Water Wedge Research Articles

Numerical investigation of free surface flow impact using an accelerated three-dimensional smoothed particle hydrodynamics

Water impact problems are inevitable in the realm of ocean engineering. The smoothed particle hydrodynamics method (SPH), as a meshless particle approach, can effectively reproduce the slamming process which involves large deformation of the free surface. In this study, an accelerated three-dimensional SPH model is constructed based on the graphic processing unit (GPU) with the speedup of up to 40. The six-degree-of-freedom motion equation is introduced to realize the responses of the solid. The fluid-solid interaction system is achieved by regarding the rigid body as the moving boundary of the fluid. The computational accuracy and efficiency of the developed model are respectively verified by the wedge water entry, dam breaking and inclined cylinder water entry. Finally, the developed model is applied to a complex flight vehicle landing problem, and the effect of the initial horizontal velocity, vertical velocity and pitch angle on the impact process are qualitatively and quantitively studied.

Integral Representations of Solution in the Problem on Skew Incidence of a Surface Wave on the Straight Shoreline Water Wedge

In the linear approximation of the surface gravitational waves of small amplitude a classical model problem about the incursion of a surface wave under some angle on the shoreline is solved. The problem is formulated for the harmonic potential of velocity of the fluid in the 3D water wedge with the Robin-Steklov boundary condition on the free surface and with the no-flow condition along the normal on the bed of the water domain. Some critical comments about a known in the literature solution having a “non-physical” singularity of the logarithmic type on the coastal line are given. The asymptotics with respect to distance from the shoreline of the obtained solution, bounded on the edge, is constructed. The reflection coefficient of the wave reflected from the shoreline is calculated.

Experimental and simulation studies on the waterproofing performance of anchored sealing gasket for shield tunnel lining

Anchored sealing gasket can be prefabricated together with prefabricated segment in the prefabrication factory, which can significantly improve the on-site construction convenience and waterproofing performance of shield tunnel segments. This paper proposed a novel anchored sealing gasket with a closed bottom and a symmetric pair of anchored feet on both sides, and the mechanical properties, waterproofing performance, and leakage mechanism of the gasket was investigated by experimental and numerical simulation methods. Test results show that for traditional sealing gasket, leakage occurs at the contact surface between the sealing gasket and the segment, while for anchored sealing gasket, leakage occurs only at the contact surface between the sealing gaskets, which indicates that the anchored sealing gasket feet can effectively prevent leakage between the sealing gasket and the shield segment. Compared with the traditional sealing gasket, the waterproofing ability of the anchored sealing gasket under the same working conditions is increased by 114%. The dynamic simulation of the waterproofing behavior of the anchored sealing gasket, considering the effect of water pressure, was carried out based on the flow-solid coupling model established by the Coupled Euler-Lagrangian (CEL) method. It was found that the waterproofing behavior of the anchored sealing gasket can be divided into four stages: the segment compression stage, the water compression stage, the water wedge stage, and the water breakthrough stage. The water resistance ability between the anchored sealing gasket and the segment is much higher than between the sealing gaskets. The anchor feet can prevent leakage at the interface between the gasket and the segment effectively. In addition, it was found that the test value of the waterproofing capacity of the anchored sealing gasket was close to the peak value of the maximum contact stress between the sealing gaskets during the water wedging stage, and this peak value can be used as a prediction method for the waterproofing capacity of the anchored sealing gasket to investigate the effect of joint deformation on waterproofing capacity. Finally, based on the experimental and simulation results, the waterproofing mechanism of the anchored sealing gasket was revealed, providing a reference for the waterproofing design of anchored sealing gaskets for prefabricated underground structures joints in the future.

