Spatiotemporal Diurnal Modulation Characteristic of Wind Speed and Power Generation Revealed by Its Actual Measurement Data Information Processing

Atmospheric turbulence is an intrinsic factor that causes uncertainty of wind speed and its power generation by wind turbine. The research of atmospheric turbulence characteristics of wind farms can be used to reduce this uncertainty. In this paper, enough measurement data getting from actual wind farms is used for information processing to quantitatively analyze the daily variation of wind speed and its power output characteristics. Furthermore, the concept of spatiotemporal diurnal modulation characteristics of atmospheric turbulence is proposed with a global scope, which is an intrinsic property of wind. Besides the daily weather processes, the average hourly wind speed has a short-term modulation effect on its turbulence and provides a modulation characteristic on wind speed uncertainty. Moreover, the long-term modulation process is affected by seasonal and regional factors, indicating that it has spatiotemporal characteristics. This atmospheric turbulence characteristic has similar effects on characteristic description parameters. However, the characteristics description parameters of wind speed and wind power variation fail to reflect such intrinsic characteristics that are not affected by the spatiotemporal diurnal modulation characteristics of atmospheric turbulence. This indicates that they do not have diurnal characteristics. Finally, the application of spatiotemporal diurnal modulation characteristics on the evaluation of frequency control in power systems is discussed. The results show that this method can effectively improve the power generation quality of large-scale wind power.

EVALUATION OF THE DYNAMICS OF DEVELOPMENT OF THE EXTERNAL ENVIRONMENT OF THE INDUSTRIAL ENTERPRISE IN THE CONDITIONS OF INNOVATIVE ECONOMY

The turbulence characteristic of the modern economy opens up new market "windows", the potential of which can be used by innovatively active agents. The development of the external environment determines the nature, stability, progress and type of trajectory of the functioning of industrial enterprises. When studying the external environment, it is important to study the trends that are emerging not only in the national economy as a whole, but also in its individual subsystems, taking into account the disproportionality of their development characteristic of Russia. The article proposes a quantitative assessment of the characteristics of the dynamics of development of the federal districts of the Russian Federation that are significant in the conditions of an innovative economy, based on an assessment of the rank correlation coefficients and variations of the volume of innovative products, the cost of technological innovation, and the innovative activity of organizations. An assessment of the tightness of the relationship between the cost of technological innovation and the volume of manufactured innovative products in the federal districts of the Russian Federation is carried out. The article identifies federal districts, the external environment of which is favorable for modernization and increasing the efficiency of enterprises, and districts in which the introduction of innovative trajectories in the development strategy of enterprises is difficult.

Heat Transfer in Highly Turbulent Separated Flows: A Review

The study of flows with a high degree of turbulence in boundary layers, near-wall jets, gas curtains, separated flows behind various obstacles, as well as during combustion is of great importance for increasing energy efficiency of the flow around various elements in the ducts of gas-dynamic installations. This paper gives some general characteristics of experimental work on the study of friction and heat transfer on a smooth surface, in near-wall jets, and gas curtains under conditions of increased free-stream turbulence. Taking into account the significant effect of high external turbulence on dynamics and heat transfer of separated flows, a similar effect on the flow behind various obstacles is analyzed. First of all, the classical cases of flow separation behind a single backward-facing step and a rib are considered. Then, more complex cases of the flow around a rib oriented at different angles to the flow are analyzed, as well as a system of ribs and a transverse trench with straight and inclined walls in a turbulent flow around them. The features of separated flow in a turbulized stream around a cylinder, leading to an increase in the width of the vortex wake, frequency of vortex separation, and increase in the average heat transfer coefficient are analyzed. The experimental results of the author are compared with data of other researchers. The structure of separated flow at high turbulence—characteristic dimensions of the separation region, parameters of the mixing layer, and pressure distribution—are compared with the conditions of low-turbulent flow. Much attention is paid to thermal characteristics: temperature profiles across the shear layer, temperature distributions over the surface, and local and average heat transfer coefficients. It is shown that external turbulence has a much stronger effect on the separated flow than on the boundary layer on a flat surface. For separated flows, its intensifying effect on heat transfer is more pronounced behind a rib than behind a step. The factor of heat transfer intensification by external turbulence is most pronounced in the transverse cavity and in the system of ribs.

