Pressure Disturbances Research Articles

Perturbation energy extraction from a fluid via a subsurface acoustic diode with sustained downstream attenuation

Engineered subsurface structures inspired by phononic materials have shown favorable capabilities in flow control. Current efforts rely on tuning a structural resonance to the frequency of an unstable fluid mode, causing the deformations of the interfacing solid to destructively interfere with a wave-like flow instability. Although promising, the technique is most effective at targeting a single frequency mode with high-Q resonance. Additionally, several studies have shown the reduction in the perturbation energy to be spatially localized to the flow region above the subsurface strip, with a severely worsening effect downstream. Motivated by a desire to overcome these limitations, we present a different approach to methodically extract an undesirable pressure disturbance from a fluid column in a manner that capitalizes on the broad frequency range of a phononic bandgap, with the goal of permanently confining the perturbation energy within the subsurface structure. An acoustic diode (AD), i.e., a unidirectional transmitter of mechanical energy, comprised of a bi-layered phononic crystal and an auxiliary medium, interacts with a fluid cavity and provides a terminal energy sink. Two distinct ADs are presented that demonstrate active (time-variant) and passive (strain-dependent) paths to concept realization. The AD’s performance is described in terms of the time-transient energy distribution in the fluid and the interacting structure, as well as spatial wave profiles at critical time instants. The results show the system’s ability to achieve robust extraction of undesirable fluid oscillations with minimal residual energy. The concept is then tested in a fully developed plane channel flow with a superimposed perturbation, demonstrating the sustained nature of the subsurface AD’s energy trapping mechanism in addition to its ability to induce downstream attenuation.

Instability model of water–steam–liquid metal three-phase jet flow during steam generator tube rupture accident in a fast reactor

The steam generator tube rupture (SGTR) accident in a lead-cooled fast reactor (LFR) results in an injection of high-pressure subcooled water from the secondary circuit into the high-temperature liquid lead-bismuth eutectic (LBE) pool in the primary loop. Rapid depressurization and phase-change heat transfer generate the steam between the water jet and liquid LBE. Based on jet instability theory, this study develops a temporal instability model focusing on the water–steam–liquid LBE three-phase flow in a cylindrical coordinate to investigate the breakup characteristics of water jet. By introducing velocity and pressure disturbances and adopting a linear assumption to the hydrodynamic governing equations, a dispersion equation is developed, and jet characteristic parameters are then defined. The effects of various operating parameters and key dimensionless numbers are further studied. By solving the dispersion equation, it is found that smaller steam film thickness and higher steam velocity enhance jet instability. Increasing jet velocity and reducing jet radius accelerate jet breakup and promote droplet refinement, while at higher jet velocities, the influence of jet radius diminishes. Additionally, the co-flow of LBE with the jet and the viscosity effect of LBE both stabilize the water jet. This model enables quantitative prediction of the breakup behavior of water jets in liquid LBE during the initial stage of SGTR accident, aiming to reveal the fundamental mechanisms of the physical process and provide theoretical guidance for safety analysis of LFR.

Experiment research on the control method of automatically retained entry by roof cutting pressure relief within thick hard main roof longwall top coal caving panel

To address the large deformation of goaf-side entries resulting from intense dynamic pressure, a method involving automatically retained entry by roof cutting pressure relief (ARERC) technology is proposed for use in thick and hard main roof longwall top coal caving (THLTCC) panel. Both physical and numerical model experiments have been conducted to verify the effectiveness of ARERC technology in controlling deformation. The evolution laws of stress and deformation in the surrounding rocks of the retained entry and the mechanism of pressure relief by roof cutting are analyzed. Results indicate that this technique optimizes the roof structure of the roadway and interrupts roof stress transfer between the retained entry and goaf. Consequently, the maximum vertical stress on the roof-cutting side of the retained entry roof is generally lower than on the uncut side. The retained entry deformation undergoes four distinct stages behind the panel: the pressure relief stage, deformation stage, compaction stable stage and stabilization stage. Notably, the deformation stage exhibits the highest deformation rate for the roadway. Therefore, it is recommended to utilize single hydraulic props for temporary support during the deformation stage to prevent damage to the retained entry caused by dynamic pressure disturbance. Based on the above analysis, several recommendations are provided for the field application of ARERC technology. Finally, the results from engineering application show the effectiveness of ARERC technology in controlling the deformation of the goaf-side entry. This ARERC technology can be extended to other coal mines with similar geological conditions.

