Acoustic Overpressure Signals from Fully Confined and Vented Chemical Explosions

2020 ◽  
Vol 110 (2) ◽  
pp. 742-753
Author(s):  
Anastasia Stroujkova ◽  
Mark Leidig ◽  
Aaron Ferris ◽  
Jeremy Salerno ◽  
James Lewkowicz
Keyword(s):  
Gas Flow ◽  
Free Fall ◽  
Acoustic Signals ◽  
High Amplitude ◽  
Ground Acceleration ◽  
Ground Failure ◽  
Fracture Formation ◽  
Ground Shock ◽  
Chemical Explosions ◽  
Peak Pressures

ABSTRACT We analyzed acoustic overpressure signals generated by overburied underground chemical explosions conducted in hard rock in New Hampshire in 2018. The explosions had comparable yields between 62.8 and 82.6 kg trinitrotoluene equivalent and were buried at depths between 12 and 13 m. Two explosions resulted in crater formation and gas venting, whereas the remaining explosions were fully confined and did not result in ground failure. Acoustic signals from the confined explosions were produced by the ground shock near ground zero. Acoustic signals from cratered explosions represent a combination of a ground shock signal and a time-delayed high-amplitude signal generated by gas venting. The cratering and venting occurred during the free-fall phase observed on the near-source accelerograms. We argue that the main reason for the cratering in this experiment is the low-rock porosity, preventing postexplosion pressure relief in the cavity and promoting long fracture formation during the unloading phase and subsequent containment failure. The ground-shock-induced signals were modeled using the Rayleigh integral of the near-source ground acceleration. The equations of nonlinear acoustics were used to model the observed gas venting signals produced by the gas flow from the explosion cavity to the surface. By comparing the near-source signals produced by venting to theoretical signals from surface blasts we have shown that the venting signals have significantly lower peak pressures and longer signal durations compared to surface blasts of the equivalent impulse. The observed amplitudes of the acoustic signals produced by the venting are significantly higher than the ground-shock related signals expected from overburied explosions. This is important to consider because higher acoustic amplitudes may potentially lead to errors in yield estimation.

Reaction of shallow onshore waters to ground shock

1972 ◽  
Vol 62 (6) ◽  
pp. 1543-1557
Author(s):  
M. L. Merritt
Keyword(s):  
Time History ◽  
Free Fall ◽  
Full Time ◽  
Initial Pulse ◽  
Wave Shape ◽  
Ground Shock ◽  
Impact Shock

abstract Pressures and accelerations were measured in and near numerous ponds and lakes in Amchitka during the nuclear shot CANNIKIN, using peak measuring and full time-history recording instruments. The resulting pressures and accelerations were similar in wave shape: each showed an initial pulse, a period of free fall during spall, and an impact shock. It is found that when reverberation times in the water are short compared to rise times and other characteristic times of the ground shock, the water responds as a whole, and the pressure in it is proportional to the acceleration. When reverberation times are longer than rise times, pressure overshoots and oscillates about the simple proportionality.

scholarly journals New insights for direct in situ measurement of oceanic vertical velocities in fine-scale studies.

2021 ◽  
Author(s):  
Caroline Comby ◽  
Stéphanie Barrillon ◽  
Jean-Luc Fuda ◽  
Andrea Doglioli ◽  
Roxane Tzortzis ◽  
...  
Keyword(s):  
Anthropogenic Activities ◽  
Free Fall ◽  
High Amplitude ◽  
Ocean Dynamics ◽  
General Interest ◽  
Fine Scale ◽  
Ligurian Sea ◽  
Essential Information ◽  
Order Of Magnitude

