The study is based on data from four moorings stretched out in the north-northwest – south-southeast direction across the isobaths in the southwestern Peter the Great Bay, the Sea of Japan, on 3–14 October, 2022. For this purpose, timeseries of vertical profiles of temperature and its gradient were expanded into empirical orthogonal functions; timescales were estimated using wavelet transform. In all cases, the leading mode captures vertical stratification variability related to the thermocline shoaling or deepening, manifesting itself by concerted oscillations of temperature and its vertical gradient, which occurred on the near-inertial, semi-diurnal and two-diurnal timescales. The near-inertial oscillations were the most intense during most of the time, while the semi-diurnal ones were the most intense on the fourth and fifth days. From the joint wavelet spectra it was found that temperature anomalies moved towards the shallower area and the speed was estimated as equal to 0.44–0.55 and 0.95–1.11 m/s for the near-inertial and semi-diurnal timescales, respectively. The speed on the two-diurnal timescale differs by an order of magnitude between the pairs of two deeper and two shallower moorings, equaling to 1.17 and 0.15 m/s, respectively. The results were interpreted as related to the near-inertial and semi-diurnal internal wave propagation from the continental slope towards the inner shelf and two-diurnal timescale was speculated to be a difference between them caused by non-linearity.

The instantaneous and average structure of a supersonic underexpanded jet is studied numerically and experimentally. The photos obtained in experiments with different exposure times and the Pitot pressure measurements are compared with the results of the numerical simulation performed using an implicit large-eddy method. We note that the jet flow instability, disturbance growth, and transition to turbulence lead to the situation, in which the instantaneous flow structure can be considerably different from the average structure. The flow pattern observable in the calculations is in good agreement with that presented in the experimental photos obtained with short exposure times. Both calculated and experimental data indicate that an important role in the jet flow dynamics is played by large-scale vortex structures that exist against the background of small-scale turbulence. The calculated and experimental Pitot pressure distributions are similar with each other, up to a certain distance from the nozzle exit section. Further downstream, the experimental and calculated Pitot pressures start to increase rapidly but the calculations predict the onset of this growth at a greater distance from the nozzle than it is observable in the experiments.

The actual problem of the presented research is to study the peculiarities of acoustic signal transformation at the geosphere boundary in the “water-land” transition zone. The signal energy of a moving hydroacoustic radiation source is transformed in the coastal zone into seismoacoustic oscillations recorded by a coastal two-coordinate laser deformograph. The spatial position of the measuring components of the laser deformograph makes it possible to localize the displacement of an object in the nearby water area based on the study of variations in the amplitude of the recorded signal. The methodology of the experiment based on the movement of the transmitter with constant speed and distance from the shore measurement system is described. As a result of the experiment, a stable registration of the seismoacoustic signal was obtained along the entire trajectory of the transmitter with a decrease in the amplitude of the received signal when it is at an angle close to 45 degrees. According to the results of the analysis of variations in the amplitude of the registered signal on differently directed components of the laser deformograph, the results of direction finding of the source of low-frequency hydroacoustic radiation were obtained, with the error in determining the direction to the hydroacoustic source ranging from 0.2 % to 10.5 %.

The results of visualization of a near-wall turbulent flow with air blowing of various intensity through a perforated surface area on an axisymmetric body with an aspect ratio of 25.3 under conditions of an incompressible flow around are presented. It is shown that the use of the laser knife method with seeding the flow with light-scattering particles 1–2 μm in size, formed from a water-based mixture that includes polyglycol, makes it possible to visualize the structural elements of the near-wall flow region, which are technically difficult to detect by traditional measurement methods.

