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Thorsten Stoesser
Department of Civil, Environmental and Geomatic Engineering, University College London, Gower Street, London, WC1E 6BT, UK

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Journal article
Published: 26 November 2020 in Applied Ocean Research
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For the purpose of this paper, the in-house large-eddy simulation code, Hydro3D, is refined to study wave structure interaction. First of all, the code is used to develop a numerical wave tank capable of simulating accurately the generation, progression and damping of solitary waves in a tank. Then, Hydro3d is employed to simulate a previous laboratory experiment of a wave propagating over an infinitely wide flat plate. The code’s accuracy is validated by comparing computed waterlevels and hydrodynamic forces on the plate with measured data for which good agreement is found for a number of conditions (i.e. varying wave steepness or plate submergence, respectively). Then the study is extended to investigate three-dimensional effects for which the infinitely wide plate is replaced by a finite square plate. It is found that the pressure difference between the lower and upper side of the plate drives a span-wise flow and creates unique flow structures and water-surface fluctuations near the plate due to the three-dimensionality of the problem. A further three-dimensional study is conducted for which the finite plate is fixed at an angle of attack in respect to the incident wave and variations in hydrodynamic forces and free-surface elevations are computed. Both vertical and horizontal forces are reduced when the plate is fixed at 45∘ degrees and minor water-level fluctuations appear, reflecting the pattern of the rotational flow near the plate edges. Plots of the velocity vectors, swirl-strength, pressure and wave elevation and acting forces reveal significant differences between an infinitely wide and a finite square plate subjected to a solitary wave.

ACS Style

Aristos Christou; Zhihua Xie; Thorsten Stoesser; Pablo Ouro. Propagation of a solitary wave over a finite submerged thin plate. Applied Ocean Research 2020, 106, 102425 .

AMA Style

Aristos Christou, Zhihua Xie, Thorsten Stoesser, Pablo Ouro. Propagation of a solitary wave over a finite submerged thin plate. Applied Ocean Research. 2020; 106 ():102425.

Chicago/Turabian Style

Aristos Christou; Zhihua Xie; Thorsten Stoesser; Pablo Ouro. 2020. "Propagation of a solitary wave over a finite submerged thin plate." Applied Ocean Research 106, no. : 102425.

Journal article
Published: 12 May 2020 in Journal of Computational Physics
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A three-dimensional Cartesian cut-cell method for the large-eddy simulation of two-phase flows with moving bodies is presented in this study, which combines a volume-of-fluid method to capture the air-water interface and a moving body algorithm on a stationary, non-uniform, staggered, Cartesian grid. The filtered Navier–Stokes equations are discretised using the finite volume method with the PISO algorithm for velocity-pressure coupling and the dynamic Smagorinsky subgrid-scale model is employed to compute the effect of the unresolved (subgrid) scales of turbulence on the large scales. In the present study, the small cut-cells are unmodified and due to the use of an implicit time integration no instabilities occur during the computations. The versatility and robustness of the present two-phase flow model is illustrated via various two- and three-dimensional flow problems with fixed/moving bodies, such as dambreak flows with and without a square cylinder, a moving cylinder in a quiescent fluid, dambreak flow over a wet bed with a moving gate, water entry and exist of a circular cylinder, and landside-generated waves. Good agreement is obtained between the numerical results and the corresponding experimental measurements.

ACS Style

Zhihua Xie; Thorsten Stoesser. A three-dimensional Cartesian cut-cell/volume-of-fluid method for two-phase flows with moving bodies. Journal of Computational Physics 2020, 416, 109536 .

AMA Style

Zhihua Xie, Thorsten Stoesser. A three-dimensional Cartesian cut-cell/volume-of-fluid method for two-phase flows with moving bodies. Journal of Computational Physics. 2020; 416 ():109536.

Chicago/Turabian Style

Zhihua Xie; Thorsten Stoesser. 2020. "A three-dimensional Cartesian cut-cell/volume-of-fluid method for two-phase flows with moving bodies." Journal of Computational Physics 416, no. : 109536.