Study on the Seepage Mechanism of Gaskets at the Joints of Shield Segments Based on Coupled Euler-Lagrangian Method

In the construction and operation stage of urban shield tunnels, joint leakage of shield is always an urgent problem to be solved. In order to further explore the waterproof performance of elastic rubber gaskets at segment joints, the finite element software ABAQUS (2022) was used to establish a fluid-solid coupling calculation model. The dynamic simulation of the leakage process at the segment joints under water pressure revealed the whole process of leakage at the segment joints and the instant water pressure value when the waterproof system failed. The results show that during the whole process from segment assembly to joint leakage, the elastic rubber gasket has experienced four key stages: gasket compression, confined water pushing, water wedge and final leakage. When the opening amount of the gasket is 6 mm and 10 mm, the contact stress between the gasket shows a “W” symmetrical distribution of high at both ends and low in the middle, and the peak of the contact stress at both ends of the interface is about twice as much as that in the middle. The waterproof threshold of the gasket is closely related to the opening amount of the gasket, and the waterproof threshold has the same trend with the initial contact stress between the gaskets.

Experimental study on the damage and fracture mechanism of deep coal beds impacted by water jets at different temperatures

The development of abundant deep coalbed methane (CBM) resources has attracted significant attention due to their commercial development potential. However, developing such resources presents many challenges due to their generation in complex geological environments governed by high temperatures and stresses. Thus, this work investigated coal fragmentation using water jets at different reservoir temperatures. The results show that compared with room temperature conditions, under water jet impact, the threshold fracturing pressure of high-temperature coal is lower, the rock-breaking volume is larger, and thermal stress leads to intensified dynamic damage. Indeed, when the temperature exceeds 75.0 °C, the coal undergoes volume fragmentation, and the depth of water jet-breaking coal increases by 81.0 %, while the specific energy consumption decreases by 52.4 %. The threshold fracturing pressure rapidly decreases as temperature increases and stabilizes, presenting an exponential trend. When the temperature exceeds 75.0 °C, the threshold fracturing pressure is maintained at around 10.0 MPa and no longer decreases with the temperature increase. In addition, three-dimensional (3D) damage field analysis highlights that the coal breaking mode shifts from a “water wedge” dominated mode to a “water wedge-thermal fracture” mode as temperature increases. Finally, the dynamic fracturing mechanism of coal under high-temperature conditions of water jet impact has been revealed. The research results of this paper provide a theoretical basis for the hydraulic permeability enhancement design of deep coal seams.

Mechanical mechanism of shear cavitating water jet dissociation of flake graphite

Abstract To obtain the mechanical mechanism of shear-type cavitation water jet dissociating flake graphite to improve the grinding technology of flake graphite, the motion state of flake graphite particles in shear-type cavitation water jet, the micro-jet impact process, the high-pressure elastic potential energy pressure release process, and the water wedge stretching process have been analyzed using the theory of hydraulic transport of liquid-solid two-phase, the theory of jets, the cavitation primordial principle, the principle of capacity conversion, and the water wedge action. The primary mechanical mechanism of shear cavitation water jet dissociation of flake graphite is collision friction effect, micro-jet impact, pressure release, and water wedge stretching effect, under these four kinds of loads individually or jointly, to achieve the purpose of removing the surface of flake graphite particles of the veinstone minerals to realize the dissociation of flake graphite. Moreover, the collision friction, pressure release, and water wedge stretching effects destroy the material under tensile stress to remove the veinstone minerals, and the micro-jet impact effect is the destruction of the material under compressive stress to remove the veinstone minerals.