Dynamic structural characteristics and vibration susceptibility of Tongren loess under the influence of water content and confining pressure

Loess is extensively developed on both sides of the Longwu River, a tributary of the Yellow River, Tongren County, Qinghai Province. The engineering geological characteristics are complex, and landslide disasters are highly developed. Based on field geological surveys and physical property analysis of the loess in this area, this study analyzes the influence of water content, consolidation pressure, and soil disturbance on the dynamic characteristics of loess using GDS dynamic triaxial tests. The results show that Tongren loess has strong structural properties. Its dynamic constitutive relationship conforms to the Hardin-Dinevich hyperbolic model, where the parameters a and b decrease with increasing confining pressure and increase with increasing water content. The dynamic cohesion and dynamic friction angle both decrease with increasing water content, with the dynamic cohesion significantly affected, decreasing by 77% ~ 83% when saturated. However, the dynamic friction angle is less affected by water content changes, decreasing by 18% ~ 25% when saturated. Under dynamic conditions, the dynamic friction angle of Tongren loess is only 12 ~ 16°, making slopes composed of Tongren loess highly susceptible to instability and sliding under strong earthquake conditions. The dynamic structural properties of Tongren loess are significantly influenced by water content, with increasing water content destroying the joint structural strength of intact loess. Before reaching the plastic limit water content, the joint structural strength of intact loess decreases sharply with increasing water content, and then decreases slowly. The frictional structural strength shows an opposite trend. Under the same experimental conditions, the failure dynamic stress, maximum dynamic elastic modulus, and dynamic shear strength parameters of intact loess are generally greater than those of remolded loess, and the differences between them decrease with increasing water content. This study provides insights into the dynamic structural characteristics of Tongren loess, which can serve as a reference for understanding the formation mechanisms, stability analysis, and seismic design of loess landslides in the region.

Research on high-speed water entry similarity of multiscale vehicle based on two-parameter compensation of atmospheric pressure–density

The atmospheric pressure and density are important factors affecting the water entry cavity and load characteristics of the vehicle. However, it is difficult to take into account the equivalent simulation of the two in the scaled-down test. The use of atmospheric pressure–density two-parameter compensation may become a key means to achieve accurate scale similarity. In this paper, the evolution of the water entry cavity and the similarity of impact loads for multiscale models in different environments are studied. Aiming at the problem that the similarity conditions are difficult to meet in small-scale model test, a distortion compensation correction method is proposed. The results show that under normal pressure environment, as the scale ratio decreases, the cavity surface closes in advance, and the slamming load gradually decreases. Under reduced pressure environment, the influence of the “scale effect” is significantly reduced. As the pressure decreases, the cavity surface closure phenomenon is weakened, and the cushioning effect of the air cushion is reduced, resulting in an increase in the slamming load. Quantitative analysis shows that the atmospheric pressure mainly affects the pressure disturbance trend in the cavity, while the atmospheric density determines the scale of the cavity and the size of the model load. By adjusting the pressure and density parameters, the prediction deviation of the small-scale model test on the disturbance time of the prototype reentrant jet pressure can be controlled within 2.4%.

Transverse deformation waves in the non-isothermal lithosphere‒asthenosphere system

The features of the occurrence and propagation of transverse deformation waves in the elastic lithosphere – viscous asthenosphere system under non-isothermal conditions are studied in the approximation of a thin layer. In this case, the phase transition at the boundary of the layers, due to temperature and pressure disturbances, plays an essential role. The qualitative and quantitative properties of propagation of disturbances of thermomechanical fields have been studied in the long-wave approximation. It is shown that due to the energy supply from the non-isothermal asthenosphere, weakly attenuated wave packets can occur, which spread over thousands of km with a characteristic speed of about 100 km/year. This allows them to be considered as a possible trigger mechanism for the massive emission of methane from frozen sedimentary rocks into the atmosphere.

