M. Brocchini | Università Politecnica delle Marche, Italy (original) (raw)

Papers by M. Brocchini

Research paper thumbnail of Boussinesq modeling of breaking waves: Description of turbulence

Journal of Geophysical Research, 2004

1] Improved turbulent closures for use in fully nonlinear Boussinesq-type models are described he... more 1] Improved turbulent closures for use in fully nonlinear Boussinesq-type models are described here. The approach extends previous works in order to give a more flexible and accurate description of the turbulence due to a breaking wave. Turbulent stresses are handled by means of the Boussinesq hypothesis, and the eddy viscosity is assumed to vary over the water depth according to different laws. The model is described in detail, and its performances are evaluated both against available analytical solutions and against experimental data of regular waves breaking over a slope. The influence of the vertical structure of turbulence under a breaking wave is analyzed by means of four different vertical profiles of eddy viscosity; the differences in terms of hydrodynamic features are also discussed. Among the four selected profiles, two of them (the uniform one and that with uniform eddy viscosity over the top half of the water column which linearly decreases to zero over the lower half ) give better overall performances when compared with experimental data concerning velocity profiles.

Research paper thumbnail of On shallow-water wakes: an analytical study

Journal of Fluid Mechanics, 2006

Analytical solutions for the characteristic scales of a turbulent wake in shallow flows are prese... more Analytical solutions for the characteristic scales of a turbulent wake in shallow flows are presented for two asymptotic cases: in one case, boundary-layer effects dominate whereas in the other, wake effects prevail. The latter case degenerates into the solution valid for an unbounded two-dimensional wake. These solutions show that the momentum deficit decreases exponentially in the longitudinal direction while the transverse velocity profile reveals a wake region characterized by a reduced velocity deficit compared to that of an unbounded wake. When wake-turbulence dominates there is a non-uniform turbulent viscosity in the longitudinal direction. These analytical solutions are compared with experimental data showing good agreement.

Research paper thumbnail of Horizontal mixing of quasi-uniform straight compound channel flows

Journal of Fluid Mechanics, 2010

The generation and evolution of large-scale vortices with vertical axis (macro-vortices) in a str... more The generation and evolution of large-scale vortices with vertical axis (macro-vortices) in a straight compound channel under quasi-uniform flow conditions is investigated. We discuss possible similarities and clear differences with free shear layer flows induced by the meeting of shallow streams of different speeds. An experimental investigation based on particle image velocimetry (PIV) measurements of free-surface velocities forms the basis for an analysis of both the specific features of macro-vortices and of the related mean flow characteristics. Dynamical properties strongly depend on the ratio r h between the main channel flow depth (h * mc ) and the floodplain depth (h * fp ), and three flow classes can be identified. 'Shallow flows' (r h > 3) are dominated by strong shearing and large macro-vortices populating the transition region between the main channel and the floodplains. The mean streamwise velocity induced in 'intermediate flows'

Research paper thumbnail of The effects of flow stratification by non-cohesive sediment on transport in high-energy wave-driven flows

Journal of Fluid Mechanics, 2008

... where u, v are the horizontal components of fluid velocity in the x (cross-shore ... performi... more ... where u, v are the horizontal components of fluid velocity in the x (cross-shore ... performing simulations in which the two-way feedback between sediment load and flow is included ... 5(a) demonstrates that this correlation is strongly due to the quadratic response between sediment ...

Research paper thumbnail of A comparison of two different types of shoreline boundary conditions

Computer Methods in Applied Mechanics and Engineering, 2002

Two different types of shoreline boundary conditions which can be used in either wave-resolving o... more Two different types of shoreline boundary conditions which can be used in either wave-resolving or wave-averaging models of waves and currents propagation in the nearshore are compared here. The two techniques are essentially different: in the first case the velocity of the shoreline is obtained by the momentum equation and the shoreline position is tracked by changing the grid position, while in the other case the velocity of the shoreline is obtained by a modified Riemann solver and the shoreline is defined as an interface between dry and wet fixed grid points. A number of test cases are described to compare the performance of the two techniques. (M. Brocchini). 0045-7825/02/$ -see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 5 -7 8 2 5 ( 0 2 ) 0 0 3 9 2 -4

Research paper thumbnail of Horizontal mixing in compound channels: a global shear layer model?

