VISJET & VISFLOOD: Software for environment hydraulic modeling & visualization

We present two general interactive PC-based modeling and visualization software systems developed for the study of two types of environmental water flows: buoyant jet mixing and urban drainage problems. VISJET (http://www.aoe-water.hku.hk/visjet) is arguably the most robust software with advanced graphics for the prediction of mixing and transport of effluent discharges into a stratified crossflow. The prediction engine is a Lagrangian model for buoyant jets with three-dimensional trajectories, and is based on extensive basic experiments and turbulence model calculations. It can be used in outfall design and environmental impact assessment, and as an educational or training tool. VISFLOOD (http://www.aoe-water.hku.hk/visflood) is based on the numerical solution of the Saint-Venant equations, and caters for the simulation of unsteady flood propagation in urban drainage systems. Both software systems are fully interactive with data interrogation; the 3D visualization is fully integrated with the model engine, and enables the user to appreciate the context of the problem in a most effective way. Both models have been well-validated against laboratory and field data, and have been applied to many actual engineering projects. This software product is an outcome of a grant by the Hong Kong Innovation and Technology Fund (ITF).published_or_final_versio

VISJET-a computer ocean outfall modelling system

Sewage and industrial effluents from coastal cities are often discharged into the adjacent sea after some land-based treatment. In modern design, the wastewater is often discharged in buoyant jet groups from risers mounted on a submarine outfall on the seabed to achieve rapid mixing of effluents with tidal flow. A mathematical model for buoyant jets in currents based on the Lagrangian models, called JETLAG, was developed. The paper presents a system called VISJET, for visualizing the ocean sewage discharge system based on the JETLAG model. We discuss the features of VISJET system and show how computer visualization can be used to help with the design of an ocean sewage discharge system.published_or_final_versio

Modelling dilution and transport processes from marine outfall discharges.

Municipal, industrial and desalination wastewater is commonly discharged into coastal waters. Marine outfalls are a common wastewater disposal system used in coastal areas, consisting on a pipe or tunnel, or the combination of both, that ends in a diffuser. The aim of the diffuser is to mix the effluent in the receiving waters. Accurate prediction of mixing and dispersion in the near field of marine outfall discharges is important to prevent pollutants present in wastewater from affecting the water quality of the receiving environment. Traditionally, marine discharges have been modelled using empirical or entrainment models. Computational Fluid Dynamics (CFD) approaches have rarely been used to model this situation, despite their great potential. This thesis aimed to assess how coupling CFD near field models with far field circulation models can be implemented to improve predictive capability of dilution and pollutant fate and transport in the near and far field of marine outfalls with multiport diffusers. The present work includes the description and validation of a CFD modelling methodology for the simulation of the near field of single and multiple ports discharges at laboratory scale. A mesh adaption approach was used to capture geometric and flow detail around the discharge port while reducing computational resource requirements. Predictions of flow trajectory, velocity and dilution generally show good agreement with available experimental data. This approach demonstrates improved predictive capability for velocity and dilution when compared against conventional buoyant jet entrainment models. The dynamics of merging between plumes were successfully captured by RANS based k-ε and k-σ models. Further studies were conducted focusing on the simulation of a real-life marine outfall located in the city of Cartagena, Colombia. The sensitivity of the outfall performance to a variety of parameters, including port alignment and other discharge and ambient conditions was assessed. The level of dilution obtained by the outfall showed great sensitivity to port alignment and Roberts Froude number. A framework for the implementation of the CFD methodology implemented here to other marine outfalls is presented. The CFD near field model results obtained for the Cartagena marine outfall were successfully coupled to the far field circulation model Delft3D by inputting a near field discharge flow vertical profile into the far field model. Time-dependent and other complex processes such as tidal forcing, density stratification and wind effects were ignored to isolate the individual parameters of interest for their analysis. The far field model showed little sensitivity to the coupling model used under the conditions studied. The overall aim of this thesis was achieved and a framework for the application of CFD near field models and its subsequent coupling with far field circulation models was proposed. RANS turbulence models produce reliable predictions of single and multiple port buoyant jet discharges from marine outfalls. The computational cost of this modelling method was reduced by implementing solution-based mesh adaption. Time-dependent processes and variations in the discharge and ambient conditions would be the next step in understanding the behaviour of near and far field models of marine outfalls