Journal article
Published: 10 March 2020 in Energy Conversion and Management
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In this paper we report on the design and testing of a novel vertical axis wind turbine (VAWT) system. The system consists of two counter-rotating VAWT rotors and a deflector that is placed between the two rotors. The system’s performance is first quantified in wind tunnel experiments and subsequently, three-dimensional computational fluid dynamics (CFD) simulations are performed to complement the experiments and to provide the fluid mechanical details. It is found that the deflector has a significant effect (power-increasing) on the power output of the two rotors, which is related to the rotational direction of the two rotors. With the addition of the deflector, the twin VAWT is able to harness up to 38.6% more wind energy compared with the system without deflector. The analysis of the CFD-produced flow field showed that the increased power output is the result of local acceleration of the fluid and local blockage effect of the deflector. The use of a deflector is found to be a simple and practical approach to improve the performance of twin VAWT system.

ACS Style

Yichen Jiang; Peidong Zhao; Thorsten Stoesser; Kun Wang; Li Zou. Experimental and numerical investigation of twin vertical axis wind turbines with a deflector. Energy Conversion and Management 2020, 209, 112588 .

AMA Style

Yichen Jiang, Peidong Zhao, Thorsten Stoesser, Kun Wang, Li Zou. Experimental and numerical investigation of twin vertical axis wind turbines with a deflector. Energy Conversion and Management. 2020; 209 ():112588.

Chicago/Turabian Style

Yichen Jiang; Peidong Zhao; Thorsten Stoesser; Kun Wang; Li Zou. 2020. "Experimental and numerical investigation of twin vertical axis wind turbines with a deflector." Energy Conversion and Management 209, no. : 112588.

Journal article
Published: 12 December 2019 in Energies
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An actuator surface model (ASM) to be employed to simulate the effect of a vertical axis turbine on the hydrodynamics in its vicinity, particularly its wake is introduced. The advantage of the newly developed ASM is that it can represent the complex flow inside the vertical axis turbine’s perimeter reasonably well, and hence, is able to predict, with a satisfying degree of accuracy, the turbine’s near-wake, with a low computational cost. The ASM appears to overcome the inadequacy of actuator line models to account for the flow blockage of the rotor blades when they are on the up-stream side of the revolution, because the ASM uses a surface instead of a line to represent the blade. The ASM was used on a series of test cases to prove its validity, demonstrating that first order flow statistics—in our study, profiles of the stream-wise velocity—in the turbine’s vicinity, can be produced with reasonable accuracy. The prediction of second order statistics, here in the form of the turbulent kinetic energy (TKE), exhibited dependence on the chosen grid; the finer the grid, the better the match between measured and computed TKE profiles.

ACS Style

Lucy Massie; Pablo Ouro; Thorsten Stoesser; Qianyu Luo. An Actuator Surface Model to Simulate Vertical Axis Turbines. Energies 2019, 12, 4741 .

AMA Style

Lucy Massie, Pablo Ouro, Thorsten Stoesser, Qianyu Luo. An Actuator Surface Model to Simulate Vertical Axis Turbines. Energies. 2019; 12 (24):4741.

Chicago/Turabian Style

Lucy Massie; Pablo Ouro; Thorsten Stoesser; Qianyu Luo. 2019. "An Actuator Surface Model to Simulate Vertical Axis Turbines." Energies 12, no. 24: 4741.

Journal article
Published: 05 September 2019 in Water Resources Research
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ACS Style

Yiqing Gong; Thorsten Stoesser; Jingqiao Mao; Richard McSherry. LES of Flow Through and Around a Finite Patch of Thin Plates. Water Resources Research 2019, 55, 7587 -7605.

AMA Style

Yiqing Gong, Thorsten Stoesser, Jingqiao Mao, Richard McSherry. LES of Flow Through and Around a Finite Patch of Thin Plates. Water Resources Research. 2019; 55 (9):7587-7605.

Chicago/Turabian Style

Yiqing Gong; Thorsten Stoesser; Jingqiao Mao; Richard McSherry. 2019. "LES of Flow Through and Around a Finite Patch of Thin Plates." Water Resources Research 55, no. 9: 7587-7605.

