Single-particle approach for analyzing flow systems. Part II: Regional residence times and local flow rates

AIChE Journal ◽  
1983 ◽  
Vol 29 (4) ◽  
pp. 663-668 ◽  
Author(s):  
Michael Rubinovitch ◽  
Uzi Mann
Keyword(s):  
Single Particle ◽  
Residence Times ◽  
Local Flow ◽  
Flow Rates ◽  
Flow Systems ◽  
Particle Approach

A single particle approach for analyzing flow systems. Part III: Multiple fluids

AIChE Journal ◽  
1985 ◽  
Vol 31 (4) ◽  
pp. 615-620 ◽  
Author(s):  
Michael Rubinovitch ◽  
Uzi Mann
Keyword(s):  
Single Particle ◽  
Flow Systems ◽  
Particle Approach

Single-particle approach for analyzing flow systems. Part I: Visits to flow regions

AIChE Journal ◽  
1983 ◽  
Vol 29 (4) ◽  
pp. 658-662 ◽  
Author(s):  
Michael Rubinovitch ◽  
Uzi Mann
Keyword(s):  
Single Particle ◽  
Flow Systems ◽  
Particle Approach

On the time scales and structure of Lagrangian intermittency in homogeneous isotropic turbulence

2019 ◽  
Vol 867 ◽  
pp. 438-481 ◽  
Author(s):  
R. Watteaux ◽  
G. Sardina ◽  
L. Brandt ◽  
D. Iudicone
Keyword(s):  
Time Scales ◽  
Isotropic Turbulence ◽  
Flow Characteristics ◽  
Residence Times ◽  
Particle Trajectories ◽  
Local Flow ◽  
Available Energy ◽  
Homogeneous And Isotropic Turbulence ◽  
History Of ◽  
Optimum Manner

We present a study of Lagrangian intermittency and its characteristic time scales. Using the concepts of flying and diving residence times above and below a given threshold in the magnitude of turbulence quantities, we infer the time spectra of the Lagrangian temporal fluctuations of dissipation, acceleration and enstrophy by means of a direct numerical simulation in homogeneous and isotropic turbulence. We then relate these time scales, first, to the presence of extreme events in turbulence and, second, to the local flow characteristics. Analyses confirm the existence in turbulent quantities of holes mirroring bursts, both of which are at the core of what constitutes Lagrangian intermittency. It is shown that holes are associated with quiescent laminar regions of the flow. Moreover, Lagrangian holes occur over few Kolmogorov time scales while Lagrangian bursts happen over longer periods scaling with the global decorrelation time scale, hence showing that loss of the history of the turbulence quantities along particle trajectories in turbulence is not continuous. Such a characteristic partially explains why current Lagrangian stochastic models fail at reproducing our results. More generally, the Lagrangian dataset of residence times shown here represents another manner for qualifying the accuracy of models. We also deliver a theoretical approximation of mean residence times, which highlights the importance of the correlation between turbulence quantities and their time derivatives in setting temporal statistics. Finally, whether in a hole or a burst, the straining structure along particle trajectories always evolves self-similarly (in a statistical sense) from shearless two-dimensional to shear bi-axial configurations. We speculate that this latter configuration represents the optimum manner to dissipate locally the available energy.

Effects of Inlet Mass Flow Distribution and Magnitude on Reactant Distribution for PEM Fuel Cells

2005 ◽  
Vol 3 (1) ◽  
pp. 45-50 ◽  
Author(s):  
M. McGarry ◽  
L. Grega
Keyword(s):  
Fuel Cell ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Separation ◽  
Flow Distribution ◽  
Pem Fuel Cells ◽  
Local Flow ◽  
Flow Rates ◽  
Large Active Area ◽  
Mass Flow Rates

