Hydroelectric power belongs to renewable energy sources and contributes a considerable percentage of the electrical energy generated in the world. Its advantages include no carbon dioxide emission, ...excellent maneuverability, and high energy effectiveness. However, disadvantages do also exist caused by the influence of hydropower facilities on the bioenvironment. This paper presents a review of the most characteristic effects of elements of the flow path of hydroturbines during their operation on biofauna (fish and plankton). The most popular design solutions are examined, which are aimed at reducing the risk of negative impact of the elements of the flow path of hydraulic turbines on the bioenvironment. Obviously, the implementation of these solutions will deteriorate the performance of hydraulic turbines. However, we should bear in mind that the main purpose of these solutions is to ensure the biological safety of facilities, while their energy characteristics do not receive proper attention. The paper presents in some detail an option for rendering environmental safety, which is the modernization of the runner hub by eliminating the gaps between the blades and the hub. Numerical simulation has revealed that the application of a runner with the modified hub increases the hydraulic resistance, decreases the flowrate, and, as a result, reduces the generated power. An analysis of the simulation results has suggested that, despite some decrease in the energy characteristics, it seems worthwhile to develop biologically safer flow path design versions. In addition, a conclusion has been made that the flow path can be further modified to compensate for power losses.
An extensive experimental investigation of two receptivity mechanisms of localized excitation of unsteady (in general) Cross-Flow (CF) instability modes in a three-dimensional (3D) swept-airfoil ...boundary layer has been carried out within one extended set of measurements. Two mechanisms of the boundary-layer receptivity have been investigated: (i) to surface nonuniformities (vibrations, in general) and (ii) to scattering of freestream vortices on surface nonuniformities. All obtained results are deeply processed and analyzed. Part 1 of the present study (this paper) is devoted to description of the results obtained for problem (i). Meanwhile, results of detailed investigation of problem (ii) are presented in Part 2 of this study (the next paper Borodulin et al. (2023)).
The article considers the issues of building the software and hardware complex for ensuring natural and technological safety within the framework of the implementation of the Smart City ...digitalization project for the city economy. The purpose of the article is to show the role and place of the complex in the general ecosystem of the city governance. It is concluded that it is necessary to use a regional digital platform for life safety in the Smart City ecosystem that provides information and software pairing of interacting federal, regional, municipal and object information systems, consolidates their information resources, prompt and effective analytical processing of the consolidated information and provides it to interested users on a one-stop basis.
An extensive experimental investigation of two receptivity mechanisms of localized excitation of unsteady (in general) Cross-Flow (CF) instability modes in a three-dimensional (3D) swept-airfoil ...boundary layer has been carried out within one extended set of measurements. Two mechanisms of the boundary-layer receptivity have been investigated: (i) to surface nonuniformities (vibrations, in general) and (ii) to scattering of freestream vortices on surface nonuniformities. All obtained results are deeply processed and analyzed. Part 1 of the present study (Borodulin et al., 2023), was devoted to description of the results obtained for problem (i). Meanwhile, results of detailed investigation of problem (ii) are presented in Part 2 of this study (the present paper).
Abstract
The consumption and temperature of hot water produced by boiler units are calculated using such a quantity as the consumption of the consumed network water. The formulas represent functional ...dependencies connecting the obtained values not only with the consumption of heating water, but also with the consumption of hot water supplied for recirculation, for own needs and for the needs of the fuel economy. They take into account the losses of network and hot water. The formulas are obtained as a result of the joint solution of the equation for the total consumption of hot water and the equation for its partial costs.
A simple laboratory procedure has been proposed for the synthesis of tetracyanoethylene in up to 54% yield by oxidative dimerization of malononitrile in the presence of selenium(IV) oxide.
The subject of the present combined experimental and theoretical investigation is the steady and unsteady linear Görtler instability. The majority of previous experiments were devoted to the steady ...Görtler vortices, despite the unsteady ones are also observed in real transitional flows. Moreover, even for the steady Görtler vortices no quantitative agreement between the experimental and theoretical linear-stability characteristics was obtained, especially for disturbance amplification rates. The experimental difficulties were connected, in particular, with a rather poor accuracy of measurements at zero disturbance frequency, a possible influence of nonlinearity, and an admixture of non-modal (transient) growth mechanism. All these difficulties have been overcome in the experimental part of the present study by means of: (
i) tuning-out of the exact zero frequency of Görtler vortices and working, instead, with quasi-steady perturbations of very low frequencies, (
ii) performing measurements at low disturbance amplitudes, and (
iii) minimization and careful estimation of the disturbance-source near-field by means of utilizing a special controlled disturbance source and performing special numerical computations for exact experimental conditions. A detailed study of all linear-stability characteristics for
essentially unsteady Görtler vortices was performed in this paper as well. The results are obtained in a range of Görtler numbers 13
≲
Gö
≲
17.3, frequency parameters
F = 0.56–22.70, and spanwise wavelength parameters
Λ = 149–775 (close to the most amplified Görtler modes).
Appropriate calculations based on locally-parallel and non-local non-parallel linear-stability theories were performed and compared quantitatively with experimentally obtained linear-stability characteristics. For the first time all stability characteristics measured for steady Görtler vortices (in quasi-steady regimes) are found to agree very well with those calculated for the most amplified first discrete-spectrum mode of the linear Görtler-instability problem. Similar good agreement is obtained for essentially unsteady Görtler vortices. The roles of effects of the base-flow non-parallelism and the disturbance-source near-field are examined.
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