Journal article
Published: 30 November 2018 in Geosciences
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Near-bed and pore space turbulent flows are beginning to be understood using new technologies and advances in direct numerical simulation (DNS) and large-eddy simulation (LES) techniques. However, the riverbed geometry that is used in many computational studies remains overly simplistic. Thus, this study presents the development of an artificial representation of a gravel riverbed matrix, and the assessment of how well it approximates a natural riverbed. A physical model of a gravel riverbed matrix that was 120 mm deep, 300 mm wide, and 2.048 m long was manufactured from cast acrylic. Additionally, a numerical approximation of the physical model was created and used for analysis. The pore matrix of the artificial riverbed was found to be comparable to that of a natural gravel riverbed in terms of its porosity and void ratio. The diameters of the artificial riverbed’s surface particles were found to vary less, with fewer irregularities, than those found for natural gravel riverbeds; yet, they were normally distributed similarly to natural riverbeds. A power spectral density function showed that the artificial riverbed exhibited a degree of roughness that was much lower than that found in nature. Thus, the hydraulic resistance and friction factor will both be lower than desired. These findings suggest that the novel methods that have been developed in this study can offer both the physical and numerical approximation of a gravel bed surface that is comparable to a natural gravel riverbed with low surface roughness, reduced particle size variance, and typical particle distribution and porosity.

ACS Style

Alex Stubbs; Thorsten Stoesser; Bettina Bockelmann-Evans. Developing an Approximation of a Natural, Rough Gravel Riverbed Both Physically and Numerically. Geosciences 2018, 8, 449 .

AMA Style

Alex Stubbs, Thorsten Stoesser, Bettina Bockelmann-Evans. Developing an Approximation of a Natural, Rough Gravel Riverbed Both Physically and Numerically. Geosciences. 2018; 8 (12):449.

Chicago/Turabian Style

Alex Stubbs; Thorsten Stoesser; Bettina Bockelmann-Evans. 2018. "Developing an Approximation of a Natural, Rough Gravel Riverbed Both Physically and Numerically." Geosciences 8, no. 12: 449.

Article
Published: 12 September 2018 in Flow, Turbulence and Combustion
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A large-eddy simulation (LES) of a laboratory-scale horizontal axis tidal stream turbine operating over an irregular bathymetry in the form of dunes is performed. The Reynolds number based on the approach velocity and the chord length of the turbine blades is approximately 60,000. The simulated turbine is a 1:30 scale model of a full-scale prototype and both turbines operate at very similar tip-speed ratio of λ ≈ 3. The simulations provide quantitative evidence of the effect of seabed-induced turbulence on the instantaneous performance and structural loadings of the turbine revealing how large-scale, energetic turbulence structures affect turbine performance and bending moments of the rotor blades. The data analysis shows that wake recovery is notably enhanced in comparison to the same turbine operating above a flat-bed and this is due to the higher turbulence levels generated by the dune. The results demonstrate the need for studying in detail the flow and turbulence characteristics at potential tidal turbine deployment sites and to incorporate observed large-scale velocity and pressure fluctuations into the structural design of the turbines.

ACS Style

Pablo Ouro; Thorsten Stoesser. Impact of Environmental Turbulence on the Performance and Loadings of a Tidal Stream Turbine. Flow, Turbulence and Combustion 2018, 102, 613 -639.

AMA Style

Pablo Ouro, Thorsten Stoesser. Impact of Environmental Turbulence on the Performance and Loadings of a Tidal Stream Turbine. Flow, Turbulence and Combustion. 2018; 102 (3):613-639.

Chicago/Turabian Style

Pablo Ouro; Thorsten Stoesser. 2018. "Impact of Environmental Turbulence on the Performance and Loadings of a Tidal Stream Turbine." Flow, Turbulence and Combustion 102, no. 3: 613-639.

Conference paper
Published: 05 September 2018 in E3S Web of Conferences
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A large-eddy simulation based Eulerian-Lagrangian model is employed to study bubble plumes in an open channel with crossflow. The numerical results are validated with PIV experimental data. Good agreement between simulated and observed velocities is found. The impact of the crossflow on the structure of the plume and the resulting turbulent structures are described.

ACS Style

Elli Mitrou; Bruño Fraga; Thorsten Stoesser. An Eulerian- Lagrangian numerical method to predict bubbly flows. E3S Web of Conferences 2018, 40, 05027 .

AMA Style

Elli Mitrou, Bruño Fraga, Thorsten Stoesser. An Eulerian- Lagrangian numerical method to predict bubbly flows. E3S Web of Conferences. 2018; 40 ():05027.

Chicago/Turabian Style

Elli Mitrou; Bruño Fraga; Thorsten Stoesser. 2018. "An Eulerian- Lagrangian numerical method to predict bubbly flows." E3S Web of Conferences 40, no. : 05027.