Study on the free surface evolution and slamming pressure of curved-wedge water entry using a Riemann-smoothed particle hydrodynamics method

The present study aims to provide a deep understanding of curved wedge water entry. It involves a numerical simulation investigation into the kinematic and dynamic properties of water entry for two curved wedges with deadrise angles of 25° and 35°. The meshless Riemann-smoothed particle hydrodynamics (SPH) model embedded with an acoustic damper is developed to simulate these violent water entries. The validation of the Riemann-SPH accuracy is confirmed through comparison with experimental data, and subsequently, we make a systematical simulation study on curved wedge water entry, including a comparative study of free surface evolution and pressure distribution at different curvatures and drop heights. Furthermore, the kinematics analysis of velocity and displacement of curved wedges and time domain characteristics of slamming pressure loads on both sides of the wedge are investigated. It is revealed that the pressure distribution is symmetrical, with high-pressure regions forming near the bottom of the wedge and gradually propagating outward. The free surface profiles are symmetrical, with deeper depressions formed by sharper wedges. The entry depth and velocity are correlated with the initial theoretical entry velocity, and the rate of speed decline varies with the curvature of the wedge. The slamming pressure loads exhibit distinct time-domain patterns, with lower pressure loads by sharper wedges.

Experimental study on rock-breaking characteristics of advanced premixed abrasive water jet

ABSTRACT To investigate the rock-breaking characteristics of the advanced premixed abrasive water jet, experiments of abrasive water jet eroding granite were carried out. The micro-failure morphology of erosion pits was observed and analyzed by CT (Computerized Tomography) and SEM (Scanning Electron Microscope). The results show that the difference in erosion effect caused by different rock breaking pressures is due to the difference in impact kinetic energy. The higher the jet pressure, the higher the impact kinetic energy of abrasive particles, and the erosion effect is enhanced. The difference in erosion effect caused by abrasive types is that the harder abrasives produce greater cutting force on the rock and consume less fracture surface energy. The CT scanning results show that the conical crack at the bottom is caused by the stamping action of abrasive particles and expands rapidly under the action of a water wedge, the action of reflective particles makes the erosion holes appear spindle-shaped. The results of SEM show that the sidewalls of the erosion pit are dominated by the cutting and fatigue-crushing effects of reflected abrasives. The bottom of the erosion pit is mainly driven by the punching action of the incident abrasive.

Shoreline subsurface dams to protect coastal aquifers from sea level rise and saltwater intrusion

Fresh groundwater in arid and highly populated regions is limited. In coastal aquifers, the deterioration of fresh groundwater is accelerated by saltwater intrusion, primarily occurring through lateral encroachment and vertical movements in the proximity of discharging wells. Coastal regions have high salinity due to saline intrusion, where many abstraction wells are turned off by this high salinity, which leads to increased freshwater supply costs. This study investigates the performance of new approach using the shoreline subsurface dams (SSDs) for mitigating the saline water wedge in coastal aquifers, where the dams are installed at the shoreline (distance from shoreline = 0). Specifically, the current study's novelty is testing the effectiveness of SSDs by different relative heights ranging from 0.05 to 0.50 in the test case (Henry problem) and from 0.09 to 0.53 relative to the aquifer thickness in the field scale aquifer (Biscayne aquifer, Florida, USA). The results showed an exponential increase in salt repulsion for increasing SSDs height, reaching a maximum of + 0.70%, + 1.80%, + 3.25%, + 5.80%, + 10.45%, and + 18.40% for the dam height to aquifer thickness ratios of 0.09, 0.18, 0.26, 0.35, 0.44 and 0.53, respectively, in the field scale case. The SSDs increase the freshwater storage at the coastal zones where the low salinity occurs and reduces the freshwater supply cost. Despite the positive impact of height on repulsion, important factors such as economics, construction aspects, geographical suitability, and environmental impacts must be considered for real applications. This is crucial to develop feasible solutions applicable globally under the growing pressure of sea level rise.

