The system of metrological provision of the Russian Federation in the field of measurement of gas flows in a vacuum and its future development

The article provides information about the state of the metrological provision in the field of gas flow measurements in a vacuum. The researchers describe the need to build and improve a system of metrological provision in the field of measuring gas flows in a vacuum. There is information about the work on the creation of a piston flow meter as a national standard for gas flow in a vacuum, taking place in the research department of the state standards in the field of pressure measurements of the D. I. Mendeleyev Institute for Metrology VNIIM.

Long-term Temporal Variation of Mean Residence Time in Spring and Groundwater After Thinning at a Forested Headwater Catchment

<p>Treatments on plantation forests, such as thinning, have a significant effect on the quality and quantity of water resources in the watersheds in Japan. However, few studies have performed intensive observations regarding the effects of thinning on the groundwater flow process with combined use of tracers, specially over a long period of time.</p><p>In this study, stable isotope analysis and hydrological observations were applied to investigate the temporal variation of spring water and groundwater mean residence time in a small watershed at Mount Karasawa, Tochigi Prefecture, Japan. We have monitored the research area since 2010, with periodical sampling once a month for 9 years, with a lack of data in some years after the thinning.  We analyzed the date for three different time periods, those are: Before Thinning, from July 2010 to September 2011, Soon After Thinning, from November 2011 to October 2013 and Long After Thinning, from September 2017 to August 2019.</p><p>The mean residence time of spring water and groundwater were evaluated by using the stable isotopes of hydrogen and oxygen as tracers, then estimating their d-excess variations using two Lumped-Parameter Models, Exponential-Piston Flow Model and Dispersion Model. The SF<sub>6</sub> concentrations were used as an Apparent Age analysis for determination of the model’s parameters. Both models show a tendency of the mean residence time getting older Soon After Thinning and then getting younger again Long After Thinning.</p><p>According to a selection of the best model for this area, the Exponential-Piston Flow Model shows that the spring water mean residence time was 25 months Before Thinning, 30 months Soon After Thinning and 26 months Long After Thinning; the groundwater at 15m deep mean residence time was 39 months Before Thinning, 46 months Soon After Thinning and 38 months Long After Thinning and the groundwater at 30m deep mean residence time was 38 months Before Thinning, 47 months Soon After Thinning and 45 months Long After Thinning. These results suggest that Soon After Thinning there is a reduction of forest interception and tree evapotranspiration, leading to an increase in infiltration and groundwater storage. Then, Long After Thinning, the forest interception and tree evapotranspiration rise back again with the recovery of the understory vegetation, which leads to a decrease in infiltration and groundwater storage.</p>

Effects of Deforestation on Water Flow in the Vadose Zone

The effects of land use change on the occurrence and frequency of preferential flow (fast water flow through a small fraction of the pore space) and piston flow (slower water flow through a large fraction of the pore space) are still not fully understood. In this study, we used a five year high resolution soil moisture monitoring dataset in combination with a response time analysis to identify factors that control preferential and piston flow before and after partial deforestation in a small headwater catchment. The sensor response times at 5, 20 and 50 cm depths were classified into one of four classes: (1) non-sequential preferential flow, (2) velocity based preferential flow, (3) sequential (piston) flow, and (4) no response. The results of this analysis showed that partial deforestation increased sequential flow occurrence and decreased the occurrence of no flow in the deforested area. Similar precipitation conditions (total precipitation) after deforestation caused more sequential flow in the deforested area, which was attributed to higher antecedent moisture conditions and the lack of interception. At the same time, an increase in preferential flow occurrence was also observed for events with identical total precipitation. However, as the events in the treatment period (after deforestation) generally had lower total, maximum, and mean precipitation, this effect was not observed in the overall occurrence of preferential flow. The results of this analysis demonstrate that the combination of a sensor response time analysis and a soil moisture dataset that includes pre- and post-deforestation conditions can offer new insights in preferential and sequential flow conditions after land use change.

Model of layered flow of viscous-plastic Bingham fluid in the extruder channel

The analysis is carried out and the presence of a zone of a piston flow, which has a significant influence both on the process of extrusion, and on the determination of the discharge-pressure characteristics of the screw, is established. It is noted that the effective viscosity has a physical meaning if the shear rate to which it corresponds is indicated. The effective viscosity is considered to consist of two components: the plastic viscosity corresponding to the viscosity of the Newtonian fluid and the structural viscosity that characterizes the shear resistance caused by the tendency of the solid particles contained in the Bingham liquid to form a structure. The effective viscosity is introduced into many hydrodynamic equations if the shear rate to which it corresponds is known. In the auger channel there are zones of forced flow created by the dynamic shear stress and the reverse flow of the head resistance created by the overpressure. The shear rate in the auger channel is marked by considerable heterogeneity and determines the complex nature of the shear deformation of the material during extrusion. Regardless of the pressure amplitude, the rigid core can not completely disappear, because for very small dimensions of the nucleus the pressure value must be very large, and with the disappearance of the plastic flow it must become infinite. Thus, the dependence of the shear stress on the shear rate for the flow of a Bingham viscoplastic fluid is always nonlinear for any values of the shear rate. An important element in the calculation of the discharge-pressure characteristics of the extrusion process is the localization of the plastic flow in the screw channel. As a result of the analysis of the model of the layered flow of viscoplastic Bingham liquid in the extruder channel, it is established that there is a zone of piston flow that exerts a significant influence both on the process of extrusion and on the determination of the discharge and pressure characteristics of the screw.

