Tatyana Lyubimova, Anatoly Lepikhin, Yanina Parshakova, Vadim Kolchanov, Carlo Gualtieri, et al.. A Numerical Study of the Influence of Channel-Scale Secondary Circulation on Mixing Processes Downstream of River Junctions. Water, MDPI, 2020, 12 (11), pp.2969. ⟨10.3390/w12112969⟩. ⟨hal-02989736⟩ Plus de détails...
A rapid downstream weakening of the processes that drive the intensity of transverse mixing at the confluence of large rivers has been identified in the literature and attributed to the progressive reduction in channel scale secondary circulation and shear-driven mixing with distance downstream from the junction. These processes are investigated in this paper using a three-dimensional computation of the Reynolds averaged Navier Stokes equations combined with a Reynolds stress turbulence model for the confluence of the Kama and Vishera rivers in the Russian Urals. Simulations were carried out for three different configurations: an idealized planform with a rectangular cross-section (R), the natural planform with a rectangular cross-section (P), and the natural planform with the measured bathymetry (N), each one for three different discharge ratios. Results show that in the idealized configuration (R), the initial vortices that form due to channel-scale pressure gradients decline rapidly with distance downstream. Mixing is slow and incomplete at more than 10 multiples of channel width downstream from the junction corner. However, when the natural planform and bathymetry are introduced (N), rates of mixing increase dramatically at the junction corner and are maintained with distance downstream. Comparison with the P case suggests that it is the bathymetry that drives the most rapid mixing and notably when the discharge ratio is such that a single channel-scale vortex develops aided by curvature in the post junction channel. This effect is strongest when the discharge of the tributary that has the same direction of curvature as the post junction channel is greatest. A comprehensive set of field data are required to test this conclusion. If it holds, theoretical models of mixing processes in rivers will need to take into account the effects of bathymetry upon the interaction between river discharge ratio, secondary circulation development, and mixing rates.
Tatyana Lyubimova, Anatoly Lepikhin, Yanina Parshakova, Vadim Kolchanov, Carlo Gualtieri, et al.. A Numerical Study of the Influence of Channel-Scale Secondary Circulation on Mixing Processes Downstream of River Junctions. Water, MDPI, 2020, 12 (11), pp.2969. ⟨10.3390/w12112969⟩. ⟨hal-02989736⟩
Elena Alekseenko, Bernard Roux. Risk of wind-driven resuspension and transport of contaminated sediments in a narrow marine channel confluencing a wide lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2020, 237, pp.106649. ⟨10.1016/j.ecss.2020.106649⟩. ⟨hal-02524483⟩ Plus de détails...
Elena Alekseenko, Bernard Roux. Risk of wind-driven resuspension and transport of contaminated sediments in a narrow marine channel confluencing a wide lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2020, 237, pp.106649. ⟨10.1016/j.ecss.2020.106649⟩. ⟨hal-02524483⟩
T. Lyubimova, A. Lepikhin, Ya. Parshakova, C. Gualtieri, S. Lane, et al.. Influence of Hydrodynamic Regimes on Mixing of Waters of Confluent Rivers. Journal of Applied Mechanics and Technical Physics, Springer Verlag, 2020, 60 (7), pp.1220-1227. ⟨10.1134/S0021894419070083⟩. ⟨hal-02989585⟩ Plus de détails...
At present, a significant weakening of the intensity of transverse mixing at the confluence of large rivers, which is observed in a number of cases, is widely discussed. Since the observed features of the confluence of large watercourses are not only of research interest but also of significant economic importance associated with the characteristics of water management at these water bodies, a large number of works are devoted to their study. Water resources management requires measures for the organization of water use which can be rational only under the understanding of processes occurring in water basins. To explain the phenomenon of suppression of the transverse mixing, which is interesting and important from the point of view of ecology, a wide range of hypotheses is proposed, up to the negation of turbulence in rivers. One of the possible mechanisms for explaining the suppression of transversal mixing can be the presence of transverse circulation manifesting itself as Prandtl’s secondary flows of the second kind. The characteristic velocity of these circulation flows is very small and difficult to measure directly by instruments; however, in our opinion, they can significantly complicate the transverse mixing at the confluence. The proposed hypothesis is tested in computational experiments in the framework of the three-dimensional formulation for dimensions of a real water object at the mouth of the Vishera River where it meets the Kama. Calculations demonstrate that, at sufficiently large flow rates, the two waters practically do not mix in the horizontal direction throughout the depth over long distances from the confluence. It has been found that a two-vortex flow is formed downstream the confluence, which just attenuates the mixing; the fluid motion in the vortices is such that, near the free surface, the fluid moves from the banks to the middle of the riverbed.