The horizontal mixing induced by large-scale vortical features (macrovortices) in a straight comp... more The horizontal mixing induced by large-scale vortical features (macrovortices) in a straight compound channel flow are analysed with specific emphasis on possible similarities with those characteristic of a shear layer induced by the meeting of three shallow streams of different speed (shear layer model). An experimental investigation based on PTV and PIV analysis of free surface velocities forms the basis for the following analyses both of specific 1

Research paper thumbnail of Modeling and analysis of an electrically actuated microbeam based on nonclassical beam theory

ABSTRACT This work investigates the mechanical behavior of a clamped-clamped microbeam modeled wi... more ABSTRACT This work investigates the mechanical behavior of a clamped-clamped microbeam modeled within the framework of the strain-gradient elasticity theory. The governing equation of motion gives proper account of both the effect of the nonlinear midplane stretching and of an applied axial load. An electric-voltage difference, introducing into the model a further source of nonlinearity, is considered, including also a correction term for fringing field effects. The electric force acting on the microbeam is rearranged by means of the Chebyshev method, verifying the accuracy of the proposed approximation. The results show that a uniform error on the whole domain can be achieved. The static solution is obtained by a numerical differential quadrature method. The paper looks into the variation of the maximal deflection of the microbeam with respect to several parameters. Study of the pull-in limit on the high-order material parameters introduced by the nonclassical approach and a comparison with respect to the classical beam theory are also carried out. The numerical simulation indicates that the static response is larger, affected by the use of a nonclassical theory near the pull-in instability regime. The dynamical problem is, finally, analyzed, deriving the multi degree-of-freedom problem through a Galerkin-based approach. The study on the single degree-of-freedom model enables us to note the large influence of the nonlinear terms.

Research paper thumbnail of Boussinesq modeling of breaking waves: Description of turbulence

Journal of Geophysical Research, 2004

1] Improved turbulent closures for use in fully nonlinear Boussinesq-type models are described he... more 1] Improved turbulent closures for use in fully nonlinear Boussinesq-type models are described here. The approach extends previous works in order to give a more flexible and accurate description of the turbulence due to a breaking wave. Turbulent stresses are handled by means of the Boussinesq hypothesis, and the eddy viscosity is assumed to vary over the water depth according to different laws. The model is described in detail, and its performances are evaluated both against available analytical solutions and against experimental data of regular waves breaking over a slope. The influence of the vertical structure of turbulence under a breaking wave is analyzed by means of four different vertical profiles of eddy viscosity; the differences in terms of hydrodynamic features are also discussed. Among the four selected profiles, two of them (the uniform one and that with uniform eddy viscosity over the top half of the water column which linearly decreases to zero over the lower half ) give better overall performances when compared with experimental data concerning velocity profiles.

Research paper thumbnail of On shallow-water wakes: an analytical study

Journal of Fluid Mechanics, 2006

Analytical solutions for the characteristic scales of a turbulent wake in shallow flows are prese... more Analytical solutions for the characteristic scales of a turbulent wake in shallow flows are presented for two asymptotic cases: in one case, boundary-layer effects dominate whereas in the other, wake effects prevail. The latter case degenerates into the solution valid for an unbounded two-dimensional wake. These solutions show that the momentum deficit decreases exponentially in the longitudinal direction while the transverse velocity profile reveals a wake region characterized by a reduced velocity deficit compared to that of an unbounded wake. When wake-turbulence dominates there is a non-uniform turbulent viscosity in the longitudinal direction. These analytical solutions are compared with experimental data showing good agreement.

