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RELEVANCE. Vertical cone diffusers are used in various technical applications: heat exchangers, gas cleaning units, boilers, industrial furnaces, dryers, ventilation devices, nozzle systems and others. For their efficient operation, it is necessary to ensure a uniform supply of the working medium to the device, which is determined by the characteristics of the flow in thediffuser. Thus, the study of the aerodynamics of technological devices with conical diffusers is an urgent task for gas-dynamic improvement and the search for ways to control flow characteristics. THE PURPOSE. To establish the evolution of the velocity field along the height of the cylindrical part of the diffuser for different configurations of the supply tubes, and also to determine the magnitude of the change in the intensity of turbulence along the height of the diffuser under different initial conditions based on experimental data on the instantaneous values of the air flow velocity. METHODS. Measurement of instantaneous values of air flow velocity is carried out using a constant temperature hot-wire anemometer. The article provides data on velocity fields and turbulence intensity along the height and along the diameter of the cylindrical part of the diffuser when air is supplied through tubes of different configurations. Feed tubes with cross sections in the form of a circle, a square and an equilateral triangle were used. RESULTS. The article provides a detailed description of the experimental stand (including key geometric dimensions), instrumentation and measurement system, and data processing techniques. The ranges of changes in the initial conditions for the experiments are presented. A comparison of the aeromechanical characteristics of flows in a vertical diffuser when air issupplied through different tube configurations is carried out. CONCLUSION. It is shown that in the diffuser there is a drop in the average velocity upstream, which is typical for all configurations of the supply tubes. It has been established that profiled tubes influence the shape of the velocity field. It was found that the values of turbulence intensity vary from 0.05 to 0.39 (the highest values were typical when air was supplied through profiled tubes). It is shown that the intensity of turbulence has its maximum values at a height of 300-350 mm, which is typical for all investigated tube configurations.

Conical diffusers of various configurations are used in many kinds of technical equipment and manufacturing processes. Therefore, it is a relevant objective to obtain reliable experimental and mathematical data on the aerodynamic characteristics of diffusers. This article presents experimental data on the aerodynamics of stationary flows in a vertical conical diffuser when air is supplied through tubes with various cross sections (circle, square, and triangle). Instantaneous values of air flow velocity are measured with a constant-temperature hot-wire anemometer. Data are obtained on the velocity fields and turbulence intensity along the height and the diameter of the diffuser's cylindrical part when air is supplied through tubes of various configurations. It is established that air supply through profiled tubes has a significant effect on the shape of the velocity field and turbulence intensity in a vertical conical diffuser. For example, higher values of turbulence intensity are typical of air supplied through profiled tubes (the differences reach 50%). A mathematical formulation (linear and exponential equations) of the change in the average speed and intensity of air flow turbulence along the height of the diffuser's cylindrical part for various initial conditions and supply tube configurations is presented. The obtained findings will make it possible to refine mathematical models and update algorithms for engineering the design of diffusers for various engineering processes and pieces of technical equipment. [ABSTRACT FROM AUTHOR]

The paper presents hydraulic analyzes of the water flow of a trapezoidal open channel under the influence of different roughness values. A trapezoidal cross-section of an open channel with a slope of 45o and a channel bottom width of 1.0 m was considered. Three cases of canal finishing as a function of Manning’s roughness coefficient (n) were analyzed for a concrete canal, a canal made of compacted clay covered with a broken layer of mud, and a canal in very poor condition with large stones on the bottom overgrown with vegetation. The longitudinal channel drop for all analyzed cases is 1%. For the needs of this work, a hydraulic calculation was made for a uniform stationary flow of the trapezoidal cross-section of the channel. Lower pro-accuracy in the channel is given by higher roughness coefficients and vice versa. When dimensioning the canal, it is neces-sary to choose the appropriate finish of the canal from the aspect of throughput as well as the speed of water flow. [ABSTRACT FROM AUTHOR]