T. Lyubimova, A. Lepikhin, Ya. Parshakova, C. Gualtieri, S. Lane, et al.. Influence of Hydrodynamic Regimes on Mixing of Waters of Confluent Rivers. Journal of Applied Mechanics and Technical Physics, Springer Verlag, 2020, 60 (7), pp.1220-1227. ⟨10.1134/S0021894419070083⟩. ⟨hal-02989585⟩
Journal: Journal of Applied Mechanics and Technical Physics
E. Alekseenko, Bernard Roux. Contribution to remediation of brackish lagoon: 3D simulation of salinity, bottom currents and resuspension of bottom sediments by strong winds. Estuarine, Coastal and Shelf Science, Elsevier, 2019, 216, pp.27-37. ⟨10.1016/j.ecss.2018.05.021⟩. ⟨hal-01813824⟩ Plus de détails...
This work concerns the modelling and numerical simulation of the 3D salinity and current distribution in a very shallow Mediterranean lagoon subject to strong winds which create intensive resuspension of polluted bottom sediments. We consider wind speeds of 10 m/s and 20 m/s in the two dominant wind directions (N-NW and S-SE). This study is made for different scenarios of flow exchanges with the surrounding hydrosystems: a brackish lagoon on the North (the Etang de Berre), the Cadiere River on the East, and a brackish channel on the South (the Rove channel). The bottom shear stress (BSS) are compared to the BBS threshold given in the literature in terms of the bottom roughness. It permits to determine which kind of bottom sediments (muds and sands) will be resuspended by each wind. The bottom currents permit to predict in which direction the suspended sediments will be moved and where are the sedimentary deposit zones. It provides a guide for the specialists of remediation of the lagoon for a mechanical extraction of sediments in such zones. In addition, numerical experiments have been performed to understand how the salinity distribution depends on the flow exchanges with the two brackish surrounding hydrosystems. This new knowledge will permit the owner of this lagoon to know how to maintain efficiently the level of salinity in the suitable range.
E. Alekseenko, Bernard Roux. Contribution to remediation of brackish lagoon: 3D simulation of salinity, bottom currents and resuspension of bottom sediments by strong winds. Estuarine, Coastal and Shelf Science, Elsevier, 2019, 216, pp.27-37. ⟨10.1016/j.ecss.2018.05.021⟩. ⟨hal-01813824⟩
E. Alekseenko, Bernard Roux. Wind effect on bottom shear stress, erosion and redeposition on Zostera noltei restoration in a coastal lagoon; part 2. Estuarine, Coastal and Shelf Science, Elsevier, 2019, 216, pp.14-26. ⟨10.1016/j.ecss.2018.05.022⟩. ⟨hal-01813834⟩ Plus de détails...
E. Alekseenko, Bernard Roux. Wind effect on bottom shear stress, erosion and redeposition on Zostera noltei restoration in a coastal lagoon; part 2. Estuarine, Coastal and Shelf Science, Elsevier, 2019, 216, pp.14-26. ⟨10.1016/j.ecss.2018.05.022⟩. ⟨hal-01813834⟩
E. Alekseenko, Bernard Roux. Numerical simulation of the wind influence on bottom shear stress and salinity fields in areas of Zostera noltei replanting in a Mediterranean coastal lagoon. Progress in Oceanography, Elsevier, 2018, 163, pp.147-160. ⟨10.1016/j.pocean.2017.05.001⟩. ⟨hal-02111578⟩ Plus de détails...