Research paper thumbnail of Horizontal mixing of quasi-uniform straight compound channel flows

Journal of Fluid Mechanics, 2010

The generation and evolution of large-scale vortices with vertical axis (macro-vortices) in a str... more The generation and evolution of large-scale vortices with vertical axis (macro-vortices) in a straight compound channel under quasi-uniform flow conditions is investigated. We discuss possible similarities and clear differences with free shear layer flows induced by the meeting of shallow streams of different speeds. An experimental investigation based on particle image velocimetry (PIV) measurements of free-surface velocities forms the basis for an analysis of both the specific features of macro-vortices and of the related mean flow characteristics. Dynamical properties strongly depend on the ratio r h between the main channel flow depth (h * mc ) and the floodplain depth (h * fp ), and three flow classes can be identified. 'Shallow flows' (r h > 3) are dominated by strong shearing and large macro-vortices populating the transition region between the main channel and the floodplains. The mean streamwise velocity induced in 'intermediate flows'

Research paper thumbnail of The effects of flow stratification by non-cohesive sediment on transport in high-energy wave-driven flows

Journal of Fluid Mechanics, 2008

... where u, v are the horizontal components of fluid velocity in the x (cross-shore ... performi... more ... where u, v are the horizontal components of fluid velocity in the x (cross-shore ... performing simulations in which the two-way feedback between sediment load and flow is included ... 5(a) demonstrates that this correlation is strongly due to the quadratic response between sediment ...

Research paper thumbnail of A comparison of two different types of shoreline boundary conditions

Computer Methods in Applied Mechanics and Engineering, 2002

Two different types of shoreline boundary conditions which can be used in either wave-resolving o... more Two different types of shoreline boundary conditions which can be used in either wave-resolving or wave-averaging models of waves and currents propagation in the nearshore are compared here. The two techniques are essentially different: in the first case the velocity of the shoreline is obtained by the momentum equation and the shoreline position is tracked by changing the grid position, while in the other case the velocity of the shoreline is obtained by a modified Riemann solver and the shoreline is defined as an interface between dry and wet fixed grid points. A number of test cases are described to compare the performance of the two techniques. (M. Brocchini). 0045-7825/02/$ -see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 0 4 5 -7 8 2 5 ( 0 2 ) 0 0 3 9 2 -4

Research paper thumbnail of Horizontal mixing in compound channels: a global shear layer model?

The horizontal mixing induced by large-scale vortical features (macrovortices) in a straight comp... more The horizontal mixing induced by large-scale vortical features (macrovortices) in a straight compound channel flow are analysed with specific emphasis on possible similarities with those characteristic of a shear layer induced by the meeting of three shallow streams of different speed (shear layer model). An experimental investigation based on PTV and PIV analysis of free surface velocities forms the basis for the following analyses both of specific 1

Research paper thumbnail of Modeling and analysis of an electrically actuated microbeam based on nonclassical beam theory

ABSTRACT This work investigates the mechanical behavior of a clamped-clamped microbeam modeled wi... more ABSTRACT This work investigates the mechanical behavior of a clamped-clamped microbeam modeled within the framework of the strain-gradient elasticity theory. The governing equation of motion gives proper account of both the effect of the nonlinear midplane stretching and of an applied axial load. An electric-voltage difference, introducing into the model a further source of nonlinearity, is considered, including also a correction term for fringing field effects. The electric force acting on the microbeam is rearranged by means of the Chebyshev method, verifying the accuracy of the proposed approximation. The results show that a uniform error on the whole domain can be achieved. The static solution is obtained by a numerical differential quadrature method. The paper looks into the variation of the maximal deflection of the microbeam with respect to several parameters. Study of the pull-in limit on the high-order material parameters introduced by the nonclassical approach and a comparison with respect to the classical beam theory are also carried out. The numerical simulation indicates that the static response is larger, affected by the use of a nonclassical theory near the pull-in instability regime. The dynamical problem is, finally, analyzed, deriving the multi degree-of-freedom problem through a Galerkin-based approach. The study on the single degree-of-freedom model enables us to note the large influence of the nonlinear terms.