Differential Pressure Gauge Research Articles

Array Observations of the 2012 Haida Gwaii Tsunami Using Cascadia Initiative Absolute and Differential Seafloor Pressure Gauges

The purpose of this article is to test the ability of the seafloor pressure sensors utilized in the Cascadia Initiative (CI) experiment (Toomey et al. , 2014) to provide useful recordings of tsunamis, and to compare the performance of the different types of seafloor pressure sensors for long‐period recordings. These tests are performed through analysis of CI seafloor pressure recordings of the 2012 Haida Gwaii tsunami. Seafloor pressure measurements are a central part of tsunami warning systems. Deep‐ocean Assessment and Reporting of Tsunamis (DART) buoy systems, designed by National Oceanic and Atmospheric Administration (NOAA), are equipped with seafloor pressure sensors (also referred to as bottom pressure recorders [BPRs]), providing tsunami data in real time (Eble and Gonzalez, 1991; Gonzalez et al. , 1998; Bernard et al. , 2001; Meinig et al. , 2005; Titov et al. , 2005; Mofjeld, 2009; Rabinovich and Eble, 2015). The DART instruments are widely spaced in deep water (typically >2700 m) along coastal regions and near subduction zones. Cabled BPR arrays are becoming more common, such as the BPR array of NorthEast Pacific Time‐Series Undersea Networked Experiments (NEPTUNE)‐Canada ocean observatory (Thomson et al. , 2011), the Japan Agency for Marine‐Earth Science and Technology (JAMSTEC) BPR array (Baba et al. , 2004; Saito et al. , 2010), and the BPR array in the Cascadia basin (Rabinovich et al. , 2011). Observations of tsunamis have also been made serendipitously on pressure gauges accompanying a variety of nontsunami field programs (e.g., Drushka et al. , 2008; Lin et al. , 2015). In this study, we use seafloor pressure measurements from absolute pressure gauges (APGs), differential pressure gauges (DPGs), and DART BPRs to study the tsunami caused by the 2012 Haida Gwaii earthquake. The APG, used by the DART and increasingly in other oceanographic studies (Ito et al. , 2011; Chadwick et al. …

Analysis of the flow imbalance in the KSTAR PF cryo-circuit

The KSTAR PF cryo-circuit is a quasi-closed circulation system in which more than 370g/s of supercritical helium (SHe) is circulated using a SHe circulator. The heated helium from superconducting magnet is cooled through sub cooler (4.3K). The circulator is operated at 4.5K and 6.5bar, and the pressure drop of the circuit is kept at 2bar in order to maintain the supercritical state and circulator stability. The circuit is connected with helium refrigerator system, distribution system, and supercritical magnet system. It has a hundred branches to supply supercritical helium to the poloidal field superconducting magnet. The branch was designed to optimize the operation conditions and they are grouped for one cryogenic valve has the same length within the cardinal principle of the optimization. Five cryogenic valves are installed to control the mass flow rate, and seven orifice mass flow meters, differential pressure gauges and temperature sensors were installed in front of the magnet in the distribution because upper magnet and lower magnet is symmetric theoretically. The cryogenic pipe line was manufactured with elevation about 10m between upper magnet and lower magnet. The inlet and outlet helium feed-through were installed at the coil inside in case of KSTAR PF1–PF5 upper magnet and lower magnet. The flow imbalance is caused by void fraction and it could be changed due to manufacturing process even if it has the same length of cooling channel. This creates an imbalance among cooling channels and temperatures are slightly different. The flow was reduced and detoured due to the pressure rise rapidly at inlet and outlet during magnet operation. Therefore, the orifice mass flow meters are installed in front of the PF1–PF5 upper magnet and lower magnet in order to investigate flow trend and the thermos-hydraulic behavior is analyzed during PF magnet operation.

A new concept for an ocean bottom pressure meter capable of precision long‐term monitoring in marine geodesy and oceanography

AbstractLong‐term vertical seafloor displacements and geostrophic changes in the water column height could be easily monitored if pressure meters were less susceptible to drift. Currently, these signals, which have typical amplitudes from decimeters to less than 1 mm/yr, cannot be differentiated from instrumental drift. In this paper, we introduce and outline a new constructional concept for an ocean bottom pressure meter that aims for unequivocal detection and monitoring of long‐term trends. The concept is based on a differential pressure sensor that measures the pressure difference between the environment and a reference pressure within a sealed volume. This sealed volume conserves the instantaneous pressure at the moment of its closure at the monitoring location in a temperature‐compensated manner. Furthermore, the approach enables easy in situ calibration of the differential pressure gauge by simply opening the reference pressure chamber to the environment and checking the zero point offset.

