scholarly journals Tracking deep-sea internal wave propagation with a differential pressure gauge array

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chu-Fang Yang ◽  
Wu-Cheng Chi ◽  
Hans van Haren ◽  
Ching-Ren Lin ◽  
Ban-Yuan Kuo
Keyword(s):  
Wave Propagation ◽  
Internal Wave ◽  
Pressure Gauge ◽  
Thermal Relaxation ◽  
Deep Ocean ◽  
Differential Pressure ◽  
Propagation Time ◽  
Ocean Bottom ◽  
Internal Motions ◽  
The Impact

AbstractTemperature is used to trace ocean density variations, and reveals internal waves and turbulent motions in the deep ocean, called ‘internal motions.’ Ambient temperature detected by geophysical differential pressure gauges (DPGs) may provide year-long, complementary observations. Here, we use data from four DPGs fixed on the ocean bottom and a high-resolution temperature sensor (T-sensor) 13 m above the seafloor as a square-kilometer array deployed offshore ~ 50 km east of Taiwan facing the open Pacific Ocean to examine the impact of temperature on DPG signals related to internal motions. The DPG signals correlate with T-sensor temperature variations between 0.002 and 0.1 mHz, but have time shifts partially caused by slow thermal conduction from the ambient seafloor to the DPG chamber and partially by internal motion propagation time across the array. Applying beamforming-frequency-wavenumber analysis and linear regression to the arrayed T-sensor and DPG data, we estimate the propagating slowness of the internal motions to be between 0.5 and 7.4 s m−1 from the northwest and northeast quadrants of the array. The thermal relaxation time of the DPGs is within 103–104 s. This work shows that a systematic scan of DPG data at frequencies < 0.1 mHz may help shed light on patterns of internal wave propagation in the deep ocean, especially in multi-scale arrays.

In-Situ Calibration of Differential Pressure Gauges on OBSIP Ocean Bottom Seismometers

2020 ◽  
Author(s):  
Gabi Laske ◽  
Adrian Doran
Keyword(s):  
Pressure Sensor ◽  
Broad Band ◽  
Pressure Gauge ◽  
Differential Pressure ◽  
P Wave ◽  
Earth Tides ◽  
Release Mechanism ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer

&lt;p&gt;A standard ocean bottom seismometer (OBS) package of the U.S. OBS Instrument Pool (OBSIP) carries a seismometer and a pressure sensor. For broadband applications, the seismometer typically is a wide-band or broad-band three-components seismometer, and the pressure sensor is a differential pressure gauge (DPG). The purpose of the pressure sensor is manifold and includes the capture of pressure signals not picked up by a ground motion sensor (e.g. the passage of tsunami), but also for purposes of correcting the seismograms for unwanted signals generated in the water column (e.g. p-wave reverberations).&lt;br&gt;Unfortunately, the instrument response of the widely used Cox-Webb DPG remains somewhat poorly known, and can vary by individual sensor, and even by deployment of the same sensor.&lt;/p&gt;&lt;p&gt;Efforts have been under way to construct and test DPG responses in the laboratory. But the sensitivity and long&amp;#8208;period response are difficult to calibrate as they &amp;#160;vary with temperature and pressure, and perhaps by hardware of the same mechanical specifications. &amp;#160;Here, we present a way to test the response for each individual sensor and deployment in situ in the ocean. This test requires a relatively minimal and inexpensive modification to the OBS instrument frame and a release mechanism that allows a drop of the DPG by 3 inches after the OBS package settled and the DPG equilibrated on the seafloor. The seismic signal generated by this drop is then analyzed in the laboratory upon retrieval of the data.&amp;#160;&lt;/p&gt;&lt;p&gt;The results compare favorably with calibrations estimated independently through post&amp;#8208;deployment data analyses of other signals such as Earth tides and the signals from large teleseismic earthquakes. Our study demonstrates that observed response functions can deviate from the nominal response by a factor of two or greater with regards to both the sensitivity and the time constant. Given the fact that sensor calibrations of DPGs in the lab require very specific and stable environments and are time consuming, the use of in-situ DPG calibration frames pose a reliable and inexpensive alternative.&amp;#160;&lt;/p&gt;

scholarly journals Mountain-Wave Propagation under Transient Tropospheric Forcing: A DEEPWAVE Case Study

