Sudden Pressure Changes Research Articles

WHIPPIT - WHIPPED THE LUNG

SESSION TITLE: Medical Student/Resident Disorders of the Pleura Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Pneumothorax (PTX) can be a complication of invasive mechanical ventilation due to abrupt changes in pressure within the thoracic cavity. It can also occur due to sudden change in the intra-thoracic pressure as a complication of inhaled illicit substances such as cocaine and 3,4-Methylenedioxymethamphetamine (MDMA) (1,2). The recreational use of inhaled nitric oxide continues to rise, with prolonged inhalation leading to neurological complications (3). Here, we present a case of a PTX after inhalation of pressurized nitric oxide in a patient without any prior lung disease, a complication not previously reported. CASE PRESENTATION: A 25-year-old man with history of cannabis use disorder presented with sudden onset left sided chest pain and dyspnea that started after inhaling two canisters of Whippits (pressurized whipped cream chargers filled with nitric oxide). He was tachycardic and tachypneic upon presentation and was noted to have absent breath sounds over left hemi-thorax. Initial laboratory investigations including a complete blood count and comprehensive metabolic panel were unremarkable. Chest X-ray (CXR) revealed a large left PTX with complete collapse of the left lung. A chest tube was inserted on the left hemithorax with resolution of his symptoms and the PTX on imaging. A computed tomography of the chest showed no underlying lung disease. The patient was discharged with recommendations to abstain from inhaled nitric oxide use. DISCUSSION: PTX due to nitric oxide inhalation is uncommon, and to our knowledge no cases have been previously reported. However, PTX and pneumomediastinum from Valsalva maneuvers after use of inhaled drugs have been reported and have been associated with marijuana use (4,5,6). Although, there is no direct role of marijuana in the development of emphysema, high burden of inflammatory cells leading to lung injury and subsequent emphysema has been described (5). In our patient, who had no prior underlying lung disease, the development of PTX most likely resulted from sudden and rapid change in intra-alveolar pressure secondary to forced lung expansion from a Valsalva maneuver after inhalation of pressurized nitric oxide. CONCLUSIONS: Nitric oxide induced PTX has not been previously reported in the literature. In our patient, PTX in the absence of underlying primary lung disease can be explained by barotrauma from rapid inhalation of nitric oxide via Whippits. Further studies are warranted to evaluate the risk factors and incidence of PTX with pressurized nitric oxide inhalation. Reference #1: Ioannidis G, Lazaridis G, Baka S, et al. Barotrauma and pneumothorax. J Thorac Dis. 2015;7(Suppl 1):S38–S43. doi:10.3978/j.issn.2072-1439.2015.01.31 Reference #2: 2) Jaensch S, Hwang S, Shih-Wei-Kuo T. Spontaneous Pneumomediastinum and Subcutaneous Emphysema following Cocaine Inhalation and Ecstasy Ingestion. Case Reports in Otolaryngology. 2019; doi: 10.1155/2019/6972731 Reference #3: 3) Thompson AG, Leite MI, Lunn MP, Bennett DL. Whippits, nitrous oxide and the dangers of legal highs. Pract Neurol. 2015;15(3):207–209. doi:10.1136/practneurol-2014-001071 4) Hauben M, Hung EY. Pneumothorax as an adverse drug event: an exploratory aggregate analysis of the US FDA AERS database including a confounding by indication analysis inspired by Cornfield's condition. Int J Med Sci. 2013;10(8):965–973. Published 2013 Jun 13. doi:10.7150/ijms.5377 5) Mishra R, Patel R, Khaja M. Cannabis-induced bullous lung disease leading to pneumothorax: Case report and literature review. Medicine (Baltimore). 2017;96(19):e6917. doi:10.1097/MD.0000000000006917 6) Miller, W. Eugene, et al. “Pneumomediastinum Resulting from Performing Valsalva Maneuvers during Marihuana Smoking.” Chest, vol. 62, no. 2, 1972, pp. 233–234., doi:10.1378/chest.62.2.233. DISCLOSURES: No relevant relationships by Moeezullah Beg, source=Web Response No relevant relationships by Tasnim Islam, source=Web Response Consultant relationship with GSK Please note: $5001 - $20000 Added 04/23/2020 by Diego Maselli Caceres, source=Web Response, value=Consulting fee Consultant relationship with AstraZeneca Please note: $5001 - $20000 Added 04/23/2020 by Diego Maselli Caceres, source=Web Response, value=Consulting fee Consultant relationship with Sanofi/Regeneron Please note: $5001 - $20000 Added 04/23/2020 by Diego Maselli Caceres, source=Web Response, value=Consulting fee Speaker/Speaker's Bureau relationship with Sunovion Please note: $5001 - $20000 Added 04/23/2020 by Diego Maselli Caceres, source=Web Response, value=Honoraria Consultant relationship with Novartis Please note: $1001 - $5000 Added 04/23/2020 by Diego Maselli Caceres, source=Web Response, value=Consulting fee

