Deep Jets Research Articles

Research on the Physical Strength of Surface Conductor Soil Under Deep Jet Drilling

Research on the Physical Strength of Surface Conductor Soil Under Deep Jet Drilling

Factors influencing the meridional width of the equatorial deep jets

Abstract. Equatorial deep jets (EDJs) are vertically alternating, stacked zonal currents that flow along the Equator in all three ocean basins at intermediate depth. Their structure can be described quite well by the sum of high-baroclinic-mode equatorial Kelvin and Rossby waves. However, the EDJ meridional width is larger by a factor of 1.5 than inviscid theory predicts for such waves. Here, we use a set of idealised model configurations representing the Atlantic Ocean to investigate the contributions of different processes to the enhanced EDJ width. Corroborated by the analysis of shipboard velocity sections, we show that widening of the EDJs by momentum loss due to irreversible mixing or other processes contributes more to their enhanced time mean width than averaging over meandering of the jets. Most of the widening due to meandering can be attributed to the strength of intraseasonal variability in the jets' depth range, suggesting that the jets are meridionally advected by intraseasonal waves. A slightly weaker connection to intraseasonal variability is found for the EDJ widening by momentum loss. These results enhance our understanding of the dynamics of the EDJs and, more generally, of equatorial waves in the deep ocean.

The Faroe‐Shetland Channel Jet: Structure, Variability, and Driving Mechanisms

AbstractThe Faroe‐Bank Channel (FBC) is a key gateway through which dense overflow water of the Nordic Seas supplies the lower limb of the Atlantic Meridional Overturning Circulation. Most recently, it was discovered that a deep jet through the Faroe‐Shetland Channel carries the bulk of this overflow water, but numerous questions regarding its structure, seasonality, and interannual variability as well as its linkage to atmospheric forcing remain poorly understood. A realistic high‐resolution ocean reanalysis (GLORYS12; 1993–2018) is, therefore, employed to address these questions. We first confirm that the Faroe‐Shetland Channel Jet is a permanent feature in GLORYS12 as well as in an ensemble of low‐resolution reanalyses. On seasonal time scales, we find a strong transport covariability between this deep jet and the observed FBC overflow. On interannual time scales, the strength of this deep jet is governed by the wind‐forced circulation in the Nordic Seas. Due to the largely barotropic structure of these flows, they have a signature detectable in satellite sea‐surface heights. Further, we suggest that the structure of the deep jet is qualitatively consistent with a geostrophic dynamical model that accounts for along‐isobath density variations. This study indicates that GLORYS12 is a promising product to study the dense water pathways and dynamics in the Nordic Seas.

Destination of New Guinea Coastal Undercurrent in the western tropical Pacific: Variability and linkages

The New Guinea Coastal Undercurrent (NGCUC) is considered a bottleneck in the western tropical Pacific (WTP), carrying upper-to-intermediate waters from the south to the northwestern Pacific, thereby playing a fundamen tal role in the interhemispheric water mass exchange. However, how the NGCUC links to the circulation in the WTP was insufficiently studied. This work explores the destination of NGCUC waters, its spatiotemporal changes, and possible physical processes linked with the downstream NGCUC using ocean reanalysis for 22 years (1994 – 2015). Lagrangian particle tracking discloses eight major destinations of the NGCUC: The Equatorial Undercurrent (EUC, 35.26%), the North Equatorial Countercurrent (NECC, 12.3%), the North (13.33%) and South (8.85%) Subsurface Countercurrents, the Equatorial Deep Jet (11.49%), the Mindanao Undercurrent (13.24%), and the Indonesian (3.47%) and Halmahera (0.86%) Throughflows. The NGCUC waters are distributed mainly to the east (81.65%) and their dissemination varies markedly with depth. These destinations exhibit significant variations on seasonal and interannual time scales. The NGCUC strengthens (weakens) during summer (winter) and more NGCUC waters are distributed westward and northeastward (eastward). Interannually, the distribution of the NGCUC water is influenced by El Niño-Southern Oscillation, in which most of its eastward-distributed waters shift northward (equatorward) in El Niño (La Niña) phase joining the strengthened NECC (EUC). Changes in the NGCUC water destination can transform the water mass properties in the WTP. The findings of this study also emphasize the fundamental role of eddies in trapping and redistributing the NGCUC waters and linking the currents in the WTP.

