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The paper reviews the results of comprehensive studies and dating of contourite deposits from the Southwest Atlantic. It focuses on sediment transport and depositional processes as well as sediment sources in the context of Pliocene-Quaternary environmental and climatic changes. The work primarily highlights investigations conducted over the past decade by the Laboratory of Paleoceanology of the Shirshov Institute of Oceanology RAS in collaboration with other research groups over the last decade. The study examines contourite systems along the Argentine Patagonian continental slope, on the Santa Catarina and São Paulo plateaus, the Ioffe contourite Drift and the gravitite-contourite system, at the foot of the São Tomé Seamount . These systems were identified using a comprehensive approach combining seismo-acoustic, lithological, geochemical, and magnetic susceptibility data. Specific features of contourites that distinguish them from other types of deep-sea sediments are considered. The sediment age was defined by biostratigraphy and/or oxygen isotope stratigraphy and confirmed by AMS-14C dates (within the last 50 ka). The depositional system formation was predominantly controlled by erosion-depositional activity of bottom along-slope currents of the Antarctic origin. These Antarctic waters are a key component of Atlantic meridional circulation and the global conveyor system. Consequently, the contourite systems formed under the influence of these waters preserve a geological archive of the region's climatic and oceanographic history. The Ioffe Drift contains the longest sedimentary record in the study area, spanning the last 3.2 Ma. This time interval captures the development of modern-type paleoceanographic variability following the closure of the Panama Gateway. Other studied systems preserve sedimentary sequences documenting glacial-interglacial stages and associated changes in sea level, climate, and bottom current circulation during the Late Quaternary.

A study of the complex spatial flow of a freon jet flowing out of a long triangular cross-section channel in the laminar-turbulent transition mode was conducted. In order to obtain a detailed picture of the flow, a multi-angle measuring complex of Gilbert diagnostics was implemented based on the IAB-463M device. It was shown that the channel geometry has a weak effect on the laminar-turbulent transition scenario in the channel, with the formation of turbulent spots. It was found that when a turbulent spot hits a jet flowing out of a triangular cross-section channel, it causes turbulization and generates secondary disturbances in the mixing layer. The results may be of practical importance in CVD combustion and deposition processes.

A new method for improving the quality of images reconstructed from digital holograms is considered. It utilizes spatial subpixel shifts, i.e., shifts by a certain value smaller than the resolution provided by the recording devices. In digital holography, photodetector matrices are used as a recording medium for holograms. The resolution is determined by the type of matrices used. To obtain holograms, a camera with a photodetector matrix with a resolution of 9000 × 6752 and a single element size of 0.86 × 0.86 μm was used. The size of the matrix used was 7.7 × 5.8 mm, the spatial resolution of such devices is approximately 500-1000 lines/mm. This already makes it possible to obtain digital holograms. However, to improve the quality of reconstructed images, it is necessary to increase the hologram resolution during registration. To increase the resolution, a device for introducing a spatial subpixel shift of the photodetector matrix was used in this study. Insufficient matrix resolution was compensated for using subpixel spatial shifts. The shift was performed along the X and Y coordinates by 430 nm, which was half the size of one matrix element. The digital hologram size increased fourfold (18,000 x 13,504 pixels). Image reconstruction was performed using a fast Fourier transform. To speed up the process, a graphics accelerator was used to reconstruct images from holograms.

An experimental study of the primary and secondary unsteady instabilities of the boundary layer of a swept wing was conducted under conditions of dominant primary crossflow instability in the presence of a localized three-dimensional roughness element on the streamlined surface. Measurements were performed using a hot-wire anemometer in a low-turbulence wind tunnel at low subsonic free-stream velocity under conditions of uncontrolled ("natural") unsteady disturbances. Four types of amplified unsteady boundary layer disturbances were detected and studied in detail: low-frequency disturbances associated with primary flow instability, mid-frequency disturbances (type III secondary instability), and high-frequency disturbances (types I and II secondary instability). The properties of these disturbances were studied in detail, and an analysis of the position and shape of their localization regions in the plane normal to the wall and flow was performed relative to the layers of strong shear of the longitudinal component of the mean flow velocity along the spanwise and normal to the wall. The complex nature of the secondary disturbances is demonstrated, which is difficult to explain by the simplified concepts of the existence of z- and y-modes of secondary instability considered in previous studies.