Journal article
Published: 26 March 2018 in Journal of Hydraulic Research
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Results from large-eddy simulations and complementary flume experiments of turbulent open channel flows over bed-mounted square bars at intermediate submergence are presented. Scenarios with two bar spacings, corresponding to transitional and k-type roughness, and three flow rates, are investigated. Good agreement is observed between the simulations and the experiments in terms of mean free surface elevations and mean streamwise velocities. Contours of simulated time-averaged streamwise, streamfunction and turbulent kinetic energy are presented and these reveal the effect of the roughness geometry on the water surface response. The analysis of the vertical distribution of the streamwise velocity shows that in the lowest submergence cases no logarithmic layer is present, whereas in the higher submergence cases some evidence of such a layer is observed. For several of the flows moderate to significant water surface deformations are observed, including weak and/or undular hydraulic jumps which affect significantly to the overall streamwise momentum balance. Reynolds shear stress, form-induced stress and form drag are analysed with reference to the momentum balance to assess their contributions to the total hydraulic resistance of these flows. The results show that form-induced stresses are dominant at the water surface and can contribute significantly to the overall drag, but the total resistance in all cases is dominated by form drag due to the presence of the bars.

ACS Style

Richard McSherry; Ken Chua; Thorsten Stoesser; Saad Mulahasan. Free surface flow over square bars at intermediate relative submergence. Journal of Hydraulic Research 2018, 56, 825 -843.

AMA Style

Richard McSherry, Ken Chua, Thorsten Stoesser, Saad Mulahasan. Free surface flow over square bars at intermediate relative submergence. Journal of Hydraulic Research. 2018; 56 (6):825-843.

Chicago/Turabian Style

Richard McSherry; Ken Chua; Thorsten Stoesser; Saad Mulahasan. 2018. "Free surface flow over square bars at intermediate relative submergence." Journal of Hydraulic Research 56, no. 6: 825-843.

Journal article
Published: 13 March 2018 in Journal of Fluids Engineering
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This paper presents large eddy simulations (LESs) of symmetric and asymmetric (cambered) airfoils forced to undergo deep dynamic stall due to a prescribed pitching motion. Experimental data in terms of lift, drag, and moment coefficients are available for the symmetric NACA 0012 airfoil and these are used to validate the LESs. Good agreement between computed and experimentally observed coefficients is found confirming the accuracy of the method. The influence of foil asymmetry on the aerodynamic coefficients is analyzed by subjecting a NACA 4412 airfoil to the same flow and pitching motion conditions. Flow visualizations and analysis of aerodynamic forces allow an understanding and quantification of dynamic stall on both straight and cambered foils. The results confirm that cambered airfoils provide an increased lift-to-drag ratio and a decreased force hysteresis cycle in comparison to their symmetric counterparts. This may translate into increased performance and lower fatigue loads when using cambered airfoils in the design of vertical axis turbines (VATs) operating at low tip-speed ratios.

ACS Style

Pablo Ouro; Thorsten Stoesser; Luis Ramirez. Effect of Blade Cambering on Dynamic Stall in View of Designing Vertical Axis Turbines. Journal of Fluids Engineering 2018, 140, 061104 .

AMA Style

Pablo Ouro, Thorsten Stoesser, Luis Ramirez. Effect of Blade Cambering on Dynamic Stall in View of Designing Vertical Axis Turbines. Journal of Fluids Engineering. 2018; 140 (6):061104.

Chicago/Turabian Style

Pablo Ouro; Thorsten Stoesser; Luis Ramirez. 2018. "Effect of Blade Cambering on Dynamic Stall in View of Designing Vertical Axis Turbines." Journal of Fluids Engineering 140, no. 6: 061104.

Original article
Published: 18 December 2017 in Environmental Fluid Mechanics
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The results of large-eddy simulations of flow and transient solute transport over a backward facing step and through a 180° bend are presented. The simulations are validated successfully in terms of hydrodynamics and tracer transport with experimental velocity data and measured residence time distribution curves confirming the accuracy of the method. The hydrodynamics are characterised by flow separation and subsequent recirculation in vertical and horizontal directions and the solute dispersion process is a direct response to the significant unsteadiness and turbulence in the flow. The turbulence in the system is analysed and quantified in terms of power density spectra and covariance of velocity fluctuations. The injection of an instantaneous passive tracer and its dispersion through the system is simulated. Large-eddy simulations enable the resolution of the instantaneous flow field and it is demonstrated that the instabilities of intermittent large-scale structures play a distinguished role in the solute transport. The advection and diffusion of the scalar is governed by the severe unsteadiness of the flow and this is visualised and quantified. The analysis of the scalar mass transport budget quantifies the mechanisms controlling the turbulent mixing and reveals that the mass flux is dominated by advection.