Rotating horizontal convection with meridional ridges

According to recent studies, the large-scale effect of bottom topography on the ocean overturning circulation can be considered as a result of bottom enhancement of turbulent mixing in the abyssal ocean. Here we show, using laboratory experiments of rotating horizontal convection, that even without spatial variation of mixing intensity, oceanic meridional ridges can strongly impact both the strength and the pattern of the overturning in some fundamental ways. For example, as suggested by experimental results, the existence of the mid-Atlantic ridge can lead to the formation of another deep jet, like the deep western boundary current (DWBC), along the ridge’s eastern edge as a pathway for southward export of newly formed deep water. In response to this interior (mid-basin) jet and the associated isopycnal displacement, adiabatic flow structures may occur in upper and lower layers, including two opposing jets located respectively above and below the interior DWBC. Though unable to contribute to the overturning, they can probably affect transport along isopycnals. In the latitudinal band of the Antarctic Circumpolar Current without side boundary but with multiple ridges lying over the bottom, multiple interior DWBCs may develop preferentially along higher ridges, carrying the Antarctic Bottom Water into the northern latitudes. Moreover, the overturning cell or the strong jets can migrate vertically with the grow or decay of the ridge. Therefore, presumably strong variations of both ocean circulation and stratification may have occurred more than once during the past millions of years, as consequences of plate tectonic evolution, and have caused substantial changes of earth climate.

Atlantic equatorial deep jets in Argo float data

Abstract Equatorial deep jets (EDJ) are zonal currents along the equator in all three ocean basins that alternate in direction with depth and time. In the Atlantic below the thermocline, they are the dominant variability on interannual timescales. Observations of equatorial deep jets are available but scarce, given the EDJs’ location at depth, their small vertical scale and their long periodicity of several years. In the last few years, Argo floats have added a significant amount of measurements at intermediate depth. In this study we therefore revise estimates of the EDJ scales based on Argo float data. Mostly, we use velocity data at 1000 m depth calculated from float displacement, which yield robust estimates of the Atlantic EDJ period (4.6 years), amplitude distribution, phase distribution, zonal wavelength (146.7°), and meridional structure. We also show that the equatorial amplitude of the EDJs’ first meridional mode Rossby wave component (9.8 cm s−1) is larger than that of their Kelvin wave component (2.8 cm s−1). Additionally, we present a new estimation of the EDJs’ vertical structure throughout the Atlantic basin, based on an equatorial geostrophic velocity reconstruction from hydrographic Argo float measurements from depths between 400 and 2000 m. Our new estimates from Argo float data provide the first basin-wide assessment of the Atlantic EDJ scales, as well as having smaller uncertainties than estimates from earlier studies.

Constraints on the Latitudinal Profile of Jupiter's Deep Jets

AbstractThe observed zonal winds at Jupiter's cloud tops have been shown to be closely linked to the asymmetric part of the planet's measured gravity field. Here, we examine to what extent, and at which latitudes, must the flows at depth resemble those at the cloud level to match the gravity signal. We show, using both the symmetric and asymmetric parts of the measured gravity field, that the observed cloud‐level wind profile between 25°S and 25°N must extend unaltered to depths of thousands of kilometers. Poleward, the midlatitude deep jets also contribute to the gravity signal, but might differ somewhat from the cloud‐level winds. We analyze the likelihood of this difference and give bounds to its strength. We also find that to match the gravity measurements, the winds must project inward in the direction parallel to Jupiter's spin axis, and decay inward in the radial direction.