The shelf area off Vladivostok in the Sea of Japan is known by the intense internal wave activity investigated for many years. The present contribution to these studies is based on data collected on 3–14 October 2022, from four moorings aligned across isobaths and equipped with thermostrings. Multivariate analysis is performed in the depth–time domain, while timescales and directions and speeds of temperature anomaly movement are estimated from wavelet transform. Approximately 50% of the variance results from vertical stratification changes, i.e., thermocline deepening or shoaling, and temperature anomalies on different timescales moved towards the shoaling seafloor. For the first time, near-inertial (NI) oscillations are detected throughout the record and turn out to be the most intense among the 6 to 70 h timescales, moving with the speeds of 0.41–0.55 m/s, although previous attention was paid to the semidiurnal internal tide. A frequency decrease, i.e., red shift, of the NI oscillations is detected towards shallower water, with the frequency eventually becoming subinertial, and is explained by anticyclonic relative vorticity at the eastern side of the mushroom-like structure detected from thermal satellite imagery. The semidiurnal and two-day oscillations were detected, moving with the speeds of 0.95–1.11 and 0.15–1.17 m/s, respectively. The two-day timescale, never reported before, is considered as a difference one caused by nonlinearity. These results are interpreted as the propagation of an internal wave generated at the steep slope offshore to the inner shelf.

This paper presents a discussion on observations of nonlinear internal waves (NLIWs) in the coastal zone of the Sea of Japan, based on the mooring of thermostring clusters in different seasons of 2022. For statistical evaluation of the frequency of event occurrence and determination of NLIW movement direction, we use our observations of the past 12 years. We present the NLIW structures, observed in spring, summer, and autumn of 2022, which are typical for this shelf area. Two types of nonlinear waves are described—solitary and undular bores, with or without strong vertical mixing behind the front. We demonstrate spatial transformation of an undular bore as it moves over the shelf. A mathematical model based on the second-order shallow water approximation is proposed for numerical simulation. To simplify calculations, the authors limit themselves to two- and three-layer shallow water models. We investigate the possibility of spatiotemporal reconstruction of internal nonlinear structures between thermostrings using experimental data and proposed models. The authors show that at distances of up to several kilometers between thermostrings, the wave fields of strongly nonlinear and nonstationary structures can be successfully reconstructed. Water flow induced by NLIWs can be reconstructed from the data of even one thermostring.

This paper presents a method for reconstructing the gas-dynamic parameters of gas flow based on non-contact PIV measurements of the velocity field. The wake flow past a model single rocket nozzle of an emergency escape system in the normal transonic (Mach number is 0.85) flight regime of the manned spacecraft rocket is considered. The flow around the nozzle is numerically simulated using the RANS and LES methods. The results obtained by the proposed reconstruction method are compared with numerical and experimental data.

The knowledge of salinity in a specific sea area with high accuracy is required to solve several acoustic and hydrophysical problems on the ocean shelf. Unlike temperature, which can be measured continuously for a long time, with, for example, thermistor strings (thermostrings), salinity values of required accuracy can be obtained only using CTD profiling. This is why methods of estimating salinity from temperature could be helpful. In this paper, the authors propose using the regression method for solving this type of problem and demonstrate the efficiency of this method using examples of temperature measurements from anchored thermostrings. For the correct construction of regressions, the authors analyzed the errors of CTD measurements and suggested a method for the dynamic correction of raw CTD data. From CTD profiling datasets of 12 years (2011–2022), after their dynamic correction, the authors obtained regression polynomial formulas for calculating salinity from temperature and studied data stability in space and time at the hydrophysical test site, located in the shelf zone of the Sea of Japan. The authors consider this method efficient and applicable in solving a variety of acoustic and hydrophysical problems.

Results of numerical investigations of the characteristics of a turbulent boundary layer in the case of air blowing through a smooth flat perforated surface with a single hole and also through a similar surface with a group of staggered holes 0.18 mm in diameter ( d/δ =0.0072) in a low-velocity flow are reported. The Reynolds number Re** based on the momentum thickness δ ** ahead of the perforated region is 2600. The blowing coefficient C b is varied in the interval from zero to 0.0438. The influence of some geometric parameters, in particular, the distance between the hole centers, on the properties of the transverse shear flow for identical intensities of blowing in situations with one hole and with a group of holes is analyzed. All observations reveal stable reduction of local friction whose value varies depending on the number of holes and their arrangement on the surface.

