Hysteresis and precession of a swirling jet normal to a wall

Interaction of a swirling jet with a no-slip surface has striking features of fundamental and practical interest. Different flow states and transitions among them occur at the same conditions in combustors, vortex tubes, and tornadoes. The jet axis can undergo precession and bending in combustors; this precession enhances large-scale mixing and reduces emissions of NOx. To explore the mechanisms of these phenomena, we address conically similar swirling jets normal to a wall. In addition to the Serrin model of tornadolike flows, a new model is developed where the flow is singularity free on the axis. New analytical and numerical solutions of the Navier-Stokes equations explain occurrence of multiple states and show that hysteresis is a common feature of wall-normal vortices or swirling jets no matter where sources of motion are located. Then we study the jet stability with the aid of a new approach accounting for deceleration and nonparallelism of the base flow. An appropriate transformation of variables reduces the stability problem for this strongly nonparallel flow to a set of ordinary differential equations. A particular flow whose stability is studied in detail is a half-line vortex normal to a rigid plane-a model of a tornado and of a swirling jet issuing from a nozzle in in a combustor. Helical counter-rotating disturbances appear to be first growing as Reynolds number increases. Disturbance frequency changes its sign along the neutral curve while the wave number remains positive. Short disturbance waves propagate downstream and long waves propagate upstream. This helical instability causes bending of the vortex axis and its precession-the effects observed in technological flows and in tornadoes.V. Shtern, J. M

The urban geopolitics of neighboring: conflict, encounter and class in Jerusalem’s settlement/neighborhood

This article examines a unique, yet paradigmatic, case study of a colonial neighborhood in East Jerusalem that is undergoing a significant demographic transformation.1 The French Hill neighborhood, built in 1971, was one of the first settlements in East Jerusalem. Initially, it was populated primarily by upper-middle class secular-Jewish residents. This group has been steadily diminishing as two other distinct new groups moved into the neighborhood: Ultra-Orthodox Jews and Palestinians. This volatile social mix has caused intense inter-ethnic and intra-ethnic collisions. Based on qualitative and quantitative studies, we argue that the juxtaposition of colonial and neoliberal logics of space reveals a shared, yet fragile, middle-class identity. We suggest that this new geopolitical space of neighboring calls for a discussion of political conflict, housing and current colonial conditions that brings class back to our understanding of the production of contested space

Hysteresis and precession of a swirling jet normal to a wall

Interaction of a swirling jet with a no-slip surface has striking features of fundamental and practical interest. Different flow states and transitions among them occur at the same conditions in combustors, vortex tubes, and tornadoes. The jet axis can undergo precession and bending in combustors; this precession enhances large-scale mixing and reduces emissions of NOx. To explore the mechanisms of these phenomena, we address conically similar swirling jets normal to a wall. In addition to the Serrin model of tornadolike flows, a new model is developed where the flow is singularity free on the axis. New analytical and numerical solutions of the Navier-Stokes equations explain occurrence of multiple states and show that hysteresis is a common feature of wall-normal vortices or swirling jets no matter where sources of motion are located. Then we study the jet stability with the aid of a new approach accounting for deceleration and nonparallelism of the base flow. An appropriate transformation of variables reduces the stability problem for this strongly nonparallel flow to a set of ordinary differential equations. A particular flow whose stability is studied in detail is a half-line vortex normal to a rigid plane-a model of a tornado and of a swirling jet issuing from a nozzle in in a combustor. Helical counter-rotating disturbances appear to be first growing as Reynolds number increases. Disturbance frequency changes its sign along the neutral curve while the wave number remains positive. Short disturbance waves propagate downstream and long waves propagate upstream. This helical instability causes bending of the vortex axis and its precession-the effects observed in technological flows and in tornadoes.V. Shtern, J. M

Influence of rheological features of behaviour of the porous damaged materials on their indentation process

На основі теорії пластичності пористого тіл за допомогою комп'ютерного моделювання методом скінчених елементів досліджується напружено-деформований стан поблизу сферичного і конічного індентора при різних властивостях индентованого матеріалу. Аналізується розподіл густини в околі індентора в залежності від властивостей пористого тіла та умов тертя між індентором та пористим тілом. Наводяться діаграми навантаження в залежності від схильності до дилатансії та зовнішнього тертя. Приділено увагу виникненню та формі навалів навколо индентора.The purpose of this work was research of the main features of behavior of the porous and damaged powder based materials at indentation process. The mechanical behavior of such materials is characterized by a loosening at purely shift tension and asymmetry of a response to stretching and compression. The rheological model of plasticity of porous materials with imperfect interpartial contacts which was earlier proposed one of authors is considered. Based on such theory of plasticity for porous media with distributed damages using finite element computer simulation the deformed state near spherical and conical indenter for different mechanical properties of indented material and different friction conditions between indenter and porous body has been studied. Porosity distribution near indenter depending on properties of porous body and friction conditions between indenter and porous body has been analyzed. Load profiles as a function of dilatancy tendency and contact friction has been shown. Development of bulk around indenter and its shape has been investigated.На основе теории пластичности пористого тела с помощью компьютерного моделирования методом конечных элементов исследуется напряженно-деформированное состояние вблизи сферического и конического индентора при различных свойствах индентируемого материала. Анализируется распределение плотности в окрестности индентора в зависимости от свойств пористого тела и условий трения между индентором и пористым телом. Приводятся диаграммы нагружения в зависимости от склонности к дилатансии и внешнего трения. Уделяется внимание возникновению и форме навалов вокруг индентора