The mass flow distribution and local flow structures that lead to areas of reactant starvation are explored for a small power large active area PEM fuel cell. A numerical model was created to examine the flow distribution for three different inlet profiles; blunt, partially developed, and fully developed. The different inlet profiles represent the various distances between the blower and the inlet to the fuel cell and the state of flow development. The partially and fully developed inlet profiles were found to have the largest percentage of cells that are deficient, 20% at a flow rate of 6.05 g/s. Three different inlet mass flow rates (stoichs) were also examined for each inlet profile. The largest percent of cells deficient in reactants is 27% and occurs at the highest flow rate of 9.1 g/s (3 stoichs) for the partially and fully developed turbulent profiles. In addition to the uneven flow distribution, flow separation occurs in the front four channels for the blunt inlet profile at all flow rates examined. These areas of flow separation lead to localized reactant deficient areas within a channel.

scholarly journals Nested Recharge Systems in Mountain Block Hydrology: High-Elevation Snowpack Generates Low-Elevation Overwinter Baseflow in a Rocky Mountain River

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2249
Author(s):  
Éowyn M. S. Campbell ◽  
M. Cathryn Ryan
Keyword(s):  
Rocky Mountain ◽  
High Elevation ◽  
Third Order ◽  
Relative Temperature ◽  
Local Flow ◽  
Fracture Systems ◽  
Lower Elevation ◽  
Flow Systems ◽  
Longitudinal Sampling

The majority of each year′s overwinter baseflow (i.e., winter streamflow) in a third-order eastern slopes tributary is generated from annual melting of high-elevation snowpack which is transmitted through carbonate and siliciclastic aquifers. The Little Elbow River and its tributaries drain a bedrock system formed by repeated thrust faults that express as the same siliciclastic and carbonate aquifers in repeating outcrops. Longitudinal sampling over an 18 km reach was conducted at the beginning of the overwinter baseflow season to assess streamflow provenance. Baseflow contributions from each of the two primary aquifer types were apportioned using sulfate, δ34SSO4, and silica concentrations, while δ18OH2O composition was used to evaluate relative temperature and/or elevation of the original precipitation. Baseflow in the upper reaches of the Little Elbow was generated from lower-elevation and/or warmer precipitation primarily stored in siliciclastic units. Counterintuitively, baseflow generated in the lower-elevation reaches originated from higher-elevation and/or colder precipitation stored in carbonate units. These findings illustrate the role of nested flow systems in mountain block recharge: higher-elevation snowmelt infiltrates through fracture systems in the cliff-forming—often higher-elevation—carbonates, moving to the lower-elevation valley through intermediate flow systems, while winter baseflow in local flow systems in the siliciclastic valleys reflects more influence from warmer precipitation. The relatively fast climatic warming of higher elevations may alter snowmelt timing, leaving winter water supply vulnerable to climatic change.

scholarly journals The Exact Groundwater Divide on Water Table between Two Rivers: A Fundamental Model Investigation

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 685 ◽  
Author(s):  
Peng-Fei Han ◽  
Xu-Sheng Wang ◽  
Li Wan ◽  
Xiao-Wei Jiang ◽  
Fu-Sheng Hu
Keyword(s):  
Water Level ◽  
Water Table ◽  
Catchment Area ◽  
River Basins ◽  
Two Dimensional ◽  
Local Flow ◽  
Fundamental Model ◽  
Through Flow ◽  
Flow Systems ◽  
Pass Through

The groundwater divide within a plane has long been delineated as a water table ridge composed of the local top points of a water table. This definition has not been examined well for river basins. We developed a fundamental model of a two-dimensional unsaturated–saturated flow in a profile between two rivers. The exact groundwater divide can be identified from the boundary between two local flow systems and compared with the top of a water table. It is closer to the river of a higher water level than the top of a water table. The catchment area would be overestimated (up to ~50%) for a high river and underestimated (up to ~15%) for a low river by using the top of the water table. Furthermore, a pass-through flow from one river to another would be developed below two local flow systems when the groundwater divide is significantly close to a high river.