Zonation of positively buoyant jets interacting with the water-free surface quantified by physical and numerical modelling

ABSTRACT: The evolution of positively buoyant jets was studied with non-intrusive techniques-Particle Image Velocimetry (PIV) and Laser Induce Fluorescence (LIF)-by analyzing four physical tests in their four characteristic zones: momentum dominant zone (jet-like), momentum to buoyancy transition zone (jet to plume), buoyancy dominant zone (plume-like), and lateral dispersion dominant zone. Four configurations were tested modifying the momentum and the buoyancy of the effluent through variations of flow discharge and the thermal gradient with the receiving water body, respectively. The physical model results were used to evaluate the performance of numerical models to describe such flows. Furthermore, a new method to delimitate the four characteristic zones of positively buoyant jets interacting with the water-free surface was proposed using the angle (?) shaped by the tangent of the centerline trajectory and the longitudinal axis. Physical model results showed that the dispersion of mass (concentrations) was always greater than the dispersion of energy (velocity) during the evolution of positively buoyant jets. The semiempirical models (CORJET and VISJET) underestimated the trajectory and overestimated the dilution of positively buoyant jets close to the impact zone with the water-free surface. The computational fluid dynamics (CFD) model (Open Field Operation And Manipulation model (OpenFOAM) is able to reproduce the behavior of positively buoyant jets for all the proposed zones according to the physical resultsFunding: The work described in this paper is part of a research project financed by the VI National Plan (2008–2012) for Research in Science and Technological Innovation of the Spanish Government (VERTIZE CTM2012-32538)

Development of an Integrated System for the Simulation and Assessment of Produced Water Discharges from Offshore Platforms

Techniques for modeling of marine pollution have been studied for decades. Specialized modeling methods have been used to simulate the dispersions of pollutants from offshore outfalls. Produced water, the largest volume waste stream discharged from offshore oil and gas production activities, is a complex mixture of dissolved and particulate organic and inorganic chemicals including metals and hydrocarbons. In recent years, the growing importance and interest in the ocean environment assessment has urged further evaluation of produced water impacts on the marine ecosystem. This thesis study describes an integrated system for the modeling and assessment of produced water discharges in coastal area. The system integrates ocean circulation simulation, pollutant fate and transport modeling that couples near field mechanisms and far field processes, and risk assessment approaches where exposure risks and probabilistic risks are evaluated. A literature survey is first introduced to review and present capabilities and limitations of the most widely used methods and models associated with assessment of the impact of marine pollution. This review identified the need for an integrated system with configurations of numerical schemes of Princeton Ocean Model (POM) for ocean circulation simulation, a Lagrangian method to simulate near field transport processes in three dimensional cross flows, and a numerical solution for far field transport modeling. The physical models are dynamically integrated to ensure mass and energy conservation. Furthermore to assess risks, a modified Monte Carlo method which uses a statistical model to establish the relationship between uncertainty parameters and output concentrations is integrated with physical modeling system along with risk characterization approaches to map risk levels. Evaluation and field validations are conducted for each individual sub-models and for the overall integrated modeling results. Specifically, the near field model is validated against a field study performed in USA platform located about 100 miles of New Orleans Louisiana. The computational efficiency and accuracy of the far field model are evaluated through test cases in comparison with concentration distribution results generated from an exact analytical solution and a RWPT (Random Walk Particle Tracking) method. Validations of ocean circulation results and the integrated produced water dispersion results are conducted in a case study carried out on the Grand Banks of Newfoundland, Canada. Validations show good performance of the developed modeling system which is used to provide satisfactory 3D simulation of marine pollutant dispersion for effective assessment and management of offshore waste discharges. Finally, a risk assessment is carried out to predict risks associated with predicted lead and benzene concentration resulting from potential future produced water discharges in the East Coast of Canada. This research study provide a tool for the modeling of complex transport processes in the coastal area, and improved methods for risk assessment of produced water impacts on the regional water environment

