0000000000681121
AUTHOR
Paolo Barrera
showing 2 related works from this author
A Langevin Approach to the Diffusion Equation
2002
We propose a generalized Langevin equation as a model for the diffusion equation of air pollution in the atmosphere. We write down a partial stochastic differential equation for the pollutant concentration, which we solve exactly obtaining the first and the second moment of the pollutant concentration. We obtain a linear multiplicative stochastic differential equation for the Fourier components of the concentration, which can be used to calculate higher moments of the concentration. We obtain the exact steady state solution in the case of neutral atmosphere and a general expression of the mean concentration as a function of the fluctuation intensity of the wind speed, the diffusion coeffici…
Group analysis and similarity solutions of the compressible boundary layer equations
1989
In this paper the application of Lie's methods to the equations of the laminar boundary layer is discussed. The momentum and energy equations in Prandtl's form are considered for a steady, viscous, compressible laminar flow with non zero pressure gradient, variable viscosity and thermal conductivity. Group analysis yields similarity solutions for given pressure distributions and particular values of the invariance group parameters (group classification). Crocco's transformation is obtained for the infinite-dimensional group of the Lie's algebra admitted by the equations.