1,722,418 research outputs found
Plane Poiseuille Flow with Symmetric and Nonsymmetric Gas-Wall Interactions
No full textInterest in some basic problems of linearized kinetic theory has been
maintained over recent years by the possibility of applications to the
micromachines and other devices with very tiny air gaps. These problems require accurate solutions of the Boltzmann equation under possibly various boundary conditions. Therefore, in the current paper, plane Poiseuille flow between parallel plates is investigated using a numerical technique that applies to the integral form of the Boltzmann equation.
In order to gain a better insight into the role played by different boundary
conditions on the flux in microchannels, the bulk velocity profiles of the
gas are reported for Maxwell's scattering kernel as well as for
Cercignani-Lampis's model
On the Reynolds equation for linearized models of the Boltzmann operator
No full textRarefied gas flows in ultra-thin film slider bearings are studied in a wide range
of Knudsen numbers. The generalized Reynolds equation, first derived by
Fukui and Kaneko (1987, 1988, 1990) on the basis of the linearized
Bhatnagar-Gross-Krook (BGK) Boltzmann equation (Bhatnagar et al.
1954), has been extended by considering a more refined kinetic model of the collisional
Boltzmann operator, i.e., the linearized ellipsoidal statistical (ES)
model, which allows the Prandtl number to assume its proper value (Cercignani
and Tironi 1966). Since the generalized Reynolds equation is a flow rate–based
model and is obtained by calculating the fundamental flows in the lubrication
film (i.e., the Poiseuille and Couette flows), the plane Poiseuille-Couette flow
problem between parallel plates has been preliminarily investigated by means
of the linearized ES model. General boundary conditions of Maxwell’s type
have been considered by allowing for bounding surfaces with different
physical properties
The Cercignani Conjecture About a Classical Zero-Point Energy, and Its Confirmation for Ionic Crystals
No full textA characteristic feature of Quantum Mechanics is that it predicts the existence of zero-point energy, i.e., of states with a nonvanishing kinetic energy at zero temperature. This is a fact that is experimentally verified and is considered to be inconceivable in a classical frame. In the year 1972 Carlo Cercignani advanced the idea that a classical zero-point energy may be conceived, if one understands the corresponding motions as characterized by being (in the terminology used at those times) of “ordered” rather than of “chaotic” type. Here we illustrate how the Cercignani idea is actually implemented for an ionic crystal model which was already shown to be of such a realistic character as to reproduce in a remarkably good way, in terms of the Newtonian trajectories of the ions, the experimental infrared spectra
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