The article presents the results of hot-wire measurements of the free-flow and boundary layer of a flat plate with a blunt leading edge, in the presence of an N-wave disturbance source. Based on the measurements, estimates of the cross-correlation characteristics were obtained. Based on the distribution of the mutual phases, conclusions were drawn regarding the presence of diffraction phenomena of free-flow pulsations. It is shown that, in contrast to the case with a sharp leading edge, in the case of a blunt leading edge it is not possible to reliably determine the presence of diffraction phenomena.

The flow pattern in the planar turbulent far wake past a body in a passively stratified medium is investigated by applying a mathematical model including the following features: Rodi’s algebraic approximations for Reynolds stress, the differential equation for transfer of a deficit in the mean velocity longitudinal component, the balance of the turbulence energy and its dissipation rate, fluid density deficit, vertical component of the mass flux vector, and the equation for dispersion in the turbulent fluctuations of density. The far-wake approximation is used in this problem. The paper discusses an issue of the local-equilibrium truncation taken for the two last equations. We compare the solutions of self-similar degeneration of the density field characteristics for a case of a classical turbulent wake behind a towed cylinder and for a case of momentumless turbulent wake. The results of numerical experiments were a foundation for interpreting the observed high error while using the locally-equilibrium truncation equation for transfer of the density fluctuations dispersion.

An experimental study was performed for a flow in a channel with an intermittent pattern of roughness. The influence of the relative obstacle height (ranging from 2 to 10 % of the channel height) on the turbulence characteristics and flow structuring in the channel nearwall zone was studied. The research was focused on the case of obstacles with a low height. We found that the obstacle height below 5.5 % induces a drastic change in pulsation and spatial flow characteristics; this alters the flow pattern in the separation zone and the vortex generation mechanisms. The across size of vortex behind the obstacle with a relative height of 2 % is twice as big as the obstacle height. The characteristic peak in spectra that corresponds to the vortex shedding frequency with fully developed roughness tends to degenerate with a decrease in the obstacle height. Here the key factor for vortex generation is due to vertical swing motion of the boundary for separation zone.

Methods of 3D numerical simulation were applied for evaluating the flow dynamics in the internal electrode of a plasmatron with a two-chamber design while a “cold” blowout through the electrode. This study presents spatial distributions for the gas flow velocity, turbulence kinetic energy and the pressure inside the two-chamber electrode equipped with two swirlers (they provide tangential input for plasma-forming air flow). Variations in the gas velocity for transversal cross-sections of the arc chamber are in agreement with previously published data for the case of “cold” smoke-based blowout of the two-chamber plasmatron equipped with a cylindrical electrode. It was established that the cylinder-conical shape of the internal electrode might result in a shorter initial laminar column in the electric arc; this happens due to expansion of the turbulent interval at a fixed length of the arc. Experiments in a plasmatron with an inter-electrode insert demonstrated that the cylinder-and-cone shape of the electrode causes a higher (by 30-35 %) voltage on the plasmatron as compared with the cylinder-only shape of the electrode. This is a qualitative confirmation for calculated results about a higher kinetic turbulence energy and a wider turbulent zone of the electric arc occurring in a two-chamber design plasmatron.

An experimental study of polydisperse pulp hydrodynamics is relevant for the tasks of aluminum production. The diagnostics method of matrix electrical impedance has been developed based on the synchronous recording of the spatial distribution of parameters of the complex conductivity and dielectric permittivity of the medium at the nodes of a wire mesh. This method allows for the study of three-dimensional flows of a multiphase model. The core of the measuring system is a matrix mesh electrical impedance sensor consisting of coordinate-linked sets of conductors whose spatial intersections form the measuring nodes of the system. The tracer is a liquid with a complex electrical conductivity different from that of the main flow. During the measurements, impedances are dynamically recorded at each three-dimensional spatial node of the mesh, determining the parameters of multiphase flows. The study experimentally demonstrated the feasibility of measuring impurity propagation during mixing in liquids with a dynamic range extended to 90 dB.

Experimental results on the diffusion combustion of a hydrogen microjet escaping from a sphere enveloped in an air flow are presented. Two limiting cases of the outflow of a burning hydrogen microjet are considered: when the jet is located at the flow divergence point on the sphere and at the opposite point, at the aft end of the sphere, where different separated flow structures are realized. Three characteristic hydrogen microjet flow velocity regimes were studied, allowing for the creation of various burning jet structures at zero incident flow velocity. The changes in the jet topology and structure were demonstrated. Flow visualization was performed using a thermal imager. A comparison was made with results obtained using a shadowgraph.