Vent Opening Research Articles

Physics‐Based Forecasts of Eruptive Vent Locations at Calderas

AbstractConstraining stresses in the Earth's crust in volcanic regions is critical for understanding many mechanical processes related to eruptive activity. Dike pathways, in particular, are shaped by the orientation of principal stress axes. Therefore, accurate models of dike trajectories and future vent locations rely on accurate estimates of stresses in the subsurface. This work presents a framework for probabilistic constraint of the stress state of calderas by combining three‐dimensional physics‐based dike pathway models with observed past vent locations using a Monte Carlo approach. The retrieved stress state is then used to produce probability maps of future vent opening across a caldera. We test our stress inversion and vent forecast approach on synthetic scenarios, and find it successful depending on the distribution of the available vents and the complexity of the volcano's structural history. We explore the potential and limitations of the approach, show how its performance is sensitive to the assumptions in the models and available prior information, and discuss how it may be applied to real calderas.

Ashfall characteristics and development of the ash monitoring network during three decades of the long-lived eruption of Popocatépetl Volcano, México

A long-lived eruption of Popocatépetl volcano in central México has produced almost continuous ash fall on the populated areas for 30 years. The eruptive phase that began in 1994, has been characterized since 1996 by the growth of about 90 subsequent crater domes and their destruction that has produced most of the ongoing ash emissions. Since the beginning of the ash emission in 1994, we designed, established, and maintained an ash-sampling network of more than 200 sites around the volcano. This sampling network has been improved over the years and there are currently also 19 automated samplers, that we describe in this manuscript. This ash sampling network is part of the Popocatépetl monitoring system run by Universidad Nacional Autónoma de México (UNAM). The sampling sites that are distributed over an area of ∼8000 km2 where ash fall occurs, involve collection of ash over 0.4 cm2 and 1 m2 areas during ash emission events associated with plumes over 1 km high. Community participation has greatly enhanced both, ash sample collection efficiency and public awareness.Growth and destruction of lava domes are variable over time, with growth times that could last up to weeks and residence times ranging from days to months, producing frequent ash emissions. There have been about 1225 ash emissions >1 km high, of these, 110 have been identified with ash columns from 3 to 13 km high above the crater (8.5–18.5 km asl), some of which has produced abundant ash fall in nearby populations. Ashfall has been distributed in all directions around the volcano up to 2 50 km from the crater but dominantly in the east and northeast direction. The total minimum volume of non-compacted ash emitted over these three decades is >149 × 106 m3 while the estimated total volume of lava emitted in the form of domes is >70 × 106 m3.The average ash mass load is 32 g/m2 and the ash is commonly deposited <30 km from the crater and up to 250 g/m2 have been deposited in periods of intense activity. Ash grainsizes range from coarse to extremely fine (MdPhi 1–6) with up to 37% of particles smaller than 10 μm and up to 10% smaller than 2.5 μm. Medium lapilli (MdPhi −3) was ejected during a sub Plinian event in 2001.Ash emission is common in both dome growth and destruction phases, as well as in the clearing of the conduits during explosive phases in the absence of domes. Vitreous lithic fragments are produced by fragmentation of the degassed lava domes in the vent. Higher amounts of vesicular clasts, individual glass particles and crystals, on the other hand, are associated with magma ascent into a more open vent. The higher percentage of accidental lithic particles is linked to clearing of the vent.

Multi-objectives occupant-centric control of thermostats and natural ventilation systems in cold climate conditions using real-time occupant-related information

Recently, Occupant-Centric Controls (OCCs) have attracted great attention. Many studies have applied OCCs to mechanical ventilation systems, while natural ventilation systems have gathered much less attention. The natural ventilation effect, driven by opening windows or vents, can be effective in improving indoor air quality, however, result in a leakage of interior heating energy in winter in cold climates. Therefore, the controls of thermostats and natural ventilation systems shall be designed well so that satisfying levels of thermal comfort, air quality and energy conservation can be simultaneously guaranteed. This study proposes an OCC and applies it to thermostats and natural ventilation systems for indoor thermal comfort, air quality and heating energy management. The strategy comprises three controllers: occupancy-based on-off controller, controller of setpoint of indoor air temperature and window openness controller. First, real-time profiles of heat gains from occupants and window openness were collected by employing vision-based detection. Second, a parametric building simulation study was conducted, and then simulation data were generated to develop predictive shallow artificial neural networks for forecasting the indoor conditions and energy performance of the investigated room. Third, the performance of the proposed strategy was examined. Compared to the baselines, the control could offer a decrease in building heating loads by between 43.4% and 63.8 % and an improvement of predicted mean vote levels by 0.36–0.37. The proposed OCC could also maintain indoor CO2 concentrations below 1000 ppm for about 91 % of the studied time, while 84.2 % of the time with several peaks over 3000 ppm in the baseline cases.