<p>Vertical velocities knowledge is essential to study fine-scale dynamics in the surface layers of the ocean and to understand their impact on biological production mechanisms, in both coastal and offshore environments. Indeed, the general interest in fine-scale and, more precisely, in the determination of vertical velocities, is explained by their key role in global oceanic balance and their impact on the vertical transfer of nutrients and carbon budget despite their low intensity. With the increasing global warming issues linked to the forcing of the carbon cycle by anthropogenic activities, the estimation of vertical velocities becomes an essential information for a better representation of biogeochemical budgets. However, these vertical velocities have long been neglected, simply parameterized, or considered as not measurable, due mainly to their order of magnitude (mm s<sup>-1</sup>), generally much lower than the one of the horizontal velocities (cm s<sup>-1</sup>). Consequently, direct <em>in situ</em> measurement of vertical velocities is still currently one of the biggest challenges in physical oceanography.</p><p>We have been working to develop a new method for direct <em>in situ</em> measurement of vertical velocities using data from different Acoustic Doppler Current Profilers (ADCPs) associated with CTD probes, and we performed a comparative analysis of the results obtained by this method. The analyzed data were collected during the FUMSECK cruise (2019, Ligurian Sea), from three ADCPs: two Workhorse (conventional ADCPs), one lowered on a carousel and the other deployed in free-fall mode, and one Sentinel V (a new generation ADCP with four classical beams and a fifth vertical beam), also lowered on a carousel. Our analyses provided profiles of vertical velocities of the order of mm s<sup>-1</sup>, as expected, with standard deviations of a few mm s<sup>-1</sup>. While the fifth beam of the Sentinel V has shown a better accuracy than conventional ADCPs, the free-fall technique has provided a more accurate measurement compared to the carousel technique. Some of these measurements were gathered along the edge of the Northern Current and this new information on coastal edge currents represents a key point for the future improvement of coastal altimetry in particular.</p><p>Finally, this innovative study opens up the possibility to perform simple and direct <em>in situ</em> measurements of vertical velocities, coupling the free-fall technique with a five-beam ADCP. Hence, we plan to deploy a free-falling Sentinel V in offshore areas characterized by intense fine-scale ocean dynamics, but also and above all, in coastal areas, where topographic forcings are typically the source of high amplitude vertical velocities.</p>

scholarly journals Spatially and temporally systematic hydrologic changes within large geoengineered landslides, Cromwell Gorge, New Zealand, induced by multiple regional earthquakes

2021 ◽  
Author(s):  
GA O'Brien ◽  
SC Cox ◽  
John Townend
Keyword(s):  
Groundwater Level ◽  
Spectral Characteristics ◽  
Seismic Energy ◽  
High Amplitude ◽  
Ground Acceleration ◽  
Earthquake Parameters ◽  
Groundwater Levels ◽  
Time To Peak ◽  
Long Duration ◽  
Groundwater Level Changes

©2016. American Geophysical Union. All Rights Reserved. Geoengineered groundwater systems within seven large (23 × 104–9 × 106 m2), deep-seated (40–300 m), previously slow-creep (2–5 mm/yr.) schist landslides in the Cromwell Gorge responded systematically to 11 large (Mw > 6.2) earthquakes at epicentral distances of 130–630 km between 1990 and 2013. Landslide groundwater is strongly compartmentalized and often overpressured, with permeability of 10−17 to 10−13 m2 and flow occurring primarily through fracture and crush zones, hindered by shears containing clayey gouge. Hydrological monitoring recorded earthquake-induced meter- or centimeter-scale changes in groundwater levels (at 22 piezometers) and elevated drainage discharge (at 11 V notch weirs). Groundwater level changes exhibited consistent characteristics at all monitoring sites, with time to peak-pressure changes taking ~1 month and recovery lasting 0.7–1.2 years. Changes in weir flow rate near instantaneous (peaking 0–6 h after earthquakes) and followed by recession lasting ~1 month. Responses at each site were systematic from one earthquake to another in terms of duration, polarity, and amplitude. Consistent patterns in amplitude and duration have been compared between sites and with earthquake parameters (peak ground acceleration (PGA), seismic energy density (e), shaking duration, frequency bandwidth, and site amplitude). Shaking at PGA ~0.27% g and e ~ 0.21 J m−3 induced discernable gorge-wide hydrological responses at thresholds comparable to other international examples. Groundwater level changes modeled using a damped harmonic oscillator characterize the ability of the system to resist and recover from extrinsic perturbations. The observed character of response reflects spectral characteristics as well as energy. Landslide hydrological systems appear most susceptible to damage and hydraulic changes when earthquakes emit broad-frequency, long-duration, high-amplitude ground motion.

Multiphase Flow Induced Vibrations at High Pressure: CFD Analysis of Multiphase Forces

2021 ◽  
Author(s):  
Paul Emmerson ◽  
Mike Lewis ◽  
Neil Barton ◽  
Steinar Orre ◽  
Knud Lunde ◽  
...  
Keyword(s):  
High Pressure ◽  
Multiphase Flow ◽  
Gas Flow ◽  
Production Systems ◽  
Pressure Fluctuations ◽  
High Amplitude ◽  
Operating Pressure ◽  
Cfd Analysis ◽  
Cfd Modelling ◽  
Test Loop

Abstract CFD analysis of a high pressure 2” pipe test loop with water-gas flow was undertaken using three different solvers. Multiphase flow induced forces were predicted on the bends at a range of operating pressures between 10 and 80 barg and compared with forces reconstructed from vibration measurements. Overall the three different CFD solvers predicted consistent results. The fluid forces predicted on the bends of the double U-loop test rig have a good range of values compared to the test reconstructed forces. The forces predicted at low pressure were in line with the experimental reconstructed values, whilst at high pressure all three CFD solvers predicted higher forces. The trend of the forces reducing with increased operating pressure, evident in test, was matched by one of the CFD methods, but less well by the other two. At low operating pressure the forces are dominated by the momentum of the liquid in the multiphase flow, whilst at high pressure the pressure fluctuations and turbulent effects will be more important. All three CFD solvers use VOF methods and above about 40 barg it is possible that they struggle to fully resolve the flow behaviour, which will be more influenced by bubble and droplet entrainment and turbulence. Multiphase flow can induce high amplitude vibrations in piping systems, potentially leading to fatigue failures. CFD modelling offers a potentially powerful tool to provide the flow induced forces required for assessing and diagnosing multiphase flow induced pipework vibration problems in hydrocarbon production systems.