Estimation of azimuthal anisotropy in the NW Pacific from seismic ambient noise in seafloor records

We analysed background surface waves in seismic ambient noise by cross-correlating continuous records of eight ocean bottom seismometers and nine differential pressure gauges deployed in the northwestern Pacific Ocean by the PLATE project. After estimating the clock delay and instrumental phase responses of differential pressure gauges by using cross-correlation functions, we measured average phase velocities in the area of the array for the fundamental-, first higher- and second higher-mode Rayleigh waves, and the fundamental-mode Love waves at a period range of 3–40 s by waveform fitting. We then measured phase-velocity anomalies of fundamental-mode and first higher-mode Rayleigh waves for each pair of stations at a period range of 5–25 s, and corrected the effect of variation in water-depths. The seismic anomalies imply the presence of strong azimuthal anisotropy beneath the eastern part of array. The direction of maximum velocity is approximately N35°E in the fossil seafloor spreading direction perpendicular to magnetic lineations from the ancient triple junction at this location. The peak-to-peak intensity of shear-wave velocity anisotropy in the mantle is ∼7 per cent.

Hydroacoustic signals of Antarctic origin detected at ocean-bottom seismic stations off New Zealand

Glacial calving from polar ice sheets is an important indicator of global climate change, and knowledge of ice discharge rates is useful for predicting global sea level variability and deep ocean circulation patterns. Since calving events are difficult to observe in-situ due to the remoteness of polar regions, the remote detection of hydroacoustic signals originating from these events is a useful monitoring tool for climatologists. We have observed hydroacoustic T-phases on an Ocean Bottom Seismic (OBS) network of 30 seismometers and differential pressure gauges that was deployed off the South Island of New Zealand in 2009–2010. These signals are emergent and strongly dispersive, containing most of their energy in the band between 5 and 15 Hz. We estimated backazimuths for events recorded on differential pressure gauges using array beamforming and F-K analysis. Our results suggest that some observed events originate in the vicinity of Ninnis and Mertz glaciers on George V Coast, East Antarctica, in general agreement with epicenters located by prior surface-wave based calving detection studies.

Neutral Density Measurement of Ion Thruster with Differential Pressure Gauge

Neutral Density Measurement of Ion Thruster with Differential Pressure Gauge

On the Systematic Long-Period Noise Reduction on Ocean Floor Broadband Seismic Sensors Collocated with Differential Pressure Gauges

Vertical-component broadband seismic data collected on the ocean floor at regional distances from the shore and water depths on the order of 1-2 km are polluted by noise due to ocean infragravity (IG) waves in a period range (20-200 s) that is critical for regional structure studies and the determination of moment tensors for regional earthquakes. Using broadband seismic and differential pressure gauge data collected at the Monterey Ocean Bottom Broadband (MOBB) observatory, which has been operational since 2002, we identify the optimal length of time window to obtain the transfer function between the vertical seismic and pressure records. The maximum reduction in IG-wave-induced noise is obtained by using a one-day stack of transfer function inferred from data segment collected in the last 24 hours prior to data in which the noise removal method is applied. We show that a one-year stack of transfer function effectively reduces the noise level in the period band 50-100 s by 20 dB and by up to 15 dB at shorter periods. This resultant 20 dB noise reduction is comparable to that obtained from the one-day stack of transfer function. Our result suggests that the removal of noise induced by IG waves on MOBB vertical-component data can be done routinely without continuously calibrating the transfer function, also in near-real time, and is therefore also useful for routine regional moment tensor de- termination. This noise removal method has been implemented in the moment tensor determination system of the Northern California Seismic System.

