Experimental Convergence Rate Study for Three Shock-Capturing Schemes and Development of Highly Accurate Combined Schemes

We study experimental convergence rates of three shock-capturing schemes for hyperbolic systems of conservation laws: the second-order central-upwind (CU) scheme, the third-order Rusanov-Burstein-Mirin (RBM), and the fifth-order alternative weighted essentially non-oscillatory (A-WENO) scheme. We use three imbedded grids to define the experimental pointwise, integral, and $W^{-1,1}$ convergence rates. We apply the studied schemes to the shallow water equations and conduct their comprehensive numerical convergence study. We verify that while the studied schemes achieve their formal orders of accuracy on smooth solutions, after the shock formation, a part of the computed solutions is affected by shock propagation and both the pointwise and integral convergence rates reduce there. Moreover, while the $W^{-1,1}$ convergence rates for the CU and A-WENO schemes, which rely on nonlinear stabilization mechanisms, reduce to the first order, the RBM scheme, which utilizes a linear stabilization, is clearly second-order accurate. Finally, relying on the conducted experimental convergence rate study, we develop two new combined schemes based on the RBM and either the CU or A-WENO scheme. The obtained combined schemes can achieve the same high-order of accuracy as the RBM scheme in the smooth areas while being non-oscillatory near the shocks.Comment: 33 page

Numerical simulation and experimental study of electrostatic field near man with protective polymeric clothing

In the article the mathematical model and the method of numerical calculation, based on the method of finite elements of three-dimensional electrostatic field near-by a man at presence of surface charge on his protective clothing, made from polymeric material, were considered. Experimental researches were conducted to determine the value of the surface charge. The results of numeral calculations of the distribution of electric potential and field intensity, as well as integral value of electric energy, stored in this field, were presented

Engine technical performance influence on car exhaust microparticles grading

Abstract. Present work demonstrates the influence of the engine size, car production year and fuel type on suspended solid particles of the car exhaust. The investigated machine group (N = 21) showed no influence on the particle size distribution caused by engine displacement and type of fuel. It is shown that almost new cars (less than 400 km travelled) are the most frequent source of the particles with an average diameter of about 10 microns or less

Чисельне моделювання та експериментальне дослідження електростатичного поля поблизу людини із захисним полімерним одягом

This is a pre-print of an article published in “Universal Journal of Electrical and Electronic Engineering, Vol. 5(1)”. The final authenticated version is available online at: http://dx.doi.org/10.13189/ujeee.2017.050103.У статті розглянуто математичну модель та метод чисельного розрахунку електростатичного поля поруч людини за наявності поверхневого заряду на його захисному одязі, виготовленого з полімерного матеріалу, заснований на методі скінченних елементів тривимірного. Для визначення величини поверхневого заряду виконано експериментальні дослідження. Представлено результати чисельних розрахунків розподілу електричного потенціалу та напруженості поля, а також інтегрального значення електричної енергії, що накопичується в полі.In the article the mathematical model and the method of numerical calculation, based on the method of finite elements of three-dimensional electrostatic field near-by a man at presence of surface charge on his protective clothing, made from polymeric material, were considered. Experimental researches were conducted to determine the value of the surface charge. The results of numeral calculations of the distribution of electric potential and field intensity, as well as integral value of electric energy, stored in this field, were presented.В статье рассмотрены математическая модель и метод численного расчета трехмерного электростатического поля вблизи человека при наличии поверхностного заряда на его защитной одежде из полимерного материала, основанный на методе конечных элементов. Проведены экспериментальные исследования по определению величины поверхностного заряда. Приведены результаты численных расчетов распределения электрического потенциала и напряженности поля, а также интегрального значения электрической энергии, запасенной в этом поле

Determination of thermal characteristics of combustion products of fire-tube heat generator with flow turbulator

Boiler construction is one of the major industries of any state. The aim is to determine the effect of the turbulator on the intensity of heat transfer in the convective part of the fire-tube heat generator of domestic production. The improvement of convective heating surfaces is one of the ways to increase the energy efficiency of the fire-tube heat generator. Since model of the process of heat transfer of gas flow in the convective tubes is multifactorial and does not have clear analytical solution at present, the study of process above is carried out using the experimental method. The results of applying the flow turbulator as a broken tape in the fire-tube heat generator of KV-GM type are presented. On their basis it can be concluded about increasing of heat transfer in convective part of the unit. The use of efficient, reliable, easy to manufacture, relatively inexpensive turbulator in domestic fire-tube heat generators will allow to increase their energy conversion efficiency and reduce fuel consumption, which will have a positive economic effect

Quantum exceptional group G_2 and its semisimple conjugacy classes

We construct quantization of semisimple conjugacy classes of the exceptional group G = G2 along with and by means of their representations on highest weight modules over the quantum group Uq(g). With every point t of a fixed maximal torus we associate a highest weight module Mt over Uq(g) and realize the quantized polynomial algebra of the class of t by linear operators on Mt . Quantizations corresponding to points of the same orbit of the Weyl group are isomorphic

Antibacterial Effect of Acoustic Cavitation Promoted by Mesoporous Silicon Nanoparticles

As-prepared mesoporous silicon nanoparticles, which were synthesized by electrochemical etching of crystalline silicon wafers followed by high-energy milling in water, were explored as a sonosensitizer in aqueous media under irradiation with low-intensity ultrasound at 0.88 MHz. Due to the mixed oxide-hydride coating of the nanoparticles’ surfaces, they showed both acceptable colloidal stability and sonosensitization of the acoustic cavitation. The latter was directly measured and quantified as a cavitation energy index, i.e., time integral of the magnitude of ultrasound subharmonics. The index turned out to be several times greater for nanoparticle suspensions as compared to pure water, and it depended nonmonotonically on nanoparticle concentration. In vitro tests with Lactobacillus casei revealed a dramatic drop of the bacterial viability and damage of the cells after ultrasonic irradiation with intensity of about 1 W/cm2 in the presence of nanoparticles, which themselves are almost non-toxic at the studied concentrations of about 1 mg/mL. The experimental results prove that nanoparticle-sensitized cavitation bubbles nearby bacteria can cause bacterial lysis and death. The sonosensitizing properties of freshly prepared mesoporous silicon nanoparticles are beneficial for their application in mild antibacterial therapy and treatment of liquid media

(Z)-N-[1-(Aziridin-1-yl)-2,2,2-trifluoroethylidene]-4-bromoaniline

The title compound, C10H8BrF3N2, crystallizes with two independent molecules in the asymmetric unit, which can be considered as being related by a pseudo-inversion center, so their conformations are different; the corresponding N=C—N—C torsion angles are 54.6 (5) and −50.5 (5)°. In the crystal, molecules related by translation in [001] interact through short intermolecular Br...F contacts [3.276 (2) and 3.284 (2) Å], thus forming two types of crystallographically independent chains

2-Bromo-1-[1-(4-bromophenyl)-5-methyl-1H-1,2,3-triazol-4-yl]ethanone

The asymmetric unit of the title compound, C11H9Br2N3O, contains two crystallographically independent molecules with similar geometries; the Br—C—C=O torsion angles are 1.2 (4) and −2.8 (4)°, and the benzene and triazole rings are inclined o one another by 51.90 (16) and 51.88 (16)°. The two molecules are related by a pseudo-screw 21 axis directed along [100]. In the crystal, molecules are linked into a three-dimensional network by weak C—H...O and C—H...N hydrogen bonds and secondary Br...Br [3.5991 (8) and 3.6503 (9) Å] interactions