Approximating Isoneutral Ocean Transport via the Temporal Residual Mean

Ocean volume and tracer transports are commonly computed on density surfaces because doing so approximates the semi-Lagrangian mean advective transport. The resulting density-averaged transport can be related approximately to Eulerian-averaged quantities via the Temporal Residual Mean (TRM), valid in the limit of small isopycnal height fluctuations. This article builds on a formulation of the TRM for volume fluxes within Neutral Density surfaces, (the “NDTRM”), selected because Neutral Density surfaces are constructed to be as neutral as possible while still forming well-defined surfaces. This article derives a TRM, referred to as the “Neutral TRM” (NTRM), that approximates volume fluxes within surfaces whose vertical fluctuations are defined directly by the neutral relation. The purpose of the NTRM is to more closely approximate the semi-Lagrangian mean transport than the NDTRM, because the latter introduces errors associated with differences between the instantaneous state of the modeled/observed ocean and the reference climatology used to assign the Neutral Density variable. It is shown that the NDTRM collapses to the NTRM in the limiting case of a Neutral Density variable defined with reference to the Eulerian-mean salinity, potential temperature and pressure, rather than an external reference climatology, and therefore that the NTRM approximately advects this density variable. This prediction is verified directly using output from an idealized eddy-resolving numerical model. The NTRM therefore offers an efficient and accurate estimate of modeled semi-Lagrangian mean transports without reference to an external reference climatology, but requires that a Neutral Density variable be computed once from the model’s time-mean state in order to estimate isopycnal and diapycnal components of the transport.

Download Full-text

An Assembly for Electrochemical Corrosion Studies in Aqueous Environments at High Temperature and Pressure

CORROSION ◽

10.5006/0010-9312-23.11.331 ◽

1967 ◽

Vol 23 (11) ◽

pp. 331-334 ◽

Cited By ~ 15

Author(s):

B. E. WILDE

Keyword(s):

Test Specimen ◽

Reference Electrode ◽

Electrochemical Corrosion ◽

High Temperature And Pressure ◽

Aisi Type ◽

Corrosion Studies ◽

External Reference ◽

Aqueous Environments ◽

Temperature And Pressure ◽

Type 304

Abstract An assembly is described, in which electrochemical corrosion measurements can be carried out in aqueous environments up to 314 C (598 F) and 105.5 kg/cm2. Test specimen mounting and corrosive environment containment procedures are discussed. A techniqie for using a high pressure electrolyte bridge with an external reference electrode is described. The performance of the system is demonstrated by potentiostatic anodic, cathodic and linear polarization experiments carried out on AISI Type 304 steel in dilute chloride solutions at 289 C.

Download Full-text

Dimensioning against fatigue - stress-based approach or fracture mechanics?

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/09544062jmes182 ◽

2006 ◽

Vol 220 (8) ◽

pp. 1109-1120

Author(s):

H-P Gänser ◽

K Glinsner ◽

W Eichlseder

Keyword(s):

Crack Length ◽

Crack Arrest ◽

Accurate Estimate ◽

Formal Structure ◽

Structural Stress ◽

Propagation Condition ◽

Stress Concentrations ◽

Notch Radius ◽

Sharp Crack ◽

Limiting Case

The non-propagation condition of a sharp crack introduced in the root of a generic notch is investigated. Thus, pre-existing flaws near structural stress concentrations are advantageously treated in a unified manner, giving in the limit of vanishing notch radius the case of a crack in an unnotched component, and in the limit of vanishing crack length the classical engineering case of a notched, crack-free component. Particular focus is put on the limiting case of vanishing crack length. The results are compared with the classical engineering strength estimate following the nominal stress concept. It is shown that both concepts may, with minor differences, be brought into the same formal structure. The transition between notch-like and crack-like behaviour of notches is investigated in some detail, giving an accurate estimate for the transition between both regimes as well as reliable lower bounds for the fatigue strength in both regimes with special consideration of crack arrest effects in flawed components.