Design on Flow Measurement Solution with Intelligent Efflux Coefficient Standard Throttling Gear

t is an in-depth research on the span measurement range ratio that standard throttling gear measures the flow is too small, and proposes the design method of multi-efflux coefficient standard throttling gear. Expanding the lower limit of measurable flow according to the relevant national standards GB/T2624-2006. Solution divides the span measurement range into several segments, each piece span measurement range corresponds to a differential pressure gauge, and calculates corresponding efflux coefficient depending on the GB/T2624-2006 to get many outflow coefficients on the different span measurement sub-range section. Intelligent system chooses corresponding efflux coefficients based on different differential pressure, and ensures measurement accuracy at the same time of expanding the lower limit.

Bubble Behavior and Flow Structure on Bubble Collapse Phenomena in a Venturi Tube

A micro-bubble generator with a venturi tube generates a large number of micro-bubbles with a diameter of 10 μm ― 1 mm by bubble collapse. The bubble collapse is caused by pressure recovery in the diverging region of the venturi tube. The pressure recovery is expected to be a shock for supersonic flow in gas-liquid two-phase flow. However, a profile of Mach numbers to flow direction of the venturi tube has not been estimated experimentally. The present study reveals mechanisms of a bubble collapse. In order to achieve the objectives, we observe bubble behavior with the bubble collapse. In addition, we measure pressure and volumetric void fraction profiles in the flow direction. Pressure is measured by a differential pressure gauge. Void fraction is measured by a constant electric current method and Maxwell' s theory. From these measurements, gas-liquid mixture velocity, sonic speed and Mach number are estimated. In experimental results, bubble collapse is observed with high liquid inlet velocity. When bubble collapse is caused, bubbles expand once into a divergence region of the venturi tube. After that, they contracted rapidly and broken up into a great number of tiny bubbles. Pressure decreases sharply around the throat and increase at the bubble collapse point. On the other hand, the void fraction increase downstream from the throat and decrease around the bubble collapse point. From these results, it is confirmed that the flow is supersonic flow between the throat and the bubble collapse point, while it becomes subsonic flow downstream of the point. Therefore, it is proposed that a shock is present at the bubble collapse point.

Basal interstitial water pressure in laboratory debris flows over a rigid bed in an open channel

Abstract. Measuring the interstitial water pressure of debris flows under various conditions gives essential information on the flow stress structure. This study measured the basal interstitial water pressure during debris flow routing experiments in a laboratory flume. Because a sensitive pressure gauge is required to measure the interstitial water pressure in shallow laboratory debris flows, a differential gas pressure gauge with an attached diaphragm was used. Although this system required calibration before and after each experiment, it showed a linear behavior and a sufficiently high temporal resolution for measuring the interstitial water pressure of debris flows. The values of the interstitial water pressure were low. However, an excess of pressure beyond the hydrostatic pressure was observed with increasing sediment particle size. The measured excess pressure corresponded to the theoretical excess interstitial water pressure, derived as a Reynolds stress in the interstitial water of boulder debris flows. Turbulence was thought to induce a strong shear in the interstitial space of sediment particles. The interstitial water pressure in boulder debris flows should be affected by the fine sediment concentration and the phase transition from laminar to turbulent debris flow; this should be the subject of future studies.

TIARES Project—Tomographic investigation by seafloor array experiment for the Society hotspot

We conducted geophysical observations on the French Polynesian seafloor in the Pacific Ocean from 2009 to 2010 to determine the mantle structure beneath the Society hotspot, which is a region of underlying volcanic activity responsible for forming the Society Islands. The network for Tomographic Investigation by seafloor ARray Experiment for the Society hotspot (TIARES, named after the most common flower in Tahiti) is composed of multi-sensor stations that include broadband ocean-bottom seismometers, ocean-bottom electro-magnetometers, and differential pressure gauges. The network is designed to obtain seismic and electrical conductivity structures of the mantle beneath the Society hotspot. In addition to providing data to study the mantle structure, the TIARES network recorded unprecedented data of pressure and electromagnetic (EM) signals by tsunamis associated with large earthquakes in the Pacific Ocean, including the 2010 Chilean earthquake (Mw 8.8).

Infragravity wave source regions determined from ambient noise correlation

We use a backprojection method to determine dominant directions of ocean infragravity waves from 60–200 s period from cross correlations between 5 ocean bottom differential pressure gauges located off the coast of Sumatra. We observe infragravity waves arriving from all directions, but there is a dominant source direction that represents coherent propagation along the coast from the southeast or from the south. This study demonstrates the effectiveness of our projection technique, which may be applied to past and future seismic data to improve models of ocean infragravity wave generation and tsunami propagation.

