Modeling

ABSTRACT The modelling of particle-particle interactions in binary mixture of particle suspended in turbulent flows was discussed. The modelling was based on a specific closure of collision kernel, which takes into account the correlation between the colliding particle velocities. It was found that the particle kinetic energies were not strongly modified by collisions. The model predictions were found to be compared with statistics issued from Large Eddy simulation of an homogeneous isotropic gas coupled with Discrete Particle Simulation of a non-settling mixture.

ABSTRACT This paper presents a new PDF model for turbulent fluid-particles interactions in the near wall region. Such models have already been presented by Swailes & Reeks [1] or more recently by Van Dijk & Swailes [2]. The PDF approach allows calculating directly the spatial evolution of the wall normal particles velocity distribution. As shown by Swailes & Reeks [1] this approach as many advantages. First, all the statistical moments used (concentration, mean velocity, fluctuating velocities) are contained in the PDF. Thus all the equations for those moments are coupled together within the PDF equation. Second, the boundary conditions can be easily specified, even for the most complex cases as partial absorption. The present study proposes to simplify the fluid particle interaction term of the PDF equation with a new closure model. This simplification is inspired by the BGK models. The paper presents first the model and its numerical implementation. It is evaluated in a wall bounded homogenous turbulence as described by Swailes & Reeks [1]. The results of the present model are then compared to those obtained by Swailes & Reeks [1]. The model is also applied to a channel flow boundary layer configuration. Those simulations illustrate the mechanisms responsible for particles dispersion in the boundary layer turbulence.

The present paper is an attempt to summarize the results obtained on the modelling of the shoulder of flux phenomenon in the case of impinging jets on very hot plates. First, the phenomenon of shoulder of flux is described through literature results. Then, a physical approach of this phenomenon is given. The modelling of the shoulder of flux is based

ABSTRACT This paper presents a statistical approach, known as mesoscopic Eulerian formalism (Février et al., J Fluid Mech 533:1–46, 2005), which is extended in order to model a cloud of inertial evaporating droplets interacting with a turbulent carrier flow. This approach is checked in a non-isothermal droplet-laden turbulent planar jet by means of a priori tests. The “measurement” of the mesoscopic particle-velocity and particle-temperature moments is accomplished by using the Eulerian particle fields computed from a Direct Numerical Simulation (DNS) coupled with a Lagrangian approach for the droplets. The results of this work show the ability of such an approach to describe the evaporating dispersed phase interacting with turbulent flows.

In 2008 Chris Anderson wrote a provocative piece titled TheEnd of Theory. The idea being that we no longer need to abstract and hypothesis; we simply need to let machines lead us to the patterns, trends, and relationships in social, economic, political, and environmental relationships. According to Anderson, the new availability of huge amounts of data offers a whole new way of understanding the world. Correlation supersedes causation, and science can advance even without coherent models and unified theories. But numbers, contrary to Anderson’s assertion, do not, in fact, speak for themselves. From the neuroscience’s standpoint, every choice we make is a reflection of an, often unstated, set of assumptions and hypotheses about what we want and expect from the data: no assertion, no prediction, no decision making is possible without an a priori opinion, without a project. Data-driven science essentially refers to the application of mathematics and technology on data to extract insights for problems, which are very clearly defined. In the real world, however, not all problems are such. To help solve them, one needs to understand and appreciate the context. The problem of landscape becomes, for this reason, critical and decisive. It requires an interdisciplinary approach consisting of several different competencies and skills.

Sources of Error in a Rigid Body Simulation of Rigid Parts on a Vibrating Rigid Plate. StephenBerard Rensselaer Polytechnic Institute 110 8th Street Troy, NY sberard@cs.rpi.edu Binh Nguyen Rensselaer Polytechnic Institute 110 8th Street Troy, NY nguyeb2@cs.rpi.edu ...

Manipulating spectral structure often leads to degradation of speech quality, which is mainly due to insufficient smoothness of the modified spectra between frames, and ineffective spectral modification. This paper presents a new spectral modification method to improve the quality of modified speech. If frames are processed independently, discontinuous features may be generated. Therefore, a speech analysis technique called temporal decomposition

Lower back pain is a major public health problem. Despite claims that lumbar belts change spinal posture due to applied pressure on the trunk, no mechanical model has yet been published to prove this treatment. This paper describes a first model for belt design, based on the one hand on the mechanical properties of the fabrics and the belt geometry, and on the other hand on the trunk geometrical and mechanical description. The model provides the estimation of the pressure applied to the trunk, and a unique indicator of the belt mechanical efficiency is proposed: pressure is integrated into a bending moment characterizing the belt delordosing action on the spine. A first in-silico clinical study of belt efficiency for 15 patients with 2 different belts was conducted. Results are very dependent on the body shape: in the case of high BMI patients, the belt effect is significantly decreased, and can be even inverted, increasing the lordosis. The belt stiffness proportionally increases the pressure applied to the trunk, but the influence of the design itself on the bending moment is clearly outlined. Moreover, the belt/trunk interaction, modeled as sticking contact and the specific way patients lock their belts, dramatically modifies the belt action. Finally, even if further developments and tests are still necessary, the model presented in this paper seems suitable for in-silico pre-clinical trials on real body shapes at a design stage.