The South Atlantic Meridional Overturning Circulation and Mesoscale Eddies in the First GO‐SHIP Section at 34.5°S

AbstractThe variability of the Atlantic meridional overturning circulation (AMOC) has considerable impacts on the global climate system. Past studies have shown that changes in the South Atlantic control the stability of the AMOC and drive an important part of its variability. That is why significant resources have been invested in a South (S)AMOC observing system. In January 2017, the RV Maria S. Merian conducted the first GO‐SHIP hydrographic transect along the SAMOC‐Basin Wide Array (SAMBA) line at 34.5°S in the South Atlantic. This paper presents estimates of meridional volume, freshwater (MFT), and heat (MHT) transports through the line using the slow varying geostrophic density field and direct velocity observations. An upper and an abyssal overturning cell are identified with a strength of 15.64 ± 1.39 Sv and 2.4 ± 1.6 Sv, respectively. The net northward MHT is 0.27 ± 0.10 PW, increasing by 0.12 PW when we remove the observed mesoscale eddies with a climatology derived from the Argo floats data set. We attribute this change to an anomalous predominance of cold core eddies during the cruise period. The highest velocities are observed in the western boundary, within the Brazil and the Deep Western Boundary currents. These currents appear as a continuous deep jet located 150 km off the slope squeezed between two cyclonic eddies. The zonal changes in water masses properties and velocity denote the imprint of exchange pathways with both the Southern and the Indian oceans.

Simulation study on cutting transport in a horizontal well with hydraulic pulsed jet technology

The hydraulic pulse jet is a high-efficiency drilling technology to improve the efficiency of bottom-hole cuttings removal by enhancing the down-hole flow of cuttings. In this paper, an Eulerian-Eulerian two-fluid model on the basis of the kinetic theory of granular flow is applied to simulate the flow behavior of cuttings and drilling fluid in a horizontal well with hydraulic pulsed jet technology. The influences of pulse jet velocity, amplitude, and frequency on hydrodynamic characteristics are analyzed. Increasing the pulse jet velocity can generate higher pressure and crossflow velocity in the bottom-hole area, quickly carry the cuttings out of the bottom-hole area, and form the cuttings bed near the outlet. The improvement of the amplitude of the pulsed jet can form a remarkable and deep jet penetration in the bottom-hole area, which has a positive effect on the cuttings migration at the bottom-hole area and destruction of the cuttings bed in the annulus. For a given average jet velocity in this paper, the optimal value of amplitude is a half of the average jet velocity. The pulse jet frequency has little effect on cuttings migration in the bottom-hole area, while a higher pulse jet frequency can effectively reduce the height of the cuttings bed in the annulus.

The Range of Jupiter's Flow Structures That Fit the Juno Asymmetric Gravity Measurements

AbstractThe asymmetric gravity field measured by the Juno spacecraft has allowed the estimation of the depth of Jupiter's zonal jets, showing that the winds extend approximately 3,000 km beneath the cloud level. This estimate was based on an analysis using a combination of all measured odd gravity harmonics, J3, J5, J7, and J9, but the wind profile's dependence on each of them separately has yet to be investigated. Furthermore, these calculations assumed the meridional profile of the cloud‐level wind extends to depth. However, it is possible that the interior jet profile varies somewhat from that of the cloud level. Here we analyze in detail the possible meridional and vertical structure of Jupiter's deep jet streams that can match the gravity measurements. We find that each odd gravity harmonic constrains the flow at a different depth, with J3 the most dominant at depths below 3,000 km, J5 the most restrictive overall, whereas J9 does not add any constraint on the flow if the other odd harmonics are considered. Interior flow profiles constructed from perturbations to the cloud‐level winds allow a more extensive range of vertical wind profiles, yet when the meridional profiles differ substantially from the cloud level, the ability to match the gravity data significantly diminishes. Overall, we find that while interior wind profiles that do not resemble the cloud level are possible, they are statistically unlikely. Finally, inspired by the Juno microwave radiometer measurements, assuming the brightness temperature is dominated by the ammonia abundance, we find that depth‐dependent flow profiles are still compatible with the gravity measurements.