Seismic Ambient Noise Characterization of a New Permanent Broadband Ocean Bottom Seismometer Site offshore Catalonia (Northeastern Iberian Peninsula)

The scientific importance of long-term ocean-floor seismic observatories has been widely and internationally recognized by earth science communities. In addition to their usefulness in investigating global-scale geophysical processes, long-term ocean-floor observations are also required to better constrain regional tectonics. However, the implementation of ocean-floor seismic stations is a difficult task, and efforts have been made for more than two decades to resolve the technological and logistical issues associated with such deployments (Romanowicz et al. 2009; Suyehiro et al. 2006). Different programs in the United States and Canada ( e.g. , NEPTUNE Project, http://www.neptune.washington.edu), Japan ( e.g. , ARENA Project, Massion et al. (2004).), and in Europe ( e.g. , ESONET Project, http://www.oceanlab.abdn.ac.uk/research/esonet.php) have promoted ocean-floor observatories, most of them multidisciplinary. A review of seafloor observatory science can be found in Favali and Beranzoli (2006). The first initiative for long-term seafloor seismic monitoring in Spain was successfully realized on August 12, 2005, when a permanent broadband ocean-bottom seismometer (OBS) and a differential pressure gauge (DPG) were installed at about 50 km offshore of the region of Catalonia in the northeastern Iberian Peninsula (Figure 1). The ocean-floor station was completely integrated into the Catalan Seismic Network (CSN) in October 2007, when satellite transmission made it possible to have continuous and real-time data available at the network data center in Barcelona. The station, with geographical coordinates 40.71°N and 1.36°E, has the code COBS at the International Registry of Seismograph Stations of the International Seismological Centre. The project was initially designed with the main goal of improving the understanding of the seismicity of the surrounding region, which is densely populated and industrially very active. The presence of nuclear power plants and chemical and oil industry facilities in the area has major implications on the seismic risk assessment of the region. Moreover, the fact that some …

Flow and Pressure Distribution in Fuel Cell Manifolds

The manifold is an essential part of the fuel cell stack. Evidently, evenly distributed reactants are a prerequisite for an efficient fuel cell stack. In this study, the cathode manifold ability to distribute air to the cells of a 70 cell stack is investigated experimentally. By means of 20 differential pressure gauges, the flow distribution is mapped for several geometrical and operating conditions. Special attention is given to the inlet conditions of the manifold. Here, a diffuser design was constructed in order to replace the conventional circular inlet design. The diffuser design showed significant improvements to the flow distribution in comparison to the circular design. Moreover, the best flow distribution was found using a U-shaped configuration.

Effects of sea states on seafloor compliance studies

Gas hydrates affect the bulk physical properties of marine sediments, in particular, elastic parameters. Shear modulus is an important parameter for estimating the distribution of hydrates in the marine sediments. However, S-wave information is difficult to recover without proper datasets. Seafloor compliance, the transfer function between pressure induced by surface gravity waves and the associated seafloor deformation, is one of few techniques to study shear modulus in the marine sediments. The coherence between recorded time series of displacement and pressure provides a measure of the quality of the calculated transfer function, the seafloor compliance. Thus, it is important to understand how to collect high coherence datasets. Here we conducted a 10-month pilot experiment using broadband seismic sensors and differential pressure gauges. We found that data collected in shallow water depth and during rough seas gave high coherence. This study is the first time long-term data sets have been employed to investigate seafloor compliance data quality and its dependence on sea state. These results will help designing future large-scale compliance experiments to study anomalously high shear moduli associated with the presence of gas hydrate or cold vents, or alternatively anomalously low shear moduli, associated with partial melt and magma chamber.