2018 ◽  
Vol 146 (6) ◽  
pp. 1861-1888 ◽  
Author(s):  
Tanja C. Portele ◽  
Andreas Dörnbrack ◽  
Johannes S. Wagner ◽  
Sonja Gisinger ◽  
Benedikt Ehard ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Wave Attenuation ◽  
Small Scale ◽  
Propagation Time ◽  
Mountain Range ◽  
Mountain Wave ◽  
Low Level ◽  
Momentum Fluxes ◽  
The Impact

The impact of transient tropospheric forcing on the deep vertical mountain-wave propagation is investigated by a unique combination of in situ and remote sensing observations and numerical modeling. The temporal evolution of the upstream low-level wind follows approximately a [Formula: see text] shape and was controlled by a migrating trough and connected fronts. Our case study reveals the importance of the time-varying propagation conditions in the upper troposphere and lower stratosphere (UTLS). Upper-tropospheric stability, the wind profile, and the tropopause strength affected the observed and simulated wave response in the UTLS. Leg-integrated along-track momentum fluxes ([Formula: see text]) and amplitudes of vertical displacements of air parcels in the UTLS reached up to 130 kN m−1 and 1500 m, respectively. Their maxima were phase shifted to the maximum low-level forcing by ≈8 h. Small-scale waves ([Formula: see text] km) were continuously forced, and their flux values depended on wave attenuation by breaking and reflection in the UTLS region. Only maximum flow over the envelope of the mountain range favored the excitation of longer waves that propagated deeply into the mesosphere. Their long propagation time caused a retarded enhancement of observed mesospheric gravity wave activity about 12–15 h after their observation in the UTLS. For the UTLS, we further compared observed and simulated [Formula: see text] with fluxes of 2D quasi-steady runs. UTLS momentum fluxes seem to be reproducible by individual quasi-steady 2D runs, except for the flux enhancement during the early decelerating forcing phase.

The impact of multiple layering on internal wave transmission

2016 ◽  
Vol 789 ◽  
pp. 617-629 ◽  
Author(s):  
S. J. Ghaemsaidi ◽  
H. V. Dosser ◽  
L. Rainville ◽  
T. Peacock
Keyword(s):  
Experimental Study ◽  
Wave Propagation ◽  
Internal Wave ◽  
Arctic Ocean ◽  
The Arctic ◽  
Simplified Model ◽  
The Arctic Ocean ◽  
The Impact ◽  
Double Diffusive

Given the ubiquity of layering in environmental stratifications, an interesting example being double-diffusive staircase structures in the Arctic Ocean, we present the results of a joint theoretical and laboratory experimental study investigating the impact of multiple layering on internal wave propagation. We first present results for a simplified model that demonstrates the non-trivial impact of multiple layering. Thereafter, utilizing a weakly viscous linear model that can handle arbitrary vertical stratifications, we perform a comparison of theory with experiments. We conclude by applying this model to a case study of a staircase stratification profile obtained from the Arctic Ocean, finding a rich landscape of transmission behaviour.

PROPAGATION OF THE BURNING WAVE IN A PULSED DETONATION COMBUSTOR OPERATING ON MIXTURES OF HEPTANE AND JET A-1 WITH AIR AND OXYGEN AT [O2/AIR] < 1

2020 ◽  
Author(s):  
M. S. ASSAD ◽  
◽  
O. G. PENYAZKOV ◽  
I. I. CHERNUHO ◽  
K. ALHUSSAN ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Combustion Wave ◽  
Equivalence Ratio ◽  
Pressure Sensors ◽  
Jet Fuel ◽  
Propagation Time ◽  
Burning Wave ◽  
Pulsed Detonation ◽  
Combustion Wave Propagation ◽  
Fuel Jet

This work is devoted to the study of the dynamics of combustion wave propagation in oxygen-enriched mixtures of n-heptane with air and jet fuel "Jet A-1" in a small-size pulsed detonation combustor (PDC) with a diameter of 20 mm and a length less than 1 m. Experiments are carried out after the PDC reaches a stationary thermal regime when changing the equivalence ratio (ϕ = 0.73-1.89) and the oxygen-to-air ratio ([O2/air] = 0.15-0.60). The velocity of the combustion wave is determined by measuring the propagation time of the flame front between adjacent pressure sensors that form measurement segements along the PDC.

