Marco Martins Afonso - Academia.edu (original) (raw)
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Papers by Marco Martins Afonso
EPL (Europhysics Letters), 2013
We study the effect of surface gravity waves on the motion of inertial particles in an incompress... more We study the effect of surface gravity waves on the motion of inertial particles in an incompressible fluid. We perform analytical calculations based on perturbation expansions which allow us to predict the dynamics of inertial particles in the deep-water regime. We find that the presence of inertia leads to a non-negligible correction to the well-known horizontal Stokes drift velocity. Moreover, we find that the vertical sedimentation velocity is also affected by a drift induced by waves. The latter result may have some relevant consequences on the rate of sedimentation of particles of finite size. We underline that the vertical drift would also be observed in the (hypothetical) absence of the gravitational force. Kinematic numerical simulations are performed and the results are found to be in excellent agreement with the analytical predictions, even for values of the parameters beyond the perturbative limit.
Journal of Turbulence, 2005
The Large-Eddy Simulation technique is exploited to investigate statistics of temperature fluctua... more The Large-Eddy Simulation technique is exploited to investigate statistics of temperature fluctuations, r θ ,inAtmospheric Boundary Layers (ABLs) with different degrees of convection. We found statistical characterizations for both strong and weak fluctuations. In terms of probability density functions (pdfs) of r θ , weak and strong fluctuations reflect themselves in different rescaling properties of pdf cores and tails, respectively. For the cores, the observed rescaling is P( r θ ) = r −αP ( r θ/r α ); while for the tails, data are compatible with P( r θ ) ∝ r ζ∞ . Such two rescaling properties are equivalent to saying | r θ | p ∼r ζp , with ζ p = αp for small p's and ζ p = ζ ∞ = constant for large p's. Both α and ζ ∞ turn out to be z-independent within the mixed layer and, more importantly, they do not appreciably vary by changing the degree of convection in the ABL. We also address the question related to the geometrical structure of temperature jumps contributing to large | r θ |. Finally, the possible relevance of our results to the long-standing problem of subgrid scale parameterizations is discussed.
EPL (Europhysics Letters), 2013
We study the effect of surface gravity waves on the motion of inertial particles in an incompress... more We study the effect of surface gravity waves on the motion of inertial particles in an incompressible fluid. We perform analytical calculations based on perturbation expansions which allow us to predict the dynamics of inertial particles in the deep-water regime. We find that the presence of inertia leads to a non-negligible correction to the well-known horizontal Stokes drift velocity. Moreover, we find that the vertical sedimentation velocity is also affected by a drift induced by waves. The latter result may have some relevant consequences on the rate of sedimentation of particles of finite size. We underline that the vertical drift would also be observed in the (hypothetical) absence of the gravitational force. Kinematic numerical simulations are performed and the results are found to be in excellent agreement with the analytical predictions, even for values of the parameters beyond the perturbative limit.
Journal of Turbulence, 2005
The Large-Eddy Simulation technique is exploited to investigate statistics of temperature fluctua... more The Large-Eddy Simulation technique is exploited to investigate statistics of temperature fluctuations, r θ ,inAtmospheric Boundary Layers (ABLs) with different degrees of convection. We found statistical characterizations for both strong and weak fluctuations. In terms of probability density functions (pdfs) of r θ , weak and strong fluctuations reflect themselves in different rescaling properties of pdf cores and tails, respectively. For the cores, the observed rescaling is P( r θ ) = r −αP ( r θ/r α ); while for the tails, data are compatible with P( r θ ) ∝ r ζ∞ . Such two rescaling properties are equivalent to saying | r θ | p ∼r ζp , with ζ p = αp for small p's and ζ p = ζ ∞ = constant for large p's. Both α and ζ ∞ turn out to be z-independent within the mixed layer and, more importantly, they do not appreciably vary by changing the degree of convection in the ABL. We also address the question related to the geometrical structure of temperature jumps contributing to large | r θ |. Finally, the possible relevance of our results to the long-standing problem of subgrid scale parameterizations is discussed.