Analysis and Optimisation of Obstacle‐Crossing Performance of Electric Shovel Based on DEM‐MBD Coupling Method

ABSTRACTTo study and enhance the obstacle‐crossing performance of the electric shovel, an obstacle‐crossing model that employs a coupling methodology integrating the discrete element method (DEM) and multi‐body dynamics (MBD) is constructed. Secondly, the influence of grouser height (GH), track velocity (TV), slope inclination (SI) and slope height (SH) on obstacle‐crossing performance is investigated through DEM‐MBD simulation, with the objective of obtaining an obstacle‐crossing surrogate model through the Kriging method and Box‐Behnken experimental design. On this basis, two optimisation solutions for the obstacle‐crossing performance of the electric shovel are proposed based on a genetic algorithm (GA), and the corresponding obstacle‐crossing performances are analysed. The results demonstrate that the coupling effect between SI and SH exerts a considerable influence on the ground pressure coefficient (GPC), power and disturbance potential energy (DPE). When the optimal TV and GH are set at 0.1 m/s and 9.38 mm, the GPC, power and disturbance kinetic energy (DKE) are observed to diminish to varying degrees, thereby indicating that the obstacle‐crossing performance of the electric shovel has been enhanced.

Posterior reversible encephalopathy syndrome after COVID-19 in a patient with chronic renal failure

A 61-year-old man with chronic renal failure had an embolic stroke of undetermined source that was treated with warfarin. Five weeks later, the patient contracted coronavirus disease (COVID-19). Six days after the onset of COVID-19, high blood pressure (>200 ‍mmHg) and consciousness disturbance were reported. CT demonstrated symmetrical hypodensity areas in the bilateral cerebellar hemispheres. MRI revealed hyperintensity lesions in the bilateral cerebellar hemispheres and pons on the T2-weighted and fluid-attenuated inversion recovery images. Moreover, cerebellar lesions appeared as hyperintensity areas on apparent diffusion coefficient mapping. Based on these findings, a diagnosis of posterior reversible encephalopathy syndrome (PRES) was made. The patient was treated with antihypertensive drugs, and the consciousness level improved gradually. MRI after one month showed that the lesions had disappeared. PRES should be considered if the brain CT of patients with COVID-19 shows a low-density lesion, especially in patients with risk factors for PRES such as chronic renal failure or hypertension.

Unsteady Flow Mechanism of Impeller Stall Inception in a High-Pressure Ratio Centrifugal Compressor With Bleed Slots

Abstract The impeller stall inception in a high-pressure ratio centrifugal compressor with bleed slots was investigated by experiments and unsteady numerical analysis. This study reported that the flow instability of the internal flow was first initiated around the leading edge of the splitter blades and finally resulted in tip leakage flow instability at the leading edge of the main blades. The impeller stall consisted of a stall cell and rotated about 70% of the impeller rotational speed. Furthermore, a pressure disturbance occurs at the splitter blade leading edge before the main blade leading edge. The blockage within the passage of the suction side at the leading edge of the splitter blade was first increased because the leading-edge separation on the suction surface of the splitter blade was enlarged. The blockage within the passage of the pressure side was increased after that of the suction side stopped increasing. Therefore, the blockage development of both pressure and suction passage at the leading edge of the splitter blade was the main cause of the stall inception. Then, a longitudinal vortex was formed near the bleed slots and blocked the mainstream near tip side. Subsequently, the reverse flow region in the inducer was developed and extended to the impeller inlet. Finally, the flow angle to the main blade increased, the spillage occurred at a leading edge of a main blade, and the rotating stall was generated. The cause of impeller instability was the separation of the suction surface of the splitter blade and the formation of a stagnation region on the pressure surface at the splitter leading edge.