A compact QCL spectrometer for mobile, high-precision methane sensing aboard drones

Abstract. A compact and lightweight mid-infrared laser absorption spectrometer has been developed as a mobile sensing platform for high-precision atmospheric methane measurements aboard small unmanned aerial vehicles (UAVs). The instrument leverages two recent innovations: a novel segmented circular multipass cell (SC-MPC) design and a power-efficient, low-noise, intermittent continuous-wave (icw) laser driving approach. A system-on-chip hardware control and data acquisition system enables energy-efficient and fully autonomous operation. The integrated spectrometer weighs 2.1 kg (including battery) and consumes 18 W of electrical power, making it ideally suited for airborne monitoring applications. Under stable laboratory conditions, the device achieves a precision (1σ) of 1.1 ppb within 1 s and 0.1 ppb CH4 at 100 s averaging time. Detailed investigations were performed to identify and quantify the effects of various environmental factors, such as sudden changes in pressure, temperature, and mechanical vibrations, which commonly influence UAV-mounted sensors. The instrument was also deployed in two feasibility field studies: an artificial methane release experiment and a study on vertical profiles in the planetary boundary layer. In both cases, the spectrometer demonstrated its airborne capability of capturing subtle and/or sudden changes in atmospheric CH4 mole fractions and providing real-time data at 1 s time resolution.

The Solar Wind Density Control on the Prompt Penetration Electric Field and Equatorial Electrojet

AbstractPrompt penetration of convection/overshielding electric fields to equatorial and low latitudes during the southward/northward turnings of interplanetary magnetic field (IMF Bz) have been widely studied in the literature. The other types of penetration electric fields due to sudden changes in the solar wind dynamic pressure, IMF By and during the onset of substorms have also been recently reported. In this paper, we present the exclusive role of solar wind density changes on the prompt equatorial electric field disturbances using the long‐term observations of equatorial electrojet (EEJ) from the Indian sector. In response to the sharp increases in the solar wind density, prompt increases/decreases in the EEJ indicating the eastward/westward prompt penetration electric field (PPEF) of ~20 min periods have been consistently observed on the dayside/nightside. The prompt equatorial electric field disturbances of the opposite polarity have also been observed when the density decreases sharply. Further, the polarity of these PPEF disturbances does not show any clear dependency on the direction of IMF Bz and By. This paper is the first report with a statistically significant number of observations on the characteristics of equatorial electric field disturbances in response to the sudden enhancements/decreases in the solar wind density alone on both dayside and nightside. The underlying physical mechanisms for the prompt equatorial electric field disturbances have been discussed in light of enhanced high‐latitude convection and additional field‐aligned currents due to sudden enhancement of solar wind density.

Systematical Analyses of Global Ionospheric Disturbance Current Systems Caused by Multiple Processes: Penetration Electric Fields, Solar Wind Pressure Impulses, Magnetospheric Substorms, and ULF Waves.

