14,056 research outputs found
The scenario of two-dimensional instabilities of the cylinder wake under EHD forcing: A linear stability analysis
We propose to study the stability properties of an air flow wake forced by a dielectric barrier discharge (DBD) actuator, which is a type of electrohydrodynamic (EHD) actuator. These actuators add momentum to the flow around a cylinder in regions close to the wall and, in our case, are symmetrically disposed near the boundary layer separation point.
Since the forcing frequencies, typical of DBD, are much higher than the natural shedding frequency of the flow, we will be considering the forcing actuation as stationary.
In the first part, the flow around a circular cylinder modified by EHD actuators will be experimentally studied by means of particle image velocimetry (PIV). In the second part, the EHD actuators have been numerically implemented as a boundary condition on the cylinder surface. Using this boundary condition, the computationally obtained base flow is then compared with the experimental one in order to relate the control parameters from both methodologies.
After validating the obtained agreement, we study the Hopf bifurcation that appears once the flow starts the vortex shedding through experimental and computational approaches. For the base flow derived from experimentally obtained snapshots, we monitor the evolution of the velocity amplitude oscillations. As to the computationally obtained base flow, its stability is analyzed by solving a global eigenvalue problem obtained from the linearized Navier–Stokes equations. Finally, the critical parameters obtained from both approaches are compared
Force chains and contact network topology in packings of elongated particles
By means of contact dynamic simulations, we investigate the contact network
topology and force chains in two-dimensional packings of elongated particles
modeled by rounded-cap rectangles. The morphology of large packings of
elongated particles in quasistatic equilibrium is complex due to the combined
effects of local nematic ordering of the particles and orientations of contacts
between particles. We show that particle elongation affects force distributions
and force/fabric anisotropy via various local structures allowed by steric
exclusions and the requirement of force balance. As a result, the force
distributions become increasingly broader as particles become more elongated.
Interestingly, the weak force network transforms from a passive stabilizing
agent with respect to strong force chains to an active force-transmitting
network for the whole system. The strongest force chains are carried by
side/side contacts oriented along the principal stress direction.Comment: Soumis a Physical Review
Neutrino Mass Patterns within the See-saw Model from Multi-localization along Extra Dimensions
We study a multi-localization model for charged leptons and neutrinos,
including the possibility of a see-saw mechanism. This framework offers the
opportunity to allow for realistic solutions in a consistent model without
fine-tuning of parameters, even if quarks are also considered. Those solutions
predict that the large Majorana mass eigenvalues for right-handed neutrinos are
of the same order of magnitude, although this almost common mass can span a
large range (bounded from above by ). The model also
predicts Majorana masses between and $\sim 5 \
10^{-2}{\rm eV}\beta\theta_{13}10^{-2} \lesssim
\sin \theta_{13} \lesssim 10^{-1}$, but smaller values are not totally excluded
by the model.Comment: 36 pages, 8 figure
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