Journal articles: 'Average residence time'

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Landfeld, A., R. Žitný, M. Houška, K. Kýhos, and P. Novotná. "Residence time distribution during egg yolk pasteurisation." Czech Journal of Food Sciences 20, No. 5 (2011): 193–201. http://dx.doi.org/10.17221/3531-cjfs.

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This work describes the determination of the average residence times during egg yolk &ndash; and whole liquid eggs pasteurisation in an industrial pasteurisation equipment (plate pasteuriser + tube holder). For the detection of the impulse the conductivity method was used. Conductivity was then monitored using the bridge method. In the system, the total of 3 probes were placed. To mark the particles of the flowing product, salted yolk with the content of salt of 1.3 or 1.8% was used. In addition, rheological properties of pasteurised yolk were determined at the temperatures of 5, 25, 45, and 65&deg;C. Based on the geometry of the channels in the individual sections of the pasteurisation equipment, the character of the flow was estimated using the Re criterion and was found to be laminar in all parts of the system. The work includes the comparison of the average residence times obtained by (a) the method of volumes, (b) the analysis of the conductivity response, (c) the estimate made by using the TUPLEX software, and (d) the estimate of the peaks of the conductivity response. &nbsp;

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Vergnes, B. "Calculation of Average Residence Time in a Ko-kneader." International Polymer Processing 26, no. 5 (2011): 587–89. http://dx.doi.org/10.3139/217.2528.

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Osácar, Carlos, Manuel Membrado, and Amalio Fernández-Pacheco. "Brief communication: Residence time of energy in the atmosphere." Nonlinear Processes in Geophysics 27, no. 2 (2020): 235–37. http://dx.doi.org/10.5194/npg-27-235-2020.

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Abstract. In atmospheric chemistry, a parameter called residence time is defined for each gas as T=M/F, where M represents the mass of the gas in the atmosphere and F is the total average influx or outflux, which in time averages are equal. In this brief communication, we extend this concept from matter to energy which is also a conservative quantity and estimate the average residence time of energy in the atmosphere, which amounts to about 58 d. A similar estimation for the residence time of energy in the Sun is of the order of 107 years, which agrees with the Kelvin–Helmholtz timescale.

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van der Ent, Ruud J., and Obbe A. Tuinenburg. "The residence time of water in the atmosphere revisited." Hydrology and Earth System Sciences 21, no. 2 (2017): 779–90. http://dx.doi.org/10.5194/hess-21-779-2017.

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Abstract. This paper revisits the knowledge on the residence time of water in the atmosphere. Based on state-of-the-art data of the hydrological cycle we derive a global average residence time of 8.9 ± 0.4 days (uncertainty given as 1 standard deviation). We use two different atmospheric moisture tracking models (WAM-2layers and 3D-T) to obtain atmospheric residence time characteristics in time and space. The tracking models estimate the global average residence time to be around 8.5 days based on ERA-Interim data. We conclude that the statement of a recent study that the global average residence time of water in the atmosphere is 4–5 days, is not correct. We derive spatial maps of residence time, attributed to evaporation and precipitation, and age of atmospheric water, showing that there are different ways of looking at temporal characteristics of atmospheric water. Longer evaporation residence times often indicate larger distances towards areas of high precipitation. From our analysis we find that the residence time over the ocean is about 2 days less than over land. It can be seen that in winter, the age of atmospheric moisture tends to be much lower than in summer. In the Northern Hemisphere, due to the contrast in ocean-to-land temperature and associated evaporation rates, the age of atmospheric moisture increases following atmospheric moisture flow inland in winter, and decreases in summer. Looking at the probability density functions of atmospheric residence time for precipitation and evaporation, we find long-tailed distributions with the median around 5 days. Overall, our research confirms the 8–10-day traditional estimate for the global mean residence time of atmospheric water, and our research contributes to a more complete view of the characteristics of the turnover of water in the atmosphere in time and space.

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Liu, Zhe, Hao Wei, Guangshan Liu, and Jing Zhang. "Simulation of water exchange in Jiaozhou Bay by average residence time approach." Estuarine, Coastal and Shelf Science 61, no. 1 (2004): 25–35. http://dx.doi.org/10.1016/j.ecss.2004.04.009.

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Tinker, Sarah C., Christine L. Moe, Mitchel Klein, et al. "Drinking water residence time in distribution networks and emergency department visits for gastrointestinal illness in Metro Atlanta, Georgia." Journal of Water and Health 7, no. 2 (2009): 332–43. http://dx.doi.org/10.2166/wh.2009.022.

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We examined whether the average water residence time, the time it takes water to travel from the treatment plant to the user, for a zip code was related to the proportion of emergency department (ED) visits for gastrointestinal (GI) illness among residents of that zip code. Individual-level ED data were collected from all hospitals located in the five-county metro Atlanta area from 1993 to 2004. Two of the largest water utilities in the area, together serving 1.7 million people, were considered. People served by these utilities had almost 3 million total ED visits, 164,937 of them for GI illness. The relationship between water residence time and risk for GI illness was assessed using logistic regression, controlling for potential confounding factors, including patient age and markers of socioeconomic status (SES). We observed a modestly increased risk for GI illness for residents of zip codes with the longest water residence times compared with intermediate residence times (odds ratio (OR) for Utility 1 = 1.07, 95% confidence interval (CI)=1.03, 1.10; OR for Utility 2 = 1.05, 95% CI = 1.02, 1.08). The results suggest that drinking water contamination in the distribution system may contribute to the burden of endemic GI illness.

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Liu Ya-Chun. "A new method for monitoring the average residence time of atmospheric particulate matter." Acta Physica Sinica 62, no. 9 (2013): 092301. http://dx.doi.org/10.7498/aps.62.092301.

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Li, S. H., S. Yang, H. R. Yang, et al. "Particle Holdup and Average Residence Time in the Cyclone of a CFB Boiler." Chemical Engineering & Technology 31, no. 2 (2008): 224–30. http://dx.doi.org/10.1002/ceat.200700264.

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Liu, Taibei, Weijian Zhou, Peng Cheng, and G. S. Burr. "A Survey of the 14C Content of Dissolved Inorganic Carbon in Chinese Lakes." Radiocarbon 60, no. 2 (2017): 705–16. http://dx.doi.org/10.1017/rdc.2017.113.

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AbstractWe present radiocarbon (14C) measurements of dissolved inorganic carbon (DIC) from surface waters of 11 lakes, widely distributed in China. Surface lake water DIC F14C values show distinct differences, and we relate these to the physical exchange character (“open” or “closed”) of each lake. Open lakes studied here generally have lower DIC F14C values than closed lakes. We present a simple model of a lake water cycle to calculate an average residence time for each lake. Comparisons between lake DIC F14C and average residence time shows that the DIC F14C increases with the average residence time and reflects a steady-state.

