scholarly journals Rayleigh–Taylor turbulent mixing evolution under a shock influence

2000 ◽  
Vol 18 (2) ◽  
pp. 155-161 ◽  
Author(s):  
Yu.A. KUCHERENKO ◽  
A.P. PYLAEV ◽  
V.D. MURZAKOV ◽  
V.N. POPOV ◽  
V.E. SAVEL'EV ◽  
...  
Keyword(s):  
Experimental Study ◽  
Solid Surface ◽  
Turbulent Mixing ◽  
Initial Perturbation ◽  
Density Ratio ◽  
Internal Working ◽  
Metal Plates ◽  
Impulse Duration ◽  
Rayleigh Taylor Instability ◽  
The Impact

At the installation SOM, the experimental study of the impulse acceleration influence on the behavior of the turbulized layer obtained as a result of Rayleigh–Taylor instability (RTI) action on the system of two different density liquids with the density ratio n = 3, has been performed. After application of impulse acceleration the systems were moving according to inertia, and by using the light method the coordinates of penetration of the heavier liquid into the lighter one and vice versa were determined. The liquids studied were placed inside the ampoule that had internal working sizes (54 × 64 × 120) mm3. There were initial accidental perturbations like a rough solid surface at the interface and the width of the initial perturbation zone was L0 = 2.3 mm. The moving ampoule blow against metal plates created the impulse acceleration. The relative impulse acceleration was δg/g11 = 22.2–66.6 where g11 is the ampoule acceleration before the impact, the impulse duration was varied from 0.27 ms to 0.096 ms. The results concerned with the turbulized layer extension after the impulse acceleration action were obtained.

scholarly journals RFNC–VNIITF multifunctional shock tube for investigating the evolution of instabilities in nonstationary gas dynamic flows

2003 ◽  
Vol 21 (3) ◽  
pp. 381-384 ◽  
Author(s):  
Yu.A. KUCHERENKO ◽  
O.E. SHESTACHENKO ◽  
S.I. BALABIN ◽  
A.P. PYLAEV
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Turbulent Mixing ◽  
Wire Array ◽  
Density Ratio ◽  
Initial Pressure ◽  
Taylor Instability ◽  
Interfacial Instability ◽  
Rayleigh Taylor Instability ◽  
Dynamic Flows

The design, operation, and functionality of the multifunctional shock tube (MST) facility at the Russian Federal Nuclear Center–VNIITF are described. When complete, the versatile MST consists of three different driver sections that permit the execution of three different classes of experiments on the compressible turbulent mixing of gases induced by the (1) Richtmyer–Meshkov instability (generated by a stationary shock wave with shock Mach numbers <5), (2) Rayleigh–Taylor instability (generated by compression wave such that acceleration of the interface is <105g0, whereg0= 9.8 m/s2), and (3) combined Richtmyer–Meshkov and Rayleigh–Taylor instability (generated by a nonstationary shock wave with initial pressure at the front 5 × 106Pa and acceleration of ≤106g0of the interface). For each of these types of experiments, the density ratio of the gases is ρ2/ρ1≤ 34. Perturbations are imposed on a thin membrane, embedded in a thin wire array of microconductors that is destroyed by an electric current. In addition, various limitations of experimental techniques used in the study of interfacial instability generated turbulent mixing are also briefly discussed.

Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

2020 ◽  
Vol 92 (3) ◽  
pp. 30901
Author(s):  
Suvanjan Bhattacharyya ◽  
Debraj Sarkar ◽  
Ulavathi Shettar Mahabaleshwar ◽  
Manoj K. Soni ◽  
M. Mohanraj
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Working Fluid ◽  
The Novel ◽  
Heat Exchanger Tube ◽  
Heat Transfer Augmentation ◽  
Corrugated Tube ◽  
The Impact ◽  
Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

scholarly journals Waterfall Algorithm as a tool of investigation the geometrical features of granular porous media

2021 ◽  
Author(s):  
Wojciech Sobieski
Keyword(s):  
Particle Size ◽  
Porous Media ◽  
Lattice Boltzmann ◽  
Granular Media ◽  
Density Ratio ◽  
Geometrical Features ◽  
Granular Porous Media ◽  
Collision Density ◽  
Boltzmann Method ◽  
The Impact

