Pressure Disturbances Research Articles

Impacto del ejercicio físico en variables relacionadas con el bienestar emocional y funcional en adultos mayores

Background and aimThe benefits of the physical exercise in aging, and specially in frailty, have been associated with reduced risk of mortality, chronic disease, and cognitive and functional impairments. Multi-component training, which combines strength, endurance, balance, and gait training, represents the most beneficial kind of physical exercise in older adults. MethodsGiven the effectiveness of the multi-component training, a physical exercise program «Actívate» (based on the methodology Vivifrail), with the focus on «active aging», was conducted in the present study. Forty-nine older adults over 60 years participated in this program. ResultsThe physical exercise intervention led to a reduction in diastolic blood pressure, pain threshold and sleep disturbances (e. g. hypersomnia) (t ≥ 2.72, p < 0.01), as well as an increase of walking speed (t = 7.84, p ≤ 0.001). Further, quality of life factors (GENCAT scale), like emotional well-being, personal development, physical well-being, self-determination, and social inclusion, were greater after intervention (t ≥ −2.06, p < 0.05). ConclusionsThese findings underline the benefits of multi-component training in functionality of older adults, and further, provide relevant aspects about the modulation of pain perception, sleep disturbances, social factors and physical and emotional well-being. Physical exercise programs such as «Actívate» should be promoted, in order to encourage healthy lifestyle habits, in the older adults’ population.

A comprehensive analysis of transient pressure and rate data from CO2 storage projects in a depleted pinnacle reef oil field complex, Michigan, USA

Pressure and rate data are commonly recorded as part of a basic monitoring program in CCS projects. This paper discusses the application of multiple analytical techniques to interpret pressure and rate transient data from CO2 injection and storage operations. The techniques of interest, i.e., injection-falloff analysis, injectivity/productivity index analysis and pressure pulse arrival time analysis, are commonly used in the oil and gas industry to assess reservoir properties, but not well known in the CCS literature (especially the last two). Injection-falloff analysis involves log-log pressure derivative plotting for the falloff data and history-matching of the entire injection-falloff sequence to determine permeability. In the injectivity/productivity index analysis, rate-normalized pressure buildup is plotted against material balance time or ratio of cumulative injection to injection rate to determine the injectivity index (ratio of injection rate to stabilized pressure buildup) which can be related to the permeability-thickness product. The arrival time analysis identifies the arrival of a pressure disturbance (∼0.1 psi change from ambient) to determine the hydraulic diffusivity from which permeability can be estimated. The applicability of these techniques is demonstrated via illustrative examples from multiple wells in different pinnacle carbonate reefs undergoing CO2-EOR in Northern Michigan. The paper ends with a discussion of the relative merits of each interpretive technique, as well as recommendations that could be useful for other field projects.

The Effect of Pressure Disturbances on the Heating of the Plate Surface in the Strong Interaction Regime

The results of an experimental wind-tunnel investigation of the plate surface heating in the strong viscous-inviscid interaction regime are presented. It is shown that In the presence of a wedge mounted in the vicinity of the trailing edge of the plate the temperature distribution over the plate surface ahead of the wedge considerably changes up to the leading edge, as compared with the case of flow past the same plate in the absence of the wedge. The boundary layer flow is not steady, since during the run the surface temperature grows continuously, the temperature distribution itself along the plate surface being variable. It is established that in an unsteady boundary layer the upwind propagation of pressure disturbances produced by a thin wedge is fundamentally different in nature from the disturbance propagation in the case of flow past a plate with a constant surface temperature.

