 Good morning, I'm Francesca Campo Maggiora, a PhD student in F-Science of Flu Mechanic at the University of Trieste. The title of my talk is a large dissimulation on turbulent flu in a sharp meander bed. My presentation is organized as a follow, I started introducing the meandering phenomena in the actual state of art about this fin. Then I described my test case and the numerical model apply. I chose the results and explained the main flu and secondary flu characteristics and the rule of turbulence in this sharp meandering flu. At the end I underlined what is our next goal. What is meandering? Jalini in 1992 defined meandering as a safe induced plane deformation of a stream, which under ideal condition is periodic and symmetrical with respect to an axis axis. This type of flu is highly three-dimensional and the principal features are the formation of region of recirculation, the presence of non-isotropic turbulent stresses and the energetic equivalent vertices, the presence of the internal shear layer and the establishment of a centrifugal secondary flu that deeply inflate the flu behavior. This type of flu is a direct artwork close to the free surface and in work close to the bed. When the bed is erodible, the secondary flu debuts the motion of sediment creating a sequence of points near the inner bank and pull here in SDI outer bank. But when the bed is erodible, a free vortex effect prevail. At the entry of the bed, the flu at the inner bank accelerates relatively to the outer bank and the secondary flu drives a net transfer momentum towards the outer bank. So the trend of high velocity is found near the inner bank and then move towards the outer bank preceding dousely. In summary, we can define the meandering wave evolution as a combination of dousely and outward migration. The numerical simulation of meandering river is a major topic in environmental engineering. The dynamic of meandering has many practical consequences. It affects the bank's ability and the channel navigability. In situ is the subject of a great number of recent experimental theoretical studies. On the numerical side, the investigation of meandering river and the rhythm of dynamic by means of larger dissimulation has found an increasing interest in the recent year. I take with reference the experimental work of blanket. The experimental flu consists of a stray inflow and a stray inflow section, a carved section of 193° and a stray outflow section or over a flat bed. The vertical sidewalls are hydraulically smooth, whereas the bed is hydraulically rough. The fluid is turbulent and subcritical, and in the table are listed the hydraulic and geometric parameters of the simulation and the grid characteristics. We perform a larger dissimulation of an incompressibly fully developed turbulent flow. The subgrid stresses are parameterized by an anti-discosity model, where the dynamic procedure is implied. A wall-area model is used to mimic the solid wall of the channel, whereas for the bed a modified log glow is used. No-slip boundary conditions are imposed on walls, whereas the free surface is treated as a horizontal impermeable rigid lead, where the free-slip conditions are applied. A convective boundary condition is used at the outflow and the influence boundaries are provided by the outflow of the simulation corresponding straight open channel flow using periodic conditions in the stream-ride direction. Now I show the results. In figure the stream of velocity at the free surface and the stream of velocity average the fluid depth, are shown at the free surface. We can observe how the turbulent channel flow enters the band and the secondary flow gives rise to centrifugal secondary fluid cells. So the high velocity are found near the inner bank and then they are moving towards the outer bank. We can observe as the main flow detaches from the inner bank because of the formation of an internal shear layer. For a further investigation of the fluid field I aligned the vertical velocity, the stream of vertical and the transverse velocity in the flow for two sections, one hundred degree section and one hundred degree section for eight different locations of the vertical in the transverse cross section. We can show how the existence of the formation of an internal shear layer near the inner bank due to the strongly curvature of the geometry and has these effects tend to vanish in the downstream part of the bed. At the free surface the vertical vorticity show the flow structure over the key part of the flow. The vertical vorticity show the rotational structure of the secondary flow and we can observe the touch of the boundary shear layer near the inner bank. In figures the vertical velocity are represented for six cross sectional in the flow. We can show an alternating pattern of upwelling and downwelling near the inner bank because of this pattern is associated with the internal shear layer separated from the inner bank. At the outer bank the flow is obviously dominated by downwelling due to the motion of the secondary flow and so the presence of centrifugal forces. The stream v vorticity show