Oceanic Isopycnal Slope Spectra. Part II: Turbulence

2007 ◽  
Vol 37 (5) ◽  
pp. 1232-1245 ◽  
Author(s):  
Jody M. Klymak ◽  
James N. Moum
Keyword(s):  
Fine Structure ◽  
Linear Combination ◽  
Internal Waves ◽  
Dissipation Rate ◽  
Spectral Amplitude ◽  
Vertical Profiles ◽  
Broad Bandwidth ◽  
Magnitude Range ◽  
Dissipation Rates ◽  
Order Of Magnitude

Abstract Isopycnal slope spectra were computed from thermistor data obtained using a microstructure platform towed through turbulence generated by internal tidal motions near the Hawaiian Ridge. The spectra were compared with turbulence dissipation rates ɛ that are estimated using shear probes. The turbulence subrange of isopycnal slope spectra extends to surprisingly large horizontal wavelengths (>100 m). A four-order-of-magnitude range in turbulence dissipation rates at this site reveals that isopycnal slope spectra ∝ ɛ2/3k1/3x. The turbulence spectral subrange (kx > 0.4 cpm) responds to the dissipation rate as predicted by the Batchelor model spectrum, both in amplitude and towed vertical coherence. Scales between 100 and 1000 m are modeled by a linear combination of internal waves and turbulence while at larger scales internal waves dominate. The broad bandwidth of the turbulence subrange means that a fit of spectral amplitude to the Batchelor model yields reasonable estimates of ɛ, even when applied at scales of tens of meters that in vertical profiles would be obscured by other fine structure.

Oceanic Isopycnal Slope Spectra. Part I: Internal Waves

2007 ◽  
Vol 37 (5) ◽  
pp. 1215-1231 ◽  
Author(s):  
Jody M. Klymak ◽  
James N. Moum
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Vertical Profile ◽  
Dissipation Rate ◽  
Wave Spectra ◽  
The Poor ◽  
Order Of Magnitude

Abstract Horizontal tow measurements of internal waves are rare and have been largely supplanted in recent decades by vertical profile measurements. Here, estimates of isotherm displacements and turbulence dissipation rate from a towed vehicle deployed near Hawaii are presented. The displacement data are interpreted in terms of horizontal wavenumber spectra of isopycnal slope. The spectra span scales from 5 km to 0.1 m, encompassing both internal waves and turbulence. The turbulence subrange is identified using a standard turbulence fit, and the rest of the motions are deemed to be internal waves. The remaining subrange has a slightly red slope (ϕ ∼ k−1/2x) and vertical coherences compatible with internal waves, in agreement with previous towed measurements. However, spectral amplitudes in the internal wave subrange exhibit surprisingly little variation despite a four-order-of-magnitude change in turbulence dissipation rate observed at the site. The shape and amplitude of the horizontal spectra are shown to be consistent with observations and models of vertical internal wave spectra that consist of two subranges: a “linear” subrange (ϕ ∼ k0z) and a red “saturated” subrange (ϕ ∼ k−1z). These two subranges are blurred in the transformation to horizontal spectra, yielding slopes close to those observed. The saturated subrange does not admit amplitude variations in the spectra yet is an important component of the measured horizontal spectra, explaining the poor correspondence with the dissipation rate.

scholarly journals Variability of the Turbulent Kinetic Energy Dissipation along the A25 Greenland–Portugal Transect Repeated from 2002 to 2012

2016 ◽  
Vol 46 (7) ◽  
pp. 1989-2003 ◽  
Author(s):  
Bruno Ferron ◽  
Florian Kokoszka ◽  
Herlé Mercier ◽  
Pascale Lherminier ◽  
Thierry Huck ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Internal Waves ◽  
Dissipation Rate ◽  
Internal Tide ◽  
Velocity Shear ◽  
Reykjanes Ridge ◽  
Continental Slopes ◽  
Order Of Magnitude