We present the first systematic analysis of global ionospheric disturbance current systems caused by multiple processes of solar and magnetospheric origin, including reorientations of the interplanetary magnetic field (IMF), sudden changes in the solar wind dynamic pressure, magnetospheric sawtooth substorms, and ultralow frequency (ULF) waves. Measurements from global magnetometer networks are used to derive the equivalent disturbance currents from the polar cap to the equator. A surprising result is that the equivalent disturbance current systems are very similar, although the driving processes are completely different. The equivalent disturbance current system in response to IMF reorientation or substorm onset is characterized by a large vortex on the dayside and evening sector and a smaller vortex near dawn, and the polarity of the current vortices depends on the IMF direction. The equivalent disturbance current system caused by a sudden change in the solar wind pressure or by ULF waves consists of a single vortex at middle and low latitudes and a very small vortex above ~60° magnetic latitude near dawn. The similar disturbance current systems caused by different solar wind and magnetospheric processes suggest that the global distribution of the ionospheric currents is determined by the intrinsic property of the ionosphere. The global current system takes only ~1 min to completely reconstruct, indicating that the current system can reach a new steady state within 1 min. A scenario is proposed to explain the global distribution and fast reconstruction of the current systems.

Can the time-lag method be used for the characterization of liquid permeation membranes?

Although the time-lag method is one of the most common tools for the characterization of gas permeation membranes, it is entirely unknown in the vast area of liquid permeation membranes. The time-lag method requires a dynamic permeation test initiated by a step-change in the driving force for the species permeation, which is relatively easy for gas permeation, but not for liquid permeation. In this paper, we present preliminary trials to overcome this obstacle for liquid permeation membranes by performing a sudden change in the osmotic pressure by changing the draw solution concentration. To accomplish this, we have modified a standard forward osmosis testing system to monitor the changes in the mass of feed and draw solutions, and the conductivity of feed solution in real-time. To demonstrate the system's operation, we tested commercial, low-pressure reverse osmosis thin film composite membranes in the active-layer-facing-draw-solution orientation. We present and discuss the resulting time-dependent changes in the water flux and the reverse salt flux, and the processing of the experimental data. The shapes of time-dependent water and salt masses are similar to the pressure decay curves and pressure rise curves, respectively, in a time-lag gas permeation experiment.

Transient Phenomena Generated in Emptying Operations in Large-Scale Hydraulic Pipelines

Air pockets generated during emptying operations in pressurized hydraulic systems cause significant pressure drops inside pipes. To avoid these sudden pressure changes, one of the most widely used methods involves the installation of air valves along the pipeline route. These elements allow air exchange between the exterior and the interior of the pipe, which alleviates the pressure drops produced and thus prevents possible breaks or failures in the structure of the installation. This study uses a mathematical model previously validated by the authors in smaller installations to simulate all hydraulic variables involved in emptying processes over time. The purpose of these simulations is the validation of the mathematical model in real large-scale installations, and to do this, the results obtained with the mathematical model are compared with actual measurements made by the partner company. The hydraulic system selected for the study is a pipeline with a nominal diameter of 400 mm and a total length of 1020 m. The results obtained from the mathematical model show great similarity with the experimental measurements, thus validating the model for emptying large pipes.

Deformation and stress in hydrothermal regions: The case of a disk-shaped inclusion in a half-space

Hydrothermal regions are affected by a wide variety of phenomena, including ground inflation and deflation episodes. Among them, calderas offer the opportunity to study the complex interactions between magmatic processes at depth and permeable rocks saturated with fluids in the upper sedimentary layers. One of such regions is the Campi Flegrei caldera in southern Italy, where several source models have been applied over the years to reproduce the ground displacement and seismicity observed during the most recent phase of major unrest (1982–1984). The present work aims at introducing a new source model consisting of a thermo-poro-elastic inclusion embedded in a homogeneous poroelastic half-space. The inclusion is meant to represent a permeable rock layer stressed and strained by hot and pressurized volatiles released upward by an underlying magmatic reservoir and is modeled as a thin horizontal disk inside which a sudden change of temperature and pore pressure occurs. We provide semi-analytical solutions for the displacement and stress fields both within and outside the source and check them by comparison with those obtained through a fully numerical approach. Results provided by our model are compared with two other deformation source models often used to describe volcanic environments in terms of pressurized cavities describing a spherical magma chamber (Mogi source) or a sill-like magma intrusion (Fialko source). For the Campi Flegrei 1982–84 unrest, our model provides a better reproduction of ground deformation data and manages to explain the widespread presence of compressive focal mechanisms, since the stress field promoted both inside and outside the thermo-poro-elastic inclusion is very different from pressurized cavities.