AbstractThe paper describes the so-called Waterfall Algorithm, which may be used to calculate a set of parameters characterising the spatial structure of granular porous media, such as shift ratio, collision density ratio, consolidation ratio, path length and minimum tortuosity. The study is performed for 1800 different two-dimensional random pore structures. In each geometry, 100 individual paths are calculated. The impact of porosity and the particle size on the above-mentioned parameters is investigated. It was stated in the paper, that the minimum tortuosity calculated by the Waterfall Algorithm cannot be used directly as a representative tortuosity of pore channels in the Kozeny or the Carman meaning. However, it may be used indirect by making the assumption that a unambiguous relationship between the representative tortuosity and the minimum tortuosity exists. It was also stated, that the new parameters defined in the present study are sensitive on the porosity and the particle size and may be therefore applied as indicators of the geometry structure of granular media. The Waterfall Algorithm is compared with other methods of determining the tortuosity: A-Star Algorithm, Path Searching Algorithm, Random Walk technique, Path Tracking Method and the methodology of calculating the hydraulic tortuosity based on the Lattice Boltzmann Method. A very short calculation time is the main advantage of the Waterfall Algorithm, what meant, that it may be applied in a very large granular porous media.

scholarly journals Empirical Stochastic Model of Multi-GNSS Measurements

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4566
Author(s):  
Dominik Prochniewicz ◽  
Kinga Wezka ◽  
Joanna Kozuchowska
Keyword(s):  
Stochastic Model ◽  
Density Ratio ◽  
Functional Model ◽  
Optimal Solution ◽  
Global Navigation Satellite Systems ◽  
Unknown Parameters ◽  
Short Baseline ◽  
Stochastic Parameters ◽  
Dependent Model ◽  
The Impact

The stochastic model, together with the functional model, form the mathematical model of observation that enables the estimation of the unknown parameters. In Global Navigation Satellite Systems (GNSS), the stochastic model is an especially important element as it affects not only the accuracy of the positioning model solution, but also the reliability of the carrier-phase ambiguity resolution (AR). In this paper, we study in detail the stochastic modeling problem for Multi-GNSS positioning models, for which the standard approach used so far was to adopt stochastic parameters from the Global Positioning System (GPS). The aim of this work is to develop an individual, empirical stochastic model for each signal and each satellite block for GPS, GLONASS, Galileo and BeiDou systems. The realistic stochastic model is created in the form of a fully populated variance-covariance (VC) matrix that takes into account, in addition to the Carrier-to-Noise density Ratio (C/N0)-dependent variance function, also the cross- and time-correlations between the observations. The weekly measurements from a zero-length and very short baseline are utilized to derive stochastic parameters. The impact on the AR and solution accuracy is analyzed for different positioning scenarios using the modified Kalman Filter. Comparing the positioning results obtained for the created model with respect to the results for the standard elevation-dependent model allows to conclude that the individual empirical stochastic model increases the accuracy of positioning solution and the efficiency of AR. The optimal solution is achieved for four-system Multi-GNSS solution using fully populated empirical model individual for satellite blocks, which provides a 2% increase in the effectiveness of the AR (up to 100%), an increase in the number of solutions with errors below 5 mm by 37% and a reduction in the maximum error by 6 mm compared to the Multi-GNSS solution using the elevation-dependent model with neglected measurements correlations.

Experimental study of heat transfer in the boundary layer of a flat plate with the impact of weak shock waves on the leading edge

2020 ◽  
Author(s):  
V. L. Kocharin ◽  
A. A. Yatskikh ◽  
D. S. Prishchepova ◽  
A. V. Panina ◽  
Yu. G. Yermolaev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Experimental Study ◽  
Shock Waves ◽  
Flat Plate ◽  
Leading Edge ◽  
Weak Shock ◽  
The Impact

An experimental study of Web switching behavior

2003 ◽  
Vol 22 (2) ◽  
pp. 87-93
Author(s):  
James Otto ◽  
Mohammad Najdawi ◽  
William Wagner
Keyword(s):  
Experimental Study ◽  
Electronic Commerce ◽  
Web Site ◽  
Waiting Times ◽  
Switching Behavior ◽  
The Internet ◽  
Wait Times ◽  
Web Page ◽  
Extensive Growth ◽  
The Impact

With the extensive growth of the Internet and electronic commerce, the issue of how users behave when confronted with long download times is important. This paper investigates Web switching behavior. The paper describes experiments where users were subjected to artificially delayed Web page download times to study the impact of Web site wait times on switching behavior. Two hypotheses were tested. First, that longer wait times will result in increased switching behavior. The implication being that users become frustrated with long waiting times and choose to go elsewhere. Second, that users who switch will benefit, in terms of decreased download times, from their decision to switch.

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