Download Full-text

Water-Mass Transformations in a Neutral Density Framework and the Key Role of Light Penetration

Journal of Physical Oceanography ◽

10.1175/2007jpo3464.1 ◽

2008 ◽

Vol 38 (7) ◽

pp. 1357-1376 ◽

Cited By ~ 73

Author(s):

Daniele Iudicone ◽

Gurvan Madec ◽

Trevor J. McDougall

Keyword(s):

Water Mass ◽

Numerical Models ◽

Potential Temperature ◽

Shortwave Radiation ◽

Neutral Density ◽

In Situ Data ◽

Water Mass Formation ◽

New Formulation ◽

Surface Buoyancy ◽

Mass Formation

Abstract A new formulation is proposed for the evaluation of the dianeutral transport in the ocean. The method represents an extension of the classical diagnostic approach for estimating the water-mass formation from the buoyancy balance. The inclusion of internal sources such as the penetrative solar shortwave radiation (i.e., depth-dependent heat transfer) in the estimate of surface buoyancy fluxes has a significant impact in several oceanic regions, and the former simplified formulation can lead to a 100% error in the estimate of water-mass formation due to surface buoyancy fluxes. Furthermore, internal mixing can also be overestimated in inversions of in situ data when the shortwave radiation is not allowed to be penetrative. The method examines the evolution equation of neutral density via the tendencies of potential temperature and salinity. The neutral density framework does not require the choice of a reference pressure and thus, unlike previous approaches that consider potential density, it is well suited for examining the whole open-ocean water column. The methodology is easy to implement, particularly for ocean numerical models. The authors present here its application to a long simulation made with an ice–ocean global model, which allowed the method to be validated.

Download Full-text

Numerical modelling of FC bacteria using a dynamic and variable mortality rate

Journal of Water Sanitation and Hygiene for Development ◽

10.2166/washdev.2020.088 ◽

2020 ◽

Vol 10 (3) ◽

pp. 569-579

Author(s):

Siavash Mohammadi ◽

Seyed Mahmood Kashefipour

Keyword(s):

Water Quality ◽

Numerical Model ◽

Mortality Rate ◽

Model Comparison ◽

Empirical Equation ◽

Water Quality Management ◽

Environmental Parameters ◽

Accurate Estimate ◽

Effective Parameters ◽

Decay Coefficient

Abstract Faecal coliform (FC) microorganisms are one of the most important indicators in water quality management, since their presence reveals the possibility of existence of other dangerous microorganisms, leading to higher health risks. An accurate estimate of the concentration of this indicator helps better evaluation of the water pollution in riverine basins; thus, it is essential for future developments. The FC mortality rate depends on the physical, chemical, and biological processes in rivers. These processes are generally affected by environmental conditions. In this study, the decay coefficient (K) or mortality rate are related to the environmental parameters such as temperature, turbidity, pH, and salinity by an empirical equation. The results showed that turbidity and temperature are the most effective parameters. Moreover, an empirical equation was developed utilizing numerical model calibration, which describes the relationship of the mortality rate (K) with water temperature and turbidity. This equation was then added to the water quality module of the FASTER numerical model. Comparison of the measured FC concentrations with the predicted values obtained from the numerical model showed that the model accuracy significantly improved for the dynamic and variable decay coefficient.

