Environmental Fluid Mechanics, volume 25, issue 1, publication number 7

RANS model predictions for desalination discharges implemented with a dynamic turbulent Schmidt number approach

Shuen Law 1
, 
Mark Davidson 1
, 
Craig McConnochie 1
, 
Daniel Lagrava 2
1
 
2
 
Spire Global Luxembourg, Luxembourg, Luxembourg | 
Publication type: Journal Article
Publication date: 2025-01-16
scimago Q2
wos Q3
SJR: 0.570
CiteScore: 4.5
Impact factor: 1.7
ISSN: 15677419, 15731510
Abstract

Desalination discharges are commonly in the form of inclined negatively buoyant jets (INBJs). Numerical predictions of INBJs remain a challenge. While accurate large eddy simulations (LES) of INBJs have become available very recently, they are substantially more resource intensive. Reynolds-averaged Navier–Stokes (RANS) modelling is potentially more efficient and can be more readily applied in practice. However, existing RANS simulations show substantial error when compared with experimental measurements. In this study, RANS simulations of 45° INBJs are performed with a dynamic turbulent Schmidt number (DTSN) approach. This new approach involves extracting turbulent Schmidt number ( $$S{c}_{t}$$ S c t ) profiles in the INBJs from recently published LES data that have been validated by experiments. Detailed cross-sectional $$S{c}_{t}$$ S c t profiles in INBJs are reported here for the first time. The relationship between $$S{c}_{t}$$ S c t and a local mean flow parameter is also determined from the LES data. RANS simulations are then performed—with $$S{c}_{t}$$ S c t being allowed to change dynamically during the simulation according to the pre-determined relationship. The results show that the DTSN approach improved the overall predictive capabilities of the RANS model to a limited extent. However, significant issues remain in terms of the models’ ability to predict dilutions in the descending portion of the flow. Importantly, the DTSN simulations demonstrate that the model predictions are sensitive to the determination of the relationship between $$S{c}_{t}$$ S c t and the local flow parameter. Further improvements in the DTSN approach are therefore possible with refinement to the characterisation of this relationship. Based on a discussion of the present and recent literature describing RANS simulations of INBJs, the authors encourage a more cautious interpretation of the current predictive capabilities of RANS simulations in the context of INBJs.

Found 48
By date By citations
Springer Nature
Improved numerical predictions of inclined negatively buoyant jet behaviour
Law S., Davidson M.J., McConnochie C., Lagrava D.
Environmental Fluid Mechanics scimago Q2 wos Q3 , 
2023-07-10,  citations by CoLab: 3 ,  Abstract  
AbstractThe results of numerical simulations of inclined negatively buoyant jets are presented. These simulations address previously highlighted difficulties in capturing sufficient detail of critical flow processes to effectively predict the detailed flow behaviour. In particular, the new simulations are able to accurately capture the details of the buoyancy-induced instabilities, which are clearly evident in associated experimental investigations and that have significant impacts on the flow behaviour. This new information is captured for inclined negatively buoyant jets discharged at 45° above a horizontal reference plane. A Large Eddy Simulation (LES) approach is implemented that makes use of a Lagrangian Dynamic Sub-grid scale (SGS) model and a novel criterion for the adaptive meshing system. Comparisons with previously published simulation results and experimental data demonstrate that these new Adaptive LES simulations provide improved predictions of flow path, concentration and velocity fields, and associated mean and turbulent statistics. In addition, this study provides a set of methods for generating high-quality LES data sets for free shear flows, which are well beyond the level of detail that can be captured by current experimental systems.
Springer Nature
Reynolds flux modeling; new numerical insights into inclined dense jets
Tahmooresi S., Mohammadian A., Nistor I., Kheirkhah Gildeh H.
Environmental Fluid Mechanics scimago Q2 wos Q3 , 
2023-04-06,  citations by CoLab: 3 ,  Abstract  
This paper aims to provide a more detailed representation of the scalar flux modeling (SFM) approach for modeling turbulent inclined negatively buoyant jets. The SFM approach addresses the limitations of eddy viscosity models in terms of the mean concentration field and turbulent scalar flux within the context of Reynolds-averaged Navier–Stokes modeling. In this study, the contribution of the involved terms in the transport equation of the turbulent scalar flux vector was evaluated, and the geometrical and mixing parameters of concentration and velocity of 45 $$^\circ$$ inclined negatively buoyant jets were verified. The SFM approach, along with the required modification for momentum flux modeling, was implemented in OpenFOAM v6. Results showed that the SFM approach can accurately predict mixing parameters due to the complex interactions between different turbulence contributors of the flow involved in the model. In comparison to simpler approaches, such as gradient-type models, that only correlate the gradient of the scalar field with turbulence, the SFM approach’s capability to predict mixing parameters is significantly higher.