ACS Style

P. Ouro; B. Fraga; N. Viti; A. Angeloudis; T. Stoesser; C. Gualtieri. Instantaneous transport of a passive scalar in a turbulent separated flow. Environmental Fluid Mechanics 2017, 18, 487 -513.

AMA Style

P. Ouro, B. Fraga, N. Viti, A. Angeloudis, T. Stoesser, C. Gualtieri. Instantaneous transport of a passive scalar in a turbulent separated flow. Environmental Fluid Mechanics. 2017; 18 (2):487-513.

Chicago/Turabian Style

P. Ouro; B. Fraga; N. Viti; A. Angeloudis; T. Stoesser; C. Gualtieri. 2017. "Instantaneous transport of a passive scalar in a turbulent separated flow." Environmental Fluid Mechanics 18, no. 2: 487-513.

Article
Published: 14 December 2017 in Journal of Geophysical Research: Earth Surface
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In this paper the effects of boulder concentration on hydrodynamics and local and reach-averaged sediment transport properties with a flow over submerged boulder arrays are investigated. Four numerical simulations are performed in which the boulders' streamwise spacings are varied. Statistics of near-bed velocity, Reynolds shear stresses, and turbulent events are collected and used to predict bed load transport rates. The results demonstrate that the presence of boulders at various interboulder spacings altered the flow field in their vicinity causing (1) flow deceleration, wake formation, and vortex shedding; (2) enhanced outward and inward interaction turbulence events downstream of the boulders; and (3) a redistribution of the local bed shear stress around the boulder consisting of pockets of high and low bed shear stresses. The spatial variety of the predicted bed load transport rate qs based on local bed shear stress is visualized and is shown to depend greatly on the boulder concentration. Quantitative bed load transport calculations demonstrate that the reach-averaged bed load transport rate may be overestimated by up to 25 times when including the form-drag-generated shear stress of the immobile boulders in the chosen bed load formula. Further, the reach-averaged bed load transport rate may be underestimated by 11% if the local variability of the bed shear stress is not accounted for. Finally, it is shown that for the small-spaced boulder array, the bed load transport rates should no longer be predicted using a normal distribution with standard deviation of the shear stress distribution σ.

ACS Style

H. W. Fang; Y. Liu; T. Stoesser. Influence of Boulder Concentration on Turbulence and Sediment Transport in Open‐Channel Flow Over Submerged Boulders. Journal of Geophysical Research: Earth Surface 2017, 122, 2392 -2410.

AMA Style

H. W. Fang, Y. Liu, T. Stoesser. Influence of Boulder Concentration on Turbulence and Sediment Transport in Open‐Channel Flow Over Submerged Boulders. Journal of Geophysical Research: Earth Surface. 2017; 122 (12):2392-2410.

Chicago/Turabian Style

H. W. Fang; Y. Liu; T. Stoesser. 2017. "Influence of Boulder Concentration on Turbulence and Sediment Transport in Open‐Channel Flow Over Submerged Boulders." Journal of Geophysical Research: Earth Surface 122, no. 12: 2392-2410.

Journal article
Published: 01 November 2017 in Journal of Irrigation and Drainage Engineering
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ACS Style

Saad Mulahasan; Thorsten Stoesser; Richard McSherry. Effect of Floodplain Obstructions on the Discharge Conveyance Capacity of Compound Channels. Journal of Irrigation and Drainage Engineering 2017, 143, 04017045 .

AMA Style

Saad Mulahasan, Thorsten Stoesser, Richard McSherry. Effect of Floodplain Obstructions on the Discharge Conveyance Capacity of Compound Channels. Journal of Irrigation and Drainage Engineering. 2017; 143 (11):04017045.

