The influence of nonlinear bottom friction on the properties of decaying cyclonic and anticyclonic vortex structures in a shallow rotated fluid

2014 ◽  
Vol 753 ◽  
pp. 217-241 ◽  
Author(s):  
S. V. Kostrykin ◽  
A. A. Khapaev ◽  
I. G. Yakushkin
Keyword(s):  
Horizontal Plane ◽  
Laboratory Experiments ◽  
Initial State ◽  
Turbulent Eddy ◽  
Modified Model ◽  
Initial Stage ◽  
Free Decay ◽  
Axisymmetric Vortex ◽  
Theoretical Predictions ◽  
Eddy Flow

AbstractThe problem of the decay of intense vortices in a shallow rotated neutrally stratified fluid is considered using simulations with a modified model of von Kármán type and laboratory experiments. The numerical model describes a forced axisymmetric vortex, vertically confined, but infinite in the horizontal plane. It may be used for comparisons with laboratory experiments, in which a quasi-turbulent eddy flow is generated, using magnetohydrodynamic forcing. A detailed analysis of simulations of the free decay of the flow from an initial state, given either by an arbitrary Poiseuille or by a forced stationary profile of vorticity, is provided. Based on this analysis, three different regimes of decay of intense anticyclones in the parameter space of the Ekman and initial Rossby numbers are found. It is shown that anticyclones with large enough Rossby and small enough Ekman numbers may decay to a non-trivial stationary state, or at least they decay much slower than cyclones of the same intensity. The laboratory experiments show much slower decay of intense anticyclones than weak anticyclones or cyclones, and also a dominance of anticyclones over cyclones during the initial stage of decay. These observations qualitatively agree with theoretical predictions.

scholarly journals Dual subtractions

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Renato Maria Prisco ◽  
Francesco Tramontano
Keyword(s):  
Field Theory ◽  
Quantum Field ◽  
Matrix Elements ◽  
Leading Order ◽  
Initial State ◽  
Final State ◽  
Dual Representation ◽  
Subtraction Scheme ◽  
Theoretical Predictions ◽  
Perturbative Quantum

Abstract We propose a novel local subtraction scheme for the computation of Next-to-Leading Order contributions to theoretical predictions for scattering processes in perturbative Quantum Field Theory. With respect to well known schemes proposed since many years that build upon the analysis of the real radiation matrix elements, our construction starts from the loop diagrams and exploits their dual representation. Our scheme implements exact phase space factorization, handles final state as well as initial state singularities and is suitable for both massless and massive particles.

The Peak Overpressure Field Resulting From Shocks Emerging From Circular Shock Tubes

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
A. J. Newman ◽  
J. C. Mollendorf
Keyword(s):  
Shock Tube ◽  
Horizontal Plane ◽  
Three Dimensional ◽  
Polar Angle ◽  
Field Measurements ◽  
Initial Development ◽  
Theoretical Predictions ◽  
Mach Numbers ◽  
Tube Exit ◽  
Semi Empirical

A simple semi-empirical model for predicting the peak overpressure field that results when a shock emerges from a circular shock tube is presented and validated. By assuming that the shape of the expanding shock remains geometrically similar after an initial development period, an equation that describes the peak overpressure field in the horizontal plane containing the shock tube’s centerline was developed. The accuracy of this equation was evaluated experimentally by collecting peak overpressure field measurements along radials from the shock tube exit at 0 deg, 45 deg, and 90 deg over a range of shock Mach numbers from 1.15 to 1.45. It was found that the equation became more accurate at higher Mach numbers with percent differences between experimental measurements and theoretical predictions ranging from 1.1% to 3.6% over the range of Mach numbers considered. (1) Shocks do propagate in a geometrically similar manner after some initial development length over the range of Mach numbers considered here. (2) The model developed here gives reasonable predictions for the overpressure field from a shock emerging from a circular shock tube. (3) Shocks are expected to be completely symmetric with respect to the shock tube’s centerline, and hence, a three dimensional overpressure field may be predicted by the model developed here. (4) While there is a range of polar angle at which the shock shape may be described as being spherical with respect to the shock tube’s exit, this range does not encompass the entirety of the half space in front of the shock tube, and the model developed here is needed to accurately describe the entire peak overpressure field.

scholarly journals KUBAN UKRAINIZATION INITIAL STATE IN THE KUBAN EMERGENCY PARLIAMENT MEETING MATERIALS

2018 ◽  
pp. 109-113
Author(s):  
A. V. Markin
Keyword(s):  
Initial State ◽  
Language And Culture ◽  
Initial Stage ◽  
National Movements

The article is devoted to the initial stage of Ukrainization in the Kuban, which consisted mainly of a purposeful and consistent introduction of the Ukrainian language and culture into the life of the population. After the February 1917 events in Russia, various national movements, where they were present, sharply intensified. In particular, the Cuban-Ukrainian movement in the Kuban also became more active. Initially, measures for this implementation were planned to be implemented in the sphere of education, mainly school. At the first stage it was spontaneous, at the initiative of the inhabitants of some localities, but with the support of the Kuban Territorial and legislative rads. The Kuban Parliament, immediately after its formation in March 1917, announced to the Provisional Government its plans to create an extensive network of Ukrainian schools, to use the Ukrainian language more widely, to promote its implementation in church services.