Control Authority of a Single-Surface Parafoil with Bleed-Air Spoilers

Bleed-air control of ram-air parafoils is a lightweight and cost-effective mechanism that enables significant landing accuracy improvements compared to traditional trailing edge brake control due to the addition of direct glide slope control. Single-surface parafoil canopies have been shown to be lightweight and possess similar flight behavior as their ram-air counterparts. The design of bleed-air spoilers is more challenging for single-surface canopies, which lack the internal ram-air that provides a high pressure differential at any chordwise location. This paper explores bleed-air spoilers on single-surface parafoils with a focus on turn rate and glide slope control capabilities. Through a flight test campaign, it was shown that bleed-air spoilers on a single-surface parafoil provide both turn rate control from asymmetric vent opening and glide slope change from symmetric vent opening. Vents located far forward at the 10% chord location yield substantial control response with a maximum turn rate response of 38 deg/s and a maximum glide slope change of 58%. Vents located farther aft at 30, 50, and 70% chords demonstrated diminished control authority. Varying the spanwise locations of the spoilers revealed that the outermost vents had negligible lateral and longitudinal control authority.

Assessing lava flow susceptibility at neighbouring volcanoes: Nyamulagira and Nyiragongo volcanoes, Virunga Volcanic Province

Assessing volcanic hazards in locations exposed to multiple central volcanoes requires to consider multiple potential eruption sources and their respective characteristics. While this is common practice in ashfall hazard assessment, this is generally not considered for topography-controlled volcanic flow processes. Yet, in volcanic areas with closely spaced volcanic systems, eruptions fed from several contrasted volcanic systems might threaten one given area. Considering the case of the Nyiragongo and Nyamulagira volcanoes in the Virunga Volcanic Province (D.R.Congo), we present a method to produce a combined lava flow inundation susceptibility map that integrates both volcanoes. The spatial distribution of the probability of vent opening for the next eruption is separately constrained for both volcanoes based on the mapping of historical and pre-historical eruptive vents and fissures. The Q-LavHa lava flow probability model is then calibrated separately for each volcano, considering several historical lava flows of Nyamulagira (2004, 2006, 2010) and Nyiragongo (2002). The maps for the two volcanoes are thereafter integrated based on a weighted sum of both individual lava flow inundation probability maps, assuming historically-based relative eruption frequency of the two volcanoes. The accuracy of this probabilistic susceptibility map for the most active volcanic region in Africa was unfortunately validated by the May 2021 lava flow produced by Nyiragongo. This map was discussed and validated in 2019 with local scientists, as well as representatives of disaster management and urban planning institutions, but was not included in the regional contingency plan ahead of the 2021 eruption crisis. Updating the volcanic crisis and evacuation management plans with this lava flow probability map could contribute to reinforce risk awareness among the population and inform the future development of the city of Goma.

Structural Control at Monte Somma and Vesuvio during the Last 5600 Years through Time and Space Distribution of Volcanic Vents