Long wave generation and coastal amplification due to propagating atmospheric pressure disturbances

Meteotsunamis are long waves generated by displacement of a water body due to atmospheric pressure disturbances that have similar spatial and temporal characteristics to landslide tsunamis. NAMI DANCE that solves the nonlinear shallow water equations is a widely used numerical model to simulate tsunami waves generated by seismic origin. Several validation studies showed that it is highly capable of representing the generation, propagation and nearshore amplification processes of tsunami waves, including inundation at complex topography and basin resonance. The new module of NAMI DANCE that uses the atmospheric pressure and wind forcing as the other inputs to simulate meteotsunami events is developed. In this paper, the analytical solution for the generation of ocean waves due to the propagating atmospheric pressure disturbance is obtained. The new version of the code called NAMI DANCE SUITE is validated by comparing its results with those from analytical solutions on the flat bathymetry. It is also shown that the governing equations for long wave generation by atmospheric pressure disturbances in narrow bays and channels can be written similar to the 1D case studied for tsunami generation and how it is integrated into the numerical model. The analytical solution of the linear shallow water model is defined, and results are compared with numerical solutions. A rectangular shaped flat bathymetry is used as the test domain to model the generation and propagation of ocean waves and the development of Proudman resonance due to moving atmospheric pressure disturbances. The simulation results with different ratios of pressure speed to ocean wave speed (Froude numbers) considering sub-critical, critical and super-critical conditions are presented. Fairly well agreements between analytical solutions and numerical solutions are obtained. Additionally, basins with triangular (lateral) and stepwise shelf (longitudinal) cross sections on different slopes are tested. The amplitudes of generated waves at different time steps in each simulation are presented with discussions considering the channel characteristics. These simulations present the capability of NAMI DANCE SUITE to model the effects of bathymetric conditions such as shelf slope and local bathymetry on wave amplification due to moving atmospheric pressure disturbances.

Harbor resonance triggered by atmospherically driven edge waves

It has been observed and theoretically proved that large tsunami-like waves can be caused by moving pressure disturbances along the shoreline. Since serious disasters due to meteorological tsunamis usually occurred in long and narrow harbors or bays, this study focuses on the resonance response of a harbor to atmospheric disturbances moving along the shoreline. The possibility and mechanism for severe oscillation occurring in the harbor have been investigated. The results show that severe oscillations can occur after a disturbance passes over, but not always. In that case, harbor resonance corresponding to one of harbor eigen frequencies has been excited. It is found that the excitation of harbor resonance mainly depends on the translational speed and spatial scale of atmospheric disturbance. Large oscillation occurs only within a small range of the translational speed and spatial scale, for a specific harbor which eigen frequencies are fixed. It is greatly associated with the amplitude of edge waves induced by disturbances. A criterion has been proposed to predict the appearance of notable edge waves with similar frequency to the harbor eigen frequencies, which is a necessary condition for severe oscillation in the harbor.

Influence of pressure on the formation process of CH4 hydrate in porous media below the freezing point

AbstractNatural gas hydrates are mainly stored in the pores of the sedimentary layer in permafrost regions, and the formation characters in porous media were particularly important for the exploitation and utilization of natural gas hydrates. So, it is essential to understand the formation process of methane hydrate in porous media below freezing point. In this study, the formation process of methane hydrate was studied in a closed system in porous media below freezing point. The results indicated that the initial pressure played an important role in the formation characteristics of methane hydrate in porous media below freezing point. The higher the initial pressure was, the larger the formation rate of methane hydrate. And the maximum formation rate attained 6.46 × 10−4 mol/h when the initial pressure was 9.0 MPa under the same temperature and particle size conditions. Furthermore, the final conversion rate was larger at higher initial pressure and the final conversion rate attained 56.5% at an initial pressure of 9.0 MPa. Furthermore, the pressure disturbance could improve the formation process of methane hydrate and the final conversion rate was larger to some extent. The relevant results will provide a theoretical reference for natural gas hydrates exploitation.