Intensified impacts on mortality due to compound winter extremes in the Czech Republic

Although impacts of extremely cold temperatures on human health have been widely studied, adverse effects of other extreme weather phenomena have so far received much less attention. We employed a high-quality long-term mortality time series (1982–2017) to evaluate impacts of extreme winter weather in the Czech Republic. We aimed to clarify whether compound events of extreme weather cause larger impacts on mortality than do each type of extreme if evaluated individually. Using daily data from the E-OBS and ERA5 datasets, we analyzed 9 types of extreme events: extreme wind gust, precipitation, snowfall, and sudden temperature and pressure changes. Relative mortality deviations from the adjusted baseline were used to estimate the immediate effect of the selected extreme events on excess mortality. The impact was adjusted for the effect of extreme cold.Extreme events associated with sudden rise of minimum temperature and pressure drops had generally significant impact on excess mortality (3.7% and 1.4% increase). The impacts were even more pronounced if these events occurred simultaneously or were compounded with other types of extremes, such as heavy precipitation, snowfall, maximum temperature rise, and their combinations (increase as great as 14.4%). Effects of some compound events were significant even for combinations of extremes having no significant impact on mortality when evaluated separately. On the other hand, a “protective” effect of pressure increases reduced the risk for its compound events. Meteorological patterns during extreme events linked to excess mortality indicate passage of a low-pressure system northerly from the study domain. We identified extreme winter weather events other than cold temperatures with significant impact on excess mortality. Our results suggest that occurrence of compound extreme events strengthen the impacts on mortality and therefore analysis of multiple meteorological parameters is a useful approach in defining adverse weather conditions.

Analysis of hydraulic transients during pipeline filling processes with air valves in large-scale installations

ABSTRACT During the filling process in pressurized hydraulic systems, sudden pressure changes generated inside the pipes can cause significant damage. To avoid these excessive overpressures, air valves should be installed to allow air exchange between the inside and outside during the filling process. This study presents a mathematical model to analyse the hydraulic transients during filling processes. This model, which has already been validated in small laboratories, is now applied to real large-scale systems that consist of DN400 and DN600 pipelines from Empresa Mixta Metropolitana S.A (EMIMET – Group Global Omnium), which is the company that manages the water supply of the metropolitan area of Valencia (from the Drinking Water Treatment Station to the municipalities). The mathematical model for large pipes is validated by comparing the experimental measurements and the results of model.

ОСОБЛИВОСТІ ПРОЕКТУВАННЯ НОСКА ПОВІТРОЗАБІРНИКА ТУРБОВЕНТИЛЯТОРНОГО ДВИГУНА

Optimization of turbofan engine air intake as well as geometry of intake lip, in-let cross-sectional area and its length is a relevant task in optimizing aerodynamic configuration of an aircraft. It is necessary to ensure a smooth entry of air flow into the engine at all modes of its operation and at various aircraft evolutions while minimizing impact on the overall aerodynamic efficiency of the aircraft. Development of engine air intake was once a very long, routine process that could last for months be-fore design completion, followed by expensive tests on determination of air intake performances on the engine test bench and in flight. Today, we can evaluate performances for a large number of air intake options using design software. The use of computational methods does not exclude tests of air intakes but dramatically reduces their quantity, testing costs and allows designers to focus mainly on the best candidates for air intakes avoiding potential surprises such as shock waves or flow separation caused by a shock wave. Optimal design of the air intake includes determining the right balance between the air intake characteristics, structural load and weight. An over-designed air intake will ultimately be overweight and thus more expensive in terms of flight cost. In a well-designed air intake the Mach number should not exceed 1, in order to avoid a sudden change in static pressure, temperature and density, which can lead to potential shock waves and flow separation caused by a shock wave in all areas throughout the flight. The use of computational fluid dynamics al-lows a better understanding of the conditions under which such adverse events occur. Adjacent to this task is the provision of necessary area on the inside of air intake to ensure sufficient noise absorption generated by the engine fan. The article considers evolution of research on the example of air intake of the D-436 engine of the An-148 aircraft.

