Parameters influencing the droplet formation in a focusing microfluidic channel

In the present work a detailed numerical study of the parameters influencing the droplet formation in a flow-focusing microfluidic device are made. First, an extensive verification of the simulations with data from the literature is carried out. Influence of parameters like viscosity and inflow velocity are compared with the results from literature showing a good agreement. Some differences are attributed to the different numerical techniques used: in the present work a pure volume-of-fluid method is used, while in the reference study this method is combined with the level-set method. As a second step of the verification of the present model, a comparison with experimental data from the literature was carried out which shows a very good agreement. After the verification was completed, eight new simulations are carried out covering a wide range of velocities of the continuous phase uc. In these simulations the velocity of the discrete phase ud remains unchanged. The variation of the continuous phase velocity reveals that with increasing the value of uc, respectively the value of the capillary number Ca, the droplet length reaches a point of saturation, i.e. a point where the droplet length does not decrease any more. For the present setup this saturation occurs for Ca > 0,03. On the other hand, when the velocity of the continuous phase goes towards very low values (Ca < 0,01 for the present setup), the droplet size increases significantly. Further, it was found that for increasing capillary numbers Ca above a value around 0,015 for water/oil and above 0,025 for water + 40% glycerol / oil systems, a transmission from the dripping towards the jetting regimes of droplet formation occurs. It was shown that when the viscosity of the continuous phase increases, higher total pressure jumps in the droplet occur, also leading to the formation of smaller droplets

Identifying non-stationary and long-term river-aquifer interactions as a response to large climatic patterns and anthropogenic pressures using wavelet analysis (Mancha Oriental Aquifer, Spain)

[EN] The objective of this study was to analyse periodicities and the long-term variability of monthly Jucar River-Mancha Oriental Aquifer interactions (RAI) and regionally measured precipitation (PP) with special focus on the correlations between these local hydrological variables and the large climatic patterns governing the Iberian Peninsula, represented by their teleconnection indices - the North Atlantic Oscillation index (NAOi) and the Western Mediterranean Oscillation index (WeMOi). To that end, wavelet analysis has been applied since it not only provides insight into the time-series dynamics but also permits statistical interpretation and correlation analysis. As a result, several periodicities have been detected: intermittent semi-annual periodicity in PP and the NAOi and annual periodicity in the RAI, NAOi and WeMOi time series. Long cycles (approximately 14 years) are also observed in the PP and WeMOi time series. The cross-wavelet spectra show a correlation between the RAI and the rest of the variables on the semi-annual and the annual scales, while wavelet coherence detects common behaviour with longer cycles - 5-6 years between the NAOi and the RAI and cycles of both 1-5 years and 7-10 years between PP and the RAI. Furthermore, results show that the periodicities in the teleconnection indices and precipitation propagate into the RAI with certain lead times: 3 months between the RAI and PP and 6 months between the RAI and the NAOi. The results indicate that the detected periodicities and the coherence between the studied variables could have applications in strategic planning on a river basin scale, taking into account the propagation times and the frequency scale. This methodological approach can be applied into strategic water resource planning independently of the geographical location of the hydrogeological system, the basin size and the climate region.Special thanks go to the Júcar Water Authority (CHJ) and stakeholders (JCRMO) in the Mancha Oriental System for providing the necessary information. The content of this report does not represent the view of CHJ and JCRMO. This work has been funded by the research projects CGL2017-87216-C4-2-R from the National Research Program I + D + i (FEDER/Ministerio de Ciencia, Investigación y Universidades) and SBPLY/17/180501/000296 from the National Research Program I + D + i of the Junta of Communities of Castile-La Mancha. We would also like to thank Christine Laurin for the English copy editing and valued comments.Dountcheva, I.; Sanz, D.; Cassiraga, EF.; Galabov, V.; Gómez-Alday, JJ. (2020). Identifying non-stationary and long-term river-aquifer interactions as a response to large climatic patterns and anthropogenic pressures using wavelet analysis (Mancha Oriental Aquifer, Spain). Hydrological Processes. 