Effect of air mass fraction on transient pressure and structural integrity assessment in a relatively long cast iron pipe

A numerical model was developed to study transient flow in air–liquid mixtures in quasi-rigid pipes. Hydraulic transient was generated in a relatively long cast iron pipe by the fast closure of the downstream valve. The presented model is based on the homogeneous flow model approach which considers the two-phase flow as a mixture without the assumption of a non-interface exchange. The method of characteristics was used to solve the set of partial differential equations. To validate the numerical model, experimental data from literature were used. The pressure wave propagation was analyzed through the pipe to understand the behavior of the air–liquid mixture under pressure disturbances. The value of the air mass fraction was also varied to discuss its effect on transient pressure. Obtained results revealed that the increase of the air mass fraction in the operating liquid may contribute to decreasing the maximum transient pressure. Based on the thin-walled hollow cylinder assumptions, the maximum stresses in the pipes were calculated for different values of the air mass fraction. Obtained results were used to conduct a structural integrity analysis of the cast iron pipe with a semi-elliptical crack. A Failure Assessment Diagram (FAD) was obtained based on the SINTAP method to calculate the safety factor for different values of the air mass fraction. It has been observed that the safety factor varies with the presence of the gaseous phase in the operating fluid.

Study on Stress Characteristics of Multi-arch Tunnel Lining under Weak Surrounding Rock Conditions Based on Field Measurement

Considering the complexity of stresses on multi-arch tunnel structures under conditions of shallow depth, unsymmetrical pressure and weak surrounding rocks and the actual geological exploration of the Xiaojian Mountain Multi-arch Tunnel, the cross-sections in strongly-weathered section were selected for embedment of monitoring and measurement equipment to monitor in real time the stress of support structures during tunnel construction. In addition, the finite difference software FLAC3D was adopted to study the surrounding rock deformation during the excavation of the multi-arch tunnel. As a result, the stress state and deformation characteristics of the support structures under unsymmetrical pressure and construction disturbance were obtained. Based on the analysis of monitoring data, it can be concluded that under conditions of shallow depth and unsymmetrical pressure, reduction of stress imbalance on the support structures is of utmost importance to the structural stability of a multi-arch tunnel and that the method of cross-validation between monitoring & measurement and numerical simulation enables more accurate analysis of stability of tunnel structure and better guidance for construction.

Large-Eddy Simulation of Flame Dynamics During the Ignition of a Swirling Injector Unit and Comparison With Experiments

Abstract During the ignition of a swirled single-injector combustor, two phases have been identified experimentally. In the first, the flame penetrates the injection unit, while in the second, the flame lifts off after a substantial delay before stabilizing at a distance from the injector. This transient phenomenon is investigated using Large Eddy Simulations based on an Euler–Lagrange description of the liquid spray, an energy deposition model to mimic ignition, and the thickened flame combustion model. It is shown that the initial penetration of the flame in the injector unit is linked with the positive pressure excursion induced by the rapid volumetric expansion of burnt gases. This sudden expansion is itself due to the fast increase in heat release rate that occurs during the initiation of the process. The corresponding positive and negative pressure disturbances induce a rapid reduction of the mass flow rate through the injector, followed by an acceleration of the flow and a return to the nominal value. It is also shown that the flame root disappears after another delay, which results in the flame edge lifting and stabilization at a distance from the injector exhaust corresponding to steady operation of the device. The relatively long delay time before this liftoff takes place is found to correspond to the residence time of the cooled burnt gases in the vicinity of the chamber walls, which are ultimately entrained by the internal recirculation zone and quench the lower flame foot.

The effect of pressure fluctuations on the shapes of thinning liquid curtains

Abstract

Wedge-induced oblique detonation waves in supersonic kerosene-air premixing flows with oscillating pressure