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Li, Tingting, Yu Zhu, Liyue Lin, Wenqian Ke, and Baoyu Xiao. "Spatial differentiation and influencing factors of floating population’s length of residence willingness." International Journal of Population Studies 7, no. 2 (2022): 27. http://dx.doi.org/10.18063/ijps.v7i2.1363.

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Based on the dynamic monitoring data of China’s floating population in 2018, according to the length of time that the floating population is willing to stay in the inflow area, the residence intention is divided into three types: short-term residence intention, long-term residence intention and permanent residence intention. The spatial differentiation and influencing factors of different types of residence intention of floating population in cities at and above the prefecture level in China are compared and analyzed by using spatial analysis technology and hierarchical model. It is found that the proportion of floating population with short-term and long-term residence intention is more than 60%, indicating that amphibious and multi-habitat livelihood is still the dominant livelihood strategy of floating population; there is an obvious spatial difference between short-term and permanent residence willingness. The short-term residence willingness is the highest in the eastern region and the lowest in the northeast region, while the permanent residence willingness shows a completely opposite distribution pattern; the floating population in the central and western regions has the highest willingness to stay for a long time. The results of the model show that the inflow characteristics and the individual characteristics of the floating population jointly affect different types of residence intention: in the eastern and central regions, economically developed areas and areas with high average wages, the floating population has higher short-term and long-term residence intention and lower permanent residence intention; the floating population who are male with agricultural registered permanent residence, low-level of education and family average monthly income, short floating time and inter provincial mobility tend to stay for a short time and a long time; the floating population who are female with non-agricultural registered permanent residence, high-level of education and family average monthly income, moving within the province and outside the province for a long time are more willing to settle permanently in the inflow place.

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Li, Liang Chao. "CFD Simulation of Gas Residence Time Distribution in Agitated Tank." Advanced Materials Research 732-733 (August 2013): 467–71. http://dx.doi.org/10.4028/www.scientific.net/amr.732-733.467.

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Gas residence time is an important parameter for gas-liquid agitated tank. Two approaches, i.e., Euler-Tracer method and CFD-DPM method are proposed for predicting gas residence time distribution (RTD) in an aerated agitated tank by using a Fluent 6.2 software package. The simulation results show that the characteristic of the gas-RTD is a curve with single peak and long tailing. Bubble size, stirring speed and gas inlet flow rate have great effect on gas-RTD in the stirred tank. Small bubbles have wider residence time distribution and stay in the vessel longer than the large bubbles and tend to complete mixing. With increasing of impeller speed or decreasing of gas inlet rate, gas-RTD become wider and have longer average gas residence time, which is in favor of gas effectively utilization.

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Millen, Amy E., Mary Pettinger, Jo L. Freudenheim, et al. "Incident Invasive Breast Cancer, Geographic Location of Residence, and Reported Average Time Spent Outside." Cancer Epidemiology Biomarkers & Prevention 18, no. 2 (2009): 495–507. http://dx.doi.org/10.1158/1055-9965.epi-08-0652.

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Schlumbrecht, M. P., and S. Chang. "Incident Invasive Breast Cancer, Geographic Location of Residence, and Reported Average Time Spent Outside." Breast Diseases: A Year Book Quarterly 20, no. 4 (2009): 366–67. http://dx.doi.org/10.1016/s1043-321x(09)79389-0.

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14

Renaud, M., J. Thibault, and P. I. Alvarez. "INFLUENCE OF SOLIDS MOISTURE CONTENT ON THE AVERAGE RESIDENCE TIME IN A ROTARY DRYER." Drying Technology 19, no. 9 (2001): 2131–50. http://dx.doi.org/10.1081/drt-100107491.

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Ganusov, Vitaly, and Jeremy Auerbach. "Mathematical modeling suggests rapid migration of naive lymphocytes via lung capillaries and liver sinusoids (P5100)." Journal of Immunology 190, no. 1_Supplement (2013): 58.4. http://dx.doi.org/10.4049/jimmunol.190.supp.58.4.

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Abstract The kinetics of recirculation of naive lymphocytes in the body has important implications for the speed at which local infections are detected and controlled by immune responses. In this study using mathematical modeling we analyze experimental data on migration of 51Cr-labeled thoracic duct lymphocytes (TDLs) via major lymphoid and nonlymphoid tissues of rats. We show that 95% of naive lymphocytes in the blood must travel via capillaries in the lung or sinusoids of the liver before they enter secondary lymphoid tissues. In contrast with a widespread belief that lymphocytes take long time to travel via vasculature of the lung and liver, our analysis suggests that lymphocytes travel via lung capillaries and liver sinusoids at an extremely rapid rate with the average residence time in these tissues being less than 1 minute. The model also predicts a relatively short average residence time of TDLs in the spleen (2.5 hours) and a longer average residence time of TDLs in major lymph nodes and Peyer's patches (10 hours). Surprisingly, we find that average residence time of lymphocytes is similar in lymph nodes draining skin (subcutaneous LNs), gut (mesenteric LNs) or in Peyer's patches.Taken together, our study for the first time provides a comprehensive, systems view of recirculation kinetics of naive lymphocytes in the whole organism.

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Hewageegana, Viyaktha Hithaishi, Maitane Olabarrieta, and Jose M. Gonzalez-Ondina. "Main Physical Processes Affecting the Residence Times of a Micro-Tidal Estuary." Journal of Marine Science and Engineering 11, no. 7 (2023): 1333. http://dx.doi.org/10.3390/jmse11071333.

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Residence time is an important parameter linked to the water quality in an estuary. In this paper, we identify and analyze the main processes that affect the residence time of the Caloosahatchee River Estuary, a micro-tidal and mixed diurnal-semidiurnal estuary located in western Florida. Multiyear validated hydrodynamic hindcast results were coupled with an offline particle tracking model to compute the residence time of the estuary, which showed a strong seasonality driven by the river discharge. The residence time reduced with increasing river flow. The wind velocity and direction also affected the residence time. The influence of the wind was dependent on the magnitude of the river discharge. In general, upstream-directed wind increased residence time, while downstream-directed wind decreased residence time. Downstream wind during the dry period reduced residence time on average by a week. Processes such as water density gradient-induced circulation and particle buoyancy also influenced the residence time of the estuary. The outcomes of this study can be used to better understand the influence of the main physical processes affecting the residence time at other similar estuaries and to help in the management of the estuaries to improve their water quality.

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McGhee, James, and Shervin Ghafouri. "Bacterial residence time in the intestine of Caenorhabditis elegans." Nematology 9, no. 1 (2007): 87–91. http://dx.doi.org/10.1163/156854107779969718.