34(25):5134-5145. https://doi.org/10.1002/hyp.13934S513451453425Butler, J. J., Whittemore, D. O., Wilson, B. B., & Bohling, G. C. (2018). Sustainability of aquifers supporting irrigated agriculture: a case study of the High Plains aquifer in Kansas. Water International, 43(6), 815-828. doi:10.1080/02508060.2018.1515566Cassiraga E. Sanz D. Castaño S. Álvarez O. &Sahuquillo A.(2013).Modelo de flujo subterráneo de los acuíferos de la Mancha oriental y sus relaciones con el río Júcar [groundwater model flow of the Mancha oriental aquifer and their relations with the Júcar River]. Unpublished report (pp 77). Confederación Hidrográfica del Júcar.Castaño, S., Sanz, D., & Gómez-Alday, J. J. (2013). Sensitivity of a Groundwater Flow Model to Both Climatic Variations and Management Scenarios in a Semi-arid Region of SE Spain. Water Resources Management, 27(7), 2089-2101. doi:10.1007/s11269-013-0277-4Charlier, J.-B., Ladouche, B., & Maréchal, J.-C. (2015). Identifying the impact of climate and anthropic pressures on karst aquifers using wavelet analysis. Journal of Hydrology, 523, 610-623. doi:10.1016/j.jhydrol.2015.02.003Confederación Hidrográfica de Júcar. (2005).Protocol for action in situations of alert and eventual drought (in Spanish). Retrieved fromhttps://www.chj.es/es-es/medioambiente/gestionsequia/Documents/Plan%20Especial%20Alerta%20y%20Eventual%20Sequia/Protocolo_CHJ_dic2005_JG.pdf.Confederación Hidrográfica de Júcar. (2010).Post‐drought report Paragraph 10 PES (in Spanish). Retrieved fromhttps://www.chj.es/es-es/medioambiente/gestionsequia/Documents/Informes%20Seguimiento/INFORME_POST_SEQUIA_2010.pdf.Confederación Hidrográfica de Júcar. (2015).Júcar River basin management plan 2015–2021 (in Spanish). Júcar River Basin Authority (Demarcación hidrográfica del Júcar).Confederación Hidrográfica del Júcar. Ministry of the Environment Madrid.Commission of the European Communities (CEC). (2000).Directive of the European Parliament and of the council establishing a framework for community action in the field of water policy: Joint text approved by the conciliation committee. 1997/0067(cod) C5‐0347/00.Daubechies, I. (1992). Ten Lectures on Wavelets. doi:10.1137/1.9781611970104Gómez-Martínez, G., Pérez-Martín, M. A., Estrela-Monreal, T., & del-Amo, P. (2018). North Atlantic Oscillation as a Cause of the Hydrological Changes in the Mediterranean (Júcar River, Spain). Water Resources Management, 32(8), 2717-2734. doi:10.1007/s11269-018-1954-0Grinsted, A., Moore, J. C., & Jevrejeva, S. (2004). Application of the cross wavelet transform and wavelet coherence to geophysical time series. Nonlinear Processes in Geophysics, 11(5/6), 561-566. doi:10.5194/npg-11-561-2004Holman, I. P., Rivas-Casado, M., Bloomfield, J. P., & Gurdak, J. J. (2011). Identifying non-stationary groundwater level response to North Atlantic ocean-atmosphere teleconnection patterns using wavelet coherence. Hydrogeology Journal, 19(6), 1269-1278. doi:10.1007/s10040-011-0755-9Hurrell J. W. Kushnir Y. Ottersen G. &Visbeck M.(2003).Preface.The North Atlantic Oscillation:Climatic Significance and Environmental Impact Geophysical Monograph Series: Vii‐Viii. Retrieved fromhttps://doi.org/10.1029/gm134p0viiJones, P. D., Davies, T. D., Lister, D. H., Slonosky, V., Jónsson, T., Bärring, L., … Beck, C. (1999). Monthly mean pressure reconstructions for Europe for the 1780–1995 period. International Journal of Climatology, 19(4), 347-364. doi:10.1002/(sici)1097-0088(19990330)19:43.0.co;2-sJones, P. D., Jonsson, T., & Wheeler, D. (1997). Extension to the North Atlantic oscillation using early instrumental pressure observations from Gibraltar and south-west Iceland. International Journal of Climatology, 17(13), 1433-1450. doi:10.1002/(sici)1097-0088(19971115)17:133.0.co;2-pKomasi, M., & Sharghi, S. (2019). Recognizing factors affecting decline in groundwater level using wavelet-entropy measure (case study: Silakhor plain aquifer). Journal of Hydroinformatics, 21(3), 510-522. doi:10.2166/hydro.2019.111Labat, D., Ababou, R., & Mangin, A. (2001). Introduction of Wavelet Analyses to Rainfall/Runoffs Relationship for a Karstic Basin: The Case of Licq-Atherey Karstic System (France). Ground Water, 39(4), 605-615. doi:10.1111/j.1745-6584.2001.tb02348.xLópez J. &Frances F.(2010).Influence of the North Atlantic oscillation and the western Mediterranean oscillation in the maximum flow events in Spain. Paper presented at: International workshop advances in statistical hydrology.Lopez-Bustins, J.-A., Martin-Vide, J., & Sanchez-Lorenzo, A. (2008). Iberia winter rainfall trends based upon changes in teleconnection and circulation patterns. Global and Planetary Change, 63(2-3), 171-176. doi:10.1016/j.gloplacha.2007.09.002Markovic, D., & Koch, M. (2013). Long-term variations and temporal scaling of hydroclimatic time series with focus on the German part of the Elbe River Basin. Hydrological Processes, 28(4), 2202-2211. doi:10.1002/hyp.9783Ministerio de Medio Ambiente (MMA). (2007).Orden MAM/698/2007 de 21 de Marzo Por la Que se Aprueban los Planes Especiales de Actuación en Situaciones de Alerta y Eventual Sequía en los Ámbitos de los Planes Hidrológicos de Cuencas Intercomunitarias. Boletín Oficial del Estado. Retrieved fromhttps://www.boe.es/eli/es/o/2007/03/21/mam698Mukherjee, A., Saha, D., Harvey, C. F., Taylor, R. G., Ahmed, K. M., & Bhanja, S. N. (2015). Groundwater