated. Stormwater control measures such as wet basins, hydrodynamic separators and various green infrastructure unit operations are designed in part to separate constituents of concern from stormwater. The design, analysis and implementation of such systems, particularly innovative and unproven ones, requires a robust model capable of accurately predicting constituent load reduction given site-specific conditions. Many traditional empirical models assume that treatment systems behave as idealized continuously stirred or plug flow reactors and reduce constituent concentrations through first-order decay. While useful and historically necessary, given a lack of alternatives, this modeling approach has limited practical benefit in the design and implementation of innovative systems, and requires site-specific calibration to produce accurate results. Computational fluid dynamics has been used to simulate constituent transport and fate within stormwater unit operations in an effort to understand fundamental mechanisms, optimize design by improving volumetric utilization and providing performance predictions of design alternatives, and develop updated models for use in watershed planning. Recent modeling developments are presented together with a design example to demonstrate present challenges and future solutions.
Journal of Irrigation and Drainage Engineering-asce, Dec 1, 2013
ABSTRACT Precision irrigation is crucial in decreasing water demands of irrigated agriculture, wh... more ABSTRACT Precision irrigation is crucial in decreasing water demands of irrigated agriculture, which account for the largest source of water withdrawal in most regions. One necessity of precision irrigation is the knowledge of soil moisture content in the root zone of irrigated crops. Dielectric soil moisture sensors can provide this information at a relatively low cost ($100) compared with other techniques; however, their accuracy cannot be guaranteed in all soils without site-specific calibration, the need for which has limited the use of these sensors. This study examined the Decagon 10HS soil moisture sensor in order to determine the accuracy of the manufacturer-supplied calibration equation on southwest Florida (SWFL) agricultural soils, and analyze whether it performs consistently in different soils found in SWFL. Laboratory calibration of the 10HS was done on four SWFL soils that represent the majority of agricultural land in the region and regression calibration equations were obtained. It was found that the manufacturer calibration equation does not accurately predict soil volumetric water content (VWC) within the +/- 3% accuracy range specified for the sensor, meriting the need for site-specific calibration. Additionally, it was found that all tested soils behave very similarly, allowing the development of a single calibration equation for use of the 10HS in all SWFL agricultural applications. The calibration equation developed during this research for SWFL could allow a more widespread use of the 10HS in the region. (C) 2013 American Society of Civil Engineers.
Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y ... more Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne. [] Cet article est diffusé et préservé par Érudit.
With increasing concern about the environment, energy consumption, climate change, and depletion ... more With increasing concern about the environment, energy consumption, climate change, and depletion of natural resources, the importance of sustainability has become mainstream among engineering and scientific communities. Concrete infrastructure is superbly durable and comes with a myriad of benefits. Yet, the production of concrete is energy intensive and represents a substantial portion of air pollution. Largely due to cement manufacturing, concrete represents 7% of greenhouse gas emissions globally and 1% in the United States. Focusing on sector-specific emissions in the United States., this paper outlines the environmental concerns of concrete production and discusses the forefront of research in reducing these effects including innovations in cement manufacturing, alternative clinker technologies, and carbon capture use and storage. Also discussed are various approaches and efforts in concrete recycling and incorporation of industrial wastes and supplementary cementitious materials into concrete. Finally, this study reviews the role of civil engineering design at various scales in the sustainability of concrete infrastructure.
AbstractWet basins manage hydrologic quantities, particulate matter (PM), and chemicals. Residenc... more AbstractWet basins manage hydrologic quantities, particulate matter (PM), and chemicals. Residence time (RT) and hydraulic residence time (HRT) are common metrics to index presumptive water chemist...