In this paper we continue our analysis of the stationary flows of M component, coupled KdV (cKdV) hierarchies and their modifications. We describe the general structure of the t 1 and t 2 flows, using the case M = 3 as our main example. One of our stationary reductions gives N degrees of freedom, superintegrable systems. When N = 1 (for t 1) and N = 2 (for t 2), we have Poisson maps, which give multi-Hamiltonian representations of the flows. We discuss the general structure of these Poisson tensors and give explicit forms for the case M = 3. In this case there are 3 modified hierarchies, each with 4 Poisson brackets. The stationary t 2 flow (for N = 2) is separable in parabolic coordinates. Each Poisson bracket has rank 4, with M + 1 Casimirs. The 4 × 4 "core" of the Poisson tensors are nonsingular and related by a "recursion operator". The remaining part of each tensor is built out of the two commuting Hamiltonian vector fields, depending upon the specific Casimirs. The Poisson brackets are generalised to include the entire class of potential, separable in parabolic coordinates. The Jacobi identity imposes specific dependence on some parameters, representing the Casimirs of the extended canonical bracket. This general case is no longer a stationary cKdV flow, with Lax representation. We give a recursive procedure for constructing the Lax representation of the stationary flow for all values of M , without having to go through the stationary reduction. [ABSTRACT FROM AUTHOR]

The spectrum of various methods and tools used for solving bioengineering problems is sufficiently wide. Dynamical systems (including the symbolic ones) in many cases become a base for design and implementation of methods of investigation and computer modeling complex processes. Whereas for solving direct problems we have many well-developed methods, results for inverse problems are much more modest. We discuss two methods for such tasks: Takens’ method for reconstruction attractor by a time series, and the based on ideas of symbolic dynamics method for digital image analysis using stationary flow on graph and weighted entropy. The results of numerical experiments are given. [ABSTRACT FROM AUTHOR]

We study the problem of the linear stability of stationary plane-parallel shear flows of an inviscid stratified incompressible fluid in the gravity field between two fixed impermeable solid parallel infinite plates with respect to plane perturbations in the Boussinesq approximation and without it. For both cases, we construct some analytical examples of steady plane-parallel shear flows of an ideal density-heterogeneous incompressible fluid and small plane perturbations in the form of normal waves imposed on them, whose asymptotic behavior proves that these perturbations grow in time regardless of whether the well-known result of spectral stability theory (the Miles Theorem) is valid or not. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Chongqing University of Posts & Telecommunications (Natural Science Edition) is the property of Chongqing University of Posts & Telecommunications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thanks to found radial solutions of polynomial partial differential equations, the uniqueness of the Stokes hydrodynamic solution has been proven for the problem of calculating the resistance force of a sphere in a viscous medium. [ABSTRACT FROM AUTHOR]

For a real solution (u, p) to the Euler stationary equations for an ideal fluid, we derive an infinite series of the orthogonality relations that equate some linear combinations of mth degree integral momenta of the functions uiuj and p to zero (m = 0, 1,... ). In particular, the zeroth degree orthogonality relations state that the components ui of the velocity field are L2-orthogonal to each other and have coincident L2-norms. Orthogonality relations of degree m are valid for a solution belonging to a weighted Sobolev space with the weight depending on m. [ABSTRACT FROM AUTHOR]

Copyright of Radio Electronics, Computer Science, Control is the property of Zaporizhzhia National Technical University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Radio Electronics, Computer Science, Control is the property of Zaporizhzhia National Technical University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Los dispositivos de alta energía son diseñados para que funcionen con campos eléctricos y magnéticos extrema-damente altos. Debido a esto, dichos dispositivos presentan fenómenos y comportamientos no lineales, como el aislamiento magnético que altera el transporte de los electrones. La no linealidad ha obligado a analizar y revisar desde el punto de vista matemático las condiciones de frontera y las soluciones del problema. El objetivo de este trabajo es exponer el tema a un nivel que facilite su difusión entre la comunidad académica no familiarizada con el mismo. Para ello, el trabajo presenta una descripción de los fenómenos que se generan cuando hay campos eléctricos y magnéticos muy altos, tomando el caso de un diodo plano al vacío, así como las ecuaciones que modelan el fenómeno de aislamiento magnético; también demuestra la existencia de las soluciones y encuentra las positivas en base a los métodos de solución superior e inferior para problemas de valor de frontera, y pro-porciona algunos ejemplos de aplicación del fenómeno de aislamiento magnético.