Chicago/Turabian Style

Saad Mulahasan; Thorsten Stoesser; Richard McSherry. 2017. "Effect of Floodplain Obstructions on the Discharge Conveyance Capacity of Compound Channels." Journal of Irrigation and Drainage Engineering 143, no. 11: 04017045.

Journal article
Published: 01 July 2017 in Computers & Fluids
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ACS Style

Pablo Ouro; Thorsten Stoesser. An immersed boundary-based large-eddy simulation approach to predict the performance of vertical axis tidal turbines. Computers & Fluids 2017, 152, 74 -87.

AMA Style

Pablo Ouro, Thorsten Stoesser. An immersed boundary-based large-eddy simulation approach to predict the performance of vertical axis tidal turbines. Computers & Fluids. 2017; 152 ():74-87.

Chicago/Turabian Style

Pablo Ouro; Thorsten Stoesser. 2017. "An immersed boundary-based large-eddy simulation approach to predict the performance of vertical axis tidal turbines." Computers & Fluids 152, no. : 74-87.

Journal article
Published: 01 May 2017 in Journal of Fluids and Structures
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ACS Style

Pablo Ouro; Magnus Harrold; Thorsten Stoesser; Peter Bromley. Hydrodynamic loadings on a horizontal axis tidal turbine prototype. Journal of Fluids and Structures 2017, 71, 78 -95.

AMA Style

Pablo Ouro, Magnus Harrold, Thorsten Stoesser, Peter Bromley. Hydrodynamic loadings on a horizontal axis tidal turbine prototype. Journal of Fluids and Structures. 2017; 71 ():78-95.

Chicago/Turabian Style

Pablo Ouro; Magnus Harrold; Thorsten Stoesser; Peter Bromley. 2017. "Hydrodynamic loadings on a horizontal axis tidal turbine prototype." Journal of Fluids and Structures 71, no. : 78-95.

Review
Published: 19 April 2017 in Fluids
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Computational Fluid Dynamics (CFD) has consolidated as a tool to provide understanding and quantitative information regarding many complex environmental flows. The accuracy and reliability of CFD modelling results oftentimes come under scrutiny because of issues in the implementation of and input data for those simulations. Regarding the input data, if an approach based on the Reynolds-Averaged Navier-Stokes (RANS) equations is applied, the turbulent scalar fluxes are generally estimated by assuming the standard gradient diffusion hypothesis (SGDH), which requires the definition of the turbulent Schmidt number, Sct (the ratio of momentum diffusivity to mass diffusivity in the turbulent flow). However, no universally-accepted values of this parameter have been established or, more importantly, methodologies for its computation have been provided. This paper firstly presents a review of previous studies about Sct in environmental flows, involving both water and air systems. Secondly, three case studies are presented where the key role of a correct parameterization of the turbulent Schmidt number is pointed out. These include: (1) transverse mixing in a shallow water flow; (2) tracer transport in a contact tank; and (3) sediment transport in suspension. An overall picture on the use of the Schmidt number in CFD emerges from the paper.

ACS Style

Carlo Gualtieri; Athanasios Angeloudis; Fabian Bombardelli; Sanjeev Jha; Thorsten Stoesser. On the Values for the Turbulent Schmidt Number in Environmental Flows. Fluids 2017, 2, 17 .

AMA Style

Carlo Gualtieri, Athanasios Angeloudis, Fabian Bombardelli, Sanjeev Jha, Thorsten Stoesser. On the Values for the Turbulent Schmidt Number in Environmental Flows. Fluids. 2017; 2 (2):17.

Chicago/Turabian Style

Carlo Gualtieri; Athanasios Angeloudis; Fabian Bombardelli; Sanjeev Jha; Thorsten Stoesser. 2017. "On the Values for the Turbulent Schmidt Number in Environmental Flows." Fluids 2, no. 2: 17.

Research papers
Published: 03 February 2017 in International Journal of River Basin Management
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Open channel flow through a line of vertically oriented circular rods, designed to represent idealized bankline vegetation, is studied. Bankline vegetation is a common feature in rivers and streams and yet has not received as much attention as fully vegetated flows. Particular focus is placed on the effect of vegetation diameter on the flow resistance which is quantified via a drag coefficient. A large number of laboratory experiments of uniform flow through one-line of vegetation were carried out and drag coefficients were calculated via a momentum balance. Experimentally obtained drag coefficients are then compared to those calculated using a number of empirical expressions that have been proposed in the literature. Good agreement is generally observed. The results show that varying the diameter of the rigid emergent vegetation affects flow resistance, and that the drag coefficient of in-line vegetation exhibits limited sensitivity to the stem Reynolds number.