AbstractThe variability of the turbulent kinetic energy dissipation due to internal waves is quantified using a finescale parameterization applied to the A25 Greenland–Portugal transect repeated every two years from 2002 to 2012. The internal wave velocity shear and strain are estimated for each cruise at 91 stations from full depth vertical profiles of density and velocity. The 2002–12 averaged dissipation rate 〈ε2002–2012〉 in the upper ocean lays in the range 1–10 × 10−10 W kg−1. At depth, 〈ε2002–2012〉 is smaller than 1 × 10−10 W kg−1 except over rough topography found at the continental slopes, the Reykjanes Ridge, and in a region delimited by the Azores–Biscay Rise and Eriador Seamount. There, the vertical energy flux of internal waves is preferentially oriented toward the surface and 〈ε2002–2012〉 is in the range 1–20 × 10−10 W kg−1. The interannual variability in the dissipation rates is remarkably small over the whole transect. A few strong dissipation rate events exceeding the uncertainty of the finescale parameterization occur at depth between the Azores–Biscay Rise and Eriador Seamount. This region is also marked by mesoscale eddying flows resulting in enhanced surface energy level and enhanced bottom velocities. Estimates of the vertical energy fluxes into the internal tide and into topographic internal waves suggest that the latter are responsible for the strong dissipation events. At Eriador Seamount, both topographic internal waves and the internal tide contribute with the same order of magnitude to the dissipation rate while around the Reykjanes Ridge the internal tide provides the bulk of the dissipation rate.

Generation of vertical fine structure in inhomogeneous flow by inertial-gravity internal waves

1993 ◽  
Vol 4 (4) ◽  
pp. 307-315
Author(s):  
A. A. Belobrov ◽  
A. A. Slepyshev ◽  
V. S. Shamov
Keyword(s):  
Fine Structure ◽  
Internal Waves ◽  
Inhomogeneous Flow

scholarly journals Estimation of the Turbulent Fraction in the Free Atmosphere from MST Radar Measurements

2005 ◽  
Vol 22 (9) ◽  
pp. 1326-1339 ◽  
Author(s):  
Richard Wilson ◽  
Francis Dalaudier ◽  
Francois Bertin
Keyword(s):  
Dissipation Rate ◽  
Spectral Width ◽  
Unbiased Estimation ◽  
Small Scale ◽  
Doppler Width ◽  
Free Atmosphere ◽  
Dissipation Rates ◽  
Sampling Volume ◽  
Radar Measurements ◽  
Width Measurements

Abstract Small-scale turbulence in the free atmosphere is known to be intermittent in space and time. The turbulence fraction of the atmosphere is a key parameter in order to evaluate the transport properties of small-scale motions and to interpret clear-air radar measurements as well. Mesosphere–stratosphere–troposphere (MST)/stratosphere–troposphere (ST) radars provide two independent methods for the estimation of energetic parameters of turbulence. First, the Doppler spectral width σ2 is related to the dissipation rate of kinetic energy εk. Second, the radar reflectivity, or C2n, relates to the dissipation rate of available potential energy εp. However, these two measures yield estimates that differ with respect to an important point. The Doppler width measurements, and related εk, are reflectivity-weighted averages. On the other hand, the reflectivity estimate is a volume-averaged quantity. The values of εp depend on both the turbulence intensity and the turbulent fraction within the radar sampling volume. Now, the two dissipation rates εp and εk are related quantities as shown by various measurements within stratified fluids (atmosphere, ocean, lakes, or laboratory). Therefore, by assuming a “canonical” value for the ratio of dissipation rates, an indirect method is proposed to infer the turbulent fraction from simultaneous radar measurements of reflectivity and Doppler broadening within a sampling volume. This method is checked by using very high resolution radar measurements (30 m and 51 s), obtained by the PROUST radar during a field campaign. The method is found to provide an unbiased estimation of the turbulent fraction, within a factor of 2 or less.

scholarly journals Aspiration-assisted bioprinting for precise positioning of biologics

2020 ◽  
Vol 6 (10) ◽  
pp. eaaw5111 ◽  
Author(s):  
Bugra Ayan ◽  
Dong Nyoung Heo ◽  
Zhifeng Zhang ◽  
Madhuri Dey ◽  
Adomas Povilianskas ◽  
...  
Keyword(s):  
Self Assembly ◽  
Physical Mechanism ◽  
Single Cells ◽  
Three Dimensional ◽  
3D Bioprinting ◽  
Precise Control ◽  
3D Space ◽  
Magnitude Range ◽  
Wide Range ◽  
Order Of Magnitude

