The randomization effect of the two-way (particle-flow) interaction has been studied and quantified using the notion of distributed chaos and the results of numerical simulations and laboratory measurements. It is shown, in particular, that an increase of such parameters as the particle volume fraction, particle mass loading, and Stokes number results generally in stronger randomization of the particle-laden flows. An important role of spontaneous breaking of the local reflectional symmetry in the randomization of the particle-laden flows has been also analyzed using relevant dynamical invariants.
In this work we propose an alternate scaling for the head loss in the steady flow of Newtonian fluids through tubes. The characteristics of the proposed scaling render more clear the role of inertia in this flow and ensure that the trends of the relationship between dimensionless quantities are the same ones observed in the dimensional problem.
The paper considers the dynamics of the spreading liquid droplets after impact on a solid surface. The dynamics of a drop falling on a solid surface is shown using numerical simulation based on the solution of 2D and 3D Navier-Stokes equations for a two-layer liquid-gas system. The results of numerical simulation are compared with experimental data.
This investigation presents evidence of the relation between the dynamics of intense events in small-scale turbulence and the energy cascade. We use the generalised (Hölder) means to track the temporal evolution of intense events of the enstrophy and the dissipation in direct numerical simulations of isotropic turbulence. We show that these events are modulated by large-scale fluctuations, and that their evolution is consistent with a local multiplicative cascade, as hypothesised by a broad class of intermittency models of turbulence.
The two-dimensional Green-Naghdi equations with uneven bottom topography are studied in this paper. The function defining the bottom topography can be dependent on time. Group classification of these equations with respect to the function describing the topography of the bottom is performed in the paper. The algebraic approach used for the analysis of the classifying equations.
The opioid peptides are implicated in regulation of neuroendocrine functions in vertebrates. However, influence of an opioid peptide, dynorphin A (DYN) on reproduction is understudied in fish. The aim of the present investigation was to study the influence of DYN on the pituitary-ovary axis in the fish Oreochromis mossambicus. Daily injections (i.p.) of 250 μg DYN kg-1 body weight for 22 days during the ovarian cycle caused reduction in the intensity and the percent area of luteinizing hormone (LH) immunoreactive content in the proximal pars distalis region of the pituitary gland compared to an intense immunostaining in time-matched controls. In the ovary, DYN treatment caused a decrease in the number of stage I (previtellogenic) follicles compared with time-matched controls. No difference was noticed in the number of stage IV (vitellogenic) follicles among different experimental groups, whereas the number of stage II and III follicles (previtellogenic) was higher in DYN-treated fish than in time-matched controls. However, there was a reduction in the number of stage V (preovulatory) follicles in DYN treated fish compared with time-matched controls. Taken together, these results indicate that DYN exerts inhibitory effect on follicular recruitment at late vitellogenic stage, through the suppression of LH secretion in fish. This article is protected by copyright. All rights reserved.
A new exact solution of the Navier-Stokes equation is derived for the compressible flows which are far from equilibrium in the limit of extremely low shear viscosity and relatively large volume viscosity. The closed description of the evolution of statistical moments of velocity is obtained, thereby bypassing the closure problem in the theory of turbulence.
This is a collection of notes for part of a short course on modal methods in fluid mechanics held at DAMTP, University of Cambridge, in the summer of 2019. These notes introduce the reader to resolvent analysis as it is currently used in fluid mechanics. They are aimed at the average beginning PhD student, and will serve as a base from which to explore the literature.
In this letter we numerically investigate the merging mechanism between two clusters of point vortices. We introduce a concept of renormalized Onsager function, an elaboration of the solutions of the mean field equation, and use it to understand the shape of the single cluster observed as a result of the merging process. We finally discuss the potential implications for the inverse cascade 2D turbulence.
The common cold is the most frequent human illness, and may be caused by several families of viruses, particularly the more than 100 serotypes of rhinoviruses. Inaccurate perceptions that antibiotics improve patient outcomes fuel the number of doctor visits and requests for antibiotics. The inappropriate use of antibiotics for minor, self-limiting, usually viral, upper-respiratory tract infections does not alter the course of the disease, and adds to the burden of antibiotic resistance. In addition, there is also no evidence to suggest that antibiotics prevent secondary bacterial complications following viral upper-respiratory tract infections. While most over-the-counter cold and flu remedies have no proven efficacy, they appear to attenuate the immune response to the infecting virus, and there is little doubt that appropriate symptomatic treatment can make the patient feel better. Therefore, symptomatic therapy remains the mainstay of common cold treatment. This article briefly reviews the components of cold and flu remedies, and provides a symptom-based assessment for the selection of appropriate over-the-counter medicine.
Upper bounds on the heat transport and other quantities of interest in Rayleigh-Bénard convection are derived in previous work from constraints resulting from the equations of time evolution for kinetic energy, the root mean square of temperature, and the temperature averaged over horizontal planes. Here, we investigate the effect of a new constraint derived from the time evolution equation for the advective heat transport. This additional constraint leads to improved bounds on the toroidal dissipation.
Governing equations for two-dimensional inviscid free-surface flows with constant vorticity over arbitrary non-uniform bottom profile are presented in exact and compact form using conformal variables. An efficient and very accurate numerical method for this problem is developed.
We study stability of axisymmetric liquid bridges between two axisymmetric solid bodies in the absence of gravity under arbitrary asymmetric perturbations which are expanded into a set of angular Fourier modes. We determine the stability region boundary for every angular mode in case of both fixed and free contact lines. Application of this approach allows us to demonstrate existence of stable convex nodoid menisci between two spheres.