Rapid ventricular response atrial fibrillation in an uncontrolled hyperthyroidism patient

Hyperthyroidism, defined as elevated blood levels of thyroid hormone with reduced levels of thyroid-stimulating hormone (TSH). Atrial fibrillation (AF) is the most common cardiac complication in patients with hyperthyroidism. There is several pathophysiology of AF in hyperthyroidism such as an increase atrial pressure, ischemia, and ion disturbance of the myocardium. In hemodynamically unstable patients should be carried out electric cardioversion. The choice of rate or rhythm control is determined based on the case. Beta-blockers inhibit sympathetic activity in the AV node so that it can inhibit the ventricular rate. Antithyroid drugs are widely used in the management due to restoration of euthyroidism is fundamental in the management of hyperthyroidism related AF.

Possibility of Fluid Flow Characterization via a Geophysical Signal: Experimental Study on the Krauklis Wave Under Fluid Flow

AbstractKrauklis waves are generated by pressure disturbances in fluid‐filled cavities and travel along the solid‐fluid interface. Their far‐field radiation, observed in seismic data from volcanoes or hydraulic fracturing, is known as long‐period events. Characterized by low velocity and resonance, Krauklis waves help estimate fracture size and discern fluids in saturated fractures. Despite numerous theoretical models analyzing Krauklis waves, the existing paradigms are founded on static flow conditions. However, in geological contexts, the assumption of static flow may not be valid. We developed an experimental apparatus using a tri‐layer model consisting of a pair of aluminum plates to examine the effect of fluid flow on Krauklis waves. We employed an infusion syringe pump to inject fluids into the fracture under different flow rates. We used water, oil, and an aqueous solution of Polyethylene glycol as fracture fluids. We calculated resonant frequency, phase velocity, and quality factor to characterize the Krauklis waves. Our findings reveal that an increase in flow rate leads to a higher phase velocity, higher quality factor, and a shift to higher resonant frequency when the flow is in the direction of initial wave propagation while decreasing amplitude. Additionally, when the flow is in the opposite direction of initial wave propagation, we note higher wave absorption and distortion of the Krauklis waves. Our observations unequivocally affirm that fluid flow leaves strong signatures on the Krauklis waves, providing a robust basis for characterizing fluid dynamics within geological settings through the analysis of Krauklis wave.

Dynamic large-eddy simulation of hypersonic transition delay over broadband wall impedance

Three-dimensional numerical simulations of hypersonic boundary layer transition delay due to porosity representative of carbon-fibre-reinforced carbon-matrix ceramics (C/C) were carried out on a 7 $^{\circ {}}$ half-angle cone for unit Reynolds numbers $Re_m=2.43 \times 10^6$ – $6.40\times 10^6\ \text {m}^{-1}$ , at the free-stream Mach number $M_\infty =7.4$ , for both sharp and 2.5 mm nose tip radii. A broadband time-domain impedance boundary condition was used to model the acoustic effects of the porous surface on the flow field. A quasi-spectral sub-filter-scale dynamic closure was adopted to stabilize the computations upon turbulent breakdown under extreme cooling conditions, with wall-to-adiabatic temperature ratio of $T_{w}/ T_{ad} \simeq 0.08 $ , while accurately recovering the growth rates of the unstable modes present in the early transition stages. Good agreement is observed with the reference experimental data, both in terms of the predicted extent of the transition delay and the measured second-mode frequency spectrum. The latter is strongly modulated by the formation of near-wall low-temperature three-dimensional streaks. Pressure disturbances concentrate in corridors of locally thickened boundary layer, with frequencies lower than what predicted by linear theory. Here, trapped wavetrains are formed, which can persist long into the turbulent region. Finally, it is shown that the presence of a porous wall simply shifts the onset of turbulence downstream, without affecting its structure.

