The Dam Break Problem For A Hyperconcentrated Suspension

2000 ◽  
Vol 10 (5) ◽  
pp. 224-230 ◽  
Author(s):  
Blaise Nsom
Keyword(s):  
Risk Assessment ◽  
Debris Flows ◽  
Equations Of Motion ◽  
Dam Break ◽  
Solid Particles ◽  
Environmental Engineering ◽  
Theoretical Studies ◽  
Shallow Water Approximation ◽  
Experimental And Theoretical Studies ◽  
Theoretical Results

Abstract A rheological approach of muddy debris flows is presented for environmental engineering and risk assessment purposes. The debris flow is viewed as a hyperconcentrated suspension of non brownian solid particles. Experimental and theoretical studies are presented versus the concentration. The experimental work generally consists in generating the flow of well characterized suspensions by a dam break. Then, the time evolution of the front as well as that of the stage at given position are accurately determined. On the theoretical framework, the viscous equations of motion of the suspension are written with the shallow water approximation, and the asymptotic solution in a non dimensional form is derived. Finally, the experimental and the theoretical results are successfully compared and the limits of this rheological approach is fixed.

scholarly journals MHD-waves in the geomagnetic tail: A review

10.12737/7168 ◽  
2015 ◽  
Vol 1 (1) ◽  
pp. 4-22 ◽  
Author(s):  
Анатолий Леонович ◽  
Anatoliy Leonovich ◽  
Виталий Мазур ◽  
Vitaliy Mazur ◽  
Даниил Козлов ◽  
...  
Keyword(s):  
Numerical Models ◽  
Experimental Studies ◽  
Low Frequency ◽  
Detailed Comparison ◽  
Mhd Waves ◽  
Theoretical Studies ◽  
Geomagnetic Tail ◽  
Magnetopause Oscillations ◽  
Experimental And Theoretical Studies ◽  
Theoretical Results

This article presents the review of experimental and theoretical studies on ultra-low-frequency MHD oscillations of the geomagnetic tail. We consider the Kelvin–Helmholtz instability at the magnetopause, oscillations with a discrete spectrum in the “magic frequencies” range, the ballooning instability of coupled Alfvén and slow magnetosonic waves, and “flapping” oscillations of the current sheet of the geomagnetic tail. Over the last decade, observations from THEMIS, CLUSTER and Double Star satellites have been of great importance for experimental studies. The use of several spacecraft allows us to study the structure of MHD oscillations with high spatial resolution. Due to this, we can make a detailed comparison between theoretical results and those obtained from multi-spacecraft studies. To make such comparisons in theoretical studies, in turn, we have to use the numerical models closest to the real magnetosphere.

scholarly journals Impact Force of a Geomorphic Dam-Break Wave against an Obstacle: Effects of Sediment Inertia

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 232
Author(s):  
Cristiana Di Cristo ◽  
Massimo Greco ◽  
Michele Iervolino ◽  
Andrea Vacca
Keyword(s):  
Impact Force ◽  
Dam Break ◽  
Solid Particles ◽  
Physical Damage ◽  
Two Phase ◽  
Rigid Obstacle ◽  
Shallow Water Approximation ◽  
Set Up ◽  
The Impact

The evaluation of the impact force on structures due to a flood wave is of utmost importance for estimating physical damage and designing adequate countermeasures. The present study investigates, using 2D shallow-water approximation, the morphodynamics and forces caused by a dam-break wave against a rigid obstacle in the presence of an erodible bed. A widely used coupled equilibrium model, based on the two-dimensional Saint–Venant hydrodynamic equations combined with the sediment continuity Exner equation (SVEM), is compared with a more complex two-phase model (TPM). Considering an experimental set-up presented in the literature with a single rigid obstacle in a channel, two series of tests were performed, assuming sand or light sediments on the bottom. The former test is representative of a typical laboratory experiment, and the latter may be scaled up to a field case. For each test, two different particle diameters were considered. Independently from the particle size, it was found that in the sand tests, SVEM performs similarly to TPM. In the case of light sediment, larger differences are observed, and the SVEM predicts a higher force of about 26% for both considered diameters. The analysis of the flow fields and the morphodynamics shows these differences can be essentially ascribed to the role of inertia of the solid particles.

scholarly journals STUDIES OF PHOTOIONIZATION PROCESSES OF NITROGEN-LIKE O+ION USINGTHE SCREENING CONSTANT BY UNIT NUCLEAR CHARGEMETHOD

2021 ◽  
Vol 9 (09) ◽  
pp. 977-985
Author(s):  
Babou Diop ◽  
◽  
Abdou Diouf ◽  
Youssou Gning ◽  
Maurice Faye ◽  
...  
Keyword(s):  
Experimental Data ◽  
Metastable State ◽  
Effective Charge ◽  
Nuclear Charge ◽  
Theoretical Studies ◽  
Rydberg Series ◽  
Screening Constant ◽  
Semi Empirical ◽  
Experimental And Theoretical Studies ◽  
Theoretical Results

In this present work, we have calculated the energies positions of the 2s22p2(1D)nd2P, 2s22p2(1D)nd2S, 2s22p2(1D)ns 2D, 2s22p2(1S)nd2D and 2s2p3(3P)np2D Rydberg series in the photoionization spectra from the 2P° metastable state of the O+ ion. Calculations were performed up to n = 40 applyingthe Screening Constant by Unit Nuclear Charge (SCUNC) via its semi empirical formalism. The quantum defect and the effective charge are also calculated.The results agree within 98% to Aguilars experimental data, and with Sows theoretical results to within 99%. These data can be a useful guideline for future experimental and theoretical studies.