Vesuvio is likely the most if not one of the most dangerous volcanoes in the world. It is an active volcano, quiescent since 1944. The activity of the Monte Somma and Vesuvio volcanic complex is commonly referred to as two central volcanic edifices, namely Monte Somma and Vesuvio. Nevertheless, the opening of numerous eruptive fissures and related vents have characterized Monte Somma and Vesuvio throughout their lives. Spatter cones, spatter ramparts, and related eruptive fissures are disseminated downslope of Vesuvio’s main cone and on the southern slopes of the volcano. Similarly, cinder cones, spatter cones, and welded spatters are distributed in the sequence cropping out on the Monte Somma cliff and on the northern slopes of Monte Somma. In this work, a total of 168 eruptive vents have been identified and characterized in a GIS environment in which field data have been merged with relevant information from historical maps and documents. These vents have been arranged into units bounded by unconformities (Unconformity Bounded Stratigraphic Units) defining the eruptive history of the volcano. Alignments of vents and eruptive fissures within each unit have been compared with regional tectonic elements and the volcano-tectonic features affecting Monte Somma and Vesuvio during the last 5600 years, thus inferring that different structural trends were active in the different stratigraphic units. In particular, we show that the N300°–320° regional, Apennine, left-lateral, strike-slip fault system, the N040°–055° Torre del Greco direct fault system, the N70° and the EW fault system, and the generally NS oriented group of local brittle elements, all analyzed here, were differently active during the investigated time span. These tectonic trends might control the position of the eruptive fissures and vents in case of future unrest of the volcano.

Design and evaluation of thermal insulation of air layer for sentry building envelopes

The prevalence of small-scale structures, such as sentry buildings, has become widespread, with many of these buildings exposed to the outdoor environment and exhibiting suboptimal thermal insulation in their envelopes. Through a comprehensive study of outdoor disturbances, the most unfavourable envelope was identified. In light of this finding, we have designed static air layer sentry buildings (SAL-SB) and dynamic air layer sentry buildings (DAL-SB). The study conducted experiments and numerical simulations to evaluate the impact of air layer thickness, vent opening forms, and inlet velocities on the thermal insulation of sentry buildings. The results showed that both the SAL and DAL effectively improved thermal insulation, and a thickness of 25 cm has been found to offer the best thermal insulation. However, considering the balance between thermal insulation and cost-effectiveness, a thickness of 15 cm is recommended. Additionally, for DAL, an inlet velocity of 3 m/s is the threshold for switching the heat transfer direction on the roof. These findings provide novel insights into enhancing the thermal environment.

Exploring Overpressure Events in Compartment Fires

For more than a century, smoke explosions have been documented in the fire research literature. Yet even with this long history, smoke explosions have received very little attention in the fire research community. The few review articles on unexplained explosions (overpressure events) have adopted the conventional names of smoke explosions, backdraft, smoke gas explosions or rapid fire progression. Anecdotal evidence from firefighters have shown a number of overpressure events that cannot be explained as a gas leak or flammable liquids ignition. In this study, experiments were conducted in a plywood lined compartment with a timber crib as a sustained fire source and the ignition source. The compartment had a single vent that was open for the entire time. After an extended period of burning, the flames detached from the crib, traveled around the compartment, and finally self-extinguished. Sometime after the flames self-extinguished, the compartment erupted in flames culminating in a large horizontal flame projecting more than 2 m from the vent opening. In this study, a consistent cycle that leads to an overpressure event has been identified. A total of 29 overpressure events were created in 13 experiments with many experiments experiencing multiple overpressure events. Gas species, compartment temperatures, vent velocities, and compartment pressure were all recorded during the experiments. Conditions in the compartment immediately prior to the overpressure event are reported. Having demonstrated that an overpressure event within a combustible compartment can be reproduced, future research is recommended to better quantify the conditions leading to an overpressure event.

Simplified vented acoustic window with broadband sound transmission loss

A vented window design is presented allowing for air ventilation and improved sound reduction for urban traffic noise. The window design aims to be of simple construction, consisting of double-glass cells with a two-sided vent opening and a single internal division that splits the inner cavity into two resonators tuned at about 200 and 400 Hz. The basic window cell is modeled by means of a transmission matrix model, as well as through a finite element simulation. These provide an insight into the physical performance principles of the device, and produce results comparable with the acoustic measurements. Preliminary experiments showed the convenience of covering the resonator openings with flow-resistive absorbing material. This helps in raising the spectral sound transmission dips, improving the single number rating according to ISO 717-1:2020 with a measured weighted sound reduction index Rw(C,Ctr)=18(0;0) dB. The comparative performance of the window related to other windows reported in the literature is shown in a graph relating sound reduction and open ventilation area ratio. A reference performance curve is proposed corresponding to the maximum sound transmission loss of a pure constriction with the same open area. The sound reductions offered by different windows can be compared depending on how much their performance, according to Rw, departs above or below this reference curve. The window design performs according to the reference curve.