Tracking the direct impact of rainfall on groundwater at Mt. Fuji by multiple analyses including microbial DNA

A total of 2 to 3 million tons of spring water flushes out from the foot of Mt. Fuji, the largest volcanic mountain in Japan. Based on the concept of piston flow transport, residence time of stored groundwater at Mt. Fuji was estimated at ∼ 15–30 years by the 36Cl ∕ Cl ratio (Tosaki et al., 2011). This range, however, represents the average residence time of groundwater that was mixed before it flushed out. To elucidate the route of groundwater in a given system, we determined signatures of direct impacts of rainfall on groundwater, using microbial, stable isotopic (δ18O), and chemical analyses (concentration of silica). Chemical analysis of the groundwater gave an average value of the water, which was already mixed with waters from various sources and routes in the subsurface environment. The microbial analysis suggested locations of water origin and paths. In situ observation during four rainfall events revealed that the stable oxygen isotopic signature obtained from spring water (at 726 m a.s.l., site SP-0 m) and shallow groundwater (at 150 m a.s.l., site GW-42 m), where the average recharge height from rainfall was 1700–1800 m, became greater than values observed prior to a torrential rain producing more than 300 mm of precipitation. The concentration of silica decreased after this event. In addition, the abundance of Bacteria in spring water increased, suggesting the influence of heavy rain. Such changes did not appear when rainfall was less than 100 mm per event. The above findings indicate a rapid flow of rain through the shallow part of the aquifer, which appeared within a few weeks of torrential rain extracting abundant microbes from soil in the studied geologic setting. Interestingly, we found that after the torrential rain, the abundance of Archaea increased in the deep groundwater at site GW-550 m, ∼ 12 km downstream of SP-0 m. However, chemical parameters did not show any change after the event. This suggests that strengthened piston flow caused by the heavy rain transported archaeal particles from the geologic layer along the groundwater route. This finding was supported by changes in constituents of Archaea, dominated by Halobacteriales and Methanobacteriales, which were not seen from other observations. Those two groups of Archaea are believed to be relatively tightly embedded in the geologic layer and were extracted from the environment to the examined groundwater through enforced piston flow. Microbial DNA can thus give information about the groundwater route, which may not be shown by analysis of chemical materials dissolved in the groundwater.

Tracking the direct impact of rainfall on groundwater at Mt. Fuji by multiple analyses including microbial DNA

A two to three million tons of spring water flushes out from the foot of Mt. Fuji, the largest volcanic mountain in Japan. Based on the concept of piston flow transport, residence time of stored groundwater at Mt. Fuji was estimated at ~ 15–30 years by the 36Cl / Cl ratio (Tosaki et al., 2011). This range, however, represents the average residence time of groundwater that was mixed before it flushed out. To elucidate the route of groundwater in a given system, we determined signatures of direct impacts of rainfall on groundwater, using microbial, and stable isotopic (delta 18O), and chemical analyses (concentration of silica). Chemical analysis of the groundwater gave an average value of the water, which was already mixed with waters from various sources and routes in the subsurface environment. The microbial analysis suggested locations of water origin and paths. In situ observation during four rainfall events revealed that the stable oxygen isotopic signature obtained from spring water (at 726 m a.s.l., site SP-0m) and shallow groundwater (at 150 m a.s.l., site GW-42m), where the average recharge height from rainfall was 1500–1800 m, became greater than values observed prior to a torrential rain producing more than 300 mm of precipitation. The concentration of silica decreased after this event. In addition, the abundance of Bacteria in spring water increased, suggesting the influence of the heavy rain. Such changes did not appear when rainfall was less than 100 mm per event. The above findings indicate a rapid flow of rain through the shallow part of the aquifer, which appeared within a few weeks of the torrential rain extracting abundant microbes from soil in the studied geologic setting. Interestingly, we found that after the torrential rain, the abundance of Archaea increased in the deep groundwater at site GW-550m, ~ 12 km downstream of SP-0m. However, chemical parameters did not show any change after the event. This suggests that strengthened piston flow caused by the heavy rain transported archaeal particles from the geologic layer along the groundwater route. This finding was supported by changes in constituents of Archaea, dominated by Halobacteriales and Methanobacteriales, which were not seen from other observations. Those two groups of Archaea are believed to be relatively tightly embedded in the geologic layer and were extracted from the environment to the examined groundwater through enforced piston flow. Microbial DNA can thus give information about the groundwater route, which may not be shown by analysis of chemical materials dissolved in the groundwater.