THE EVOLUTION OF A CLAY CRUST IN A BOREHOLE

Based on the previously proposed quasi-stationary model of clay crust formation when drilling wells in depth intervals with permeable rocks, software was created and computational experiments were performed, which made it possible to clarify the contribution of various physical parameters to the process of its growth.Based on the analysis of the results of computational experiments, the contribution of the physical parameters of the formation and clay crust to the dependence of its size on time has been clarified. The model assumes that the filtration pressure fields are described by stationary piezo conductivity equations. This made it possible to construct explicit dependences of pressure, thickness of the clay crust, radius of the zone of pressure disturbances in the reservoir during drilling and other parameters on time. Simple approximate formulas have been found for the dependence of the thickness of the clay crust, the filtration rate and the radius of the pressure disturbance zone in the reservoir on time, which describe their evolution with high accuracy.Based on the analysis of the calculation results, it was found that the thickness of the clay crust significantly depends on the permeability of the reservoir and repression, and these parameters determine the process of its formation. The porosity of the collector makes a smaller contribution, and the filtration and capacitance parameters of the clay crust have little effect on its thickness.New possibilities for estimating the physical parameters of reservoirs based on cavernometry have been identified. The solution of this problem is especially important for horizontal wells, in which the clay crust intervals have a significant length, and its formation occurs under conditions of a wide range of reservoir properties of the formation. The considered problem is of practical importance, since the zone of penetration of drilling mud filtrate into the formation has a screening effect on the use of geophysical methods to determine reservoir saturation. The results obtained can be used both to improve the interpretation of geophysical methods and to develop those.When conducting computational experiments using an exact formula, the stochastic behavior of the calculated curves was found. It was found that the noted effect is associated with rounding error, and in this sense is a manifestation of the features of the processor. An approach is proposed to eliminate the detected stochastic errors.

Silk Flocked Flexible Sensor Capable of Wide-Range and Sensitive Pressure Perception.

In recent years, there have been advancements in high-performance soft sensors with simultaneous moderate sensitivity and wide linearity. However, it remains challenging to combine high-efficiency production and high performance for soft sensors. The skin and hair structure provide an elegantly simple sensing model, where hair acts as signal receptors and basal skin acts as signal processors. Herein, we used efficient electrostatic flocking and extrusion printing to engineer comb-shaped electrodes with conductive polydimethylsiloxane (PDMS) flocked with conductive silk fibers as a biomimetic flexible sensor. The mechanical and electrical properties of modified PDMS and silk fibers were characterized to optimize the functionalization process. The sensor unit exhibited a high linear range up to 2,000 kPa and a competitively good sensitivity of 0.0285 kPa-1 in the contact mode with conductive materials, as well as good resolution in the noncontact mode. Such sensors and a sensor array demonstrated potential applications for detecting pressure disturbances from acoustic activity and for human-robot interactions. We anticipate that the straightforward design and facile fabrication of soft sensors with vertical fibrous morphology for perception will open new avenues for the next generation of high-performance soft sensors integrated with artificial intelligence.

On space–time diversity in shock train self-excited oscillation mode during wide-range evolution in a scramjet isolator

The shock train self-excited oscillation can induce combustor instabilities and reduce engine margin. In a dual-mode scramjet, the shock train undergoes a complete evolution process, exhibiting structural changes closely tied to this inherent unsteadiness. This study aims to elucidate the space–time diversity in shock train self-excited oscillation mode and the underlying mechanisms during wide-range evolution. The experimental investigations were conducted at Ma = 1.95, capturing the complete evolution of the shock train. The results indicate the evolution can be categorized into three regimes based on structural characteristics. In regime I, the shock region gradually forms, followed by the occurrence of the mixing region in regime II. Regime III corresponds to inlet unstart. In regime II, isolator outlet pressure fluctuations exhibit higher frequency and lower amplitude compared to regime I, while the shock motion demonstrates lower frequency and higher amplitude. The shock train behaves in a large-scale, low-frequency (1.53 times the duct height, 10 Hz) unsteady motion in regime II, posing a potential threat to engine operation. Coherence and phase analysis reveal the disturbance source originates downstream. Proper orthogonal decomposition modal analysis shows two oscillation modes: low-frequency components correspond to shock motion, and high-frequency components correspond to pressure fluctuations across the entire pseudoshock. The propagating of downstream disturbance differs between the two regimes. In regime I, the shock train exhibits rigid-body motion synchronously. In regime II, the relative motion between each shock wave and the cumulative effect of pressure disturbance lead to frequency decay upstream, amplifying the shock train motion.