Modeling and Jitter Suppression Analysis of a Lifting Multistage Hydraulic Cylinder

In view of the abnormal phenomena in the movement of the 4-stage hydraulic cylinder, this paper establishes the basic motion model of the multi-stage hydraulic cylinder by melting point nodal cavity method, and analyses the variation law of its external load. On this basis, the erection process of the multi-stage hydraulic cylinder is simulated and analyzed by AMESim, and it is found that the sudden change of pressure at the change of the stage will cause the vibration of the multi-stage. Found that the abnormal vibration of the third piston occurs during the retraction process of the hydraulic cylinder, which is caused by the insufficient guide distance of the 3 stage piston of the multi-stage hydraulic cylinder. The sealing conditions of the piston and the guide sleeve are improved by increasing the guide length of the piston appropriately, and the correctness of the improved scheme is verified by the way of simulation, that is, it can effectively suppress the vibration of the third piston. Vibration occurs during retraction. Some improvement suggestions are provided for vibration reduction of multi-stage hydraulic cylinder.

Shock wave propagation along the central retinal blood vessels.

Retinal haemorrhage is often observed following brain injury. The retinal circulation is supplied (drained) by the central retinal artery (vein) which enters (leaves) the eye through the optic nerve at the optic disc; these vessels penetrate the nerve immediately after passing through a region of cerebrospinal fluid (CSF). We consider a theoretical model for the blood flow in the central retinal vessels, treating each as multi-region collapsible tubes, where we examine how a sudden change in CSF pressure (mimicking an injury) drives a large amplitude pressure perturbation towards the eye. In some cases, this wave can steepen to form a shock. We show that the region immediately proximal to the eye (within the optic nerve where the vessels are strongly confined by the nerve fibres) can significantly reduce the amplitude of the pressure wave transmitted into the eye. When the length of this region is consistent with clinical measurements, the CSF pressure perturbation generates a wave of significantly lower amplitude than the input, protecting the eye from damage. We construct an analytical framework to explain this observation, showing that repeated rapid propagation and reflection of waves along the confined section of the vessel distributes the perturbation over a longer lengthscale.

Hazard evaluation of explosion venting behaviors for aluminum powder/air fuels using experimental and numerical approach

In this paper, modified 20 L sphere was used for the determination of the explosion venting of aluminum powder/air fuels, Fluent software was used for simulation to reveal the combustion mechanism. The results showed that the airtight accumulation effect gradually strengthened with the increase of the cracking pressure. Meanwhile, the maximum reduced explosion pressure and the flame length increased gradually accompanied by the flame changed from secondary/multiple flame type to single flame type. Additionally, the pressure field was reproduced by simulation. It demonstrated that the under-expansion jet was formed due to sudden change of pressure, density, temperature and Mach number between internal and outer of the vessel, which caused the turbulent kinetic energy at the vent to be much higher than that inside the vessel. The results at the conditions with vents of 70 mm and 50 mm in diameter had better accuracy and safety margin according to theoretical calculation.

Research Progress on Anti-Vascular Endothelial Growth Factor-Induced Retinal Pigment Epithelium Tear

Various eye diseases can cause retinal pigment epithelium (RPE) tear. RPE tear is common in neovascular age-related macular degeneration (nAMD). The injection of anti-vascular endothelial growth factor (VEGF) increases the risk of PRE tear, the mechanism of which is a sudden change in intraocular pressure during drug injection, vitreous macular traction, destruction of the RPE tight junction barrier and secondary contraction and fibrosis of the choroidal neovascular membrane. The height of pigment epithelial detachment (PED) is an important risk factor for RPE tear in patients with nAMD after injection of anti-VEGF drugs. The diagnosis of RPE tears primarily relies on imaging studies，such as fundus photography、fundus autofluorescence、optical coherence tomography and so on. Regarding treatment, we must first determine whether the patient has a RPE tear, or whether there are risk factors related to the RPE tear, and then perform the corresponding personalized treatment. If possible, consider stem cell transplant alternatives. There is no proven method to prevent RPE tear so far. This article will review and summarize the research progress in the pathogenesis, risk factors, diagnosis, treatment and prevention of RPE tear caused by anti-VEGF drugs, and further improve the understanding of RPE tears，in order to provide reference for clinical work.