Three-dimensional (3D) bioprinting is an appealing approach for building tissues; however, bioprinting of mini-tissue blocks (i.e., spheroids) with precise control on their positioning in 3D space has been a major obstacle. Here, we unveil “aspiration-assisted bioprinting (AAB),” which enables picking and bioprinting biologics in 3D through harnessing the power of aspiration forces, and when coupled with microvalve bioprinting, it facilitated different biofabrication schemes including scaffold-based or scaffold-free bioprinting at an unprecedented placement precision, ~11% with respect to the spheroid size. We studied the underlying physical mechanism of AAB to understand interactions between aspirated viscoelastic spheroids and physical governing forces during aspiration and bioprinting. We bioprinted a wide range of biologics with dimensions in an order-of-magnitude range including tissue spheroids (80 to 600 μm), tissue strands (~800 μm), or single cells (electrocytes, ~400 μm), and as applications, we illustrated the patterning of angiogenic sprouting spheroids and self-assembly of osteogenic spheroids.

scholarly journals The σ Problem of the Crab Pulsar Wind

2004 ◽  
Vol 218 ◽  
pp. 171-174
Author(s):  
J. G. Kirk ◽  
O. Skjæraasen
Keyword(s):  
Dissipation Rate ◽  
A Priori ◽  
Termination Shock ◽  
Crab Pulsar ◽  
Complete Conversion ◽  
Poynting Flux ◽  
Dissipation Rates ◽  
Pulsar Wind

The conversion of the Crab pulsar wind from one dominated by Poynting flux close to the star to one dominated by particle-borne energy at the termination shock is considered. The idea put forth by Coroniti (1990) and criticized by Lyubarsky & Kirk (2001) that reconnection in a striped wind is responsible, is generalized to include faster prescriptions for the a priori unknown dissipation rate. Strong acceleration of the wind is confirmed, and the higher dissipation rates imply complete conversion of Poynting flux into particle-borne flux within the unshocked wind.

Locally Available Aggregate and Sediment Production

2003 ◽  
Vol 1819 (1) ◽  
pp. 185-193 ◽  
Author(s):  
Randy B. Foltz ◽  
Mark Truebe
Keyword(s):  
Road Construction ◽  
Forest Road ◽  
Sediment Production ◽  
Magnitude Range ◽  
Long Duration ◽  
Order Of Magnitude ◽  
Equivalent Test ◽  
Basic Characteristics ◽  
Material Tests ◽  
Selection Of

Selection of suitable locally available materials to build strong and durable roads with aggregate surfaces is desired to minimize road construction and maintenance costs and to minimize the detrimental effects of sedimentation. Eighteen aggregates were selected from local sources in Idaho, Oregon, South Dakota, and Washington State. Aggregate was placed in shallow metal frames and compacted to simulate a forest road. The levels of runoff and sediment from a highintensity, long-duration simulated rainstorm were measured. The material tests selected for use in the study included ones that define the basic characteristics of the aggregate, along with a number of tests intended to predict susceptibility to erosion. Each of the tests was statistically evaluated to identify those that best predicted the perceived aggregate quality. The two best indicators of aggregate quality were the results of the sand equivalent test and the P20 portion of the Oregon air degradation test. The best indicator of either runoff or sediment production was the fraction passing the 0.6-mm sieve. Acceptable aggregates, both those of good quality and those of marginal quality, exhibited a 2-order-of-magnitude range in both runoff and sediment production.

scholarly journals Observations of Breaking Waves and Energy Dissipation in Modulated Wave Groups

2018 ◽  
Vol 48 (12) ◽  
pp. 2937-2948 ◽  
Author(s):  
David W. Wang ◽  
Hemantha W. Wijesekera
Keyword(s):  
Energy Dissipation ◽  
Wave Height ◽  
Wave Breaking ◽  
Dissipation Rate ◽  
Breaking Waves ◽  
Wave Groups ◽  
Dissipation Rates ◽  
Local Wave ◽  
Tke Dissipation Rate ◽  
The Impact

AbstractIt has been recognized that modulated wave groups trigger wave breaking and generate energy dissipation events on the ocean surface. Quantitative examination of wave-breaking events and associated turbulent kinetic energy (TKE) dissipation rates within a modulated wave group in the open ocean is not a trivial task. To address this challenging topic, a set of laboratory experiments was carried out in an outdoor facility, the Oil and Hazardous Material Simulated Environment Test Tank (203 m long, 20 m wide, 3.5 m deep). TKE dissipation rates at multiple depths were estimated directly while moving the sensor platform at a speed of about 0.53 m s−1 toward incoming wave groups generated by the wave maker. The largest TKE dissipation rates and significant whitecaps were found at or near the center of wave groups where steepening waves approached the geometric limit of waves. The TKE dissipation rate was O(10−2) W kg−1 during wave breaking, which is two to three orders of magnitude larger than before and after wave breaking. The enhanced TKE dissipation rate was limited to a layer of half the wave height in depth. Observations indicate that the impact of wave breaking was not significant at depths deeper than one wave height from the surface. The TKE dissipation rate of breaking waves within wave groups can be parameterized by local wave phase speed with a proportionality breaking strength coefficient dependent on local steepness. The characterization of energy dissipation in wave groups from local wave properties will enable a better determination of near-surface TKE dissipation of breaking waves.