The paper concerns the numerical simulation of the wind influence on bottom shear stress and salinity fields in a semi-enclosed coastal lagoon (Etang de Berre) which is connected to the Mediterranean through a long and narrow channel (called Caronte). Two different scenarios are considered. The first scenario (scen.#1), starting with a homogeneous salinity of S = 20 PSU and without wind forcing, studies a stratification process under the influence of a periodic seawater inflow and a strong freshwater inflow from a hydropower plant (250 m 3 /s). Then, in the second scenario (scen.#2), we study how a strong wind of 80 km/h can destroy the haline stratification obtained at the end of scen.#1. The MARS3D numerical model is used to analyze the 3D current and salinity distribution induced by these three meteorological, oceanic and anthropogenic forcings in this lagoon and in the Caronte channel. The main goal is to determine the bottom shear stress (BSS) in the nearshore areas of Zostera noltei replanting, and to compare it with the threshold for erosion of the bottom sediments for different bottom roughness parameters. The most interesting results concern the four nearshore replanting areas; two are situated on the eastern side of EB and two on the western side. The results of scen.#2 show that all these areas are subject to a downwind coastal jet. The destratification process is very beneficial; salinity always remains greater than 12 PSU for a N-NW wind of 80 km/h and a hydropower runoff of 250 m 3 /s. Concerning BSS, it presents a maximum near the shoreline and decreases along transects perpendicular to the shoreline. There exists a zone, parallel to the shoreline, where BSS presents a minimum (where BSS = 0). When comparing the BSS value at the four control points with the critical value, BSS cr , at which the sediment mobility would occur, we see that for the smaller bottom roughness values (ranging from z 0 = 3.5 Â 10 À4 mm, to 3.5 Â 10 À2 mm) BSS largely surpasses this critical value. For a N-NW wind speed of 40 km/h (which is blowing for around 100 days per year), BSS still largely surpasses BSS cr-at least for the silt sediments (ranging from z 0 = 3.5 Â 10 À4 mm, to 3.5 Â 10 À3 mm). This confirms the possibility that the coastal jet could be a stressor for SAV replanting.
E. Alekseenko, Bernard Roux. Numerical simulation of the wind influence on bottom shear stress and salinity fields in areas of Zostera noltei replanting in a Mediterranean coastal lagoon. Progress in Oceanography, Elsevier, 2018, 163, pp.147-160. ⟨10.1016/j.pocean.2017.05.001⟩. ⟨hal-02111578⟩
T.P. Lyubimova, A.P. Lepikhin, Y.N. Parshakova, C. Gualtieri, S.N. Lane, et al.. Influence of hydrodynamic regimes on mixing of waters of confluent rivers. Computational Continuum Mechanics, 2018, 11 (3), pp.354-361. ⟨10.7242/1999-6691/2018.11.3.26⟩. ⟨hal-02989643⟩ Plus de détails...
Alekseenko Elena, Bernard Roux. Submerged Aquatic Vegetation Restoration in Brackish Ecosystems Subject to Strong Winds and Coastal Jets. Oceanography & Fisheries Open access Journal, 2017, 2 (4), pp.555595. ⟨10.19080/OFOAJ.2017.02.555595⟩. ⟨hal-01813859⟩ Plus de détails...
The bottom shear stress (BSS) in a windy Mediterranean lagoon has been carefully investigated through numerical modelling. BSS maps have been obtained for the entire lagoon. The aim is to compare BSS with its critical value in the near shoreareas selected for SAV replanting which are subject to downwind coastal jets.
Alekseenko Elena, Bernard Roux. Submerged Aquatic Vegetation Restoration in Brackish Ecosystems Subject to Strong Winds and Coastal Jets. Oceanography & Fisheries Open access Journal, 2017, 2 (4), pp.555595. ⟨10.19080/OFOAJ.2017.02.555595⟩. ⟨hal-01813859⟩
Journal: Oceanography & Fisheries Open access Journal
E Alekseenko, B Roux, D Fougere, Paul G. Chen. The effect of wind induced bottom shear stress and salinity on Zostera noltii replanting in a Mediterranean coastal lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2017, 187, pp.293-305. ⟨10.1016/j.ecss.2017.01.010⟩. ⟨hal-01453377⟩ Plus de détails...