The oblique detonation wave (ODW) induced by a wedge in the supersonic pre-evaporated kerosene-air flow is investigated via the numerical simulation based on the Navier-Stokes equations with a two-step reaction model. The unsteady inflow feature is subject to a continuous sinusoid pressure disturbance. The influence of oscillating amplitudes and disturbance cycle numbers of the unsteady pressure on the stabilization of wedge-induced ODW is analyzed. Based on a smooth transition with a curved shock from the shock-induced deflagration to oblique detonation, the increasing fluctuating amplitude results in the unsteady dynamics for the ODW stabilization. It is found that both the formation wave structure and the transition pressure are changed due to the unsteady inflow, and a double-V wave structure appears. The interaction between the pressure disturbance and the stabilization wave structure leads to the oscillating ODW with convex and concave fronts. In particular, the low-pressure wave induces a larger wave angle with convex ODW and the concave one with unstable cellular wave structures is due to the high-pressure disturbance. The decrease of the disturbance cycle number results in a gradual evolution process of ODW stabilization, and the increase leads to the complex interactions of transverse waves, during which local quenching could occur. In general, the present results indicate that the stabilization wave structure of ODW is expected to re-adjust itself with local unstable features during a dynamic process and tends to be resilient to the inflow pressure disturbances.

Spatiotemporal variation of wave energy induced by an accelerated moving atmospheric pressure disturbance

ABSTRACT In this paper, energy distribution and variation induced by a one-dimensional atmospheric pressure disturbance (APD) moving with a constant acceleration are theoretically studied. Based on the analytical solution, significant energy fluctuations are confirmed along the moving tracks of three surface waves. Upon which, energy distribution around the instantaneous APD center is further investigated. Around the APD center the potential energy dominates the total energy. The energy of the accelerated case is smaller than that of the corresponding idealized case. The ratio between them reaches its maximum near the APD center and declines both sides showing a spatially asymmetric pattern. Regarding the total accumulated energy, both potential and kinetic energies approach their idealized situations gradually. Meanwhile, the energy variation rate is quantitatively analyzed from perspectives of energy input and output. Energy growth/reduction occur at the front/rear side of the APD center. Nevertheless, the energy growth in front of the APD is more significant, ascribing to the more energy input from the front. In addition, it’s also confirmed that under the accelerated moving APD, the total energy growth is composed of both the energy inputting from the APD and the energy transferred from outside into the region.

Drivers of species richness, biomass, and dominance of invasive macrophytes in temperate lakes

Presence and abundance of invasive species depend on likelihood of introduction and environmental limitations to their distributions. Propagule pressure and anthropogenic disturbance are hypothesized to increase invasions, yet assessing the importance of propagule pressure and anthropogenic factors independently is challenging, and properties of invaded systems (e.g., habitat availability) likely contribute to invasions. We sampled macrophyte assemblages in 20 lakes in New York, varying in boater visitations and number of previous waterbodies visited, to test if increased propagule risk (proxy for propagule pressure measuring potential for introducing invasives from different sources) resulted in greater species richness, biomass (g/m2) and dominance (% invasive biomass) of invasive macrophytes. We then tested watershed land use, in-lake water properties, and lake morphology on presence, abundance, and dominance of invasive macrophytes. Increased propagule risk resulted in greater species richness of invasive macrophytes. In invaded lakes, increased abundance of invasive macrophytes was correlated with increased agriculture in watersheds and littoral:total area. Increased dominance of invasive macrophytes was observed in lakes with greater littoral:total areas. Results suggest propagule risk can explain spatial variability in macrophyte invasions, while area-specific biomass in invaded lakes can be correlated with watershed and in-lake water properties. In lakes with increased suitable habitat (relative proportion of littoral:total area ratio), invasive macrophytes may dominate aquatic plant assemblages. Many factors correlated with the abundance of invasive macrophytes are not easily managed (e.g., watershed agricultural land use and lake morphology). Limiting introductions of propagules is likely the best approach to prevent macrophyte invasions, especially at high risk lakes.