scholarly journals The Influence of Aneurysm Configuration on Intra-Aneurysmal Pressure and Flow

2006 ◽  
Vol 12 (3) ◽  
pp. 203-214 ◽  
Author(s):  
A. Sorteberg ◽  
D. Farhoudi
Keyword(s):  
Side Wall ◽  
Aneurysm Rupture ◽  
Parent Artery ◽  
Pressure Waves ◽  
Local Flow ◽  
Flow Rates ◽  
Flow Phantom ◽  
Respective Parent ◽  
Pressure Transmission ◽  
Intravascular Pressure

Aneurysm rupture may occur in conjunction with swift pressure increases like heavy lifting. We therefore investigated the transmission of pressure waves as well as local flow rates in various types of experimental aneurysms and their parent arteries. 0.014-inch guidewires containing a combined pressure and thermistor sensor were inserted into both the dome and the parent artery of idealized silicone aneurysms mounted in a pulsatile flow phantom. Intravascular pressure and thermodilution responses to injections of room-temperatured normal saline at a rate of 5cc.s−1 over two seconds were recorded simultaneously at both sites. Flow was evaluated semiquantitatively applying the thermodilution principle. We found that the propagation of pressure was attenuated at the dome of the aneurysms compared to their respective parent arteries. This difference was more distinct in side-wall aneurysms than in bifurcational aneurysms. The attenuation of traveling pressure in the aneurysm was most effective at low systemic pressures. The intraaneurysmal flow rate was unique, always lower than in the respective parent arteries and highly dependent on the configuration of the aneurysm. We observed considerably higher flow rates in bifurcational aneurysms compared to side-wall aneurysms. Bifurcational aneurysms were hence characterized by a relatively high pressure transmission and high flow rates which may represent a stimulus for enlargement of untreated aneurysms and promote coil compaction in endovascularly treated lesions.

scholarly journals Ground-Water Circulation in the Meade Thrust Allochthon Evaluated by Radiocarbon Techniques

Radiocarbon ◽  
1983 ◽  
Vol 25 (2) ◽  
pp. 357-372 ◽  
Author(s):  
A B Muller ◽  
A L Mayo
Keyword(s):  
Ground Water ◽  
Major Ions ◽  
Analysis Data ◽  
Mining Area ◽  
Water Circulation ◽  
Hydrocarbon Exploration ◽  
Residence Times ◽  
Flow Systems ◽  
Phosphoria Formation ◽  
Overthrust Belt

The Meade thrust, in southeastern Idaho, is a major element of the Western Overthrust Belt. The allochthon is of geo-economic importance both as a potential hydrothermal area and as the principal mining area within the Western Phosphate Field. To assist in the development of these two resources, an understanding of the regional ground-water circulation was sought. Geologic and hydrologic data from boreholes in this area are virtually nonexistent. Waterwell development in the area has not occurred because of the abundance of springs and only a few hydrocarbon exploration boreholes have been drilled. Thus, the problem lends itself to evaluation by isotope hydrologic and geochemical methods. Ten springs from within the thrust block and around its periphery were sampled for major ions, 2H/18O, and 14C/13C analysis. Data from these analyses and from field geologic evidence have identified two distinct flow regimes within the Meade thrust allochthon. Shallow flow systems lie above the impermeable Phosphoria Formation, usually within a few hundred meters of the surface. Most of the spring waters from this system are recent and cool. In all cases, they have mean subsurface residence times of less than a few hundred years. The deeper flow systems which lie below the Phosphoria formation are hydraulically isolated from the shallow system. Warm waters from these springs have 14C contents suggesting mean ground-water residence times on the order of 15,000 years. Although these waters could have circulated to as deep as 1900m, 2H/18O results show that high temperatures were never reached. There is no evidence to suggest that water from beneath the Meade thrust has contributed to the circulation in the allochthon.

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