Discovery of an unrecognized pathway carrying overflow waters toward the Faroe Bank Channel

The dense overflow waters of the Nordic Seas are an integral link and important diagnostic for the stability of the Atlantic Meridional Overturning Circulation (AMOC). The pathways feeding the overflow remain, however, poorly resolved. Here we use multiple observational platforms and an eddy-resolving ocean model to identify an unrecognized deep flow toward the Faroe Bank Channel. We demonstrate that anticyclonic wind forcing in the Nordic Seas via its regulation of the basin circulation plays a key role in activating an unrecognized overflow path from the Norwegian slope – at which times the overflow is anomalously strong. We further establish that, regardless of upstream pathways, the overflows are mostly carried by a deep jet banked against the eastern slope of the Faroe-Shetland Channel, contrary to previous thinking. This deep flow is thus the primary conduit of overflow water feeding the lower branch of the AMOC via the Faroe Bank Channel.

Equatorial Deep Jets and Their Influence on the Mean Equatorial Circulation in an Idealized Ocean Model Forced by Intraseasonal Momentum Flux Convergence

AbstractEquatorial deep jets (EDJ) are vertically stacked, downward propagating zonal currents that alternate in direction with depth. In the tropical Atlantic, they have been shown to influence both surface conditions and tracer variability. Despite their importance, the EDJ are absent in most ocean models. Here we show that EDJ can be generated in an idealized ocean model when the model is driven only by the convergence of the meridional flux of intraseasonal zonal momentum diagnosed from a companion model run driven by steady wind forcing, corroborating the recent theory that intraseasonal momentum flux convergence maintains the EDJ. Additionally, the EDJ in our model nonlinearly generate mean zonal currents at intermediate depths that show similarities in structure to the observed circulation in the deep equatorial Atlantic, indicating their importance for simulating the tropical ocean mean state.

The influence of deep jets on Jupiter's weather layer in a 1.5‐layer shallow‐water model

AbstractThe depth of the jet streams seen in Jupiter's outer weather layer has long been debated, with alternative suggestions of confinement to the weather layer and extensions deep into the planet being considered. Interpretation of measurements from NASA's Juno probe have suggested that weather‐layer jets do extend deep into the planet, down to depths of (3,000 km). However, this relies on the assumption that the jet profile does not change its spatial structure with depth, which may not be the case. In this work, we consider a simple 1.5‐layer shallow‐water model of Jupiter‐like jet streams, with prescribed deep jets in the lower layer, and look at the parameters affecting the strength of the coupling between the layers. We find the value of the Rossby deformation scale, L D, to be particularly important, not just in setting the magnitude of variations in layer depth, but also in dictating the effectiveness of radiative damping. We also find the radiative damping timescales, the energy injection rate, and the spacing of deep jets to be important. We combine these findings into our best‐guess simulations of the real Jupiter and find that low latitudes are relatively uncoupled between the layers, with high latitudes being more tightly coupled. These effects can be tied to the smallness of Jupiter's L D and the effectiveness of radiative damping as a coupling mechanism. These simulations do, however, produce equatorial subrotation and eddy‐momentum fluxes unlike those on the real planet. It may be, therefore, that spatially varying forcing and very long radiative damping timescales are required for this model to be more Jupiter‐like.