To study the features of resonant oscillations in the water column of the Peter the Great Gulf of the Sea of Japan, in situ measurements were carried out on its shelf, combined with numerical simulation of these processes. The observational data were obtained from autonomous bottom pressure gauges in Novik Bay in the winter of 2016. In the calculations, a spectral-difference model was used, modified to account for the ice cover, and implemented on an irregular triangular grid. The atmospheric forcing used in the model had periods from 15 to 55 min. As a result, characteristic series of spatio-temporal parameters for resonant oscillations of the studied water area were determined. The locations of the peaks on the simulated resonance curves correspond to the locations of well-defined maxima of the energy spectrum according to in situ measurements, hence indicating the possibility of a significant resonant amplification of level fluctuations by wave and periodic wind effects. The novelty of this study is inclusion of the winter period, when the surface of the bay is partially covered with ice.

В статье представлены результаты гидрологических исследований на шельфе залива Петра Великого Японского моря в июле – августе 2012, июле – августе 2017, августе 2019 и августе 2021 годов. Пространственная изменчивость полей температуры и скорости звука, характерная для региона, проанализирована по результатам гидрологических CTD-зондирований и долговременных измерений заякоренными вертикальными термогирляндами. В ходе измерений было зарегистрировано прохождение тайфунов Болавен (28–29 августа 2012 года), Нору (7–8 августа 2017 года), Кроса (16 августа 2019 года), Мирина (7–9 августа 2021 года), Лупит (8–9 августа 2021 года), Омаис (10–11 августа 2021 года) у побережья Приморья Российской Федерации. Показано значительное изменение гидрологической ситуации в заливе под воздействием экстремальных внешних факторов. В спокойных метеорологических условиях в заливе наблюдается до трех слабовыраженных термоклина, расположенных на глубинах 8–15 м, 30–35 м и 45–60 м. Во время прохождения тайфунов три термоклина объединяются в один мощный на глубине примерно 50–60 м, а в некоторых случаях термоклин с большим градиентом находился на глубинах 30–40 м. Перепад температуры в термоклине, сформированным под действием тайфунов, составил примерно 12–15°C на 10 м глубины. По-видимому, усиления волнения и нагон прогретой поверхностной воды в заливе Петра Великого, вызванные сильными южными и юго-западными ветрами, приводят к появлению ярко выраженного придонного подводного звукового канала. Поскольку такие изменения влияют на распространение акустических сигналов, их особенно важно исследовать при работе с автономными подводными объектами, осуществлении их позиционирования и связи с ними.

В статье представлены результаты гидрологических исследований на шельфе залива Петра Великого Японского моря в июле – августе 2012, июле – августе 2017, августе 2019 и августе 2021 годов. Пространственная изменчивость полей температуры и скорости звука, характерная для региона, проанализирована по результатам гидрологических CTD-зондирований и долговременных измерений заякоренными вертикальными термогирляндами. В ходе измерений было зарегистрировано прохождение тайфунов Болавен (28–29 августа 2012 года), Нору (7–8 августа 2017 года), Кроса (16 августа 2019 года), Мирина (7–9 августа 2021 года), Лупит (8–9 августа 2021 года), Омаис (10–11 августа 2021 года) у побережья Приморья Российской Федерации. Показано значительное изменение гидрологической ситуации в заливе под воздействием экстремальных внешних факторов. В спокойных метеорологических условиях в заливе наблюдается до трех слабовыраженных термоклина, расположенных на глубинах 8–15 м, 30–35 м и 45–60 м. Во время прохождения тайфунов три термоклина объединяются в один мощный на глубине примерно 50–60 м, а в некоторых случаях термоклин с большим градиентом находился на глубинах 30–40 м. Перепад температуры в термоклине, сформированным под действием тайфунов, составил примерно 12–15°C на 10 м глубины. По-видимому, усиления волнения и нагон прогретой поверхностной воды в заливе Петра Великого, вызванные сильными южными и юго-западными ветрами, приводят к появлению ярко выраженного придонного подводного звукового канала. Поскольку такие изменения влияют на распространение акустических сигналов, их особенно важно исследовать при работе с автономными подводными объектами, осуществлении их позиционирования и связи с ними. The paper presents the results of hydrological studies which we carried out on the shelf of the Peter the Great Bay of the Sea of Japan in July – August 2012, July – August 2017, August 2019 and August 2021. We have analyzed spatial variability of temperature and sound velocity fields, peculiar to the region, on the basis of hydrological CTD-data and the results of long-term measurements with anchored vertical thermostrings. In the course of measurements, we registered the following typhoons during theirpassageoff the coast of the Primorsky Territory of Russia: Bolaven (August 28–29, 2012), Noru (August 7–8, 2017), Krosa (August 16, 2019), Mirinae (August 7–9, 2021), Lupit (August 8–9, 2021), Omais (August 10–11, 2021). A significant change in the hydrological situation in the bay under the influence of extreme external factors is shown. Up to three mild thermoclines are observed in the bay in calm meteorological conditions. Its are located at depths of 8–15 m, 30–35 m, and 45–60 m in some cases, a thermocline with a large gradient was located at depths of 30–40 m. The temperature difference in the thermocline formed under the influence of typhoons was approximately 12–15°C per 10 m of depth. Apparently, the intensification of waves and surge of heated surface water in the Peter the Great Bay, caused by strong southerly and southwesterly winds, lead to the appearance of a pronounced near-bottom underwater sound channel. Since such changes affect the propagation of acoustic signals, they are especially important to study when working with autonomous underwater objects, their positioning and communicating with them.