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AbstractWe fed adult Caenorhabditis elegans fluorescent microspheres mixed with their Escherichia coli food and then measured the total fluorescence of expelled faeces as a function of time after transfer to unlabelled bacteria. Intestinal clearance obeys a simple first-order decay or dilution curve: we estimate that 43 ± 10% of the maximum intestinal volume is expelled in each defecation and the average residence time of a bead (by inference, a bacterium) is less than 2 min. Our results raise questions how bacteria can be sufficiently digested in this brief period to provide energy and material to sustain the high rate of C. elegans oocyte production.

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Takeoka, Hidetaka, and Toshiya Hashimoto. "Average residence time of matter in coastal waters in a transport system including biochemical processes." Continental Shelf Research 8, no. 11 (1988): 1247–56. http://dx.doi.org/10.1016/0278-4343(88)90004-0.

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Kim, Jin-Ho, Sok-Jin Hong, Won-Chan Lee, Jeong-Bae Kim, Hyung-Chul Kim, and Dong-Myung Kim. "Estimation on Average Residence Time of Particulate Matters in Geoje Bay using Particle Tracking Model." Journal of the Korean Society of Marine Environment and Safety 22, no. 1 (2016): 20–26. http://dx.doi.org/10.7837/kosomes.2016.22.1.020.

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Luciano, De Paola, Panzino Mariantonia, Saturno Laura, et al. "The Effect of Residence Time of No-tunneled Hemodialysis Catheters on Infection and Thrombosis Outcome. Identification of CVC’s Time Cut-off." Journal of Clinical Nephrology 8, no. 1 (2024): 023–31. http://dx.doi.org/10.29328/journal.jcn.1001122.

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Introduction: Permanent vascular access (arteriovenous fistula (AVF), arteriovenous graft (AVG)) is susceptible to acute events that reduce patency. The temporary central venous catheter (CVC) constitutes bridging therapy for primary vascular access dysfunction. The impact of “residence time” on the rate of dysfunction/thrombosis or infection remains to be explored. AIM: 1) To evaluate the impact of CVC residence time on outcomes (infection or Thrombosis/dysfunction) in consecutive temporary CVCs adjusted for the insertion site (upper site vs. lower site). 2) To establish a cut-off resident time. Patients and methods: Seventeen prevalent hemodialysis patients with three consecutive CVCs are followed up prospectively in an observational study for a period equivalent to the permanence of the CVCs. The data is recorded at the beginning of the CVC time. The diagnosis of catheter-related bloodstream infection and thrombosis/dysfunction is made following the K-Doqi 2019 guidelines. Statistical analysis: Seventeen hemodialysis patients (51 CVCs) were included. The ‘CVC resident time’ of each individual patient ((i.e. βcoefficient (log-transformed)*AUC)) was determined using LMM and then inserted into multivariate Cox models to assess infection and dysfunction/thrombosis outcomes (Joint Models). The AUC was calculated at various baseline levels of CVC time (10th……50th percentile). The cut-off point for thrombosis in CVC time corresponds to the mean of the CVC time at the 30th percentile of all CVCs. Results: The CVC time is different for CVC’s site insertion and sequence. From the analysis of multivariate joint models, CVC resident time appears not to be significant for infection, but heterogenicity for the insertion site (ref3-4=upper site) is significant for the outcome of thrombosis/dysfunction. From the study of survival analysis, the free survival from outcomes by CVC site insertion appears to be significant for thrombosis/dysfunction. The average time of CVCs’ calculation at the 30th percentile is 14 days (cut-off). Conclusion: No tunneled hemodialysis Catheter (NTHC) residence time is considered not to be a risk factor for infection, but it represents a risk factor for lower access thrombosis. After the cut-off time of 14 days, the advantage of the higher NTHCs is lost.

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Crump, Byron C., Charles S. Hopkinson, Mitchell L. Sogin, and John E. Hobbie. "Microbial Biogeography along an Estuarine Salinity Gradient: Combined Influences of Bacterial Growth and Residence Time." Applied and Environmental Microbiology 70, no. 3 (2004): 1494–505. http://dx.doi.org/10.1128/aem.70.3.1494-1505.2004.

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ABSTRACT Shifts in bacterioplankton community composition along the salinity gradient of the Parker River estuary and Plum Island Sound, in northeastern Massachusetts, were related to residence time and bacterial community doubling time in spring, summer, and fall seasons. Bacterial community composition was characterized with denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA. Average community doubling time was calculated from bacterial production ([14C]leucine incorporation) and bacterial abundance (direct counts). Freshwater and marine populations advected into the estuary represented a large fraction of the bacterioplankton community in all seasons. However, a unique estuarine community formed at intermediate salinities in summer and fall, when average doubling time was much shorter than water residence time, but not in spring, when doubling time was similar to residence time. Sequencing of DNA in DGGE bands demonstrated that most bands represented single phylotypes and that matching bands from different samples represented identical phylotypes. Most river and coastal ocean bacterioplankton were members of common freshwater and marine phylogenetic clusters within the phyla Proteobacteria, Bacteroidetes, and Actinobacteria. Estuarine bacterioplankton also belonged to these phyla but were related to clones and isolates from several different environments, including marine water columns, freshwater sediments, and soil.

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Lecart, Mathieu, Thomas Dobbelaere, Lauranne Alaerts, et al. "Land reclamation and its consequences: A 40-year analysis of water residence time in Doha Bay, Qatar." PLOS ONE 19, no. 1 (2024): e0296715. http://dx.doi.org/10.1371/journal.pone.0296715.

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Qatar’s rapid industrialization, notably in its capital city Doha, has spurred a surge in land reclamation projects, leading to a constriction of the entrance to Doha Bay. By reducing and deflecting the ocean circulation, land reclamation projects have reduced the effective dispersion of wastewater introduced into the bay and hence degraded the water quality. Here, we assess fluctuations in water residence time across three distinct eras (1980, 2000, and 2020) to gauge the impact of successive land reclamation developments. To do this, we couple the multi-scale ocean model SLIM with a Lagrangian model for water residence time within Doha’s coastal area. We consider three different topographies of Doha’s shoreline to identify which artificial structures contributed the most to increase water residence time. Our findings reveal that the residual ocean circulation in Doha Bay was predominantly impacted by northern developments post-2000. Between 1980 and 2000, the bay’s residence time saw a modest rise, of about one day on average. However, this was followed by a substantial surge, of three to six days on average, between 2000 and 2020, which is mostly attributable to The Pearl mega artificial island development. Certain regions of the bay witnessed a tripling of water residence time. Given the ongoing population expansion along the coast, it is anticipated that the growth of artificial structures and coastal reclamation will persist, thereby exacerbating the accumulation of pollutants in the bay. Our findings suggest that artificial offshore structures can exert far-reaching, non-local impacts on water quality, which need to be properly assessed during the planning stages of such developments.