Jupiter-style Jet Stability

Abstract Studies of Jupiter’s zonal jets, facilitated by the two Voyager flybys, the Galileo entry probe, the Cassini flyby, and the Juno orbiter have led to two fundamental insights into inviscid shear stability that have implications for a wide range of large-scale fluid systems involving alternating shear instability. The first insight is that the analog of the Mach number for vorticity (Rossby and drift) waves, “Ma,” ensures shear stability via the criterion “Ma”−1 < 1, which includes both Kelvin–Arnol’d branches of stability, and is edged with a shock. A surprise is the well-studied first branch (KA-I), which includes as special cases the textbook shear stability theorems of Rayleigh, Kuo, Charney–Stern, and Fjørtoft, merely corresponds to “Ma”−1 < 0. The second insight is that Jupiter’s tropospheric jets achieve stability via a second branch (KA-II) strategy, a 3/4 layer, undulating control surface supplied by the dynamic topography of the planet’s deep jets, which maintains “Ma”−1 ≲ 1 via stretching vorticity. The deep jets are similarly stabilized by the spherical shape of the planet itself. Although Jupiter-style zonal jet stabilization is precluded by the torus geometry used in hot-plasma fusion reactors, it is directly applicable to the tube with ends geometry used in cool-plasma applications, including antimatter storage at high-energy colliders. In general, the lessons learned from analyzing Jupiter’s jets eliminate much of the guesswork from predicting and controlling inviscid shear instability.

Offset height effect on turbulent characteristics of twin surface jets

The characteristics of square twin surface jets at various offset heights from the free surface were studied using a particle image velocimetry technique. The offset heights were varied from 1 to 4 nozzle widths at a fixed Reynolds number of 3890. The entrainment and mixing characteristics were examined using the potential core length, merging point, combined point, maximum velocity decay, half-velocity width and were found be nearly independent of offset height in near field. The jet–surface interaction was examined by surface velocity, vorticity thickness and surface turbulence intensities. The growth rate of the vorticity thickness reduced in the interaction region; and was more severe for shorter offset height. Turbulent structures were examined using weighted joint probability density function and two-point cross-correlations between swirling strength and velocity fluctuations. Weaker turbulent events were observed for deeper jet close to a free surface at the streamwise location beyond the attachment point.

Analysis of Jupiter’s Deep Jets Combining Juno Gravity and Time-varying Magnetic Field Measurements

Abstract Jupiter’s internal flow structure is still not fully known, but can be now better constrained due to Juno’s high-precision measurements. The recently published gravity and magnetic field measurements have led to new information regarding the planet and its internal flows, and future magnetic measurements will help to solve this puzzle. In this study, we propose a new method to better constrain Jupiter’s internal flow field using the Juno gravity measurements combined with the expected measurements of magnetic secular variation. Based on a combination of hydrodynamical and magnetic field considerations we show that an optimized vertical profile of the zonal flows that fits both measurements can be obtained. Incorporating the magnetic field effects on the flow better constrains the flow decay profile. This will get us closer to answering the persistent question regarding the depth and nature of the flows on Jupiter.

Vertically Sheared Horizontal Flow-Forming Instability in Stratified Turbulence: Analytical Linear Stability Analysis of Statistical State Dynamics Equilibria

Abstract Vertically banded zonal jets are frequently observed in weakly or nonrotating stratified turbulence, with the quasi-biennial oscillation in the equatorial stratosphere and the ocean’s equatorial deep jets being two examples. Explaining the formation of jets in stratified turbulence is a fundamental problem in geophysical fluid dynamics. Statistical state dynamics (SSD) provides powerful methods for analyzing turbulent systems exhibiting emergent organization, such as banded jets. In SSD, dynamical equations are written directly for the evolution of the turbulence statistics, enabling direct analysis of the statistical interactions between the incoherent component of turbulence and the coherent large-scale structure component that underlie jet formation. A second-order closure of SSD, known as S3T, has previously been applied to show that meridionally banded jets emerge in barotropic β-plane turbulence via a statistical instability referred to as the zonostrophic instability. Two-dimensional Boussinesq turbulence provides a simple model of nonrotating stratified turbulence analogous to the β-plane model of planetary turbulence. Jets known as vertically sheared horizontal flows (VSHFs) often emerge in simulations of Boussinesq turbulence, but their dynamics is not yet clearly understood. In this work S3T analysis of the zonostrophic instability is extended to study VSHF emergence in two-dimensional Boussinesq turbulence using an analytical formulation of S3T amenable to perturbation stability analysis. VSHFs are shown to form via an instability that is analogous in stratified turbulence to the zonostrophic instability in β-plane turbulence. This instability is shown to be strikingly similar to the zonostrophic instability, suggesting that jet emergence in both geostrophic and nonrotating stratified turbulence may be understood as instances of the same generic phenomenon.