The research aims to study the resonant properties of the water area of the Peter the Great Gulf, in the Sea of Japan. The coast of the gulf is exposed to the threat of tsunamis due to relatively high seismic activity in the Sea of Japan. On May 26, 1983, a tsunami hit several bays of the gulf with wave heights reaching 5 m. As a response, the coasts were equipped with three sophisticated sea level measuring stations. Field measurements with installation of autonomous pressure gauges were carried out August 18–26, 2016, to study the peculiarities of free surface oscillations in the western part of the Peter the Great Gulf. Spectral analysis of the recorded data and the data obtained from the Posyet automated post of the Russian Tsunami Warning Service showed, in particular, that there were several clearly pronounced peaks at periods of 40, 48, 79 and 89 min. These oscillations are coincident for the Sea of Japan and the studied water area with a wide entrance. A finite-volume numerical model was used to calculate free oscillations in the computational domain covering the Sea of Japan region. We performed model calculations with an irregular triangular grid. This allowed us to describe both the outer water area of the Sea of Japan and separate small-scale relief elements in the water area under study, which are important for the formation of local seiches. Isophases and spatial patterns of several resonant oscillations spectra at 15–105 min periods were obtained for the Peter the Great Gulf area. Model calculations carried out in this work showed an evident spatial structure of resonant oscillations. Such research, including field measurements in adjacent coastal waters, is required to identify and monitor potentially hazardous coastal areas. The amplification of resonant oscillations depends on how effectively the specific atmospheric disturbance generates corresponding eigenmodes of the Sea of Japan. In some bays, the amplitudes of the Sea of Japan eigen oscillations can increase due to resonant properties of coastal water areas, even with a low quality factor. If the amplitudes are large, such a double resonance can lead to a meteorological tsunami.

The experimental study results of the mixing layer of subsonic jet exhausting from a convergent axisymmetric nozzle at a Mach number Ma = 0.85 are presented. The mixing layer thickness at the high-speed subsonic jet initial section is determined. The values and histograms of the flow velocity root-mean-square deviations at mixing layer different points are given. The applicability analysis of the panoramic laser PIV method to the structure study, average values and velocity pulsations characteristics in the mixing layer is carried out on the literature data basis on the level of pulsations in subsonic jet flows.

The temporal characteristics of the processes of deformation and disintegration of a freely falling drop of a low-viscosity liquid in an air accelerating flow are studied. The experiments were carried out under fast loading and in the regime of impulse-quasi-static loading of drops at moderate gradients of flow velocity. Experimental values of the interaction time and the induction time of the drop breakup are obtained.