Reducing the harmful emissions and porous pollutions while combustion of water-fuel emulsions

2020 ◽  
Vol 5 (2) ◽  
pp. 62-74
Author(s):  
Victoria S. Kornienko ◽  
◽  
Roman M. Radchenko ◽  
Dariusz Mikielewicz 2 ◽  
Dmytro V. Konovalov ◽  
...  
Keyword(s):  
Complex System ◽  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Solid Particles ◽  
Theoretical Studies ◽  
Gas Cleaning ◽  
Cleaning Method ◽  
Harmful Emissions ◽  
Experimental And Theoretical Studies

Based on the experimental and theoretical studies, a scheme of system for complex gas cleaning method of an internal combustion engine was developed. This system reduces the content of NOx in gases by 55%, SO2 by 50%, and the content of solid particles by 3 times. The use of a complex system ensures that gases are purified from toxic ingredients and heat emissions to the level recommended by IMO.

Experimental and theoretical studies on the nucleofugality ratio in the aminolysis reactions of O-(4-cyanophenyl) O-(3-nitrophenyl) thionocarbonate with amines in aqueous ethanol

2017 ◽  
Vol 41 (18) ◽  
pp. 9954-9962 ◽  
Author(s):  
Rodrigo Montecinos ◽  
Margarita E. Aliaga ◽  
Paulina Pavez ◽  
José G. Santos
Keyword(s):  
Aqueous Ethanol ◽  
Water Molecules ◽  
Theoretical Studies ◽  
Experimental And Theoretical Studies ◽  
Theoretical Results

The title thionocarbonate reacts with amines to form 4-cyanophenol and 3-nitrophenol in a 1.5 : 1 ratio. Theoretical results show that the products ratio depends on the microsolvation of the water molecules.

scholarly journals STUDY OF THE PASTE-LIKE PROPELLANT COMBUSTION AT VARIOUS LOADING SCHEMES

2020 ◽  
pp. 89-101
Author(s):  
Viktor V. BURKIN ◽  
◽  
Aleksey S. D’YACHKOVSKIY ◽  
Aleksandr N. ISHCHENKO ◽  
Vladimir Z. KASIMOV ◽  
...  
Keyword(s):  
Maximum Pressure ◽  
Theoretical Studies ◽  
Powder Charge ◽  
Propellant Combustion ◽  
Dispersion Law ◽  
Different Types ◽  
Propellant Charge ◽  
The Mathematical Model ◽  
Experimental And Theoretical Studies ◽  
Theoretical Results

The experimental and theoretical studies of the paste-like propellant combustion in a model ballistic installation are implemented. The research is carried out using three masses of projectile assemblies and three types of the propellant charge. The paper presents two versions of the law of dispersion for paste-like propellants which allow accounting for the pressure on the front and acceleration of the projectile assembly with a traveling charge. The coefficients in the laws of dispersion are obtained. Using the mathematical model presented in this work, the gas-dynamic pictures of the shots when the propellants are applied as traveling charges are obtained for each dispersion law. Based on the results, a detailed study of the processes occurring with the traveling charge consisting of a model paste-like propellant is implemented for various shot arrangements. The discrepancy between theoretical results and the results obtained in the set of experiments is no more than 2% for the maximum pressure and no more than 1% for the muzzle velocity. The dispersion law accounting for the projectile assembly acceleration and traveling charge makes it possible to describe accurately the processes in the space behind the projectile for projectile assemblies of various masses and different types of granulated powder charge in terms of the model ballistic installation in the considered pressure range.

The Stabilizing Effect of Pre-Equilibria: A Trifluoromethyl Complex as CF2 Reservoir in Catalytic Olefin Difluorocarbenation

2020 ◽  
Author(s):  
Thomas Louis-Goff ◽  
Huu Vinh Trinh ◽  
Eileen Chen ◽  
Arnold L. Rheingold ◽  
Christian Ehm ◽  
...  
Keyword(s):  
High Selectivity ◽  
Side Reactions ◽  
Theoretical Studies ◽  
Attractive Feature ◽  
Catalyst Recovery ◽  
Wide Range ◽  
Stabilizing Effect ◽  
Experimental And Theoretical Studies

A new, efficient, catalytic difluorocarbenation of olefins to give 1,1-difluorocyclopropanes is presented. The catalyst, an organobismuth complex, uses TMSCF<sub>3</sub> as a stoichiometric difluorocarbene source. We demonstrate both the viability and robustness of this reaction over a wide range of alkenes and alkynes, including electron-poor alkenes, to generate the corresponding 1,1-difluorocyclopropanes and 1,1-difluorocyclopropenes. Ease of catalyst recovery from the reaction mixture is another attractive feature of this method. In depth experimental and theoretical studies showed that the key difluorocarbene-generating step proceeds through a bismuth non-redox synchronous mechanism generating a highly reactive free CF<sub>2</sub> in an endergonic pre-equilibrium. It is the reversibility when generating the difluorocarbene that accounts for the high selectivity, while minimizing CF<sub>2</sub>-recombination side-reactions.

Sign in / Sign up

Export Citation Format

Share Document