Download Full-text

3D Natural State Modeling of Mount Iyang-Argopuro Geothermal Area, East Java, Indonesia

Journal of Geoscience Engineering Environment and Technology ◽

10.25299/jgeet.2021.6.2.4127 ◽

2021 ◽

Vol 6 (2) ◽

pp. 113-119

Author(s):

Dewi Asmorowati ◽

Allen Haryanto Lukmana ◽

Rizqi Mahfudz Prasetyo

Keyword(s):

Numerical Model ◽

Resource Assessment ◽

Geochemical Data ◽

Natural State ◽

Geothermal Area ◽

Good Match ◽

Rectangular Cell ◽

Pressure Profiles ◽

Temperature And Pressure ◽

Model Temperature

Mount Iyang-Argopuro is one of the geothermal working areas in the East Java. Mount Iyang-Argopuro has the potential of 185 MWe of reserves and 110 MWe of resources. It is estimated to have a liquid dominated reservoir with temperature up to 250-275 oC. An early 3D natural state numerical model of Mount Iyang-Argopuro Field is created using TOUGH2 simulator in order to identify the undisturbed condition of reservoir and resource assessment. Since Mount Iyang-Argopuro geothermal area is still in the exploration stage, the model created based on based on geological, geophysical, and geochemical data. The model has an area 14 km x 8.2 km and 9180 m in thickness. The model consists of 7410 of rectangular cell blocks with the roughest cell size is 1000 m x 1000 m and the finest is 200 m x 500 m. The model is verified by matching the model temperature and pressure profiles to the calculated geothermometer temperature and pressure, which shows good match enough.

Download Full-text

Numerical Simulation and Analyses of Flow Rate Exchange between Accumulator and Main loop

E3S Web of Conferences ◽

10.1051/e3sconf/201912804005 ◽

2019 ◽

Vol 128 ◽

pp. 04005

Author(s):

Meng Qingliang ◽

Zhao Zhenming ◽

Zhang Huandong

Keyword(s):

Numerical Model ◽

Stokes Equations ◽

Model Simulation ◽

Navier Stokes ◽

Working Fluid ◽

Total System ◽

Two Phase ◽

Main Loop ◽

Temperature And Pressure ◽

Phase Fluid

In order to study the dynamic behaviors of heat and mass transfer between accumulator and mechanically pumped two–phase loop (MPTL) system, a transient numerical model is developed by using thetime–dependent Navier–Stokes equations. By comparison between simulation and test results, it is found that the error of numerical model is in the range of ±10%, which verifies the validityand accuracy of the model. Simulation results show that the accumulator will exchange fluid with the main loop in responseto heat load variations. In this case, the temperature and pressure of two phase fluid in accumulator, and the total system flow resistance will be affected. The rate of mass transferbetween accumulator and main loop will increase along with the charge amount of working fluid, and also for the variation trend of temperature and pressure of two phase fluid in the accumulator. The model can be used to study the operating state, flow and heat characteristics of MPTL system.

Download Full-text

Seasonal Evolution of Cape Darnley Bottom Water Revealed by Mooring Measurements

Frontiers in Marine Science ◽

10.3389/fmars.2021.657119 ◽

2021 ◽

Vol 8 ◽

Author(s):

Genta Mizuta ◽

Yasushi Fukamachi ◽

Daisuke Simizu ◽

Yoshimasa Matsumura ◽

Yujiro Kitade ◽

...

Keyword(s):

Bottom Water ◽

Baroclinic Instability ◽

Potential Temperature ◽

Neutral Density ◽

Source Water ◽

Short Term ◽

Seasonal Evolution ◽

Ice Production ◽

Over Time ◽

Short Term Variability

This study examines the seasonal evolution of Cape Darnley Bottom Water (CDBW), using the results of mooring and hydrographic measurements in the slope region off Cape Darnley in 2008–2009 and 2013–2014. Newly formed CDBW began reaching the western and nearshore part of the slope region off Cape Darnley in April, spread to the offshore and eastern part in May, and reached the easternmost part in September. The potential temperature and salinity decreased and the neutral density increased when newly formed CDBW reached mooring sites. Potential temperature-salinity properties of CDBW changed over time and location. The salinity of the source water of CDBW estimated from potential temperature-salinity diagrams started to increase at a nearshore mooring in late April, which is about 2 months after the onset of sea-ice production, and continued to increase during the ice production season. It is most probable that the accumulation of brine in the Cape Darnley polynya produces the seasonal variation of potential temperature-salinity properties of CDBW. Two types of CDBW were identified. Cold and less saline CDBW and warm and saline CDBW were present in Wild and Daly Canyons, respectively. This indicates that the salinity of the source water of CDBW increased in the westward direction. CDBW exhibited short-term variability induced by baroclinic instability.