Singing Mitigation in an Export Riser via Liquid Injection: A Field Case Study

2014 ◽  
Author(s):  
S. P. C. Belfroid ◽  
H. J. C. Korst ◽  
P. van Beek ◽  
K. Lunde ◽  
I. G. Eidsvik ◽  
...  
Keyword(s):  
Gas Flow ◽  
Field Measurements ◽  
High Amplitude ◽  
Injection Rate ◽  
Norwegian Sea ◽  
Liquid Injection ◽  
Flexible Jumper ◽  
Continuous Injection ◽  
Gas Lift

Flexible Risers are prone to the generation of high amplitude tonal noise, i.e. a so-called singing riser. Recently, severe vibrations and high noise levels were encountered on the turret of an FPSO in the Norwegian Sea, resulting in significantly reduced production. The vibrations could be attributed to pulsations generated either by a flexible jumper (connecting topside to turret), the gas lift riser or the gas export riser. Field measurements showed that the most likely source was the 10 inch gas export riser. Due to the vibrations, a reduced production limit was set. A field measurement campaign was started to inject liquid into the export risers to provisionally increase production, while in the meantime permanent solutions were evaluated and installed. Liquid was injected batch wise and continuously. The main field trial was initiated by a batch of MEG (mono ethylene glycol) (2 times 500 liters) followed by continuous injection of small amounts of MEG. Between settling periods, the gas export rate was increased in steps until vibrations were detected. At detection, the MEG injection rate was increased until vibrations/pulsations disappeared, after which gas export was increased again. This process was repeated to maximum gas flow rate, after which the liquid injection and gas export were similarly stepwise decreased. During this test, the gas export could be increased tenfold with moderate liquid injection rates (up to a maximum of 25 l/hr). Similar tests were done with TEG as injected fluid. However, TEG was far less efficient in suppressing the singing. This is attributed to the higher viscosity of the TEG at the injection temperatures and the method of injection.

Seismoacoustic analysis of underground explosions using the Rayleigh integral

2020 ◽  
Vol 223 (2) ◽  
pp. 1069-1085 ◽  
Author(s):  
Philip Blom ◽  
Alex Iezzi ◽  
Garrett Euler
Keyword(s):  
Ground Motion ◽  
Acoustic Signal ◽  
Low Frequency ◽  
Free Fall ◽  
Acoustic Signals ◽  
Frequency Component ◽  
Underground Explosion ◽  
Ground Zero ◽  
Surface Motion ◽  
Explosion Monitoring

SUMMARY A coupled seismoacoustic model is developed for the analysis of acoustic signals produced by underground explosive events with an aim to develop a means of improving estimated depth and yield for explosion monitoring. A ground spall model is used to predict surface motion characteristics produced by an underground explosion and the Rayleigh integral is applied to relate the surface motion to the acoustic signal some distance from surface ground zero. The low-frequency component of the ground motion associated with the prolonged free fall of lofted material during spall is found to dominate the acoustic signal propagating away from surface ground zero at shallow angles. The model is applied to observed ground motion and acoustic signals recorded during the Source Physics Experiment (SPE) with promising results. In addition to accurately predicting characteristics of the observed acoustic signals from several of the SPE events, the model provides a means of explaining the lack of signals observed during several events in the SPE due to the directionality of the higher frequency acoustic signals associated with the uplift and closure components as well as the lack of a spatially localized, longer duration dwell.