Hydrolink 2020/4. Artificial intelligent

Topic: Artificial Intelligenc

On the turbulence in negatively Buoyant Jets

Negatively buoyant jets (NBJ) have been investigated with both a laboratory simulation (with a Feature Tracking Velocimetry, FTV, technique, to measure velocity fields) and a numerical simulation (with an Immersed Boundary method, in which the velocity fields are computed by a DNS method and the concentration by a LES method).This phenomenon can be found in a number of practical applications, e.g. the sea discharge of brine from desalination plants through submerged outfalls, oil or gas drilling facilities and mineral salt industries e.g. from leaching of mineral salts domes, gypsum or acidic wastes from fertilizer factories, etc.. These jets are typically released upwards, with a certain angle on the horizontal, to increase the path before to sink in the seafloor, to maximize the dilution, therefore the NBJs are initially driven from a source of both momentum, so behave basically as simple jets, far from the outlet the buoyancy prevails, bending the jet similar to a plume. To understand the processes that govern the dilution is important study the turbulent mixing and the entrainment. In this work are presented the results, under a large range of conditions (e.g. angle of the diffuser, density of the brine, release into a stagnant environment), will be shown; in particular, first order statistics, to study the characteristic dimensions of the jet. The second and third order statistics, to study the turbulent quantities

On the turbulence in negatively Buoyant Jets

Negatively buoyant jets (NBJ) have been investigated with both a laboratory simulation (with a Feature Tracking Velocimetry, FTV, technique, to measure velocity fields) and a numerical simulation (with an Immersed Boundary method, in which the velocity fields are computed by a DNS method and the concentration by a LES method).This phenomenon can be found in a number of practical applications, e.g. the sea discharge of brine from desalination plants through submerged outfalls, oil or gas drilling facilities and mineral salt industries e.g. from leaching of mineral salts domes, gypsum or acidic wastes from fertilizer factories, etc.. These jets are typically released upwards, with a certain angle on the horizontal, to increase the path before to sink in the seafloor, to maximize the dilution, therefore the NBJs are initially driven from a source of both momentum, so behave basically as simple jets, far from the outlet the buoyancy prevails, bending the jet similar to a plume. To understand the processes that govern the dilution is important study the turbulent mixing and the entrainment. In this work are presented the results, under a large range of conditions (e.g. angle of the diffuser, density of the brine, release into a stagnant environment), will be shown; in particular, first order statistics, to study the characteristic dimensions of the jet. The second and third order statistics, to study the turbulent quantities

Impact of Albufeira bay outfall plumes in bathing water quality, a modelling approach

Dissertação de mestrado, Ciclo Urbano da Água, Instituto Superior de Engenharia, Universidade do Algarve, 2017O turismo em zonas balneares é responsável por pressões nas infraestruturas do ciclo urbano da água e recursos hídricos, nomeadamente na conceção de sistemas de abastecimento de água e saneamento. O presente trabalho tem como objetivo avaliar o comportamento hidrodinâmico de três emissários submarinos e impacte na qualidade das águas balneares na baía de Albufeira usando uma abordagem de modelação matemática, com base no software MOHID. São investigados os principais processos que controlam a dispersão na baía. Os primeiros desenvolvimentos consistem numa série de campanhas de medição e colheita de dados (parâmetros microbiológicos, caudais, vento, etc.) que fornecem os dados para caracterizar a dispersão neste sistema costeiro. Uma rede de pontos de observação e controlo são definidos para avaliar o impacte das plumas na zona de influência dos emissários submarinos. A aplicação e desenvolvimento do modelo de dispersão proporciona uma melhor compreensão e controlo dos processos de diluição e dispersão na baía. Os resultados da modelação são utilizados para avaliar a necessidade de desinfeção, que pode reduzir custos operacionais e permitirá um aumento da resiliência do sistema em caso de falhas nas infraestruturas de colheita, transporte e de tratamento de águas residuais e proporcionar um melhor funcionamento e gestão de instalações

Physical modelling of desalination discharges impacting an inclined boundary.