the complex structure of the secondary flow. We can show the belt of positive vorticity at the free surface and it identifies the internal shear layer. We can show the major area of negative vorticity so it is the central region cell and the outer bank cell an area of positive vorticity near the outer bank. The result shows that the outer bank is present in the upstream part of the band and then it loses strength proceeding downstream. We know that the bed shear stress is a measure of the force exerted at the bed. When the bed shear stress exceeds the critical value then the motion of the seed event over the bed is initiated. Given the hydraulically roughness of the bed the equation of linear model can be directly applied to obtain the friction velocity. It is based on the velocity vector. In figure the spatial distribution of the friction factor are two. We observe that the friction the highest value of friction are found near the inner bank since in this region the velocity are the highest because of the strongly favored pressure gradient due to the curvature discontinuity and as the proceeding downstream the friction became moderately equally distributed. In figures of Reynolds shear stresses we can show for the stream transverse stresses and a local increase of its value because in this region when the center region cell and the outer bank cell touch but this behavior is not observed in the stream of vertical and the transverse vertical stresses because of the free surface the vertical velocity is equal to zero. For the transverse vertical stress we observe an anti-symmetry along the bisecture format from the corner from the free surface and the outer bank cells whereas the stream of vertical stresses show a clear correlation with the rotational sense of the cross sectional flow and the outer bank cell fully coincide with the an area of negative stream of vertical stresses. We have present turbulent kinetic energy in the upstream part of the curve of the band an eruption of the turbulent kinetic energy of course it progressively increases moving towards the corner of the center region cell and it gains weakens proceeding downstream. The high values are fine near the band in order to provide the turbulence anisotropy and the turbulent efficiency in turbulent stress production the principal stresses and the so-called structural parameter are addressed now. Basically the difference between the principal stresses are defined as a measure of the turbulence anisotropy. The velocity fluctuation near the free surface tend to be zero. That causes the transverse fluctuation to be dominant. As a consequence instead at the outer bank an opposite behavior is observed. As a consequence the turbulence anisotropy is most pronounced at the boundaries. So the peak shows also the increase of turbulent anisotropy at the touch of the center region and the outer bank cells. And so in this year we have a high anisotropy. The structural parameter is defined as the rate of the magnitude of shear stresses and twice the turbulent kinetic energy. It roughly indicates the efficiency in turbulent energy in production of turbulent stress. It indicates we can show an increase value of this parameter at the touch of two mutually control rotating cells and this coincide where the stream-wise transverse stresses are dominant and where the stream of vertical and transverse vertical stresses have a minimum value. So this at the outer bank in the core of the outer bank this behavior is the opposite. So there be it's clear that the outer bank cell itself has an unsafe production of turbulent shear stress in the cross-sectional plane. The carved open channel flow exhibits a transverse inclination of the free surface that's moving proceeding in the band and causes the establishment of centrifugal secondary flow that deeply influence the flow behavior. At the moment this problem is often addressed using the rigidly assumption. And so in this context the super elevation effect is considered to be negligible but it's not true in general. We want to introduce the free surface elevation in the numerical model imposing a hydrostatic pressure variation as a body force in the momentum equation. We carry out a large simulation of meandering flow using a simplified linearized condition of free surface. We allow to the reproduction without the need to move the computational grid. Thank you for the attention. So when the bed is non erodible we have this free vortex effect. And so we observe the high velocity and so the consequence also the friction factor is high near the inner bank and the high of velocity progressively move at the outer band proceeding downstream. But when the bed is erodible the secondary flow creates a sequence of a point bar near the inner bank and so the deposition process is a major at the inner bank but at the outer band the erosion is big and so it creates a sequence of pull here. I use the for simulate the roughness of the bed I use the modified log row consider the roughness of the bed. I try to do without this. Is it necessary that I am going to because you are recording?