Effect of hydrogen addition on the consumption speed of lean premixed laminar methane flames exposed to combined strain and heat loss

This study presents a numerical analysis of the impact of hydrogen addition on the consumption speed of premixed lean methane-air laminar flames exposed to combined strain and heat loss. Equivalence ratios of 0.9, 0.7, and 0.5 with fuel mixture composition ranging from pure methane to pure hydrogen are considered to cover a wide range of conditions in the lean region. The 1-D asymmetric counter-flow premixed laminar flame aCFPF with heat loss on the product side is considered as a flamelet configuration that represents an elementary unit of a turbulent flame and the consumption speed is used to characterize the effect of strain and heat loss. Due to the ambiguity in the definition of the consumption speed of multi-component mixtures, two definitions are compared. The definition of the consumption speed based on the heat release results in lower values of the stretched flame speed and even an opposite response to strain rate for some methane-hydrogen-air mixtures compared to the definition based on the fuel consumption. Strain rate leads to an increase in the flame speed for the lean methane-hydrogen mixtures, reaching a maximum value after which the flame speed decreases with strain rate. Heat loss decreases the stretched flame speed and leads to a sooner extinction of the flamelet due to combined strain and heat loss. Hydrogen addition and equivalence ratio significantly impact the maximum consumption speed and the flame response to combined strain rate and heat loss. The effect of hydrogen on the thermo-diffusive properties of the mixture, characterized by the Zel'dovich number and the effective Lewis number, are also analyzed and related to the effect on the consumption speed. Two definitions of the Lewis number of the multi-component fuel mixture are evaluated against the results from the aCFPF.Comment: Submitted to journal Combustion Theory and Modelling - Manuscript ID TCTM-2022-06-6

Tracking Labrador Sea Water property signals along the Deep Western Boundary Current

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 5348–5366, doi:10.1002/2017JC012921.Observations of the Deep Western Boundary Current (DWBC) at Line W on the western North Atlantic continental slope southeast of Cape Cod from 1995 to 2014 reveal water mass changes that are consistent with changes in source water properties upstream in the Labrador Sea. This is most evident in the cold, dense, and deep class of Labrador Sea Water (dLSW) that was created and progressively replenished and deepened by recurring winter convection during the severe winters of 1987–1994. The arrival of this record cold, fresh, and low potential vorticity anomaly at Line W lags its formation in the Labrador Sea by 3–7 years. Complementary observations along the path of the DWBC provide further evidence that this anomaly is advected along the boundary and indicate that stirring between the boundary and the interior intensifies south of the Flemish Cap. Finally, the consistency of the data with realistic advective and mixing time scales is assessed using the Waugh and Hall (2005) model framework. The data are found to be best represented by a mean transit time of 5 years from the Labrador Sea to Line W, with a leading order role for both advection by the DWBC and mixing between the boundary flow and interior waters.NSF Grant Numbers: OCE-0726720 , 1332667 , 13328342018-01-0

A barotropic vorticity budget for the subtropical North Atlantic based on observations

Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(11), (2019): 2781-2797, doi: 10.1175/JPO-D-19-0111.1.To ground truth the large-scale dynamical balance of the North Atlantic subtropical gyre with observations, a barotropic vorticity budget is constructed in the ECCO state estimate and compared with hydrographic observations and wind stress data products. The hydrographic dataset at the center of this work is the A22 WOCE section, which lies along 66°W and creates a closed volume with the North and South American coasts to its west. The planetary vorticity flux across A22 is quantified, providing a metric for the net meridional flow in the western subtropical gyre. The wind stress forcing over the subtropical gyre to the west and east of the A22 section is calculated from several wind stress data products. These observational budget terms are found to be consistent with an approximate barotropic Sverdrup balance in the eastern subtropical gyre and are on the same order as budget terms in the ECCO state estimate. The ECCO vorticity budget is closed by bottom pressure torques in the western subtropical gyre, which is consistent with previous studies. In sum, the analysis provides observational ground truth for the North Atlantic subtropical vorticity balance and explores the seasonal variability of this balance for the first time using the ECCO state estimate. This balance is found to hold on monthly time scales in ECCO, suggesting that the integrated subtropical gyre responds to forcing through fast barotropic adjustment.We thank Alonso Hernández-Guerra, M. Dolores Pérez-Hernández, and María Casanova-Masjoan for providing the inverse model results from Casanova-Masjoan et al. (2018). The A22 section is part of the WOCE/CLIVAR observing effort, with all data available at http://cchdo.ucsd.edu/. We thank Carl Wunsch, Patrick Heimbach, Chris Hill, and Diana Lees Spiegel for their assistance with the ECCO fields. The state estimates were provided by the ECCO Consortium for Estimating the Circulation and Climate of the Ocean funded by the National Oceanographic Partnership Program (NOPP) and can be downloaded at http://www.ecco-group.org/products.htm. The citable URL for the ECCO version 4 release 2 product is http://hdl.handle.net/1721.1/102062. We are grateful to Joseph Pedlosky and Glenn Flierl for their comments on an earlier version of this work. IALB and JMT were supported financially by U.S. NSF Grants OCE-0726720, 1332667, and 1332834. MS was supported by the U.S. NASA Sea Level Change Team (Contract NNX14AJ51G) and through the ECCO Consortium funding via the Jet Propulsion Laboratory. We thank two anonymous reviewers, whose thoughtful comments led to improvements.2020-04-1

The interaction of recirculation gyres and a deep boundary current

Author Posting. © American Meteorological Society, 2018. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 48 (2018): 573-590, doi:10.1175/JPO-D-17-0206.1.Motivated by the proximity of the Northern Recirculation Gyre and the deep western boundary current in the North Atlantic, an idealized model is used to investigate how recirculation gyres and a deep flow along a topographic slope interact. In this two-layer quasigeostrophic model, an unstable jet imposed in the upper layer generates barotropic recirculation gyres. These are maintained by an eddy-mean balance of potential vorticity (PV) in steady state. The authors show that the topographic slope can constrain the northern recirculation gyre meridionally and that the gyre’s adjustment to the slope leads to increased eddy PV fluxes at the base of the slope. When a deep current is present along the topographic slope in the lower layer, these eddy PV fluxes stir the deep current and recirculation gyre waters. Increased proximity to the slope dampens the eddy growth rate within the unstable jet, altering the geometry of recirculation gyre forcing and leading to a decrease in overall eddy PV fluxes. These mechanisms may shape the circulation in the western North Atlantic, with potential feedbacks on the climate system.We gratefully acknowledge an AMS graduate fellowship (IALB) and U.S. National Science Foundation Grants OCE-1332667 and 1332834 (IALB and JMT).2018-09-0

Moored observations of the Deep Western Boundary Current in the NW Atlantic: 2004–2014

Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 7488–7505, doi:10.1002/2017JC012984.A moored array spanning the continental slope southeast of Cape Cod sampled the equatorward-flowing Deep Western Boundary Current (DWBC) for a 10 year period: May 2004 to May 2014. Daily profiles of subinertial velocity, temperature, salinity, and neutral density are constructed for each mooring site and cross-line DWBC transport time series are derived for specified water mass layers. Time-averaged transports based on daily estimates of the flow and density fields in Stream coordinates are contrasted with those derived from the Eulerian-mean flow field, modes of DWBC transport variability are investigated through compositing, and comparisons are made to transport estimates for other latitudes. Integrating the daily velocity estimates over the neutral density range of 27.8–28.125 kg/m3 (encompassing Labrador Sea and Overflow Water layers), a mean equatorward DWBC transport of 22.8 × 106 ± 1.9 × 106 m3/s is obtained. Notably, a statistically significant trend of decreasing equatorward transport is observed in several of the DWBC components as well as the current as a whole. The largest linear change (a 4% decrease per year) is seen in the layer of Labrador Sea Water that was renewed by deep convection in the early 1990s whose transport fell from 9.0 × 106 m3/s at the beginning of the field program to 5.8 × 106 m3/s at its end. The corresponding linear fit to the combined Labrador Sea and Overflow Water DWBC transport decreases from 26.4 × 106 to 19.1 × 106 m3/s. In contrast, no long-term trend is observed in upper ocean Slope Water transport. These trends are discussed in the context of decadal observations of the North Atlantic circulation, and subpolar air-sea interaction/water mass transformation.G. Unger Vetlesen Foundation; Woods Hole Oceanographic Institution; US National Science Foundation2018-03-1