Investigation into the turbulence statistics of installed jets using hot-wire anemometry

This work presents a detailed study of the turbulence flow statistics of a jet mounted with its axis parallel to a rigid flat plate. Hot-wire constant temperature anemometry has been used to measure the single-point and two-point statistics of the axial velocity component at several locations within the jet flow field. Results show that the jet mean flow near the plate surface is subjected to a local acceleration and redirection due to a Coandă-type effect. The propagation of these effects downstream of the plate trailing edge is strongly dependent on the plate position. Regarding the velocity fluctuations, the mean turbulence intensity levels are seen to decrease as the radial distance between the jet and surface decreases. Analysis of the single-point power spectral density data on the shear layer close to the plate shows that the reduction in magnitude of the low-frequency content of the energy spectrum is responsible for the decrease in turbulence intensity. Additionally, the characteristic time and length scales computed from two-point measurements reduce as the plate is mounted closer to the jet centre-line. The axial eddy convection velocity is seen to increase in the region of high turbulent kinetic energy in the shear layer adjacent to the surface. Empirical models for turbulence characteristic scales and eddy convection velocity are presented. These findings suggest that both the amplitude and distribution of the jet mixing noise sources are affected when closely installed next to a surface. This paper is a continuation of a recent investigation on the turbulence statistics of isolated jets presented in Proença (Exp Fluids 60(4):63, 2019). Graphic abstract

Assessing decoupling of above and below canopy air masses at a Norway spruce stand in complex terrain

<p>Concurrent below (0.14 • canopy height) and above canopy sonic anemometer vertical velocity (w) measurements reveal frequent decoupling events between the air masses below and above the canopy at a dense spruce forest stand in mountainous terrain. Decoupling events occurred predominantly during nighttime but not exclusively. Several single-level approaches based on steady state and integral turbulence characteristic tests as well as u<sub>*</sub> filtering and two-level CO<sub>2</sub> flux filtering methods are tested. These tests aimed at evaluating the filtering schemes to address decoupling and its effect on above canopy derived eddy covariance CO<sub>2</sub> fluxes. In addition to the already existing two-level filtering approach based on the correlation of σ<sub>w</sub> above and below canopy, two new filtering methods are introduced based on w raw data below and above the canopy. One is a telegraphic approximation agreement, which assumes coupling when w both above and below canopy are pointing in the same direction. Another one evaluates the cross correlation maximum between below and above canopy w data. This study suggests that none of the single-level approaches can detect decoupling when compared to two-level filtering approaches. It further suggests that the newly introduced two-level approaches based on w raw data may have advantages in comparison to the conventional σ<sub>w</sub> approach regarding their flexibility on shorter time scales than one year. We tested the correlation of the newly introduced filtering approaches with the parameters u<sub>*</sub>, global radiation, buoyancy forcing across the canopy and wind shear across the canopy. In any case, this correlation was not existing or weakly positive, suggesting that concurrent below and above canopy measurements are mandatory for addressing decoupling sufficiently. Sonic anemometer measurements near the forest floor and above the canopy are sufficient to apply the new procedures and can be implemented in a routine manner at any forest site globally.</p>

Study on Gust Parameters and Wind Spectrum of South China Sea

Wind loads are one of the main loads on offshore structures during typhoons in the South China Sea (SCS). The accuracy of wind turbulence characteristic parameters were very important for the calculation of wind load of these large structures and floating platforms. The parameters of the gust factor and wind spectra are studied in this paper. Characteristics of the gust factor and the turbulence during typhoon and monsoon period were analyzed by using the observational data of long-term wind on a platform in South China Sea. The relationships among the gust factor, mean wind speed and turbulence intensity were described. The most suitable wind spectrum for SCS had been compared for the different wind speed conditions. The results can provide reference and technical guarantee for the offshore constructions of SCS.

Turbulence Characteristic of Flow Near Laboratory Experiment Groin Fields

Groin is hydraulic structure utilized to protect riverbank from erosion. Groin will shift away flow. Area just downstream of groin structure will be occupied by low velocity flow hence there will be sediment deposition. Turbulence mechanism between primary flow region and groin field having important role in sediment exchange needs to be investigated. Instantaneous flow measurement was conducted in order to investigate turbulence relation between series groin under various groin spacing. Laboratory experiment employed turbulence flow having Reynolds number range between 31,935-32,500 and Froude number range between 0.051-0.053. A MicroADV 16-MHz was used to measure 3D instantaneous velocity. The experiment findings expressed that Reynolds stress involving vertical velocity and did not show any specific distributions except at the lowest measurement elevation, while Reynolds stress showed specific distributions. Turbulence value difference between groin field and primary flow region at upstream of the groin field was significant. As the area was getting downstream, area containing high turbulence was wider. This work indicated that bed shear stress value tended to grow at downstream area of groin field. High difference bed shear stress value between primary flow region and groin field seized second groin field and third groin field.

Agroholdings, turbulence, and resilience: The case of Ukraine

The agricultural sector in transitional and emerging market economies is marked by the prominence of agroholdings, i.e., conglomerates of agricultural enterprises controlling up to hundreds of thousands of hectares of farmland. Drawing on secondary information from Ukraine, this paper explores how institutional turbulence gives rise to agroholdings. The key hypothesis is that membership in an agroholding presents a strategy for agricultural enterprises to remain resilient in the midst of the severe institutional turbulence characteristic of a transitional economy. The focus on resilience provides a tentative explanation of why the remarkable growth of agroholdings fails to be accompanied by evidence of their superior efficiency.