The purpose of this research is to improve the current understanding of the mixing processes and dilution of negatively buoyant jets impacting an inclined boundary in a stationary environment. This work has direct application to the discharge of brine from a desalination plant, but has broader implications for other industrial discharges. Improvements in our current understanding were be gained from a comprehensive experimental program and comparisons with associated numerical models. The predictive capabilities of these numerical models have key benefits for industry in design and environmental impact assessment processes, and outcomes of compliance and monitoring processes. In this context predictive capabilities of flow scale, dilution and location are particularly important for these complex flows. Thus the primary motivation for this study is embedded in the application to discharges from large-scale desalination plants that typically result in jets of dense effluent into the ocean, near the sea floor, and it is necessary to demonstrate that these discharges meet environmental constraints within a prescribed mixing zone. The relatively dense effluent initially rises towards the ocean surface because of its initial momentum, but subsequently falls back to the ocean floor because of its negative buoyancy. There is a long history (70 years +) of research into the near field mixing and dilution of positively buoyant jets, as they are the result of the more common fresh-water municipal discharge into a marine environment. While the behaviour of these flows are governed by the same principles, there is significantly less research into the behaviour of negatively buoyant discharges. It has been noted by previous researchers that there is a lack of robust experimental results in this area, in particular assessing the dilution characteristics in the impact region, when the flow returns to the ocean floor (bottom boundary). The most recent studies have provided some clarity on this issue, but these studies have been limited to flows impacting a horizontal boundary. Consequently this research program included a comprehensive experimental program that generated high quality dilution data for negatively buoyant discharges impinging on boundaries with different slopes. Experiments were carried for discharge angles ranging from 30◦ to 60◦ because these are representative of potential industrial applications. The boundary angle was varied from 0◦ to 20◦, which is consistent with previous numerical studies for these discharges on sloped boundaries. Variations in the initial discharge densimetric Froude number provided opportunities to assure the quality of the data because the flow is expected to scale on this dimensionless parameter. A Laser-Induced Fluorescence (LIF) system was employed to measure planar concentration fields along the centreline of the flow. This measuring system has provided detailed information about the scale, dilution and location of the flow in the impact region. Impact point dilution and location data have been extracted from a unique and comprehensive experimental data set that covers lower boundary (seabed) angles from 0◦ to 20◦ , discharge angles of 30◦ , 45◦ and 60◦ , non-dimensional source heights ranging from -0.09 to 5.04, and initial densimetric Froude numbers ranging from 10.98 to 52.77. This data has been compared with predictions from a relatively simple semi-analytical model. These comparisons show that predictions of the impact point dilution, and the horizontal and vertical coordinates of the impact point, are in good agreement with the measured data. This agreement supports the use of the model to predict conditions at the impact point for lower boundary (seabed) inclinations up to 20◦ below a horizontal reference plane. This agreement also suggests that the mixing prior to reaching the impact point is not adversely affected by the presence of the lower boundary. The boundary data presented demonstrates that the mixing achieved in the immediate proximity of the impact point is most sensitive to boundary inclination when the effluent is released at 60◦, and that notable additional mixing (a 26% increase) can be achieved within 2 boundary length scales of the impact point. The relationship between the boundary length and the flow path length to the impact point enables scaling of the above results to a range of marine disposal scenarios for large scale desalination facilities. This new information is potentially valuable when considering compliance of these different scenarios in the context of pre-defined regulatory mixing zones, or alternatively in defining appropriate regulatory mixing zones for a given discharge scenario