Buoyancy-Driven Ventilation in the Interior-Most Flats of an Apartment Building with Different Corridor Vent Opening Condition

In the present work, computational simulations are conducted for an apartment building to investigate the bouncy-driven airflow in the corridor and inside the rooms. Two types of corridor vent openings are provided through which the hot light air moves to the ambient. Two floors are considered for the study. The simulations are conducted with three different temperature difference conditions between walls and room inside air such as; ∆T=10OC, ∆T=15OC, ∆T=20OC for two different corridor vent opening configurations. When the corridor vent openings are kept only in front of the doors and windows, recirculation zones below the roof near the air entry region are observed and part of the air escaped through the inlet. In the case of a wide corridor vent opening, air does not escape through the inlet. With increase in ΔT, the airflow increases irrespective of vent positions. Mainly the area of the rooms is well ventilated closer to the door position. It is also observed that the lower floor is relatively well-ventilated as compared to the upper floor. The ACH increases with increase in vent opening and it also increases with increase in ∆T.

Crankcase Explosions in Marine Diesel Engines: A Computational Study of Unvented and Vented Explosions of Lubricating Oil Mist

Accidental crankcase explosions in marine diesel engines are presumably caused by the inflammation of lubricating oil in air followed by flame propagation and pressure buildup. This manuscript deals with the numerical simulation of internal unvented and vented crankcase explosions of lubricating oil mist using the 3D CFD approach for two-phase turbulent reactive flow with finite-rate turbulent/molecular mixing and chemistry. The lubricating oil mist was treated as either monodispersed with a droplet size of 60 μm or polydispersed with a trimodal droplet size distribution (10 μm (10 wt%), 250 μm (10 wt%), and 500 μm (80 wt%)). The mist was partly pre-evaporated with pre-evaporation degrees of 60%, 70%, and 80%. As an example, a typical low-speed two-stroke six-cylinder marine diesel engine was considered. Four possible accidental ignition sites were considered in different linked segments of the crankcase, namely the leakage of hot blow-by gases through the faulty stuffing box, a hot spot on the crankpin bearing, electrostatic discharge in the open space at the A-frame, and a hot spot on the main bearing. Calculations show that the most important parameter affecting the dynamics of crankcase explosion is the pre-evaporation degree of the oil mist, whereas the oil droplet size distribution plays a minor role. The most severe unvented explosion was caused by the hot spot ignition of the oil mist on the main bearing and flame breaking through the windows connecting the crankcase segments. The predicted maximum rate of pressure rise in the crankcase attained 0.6–0.7 bar/s, whereas the apparent turbulent burning velocity attained 7–8 m/s. The rate of heat release attained a value of 13 MW. Explosion venting caused the rate of pressure rise to decrease and become negative. However, vent opening does not lead to an immediate pressure drop in the crankcase: the pressure keeps growing for a certain time and attains a maximum value that can be a factor of 2 higher than the vent opening pressure.

Quantifying extended discharge rate of inert gas agents to increase hold time for protection of enclosures with openings

The application of gas-fire-suppression systems encounters a challenge that oxygen concentration tends to return to the original value in post-discharge time if open vents are present in a protected enclosure. Extending discharge becomes necessary to maintain oxygen concentration to prevent a fire resurgence in this enclosure. Until now the extended discharge rate must be evaluated individually by full-scale tests and no international standards specify the requirements in extended discharge. In this study, a formula was proposed to calculate the extended discharge rate as a function of opening size. A series of tests were conducted to investigate the oxygen concentration against the opening size in an apartment, followed by numerical simulations to recreate these tests. Then the discharge was extended in the simulations. Results show that the oxygen concentration was maintained between 10.5 % and 12.9 % in the apartment excepted the location next to the open door if the proposed discharge rate was adopted in the extended discharge time. Thus, this study proposal a universal method to quantify the extended discharge rate for a protected enclosure with openings.