Effect of Landslide Surge on Pile Foundation of Overhead Vertical Wharf

Waves generated by landslides into water cause great harm to wharfs. Hence, the surge wave pressure generated by the landslide serves as an important reference for the structural design of wharfs in reservoir areas. In this study, a series of hydraulic model tests were performed to study the energy and wave pressure produced by the surge. According to wave pressure‐time curves, the extreme values of sudden transient changes in wave pressure are obtained. The mechanism and influencing factors of surge wave pressure on vertical wharf buildings are expounded. On this basis, a formula to calculate the wave pressure exerted by landslide surge on the pile foundation of an overhead vertical wharf is developed. A large number of experiments show that the empirical formula is in good agreement with the experimental data.

An Intelligent Bio-Inspired Cooperative Decoupling Control Strategy for the Marine Boiler-Turbine System with a Novel Energy Dynamic Model

This paper presents an intelligent bio-inspired cooperative decoupling control strategy (IBICDC) for the problems of modeling difficulties and strong coupling in the marine boiler-turbine system (MBTS). First, the model of the main steam pressure control loop is successfully constructed by introducing the Martin-Hou equation, which solves the modeling difficulty caused by the complexity of structure, operation mechanism, and operation conditions, as well as the characteristics of nonlinearity, parameter time-varying, and time-delay in the marine boiler (MB). According to the mathematic method of homeomorphic mapping relationship between the rotational speed and the kinetic energy in the marine steam turbine with propeller (MSTP) and the feedback linearization method, the nonlinear degree of the MSTP rotational speed control loop model is reduced and the infinite point of discontinuity in the rotational acceleration when the rotational speed close to 0 is eliminated. Then, the IBICDC inspired by the internal environment regulation mechanism of human body is applied to the strong coupling problem between the two control loops, namely, to eliminate the large value sudden change of the main steam pressure caused by the change of operation conditions. The conventional decoupling methods are also presented. Finally, detailed numerical simulations are conducted to validate the effectiveness of the IBICDC strategy.

The upper frequency limit of dynamic cerebral autoregulation.

Dynamic cerebral autoregulation (CA) is expressed by the temporal pattern of cerebral blood flow (CBF) recovery following a sudden change in arterial blood pressure (BP). Transfer function analysis of BP as input and CBF velocity as output can express dynamic CA through its amplitude (or gain) and phase frequency responses. The upper frequency limit (FupLim ) at which dynamic CA can operate is of considerable physiological interest and can also provide additional information about worsening CA due to disease processes. In healthy subjects FupLim was strongly dependent on arterial changes induced by four different breathing manoeuvres. The considerable intersubject variability in FupLim suggests that fixed frequency bands should not be adopted for averaging values of gain and phase in studies of dynamic CA. Dynamic cerebral autoregulation (CA) can be expressed in the frequency domain by the amplitude and phase frequency responses calculated by transfer function analysis of arterial blood pressure (BP) and cerebral blood flow velocity (CBFV). We studied the effects of arterial ( ) on the upper frequency limit (FupLim ) of these responses and its intersubject variability. Twenty-four healthy subjects (11 female, age 36.0±13.4years) were recruited. Recordings of CBFV (transcranial Doppler ultrasound), BP (Finometer) and end-tidal CO2 ( , capnography) were performed during 5min at rest (normocapnia) and during four breathing manoeuvres: 5% and 8% CO2 in air and hyperventilation targeting reductions of 5 and 10mmHg compared to normocapnia. FupLim was determined by the break point of the autoregulation index (ARI) curve as a function of frequency when the phase response was gradually set to zero. The five breathing conditions led to highly significant differences in (p<0.0001), CBFV (P<0.0001), ARI (p<0.0001) and FupLim (p<0.0001). FupLim ranged from 0.167±0.036Hz at the lowest values of hypocapnia (28.1±1.9mmHg) to 0.094±0.040Hz at the highest level of hypercapnia (41.7±5.4mmHg), showing a correlation of r=-0.53 (p<0.001) with . These findings reinforce the key role of in CBF regulation. The considerable intersubject variability of FupLim suggests that fixed frequency bands should not be adopted for averaging values of gain and phase in dynamic CA studies, and that the higher frequency band (0.20-0.40Hz), in particular, does not contain relevant information about dynamic CA. Further investigations are needed to assess the information value of FupLim as a marker of dynamic CA efficiency in physiological and clinical studies.