Some results of cislunar plasma research

The main results of plasma cislunar investigations, carried out during Luna-19 and Luna-22 spacecraft flights by means of dual frequency dispersion interferrometry, are briefly outlined. It is shown that a thin layer of plasma, with a height of several tens of kilometers and a maximum concentration of the order 1,000 electrons/cu cm exists above the solar illuminated lunar surface. A physical model of the formation and existence of such a plasma in cislunar space is proposed, taking into account the influence of local magnetic areas on the moon

The nighttime ionosphere of Mars from Mars-4 and Mars-5 radio occultation dual-frequency measurements

Dual frequency radio sounding of the Martian nighttime ionosphere was carried out during the exits from behind the planet of the Mars-4 spacecraft on February 2, 1974 and the Mars-5 spacecraft on February 18, 1974. In these experiments, the spacecraft transmitter emitted two coherent monochromatic signals in decimeter and centimeter wavelength ranges. At the Earth receiving station, the reduced phase difference (or frequencies) of these signals was measured. The nighttime ionosphere of Mars measured in both cases had a peak electron density of approximately 5 X 1,000/cu cm at an altitude of 110 to 130 km. At the times of spacecraft exit, the solar zenith angles at the point of occultation were 127 deg and 106 deg, respectively. The height profiles of electron concentration were obtained assuming spherical symmetry of the Martian ionosphere

Multivariate p-dic L-function

We construct multivariate p-adic L-function in the p-adic number fild by using Washington method.Comment: 9 page

Asymmetric inheritance of RNA toxicity in C. elegans expressing CTG repeats

Nucleotide repeat expansions are a hallmark of over 40 neurodegenerative diseases and cause RNA toxicity and multisystemic symptoms that worsen with age. Through an unclear mechanism, RNA toxicity can trigger severe disease manifestation in infants if the repeats are inherited from their mother. Here we use Caenorhabditis elegans bearing expanded CUG repeats to show that this asymmetric intergenerational inheritance of toxicity contributes to disease pathogenesis. In addition, we show that this mechanism is dependent on small RNA pathways with maternal repeat-derived small RNAs causing transcriptomic changes in the offspring, reduced motility, and shortened lifespan. We rescued the toxicity phenotypes in the offspring by perturbing the RNAi machinery in the affected hermaphrodites. This points to a novel mechanism linking maternal bias and the RNAi machinery and suggests that toxic RNA is transmitted to offspring, causing disease phenotypes through intergenerational epigenetic inheritance.Peer reviewe

Generalized Bloch analysis and propagators on Riemannian manifolds with a discrete symmetry

We consider an invariant quantum Hamiltonian $H=-\Delta_{LB}+V$ in the $L^{2}$ space based on a Riemannian manifold $\tilde{M}$ with a countable discrete symmetry group $\Gamma$. Typically, $\tilde{M}$ is the universal covering space of a multiply connected Riemannian manifold $M$ and $\Gamma$ is the fundamental group of $M$. On the one hand, following the basic step of the Bloch analysis, one decomposes the $L^{2}$ space over $\tilde{M}$ into a direct integral of Hilbert spaces formed by equivariant functions on $\tilde{M}$. The Hamiltonian $H$ decomposes correspondingly, with each component $H_{\Lambda}$ being defined by a quasi-periodic boundary condition. The quasi-periodic boundary conditions are in turn determined by irreducible unitary representations $\Lambda$ of $\Gamma$. On the other hand, fixing a quasi-periodic boundary condition (i.e., a unitary representation $\Lambda$ of $\Gamma$) one can express the corresponding propagator in terms of the propagator associated to the Hamiltonian $H$. We discuss these procedures in detail and show that in a sense they are mutually inverse

SOME ABSTRACT PROPERTIES OF SEMIGROUPS APPEARING IN SUPERCONFORMAL THEORIES

A new type of semigroups which appears while dealing with $N=1$ superconformal symmetry in superstring theories is considered. The ideal series having unusual abstract properties is constructed. Various idealisers are introduced and studied. The ideal quasicharacter is defined. Green's relations are found and their connection with the ideal quasicharacter is established.Comment: 11 page