Positive Pressure and Negative Pressure Irrigation Dynamics with Different Needle Designs Using Computational Fluid Dynamics

This study aimed to investigate the irrigation dynamics of the positive pressure side-vented (SV) needle, EndoVac (micropores) needle and modified apical negative pressure (mANP) open-ended needle using computational fluid dynamics (CFD). A simulation of a prepared root canal (conical frustum) of 15 mm length with an apical diameter of 0.40 mm following Protaper F4 apical preparation was created using three-dimensional (3D) CAD software. The 3D simulated needle of SV 30G needle, EndoVac with micropores needle and mANP, 30G flat open-ended needle were also created. The irrigation dynamics were evaluated through transient CFD simulations. In addition, the irrigation dynamics of mANP at 0.2 mm, 0.5 mm, and 1.0 mm short from the working length were also assessed. The EndoVac and mANP showed negative apical static pressure and streamline patterns able to reach the apical region, thus indicating negligible extrusion. Meanwhile, SV showed positive apical static pressure and almost nonexistent streamlines beyond the needle tip. The SV showed the highest wall shear stress (WSS) magnitude of 1030Pa whereas Endovac (161 Pa) and mANP1 (258 Pa). However, SV revealed lower average WSS (10 Pa) compared to mANP1 (13 Pa) and mANP2 (11 Pa). This is due to SV developed a localised maximum WSS opposite the open vent area only therefore, uneven distribution of WSS. The EndoVac system developed a localised maximum WSS in the pair of micropores furthest away from the apical. CFD analysis of the EndoVac, mANP and SV showed different technique approach, needle design and needle depths insertion affect the irrigation dynamics pattern and magnitude.

Design of a submarine main ballast tank flood and vent openings mechanisms

Besides the piping systems used for blowing the main ballast tanks of a submarine by feeding compressed air, a great importance must be given to the flood and vent openings and the mechanisms that operate the covers. From an engineering standpoint, the flood openings must be as small as possible to minimize the noise generated by the water flow.Their number and cumulated area must be determied as to avoid over pressure when feeding compressed air into the ballast tanks that may lead to structural damage. The requirements for designing of such systems are covered by the Class and Administration rules and regulations.

Characterizing SO2 Emission Rate, Thermal Anomalies, from Opened and Closed Vent System at Agung, Bromo, and Sinabung Volcanoes in Indonesia

Agung, Bromo, and Sinabung Volcanoes have high volcanic activity over the last decade, and have different eruption characteristics. Hence, it would be fascinating to study the characteristics of their volcanic activity patterns based on SO2 emission rates and thermal anomaly correlated with the seismicity data. The SO2 emission rate measurement was carried out using the Differential Optical Absorption Spectroscopy (DOAS), and calculated based on SO 2 column density, distance of measurement, wind speed, and wind direction. In addition, SO2 emission was detected using Ozone Monitoring Instrument (OMI) images with daily global coverage. Thermal anomaly detection was performed using Advance Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of Thermal Infrared (TIR) subsystem with high spatial resolution (90x90 m). ASTER TIR images were corrected for radiometric and thermal atmospheric. The emissivity and brightness temperature separation algorithm was applied to obtain surface temperature of Agung, Bromo, and Sinabung Volcanoes. All the data were correlated with the seismicity of each volcano. The SO2 emission rates correlate with the magma ascent to the shallow depth in an open system volcano (Bromo Volcano). In the closed-system volcanoes (early phase of Agung and Sinabung), SO2 emission was detected after the transition of closed to open system. Magmatic injection from the reservoir to the shallow depth was detected as thermal anomalies, such as in Agung Volcano. Whereas in Bromo Volcano, the thermal anomaly was insignificant since Bromo Volcano has an explosive eruption at a short period, so the ASTER image could not observe the thermal anomaly on the eruption time. Thermal anomaly pattern in Sinabung Volcano was the manifestation of new magmatic injection to the shallow depth. Therefore, their increase serves as indicators for the increasing magmatic activity prior to the eruptions. Keywords: SO2 emission rate, thermal anomaly, DOAS, OMI, ASTER, Open Vent, Closed Vent

Assessing impending hazards from summit eruptions: the new probabilistic map for lava flow inundation at Mt. Etna