ACS Style

S. Mulahasan; T. Stoesser. Flow resistance of in-line vegetation in open channel flow. International Journal of River Basin Management 2017, 15, 329 -334.

AMA Style

S. Mulahasan, T. Stoesser. Flow resistance of in-line vegetation in open channel flow. International Journal of River Basin Management. 2017; 15 (3):329-334.

Chicago/Turabian Style

S. Mulahasan; T. Stoesser. 2017. "Flow resistance of in-line vegetation in open channel flow." International Journal of River Basin Management 15, no. 3: 329-334.

Journal article
Published: 01 February 2017 in Journal of Hydrodynamics
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ACS Style

Richard McSherry; Ken V. Chua; Thorsten Stoesser. Large eddy simulation of free-surface flows. Journal of Hydrodynamics 2017, 29, 1 -12.

AMA Style

Richard McSherry, Ken V. Chua, Thorsten Stoesser. Large eddy simulation of free-surface flows. Journal of Hydrodynamics. 2017; 29 (1):1-12.

Chicago/Turabian Style

Richard McSherry; Ken V. Chua; Thorsten Stoesser. 2017. "Large eddy simulation of free-surface flows." Journal of Hydrodynamics 29, no. 1: 1-12.

Proceedings article
Published: 24 June 2016 in River Flow 2016
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ACS Style

Bruño Fraga; Elli Mitrou; Thorsten Stoesser. Large-eddy simulations of bubble plumes with and without crossflow. River Flow 2016 2016, 1 .

AMA Style

Bruño Fraga, Elli Mitrou, Thorsten Stoesser. Large-eddy simulations of bubble plumes with and without crossflow. River Flow 2016. 2016; ():1.

Chicago/Turabian Style

Bruño Fraga; Elli Mitrou; Thorsten Stoesser. 2016. "Large-eddy simulations of bubble plumes with and without crossflow." River Flow 2016 , no. : 1.

Article
Published: 04 June 2016 in Journal of Geophysical Research: Oceans
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A large-eddy simulation based Eulerian-Lagrangian model is employed to quantify the impact of bubble size, diffuser diameter, and gas flow rate on integral properties of bubble plumes, such as the plume's width, centerline velocity, and mass flux. Calculated quantities are compared with experimental data and integral model predictions. Furthermore, the LES data were used to assess the behavior of the entrainment coefficient, the momentum amplification factor, and the bubble-to-momentum spread ratio. It is found that bubble plumes with constant bubble size and smaller diameter behave in accordance with integral plume models. Plumes comprising larger and non-uniform bubble sizes appear to deviate from past observations and model predictions. In multi-diameter bubble plumes, a bubble self-organisation takes place, i.e., small bubbles cluster in the center of the plume whilst large bubbles are found at the periphery of the plume. Multi-diameter bubble plumes also feature a greater entrainment rate than single-size bubble plumes, as well as a higher spread ratio and lower turbulent momentum rate. Once the plume is fully established, the size of the diffuser does not appear to affect integral properties of bubble plumes. However, plume development is affected by the diffuser width, as larger release areas lead to a delayed asymptotic behavior of the plume and consequently to a lower entrainment and higher spread ratio. Finally, the effect of the gas flow rate on the integral plume is studied and is deemed very relevant with regards to most integral plume properties and coefficients. This effect is already fairly well described by integral plume models.

ACS Style

Bruño Fraga; Thorsten Stoesser. Influence of bubble size, diffuser width, and flow rate on the integral behavior of bubble plumes. Journal of Geophysical Research: Oceans 2016, 121, 3887 -3904.

AMA Style

Bruño Fraga, Thorsten Stoesser. Influence of bubble size, diffuser width, and flow rate on the integral behavior of bubble plumes. Journal of Geophysical Research: Oceans. 2016; 121 (6):3887-3904.

Chicago/Turabian Style

Bruño Fraga; Thorsten Stoesser. 2016. "Influence of bubble size, diffuser width, and flow rate on the integral behavior of bubble plumes." Journal of Geophysical Research: Oceans 121, no. 6: 3887-3904.