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Kim, Jin Ho, Sung-Eun Park, Youngmin Kim, et al. "Assessing Average Residence Time as a Physical Descriptor for Shellfish Farming Areas in Jaran Bay, Korea." Journal of Environmental Science International 29, no. 3 (2020): 273–82. http://dx.doi.org/10.5322/jesi.2020.29.3.273.

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Cucco, Andrea, Jacobo Martín, Giovanni Quattrocchi, Harold Fenco, Georg Umgiesser, and Daniel Alfredo Fernández. "Water Circulation and Transport Time Scales in the Beagle Channel, Southernmost Tip of South America." Journal of Marine Science and Engineering 10, no. 7 (2022): 941. http://dx.doi.org/10.3390/jmse10070941.

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The Beagle Channel is a long and narrow interoceanic passage within the Tierra del Fuego archipelago in the southernmost tip of South America. A high-resolution 3D hydrodynamic model based on the finite elements method was applied to investigate the residual circulation, water fluxes and transport time scales inside this channel. Numerical solutions were analyzed at seasonal time scale and the model results compared with observed ocean data. The circulation pattern is characterized by a west-to-east residual flow with low intensity and low seasonal variability. The water fluxes through the channel were estimated to be, on average, around 12,700 m3/s, with inflow through its western entrance and eastwards outflow mainly through the Mackinlay Strait. The water residence times vary seasonally with basin averages between 36 and 43 days and maximum values between 53 and 95 days. The results provide an overview of the hydrodynamics and water residence times in the Beagle Channel, a unique ecosystem threatened by recent anthropogenic pressures and climate change.

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Luo, Bi Jun, Hai Hong Wu, Shao Yan Lu, Yan An Zhang, and Qi Zhang. "Analysis on Crystallization Kinetics of Gypsum Prepared by Bittern under 40°C." Advanced Materials Research 968 (June 2014): 112–15. http://dx.doi.org/10.4028/www.scientific.net/amr.968.112.

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Crystallization kinetics experiment of calcium sulfate dehydrates, which is prepared by bittern under 40oC and 200r/min conditions, is carried out. According to the results of the experimental data, the relationship of nucleus particle-number density n0 and crystal growth rate G with the residence time is summarized. Also, the average diameter of gypsum crystal is decreasing with the residence time increase. Meanwhile, the crystallization kinetics formula is derived to be: B0=3.20×105G0.47.

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Sherwin, S. J., D. J. Doorly, P. Franke, and J. Peiró. "Unsteady near wall residence times and shear exposure in model distal arterial bypass grafts." Biorheology: The Official Journal of the International Society of Biorheology 39, no. 3-4 (2002): 365–71. http://dx.doi.org/10.1177/0006355x2002039003004012.

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Building on previous studies of unsteady flow within model distal bypass grafts we analyse the near wall residence times and shear exposure in a 45 degrees anastomosis under symmetrical and symmetry breaking geometric configurations. We define residence time as the minimum time for a particle to exit a spherical region and shear exposure as a temporal integral of the Huber‐Henky‐von‐Mises criterion along a particle path over a fixed time interval. Decomposing the pulsatile cycle into four equal intervals we find that the interval of peak residence time in the host vessel is from mid‐deceleration to peak diastole and peak diastole to mid‐acceleration. The asymmetric model is shown to have a significantly lower residence time during these intervals. Considering the shear exposure prior to the residence time evaluation we determine that a higher average shear exposure exists in the asymmetric model associated with the upstream geometry modification. Analysis of the regions of high residence time and shear exposure suggests that the “toe” region and the interface between the “heel” and bulk flow are more significant than the bed and heel region. Although the asymmetric model considered in this study reduces residence times in the host artery, the product of the measure of shear exposure and residence time is not found to be preferable. If shear exposure were to be considered as an important factor in particle activation, the findings imply that for junction optimisation, greater consideration needs to be given both to the local junction asymmetry and upstream influence on the shear history.

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Laskari, A., R. de Kat, R. J. Hearst, and B. Ganapathisubramani. "Time evolution of uniform momentum zones in a turbulent boundary layer." Journal of Fluid Mechanics 842 (March 13, 2018): 554–90. http://dx.doi.org/10.1017/jfm.2018.126.

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Time-resolved planar particle image velocimetry was used to analyse the structuring of a turbulent boundary layer into uniform momentum zones (UMZs). The instantaneous peak-detection method employed by Adrian et al. (J. Fluid Mech., vol. 422, 2000, pp. 1–54) and de Silva et al. (J. Fluid Mech., vol. 786, 2016, pp. 309–331) is extended to account for temporal coherence of UMZs. The resulting number of zones detected appears to follow a normal distribution at any given instant. However, the extreme cases in which the number of zones is either very high or very low, are shown to be linked with two distinct flow states. A higher than average number of zones is associated with a large-scale $Q2$ event in the log region which creates increased small-scale activity within that region. Conversely, a low number of zones corresponds to a large-scale $Q4$ event in the log region and decreased turbulent activity away from the wall. The residence times, within the measurement plane, of zones belonging to the latter scenario are shown to be on average four times larger than those of zones present during higher than average zone structuring states. For both cases, greater residence times are observed for zones of higher momentum that are generally closer to the free stream.

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Saito, M., S. Onodera, K. Okubo, et al. "Effects of physical and morphometric factors on nutrient removal properties in agricultural ponds." Water Science and Technology 72, no. 12 (2015): 2187–93. http://dx.doi.org/10.2166/wst.2015.441.

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Effects of physical and morphometric factors on nutrient removal properties were studied in small agricultural ponds with different depths, volumes, and residence times in western Japan. Average residence time was estimated to be &gt;15 days, and it tended to decrease from summer to winter because of the increase in water withdrawal for agricultural activity. Water temperature was clearly different between the surface and bottom layers; this indicates that thermal stratification occurred in summer. Chlorophyll-a was significantly high (&gt;20 μg/L) in the surface layer (&lt;0.5 m) and influenced by the thermal stratification. Removal ratios of dissolved total nitrogen (DTN) and dissolved total phosphorus in the ponds were estimated to be 53–98% and 39–98% in August and 10–92% and 36–57% in December, respectively. Residence time of the ponds was longer in August than in December, and DTN removal, in particular, was more significant in ponds with longer residence time. Our results suggest residence time is an important factor for nitrogen removal in small agricultural ponds as well as large lakes.

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Cheng, Yao, Zheng Mu, Haiyan Wang, Fengxia Zhao, Yu Li, and Lei Lin. "Water Residence Time in a Typical Tributary Bay of the Three Gorges Reservoir." Water 11, no. 8 (2019): 1585. http://dx.doi.org/10.3390/w11081585.

