Mathematical modeling of turbulent jets of deep-water sewage discharge into coastal basins

The basic properties of the dynamic model of a turbulent jet formed by a deep-water sewage discharge into the stratified environment of coastal regions are considered. The model developed was used to estimate the parameters of a floating-up jet of deep wastewater discharge from Sand Island into the basin of Mamala Bay (Hawaii) depending on the season and discharge operation mode. The estimates of the float-up depths of the jet and the initial dilution of the jet were estimated on the basis of model calculations using experimental data on the vertical profiles of the water temperature and salinity under the actual conditions of stratification in the study region. It is shown that the further propagation of the wastewater jet depends on tidal events and internal waves generated by tides. The appearance of turbulent jets at the sea surface was recorded. The model estimates of the parameters of the wastewater discharge were compared with the results of experimental measurements. Good agreement was found, which indicates that the physical mechanisms of the propagation of turbulent jets in a stratified medium are adequately described by the model.     

The spectral characteristics and kinematics of short-period internal waves on the Hawaiian shelf

Based on the results of analyzing the characteristics of currents and temperature measured in the water space of the Mamala Bay (the Island of Oahu, Hawaii), we investigate the main properties of the field of short-period internal waves, which is very complex. We focus on analyzing the spectral characteristics and orbit parameters for waves with a period of 20 minutes. The results of investigations reveal two types of short-period internal waves for this area: intense and fast waves propagating predominantly toward the ocean and weaker and slower waves propagating mainly toward the coast. Suppositions are made on how these waves form: the strong and fast waves are likely to be caused by the decay of locally generated internal tides near the shelf edge, while the weak and slow and very short waves seem to result from the specific interaction between the pycnocline and strong tidal currents over a steep slope.     

Energy Spectra of Cosmic-Ray Protons and Nuclei Measured in the NUCLEON Experiment Using a New Method

Astronomy Reports - Some results of studies of cosmic rays obtained during the NUCLEON space experiment in 2015–2017 are presented. This experiment was intended for direct measurements of the...     

Ecotoxicological monitoring in lakes of Northwestern and Central European Russia situated in specially protected natural areas

An ecotoxicological assessment is given to the state of small lakes in specially protected natural areas in Northwestern and Central European Russia, which suffer from aerotechnogenic acidification. The toxicity of water and bottom sediments is shown to increase with decreasing water pH. The most sensitive characteristics of aquatic organisms in different trophic groups are chosen, allowing the state of lakes to be monitored.     

Fine vortex columns on the shelf in the area of bottom convection influence

This paper analyzes the results of investigations into extremely large releases of current velocities registered by an acoustic Doppler profiler during experiments performed on the Hawaii shelf. An integral analysis of the variability of current fields relies on the profile data of current velocities, temperature, and acoustic-scattering layers. Based on these investigations, we proposed a hypothesis stating that the small-scale variability of currents in profiler data is conditioned by the passage of fine vortices emerging in the outflow and rise of freshened waters from a subsurface sink near the shelf edge. To confirm this hypothesis on the emergence mechanism of the observed releases of current velocities, we conducted a mathematical simulation of the response that the Doppler meter has to the passage of fine vortex, which revealed a good agreement between model calculations and experimental data. Similar phenomena were also found in the Gelendzhik Bay of the Black Sea.     

Assessment of bottom sediment contamination in acidified Karelian lakes

The physicochemical, toxicological, and teratological properties of bottom sediments in Karelian lakes (Vuontelenjarvi, Suojarvi, Venderskoe, and Chuchjarvi) and Kondopoga Bay of Lake Onega are studied. Bioassay results testify to a high toxicity of bottom sediments in heavily acidified lakes (with the water pH of 5.5 and lower).     

