Evaluation of Surface Layer Stability Functions and Their Extension to First Order Turbulent Closures for Weakly and Strongly Stratified Stable Boundary Layer

In this study, we utilize a generalization of Monin–Obukhov similarity theory to construct first order turbulent closures for single-column models of the atmospheric boundary layer (ABL). A set of widely used universal functions for dimensionless gradients is evaluated. Two test cases based on Large-Eddy Simulations (LES) experimental setups are considered – weakly stable ABL (GABLS1; Beare et al. in Bound Layer Meteorol 118(2):247–272,2006), and very strongly stratified ABL (van der Linden et al. in Bound Layer Meteorol 173(2):165–192, 2019). The comparison shows that approximations obtained using a linear dimensionless velocity gradient tend to match the LES data more closely. In particular, the EFB (Energy- and Flux- Budget) closure proposed by Zilitinkevich et al. (Bound Layer Meteorol 146(3):341–373, 2013) has the best performance for the tests considered here. We also test surface layer “bulk formulas” based on these universal functions. The same LES data are utilized for comparison. The setup showcases the behavior of surface scheme, when one assumes that the velocity and temperature profiles in ABL are represented correctly. The advantages and disadvantages of different surface schemes are revealed

Incipient Regimes of Drill Bit Whirlings on Uneven Bottoms of Deep Bore-Holes

This paper studies the problem of whirl vibrations of rotating drill string bit under conditions of its contact interaction with the bore-hole bottom surface. The destructive effects of whirl vibrations of drill bits and drill strings have long been recognized. The backward whirling is believed to randomly happen to some degree in 40% of all wells. It is shown that the situation is essentially associated with enlargement of the compressive thrust force and its approaching to the Eulerian critical value. Then, the bending stiffness of the drill string reduces, it hogs and the diamond impregnations existing in the bit surface penetrate into the rock medium. As this takes place, the bit axis tilts and nutates. It should be particularly emphasized that at this stage, the bit is under action of the vertical force (weight on bit) which essentially exceeds all other forces. It presses the bit to the hole bottom (not to the hole wall) and the bit loses its ability to slide on the bore-hole bottom and begins to roll on its surface, lagging behind or outstripping the drill string rotation. As a result, the point of the bit contact with the reference surface (the instantaneous centre of velocities) may describe extremely complicated trajectories with loops and cuspidal points and to change the motion directions. As examples, whirling of spherical bit is considered

Collaborative interpretation of the data obtained by resistivity and ground penetrating radar methods for assessing the permeability of sandy clay soils

A method for estimating the filtration factor of sandy clay soils is considered on the basis of a joint interpretation of the data of a set of methods of engineering electrical exploration, including electrical resistivity tomography and ground penetrating radar studies. The solution of this problem is based on the use of known empirical connections between the imaginary and real parts of the complex dielectric permittivity, specific electrical resistance, and Q factor. An example of the effective joint use of the ground penetrating radar and non-contact electrical resistivity tomography shows how to obtain qualitative and quantitative estimates of a changing filtration factor in a draining road layer. It is necessary to use precise engineering geological information in order to provide the required estimates. The proposed approach makes it possible to describe continuous profiles of a pavement and underlying layers by ground penetrating radar and electrical resistivity tomography, as well as to assess soil properties when conducting an electrical survey from the surface of asphalt concrete pavement. Recommendations for the implementation of the developed methods of complex engineering and geophysical research are given for solving issues of repair work design, supervision, and quality control of road construction

Mathematical investigation of pressure pulsations characteristics and natural acoustic frequencies in the gas-dynamic channel

Paper presents a numerical simulation of the occurrence of flow instability and pressure self-oscillations for a complex configuration of the gas-dynamic tract in combustion chamber. Unsteady axisymmetric two-dimensional Navier-Stokes equations are used for mathematical modelling of compressible one-phase medium. To simulate turbulence, the k-ε and LES models were used. Fast Fourier Transform (FFT) determined the frequency spectrum of pressure pulsations in the combustion chamber. It is shown that in the case of a simple geometry of the free gas cavity in combustion chamber, both models of turbulence make it possible to determine the spectrum of the natural acoustic frequencies. Using the LES model in the case of complex geometry makes it possible to predict the hydrodynamic structure of a flow accurately. The flow, in this case, has an intensive vortex generation. Formation of small-scale vortex occurs in the near-wall regions and large eddies in the core of a flow. Frequency of large eddies formation can be combined with the natural acoustic frequencies of combustion chamber and can affect the amplitude of pressure pulsation