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Tributary bays of the Three Gorges Reservoir (TGR) are suffering from environmental problems, e.g., eutrophication and algae bloom, which could be related to the limited water exchange capacity of the tributary bays. To understand and quantify the water exchange capacity of a tributary bay, this study investigated the water residence time (RT) in a typical tributary bay of TGR, i.e., the Zhuyi Bay (ZB), using numerical simulation and the adjoint method to obtain the RT. The results show that RT of ZB with an annual mean of 16.7 days increases from the bay mouth to the bay top where the maximum can reach 50 days. There is a significant seasonal variation in RT, with higher RT (average 20 days) in spring and autumn and lower RT (average < 5 days) in the summer. The sensitivity experiments show that the TGR water level regulation has a strong influence on RT. The increase in the water level could increase RT of ZB to some extent. Density currents induced by the temperature difference between the mainstream and tributaries play an important role in the water exchange of ZB, while the impacts of the river discharges and winds on RT are insignificant.

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Chalamov, Yanush, Apostol Simitchiev, Ventzislav Nenov, Angel Danev, and Hristina Andreeva. "Effect of propeller use on residence time distribution (rtd) in single-screw cam-flow rice semolina extrusion." BIO Web of Conferences 102 (2024): 03003. http://dx.doi.org/10.1051/bioconf/202410203003.

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The influence of the speed of the feeding (Nf) and main (Nw) screw, the moisture content of the material (W) and the temperature of the die (Tm) on the average residence time (t) and the Peclet number (Pe) in single-screw extrusion of rice semolina using a propeller were investigated. A computer system with a camera was used to continuously read the colorant saturation as a tracer pulsed into the feed zone of the extruder. The differential distribution curves of dwell times were constructed. The responce surface methodology with an orthogonal central compositional plan was used. Regression equations were obtained describing the influence of the selected independent variables on the average residence time (t) and the Peclet number (Pe). It has been found that the use of a propeller increases the mixing capability of the extruder and brings it closer to the ideal mixer.

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Liu, Zhenyu, Yang Li, Changgui Cheng, Peng Lan, and Weili Wu. "Study on Parameter Optimization of Diversion Wall in an Eight-Strand Tundish during Continuous Casting of Billet with High Casting Speed." Processes 10, no. 3 (2022): 555. http://dx.doi.org/10.3390/pr10030555.

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With the increasing demand for high-efficient continuous casting, parameter optimization during high-speed continuous casting is critical. To clarify the changes in flow characteristics in a multistrand tundish and the optimization principles for the diversion wall, a numerical investigation of an eight-strand tundish during continuous casting of billet was carried out in this paper. The simulation results were validated with the physical results of a 1:3 water model experiment. The results show that, for a tundish with the same flow control device, the average residence time and the maximum residence time difference of liquid steel in different strands are significantly reduced with higher casting speed. At different casting speeds, the effect of the hole diameter and deflection angle of diversion wall on the average residence time and the dead region proportion is very minor, while that on the maximum residence time difference of liquid steel in different strands is significant. For a given tundish, to improve the flow uniformity among multiple strands, parameter optimization of diversion wall should be optimized when the casting speed increases. When the casting speed is 4.4 m/min, the hole diameter of the diversion wall is 80 mm, and the deflection angle of the diversion wall is 74°, the flow field parameters of liquid steel in the eight-strand tundish are good, especially flow uniformity among multiple strands.

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Thiele, R., and J. Breme. "Micro- and Macromixing in Polymerization Reactors." International Polymer Processing 3, no. 1 (1988): 48–53. http://dx.doi.org/10.1515/ipp-1988-0004.

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Abstract The paper deals with the influence of the local mixing state on the product properties in a mass styrene-acrylonitrile copolymerization stirred tank reactor in steady state. Experimental investigations at different stirrer speeds have been carried out in a specially constructed bench scale reactor. The idealized models for microfluid and complete segregation were used to calculate the polymer mass fraction, the weight average polymerization degree and the molecular nonuniformity at the outlet of the reactor. The apparatus operated as an “ideally mixed” continuous stirred tank reactor under all chosed conditions as demonstrated by measurements of the residence time distributions. The results are: the segregation model describes the experimentals at low stirrer speeds and the microfluid model is appropriate at high agitator revolutions. Polymer mass fraction, weight average polymerization degree and molecular nonuniformity as functions of average residence time calculated on the basis of both the idealized models indicate intersection points. A high extent of microfluid must not tend to decrease the molecular nonuniformity. The agitator speed can be limited in such a way that it is just sufficiently high to approximate the residence time distribution of an “ideally mixed” continuous stirred tank reactor in order to avoid dead spots and channelling. Segregation is not dangerous for the reactor performance and the product properties.

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DAIGO, Ichiro, Yasunari MATSUNO, Keiichi N. ISHIHARA, and Yoshihiro ADACHI. "Development of Methodology for Analyzing the Average Number of Times of Use and the Average Residence Time of Iron Element in Society by Applying Markov Chain Model." Tetsu-to-Hagane 91, no. 1 (2005): 159–66. http://dx.doi.org/10.2355/tetsutohagane1955.91.1_159.

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English, K. K., R. C. Bocking, and J. R. Irvine. "A Robust Procedure for Estimating Salmon Escapement based on the Area-Under-the-Curve Method." Canadian Journal of Fisheries and Aquatic Sciences 49, no. 10 (1992): 1982–89. http://dx.doi.org/10.1139/f92-220.

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Salmon spawning escapements are estimated using the area-under-the-curve (AUC) method by dividing the integral of the escapement curve by the average residence time of fish in the survey area. We present two forms of the basic AUC method which differ in the procedure used to estimate residence time from the observations of tagged fish during stream surveys. AUC estimates based on "observed residence times" were sensitive to variability in survey timing, observer efficiency, and tag detection, while those based on "total residence times" were more robust. For two coastal streams, escapement estimates based on "observed residence times" were between 1.1, and 6.8 times larger than an independent escapement estimate (from fence counts and mark–recapture data), while estimates based on "total residence times" were generally closer to the independent estimate (0.74–1.51 times the estimate, and within 26% six times out of seven). The consistency of our results under a wide variety of survey conditions, combined with their strong theoretical basis, indicates that an AUC method based on annual estimates of total residence time and observer efficiency is robust. However, the level of survey effort required for these methods would limit their application to high-priority streams or populations.

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Chen, Zhipeng, and Kun Hu. "Solid-liquid Two Phase Flow Simulation on Particle Motion in the Axial Flow Pump." Scientific Journal of Technology 5, no. 3 (2023): 26–30. http://dx.doi.org/10.54691/sjt.v5i3.4480.

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Based on the DEM-CFD method, the solid-liquid two-phase flow in an axial flow pump was simulated, and the velocity and trajectory of particles passing through the impeller and deflector were investigated. It was found that the particles accelerated about 150% after passing through the impeller. Five solid concentration schemes were set up to explore the influence of solid concentration on particle velocity and average residence time. The maximum velocity of particles at different concentrations tended to 10 m/s; The average residence time of particles in low concentration scheme (2%) is 120% of that in other schemes. The research in this paper can be used as a reference to reduce the erosion wear in the pump and enhance the heat transfer effect.