Meteotsunamis Accompanying Tropical Cyclone Rainbands During Hurricane Harvey

AbstractMeteotsunami waves can be triggered by atmospheric disturbances accompanying tropical cyclone rainbands (TCRs) before, during, and long after a tropical cyclone (TC) makes landfall. Due to a paucity of high‐resolution field data along open coasts during TCs, relatively little is known about the atmospheric forcing that generate and resonantly amplify these ocean waves, nor their coastal impact. This study links high‐resolution field measurements of sea level and air pressure from Hurricane Harvey (2017) with a numerical model to assess the potential for meteotsunami generation by sudden changes in air pressure accompanying TCRs. Previous studies, through the use of idealized models, have suggested that wind is the dominant forcing mechanism for TCR‐induced meteotsunami with negligible contributions from air pressure. Our model simulations show that large air pressure perturbations (∼1–3 mbar) can generate meteotsunamis that are similar in period (∼20 min) and amplitude (∼0.2 m) to surf zone observations. The measured air pressure disturbances were often short in wavelength, which necessitates a numerical model with high temporal and spatial resolution to simulate meteotsunami triggered by this mechanism. Sensitivity analysis indicates that air pressure forcing can produce meteotsunami with amplitudes O(0.5 m) and large spatial extents, but model results are sensitive to atmospheric factors, including model uncertainties (length, forward translation speed, and trajectory of the air pressure disturbance), as well as oceanographic factors (storm surge). The present study provides observational and numerical evidence that suggest that air pressure perturbations likely play a larger role in meteotsunami generation by TCRs than previously identified.

Experimental Study on Groutability of Sand Layer concerning Permeation Grouting

Permeation grouting is widely used in grouting engineering because of its low grouting pressure and minor disturbance to the stratum. However, influenced by the complex properties of sand layer and slurry, an accurate prediction of the groutability of the sand layer remains to be a hard work. In this paper, the permeability of sand layer is studied based on a self‐designed permeation grouting test device, which considers the different sand particle size, relative density of sand layer, slurry water‐cement ratio, and clay content. The influencing factors of sand layer groutability are analyzed, and the different parameters that affect the grouting of sand layer are evaluated, thus proposing a new approach to predict the groutability of sand layer. Results show that the sand particle size and slurry water‐cement ratio are positively related to the groutability of sand layer, and the relative density and clay content of sand layer are negatively correlated with the groutability of sand layer. The proposed alternative empirical formula to estimate the groutability of sand layer will help predict the groutability of sand layer with a higher degree of accuracy, which can provide a certain reference for engineering.

Experimental Research on Coal and Gas Delay Outburst and AE Characteristics under Conditions of Geostress and Gas Pressure Disturbance

Adopting yellow mud as barrier layer materials, coal and gas delay outburst experiments under conditions of geostress and gas accumulation disturbance were carried out by using self‐developed simulation system, to find out roles of geostress and gas pressure played in the process of the delay outburst and ways to predict it, through analysis of variations of gas pressure, and AE characteristics during the process. The results show that after the geostress increased by 0.11 MPa from 1.80 MPa, an outburst occurs, while in gas accumulation situations, the gas pressure increase of 0.27 MPa from 0.67 MPa induces an outburst; hence, geostress is one of the dominant factors impacting an outburst occurrence. The lasting time of the outburst triggering under geostress disturbance is shorter than that under gas accumulation disturbance, while the duration of the outburst development under gas accumulation conditions is longer than that under geostress conditions. Coal seam breakage by geostress is the precondition for an outburst risk, and gas expansion energy is the dominant parameter influencing the duration of the outburst development. The AE signals show distinctive features in different stages of the outburst under geostress disturbance. At the preparation stage of the outburst, the AE signals increase sharply but have a low intensity and then drop to a lower balance level. At the triggering stage, the AE signals become active and increasing until up to the peak where the outburst occurs, and the intensity is highest.

METEOTSUNAMI RISK AND THE USE OF DYNAMIC MOORING ANALYSIS AND SHORETENSION TO MITIGATE RISK IN FREMANTLE PORT

Meteotsunamis are generated by meteorological events, particularly moving pressure disturbances due to squalls, thunderstorms, frontal passages and atmospheric gravity waves. Relatively small initial sea-level perturbations, of the order of a few centimetres, can increase significantly through multi-resonant phenomena to create tsunami like destructive events resulting in injury, loss of life, damage to infrastructure and significant economic loss. On the 17th August 2014, severe metocean conditions (including 27.8 m/s wind gusts and a meteotsunami) resulted in the vessels Grand Pioneer and AAL Fremantle breaking loose from their mooring at Berth 11 and 12 in Fremantle Port. One of the vessels collided with a railway bridge closing the commuter railway line for two weeks. Royal HaskoningDHV was commissioned by Fremantle Ports to undertake a hydrodynamic investigation and a dynamic mooring analysis (DMA) to determine the cause of the event and provide a technical solution to provide safe moorings in the port.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/idTLjfeajiM