Influence of the Structure of a Gouge-Filled Fault on the Parameters of Acoustic Emission

2019 ◽  
Vol 105 (5) ◽  
pp. 759-765 ◽  
Author(s):  
Alexey A. Ostapchuk ◽  
Kseniya G. Morozova ◽  
Dmitry V. Pavlov
Keyword(s):  
Acoustic Emission ◽  
Laboratory Experiments ◽  
Shear Crack ◽  
Kinematic Parameters ◽  
Stick Slip ◽  
Omori Law ◽  
Shear Loads ◽  
Initial Stage ◽  
Slip Event ◽  
Model Setup

Presented are the results of laboratory experiments on investigating manifestations of acoustic emission (AE) of a gouge-filled fault during stick-slip. The laboratory experiments were held at the slider-model setup, when a granite block slides along a rough granite base under normal and shear loads. In the course of experiments we altered the structure of the two-component filler of the fault and focused on variations of the AE parameters. The kinematic parameters of fault slip events in all the realizations remained approximately the same. The eff ect of gouge structure on the statistics of AE has been revealed. An alteration of proportion of quartz sand / glass beads in the filler of the fault was accompanied by an alteration of the b-value of frequency-energy distribution from 0.53 to 0.85, and the p-value of Omori law from 1.00 to 2.06. Also, it has been demonstrated that the nucleation of a slip event is accompanied by an alteration of the mechanism of AE generation – at the initial stage the 'tensile crack' signals prevailed, while at the final stage – the 'shear crack' signals did. The alteration of AE genesis manifested vividly in a corresponding alteration of the emitted waveforms for all the realizations.

The thermal bar

1992 ◽  
Vol 236 ◽  
pp. 27-42 ◽  
Author(s):  
S. S. Zilitinkevich ◽  
K. D. Kreiman ◽  
A. Yu. Terzhevik
Keyword(s):  
Laboratory Experiments ◽  
Heat Budget ◽  
Traditional Approach ◽  
Laminar Regime ◽  
Laboratory Measurements ◽  
Cold Zone ◽  
Thermal Bar ◽  
Simple Theoretical Model ◽  
Theoretical Predictions ◽  
Zone Ii

A simple theoretical model of the thermal bar is derived on the basis of heat budget equations for the following three zones of a wedge-shaped water basin warmed from above: (i) stably stratified shallow warm-water zone; (ii) vicinity of the bar; (iii) convectively mixed deep cold zone. In contrast to the traditional approach, advective warming of the vicinity of the bar and associated facilitating of the thermal bar propagation are taken into account. Theoretical predictions are compared with the data of lacustrine and laboratory measurements taken from current literature. New laboratory experiments have been carried out to examine the laminar regime of the thermal bar.

The evolution of a perturbed vortex in a pipe to axisymmetric vortex breakdown

1998 ◽  
Vol 366 ◽  
pp. 211-237 ◽  
Author(s):  
Z. RUSAK ◽  
S. WANG ◽  
C. H. WHITING
Keyword(s):  
Vortex Breakdown ◽  
Swirling Flow ◽  
Nonlinear Ordinary Differential Equation ◽  
Swirling Flows ◽  
Axisymmetric Vortex ◽  
Burgers Vortex ◽  
Theoretical Predictions ◽  
Necessary And Sufficient Criteria ◽  
High Reynolds ◽  
Necessary And Sufficient

The evolution of a perturbed vortex in a pipe to axisymmetric vortex breakdown is studied through numerical computations. These unique simulations are guided by a recent rigorous theory on this subject presented by Wang & Rusak (1997a). Using the unsteady and axisymmetric Euler equations, the nonlinear dynamics of both small- and large-amplitude disturbances in a swirling flow are described and the transition to axisymmetric breakdown is demonstrated. The simulations clarify the relation between our linear stability analyses of swirling flows (Wang & Rusak 1996a, b) and the time-asymptotic behaviour of the flow as described by steady-state solutions of the problem presented in Wang & Rusak (1997a). The numerical calculations support the theoretical predictions and shed light on the mechanism leading to the breakdown process in swirling flows. It has also been demonstrated that the fundamental characteristics which lead to vortex instability and breakdown in high-Reynolds-number flows may be calculated from considerations of a single, reduced-order, nonlinear ordinary differential equation, representing a columnar flow problem. Necessary and sufficient criteria for the onset of vortex breakdown in a Burgers vortex are presented.

scholarly journals Estimation of Squeeze-Film Damping and Inertial Coefficients from Experimental Free-Decay Data