The development of probabilistic maps associated with lava flow inundation is essential to assess hazard in open vent volcanoes, especially those that have highly urbanized flanks. In this study we present the new lava flow hazard map linked to the summit eruptions of Mt. Etna, which has been developed using a probabilistic approach that integrates statistical analyses of the volcanological historical data with numerical simulations of lava flows. The statistical analysis of volcanological data (including vent location, duration and lava volumes) about all summit eruptions occurred since 1998 has allowed us both to estimate the spatiotemporal probability of future vent opening and to extract the effusion rate curves for lava flow modelling. Numerical simulations were run using the GPUFLOW model on a 2022 Digital Surface Model derived from optical satellite images. The probabilistic approach has been validated through a back-analysis by calculating the fit between the expected probabilities of inundation and the lava flows actually emplaced during the 2020-2022 period. The obtained map shows a very high probability of inundation of lava flows emitted at vents linked to the South East Crater, according to the observation of the eruptive dynamics in the last decades.

Experimental study on the overpressure variation and flame mode of premixed fuel-air deflagration in a semi-closed enclosure

A small scale combustible gas venting explosion experimental system with a volume of 0.002 m3/0.0035 m3 was established, and the venting explosion experiments of ‘petroleum fuel vapor-air mixture’ under various vent sizes were conducted. The characteristics of overpressure and flame parameters under different vent sizes were obtained and the different venting modes were classified. The research results show that the overpressure history of petroleum fuel vapor/air mixture during the venting explosion process could be divided into four types, and four typical overpressure peaks induced by various phenomena were captured. With increasing venting coefficient Kv, the number of overpressure peaks decreases, but the value of overpressures gradually increases. When the value of Kv was relatively small (Kv ≤ 3.329) a ball or mushroom flame cloud was formed in the external field. When the value of Kv was comparatively large (4.560 ≤ Kv), a jet-like flame was formed in the external field. With the increase of the venting coefficient Kv, the internal maximum overpressure peak, the external maximum overpressure peak along vertical direction, the external flame height dimensionless number along the vertical direction and the external flame speed dimensionless number along the vertical direction showed an increasing trend, while the external flame diameter dimensionless number along the horizontal direction and the external flame speed dimensionless number along horizontal direction showed an decreasing trend. If treat ‘the least number of overpressure peaks’ and ‘the external explosion doesn’t occur’ as the ideal state of the venting explosion process, the vent opening needs to be set to ensure that 4.560 ≤ Kv ≤ 8.585.

Pre-existing fractures and eruptive vent openings during the 2021 Fagradalsfjall eruption, Iceland

Pre-existing fractures and eruptive vent openings during the 2021 Fagradalsfjall eruption, Iceland

A Comparative Evaluation of Vertical Marginal Gap for Vented and Precemented Cad-Cam Zirconium Copings on Angulated Abutments: An In vitro Study.

To evaluate vertical marginal gap after cementation of Zr (zirconium) copings with palatal vent, open vent, and precementation technique on angulated abutments resulting from cement entrapment between intaglio surface of copings and angulated abutments. Twenty-four angled abutments and 24 CAD-CAM Zr copings were assigned to three groups depending on the type of cementation technique, comprising eight copings with palatal vent, open vent, and no vent, respectively. Vertical marginal gaps between abutment shoulder and coping margin were evaluated at four points: buccal, palatal, mesial, and distal. The readings were statistically analyzed. The average mean value of vertical marginal gap at all sites for Group A with palatal vent was 158.45, for Group B with open vent was 151.84, and for Group C using precementation technique was 163.58. A statistically non-significant difference was seen for values between all sites (P > 0.05) for all groups. The average vertical marginal gap for Group B was comparatively lower compared to Groups A and C.

A Health Indicator of Aluminum Electrolytic Capacitors Based on Strain Sensing

This letter proposes a novel health indicator for aluminum electrolytic capacitors (AECs) based on strain sensing in a non-intrusive manner. The indicator leverages the mechanism that the internal pressure of AECs gradually increases with the electrochemical reaction caused by degradation, thereby, with a change in strain. The results reveal the proposed health indicator is highly sensitive to capacitor degradation and meanwhile highly resistant to interferences. Furthermore, an End-of-Life criterion for the AECs is proposed in this indicator, which is corresponding to the moment of open vent. The applicability of this indicator is verified for constant conditions, dynamic operating conditions, and overvoltage conditions. In addition, the effect of temperature is analyzed. The proposed health indicator can be used to determine the time-to-failure of testing samples in accelerated life testing and condition monitoring of AECs.