54 research outputs found
Order-of-magnitude speedup for steady states and traveling waves via Stokes preconditioning in Channelflow and Openpipeflow
Steady states and traveling waves play a fundamental role in understanding
hydrodynamic problems. Even when unstable, these states provide the
bifurcation-theoretic explanation for the origin of the observed states. In
turbulent wall-bounded shear flows, these states have been hypothesized to be
saddle points organizing the trajectories within a chaotic attractor. These
states must be computed with Newton's method or one of its generalizations,
since time-integration cannot converge to unstable equilibria. The bottleneck
is the solution of linear systems involving the Jacobian of the Navier-Stokes
or Boussinesq equations. Originally such computations were carried out by
constructing and directly inverting the Jacobian, but this is unfeasible for
the matrices arising from three-dimensional hydrodynamic configurations in
large domains. A popular method is to seek states that are invariant under
numerical time integration. Surprisingly, equilibria may also be found by
seeking flows that are invariant under a single very large Backwards-Euler
Forwards-Euler timestep. We show that this method, called Stokes
preconditioning, is 10 to 50 times faster at computing steady states in plane
Couette flow and traveling waves in pipe flow. Moreover, it can be carried out
using Channelflow (by Gibson) and Openpipeflow (by Willis) without any changes
to these popular spectral codes. We explain the convergence rate as a function
of the integration period and Reynolds number by computing the full spectra of
the operators corresponding to the Jacobians of both methods.Comment: in Computational Modelling of Bifurcations and Instabilities in Fluid
Dynamics, ed. Alexander Gelfgat (Springer, 2018
Distinct Expression Profiles and Different Functions of Odorant Binding Proteins in Nilaparvata lugens StÄl
Background: Odorant binding proteins (OBPs) play important roles in insect olfaction. The brown planthopper (BPH), Nilaparvata lugens StaËl (Delphacidae, Auchenorrhyncha, Hemiptera) is one of the most important rice pests. Its monophagy (only feeding on rice), wing form (long and short wing) variation, and annual long distance migration (seeking for rice plants of high nutrition) imply that the olfaction would play a central role in BPH behavior. However, the olfaction related proteins have not been characterized in this insect. Methodology/Principal Findings: Full length cDNA of three OBPs were obtained and distinct expression profiles were revealed regarding to tissue, developmental stage, wing form and gender for the first time for the species. The results provide important clues in functional differentiation of these genes. Binding assays with 41 compounds demonstrated that NlugOBP3 had markedly higher binding ability and wider binding spectrum than the other two OBPs. Terpenes and Ketones displayed higher binding while Alkanes showed no binding to the three OBPs. Focused on NlugOBP3, RNA interference experiments showed that NlugOBP3 not only involved in nymph olfaction on rice seedlings, but also had non-olfactory functions, as it was closely related to nymph survival. Conclusions: NlugOBP3 plays important roles in both olfaction and survival of BPH. It may serve as a potential target fo
Genes with high penetrance for syndromic and non-syndromic autism typically function within the nucleus and regulate gene expression
Raw data from A high sample rate, wireless instrumented wheel for measuring 3D pushrim kinetics of a racing wheelchair
This file contains the unfiltered raw channels, tridimensional forces and moments measured at the hub, and the battery level signal measured by the prototype of a new instrumented wheel dedicated to wheelchair racing. These data were recorded at maximal acceleration up to maximal speed on a training roller by a male, international level, class T54 Paralympic athlete
Raw data from A high sample rate, wireless instrumented wheel for measuring 3D pushrim kinetics of a racing wheelchair
This file contains the unfiltered raw channels, tridimensional forces and moments measured at the hub, and the battery level signal measured by the prototype of a new instrumented wheel dedicated to wheelchair racing. These data were recorded at maximal acceleration up to maximal speed on a training roller by a male, international level, class T54 Paralympic athlete
Convection naturelle de Rayleigh-Bénard-Marangoni en régime transitoire
National audienc
Convection naturelle de Rayleigh-Bénard-Marangoni en régime transitoire
National audienc
Simulation of transient Rayleigh-BĂ©nard-Marangoni convection induced by evaporation
International audienceNumerical simulation of thermal convection induced by solvent evaporation in an initially isothermal fluid is considered. Both thermocapillarity and buoyancy driving forces are taken into account, and a criterium based on the Peclet number is used to analyze the stability of this transient problem. Critical Marangoni and Rayleigh numbers are obtained for a large range of Biot and Prandtl numbers. Results of the non-linear simulations are compared with a previous linear transient stability analysis based on a non-normal approach and with visualizations performed during polyisobutylene (PIB)/toluene solutions drying experiments. A scaling analysis is developed for the Marangoni problem and correlations are derived to predict the order of magnitude of temperature and velocity as a function of Bi, Ma and Pr numbers
Culture of microalgae with ultrafiltered seawater: from a feasibility study to an industrial development
International audienc
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