scholarly journals X-ray signatures of black hole feedback: hot galactic atmospheres in IllustrisTNG and X-ray observations

2020 ◽  
Vol 494 (1) ◽  
pp. 549-570 ◽  
Author(s):  
Nhut Truong ◽  
Annalisa Pillepich ◽  
Norbert Werner ◽  
Dylan Nelson ◽  
Kiran Lakhchaura ◽  
...  
Keyword(s):  
State Of The Art ◽  
Quenching Mechanism ◽  
Lower Mass ◽  
Cosmological Simulations ◽  
X Ray ◽  
Star Forming ◽  
Magnitude Range ◽  
Order Of Magnitude ◽  
Quenching Mechanisms ◽  
Gaseous Atmospheres

ABSTRACT Hot gaseous atmospheres that permeate galaxies and extend far beyond their stellar distribution, where they are commonly referred to as the circumgalactic medium, imprint important information about feedback processes powered by the stellar populations of galaxies and their central supermassive black holes (SMBHs). In this work, we study the properties of this hot X-ray emitting medium using the IllustrisTNG cosmological simulations. We analyse their mock X-ray spectra, obtained from the diffuse and metal-enriched gas in TNG100 and TNG50, and compare the results with X-ray observations of nearby early-type galaxies. The simulations reproduce the observed X-ray luminosities (LX) and temperature (TX) at small (<Re) and intermediate (<5Re) radii reasonably well. We find that the X-ray properties of lower mass galaxies depend on their star formation rates. In particular, in the magnitude range where the star-forming and quenched populations overlap, $M_{\rm K}\sim -24\ (M_*\sim 10^{10.7}\, \mathrm{M}_\odot)$, we find that the X-ray luminosities of star-forming galaxies are on average about an order of magnitude higher than those of their quenched counterparts. We show that this diversity in LX is a direct manifestation of the quenching mechanism in the simulations, where the galaxies are quenched due to gas expulsion driven by SMBH kinetic feedback. The observed dichotomy in LX is thus an important observable prediction for the SMBH feedback-based quenching mechanisms implemented in state-of-the-art cosmological simulations. While the current X-ray observations of star-forming galaxies are broadly consistent with the predictions of the simulations, the observed samples are small and more decisive tests are expected from the sensitive all-sky X-ray survey with eROSITA.

scholarly journals Gravity Wave–Fine Structure Interactions. Part II: Energy Dissipation Evolutions, Statistics, and Implications

2013 ◽  
Vol 70 (12) ◽  
pp. 3735-3755 ◽  
Author(s):  
David C. Fritts ◽  
Ling Wang
Keyword(s):  
Fine Structure ◽  
Energy Dissipation ◽  
Gravity Wave ◽  
Dissipation Rate ◽  
Companion Paper ◽  
Direct Numerical Simulations ◽  
Thermal Dissipation ◽  
Wave Interactions ◽  
Thermal Energy Dissipation ◽  
Flow Evolution

Abstract Part I of this paper employs four direct numerical simulations (DNSs) to examine the dynamics and energetics of idealized gravity wave–fine structure (GW–FS) interactions. That study and this companion paper were motivated by the ubiquity of multiscale GW–FS superpositions throughout the atmosphere. These DNSs exhibit combinations of wave–wave interactions and local instabilities that depart significantly from those accompanying idealized GWs or mean flows alone, surprising dependence of the flow evolution on the details of the FS, and an interesting additional pathway to instability and turbulence due to GW–FS superpositions. This paper examines the mechanical and thermal energy dissipation rates occurring in two of these DNSs. Findings include 1) dissipation that tends to be much more localized and variable than that due to GW instability in the absence of FS, 2) dissipation statistics indicative of multiple turbulence sources, 3) strong influences of FS shears on instability occurrence and turbulence intensities and statistics, and 4) significant differences between mechanical and thermal dissipation rate fields having potentially important implications for measurements of these flows.

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