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Espécie, Mariana de A., Rodrigo H. O. Tardin, and Sheila M. Simão. "Degrees of residence of Guiana dolphins (Sotalia guianensis) in Ilha Grande Bay, south-eastern Brazil: a preliminary assessment." Journal of the Marine Biological Association of the United Kingdom 90, no. 8 (2010): 1633–39. http://dx.doi.org/10.1017/s0025315410001256.

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The Guiana dolphin, Sotalia guianensis, is a small delphinid found in coastal areas from northern Honduras to southern Brazil. Little is known about the ecology of this species in several areas of its geographical distribution. In this paper, we present new data about the residency of Guiana dolphins in Ilha Grande Bay, south-eastern Brazil. Boat surveys were conducted at the study area from May 2007 to March 2008. Applying the photo-identification technique, we took pictures of dolphins' dorsal fins, looking for natural markings on them. A total of 17,969 photographs were taken, from which was created a databank of 462 distinct dolphins. Individuals showed different degrees of residency in the bay. More than 50% of the catalogued dolphins were considered non-residents and/or showed a low degree of residence. The average interval between resightings was 35 ± 27.4 days. Animals without markings (calves and juveniles) accounted for 45% (N = 2917) of photographs taken. These results indicate that this population has a fluid structure including different individuals over time. We suggest a possible relationship between the presence of some individuals and local resource availability, such as prey and protected areas.

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Wotton, B. Mike, James S. Gould, W. Lachlan McCaw, N. Phillip Cheney, and Stephen W. Taylor. "Flame temperature and residence time of fires in dry eucalypt forest." International Journal of Wildland Fire 21, no. 3 (2012): 270. http://dx.doi.org/10.1071/wf10127.

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Temperature profiles of flames were measured using arrays of thermocouples on towers located in experimental bushfires of varying intensity, carried out in dry eucalypt forest of different fuel age and structure. In-fire video of flame-front passage and time series data from very fine exposed thermocouples were used to estimate the duration of passage of the main flaming front in these experimental fires. Flame temperature measured at points within the flame was found to vary with height; maximum flame temperature was greater in the tall shrub fuel than in the low shrub fuel sites. A model to estimate flame temperature at any height within a flame of a specific height was developed. The maximum flame temperature observed was ~1100°C near the flame base and, when observation height was normalised by flame height, flame temperature exponentially decreased to the visible flame tip where temperatures were ~300°C. Maximum flame temperature was significantly correlated with rate of spread, fire intensity, flame height and surface fuel bulk density. Average flame-front residence time for eucalypt forest fuels was 37 s and did not vary significantly with fine fuel moisture, fuel quantity or bulk density.

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McClarty, Davis, Maral Ouzounian, Mingyi Tang, et al. "Ascending aortic aneurysm haemodynamics are associated with aortic wall biomechanical properties." European Journal of Cardio-Thoracic Surgery 61, no. 2 (2021): 367–75. http://dx.doi.org/10.1093/ejcts/ezab471.

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Abstract OBJECTIVES The effect of aortic haemodynamics on arterial wall properties in ascending thoracic aortic aneurysms (ATAAs) is not well understood. We aim to delineate the relationship between shear forces along the aortic wall and loco-regional biomechanical properties associated with the risk of aortic dissection. METHODS Five patients with ATAA underwent preoperative magnetic resonance angiogram and four-dimensional magnetic resonance imaging. From these scans, haemodynamic models were constructed to estimate maximum wall shear stress (WSS), maximum time-averaged WSS, average oscillating shear index and average relative residence time. Fourteen resected aortic samples from these patients underwent bi-axial tensile testing to determine energy loss (ΔUL) and elastic modulus (E10) in the longitudinal (ΔULlong, E10long) and circumferential (ΔULcirc, E10circ) directions and the anisotropic index (AI) for each parameter. Nine resected aortic samples underwent peel testing to determine the delamination strength (Sd). Haemodynamic indices were then correlated to the biomechanical properties. RESULTS A positive correlation was found between maximum WSS and ΔULlong rs=0.75, P = 0.002 and AIΔUL (rs=0.68, P=0.01). Increasing maximum time-averaged WSS was found to be associated with increasing ΔULlong (rs=0.73, P = 0.003) and AIΔUL (rs=0.62, P=0.02). Average oscillating shear index positively correlated with Sd (rs=0.73,P=0.04). No significant relationship was found between any haemodynamic index and E10, or between relative residence time and any biomechanical property. CONCLUSIONS Shear forces at the wall of ATAAs are associated with local degradation of arterial wall viscoelastic hysteresis (ΔUL) and delamination strength, a surrogate for aortic dissection. Haemodynamic indices may provide insights into aortic wall integrity, ultimately leading to novel metrics for assessing risks associated with ATAAs.

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Soria, Juan, Lucía Vera-Herrera, Sara Calvo, et al. "Residence Time Analysis in the Albufera of Valencia, a Mediterranean Coastal Lagoon, Spain." Hydrology 8, no. 1 (2021): 37. http://dx.doi.org/10.3390/hydrology8010037.

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The Albufera of Valencia is a coastal lagoon located in the western area of the Mediterranean Sea, in the Iberian Peninsula. It has an area of 23.1 km2 and an average depth of only 1 m, with a maximum depth of 1.6 m. This lagoon is the remnants of an original and more extensive wetland of about 220 km2 which is now mostly dedicated to rice cultivation. Surface water is supplied through several main and many secondary canals for a total of 64 water entry points and three exit points to the sea. It is difficult to evaluate the residence time due to the lack of reliable measurements of the inflow or outflow, as well as continuous measurements. Between 1988 and 2018, several procedures were used, the results of which are outlined in this document. Overall, a decrease in the inflow during these thirty years was observed and, therefore, it can be concluded that the residence time is increasing. There is a temporal variation during the year due to rainfall and cultivation periods. Likewise, the results found that the natural hydrological zoning of the lagoon causes a spatial heterogeneity with small Northern areas with low residence time of 4.7 days, almost on a weekly basis and large Western extensions with high residence time of 222.9 days. It is impossible to know this information if individual flow measurements are not taken from each of the main watercourses.

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Zheng, Lei, Ai Zhong Ding, De Chuan Kong, and Li Rong Cheng. "Hydraulic Characteristics of a Pilot-Scale Vertical Subsurface Flow Constructed Wetland." Advanced Materials Research 356-360 (October 2011): 2451–58. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.2451.