Stationary flow bench testing is a standard experimental methodology used by the automotive industry to characterize a cylinder head. In order to reduce the development time, the use of a CFD-based virtual test bench is nowadays a standard practice too. The use of a conventional RANS methodology for the simulation of the flow through the ducts of an engine head allows to get only the mean flow variables distributions because the time average of the generic flow variable fluctuation is zero by definition, but the fluid-dynamics of a stationary flow bench is not really stationary due to the flow instability induced by the duct design and the interaction between valve jets in a multi-duct head. In order to obtain an in-depth knowledge of the fluid-dynamics of a stationary flow bench test rig a LES simulation of a heavy duty DI diesel engine head with two intake ducts, for which experimental data was available, has been carried out using OpenFOAM®. The comparison between LES, experimental and conventional RANS results widened the understanding of the test-bench fluid-dynamics and of the swirl generation process. Due to the high computational cost of the LES approach, the outcomes of this latter have been also used to evaluate potential accuracy improvements of the RANS simulation, namely using a model sensible to flow anisotropies and curvatures such as a RSTM model. The simulation with the new turbulence model has been carried out and compared with the previous results demonstrating predictive improvements with an affordable computational cost for industrial routine usage. [ABSTRACT FROM AUTHOR]

In this paper we formulate the dual variational principle for a problem of stationary flow of a viscous fluid in a pipe with transversal section in the L-form represented by a second elliptic equation with Dirichlet boundary conditions. [ABSTRACT FROM AUTHOR]

Stability of a stationary plane-parallel convective flow of viscoplastic fluid between two differentially heated vertical rigid plates is studied. It has been found that, as in the case of Newtonian fluid, depending on the Prandtl number value, the hydrodynamic monotonic perturbations (vortices at the boundary of counter-flows) or oscillatory thermal perturbations (thermal waves) are responsible for the onset of instability. Stability maps in the Grashof number–Prandtl number plane are obtained for different values of the yield stress. It has been shown that for large Prandtl number values typical for viscoplastic fluids the oscillatory thermal perturbations are most dangerous. Two-dimensional non-linear regimes of convection are studied numerically by the finite difference method. [ABSTRACT FROM AUTHOR]

In this paper we present an example of numerical computation of the motion of the air which goes over a mountain and, according to humidity, causes different quantities of condensation and different variations of temperature. The result of computation coincides satisfactorily with the theoretical values and those of observation. [ABSTRACT FROM AUTHOR]

Economic reasons and the regulation of gas markets create a growing need for mathematical optimization of natural gas networks. Real life planning tasks often lead to highly complex and extremely challenging optimization problems whose numerical treatment requires a breakdown into several simplified problems to be solved by carefully chosen hierarchies of models and algorithms. This paper presents stationary NLP type models of gas networks that are primarily designed to include detailed nonlinear physics in the final optimization steps for mid term planning problems after fixing discrete decisions with coarsely approximated physics. [ABSTRACT FROM AUTHOR]

Abstract: The derivation of macroscopic models for particle-laden gas flows is reviewed. Semi-implicit and Newton-like finite element methods are developed for the stationary two-fluid model governing compressible particle-laden gas flows. The Galerkin discretization of the inviscid fluxes is potentially oscillatory and unstable. To suppress numerical oscillations, the spatial discretization is performed by a high-resolution finite element scheme based on algebraic flux correction. A multidimensional limiter of TVD type is employed. An important goal is the efficient computation of stationary solutions in a wide range of Mach numbers. This is a challenging task due to oscillatory correction factors associated with TVD-type flux limiters and the additional strong nonlinearity caused by interfacial coupling terms. A semi-implicit scheme is derived by a time-lagged linearization of the nonlinear residual, and a Newton-like method is obtained in the limit of infinite CFL numbers. The original Jacobian is replaced by a low-order approximation. Special emphasis is laid on the numerical treatment of weakly imposed boundary conditions. It is shown that the proposed approach offers unconditional stability and faster convergence rates for increasing CFL numbers. The strongly coupled solver is compared to operator splitting techniques, which are shown to be less robust. [Copyright &y& Elsevier]

The linear stability problem is under study for steady axisymmetric translational flows of a density-homogeneous nonviscous incompressible ideal conducting fluid with free surface and “frozen-in” poloidal magnetic field. By the direct Lyapunov method, some sufficient conditions are obtained for the stability of these flows under small long-wave perturbations with the same symmetry. These stability conditions have partial converses; and, for unstable stationary flows, an a priori exponential lower bound is constructed on the growth of small perturbations under consideration, while the increment of the appearing exponent serves as an arbitrary positive parameter. An illustrative analytical example is given of steady flows with superimposed small long-wave axisymmetric perturbations growing in time in accordance with the estimate. [ABSTRACT FROM AUTHOR]