1986 ◽  
Vol 200 (2) ◽  
pp. 123-133 ◽  
Author(s):  
J B Roberts ◽  
R Holmes ◽  
P J Mason
Keyword(s):  
Linear Model ◽  
Transient Response ◽  
Parametric Identification ◽  
Squeeze Film ◽  
Decay Data ◽  
Operating Range ◽  
Response Data ◽  
Squeeze Film Damping ◽  
Free Decay ◽  
Theoretical Predictions

This paper describes the results obtained from an experimental programme concerned with a parametric identification of the damping and inertial coefficients of a cylindrical squeeze-film bearing, through an analysis of transient response data. The results enable the operating range for which a linear model of the squeeze-film is appropriate to be determined. Comparisons are made between the estimated coefficients and theoretical predictions.

scholarly journals Experimental and numerical studies of an eastward jet over topography

2001 ◽  
Vol 438 ◽  
pp. 129-157 ◽  
Author(s):  
YUDONG TIAN ◽  
ERIC R. WEEKS ◽  
KAYO IDE ◽  
J. S. URBACH ◽  
CHARLES N. BAROUD ◽  
...  
Keyword(s):  
Parameter Space ◽  
Laboratory Experiments ◽  
Multiple Equilibria ◽  
Low Frequency ◽  
Zonal Flow ◽  
Azimuthal Velocity ◽  
Flow Patterns ◽  
Initial State ◽  
Similar Frequency ◽  
Zonal Flows

Motivated by the phenomena of blocked and zonal flows in Earth's atmosphere, we conducted laboratory experiments and numerical simulations to study the dynamics of an eastward jet flowing over wavenumber-two topography. The laboratory experiments studied the dynamical behaviour of the flow in a barotropic rotating annulus as a function of the experimental Rossby and Ekman numbers. Two distinct flow patterns, resembling blocked and zonal flows in the atmosphere, were observed to persist for long time intervals.Earlier model studies had suggested that the atmosphere's normally upstream- propagating Rossby waves can resonantly lock to the underlying topography, and that this topographic resonance separates zonal from blocked flows. In the annulus, the zonal flows did indeed have super-resonant mean zonal velocities, while the blocked flows appear subresonant. Low-frequency variability, periodic or irregular, was present in the measured time series of azimuthal velocity in the blocked regime, with dominant periodicities in the range of 6–25 annulus rotations. Oscillations have also been detected in zonal states, with smaller amplitude and similar frequency. In addition, over a large region of parameter space the two flow states exhibited spontaneous, intermittent transitions from the one to the other.We numerically simulated the laboratory flow geometry in a quasi-geostrophic barotropic model over a similar range of parameters. Both flow regimes, blocked and zonal, were reproduced in the simulations, with similar spatial and temporal characteristics, including the low-frequency oscillations associated with the blocked flow. The blocked and zonal flow patterns are present over wide ranges of forcing, topographic height, and bottom friction. For a significant portion of parameter space, both model flows are stable. Depending on the initial state, either the blocked or the zonal flow is obtained and persists indefinitely, showing the existence of multiple equilibria.

scholarly journals An introduction to the mechanics of the lasso

2014 ◽  
Vol 470 (2171) ◽  
pp. 20140512 ◽  
Author(s):  
Pierre-Thomas Brun ◽  
Neil Ribe ◽  
Basile Audoly
Keyword(s):  
Boundary Layer ◽  
Horizontal Plane ◽  
Laboratory Experiments ◽  
String Model ◽  
Line Tension ◽  
Static Friction ◽  
The Other ◽  
Numerical Continuation ◽  
The World ◽  
Small Loop

Trick roping evolved from humble origins as a cattle-catching tool into a sport that delights audiences all over the world with its complex patterns or ‘tricks’. Its fundamental tool is the lasso, formed by passing one end of a rope through a small loop (the honda) at the other end. Here, we study the mechanics of the simplest rope trick, the Flat Loop , in which the rope is driven by the steady circular motion of the roper's hand in a horizontal plane. We first consider the case of a fixed (non-sliding) honda. Noting that the rope's shape is steady in the reference frame rotating with the hand, we analyse a string model in which line tension is balanced by the centrifugal force and the rope's weight. We use numerical continuation to classify the steadily rotating solutions in a bifurcation diagram and analyse their stability. In addition to Flat Loops , we find planar ‘coat-hanger’ solutions, and whirling modes in which the loop collapses onto itself. Next, we treat the more general case of a honda that can slide due to a finite coefficient of friction of the rope on itself. Using matched asymptotic expansions, we resolve the shape of the rope in the boundary layer near the honda where the rope's bending stiffness cannot be neglected. We use this solution to derive a macroscopic criterion for the sliding of the honda in terms of the microscopic Coulomb static friction criterion. Our predictions agree well with rapid-camera observations of a professional trick roper and with laboratory experiments using a ‘robo-cowboy’.

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