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The hydraulic characteristics of constructed wetland are vital to its performance for pollutant removal. Hydraulic characteristics of a pilot scale vertical flow constructed wetland were studied by tracer experiments with the method of moments (MoM) analyzing. From the residence-time distribution (RTD) of tracer during the experiment, the mean detention time, average water velocity and dispersion coefficients were obtained for the constructed wetland. The results showed that the mean residence time was approximately 15% shorter than nominal residence time indicating 85% of total available pore volume was active in pollutant removal processes. The two peaks observed on the RTD curves suggested short-circuiting flows or dead zones exist in the constructed wetland. The relatively large Peclet number of 11.8 suggested that dispersive processes dominated in the tracer movement. Comparison of tracer profiles at different sampling locations indicated that large amount of tracer transported through the upper portion of the constructed wetland.

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Corrêa, J. L. G., D. R. Graminho, M. A. Silva, and S. A. Nebra. "The cyclonic dryer: a numerical and experimental analysis of the influence of geometry on average particle residence time." Brazilian Journal of Chemical Engineering 21, no. 1 (2004): 103–12. http://dx.doi.org/10.1590/s0104-66322004000100011.

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Zhang, Binglong, Fuhai Liu, Rong Zhu, and Jinfeng Zhu. "Effects of Multiple-Hole Baffle Arrangements on Flow Fields in a Five-Strand Asymmetric Tundish." Materials 13, no. 22 (2020): 5129. http://dx.doi.org/10.3390/ma13225129.

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This paper reports on the re-engineering of standard five-strand tundish designs into a five-strand asymmetric tundish, which resulted in a non-uniform rate and bias for each strand. We sought to improve the casting conditions by optimizing the liquid steel flow-field in the tundish. Both a water modelling experiment and a numerical simulation were performed to analyze the flow-field according to various diversion hole diameters and injection angles. The results showed that the average residence time decreased as the diameter of the diversion holes increased. As the injection angle was increased, the average residence time initially decreased and then increased. The liquid steel from the ladle shroud rapidly extended to the #2 and #3 strands in the original tundish, which reduced the likelihood of inclusion collision and coalescence.

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Meijie, Z., G. Huazhi, H. Ao, Z. Hongxi, and D. Chengji. "Numerical simulation and industrial practice of inclusion removal from molten steel by gas bottom-blowing in continuous casting tundish." Journal of Mining and Metallurgy, Section B: Metallurgy 47, no. 2 (2011): 137–47. http://dx.doi.org/10.2298/jmmb110120006m.

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Gas blowing at the bottom of tundish is an efficient metallurgy technique in clean steelmaking. In this paper, the removal of small size inclusions in the gas bottom-blowing tundish was studied by numerical simulation and industrial practice. The residence time distribution (RTD) of molten steel in the tundish was calculated by mathematical modeling. The content of small size inclusions in the slab was analyzed using a oxygen probing and metallographic images. The results show that the molten steel characteristics obviously change when applied gas bottom-blowing, the average residence time of molten steel in the tundish prolongs more than 100s and the dead volume fraction decreases about 5%. Therefore, the removal efficiency of small size inclusions greatly increases because of bubbles attachment and long moving path. Industrial experiment results show that the average inclusions content of less than 20?m decreases more than 24%, the average overall oxygen content decreases about 15% when controlling the reasonable blowing parameters.

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Stepanov, Borivoj, Ivan Pesenjanski, and Momcilo Spasojevic. "Scandinavian baffle boiler design revisited." Thermal Science 19, no. 1 (2015): 305–16. http://dx.doi.org/10.2298/tsci130508070s.

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The aim of this paper is to examine whether the use of baffles in a combustion chamber, one of the well-known low-cost methods for the boiler performance improvement, can be enhanced. Modern day tools like computational fluid dynamics were not present at the time when these measures were invented, developed and successfully applied. The objective of this study is to determine the influence of location and length of a baffle in a furnace, for different mass flows, on gas residence time. The numerical simulations have been performed of a simple Scandinavian stove like furnace. The isothermal model is used, while air is used as a medium and turbulence is modeled by realizable k-epsilon model. The Lagrange particle tracking is used for the residence time distribution determination. The statistical analysis yielded the average residence time. The results of the computational fluid dynamics studies for different baffle positions, dimensions and flow rates show from up to 17% decrease to up to 13 % increase of residence time. The conclusion is that vertical position of the baffle is the most important factor, followed by the length of the baffle, while the least important showed to be the mass flow.

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Cao, Yongsheng, Guanglin Zhang, Demin Li, Lin Wang, and Zongpeng Li. "Online Energy Management and Heterogeneous Task Scheduling for Smart Communities with Residential Cogeneration and Renewable Energy." Energies 11, no. 8 (2018): 2104. http://dx.doi.org/10.3390/en11082104.

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With the development of renewable energy technology and communication technology in recent years, many residents now utilize renewable energy devices in their residences with energy storage systems. We have full confidence in the promising prospects of sharing idle energy with others in a community. However, it is a great challenge to share residents’ energy with others in a community to minimize the total cost of all residents. In this paper, we study the problem of energy management and task scheduling for a community with renewable energy and residential cogeneration, such as residential combined heat and power system (resCHP) to pay the least electricity bill. We take elastic and inelastic load demands into account which are delay intolerant and delay tolerant tasks in the community. The minimum cost problem of a non-cooperative community is extracted into a random non-convex optimization problem with some physical constraints. Our objective is to minimize the time-average cost for each resident in the community, including the cost of the external grid and natural gas. The Lyapunov optimization theory and a primal-dual gradient method are adopted to tackle this problem, which needs no future data and has low computational complexity. Furthermore, we design a cooperative renewable energy sharing algorithm based on State-action-reward-state-action (Sarsa) Algorithm, in the condition that each residence in the community is able to communicate with its neighbors by a central controller. Finally, extensive simulations are presented to validate the proposed algorithms by using practical data.

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John, Sebin, K. R. Muraleedharan, C. Revichandran, S. Abdul Azeez, G. Seena, and Pierre W. Cazenave. "What Controls the Flushing Efficiency and Particle Transport Pathways in a Tropical Estuary? Cochin Estuary, Southwest Coast of India." Water 12, no. 3 (2020): 908. http://dx.doi.org/10.3390/w12030908.

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Estuaries with poor flushing and longer residence time retain effluents and pollutants, ultimately resulting in eutrophication, a decline in biodiversity and, finally, deterioration of water quality. Cochin Estuary (CE), southwest coast of India, is under the threat of nutrient enrichment by the anthropogenic interventions and terrestrial inputs through land runoff. The present study used the FVCOM hydrodynamic model coupled with the Lagrangian particle module (passive) to estimate the residence time and to delineate site-specific transport pathways in the CE. The back and forth movements and residence time of particles was elucidated by using metrics such as path length, net displacement and tortuosity. Spatio-temporal patterns of the particle distribution in the CE showed a similar trend during monsoon and post-monsoon with an average residence time of 25 and 30 days, respectively. During the low river discharge period (pre-monsoon), flood-ebb velocities resulted in a minimum net transport of the water and longer residence time of 90 days compared to that of the high discharge period (monsoon). During the pre-monsoon, particle released at the southern upstream (station 15) traversed a path length of 350 km in 90 days before being flushed out through the Fortkochi inlet, where the axial distance was only 35 km. This indicates that the retention capacity of pollutants within the system is very high and can adversely affect the water quality of the ecosystem. However, path length (120 km) and residence time (7.5 days) of CE were considerably reduced during the high discharge period. Thus the reduced path length and the lower residence time can effectively transport the pollutants reaching the system, which will ultimately restore the healthy ecosystem. This is a pioneer attempt to estimate the flushing characteristics and residence time of the CE by integrating the hydrodynamics and Lagrangian particle tracking module of FVCOM. This information is vital for the sustainable management of sensitive ecosystems.