Distribution parameter and drift velocity for two-phase flow in a large diameter pipe

In view of practical importance of the drift flux model for two-phase flow analysis in general, and in the analysis of nuclear reactor transients and accidents in particular, the distribution parameter, and the drift velocity have been studied for two-phase flow in a vertical large diameter pipe. In this, study, local measurements were performed on flow parameters, such as void fraction, gas velocity and, liquid velocity in a vertical upward air–water two-phase flow in a pipe of 200mm inner diameter and, 25m in height by using the local sensor techniques such as hot-film probes, optical multi-sensor, probes and differential pressure gauges. Two-phase flow regimes in a vertical large diameter pipe, were classified into bubbly, churn and slug flows according to the visual observation. The values of the, distribution parameter and the mean drift velocity were determined directly by their definition using experiment data of the local flow parameters in a two-phase flow in a large diameter pipe. Various existing drift flux correlations were compared with the present experimental results and experimental data obtained by other researchers. A detailed discussion on the problems of these correlations was presented in this paper.

Determination of optimum measurement points via A-optimality criterion for the calibration of measurement apparatus

A procedure for optimal selection of the measurement points to get the best calibration characteristics (for the chosen optimality criterion) of measuring apparatus is proposed. The coefficients of the calibration characteristics are evaluated by the classical least squares method. For this work, the A-optimality criterion has been used as an optimality criteria. As an example, the problem of optimal selection of the standard pressure setters (the piston gauges) during calibration of the differential pressure gage is solved. Obtained values of the optimum measurement points for the calibration of the differential pressure gage are checked via actual experiments.

P-9 空調機用電磁弁の発生加振力と配管の振動応答(ポスター要旨講演)

Abstract: To evaluate pipe stress in air conditioning units caused by fluid excitation force, we conducted an experiment in which we released compressed air from the electromagnetic valve and directly measured the excitation force generated using a load cell. We clarified the magnitude, application point and application direction of the fluid-step excitation force. We proposed a formula for computing the magnitude of the step force and showed how this formula could be used to determine the excitation force. Furthermore, we conducted an experiment using a refrigerant circulating equipment. We indirectly measured the excitation force using a differential-pressure gauge and a flow meter and demonstrated that the proposed formula was also valid for actual refrigerant.

The monterey bay broadband ocean bottom seismic observatory

We report on the installation of a long-term buried ocean-floor broadband seismic station (MOBB) in Monterey Bay, California (U.S.A.), 40 km off-shore, at a water depth of 1000 m. The station was installed in April 2002 using a ship and ROV, in a collaborative effort between the Monterey Bay Aquarium Research Institute (MBARI) and the Berkeley Seismological Laboratory (BSL). The station is located on the western side of the San Gregorio Fault, a major fault in the San Andreas plate boundary fault system. In addition to a 3-component CMG-1T seismometer package, the station comprises a current meter and Differential Pressure Gauge, both sampled at high-enough frequency (1 Hz) to allow the study of relations between background noise on the seis- mometers and ocean waves and currents. The proximity of several land-based broadband seismic stations of the Berkeley Digital Seismic Network allows insightful comparisons of land/ocean background seismic noise at pe- riods relevant to regional and teleseismic studies. The station is currently autonomous. Recording and battery packages are exchanged every 3 months during scheduled one day dives. Ultimately, this station will be linked to shore using continuous telemetry (cable and/or buoy) and will contribute to the earthquake notification sys- tem in Northern California. We present examples of earthquake and noise data recorded during the first 6 months of operation of MOBB. Lessons learned from these and continued recordings will help understand the nature and character of background noise in regional off-shore environments and provide a reference for the installa- tion of future off-shore temporary and permanent broadband seismic stations.

Trial of Multidisciplinary Observation at an Expandable Sub-Marine Cabled Station “Off-Hatsushima Island Observatory” in Sagami Bay, Japan

Sagami Bay is an active tectonic area in Japan. In 1993, a real-time deep sea floor observatory was deployed at 1,175 m depth about 7 km off Hatsushima Island, Sagami Bay to monitor seismic activities and other geophysical phenomena. Video cameras monitored biological activities associated with tectonic activities. The observation system was renovated completely in 2000. An ocean bottom electromagnetic meter (OBEM), an ocean bottom differential pressure gauge (DPG) system, and an ocean bottom gravity meter (OBG) were installed January 2005; operations began in February of that year. An earthquake (M5.4) in April 2006, generated a submarine landslide that reached the Hatsushima Observatory, moving some sensors. The video camera took movies of mudflows; OBEM and other sensors detected distinctive changes occurring with the mudflow. Although the DPG and OBG were recovered in January 2008, the OBEM continues to obtain data.