Elsevier
Laboratory study to quantify lower boundary influences on desalination discharges
Ramakanth A., Davidson M.J., Nokes R.I.
Desalination scimago Q1 wos Q1 , 
2022-05-01,  citations by CoLab: 10 ,  Abstract  
Brine discharges from desalination facilities represent an important environmental consideration surrounding the use of desalination technologies. These discharges are typically released through a series of subsurface discharge ports, and the ability to quantify their flow behaviour is critical to mitigating adverse environmental effects. Previous experimental studies on desalination discharges or Inclined Negatively Buoyant Jets have highlighted discrepancies in the dilution measurements reported in the literature. These discrepancies are potentially due to the inconsistent treatment of the lower boundary in the experimental setup, which in practice represents the seabed. This issue is investigated through a series of experiments using the Laser Induced Fluorescence method. Three discharge angles (30 0 , 45 0 and 60 0 ) are tested and the non-dimensional source height above the boundary (H/F 0 d) is varied between 0.06 and 1.84 (termed the bed proximity parameter). The results illustrate a relationship between dilutions measured at common reference points near the boundary and the bed proximity parameter. Dilutions are also shown to decrease by up to 30% compared to experiments without lower boundary influence. The outcomes from this study provide valuable insight into the previously reported discrepancies and enable the lower boundary to be incorporated into the design of desalination discharge systems. • An experimental program was developed to investigate the influence of a lower boundary on desalination discharges. • Experiments were carried out using the Laser Induced Fluorescence (LIF) method. • Geometric and dilution results were extracted from the experiments and used to characterise the flow behaviour. • Empirical equations were developed to predict flow dilutions at key reference locations along the flow path. • Empirical equations were developed to determine whether the lower boundary will impact the flow behaviour.
Springer Nature
Application of Reynolds flux modeling in CFD simulation of 45$$^{\circ}$$ inclined negatively buoyant jets
Tahmooresi S., Ahmadyar D.
Environmental Fluid Mechanics scimago Q2 wos Q3 , 
2022-01-04,  citations by CoLab: 6 ,  Abstract  
Predicting mixing parameters and mean concentration field of inclined negatively buoyant jets (INBJs) appropriately, has been a long-lasting challenge in numerical modeling of this type of jet flows. To address this challenge, 45 $$^{\circ}$$ inclined dense jets were simulated in OpenFOAM hiring three different approaches as Boussinesq-based and non-Boussinesq-based ones. The first approach was conducted by using a two-equation turbulence model, realizable k– $$\epsilon$$ (RKE), in correlation with the standard gradient diffusion hypothesis (SGDH). In the second one, as the pure non-Boussinesq-based approach, turbulent scalar flux modeling (SFM), as an implicit second-moment closure-based approach, for the first time, was combined with the SSG turbulence model. Setting the model coefficients was conducted for both the SSG and SFM given that the calibration is a mutually coupled problem. The best agreement with the experimental data was found in approach two, where the return point dilution ratio, Sr/Fr, shows an increase about the 70%, 32%, 86% over their counterparts in approach one, the large eddy simulation (LES), and the standard k– $$\epsilon$$ , respectively. Quantitative comparisons for bulk parameters (geometrical and mixing) confirms that the SFM approach stands out with $$\sim 4\%$$ average error while the corresponding value is $$\sim 19\%$$ for the SGDH approach. These significant improvements over the prediction of mixing parameters can be perceived as the main benefit of the hired SFM approach. Evaluating the turbulent scalar flux vector was performed for both approaches, and it was shown that the SFM is more coordinated with the physics of the flow, compared to the SGDH, concerning the evolutionary behavior of the flow moving from the upstream to the downstream captured by the SFM. Regarding the LES simulations hiring high-performance computers and large quantities of grid numbers, the SFM can be regarded as the best RANS option to model the INBJs. This is the case, specifically, for the mixing parameters.