Passive Control of the Flow Around a Rectangular Cylinder with a Custom Rough Surface

Motivated by existing techniques for implementing roughness on cylinders to control flow disturbances, we performed delayed detached eddy simulations (DDES) at Re = 6×106 that generated unsteady turbulent flow around a rectangular cylinder with a controlled wrinkled surface and a 1:4 aspect ratio. A systematic study of the roughness effect was carried out by implementing different configurations of equally spaced grooves and bumps on the top-surface of the cylinder. Our results suggest that groove geometries reduce energy dissipation at higher rates than the smooth reference case, whereas bumped cylinders produce relative pressures characterized by a sawtooth pattern along the middle-upper part of the cylinder. Moreover, cylinders with triangular bumps increase mean drag and lift forces by up to 8% and 0.08 units, respectively, while circular bumps increase vorticity and pressure disturbances on the wrinkled surface. All of these effects impact energy dissipation, vorticity, pressure coefficients, and flow velocity along the wrinkled surface. Both the surface-manufactured cylinders and the proposed visualization techniques could be replicated in a variety of engineering developments involving flow characterization in the presence of roughness.

The Impact of Blood Pressure Rhythm and Perioperative Blood Pressure Variability on Short-Term Prognosis in Patients with Type A Aortic Dissection.

Aims/Background Previous studies have indicated a strong correlation between disturbances in blood pressure (BP) circadian rhythm and major cardiovascular adverse events. Similarly, blood pressure variability (BPV) has been closely linked to cerebral small vessel disease and leukoaraiosis. This study aims to investigate the relationship between BP rhythm and BPV with the short-term prognosis of patients with Type A aortic dissection, offering insights for targeted perioperative nursing interventions and improving patient outcomes. Methods This retrospective study included patients undergoing surgical treatment for Type A aortic dissection at Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences) from June 2022 to March 2024. The study followed patients from the completion of surgery to 30 days postoperatively, with all-cause mortality within 30 days as the endpoint representing poor short-term prognosis. Clinical data were compared along with: types of BP rhythm; BPV parameters including the mean 24-hour systolic BP (24hSBP), 24-hour diastolic BP (24hDBP), and pulse pressure; and the coefficient of variability (CV) for 24hSBP, 24hDBP, and pulse pressure. Multivariate logistic regression analysis was utilized to identify risk factors for poor short-term outcomes in these patients, and receiver operating characteristic (ROC) curves were plotted to assess the predictive value of BP rhythm types and BPV indicators. Results The study ultimately included 115 participants, with 31 deaths occurring within 30 days post-surgery, resulting in a postoperative mortality rate of 26.96%. The multivariate logistic regression analysis revealed that white blood cell count, neutrophil count, non-dipping BP rhythm, pulse pressure, and the CV for 24hSBP, 24hDBP, and pulse pressure, were significant risk factors for poor short-term prognosis (p < 0.05). The ROC curve analysis demonstrated that non-dipping BP rhythm, pulse pressure, 24hSBP-CV, 24hDBP-CV, and pulse pressure-CV had areas under the curve (AUC) of 0.685, 0.749, 0.751, 0.773, and 0.763, respectively. The combination of these indicators yielded the highest AUC at 0.918. Conclusion A combination of BP rhythm and BPV indicators provides significant predictive value for poor short-term outcomes in patients with Type A aortic dissection. Clinicians and nursing staff can use these features to formulate targeted preventive measures.

3T-3D FLAIR MRI in Menière's disease: associated profiles with clinical symptoms and electroacoustic characteristics.