Study on the Control of Saltwater Intrusion Using Subsurface Dams

Subsurface dams are widely used to prevent saltwater intrusion, with good results. This blockage often leads to an accumulation of pollutants and salt on the inland and seaside of the dam, respectively. While the latter is intended, the former effect is not desired and poses a huge problem in groundwater management. In order to quantitatively address this issue and clarify the impact of subsurface dam height, location, and the head difference for the saltwater and freshwater boundary on saltwater wedges and fresh groundwater discharge, a flow tank and numerical model were constructed. The results indicate that there was an optimal effective dam height and location (also the minimum effective dam location) for controlling saltwater intrusion, which corresponded to the maximum groundwater and freshwater discharge. When the various conditions of the numerical model were set according to the flow tank and the dam was 15 cm away from the saltwater boundary, the minimum effective dam height was equal to the aquifer thickness multiplied by 0.36. The dam height reached a height that was slightly higher than the minimum effective height, namely, the ratio of dam height to aquifer thickness was 0.38, which revealed that the freshwater discharge reached its maximum at 22.71 cm3/min, the saline water wedge area was the smallest at 378 cm2, and the prevention effect of saltwater intrusion was the best. Building a dam too high, that was, the ratio of dam height to aquifer thickness exceeded 0.38, resulted in an increased saltwater wedge area and exacerbated aquifer pollution. When the dam was located at the minimum effective distance for preventing saltwater intrusion under a certain dam height and head difference between saltwater and freshwater boundary, that was, the ratio of the distance of the dam to the saltwater boundary to the total length of the aquifer was 0.063, the distance of the dam to the saltwater boundary was the minimum effective distance. Compared to other effective distances, when the dam was at the minimum effective distance, the freshwater discharge reached its maximum at 22.71 cm3/min, and the saltwater wedge area was the smallest at 378 cm2. These conclusions provide a theoretical reference for the impact of subsurface dam construction on the saltwater wedge. This study examines the impact of tides and waves on the water head of the saltwater boundary, and it is also necessary to verify these conclusions through actual field experiments. We will investigate this in future work.

Study on the effect of cavity oscillation on wedge water entry with a multiphase smoothed particle hydrodynamics model

Previous Smoothed Particle Hydrodynamics (SPH) study on water entry issues has primarily been conducted for the load analysis of impact phase rather than the cavity oscillation effect because the calculation and simulation of this complex physical process are more complicated and time consuming. In order to increase computational efficiency and accuracy, the multiphase δ+-SPH model is combined with Adaptive Particle Refinement technology to investigate the whole process of the wedge's water entry. The hydrodynamic phenomena in the stages before cavity closure for the four cases with different Froude numbers (Fn) are compared and analyzed. After the cavity is pinched off, the wedge exhibits kinematic oscillation. Our test shows that the adoption of sound speed has a significant influence on the oscillation period and peak value of closed cavities in weakly compressible SPH calculations. Then, a suitable sound speed adoption is selected to simulate the oscillatory phenomenon accurately. Comparing the pressure profile with the surface pressure and acceleration of the wedge at the same time, it can be concluded that the oscillation of the hydrodynamic load on the wedge is caused by the pressure oscillation in the closed cavity. Especially for the case of low Fn, the pressure peak on the wedge's surface in the oscillation stage is even greater than the pressure load in the impact stage. The peak pressure of closed cavity is positively correlated with Fn and negatively correlated with Euler number (Eu). Finally, by analyzing the influence of wedge width and impact velocity, it is found that the oscillation period of the closed cavity is related to the morphology of the cavity. The larger the aspect ratio of the closed cavity, the longer the oscillation period.

Study of the water entry and exit problems by coupling the APR and PST within SPH

In this manuscript, the adaptive particle refinement (APR) and particle shifting technique (PST) are coupled and applied to investigate the entire process of water entry and exit. The PST implementation for various types of particles is quantitatively discussed in detail in the coupled APR-PST approach. A comprehensive analysis of different APR-PST coupled schemes is conducted with crucial variables compared and analyzed for the first time. The stability, accuracy and robustness of the developed numerical model are verified by three benchmark tests: 2D wedge water entry, 2D cylinder water exit and 2D cylinder water entry and exit. The obtained results show that the current model can ensure the overall computational precision in the situation of local refinement, which indicates it is a viable way to solve the problems of water entry and exit.