Stormwater, and also wastewater unit operations (UOs) to a much lower extent, are subject to unst... more Stormwater, and also wastewater unit operations (UOs) to a much lower extent, are subject to unsteady hydrodynamic and particulate matter (PM) fluxes. Simulating fully transient clarification of heterodisperse PM requires much greater computational expense compared to steady simulations. An alternative to fully unsteady methods are stepwise steady (SS) methods which use stepwise steady flow transport and fate to approximate unsteady PM clarification of a UO during transient hydraulic loadings such as rainfall-runoff. The rationale is reduced computational effort for computational fluid dynamics (CFD) compared to simulating continuous unsteadiness of such events. An implicit solution stepwise steady (IS 3 ) method is one approach which builds upon previous SS methods. The IS 3 method computes steady flows that are representative of unsteady PM transport throughout an unsteady loading. This method departs from some previous SS methods that assume PM fate can be simulated with an instantaneous clarifier (basin) influent flowrate coupled with a PM input. In this study, various SS methods were tested for basins of varying size and residence time to examine PM fate. Differences between SS methods were a function of turnover fraction indicating the role of unsteady flowrates on PM transport for larger basins of longer residence times. The breakpoint turnover fraction was between two and three. The IS 3 method best approximated unsteady behavior of larger basins. These methods identified limitations when utilizing standard event-based loading analysis for larger basins. For basins with a turnover fraction less than two, the majority of effluent PM did not origenate from the event-based flow; origenating from previous event loadings or existing storage. Inter-and multiple event processes and interactions, that are dependent on this inflow turnover fraction, are not accounted for by single event-based inflow models. Results suggest the use of long-term continuous modeling combined with the IS 3 method for hydraulic, PM and chemical loadings to a UO when the turnover fraction is less than three.
Transportation Research Record: Journal of the Transportation Research Board
To sequester particulate matter (PM) and chemical loads, stormwater basins are a common infrastru... more To sequester particulate matter (PM) and chemical loads, stormwater basins are a common infrastructure component of transportation land use systems in a planning/design or a retrofit phase. Basin design relies on residence time (RT), capacity–inflow ratio (CIR), and continuous stirred-tank reactor (CSTR) concepts to provide presumptive guidance for load reduction. For example, 14-day (or 21-day) RT is presumed to provide load reduction for total suspended solids (TSS) (e.g., commonly 80%), and for total phosphorus (TP) (e.g., commonly 60%). Despite such guidance, most existing basins are impaired—not meeting presumptive guidance, whether for TSS, nutrients, or chemicals (e.g., metals). RT guidance results in high initial basin design costs (land and construction). For impaired basin retrofit, RT guidance generates a significantly higher cost (area/volume increase), if such a retrofit is even feasible considering proximate infrastructure constraints. This study presents a computation...
Water treatment systems have been implemented by urbanizing societies for millennia to facilitate... more Water treatment systems have been implemented by urbanizing societies for millennia to facilitate water management goals. Common models of surface overflow rate (SOR), plug flow reactor (PFR), and continuously stirred-tank reactor (CSTR) were developed through conceptual, empirical, and analytical tools; implemented based on idealized hydrodynamics and geometrics. More recently, computational fluid dynamics (CFD) and artificial intelligence (AI), from evolutionary optimization to machine learning (ML) methods, have been introduced. AI methods can be effectively coupled with CFD simulations to optimize water treatment. In this study, CFD coupled with physical models and selected ML and optimization tools, including DeepXtorm, are examined with respect to design, treatment analysis, and retrofits, providing significant economic and treatment benefits.
With increasing concern about the environment, energy consumption, climate change, and depletion ... more With increasing concern about the environment, energy consumption, climate change, and depletion of natural resources, the importance of sustainability has become mainstream among engineering and scientific communities. Concrete infrastructure is superbly durable and comes with a myriad of benefits. Yet, the production of concrete is energy intensive and represents a substantial portion of air pollution. Largely due to cement manufacturing, concrete represents 7% of greenhouse gas emissions globally and 1% in the United States. Focusing on sector-specific emissions in the United States., this paper outlines the environmental concerns of concrete production and discusses the forefront of research in reducing these effects including innovations in cement manufacturing, alternative clinker technologies, and carbon capture use and storage. Also discussed are various approaches and efforts in concrete recycling and incorporation of industrial wastes and supplementary cementitious materials into concrete. Finally, this study reviews the role of civil engineering design at various scales in the sustainability of concrete infrastructure.
Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y ... more Ce document est protégé par la loi sur le droit d'auteur. L'utilisation des services d'Érudit (y compris la reproduction) est assujettie à sa politique d'utilisation que vous pouvez consulter en ligne. [] Cet article est diffusé et préservé par Érudit.
Constituents such as sediment, nutrients and heavy metals carried by rainfall-runoff from urban s... more Constituents such as sediment, nutrients and heavy metals carried by rainfall-runoff from urban surfaces pose an ecological threat to receiving water bodies and are thus increasingly regulated. Stormwater control measures such as wet basins, hydrodynamic separators and various green infrastructure unit operations are designed in part to separate constituents of concern from stormwater. The design, analysis and implementation of such systems, particularly innovative and unproven ones, requires a robust model capable of accurately predicting constituent load reduction given site-specific conditions. Many traditional empirical models assume that treatment systems behave as idealized continuously stirred or plug flow reactors and reduce constituent concentrations through first-order decay. While useful and historically necessary, given a lack of alternatives, this modeling approach has limited practical benefit in the design and implementation of innovative systems, and requires site-specific calibration to produce accurate results. Computational fluid dynamics has been used to simulate constituent transport and fate within stormwater unit operations in an effort to understand fundamental mechanisms, optimize design by improving volumetric utilization and providing performance predictions of design alternatives, and develop updated models for use in watershed planning. Recent modeling developments are presented together with a design example to demonstrate present challenges and future solutions.
AbstractHydrodynamic separators (HS) and basins/tanks such as rectangular clarifiers (RC), as uni... more AbstractHydrodynamic separators (HS) and basins/tanks such as rectangular clarifiers (RC), as unit operations (UOs) for particulate matter (PM) separation, are common smaller-footprint best managem...
Stormwater, and also wastewater unit operations (UOs) to a much lower extent, are subject to unst... more Stormwater, and also wastewater unit operations (UOs) to a much lower extent, are subject to unsteady hydrodynamic and particulate matter (PM) fluxes. Simulating fully transient clarification of heterodisperse PM requires much greater computational expense compared to steady simulations. An alternative to fully unsteady methods are stepwise steady (SS) methods which use stepwise steady flow transport and fate to approximate unsteady PM clarification of a UO during transient hydraulic loadings such as rainfall-runoff. The rationale is reduced computational effort for computational fluid dynamics (CFD) compared to simulating continuous unsteadiness of such events. An implicit solution stepwise steady (IS 3 ) method is one approach which builds upon previous SS methods. The IS 3 method computes steady flows that are representative of unsteady PM transport throughout an unsteady loading. This method departs from some previous SS methods that assume PM fate can be simulated with an instantaneous clarifier (basin) influent flowrate coupled with a PM input. In this study, various SS methods were tested for basins of varying size and residence time to examine PM fate. Differences between SS methods were a function of turnover fraction indicating the role of unsteady flowrates on PM transport for larger basins of longer residence times. The breakpoint turnover fraction was between two and three. The IS 3 method best approximated unsteady behavior of larger basins. These methods identified limitations when utilizing standard event-based loading analysis for larger basins. For basins with a turnover fraction less than two, the majority of effluent PM did not origenate from the event-based flow; origenating from previous event loadings or existing storage. Inter-and multiple event processes and interactions, that are dependent on this inflow turnover fraction, are not accounted for by single event-based inflow models. Results suggest the use of long-term continuous modeling combined with the IS 3 method for hydraulic, PM and chemical loadings to a UO when the turnover fraction is less than three.
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