Diagnosis of Menière's disease relies on clinical symptoms. Injected 3T MRI can show endolymphatic hydrops (EH), but correlation with the clinical status of MD, (probable -PMD or definite-DMD) remains doubtful. We revealed endolymphatic pressure disruption through functional exploration and verified if it was associated with an EH through MRI. We prospectively analyzed 3D3T FLAIR MRI of DMD and PMD patients. All of them underwent electrocochleography (EcoG), distortion-product otoacoustic emissions (DPOAEs), and videonystagmograhy (VNG). Amplitudes of summating potential (SP) and cochlear nerve action potential (AP) were measured on EcoG. DPOAE-phase was collected at 1kHz for the 2f1-f2 DPOAE between sitting and laying position. A SP/AP ≥ 40% and a DPOAE phase-shift > 40° revealed pressure disruption. 39 patients (25 women, 53 y.o. 20-78), were included, with 32 DMD ears and 11 PMD ears. MRI was performed in a median of 21 days [0; 68] from the MD incident. Audiovestibular exploration took place 41 days after the crisis [0;83]. MRI revealed an EH in 71.9% and 27.2% of DMD and PMD, respectively. When combining functional explorations and MRI, testing was positive in 97% for DMD and 82% for PMD. When abnormal (59%), VNG mainly showed hyporeflexia in the diseased ear. In patients suffering from DMD or PMD, with endolymphatic pressure disturbances confirmed by combined DPOAE-phase and EcoG, 3T 3D MRI reveals EH mostly in DMD but rarely in PMD. This seems to confirm that disturbance of endolymphatic pressure precedes EH.

Changes in turbulent processes caused by atmospheric gravity waves from troposphere

We have determined that changes in temperature and wind speed recorded in the Earth‘s upper atmosphere above tropospheric sources (hurricanes) can be explained by the propagation of atmospheric gravity waves (AGW). We carried out modeling of the propagation of AGW with a period of 65 min and kx=10−5 m−1 using multi-layer methods in a non-homogeneous, non-isothermal atmosphere, taking into account viscosity and thermal conductivity. We obtained that disturbances in the horizontal component of the velocity are five times greater than the increase in the vertical component of the velocity, and temperature changes can reach 30 K. We should note that the disturbances of temperature and pressure as a result of AGW spreading are superimposed onto the usual view of changes of pressure and temperature with the altitude and reach the maximum amplitude in the range from 90 to 100 km. The obtained changes in the temperature of the upper atmosphere and the velocity with height as a result of the presence of AGW made it possible to estimate the values of the coefficients of turbulent viscosity and thermal conductivity in the upper atmosphere of the Earth above tropospheric energy sources. Intensification of turbulent processes was recorded in the range of altitudes from 75 to 100 km.

Momentum, energy and vorticity balances in deep-water surface gravity waves

The particle trajectories in irrotational, incompressible and inviscid deep-water surface gravity waves are open, leading to a net drift in the direction of wave propagation commonly referred to as the Stokes drift, which is responsible for catalysing surface wave-induced mixing in the ocean and transporting marine debris. A balance between phase-averaged momentum density, kinetic energy density and vorticity for irrotational, monochromatic and spatially periodic two-dimensional water waves is derived by working directly within the Lagrangian reference frame, which tracks particle trajectories as a function of their labels and time. This balance should be expected as all three of these quantities are conserved following particles in this system. Vorticity in particular is always conserved along particles in two-dimensional inviscid flow, and as such even in its absence it is the value of the vorticity that fundamentally sets the drift, which in the Lagrangian frame is identified as the phase-averaged momentum density of the system. A relationship between the drift and the geometric mean water level of particles is found at the surface, which highlights connections between the geometry and dynamics. Finally, an example of an initially quiescent fluid driven by a wavelike pressure disturbance is considered, showing how the net momentum and energy from the surface pressure disturbance transfer to the wave field, and recognizing the source of the mean Lagrangian drift as the net momentum required to generate an irrotational surface wave by any conservative force.