Surface manifestations of internal waves investigated by a subsurface buoyant jet: 3. Surface manifestations of internal waves

In a large test reservoir at the Institute of Applied Physics, Russian Academy of Sciences, a series of experiments were performed to investigate the surface manifestations of internal waves radiated by a subsurface buoyant jet. The field of currents on the water surface of the reservoir was studied through the distribution of temperature with shallow thermocline. Using Particle Tracking Velocimetry (PTV), the velocity field of surface currents was measured. A theoretical model was developed to calculate the rates of disturbances on the surface. A comparison with experimental data indicated that the calculated data of the surface rate value are overestimated. This discrepancy was explained by the presence of a film of surface-active substances (SASs) with experimentally obtained parameters. Using scale modeling coefficients, we estimated the parameters of internal waves radiated by the subsurface wastewater system and the values of their surface manifestations in field conditions. We estimated the hydrodynamic contrasts in the field of surface waves, which can be caused by these inhomogeneous currents on the surface. For a wind velocity of 5 m/s, the magnitude of the contrast in the field of short waves can reach up to 10–25%, which is detected with confidence by remote-sensing methods.     

Surface manifestations of internal waves investigated by a subsurface buoyant Jet: 1. The mechanism of internal-wave generation

In a large test reservoir with artificial temperature stratification at the Institute of Applied Physics, Russian Academy of Sciences, we have performed a major laboratory simulation of the nonstationary dynamics of buoyant turbulent jets generated by wastewater flows from underwater collector diffusers. The interaction of buoyant jets with the pycnocline leads to an active generation of internal waves. An analysis of the dependence of wave amplitude on the control parameter proportional to the rate of liquid flow from the collector diffuser has indicated that this dependence is adequately described by a function that is characteristic for the presence in the Hopf bifurcation system, which occurs for a soft actuation mode of self-oscillations of the globally instable mode. To check the conditions for the actuation of the globally instable mode, we have performed an auxiliary experiment in a small reservoir with a salt stratification formulated similar to the experiment in the big reservoir. Using the particle image velocimetry (PIV) method, we have measured the velocity field in the buoyant jet and constructed the profiles of transverse velocity in several sections. When the jet approaches the pycnocline, a counterflow is generated at the edges. A stability analysis for the resulting profiles of flow velocities performed by the method of normal modes has revealed that, for the jet portions with counterflow, the condition of absolute instability by the Briggs criterion for axisymmetric jet oscillations is satisfied, which testifies to the fact that the globally instable mode is actuated. The estimates for oscillation frequencies of the globally instable mode are well consistent quantitatively with the measured spectrum of jet oscillations.     

Modeling the sea currents in open basins: The case study for the Hawaiian Island region

The fields of currents in open basins are studied with the use of a mathematical model of ocean hydrodynamics. The area of the Hawaiian Islands is taken as an example. The model, based on three-dimensional equations of thermohydrodynamics, is solved for a domain with open boundaries, at which adaptive boundary conditions are set. We analyze the results of numerical experiments with given monthly mean climatic conditions at the ocean surface and open lateral boundaries with consideration for tides M ₂ and K ₁. A comparison of the model solutions and observational data shows that the model can realistically reproduce the mean parameters of the ocean state and their variability. The model solutions for the given area were found to have a northward current in the upper oceanic layer. This current clearly manifests itself in averaged fields. The characteristics of averaged currents indicate that the upper 100–150-m layer between the islands of Hawaii and Maui as well as between the islands of Molokai and Oahu is characterized by water transport from the west to the east side of the ridge of islands. The results obtained and the model proposed can be used to monitor physical fields of the ocean.     

Anomalous variation of the ocean’s inertial oscillations at the Hawaii shelf

The data of acoustic Doppler profilometers placed at the edge of the steep shelf of Oahu Island, Hawaii, are analyzed for the currents. The specific character of inertial oscillations is revealed in the region: strong elongation of inertial orbits, a large amount of anomalous (cyclonic) current rotation, and sharp weakening in the divergence layer of the background (low-frequency) oscillations, the strong variation of which results in significant deviations of the effective inertial frequency from its local geographical value. It is suggested that cyclonic rotation of the inertial currents is related to a strong decrease in the effective oscillation frequency of the oceanic waves on the shelf.