systems of the Indian Sub-Continent. Journal of Hydrology: Regional Studies, 4, 1-14. doi:10.1016/j.ejrh.2015.03.005Ortega-Gómez, T., Pérez-Martín, M. A., & Estrela, T. (2018). Improvement of the drought indicators system in the Júcar River Basin, Spain. Science of The Total Environment, 610-611, 276-290. doi:10.1016/j.scitotenv.2017.07.250Osborn, T. J. (2006). Recent variations in the winter North Atlantic Oscillation. Weather, 61(12), 353-355. doi:10.1256/wea.190.06Osman, Y. Z., & Bruen, M. P. (2002). Modelling stream–aquifer seepage in an alluvial aquifer: an improved loosing-stream package for MODFLOW. Journal of Hydrology, 264(1-4), 69-86. doi:10.1016/s0022-1694(02)00067-7Ouachani, R., Bargaoui, Z., & Ouarda, T. (2011). Power of teleconnection patterns on precipitation and streamflow variability of upper Medjerda Basin. 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Hydrological Processes, 27(14), 2021-2031. doi:10.1002/hyp.9356Sanz D.(2005).Contribución a la caracterización geométrica de las unidades hidrogeológicas que integran el sistema de acuíferos de la Mancha Oriental (Contribution to the geometric characterization of the hydrogeological units of the La Mancha Oriental aquifer system) Memoria para optar al grado de doctor (PhD thesis). Universidad Complutense de Madrid Facultad de Ciencias Geológicas Departamento de Geodinámica.Sanz, D., Castaño, S., Cassiraga, E., Sahuquillo, A., Gómez-Alday, J. J., Peña, S., & Calera, A. (2011). Modeling aquifer–river interactions under the influence of groundwater abstraction in the Mancha Oriental System (SE Spain). Hydrogeology Journal, 19(2), 475-487. doi:10.1007/s10040-010-0694-xSanz, D., Gómez-Alday, J. J., Castaño, S., Moratalla, A., De las Heras, J., & Martínez-Alfaro, P. E. (2009). Hydrostratigraphic framework and hydrogeological behaviour of the Mancha Oriental System (SE Spain). 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Assessing 1D hydrodynamic modeling of Júcar River behavior in Mancha Oriental Aquifer domain (SE Spain)

[EN] In times of population growth, climate change, and increasing water scarcity around the world, it is important to take an objective look at water, a fundamental resource for life. Hydrodynamic modeling makes possible the research of different aspects of the water cycle and the evaluation of different hydrological and hydrogeological forecasting scenarios in the short and medium terms. The present research offers a more detailed scope at the hydrodynamic processes and their space-time distributions on a UE pilot in the Jucar River Basin, providing a calibrated and validated hydrodynamic model of 121 km river reach for 45 years period (1974-2019) on a daily scale. The obtained information is about discharge and water depths along the Jucar River reach within the hydrogeological boundaries of the Mancha Oriental Aquifer (MOA). The river-aquifer interactions have been represented as dynamic boundary conditions expressed as a difference between observed discharges measured in 3 gauging stations. The obtained calibration error performance evaluations of observed and simulated values cover two periods, according to observed data availability from gauging station 08036 with resulting R-2 for both discharges and water depths over 0.96. The model validation results were obtained for a different gauge 08132 and the determination coefficients R-2 also perform very well with value of 0.90. The model developed might be useful for decision making in water resources management and can be used to generate simulated time series of water depths, levels, discharges, and velocities in reaches where gauging measurements are not available with a desired space-time resolution (from meter/second to kilometer/month). Estimation of critical discharge value (1.973 m(3)s(-1)) for system equilibrium, based on the balance between losing and gaining sub-reaches of the river, is also made with a statistical significance at 95% for hydrologic years 2007-2010, period influenced by restrictions in groundwater withdrawals. The results of the present research are important for the proper and objective management of the scarce water resources on a watershed scale in Jucar River Basin, a complex case study representing semiarid climate, growing anthropogenic pressures, and complex river-aquifer interactions. The used approach of dynamic representation of the river-aquifer interactions as distributed source boundary condition in the one-dimensional hydrodynamic model might be applied in another study case on similar scale.This work was funded by the following research projects CGL 2017 87216 C 4 2 R Programa Nacional de Investigación I+D+i (FEDER/Ministerio de Ciencia, Investigación y Universidades) SBPLY/17 180501 000296 Programa Nacional de Investigación I+D+i de la Junta de Comunidades de Castilla La Mancha.Dountcheva, I.; Sanz, D.; Penchev, P.; Cassiraga, EF.; Galabov, V.; Gómez-Alday, JJ. (2023). Assessing 1D hydrodynamic modeling of Júcar River behavior in Mancha Oriental Aquifer domain (SE Spain). Water. 15(3):1-21. https://doi.org/10.3390/w1503048512115