Ecological Assessment for Spatial Planning: The Case of Southern Tuscany, Italy

ABSTRACT The study concerns a methodology of assessment that aims to detect the prior objectives relative to nature conservation in an extended area.of Tuscany in Italy. In particular, we designed a model to assess ecological value (EV) and ecological sensitivity (ES) that together define the hotspots of ecological attention (HEA) areas; we design a model to assess anthropic pressure (disturbance) (AP), which together with ecological sensitivity define the hotspots of ecological fragility (vulnerability) (HEF) areas. The results of the work confirm the robust-ness of the method and its application in the scope of extended area planning and environmental assessment.

Relationship between Plantar Pressure and Sensory Disturbance in Patients with Hansen's Disease-Preliminary Research and Review of the Literature.

Orthoses and insoles are among the primary treatments and prevention methods of refractory plantar ulcers in patients with Hansen’s disease. While dynamic plantar pressure and tactile sensory disturbance are the critical pathological factors, few studies have investigated whether a relationship exists between these two factors. In this study, dynamic pressure measured using F-scan system and tactile sensory threshold evaluated with monofilament testing were determined for 12 areas of 20 feet in patients with chronic Hansen’s disease. The correlation between these two factors was calculated for each foot, for each clinical category of the foot (0–IV) and across all feet. A significant correlation was found between dynamic pressure and tactile sensation in Category II feet (n = 8, p = 0.016, r2 = 0.246, Spearman’s rank test). In contrast, no significant correlation was detected for the entire foot or within the subgroups for the remainder of the clinical categories. However, the clinical manifestation of lesion areas showed high variability: (1) pressure concentrated, sensation lost; (2) margin of pressure concentration, sensation lost; (3) pressure concentrated, sensation severely disturbed but not lost; and (4) tip of the toe. These results may indicate that, even though there was a weak relationship between dynamic pressure and tactile sensation, it is important to assess both, in addition to the basics of orthotic treatment in patients with Hansen’s disease presenting with refractory plantar ulceration.

Investigation on the Flow Field Entropy Structure of Non-Synchronous Blade Vibration in an Axial Turbocompressor.

In order to explore the inducing factors and mechanism of the non-synchronous vibration, the flow field structure and its formation mechanism in the non-synchronous vibration state of a high speed turbocompressor are discussed in this paper, based on the fluid–structure interaction method. The predicted frequencies fBV (4.4EO), fAR (9.6EO) in the field have a good correspondence with the experimental data, which verify the reliability and accuracy of the numerical method. The results indicate that, under a deviation in the adjustment of inlet guide vane (IGV), the disturbances of pressure in the tip diffuse upstream and downstream, and maintain the corresponding relationship with the non-synchronous vibration frequency of the blade. An instability flow that developed at the tip region of 90% span emerged due to interactions among the incoming main flow, the axial separation backflow, and the tip leakage vortices. The separation vortices in the blade passage mixed up with the tip leakage flow reverse at the trailing edge of blade tip, presenting a spiral vortex structure which flows upstream to the leading edge of the adjacent blade. The disturbances of the spiral vortexes emerge to rotate at 54.5% of the rotor speed in the same rotating direction as a modal oscillation. The blade vibration in the turbocompressor is found to be related to the unsteadiness of the tip flow. The large pressure oscillation caused by the movement of the spiral vortex is regarded as the one of the main drivers for the non-synchronous vibration for the present turbocompressor, besides the deviation in the adjustment of IGV.