Study on the influence mechanism of material damage on the cavitation erosion properties of hydraulic concrete

Flood releasing safety is one of the three major safety problems of high dams due to the high-water head and large discharge, and the safety problems caused by cavitation erosion are increasingly prominent, which has become one of the challenging problems for the safety of high dam flood discharge. Particularly, flood discharge and energy dissipation structures are susceptible to varying degrees of damage under external loading and material performance degradation. However, the action mechanism of damage-cavitation erosion for concrete remains unknown and unclear. In this paper, the cavitation erosion properties of concrete with different damage variables and the influence mechanism of damage-cavitation erosion are systematically studied. Based on the ultrasonic cavitation erosion tests of undamaged and damaged concrete, it is found that the mass loss, harshness, volume of pits, and depth of damaged concrete increased rapidly at first and then slowly, the maximum loss rate is almost dependent on the degree of damage, and its relationship with the damage degree can be described by a piecewise linear function. More importantly, a damage variable threshold for the step surge of concrete cavitation erosion is suggested. The cementitious material in damaged concrete is more prone to cavitation erosion due to the potential microcracks caused by the damage. Compared with the results of tests and simulations, the incentive mechanism of the surge of concrete cavitation erosion due to the concrete damage - microcrack initiation - strength and fatigue life reduction - microjet impact - water wedge excitation in cracks - development, expansion, and penetration of erosion pits is revealed. The influence mechanism revelation of damage-cavitation erosion for concrete will enrich the theory and technology of cavitation erosion risk assessment for hydraulic concrete structures.

Surface removal of ductile metal using cyclic low-frequency impact of a discrete particle-less waterjet

The discrete waterjet (DWJ) offers advantages in material removal because of the cyclic impact loading, but the specific removal characteristics and corresponding mechanisms have not been yet fully understood. Therefore, the flow field and material removal characteristics of the DWJ were studied through numerical and experimental methods, including the velocity and impact pressure distribution, surface morphology, quantitative statistics of erosion crater, and fractography under different jet pressures and exposure times. The results indicate that mechanical interruption has a positive impact on increasing the maximum velocity (53.0% at 30 MPa) of the waterjet head and altering the impact pressure distribution, resulting in an asymmetric erosion crater with a tapering groove along the edge. Meanwhile, the DWJ has superior working efficiency (higher erosion area, depth and volume) and energy utilization (lower specific energy) than the continuous waterjet (CWJ), while avoiding the unfavorable high crater lips. A large amount of material removal does not necessarily occur in the initial stage of waterjet impact, and it is related to material properties, waterjet parameters and specific evaluation indexes. The increase of waterjet pressure accelerates the material removal process and improves the energy consumption efficiency. The materials removing process is divided into four stages: surface deformation due to the cyclic impact pressures, surface break-ups localized near the surface unevenness, independent fragment forming mainly by water wedge pressure, and larger removal of materials due to these cyclic processes.

An experimental study on the erosion of sandstone by self-excited oscillation cavitation waterjet in submerged environment

Self-excited oscillation cavitation waterjet (SOCW) has good prospects for application in deep sea mineral extraction of its cavitation characteristics. This study conducted the erosion experiments of three types of sandstone, red sandstone, white sandstone, and black sandstone by SOCW under a submerged environment. The erosion characteristics of three types of sandstones under the impact of SOCW at various erosion times, standoff distance, and pressure were compared. It was found that, a) Red sandstone with larger porosity is more likely to produce a large damage area and has the best rock breaking effect. Taking the standard working condition of this experiment as an example (t = 50s, Pj = 16 MPa, S/De = 4), the erosion depth of red sandstone can reach 1.9 times that of white sandstone and 5.5 times that of black sandstone; the erosion area can reach 19.6 times that of white sandstone and 6.2 times that of black sandstone; the erosion quality can reach 5.2 times that of white sandstone and 7.4 times that of black sandstone. b) With the increase of erosion time and erosion pressure, the erosion index of sandstone shows an increasing trend. However, in this study, there is an optimal standoff distance S/De = 4 to maximize the erosion depth of the sandstone. Again, there is an optimal standoff distance to maximize the erosion hole area, S/De = 10 for the red sandstone and white sandstone, and S/De = 6 for the black sandstone. c) The special phenomenon of the pressure difference formed after the collapse of the SOCW bubble in the submerged environment, which acts on the moisture content fine pore space inside the sandstone, the fine pore zone, was observed by scanning electron microscope (SEM). The microscopic characterization of the water wedge effect was observed by computed tomography (CT), and the trend of crack development is shown by the binarization processed images of the sandstone internal damage section. This result can be a theoretical basis to guide the working parameters of nozzles in deep sea mining, especially for the selection of standoff distance.