THE CHOICE GROUND OF DOWNHOLE STREAM PUMP GEOMETRICAL SIZES

The method of choosing geometric parameters of the well hole pump which ensures its operation in the mode of maximum efficiency is proposed. According to the algorithm developed, the ratio of the diameters of the working nozzle, the mixing chamber and the diffuser of the jet pump, as well as the distance between the nozzle and the speed equalization chamber and the axial dimensions of the flow part elements are regulated. During the process of establishing the required dimensions of the elements of the ejection system, the nature of the free working jet into the mixing chamber of the jet pump is taken into account, which determines the shape and structure of the estimated ratios governing the axial distance between the working nozzle and the resuscitation chamber of the mixing streams. The relationship between the mixing chamber diameters and the working nozzle and the amount of the jet pump coefficient of ejection which ensures its operation with the maximum possible values of the ejection system efficiency is shown. The analytical nature of the establishment of hydraulic interconnections among the elements of the ejection system is complemented by the experience of the practical use of deep jet pumps in the implementation of certain technological processes of construction, operation and repair of oil wells.

Statistical state dynamics of vertically sheared horizontal flows in two-dimensional stratified turbulence

Simulations of strongly stratified turbulence often exhibit coherent large-scale structures called vertically sheared horizontal flows (VSHFs). VSHFs emerge in both two-dimensional (2D) and three-dimensional (3D) stratified turbulence with similar vertical structure. The mechanism responsible for VSHF formation is not fully understood. In this work, the formation and equilibration of VSHFs in a 2D Boussinesq model of stratified turbulence is studied using statistical state dynamics (SSD). In SSD, equations of motion are expressed directly in the statistical variables of the turbulent state. Restriction to 2D turbulence facilitates application of an analytically and computationally attractive implementation of SSD referred to as S3T, in which the SSD is expressed by coupling the equation for the horizontal mean structure with the equation for the ensemble mean perturbation covariance. This second-order SSD produces accurate statistics, through second order, when compared with fully nonlinear simulations. In particular, S3T captures the spontaneous emergence of the VSHF and associated density layers seen in simulations of turbulence maintained by homogeneous large-scale stochastic excitation. An advantage of the S3T system is that the VSHF formation mechanism, which is wave–mean flow interaction between the emergent VSHF and the stochastically excited large-scale gravity waves, is analytically understood in the S3T system. Comparison with fully nonlinear simulations verifies that S3T solutions accurately predict the scale selection, dependence on stochastic excitation strength, and nonlinear equilibrium structure of the VSHF. These results constitute a theory for VSHF formation applicable to interpreting simulations and observations of geophysical examples of turbulent jets such as the ocean’s equatorial deep jets.

Evidence for the Maintenance of Slowly Varying Equatorial Currents by Intraseasonal Variability

AbstractRecent evidence from mooring data in the equatorial Atlantic reveals that semiannual and longer time scale ocean current variability is close to being resonant with equatorial basin modes. Here we show that intraseasonal variability, with time scales of tens of days, provides the energy to maintain these resonant basin modes against dissipation. The mechanism is analogous to that by which storm systems in the atmosphere act to maintain the atmospheric jet stream. We demonstrate the mechanism using an idealized model setup that exhibits equatorial deep jets. The results are supported by direct analysis of available mooring data from the equatorial Atlantic Ocean covering a depth range of several thousand meters. The analysis of the mooring data suggests that the same mechanism also helps maintain the seasonal variability.