Download Full-text

The Carnot Cycle and Area-Specific Work Equivalence on a Skew T–logp Diagram

Monthly Weather Review ◽

10.1175/2008mwr2507.1 ◽

2008 ◽

Vol 136 (10) ◽

pp. 4010-4012

Author(s):

Alex DeCaria

Keyword(s):

Potential Temperature ◽

Poisson’S Equation ◽

Carnot Cycle ◽

Specific Work ◽

Poisson's Equation ◽

Direct Reading ◽

Temperature Potential ◽

Extreme Sensitivity ◽

Temperature And Pressure

Attempts to calculate the area to specific work equivalence on a skew T–logp diagram for a Carnot cycle can lead to large errors if the pressures of the nodes of the cycle are estimated from the diagram. The cause is the extreme sensitivity of the calculation to the pressures of the nodes. To keep errors within 10%, the pressures of the nodes must be known to within 0.1 hPa, a precision that is not practical by direct reading from the diagram. To avoid these errors the pressures of the nodes should be calculated directly from Poisson’s equation, which relates temperature, potential temperature, and pressure.

Download Full-text

Does lateral stirring really take place along neutral surfaces in double-diffusive regions of the oceans?

10.5194/egusphere-egu2020-7494 ◽

2020 ◽

Author(s):

Gabriel Wolf ◽

Tailleux Remi ◽

Ferreira David ◽

Kuhlbrodt Till

Keyword(s):

Ad Hoc ◽

Climate Models ◽

Potential Temperature ◽

Water Masses ◽

Neutral Density ◽

Positive Density ◽

Potential Density ◽

Source Regions ◽

Density Ratios ◽

Double Diffusive

<p><span>Potential temperature/salinity (theta/S) characteristics of water masses in the ocean interior can often be traced back over long distances to their source regions. In practice, understanding how water masses are altered by interior mixing and stirring requires a detailed understanding of the interior pathways linking fluid parcels to their source regions. So far, oceanographers have generally assumed that these pathways are strongly constrained to take place on potential density surfaces of some kind, of which the most commonly employed have been the Jackett and McDougall neutral density variable and sigma2, the potential density referenced to 2000 dbar. Because sigma2 is a somewhat ad-hoc and artificial construct, the more physically-based neutral density variable has been widely assumed to represent the most accurate variable to describe interior pathways, but the analysis of van Sebille et al. (2011) intriguingly suggests otherwise. In order to shed light on the issue, this work hypothesizes that if neutral surfaces were optimal to describe lateral stirring in the ocean, they should be the surfaces along which the observed spread in potential temperature and salinity anomalies should be minimum, since lateral stirring is about 7 orders of magnitude more vigorous in the lateral directions than perpendicular to them. Surprisingly, it is found that this is actually never the case in ocean regions with positive density ratios, traditionally associated with double-diffusive regimes. In those regions, indeed, it is always possible to find material surfaces, not necessarily definable in terms of potential density, along which the spread is reduced for both potential temperature and salinity compared to that over neutral surfaces. In doubly-stable regions, on the other hand, it is not possible to find material variables able to simultaneously reduce both the spread in potential temperature and salinity compared to that over neutral surfaces. Given the widespread nature of double-diffusive regimes in the world oceans, especially in the Atlantic Ocean, these results have strong implications for the ability of ocean climate models to accurately simulate water masses, as it is unclear how to maintain water masses properties by mixing vigorously along directions along which the spread in theta/S is far from its minimum.</span></p>

Download Full-text