American Chemical Society (ACS)
Does the Green Hydrogen Economy Have a Water Problem?
Beswick R.R., Oliveira A.M., Yan Y.
ACS Energy Letters scimago Q1 wos Q1 , 
2021-08-17,  citations by CoLab: 161 , 
Institute of Electrical and Electronics Engineers (IEEE)
Numerical Differentiation of Noisy Data: A Unifying Multi-Objective Optimization Framework
Van Breugel F.V., Kutz J.N., Brunton B.W.
IEEE Access scimago Q1 wos Q2 Open Access , 
2020-10-27,  citations by CoLab: 74 ,  Abstract  
Computing derivatives of noisy measurement data is ubiquitous in the physical, engineering, and biological sciences, and it is often a critical step in developing dynamic models or designing control. Unfortunately, the mathematical formulation of numerical differentiation is typically ill-posed, and researchers often resort to an ad hoc process for choosing one of many computational methods and its parameters. In this work, we take a principled approach and propose a multi-objective optimization framework for choosing parameters that minimize a loss function to balance the faithfulness and smoothness of the derivative estimate. Our framework has three significant advantages. First, the task of selecting multiple parameters is reduced to choosing a single hyper-parameter. Second, where ground-truth data is unknown, we provide a heuristic for selecting this hyper-parameter based on the power spectrum and temporal resolution of the data. Third, the optimal value of the hyper-parameter is consistent across different differentiation methods, thus our approach unifies vastly different numerical differentiation methods and facilitates unbiased comparison of their results. Finally, we provide an extensive open-source Python library pynumdiff to facilitate easy application to diverse datasets (https://github.com/florisvb/PyNumDiff).
Social Science Electronic Publishing
Green Hydrogen: The Holy Grail of Decarbonisation? An Analysis of the Technical and Geopolitical Implications of the Future Hydrogen Economy
Scita R., Raimondi P.P., Noussan M.
SSRN Electronic Journal , 
2020-10-15,  citations by CoLab: 35 ,  Abstract  
Hydrogen is currently enjoying a renewed and widespread momentum in the energy market. In the last years, demand for hydrogen has substantially increased worldwide, with several countries developing hydrogen national strategies, and private companies investing in the development of hydrogen related projects. Green hydrogen’s environmental sustainability and versatility contribute to its representation as the holy grail of decarbonisation. This working paper challenges this definition, by analysing the historical process which contributed to hydrogen’s rise, showing the current uses of hydrogen and the major obstacles to the implementation of a green hydrogen economy, and assessing the geopolitical implications of a future hydrogen society. Particularly, the paper shows that the hydrogen economy is still far from becoming reality. Even though investments in green hydrogen technologies and projects have increased over the last decade, there still remains a high number of unresolved issues, relating to technical challenges and geopolitical implications. Nonetheless, a clean hydrogen economy offers promising opportunities not only to fight climate change, but also to redraw geopolitical relations between states. The energy transition is already taking place, with renewable energies gradually eroding the global energy system based on fossil fuels. A global transformation, set in motion by the need to decarbonise the energy system, will have the potential to redraw international alliances and conflicts. In this context, hydrogen may play a crucial role. By 2050, hydrogen could indeed meet up to 24% of the world’s energy needs, thus highly influencing the geopolitical landscape. In this regard, the choice over which pathway to take for the creation of hydrogen value chains will have a huge geopolitical impact, resulting in new dependencies and rivalries between states. Conclusively, if national governments are willing to spur the emergence of a green hydrogen economy, they should heavily invest in research and development, encourage the development of a clean hydrogen value chain, and promote common international standards. Moreover, they should also take into account hydrogen’s geopolitical implications. If the hydrogen economy is well-managed, it could indeed increase energy security, diversify the economy, and strengthen partnerships with third countries.
Springer Nature
Effects of turbulent Schmidt number on CFD simulation of $$45^\circ $$ inclined negatively buoyant jets
Tahmooresi S., Ahmadyar D.