The paper concerns the wind influence on bottom shear stress and salinity levels in a Mediterranean semi-enclosed coastal lagoon (Etang de Berre), with respect to a replanting program of Zostera noltii . The MARS3D numerical model is used to analyze the 3D current, salinity and temperature distribution induced by three meteorological, oceanic and anthropogenic forcings in this lagoon. The numerical model has been carefully validated by comparison with daily observations of the vertical salinity and temperature profiles at three mooring stations, for one year. Then, two modelling scenarios are considered. The first scenario (scen.## 1), starting with an homogeneous salinity of S = 20 PSU and without wind forcing, studies a stratification process under the influence of a periodic seawater inflow and a strong freshwater inflow from an hydropower plant (250 m3/s). Then, in the second scenario (scen.## 2), we study how a strong wind of 80 km/h can mix the haline stratification obtained at the end of scen.## 1. The most interesting results concern four nearshore replanting areas; two are situated on the eastern side of EB and two on the western side. The results of scen.## 2 show that all these areas are subject to a downwind coastal jet. Concerning bottom salinity, the destratification process is very beneficial; it always remains greater than 12 PSU for a N-NW wind of 80 km/h and an hydropower runoff of 250 m3/s. Special attention is devoted to the bottom shear stress (BSS) for different values of the bottom roughness parameter (for gravels, sands and silts), and to the bottom salinity. Concerning BSS, it presents a maximum near the shoreline and decreases along transects perpendicular to the shoreline. There exists a zone, parallel to the shoreline, where BSS presents a minimum (close to zero). When comparing the BSS value at the four replanting areas with the critical value, BSScr, at which the sediment mobility would occur, we see that for the smaller roughness values (ranging from z0 = 3.5 × 10-4 mm, to 3.5 × 10-2 mm) BSS largely surpasses this critical value. For a N-NW wind speed of 40 km/h (which is blowing for around 100 days per year), BSS still largely surpasses BSScr - at least for the silt sediments (ranging from z0 = 3.5 × 10-4 mm, to 3.5 × 10-3 mm). This confirms the possibility that the coastal jet could generate sediment mobility which could have a negative impact for SAV replanting.
E Alekseenko, B Roux, D Fougere, Paul G. Chen. The effect of wind induced bottom shear stress and salinity on Zostera noltii replanting in a Mediterranean coastal lagoon. Estuarine, Coastal and Shelf Science, Elsevier, 2017, 187, pp.293-305. ⟨10.1016/j.ecss.2017.01.010⟩. ⟨hal-01453377⟩
Elena Alekseenko, Bernard Roux, Anton Sukhinov, Richard Kotarba, Dominique Fougere. Nonlinear hydrodynamics in a Mediterranean lagoon. Nonlinear Processes in Geophysics, European Geosciences Union (EGU), 2013, 20 (2), pp.189-198. ⟨10.5194/npg-20-189-2013⟩. ⟨hal-01464721⟩ Plus de détails...
The paper addresses the application of the nonlinear hydrodynamics model (RANS (Reynolds-averaged Navier-Stokes) equations) in a wide semi-enclosed Mediterranean lagoon (Berre lagoon), considering three ă natural forcing functions, i.e., sea tide propagating through a long narrow channel, wind and runoff. Main attention is focused to characteristic velocities (at free surface and bottom) and to free surface elevation associated to each of these three mechanisms, with special attention to the nearshore areas (i.e., in shallow water). The most interesting result concerns wind effects which, due to Berre lagoon bathymetry, give rise to downwind coastal jets, alongshore, in shallow water areas. Such coastal jets were never mentioned before in Berre lagoon literature.
Elena Alekseenko, Bernard Roux, Anton Sukhinov, Richard Kotarba, Dominique Fougere. Nonlinear hydrodynamics in a Mediterranean lagoon. Nonlinear Processes in Geophysics, European Geosciences Union (EGU), 2013, 20 (2), pp.189-198. ⟨10.5194/npg-20-189-2013⟩. ⟨hal-01464721⟩
Tatyana Lyubimova, Bernard Roux, Shunlong Luo, Ya. N Parshakova, Natalya Shumilova. Modeling of the near-field distribution of pollutants coming from a ă coastal outfall. Nonlinear Processes in Geophysics, European Geosciences Union (EGU), 2013, 20 (2), pp.257-266. ⟨10.5194/npg-20-257-2013⟩. ⟨hal-01464728⟩ Plus de détails...
The present study concerns the 3-D distribution of pollutants emitted ă from a coastal outfall in the presence of strong sea currents. The ă problem is solved using the nonlinear Reynolds-averaged Navier-Stokes ă equations in the framework of the k-epsilon model. The constants of the ă logarithmic law for the vertical velocity profile in the bottom boundary ă layer are obtained by processing experimental data from acoustic Doppler ă current profilers (ADCPs). The near-field distribution of pollutants at ă different distances from the diffuser is obtained in terms of the ă ambient flow velocity (steady or with tidal effect) and outfall ă discharge characteristics. It is shown that even in the case where the ă effluent density is substantially lower than the ambient sea water ă density the plume can impact the seabed, creating a risk of pollution of ă removable bottom sediments.