To the definition of the concept economic competence of the teacher

Essential signs of the concept of the teacher’s economic competence are determined, and a description of the structure of this competence is offered. The revealed theoretical construct is used as a methodological basis for designing the content of the academic discipline “Economics of Education”Определены существенные признаки понятия «экономическая компетентность педагога», предложено описание структуры этой компетентности. Выявленный теоретический конструкт применяется в качестве методологического основания проектирования содержания учебной дисциплины «Экономика образования

Overcoming cognitive-sensitive barriers in research activities as the condition of development of the methodological culture of a teacher

The phenomen of cognitive-semantic barriers arising in students' research activity is considered. Some ways of overcoming the barriers for the development of the methodological culture of the teacher are suggestedРассмотрен феномен познавательно-смысловых барьеров, возникающих в исследовательской деятельности студентов. Предложены некоторые способы преодоления барьеров для развития методологической культуры педагог

Landscape, Memory, Heritage and Identity (Historiographical Overview)

Introduction. UNESCOs adoption of the Convention “Concerning the Protection of the World Cultural and Natural Heritage” of 1972 led to the discussion on the issues of mutual influence and interdependence of humankind and nature and human perception of the environment and his own ecological niche. As a result of these discussions, the term “cultural landscape” came into use, and became part of the world cultural heritage. Methods and materials. This study is based on the combination of the general, special historical and cultural methods. The central place among them was occupied by the comparative, analytical, historical-genetic, comparative analysis methods and some methods of historical cultural studies. Analysis. The evolution of the cultural landscape took place throughout human history and is a unique blend of not only human development. It also reflects, on the one hand, national culture and mentality, and on the other, shows the influence of natural factors on their development. It also helps to understand the mentality of various ethnic groups, similarities and differences in their perception of the world and attitude. The development of the cultural landscape concept has become an integral part of the Anthropocene theory, based on the teachings of V.I. Vernadsky, about the impact and intersection of the geo-, bio- and noosphere in the fate of humankind. Results. The article considers the development of the “cultural landscape” theory mainly in English and American historiography which conclusively demonstrates how natural factors impact on changes in culture of the same ethnos. Through historiographic studies and comparisons, it becomes possible to trace the importance of preserving and studying the cultural landscapes of the past and present, in order to understand ourselves and be responsible to the world around us

The universal algorithm for solving the gas dynamics equations on the mesh with arbitrary number of cell faces

The paper presents methodology and algorithm for calculating the equations of gas dynamics on arbitrary computational meshes with a mixed type of cells. The calculation method is based on the method of linear reconstruction proposed by Barth and Jesperson. The algorithm for determining the geometric parameters of arbitrary computational cell is presented. To implement the calculation algorithm, a data storage system has been proposed and tested. The algorithm of the solver and the algorithm of docking the computational meshes in the case of using block-structured meshes are proposed. The efficiency of methodology and developed program of calculation are demonstrated by the calculation example of the air flow in flat air intakes. The structure of flow and position of the bow shock wave are determined. These results with the theoretical values were compared. The application of the proposed methodology and calculation algorithm to arbitrary computational meshes with a mixed cell type makes it possible to optimize the process of constructing computational mesh and conduct numerical studies of gas dynamics in regions of complex geometry

Results of Comprehensive Geophysical Studies on the Search for Crypts on the Territory of Suburban Necropolis of Tauric Chersonese in the Karantinnaya Balka

The article presents the results of comprehensive studies carried out by the research team of Saint Petersburg Mining University in cooperation with the specialists from the State Museum-Preserve "Tauric Chersonese" in 2019. The purpose of the work was to discover and map antique and medieval crypts (ancient burial structures) on the territory of suburban necropolis of Tauric Chersonese in the Karantinnaya balka. The complex of geophysical methods included continuous ground penetrating radar sounding at two center frequencies of 350 and 500 MHz and contactless electrical tomography. To minimize spatial errors in the process of studies, topographic and geodetic works were carried out. For the first time wave electromagnetic effects were identified, which indicated the positions of hidden underground crypts. Geological factors were established that are favorable for cutting crypts in the layered thickness of Sarmatian limestones. The obtained results allowed to justify the feasibility of continuing geophysical works at the necropolis in order to study interior space of the discovered crypts and to determine the boundaries of archaeological heritage