A general-purpose colourimetric air pressure indicator

A general-purpose air pressure colourimetric indicator is described based on a sensitive CO2 indicator, which responds to the change in partial pressure of CO2 in air. The indicator uses the pH indicator dye thymol blue (TB) and is green in ambient air (at 1 atm), bright blue under high vacuum (<0.01 atm) and bright yellow at high air pressures (>10 atm). The TB indicator is cast from an ink and its change in colour monitored mainly using digital photography coupled with colour analysis and quantitatively related to air pressure. The response of the TB indicator is initially probed using different Ar/CO2 gas mixtures at 1 atm pressure and then used to monitor: (i) sub-ambient air pressures, P, over the range 0.1−1 atm and (ii) super ambient air pressures over the range 1−14 atm. Colour analysis of all the photographic images taken in the two studies reveals a consistent data set that is readily related quantitatively to P, with a typical 50 % colour change at 1.02 ± 0.03 atm of air, i.e. or (4.2 ± 0.1)×10−4 atm of CO2. The 90 % response and recovery times of the indicator to sudden changes in pressure are fast, <1.7 min. Two possible applications of the TB indicator, in vacuum packaging and as a pressure sensitive paint in aerodynamics are demonstrated. This is the first example of a general-purpose air pressure colorimetric indicator and in particular one that can be used to monitor super-ambient air pressures up to ca. 10 atm.

Non-equilibrium thermodynamic model for liquefied natural gas storage tanks

A thermodynamic non-equilibrium model is introduced to evaluate the thermal performance of vertical and horizontal liquefied natural gas (LNG) storage tanks in refueling stations. This model incorporates a resistance-capacitance network to reduce the required computation time to several hours compared with the computational fluid dynamics (CFD) method which requires several days or weeks to run under high-performance computing. The accuracy of the non-equilibrium model is validated with two sets of experimental data, and thermodynamic equilibrium and CFD models, respectively. Our results indicate that the non-equilibrium and equilibrium models have a similar accuracy to predict the pressure and temperature changes in vertical and horizontal LNG storage tanks under stationary conditions. However, the equilibrium model fails to predict the tank performance under sudden pressure changes such as those produced via vapor return from heavy-duty trucks duringre fueling. In contrast, the non-equilibrium model accurately predicts the pressure of LNG storage tank under dynamic conditions. Our results also indicate that, compared to vertical tanks and under dynamic operating conditions, horizontal storage tanks can hold LNG for longer periods without methane release to the atmosphere.

Liquid jet formation during a suspended liquid suction process

In the tubular co-flowing gas-liquid jet, liquid is sucked through a nozzle suspended above the flat gas-liquid interface. The liquid hump can be induced by the sudden pressure change just beneath the nozzle entrance. At a sufficiently fast initial gas superficial velocity, the interface undergoes a transition and liquid starts to be sucked. The suction flow is in the form of an axisymmetric liquid jet surrounded by an upwards coaxial gas flow. In the present study, we discuss the evolution and characteristics of the suspended liquid suction flow. The jet dynamics include the interface deformation and development (the hump stage), the tubular co-flowing jet (the spout state) and the destabilization of the liquid jet (the jet state). Tube inner diameter, suspension height, and initial gas superficial velocity are three important parameters that influence the suction flow. Due to the inward gas flow, a relatively large amount of pressure gradients is imparted to a small mass of liquid near a free surface, which leads to interface deformation. The lateral boundary of the liquid hump circumferentially shrinks and the top liquid gradually rises following the shrinkage. There is a comparatively stable axisymmetric liquid jet surrounded by an upwards coaxial gas flow inside the tube. Surprisingly, no evidence is shown the dependence of jet spout with initial gas axisymmetric superficial velocity below the nozzle through plenty of experiment figures and statistical analysis. On the other hand, the velocity difference between the fast light gas flow and the slow dense liquid is critical to the destabilization of the liquid jet.