On the impact of sea ice in a global ocean circulation model

1997 ◽  
Vol 25 ◽  
pp. 111-115 ◽  
Author(s):  
Achim Stössel
Keyword(s):  
Southern Ocean ◽  
Sea Ice ◽  
Ocean Circulation ◽  
General Circulation ◽  
Thermohaline Circulation ◽  
Circulation Model ◽  
Deep Ocean ◽  
Global Ocean ◽  
Convective Activity ◽  
The Impact

This paper investigates the long-term impact of sea ice on global climate using a global sea-ice–ocean general circulation model (OGCM). The sea-ice component involves state-of-the-art dynamics; the ocean component consists of a 3.5° × 3.5° × 11 layer primitive-equation model. Depending on the physical description of sea ice, significant changes are detected in the convective activity, in the hydrographic properties and in the thermohaline circulation of the ocean model. Most of these changes originate in the Southern Ocean, emphasizing the crucial role of sea ice in this marginally stably stratified region of the world's oceans. Specifically, if the effect of brine release is neglected, the deep layers of the Southern Ocean warm up considerably; this is associated with a weakening of the Southern Hemisphere overturning cell. The removal of the commonly used “salinity enhancement” leads to a similar effect. The deep-ocean salinity is almost unaffected in both experiments. Introducing explicit new-ice thickness growth in partially ice-covered gridcells leads to a substantial increase in convective activity, especially in the Southern Ocean, with a concomitant significant cooling and salinification of the deep ocean. Possible mechanisms for the resulting interactions between sea-ice processes and deep-ocean characteristics are suggested.

Influence of the applied pressure of the transducer on the propagation speed of the ultrasonic wave in wood

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Edgar V.M. Carrasco ◽  
Rejane C. Alves ◽  
Mônica A. Smits ◽  
Vinnicius D. Pizzol ◽  
Ana Lucia C. Oliveira ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Applied Pressure ◽  
Pressure Gauge ◽  
Eucalyptus Grandis ◽  
Propagation Speed ◽  
Ultrasonic Waves ◽  
Ultrasonic Speed ◽  
Wave Propagation Speed ◽  
Propagation Technique ◽  
Non Destructive

Abstract The non-destructive wave propagation technique is used to estimate the wood’s modulus of elasticity. The propagation speed of ultrasonic waves is influenced by some factors, among them: the type of transducer used in the test, the form of coupling and the sensitivity of the transducers. The objective of the study was to evaluate the influence of the contact pressure of the transducers on the ultrasonic speed. Ninety-eight tests were carried out on specimens of the species Eucalyptus grandis, with dimensions of 120 × 120 × 50 mm. The calibration of the pressure exerted by the transducer was controlled by a pressure gauge using a previously calibrated load cell. The robust statistical analysis allowed to validate the experimental results and to obtain consistent conclusions. The results showed that the wave propagation speed is not influenced by the pressure exerted by the transducer.

scholarly journals From Loschmidt daemons to time-reversed waves

2016 ◽  
Vol 374 (2069) ◽  
pp. 20150156 ◽  
Author(s):  
Mathias Fink
Keyword(s):  
Wave Propagation ◽  
Time Reversal ◽  
Degrees Of Freedom ◽  
Point Of View ◽  
Propagation Time ◽  
Reversal Invariance ◽  
Spatial Boundary ◽  
Dual Approaches ◽  
Spatio Temporal

Time-reversal invariance can be exploited in wave physics to control wave propagation in complex media. Because time and space play a similar role in wave propagation, time-reversed waves can be obtained by manipulating spatial boundaries or by manipulating time boundaries. The two dual approaches will be discussed in this paper. The first approach uses ‘time-reversal mirrors’ with a wave manipulation along a spatial boundary sampled by a finite number of antennas. Related to this method, the role of the spatio-temporal degrees of freedom of the wavefield will be emphasized. In a second approach, waves are manipulated from a time boundary and we show that ‘instantaneous time mirrors’, mimicking the Loschmidt point of view, simultaneously acting in the entire space at once can also radiate time-reversed waves.

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