Tatyana Lyubimova, Bernard Roux, Shunlong Luo, Ya. N Parshakova, Natalya Shumilova. Modeling of the near-field distribution of pollutants coming from a ă coastal outfall. Nonlinear Processes in Geophysics, European Geosciences Union (EGU), 2013, 20 (2), pp.257-266. ⟨10.5194/npg-20-257-2013⟩. ⟨hal-01464728⟩
D.V. Lyubimov, T. P. Lyubimova, R.V. Skuridin, G. Chen, B. Roux. Numerical investigation of meniscus deformation and flow in an isothermal liquid bridge subject to high-frequency vibrations under zero gravity conditions. Computers and Fluids, Elsevier, 2002, 31, pp.663-682. ⟨10.1016/S0045-7930(01)00078-0⟩. ⟨hal-01307320⟩ Plus de détails...
This paper deals with meniscus deformation and flow in an isothermal liquid bridge maintained between two circular rods, when one rod is subject to axial monochromatic vibrations. It concerns a fundamental aspect of the problem of crystal growth from melt by the floating-zone technique which is often considered in weightlessness conditions. In the absence of vibrations the bridge is cylindrical; but due to vibration the mean shape of the meniscus is no more cylindrical and the meniscus oscillates around this mean shape. Two models are developed. First, we take into account the pulsating deformations of the meniscus (free surface), but we assume that the mean shape of meniscus remains cylindrical (i.e., we neglect the influence of vibration on this mean shape). For this simple case, a solution of the problem for the pulsating meniscus deformations and the pulsating velocity field is found in explicit form. For the mean flow, the problem is solved numerically by a finite-difference method. The calculations demonstrate the contribution of two basic mechanisms of mean flow generation due to vibrations, related to the generation of mean vorticity in the viscous boundary layer near the rigid boundaries and surface-wave propagation at a free surface. The intensity of the mean flow induced by surface waves is found to be sharply increasing when the vibration frequency approaches the resonance values that are determined from the explicit form of the solution of pulsation problem. In the second model, we take into account both pulsating and mean deformations of the meniscus. The governing equations for the potential of pulsating velocity and mean velocity, and for the pressure, are solved by using a finite-difference method and a boundary-fitted curvilinear coordinate system fitting the free surface.
D.V. Lyubimov, T. P. Lyubimova, R.V. Skuridin, G. Chen, B. Roux. Numerical investigation of meniscus deformation and flow in an isothermal liquid bridge subject to high-frequency vibrations under zero gravity conditions. Computers and Fluids, Elsevier, 2002, 31, pp.663-682. ⟨10.1016/S0045-7930(01)00078-0⟩. ⟨hal-01307320⟩
Dv Lyubimov, Tp Lyubimova, Sofiane Meradji, Bernard Roux, D Beysens, et al.. 2D unsteady motion and deformation of a gaseous bubble in a vibrating liquid at zero gravity. Journal de Physique IV Proceedings, EDP Sciences, 2001, 11 (PR6), pp.Pr6--91. ⟨hal-01291556⟩ Plus de détails...
Dv Lyubimov, Tp Lyubimova, Sofiane Meradji, Bernard Roux, D Beysens, et al.. 2D unsteady motion and deformation of a gaseous bubble in a vibrating liquid at zero gravity. Journal de Physique IV Proceedings, EDP Sciences, 2001, 11 (PR6), pp.Pr6--91. ⟨hal-01291556⟩
Sofiane Meradji, Tp Lyubimova, Dv Lyubimov, B Roux. Numerical simulation of a liquid drop freely oscillating. Crystal Research and Technology, Wiley-VCH Verlag, 2001, 36 (7), pp.729--744. ⟨hal-01291555⟩ Plus de détails...
Sofiane Meradji, Tp Lyubimova, Dv Lyubimov, B Roux. Numerical simulation of a liquid drop freely oscillating. Crystal Research and Technology, Wiley-VCH Verlag, 2001, 36 (7), pp.729--744. ⟨hal-01291555⟩
Dv Lyubimov, Tp Lyubimova, Sofiane Meradji, B Roux. Vibrational control of crystal growth from liquid phase. Journal of Crystal Growth, Elsevier, 1997, 180 (3), pp.648--659. ⟨hal-01291557⟩ Plus de détails...
Dv Lyubimov, Tp Lyubimova, Sofiane Meradji, B Roux. Vibrational control of crystal growth from liquid phase. Journal of Crystal Growth, Elsevier, 1997, 180 (3), pp.648--659. ⟨hal-01291557⟩