From Rotating Stall to Surge: A Shock Tube Mechanism

2013 ◽  
Author(s):  
Paul Xiubao Huang ◽  
JianAn Yin
Keyword(s):  
Shock Tube ◽  
Gas Flow ◽  
Pressure Ratio ◽  
Low Frequency ◽  
Physical Nature ◽  
High Amplitude ◽  
Rotating Stall ◽  
Jet Engine ◽  
Dynamic Type ◽  
Compressor Surge

Compressor surge is a complete breakdown in compression resulting in an abrupt momentary reversal of gas flow and the violent pressure fluctuation with relatively low frequency and high amplitude. It commonly exists in dynamic type turbo compressors, particularly axial compressor and jet engine, or turbo charger for reciprocating engines. It is generally accepted that surge is preceded by a rotating stall, a situation of a few stalled blades rotating around compressor annulus (cascade) with much higher frequency. In jet engine, violent surge event typically produces a frightening loud bang, lots of vibrations and could cause catastrophic structural failures if not timely managed. Naturally, as important matters as rotating stall and surge, there have been tremendous R/D efforts from academia, government and industry devoted to this area, especially since jet engines became the prime powerhouses for modern airplanes. Despite of all the efforts, there still seems to be a more urgent need to understand the physical characteristics of the transition from a rotating stall to surge that has mystified researchers due to its transient nature. Fundamental questions remain unanswered even today, such as: What exactly triggers the surge to take place from a rotating stall? What is the physical nature of a compressor system or a local incipient surge: is it a movement of wave or fluid particles or both? How to estimate the quantitative destructive forces of a severe surge, that is, the maximum possible surge strength? This paper attempts to answer these questions by applying the classical Shock Tube Theory to the transient process from rotating stall to surge. The Shock Tube analogy is established with the hypothesis (implied from experimental observations) that an instant zero through flow condition exists inside a stalled cascade cell or dynamic compressor that triggers surge. It is revealed that surge event consists of a pair of non-linear compression and expansion waves (CW & EW) that instantly reverse gas flow (IRFF) by the pushing force of upstream propagating CW and the pulling force from downstream travelling EW. The surge strength is shown to be proportional to the square root of the pressure ratio of the involved cascade or compressor. Surge Rules are deduced to predict the location of surge initiation, the minimum and maximum surge strengths, travelling directions and speed. Moreover, a pro-active control strategy called SEWI (Surge Early Warning Initiative) is proposed using the unique characteristics of CW-IRFF-EW formation of a cascade cell induced surge as precursors for subsequent warning and controls before the destructive compressor surge takes place.

scholarly journals Effect of Strain Measurement Layout on Damage Detection and Localization in a Free Falling Compliant Cylinder Impacting a Water Surface

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 58
Author(s):  
Alessandro Mercuri ◽  
Pierluigi Fanelli ◽  
Stefano Ubertini ◽  
Giacomo Falcucci ◽  
Elio Jannelli ◽  
...  
Keyword(s):  
Damage Detection ◽  
Free Fall ◽  
Experimental Tests ◽  
High Amplitude ◽  
Impulsive Loading ◽  
Sensor Arrangement ◽  
The Difference ◽  
Impact Problems ◽  
Free Falling ◽  
Detection And Localization

The need for effective and reliable damage detection and localization systems is growing in several engineering fields, in particular in water impact problems characterized by impulsive loading conditions, high amplitude vibrations and large local deformations. In this paper, we further develop the approach presented in previous works to detect damage of water-impacting structures. Specifically, we provide a set of experimental tests on a flexible plastic cylinder impacting the water after a 50 cm free fall. The cylindrical specimen is artificially damaged in a known position. Strain measurements are performed through a set of nine fiber Bragg gratings distributed along the circumference of a cylinder section. We show that strain sensors can be used as reference sensors, for structure displacements reconstruction, and control sensors, for damage detection purposes, and the computation of the difference between measured and expected deformation may allow damage detection. Moreover, we investigate how exchanging control and reference sensors in the same sensor arrangement affect damage detection and localization.

scholarly journals SEISMIC DAMAGE ASSESSMENT OF LIFELINES BASED ON GEOSPATIAL ANALYSIS

2019 ◽  
Vol XLII-4/W16 ◽  
pp. 197-203
Author(s):  
M. Eskandari ◽  
S. Goodarzi ◽  
M. A. Nekooie
Keyword(s):  
Damage Assessment ◽  
Hazard Analysis ◽  
Seismic Damage ◽  
Geospatial Information ◽  
Ground Acceleration ◽  
Ground Shaking ◽  
Ground Failure ◽  
Damage Probability ◽  
Seismic Damage Assessment ◽  
Database Implementation

Abstract. The main purpose of this study is to develop a Geospatial Information System (GIS) model with the ability to assess the seismic damage to lifelines for two well-known hazards, including ground shaking and ground failure simultaneously. The model that is developed and used in this study includes four main parts of database implementation, seismic hazard analysis, vulnerability assessment and seismic damage assessment to determine the lifeline’s damage probability. To consider uncertainty analysis in the model, Monte Carlo simulation is used based on 10,000 iterations. The results of hazard analysis indicated that peak ground acceleration is about 0.03 g to 0.3 g and there is slight to moderate damages to the desired infrastructure in the study area.

Sign in / Sign up

Export Citation Format

Share Document