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Platonov, Dmitriy, Andrey Sentyabov, Sergey Shtork, Sergey Skripkin, and Dmitriy Dekterev. "NUMERICAL SIMULATION OF THE FLOW WITH DISPERSE PHASE IN A TANGENTIAL VORTEX CHAMBER." Eurasian Journal of Mathematical and Computer Applications 13, no. 1 (2025): 100–107. https://doi.org/10.32523/2306-6172-2025-13-1-100-107.

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The flow with a disperse phase in a tangential vortex chamber at high swirl numbers was studied using a numerical methods. The swirling flow is created using nozzles directed at an angle to the chamber axis. The numerical flow model was based on computational fluid dynamics methods and described the turbulent flow of water. Turbulence was simulated using the large eddy simulation method. Based on the results of single-phase flow simulation, particle motion was calculated using the Lagrange approach. The results of the single-phase flow simulation are consistent with the data from the corresponding experimental studies. The movement of particles depends significantly on their density. For massless particles, the average residence time of the particles is noticeably lower for a higher swirl number. The residence time of heavy particles is 1.5 - 2 times higher than the similar residence time of massless particles. At the same time, most of the heavy particles do not leave the tangential chamber and are deposited.

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Bannister, Edward J., Mike Jesson, Nicholas J. Harper, et al. "Residence times of air in a mature forest: observational evidence from a free-air CO₂ enrichment experiment." Atmospheric Chemistry and Physics 23, no. 3 (2023): 2145–65. http://dx.doi.org/10.5194/acp-23-2145-2023.

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Abstract. In forests, the residence time of air – the inverse of first-order exchange rates – influences in-canopy chemistry and the exchanges of momentum, energy, and mass with the surrounding atmosphere. Accurate estimates are needed for chemical investigations of reactive trace species, such as volatile organic compounds, some of whose chemical lifetimes are on the order of average residence times. However, very few observational residence-time estimates have been reported. Little is known about even the basic statistics of real-world residence times or how they are influenced by meteorological variables such as turbulence or atmospheric stability. Here, we report opportunistic investigations of residence time of air in a free-air carbon dioxide enrichment (FACE) facility in a mature, broadleaf deciduous forest with canopy height of hc≈25 m. Using nearly 50 million FACE observations, we find that median daytime residence times in the tree crowns range from around 70 s when the trees are in leaf to just over 34 s when they are not. Residence times increase with increasing atmospheric stability, as does the spread around their central value. Residence times scale approximately with the reciprocal of the friction velocity, u∗. During some calm evenings in the growing season, we observe distinctly different behaviour: pooled air being sporadically and unpredictably vented – evidenced by sustained increases in CO2 concentration – when intermittent turbulence penetrates the canopy. In these conditions, the concept of a residence time is less clearly defined. Parameterisations available in the literature underestimate turbulent exchange in the upper half of forest crowns and overestimate the frequency of long residence times. Robust parameterisations of residence times (or, equivalently, fractions of emissions escaping the canopy) may be generated from inverse-gamma distributions, with the parameters 1.4≤α≤1.8 and β=hc/u∗ estimated from widely measured flow variables. In this case, the mean value for τ becomes formally defined as τ‾=β/(α-1). For species released in the canopy during the daytime, chemical transformations are unlikely unless the reaction timescale is on the order of a few minutes or less.

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Tian, Lijun, Yongli Gao, Guang Yang, et al. "Isotopic tracers of sources of water for springs from the Edwards Aquifer, Central Texas, USA." Hydrology Research 52, no. 3 (2021): 787–803. http://dx.doi.org/10.2166/nh.2021.011.

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Abstract The Edwards Aquifer (EA) in Central Texas provides water supply for over two million people and contains springs that are hydrologically and ecologically important to the region. The residence time of groundwater in the EA ranges from a few days to many thousands of years, since water in the aquifer is contained and transported within both matrix porosity and large conduits. In this study, stable isotopes of water from five springs are investigated for tracing the origin of water and hydrological processes in the EA system during 2017–2019. There is a quick response of the isotopic signals measured at these springs to changes in the isotopic compositions of precipitation. By utilizing an isotope mixing model, we have identified sources of water for these springs with a bi-modal distribution of groundwater supply in the EA: water supplied from deep groundwater with a longer residence time (an average of 67%) and supplemental epikarst interflow with a shorter residence time (an average of 33%). The evolution of hydrochemical water types from HCO3–Ca to HCO3·Cl–Ca·Mg along the EA flowpaths indicates that inputs from epikarst interflow are greater in springs within the artesian zone than the springs within the contributing zone.

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Płaczkowska, Eliza, Janusz Siwek, Karolina Maciejczyk, Karolina Mostowik, Magdalena Murawska, and Bartłomiej Rzonca. "Groundwater capacity of a flysch-type aquifer feeding springs in the Outer Eastern Carpathians (Poland)." Hydrology Research 49, no. 6 (2018): 1946–59. http://dx.doi.org/10.2166/nh.2018.200.

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Abstract The aim of the study is to assess the capacity of the flysch aquifer feeding springs in the Outer Eastern Carpathians using spring recession curves. The four selected springs are located in an area generally believed to be poor in groundwater. However, the selected springs were characterized by remarkably high average discharge of 3.2–9.6 L s−1. Recession coefficients were estimated which enabled an aquifer capacity and groundwater residence time assessment. Despite similarities in elevation, precipitation, and lithology in the study area, a substantial variation in the recession coefficients and aquifer parameters was found. The average aquifer capacity of groundwater subsystems strongly varied in the small study area (4.9–49 m3 × 103). The mean groundwater residence time varied from 11 days to 50 days depending on the volume of groundwater drained by the springs. Differences in discharge, recession coefficients, groundwater capacity, and residence time were related to recharge areas of different size. Simple relationships between the topographic catchment areas of springs and their hydrologic parameters can become altered by local structural features: faults and fissures. The study demonstrates that tectonically produced structures may facilitate a larger supply of groundwater and the occurrence of high-discharge springs in a given area.

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Journal articles on the topic 'Average residence time'

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