Environmental Fluid Mechanics scimago Q2 wos Q3 , 
2020-08-18,  citations by CoLab: 15 ,  Abstract  
Employing inclined negatively buoyant jets is one of the most advantageous means to discharge brine or waste in coastal environments. However, numerical prediction of mixing parameters for this kind of flow is still a challenge. In this investigation, CFD simulations of $$45^\circ $$ inclined dense jets were conducted using realizable k– $$\epsilon $$ model with buoyancy corrections and different values of turbulent Schmidt number ( $$Sc_t$$ ) within two approaches in a finite volume model (Open FOAM). In the first approach, seven scenarios with different values of $$Sc_t$$ were simulated. In the second one, a Regional Turbulent Schmidt Number (RTSN) configuration was introduced based on different behaviors of the flow in jet-like, plume-like, and inner/outer regions. Regarding the first approach, results showed that changing the turbulent Schmidt number has significant consequences for mixing and geometrical parameters. Reducing $$Sc_t$$ from 1.0 to 0.4 led to more than $$\sim 60\%$$ and $$\sim 40\%$$ improvements in dilution ratio at return point and centerline peak, respectively. Using RTSN approach successfully improved the mixing parameters along with keeping nearly unchanged the accuracy of geometrical parameters. That was the case, specifically at return point in comparison with using any other constant $$Sc_t$$ for the whole domain (first approach). This local (regional) change in turbulent Schmidt number compensates for flaws of Boussinesq approximation in the linear two-equation turbulence modeling of inclined negatively buoyant jets. Comparing to the previous LES results, the RTSN approach combined with the realizable k– $$\epsilon $$ model stands as an economically superior solution employing much lower grid numbers.
American Society of Civil Engineers (ASCE)
Field-Scale Numerical Modeling of a Dense Multiport Diffuser Outfall in Crossflow
Baum M.J., Gibbes B.
Journal of Hydraulic Engineering scimago Q2 wos Q3 , 
2019-11-15,  citations by CoLab: 21 ,  Abstract  
AbstractA numerical investigation of near-field brine discharge dynamics is reported for the Gold Coast Desalination Plant offshore inclined multiport brine diffuser. Quasi-steady computational flu...
MDPI
Numerical Modeling of Multiple Inclined Dense Jets Discharged from Moderately Spaced Ports
Yan, Mohammadian
Water (Switzerland) scimago Q1 wos Q2 Open Access , 
2019-10-05,  citations by CoLab: 19 ,  PDF,  Abstract  
Wastewaters are often discharged into water bodies from multiport diffusers in the form of inclined dense jets, and it is important to predict their mixing characteristics for a sound sustainable design for seawater desalination. Compared with single jets and multiple horizontal or vertical jets, the mixing processes of multiple inclined dense jets are more complicated, and thus the existing theoretical, analytical, or simplified numerical methods cannot effectively predict their dilution properties. Recent advances in numerical modeling techniques have provided a new avenue of simulating wastewater jets as three-dimensional phenomena, but their application to multiple inclined dense jets has rarely been reported. In this study, a fully three-dimensional numerical model is employed to simulate multiple inclined brine discharges from diffusers with moderately spaced ports, with the standard and re-normalization group (RNG) k-ε turbulence closures being tested. The simulated characteristic variables are compared to experimental data, and the results show that the simulations match very well with the experiments, demonstrating that the numerical model is a promising tool for simulating inclined dense jets discharged from multiport diffusers. The study also found that the RNG k-ε model performs better than the standard k-ε model without significantly increasing the computational costs.
Valuing water
Schmidt J.J.
2019-09-06,  citations by CoLab: 12 , 
Elsevier
The state of desalination and brine production: A global outlook.
Jones E., Qadir M., van Vliet M.T., Smakhtin V., Kang S.
Science of the Total Environment scimago Q1 wos Q1 , 
2019-03-01,  citations by CoLab: 1273 ,  Abstract  
Rising water demands and diminishing water supplies are exacerbating water scarcity in most world regions. Conventional approaches relying on rainfall and river runoff in water scarce areas are no longer sufficient to meet human demands. Unconventional water resources, such as desalinated water, are expected to play a key role in narrowing the water demand-supply gap. Our synthesis of desalination data suggests that there are 15,906 operational desalination plants producing around 95 million m3/day of desalinated water for human use, of which 48% is produced in the Middle East and North Africa region. A major challenge associated with desalination technologies is the production of a typically hypersaline concentrate (termed 'brine') discharge that requires disposal, which is both costly and associated with negative environmental impacts. Our estimates reveal brine production to be around 142 million m3/day, approximately 50% greater than previous quantifications. Brine production in Saudi Arabia, UAE, Kuwait and Qatar accounts for 55% of the total global share. Improved brine management strategies are required to limit the negative environmental impacts and reduce the economic cost of disposal, thereby stimulating further developments in desalination facilities to safeguard water supplies for current and future generations.