Influence of moisture content and intermediate principal stress on cracking behavior of sandstone subjected to true triaxial unloading conditions

The presence of water has been confirmed to play an important role in affecting the failure properties of underground surrounding rock when subjected to complicated stress circumstances. In the current study, the crack propagation behavior of red sandstone affected by various moisture contents and intermediate principal stresses were investigated by using the QKX-YB200 true triaxial test system with unloading minimum principal stress. The experimental results demonstrate that the failure mode can be divided into shear, tension with shear, and slabbing. A clear observation of the fractured specimen shows that the extensional cracks tend to increase while shear cracks gradually diminish with the increase of moisture content and intermediate principal stress. For natural sandstone (with lower moisture content), the transition of failure mode from shear to slabbing requires higher intermediate principal stress. However, with the increase of moisture content, the occurrence of slabbing failure requires lower intermediate principal stress. The analysis of failure process indicates that the presence of water may restrain the possibility of rockburst, and the intermediate principal stress exhibits distinct functions in the failure behavior of natural and saturated sandstone. The surface microscopic morphological characteristics and acoustic emission signal feature were also analyzed to validate the transformation of the cracking mode. The current research indicated that the water-induced micro defect and damage effect, “water wedge” effect, intermediate principal stress effect are the key factors that contribute to the final slabbing failure in immersed hard rocks under true‑triaxial unloading conditions.

Mesh generation for underwater acoustic modeling with KRAKEN

Underwater sound modeling is applied in several environmental studies, from assessing underwater noise induced by offshore wind farms to the influence of climate change on ocean temperature. One of the most well-known underwater acoustics models is KRAKEN, an open-source code requiring a mesh to simulate 3D environments. This paper presents OMesh2KRAKEN, a software toolkit that uses OceanMesh2D to generate unstructured meshes for KRAKEN based on realistic environmental data. Two practical study cases in the North Atlantic are presented and discussed. In addition, an idealized 3D shallow water wedge was simulated. Practically, OMesh2KRAKEN can assist in implementing underwater acoustic modeling studies from deep waters to nearshore regions where, for instance, sound propagation maps are required. Indeed, higher mesh resolutions may be required for areas with complex bathymetric features. In these cases, the new tool presents several advantages as it automatically implements different mesh resolutions in areas of interest and prepares the respective environmental files for acoustic computations.

Experimental investigation of the creep damage evolution of coal rock around gas extraction boreholes at different water contents.

The creep process of the coal rock around the extraction boreholes under stress-water coupling is an important factor affecting the stability of the boreholes. To study the influence of the water content of perimeter of the coal rock around the boreholes on its creep damage, a creep intrinsic model considering water damage was established by introducing the plastic element model from the Nishihara model. To study the steady-state strain and damage evolution of coal rocks containing pores, and verify the practicality of the model, a graded loading water-bearing creep test was designed to explore the role of different water-bearing conditions in the creep process. The following conclusions were obtained: 1) water has a physical erosion and softening water wedge effect on the perimeter of the coal rock around the boreholes, which affects the loading axial strain and displacement of the perforated specimens; 2) an increase in water content reduces the time taken for perforated specimens to enter the creep phase, making the accelerated creep phase come earlier; 3) the parameters of the water damage model are considered to be exponentially related with the water content. The experimental data are similar to the results of the model parameters, and the model shows some practicality; 4) the damage variables in the accelerated creep phase increase rapidly throughout the creep process, leading to local instability in the borehole. The findings of the study provide important theoretical implications for the study of instability in gas extraction boreholes.