Physiological traits of Penicillium glabrum strain LCP 08.5568, a filamentous fungus isolated from bottled aromatised mineral water

International audiencePenicillium glabrum is an ubiquitous fungus distributed world wide. This fungus is a frequent contaminant in the food manufacturing industry. Environmental factors such as temperature, water activity and pH have a great influence on fungal development. In this study, a strain of P. glabrum referenced to as LCP 08.5568, has been isolated from a bottle of aromatised mineral water. The effects of temperature, aw and pH on radial growth rate were assessed on Czapeck Yeast Agar (CYA) medium. Models derived from the cardinal model with inflection (Rosso et al., 1993 An unexpected correlation between cardinal temperatures of microbial growth highlighted by a new model. J Theor. Bio. 162, 447-463) were used to fit the experimental data and determine for each factor, the cardinal parameters (minimum, optimum and maximum). Precise characterisation of the growth conditions for such a fungal contaminant, has an evident interest to understand and to prevent spoilage of food products

Evaluation of the efficacy of endovascular treatment of pelvic congestion syndrome

AbstractAimTo assess the efficacy of venous embolization treatment for the pelvic congestion syndrome (PCS).Patients and methodsRetrospective study of 33 female patients undergoing pelvic venous embolization between January 2008 and May 2012 in Bordeaux. The inclusion criteria were clinical symptoms of PCS documented by transabdominal Doppler ultrasound and/or pelvic magnetic resonance imaging. Patients with pelvic varicose veins feeding saphenous varicose veins were excluded. The efficacy of treatment was assessed on a Visual Analog Scale (VAS).ResultsThirty-three patients were included and the mean follow up period was 26months (3–59months). The VAS was 7.37 (standard deviation: 0.99) before embolization and 1.36 (standard deviation: 1.73) after embolization (P<0.0001). Twenty patients reported that their symptoms had completely disappeared, 11 had partially disappeared and two had gained no improvement. A significant fall was found in the number of patients with dyspareunia (P<0.0001). A single technical embolization failure was reported.ConclusionOur series demonstrates the efficacy of embolization treatment with a significant fall in the VAS in patients with PCS

Rapid export of waters formed by convection near the Irminger Sea's western boundary

The standard view of the overturning circulation emphasizes the role of convection, yet for waters to contribute to overturning, they must not only be transformed to higher densities but also exported equatorward. From novel mooring observations in the Irminger Sea (2014–2016), we describe two water masses that are formed by convection and show that they have different rates of export in the western boundary current. Upper Irminger Sea Intermediate Water appears to form near the boundary current and is exported rapidly within 3 months of its formation. Deep Irminger Sea Intermediate Water forms in the basin interior and is exported on longer time scales. The subduction of these waters into the boundary current is consistent with an eddy transport mechanism. Our results suggest that light intermediate waters can contribute to overturning as much as waters formed by deeper convection and that the export time scales of both project onto overturning variability. Plain Language Summary The deep ocean can regulate the Earth's climate by storing carbon and heat. At high latitudes, waters are cooled by the atmosphere and sink, but they can only be successfully stored in the deep ocean if they are exported toward the equator. In this study, we analyze new mooring observations in the Irminger Sea to investigate the cooling and export of high‐latitude waters. In addition to the well‐documented waters that are cooled in the center of the Irminger Sea, we find that saltier waters are cooled near the western boundary current. Both of these water types make it into boundary current and are exported. Our observations are consistent with the dynamics of swirling eddy motions. The eddy transport process is more effective for the waters cooled near the boundary current, implying that cooling near boundary currents may be more important for the climate than has been appreciated to date