Springer Nature
Turbulence characteristics of 45° inclined dense jets
Jiang M., Law A.W., Lai A.C.
Environmental Fluid Mechanics scimago Q2 wos Q3 , 
2018-07-11,  citations by CoLab: 27 ,  Abstract  
In the present study, we performed an extensive laboratory investigation to quantify the turbulence characteristics of 45° inclined dense jets using Particle Image Velocimetry (PIV) over a wide range of Densimetric Froude Number. The objective was to provide benchmark data to guide high resolution turbulence numerical simulations for dense jets in the future. The PIV measurements were sampled at a relatively high frequency of 50 Hz, which enabled the analysis of second order turbulence statistics as well as the turbulence kinetic energy spectrum (including the inertial subrange) along the curvilinear jet trajectory, which has hitherto not been reported. The measurements showed that the spectral profile was flat near the discharge port with the potential core, since the Kelvin–Helmholtz shear-induced turbulence at the jet boundaries had not fully penetrated to the core. The spectral profile then evolved along the trajectory with progressive steepening towards the higher frequencies, and a fully-developed profile appeared beyond the terminal rise with a clearly identifiable inertial subrange for the energy cascade. In parallel, we also performed numerical simulations using the Large Eddy Simulations (LES) approach with the Dynamic Smagorinsky sub-grid model for the specific discharge conditions as in the experiments. The LES approach followed that of Zhang et al. (Environ Fluid Mech 16(1):101–121, 2016, J Hydro Environ Res 15:54–66, 2017) using GCI as the grid convergence criteria. The comparison showed that the time-averaged first order mixing characteristics of the inclined dense jet can be simulated reasonably well comparing to the experimental data. In terms of the turbulence kinetic energy spectrum, the low frequencies of the production range were also well captured by the simulations. However, the simulated transitional spectra towards the inertial subrange decayed substantially faster than the experiments. The discrepancy was attributed to the fact that the grid resolution was not sufficiently fine in the simulations (which were constrained by the available computational resources and time), such that stratified effects remained present inside the sub-grids producing additional turbulence energy that were not represented by the Dynamic Smagorinsky model. Thus, the numerical investigation showed that further improvement in sub-grid models that can incorporate the stratified effects would be desirable in the future for engineering simulations.
Elsevier
Large eddy simulations of 45° and 60° inclined dense jets with bottom impact
Zhang S., Law A.W., Jiang M.
Journal of Hydro-Environment Research scimago Q2 wos Q2 , 
2017-06-01,  citations by CoLab: 41 ,  Abstract  
In the present study, we performed a numerical study with the Large Eddy Simulations (LES) approach to simulate inclined dense jets with 45° and 60° inclinations in a stagnant ambient, including the bottom impact and subsequent spreading on the wall boundary. The objective was to evaluate the performance of LES on the predictions of both the kinematic and mixing behavior of the inclined dense jet with bottom boundary in the near field region. The Dynamic Smagorinsky sub-grid model was adopted with near-wall modeling for the bottom boundary. The results showed that LES can reasonably predict the jet trajectory with the present mesh scheme, including the locations of the return point and impact point at the boundary. The localized concentration build-up at the impact point reported by Abessi and Roberts (2015) was also reproduced. The impact dilution was however underestimated by ∼20% in general corresponding to the grid resolution adopted in the present study, which demonstrated the challenge to simulate accurately the dynamics of the mixing behaviour as well as the wall interaction processes. The spreading layer was examined to the end of the near field region as defined by Roberts et al. (1997). The profiles of the mean concentration and concentration fluctuation along the spreading layer were found to be similar to previous experimental results with self-similar behaviour. The dilution was however also under-predicted within the spreading layer.
MDPI
On the Values for the Turbulent Schmidt Number in Environmental Flows
Gualtieri C., Angeloudis A., Bombardelli F., Jha S., Stoesser T.
Fluids scimago Q2 wos Q3 Open Access , 
2017-04-19,  citations by CoLab: 156 ,  PDF, 

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