A Verification and Validation Study on a Loosely Two-Way Coupled Hydroelastic Model of Wedge Water Entry

_ The interaction between the structural response and hydrodynamic loading (hydroelasticity) must be considered for design and operation purposes of high-speed planing craft made of composites that are prone to frequent water impact (slamming). A computational approach was proposed to study the hydroelastic slamming of a flexible wedge. The computational approach is a loose two-way coupling between a Wagner-based hydrodynamic solution and a linear finite element plate model. Verification and validation (V&V) was performed on this coupled model. It was found that the model overpredicts rigid-body/spray root kinematics by <15% and hydrodynamic loading/ structural response by <26%. Introduction One of the primary constraints on the operational envelope of high-speed craft is slamming (water impact). Slamming occurs between the hull body and the water surface when a portion/whole of the craft exits the water and then reenters at high-enough velocity (Lloyd 1989; Faltinsen 2005). The frequent water impacts, which work like “water hammers,” along with their induced acceleration pose great jeopardy on hull structures as well as crew and instrument on-board (Yamamoto et al. 1985; Ensign et al. 2000; Hirdaris et al. 2014). With the growing use of lightweight materials, the interaction between the structural deformation and the hydrodynamic loading (hydroelasticity) becomes more prevalent. The current design criteria of high-speed craft are based on empirical procedures with no regard to hydroelasticity due to the lack of understanding of this complex phenomenon (DNV 2013; ABS 2016). Therefore, a better comprehension of hydroelastic slamming is the first step to designing more high-performance craft (Fu et al. 2014; Judge et al. 2020).

O2 and CO2 Responses of the Synaptic Period to Under-Ice Phytoplankton Bloom in the Eutrophic Razdolnaya River Estuary of Amur Bay, the Sea of Japan

Hydrological conditions are an important factor for aquatic ecosystems. Their contribution to stimulating phytoplankton bloom in eutrophic estuaries is not quite clear. We present the results of an outbreak of a phytoplankton bloom event observed in the eutrophic Razdolnaya R. estuary in 2022 from January 22 to February 23, when the estuary was covered by ice. The bloom spreads over 21 km from the river mouth bar to upstream in the near-bottom layer below the halocline. The Chl-a concentration in the bloom area increased from 15 to 100 μg/L, and the dissolved oxygen concentration from 350 to 567 μmol/kg at a rate of 11 μmol/(kg day) over the study period, while the CO2 partial pressure was reduced to 108 µatm in the most oxygen-supersaturated waters. The Thalassiosira nordenskioeldii Cleve sea diatom was the dominant phytoplankton species in the bloom area. The opposite trend was observed near the boundary of the saline water wedge penetration over 29 km from the river mouth bar to upstream where the dissolved oxygen concentration decreased from 140 to 53 μmol/kg over a month, and partial pressure of CO2 reached 4454 μatm. We also present the results obtained in February 2016 before and after a snowfall, when the ability of PAR to penetrate through the ice was impeded by a layer of snow. After the snowfall, photosynthesis in the under-ice water stopped and the oxygen concentration decreased to almost zero due to the microbiological destruction of the phytoplankton biomass. As such, the main effect of phytoplankton bloom is the formation of superoxia/hypoxia (depending on the light conditions), during the period of maximum ice thickness and minimum river discharge. Thus, this study demonstrates that the eutrophication in the future could lead to unstable ecosystems and large synoptic variations of dissolved oxygen and CO2 partial pressure of the estuaries.