scholarly journals Interstellar Neutral He Parameters from Crossing Parameter Tubes with the Interstellar Mapping and Acceleration Probe Informed by 10 yr of Interstellar Boundary Explorer Observations

2021 ◽  
Vol 258 (1) ◽  
pp. 7
Author(s):  
N. A. Schwadron ◽  
E. Möbius ◽  
D. J. McComas ◽  
J. Bower ◽  
E. Bower ◽  
...  
Keyword(s):  
Statistical Parameter ◽  
Flow Distribution ◽  
Longitudinal Direction ◽  
The Sun ◽  
Parameter Uncertainties ◽  
Local Flow ◽  
Pickup Ions ◽  
Systematic Uncertainties ◽  
Interstellar Plasma ◽  
It Operations

Abstract The Sun's motion through the interstellar medium leads to an interstellar neutral (ISN) wind through the heliosphere. Several ISN species, including He, moderately depleted by ionization are observed with pickup ions and directly imaged. Since 2009, analyzed Interstellar Boundary Explorer (IBEX) observations returned a precise 4D parameter tube associated with the bulk velocity vector and the temperature of ISN flow distribution. This 4D parameter tube is typically expressed in terms of the ISN speed, the inflow latitudinal direction, and the temperature as a function of the inflow longitudinal direction and the local flow Mach number. We have used IBEX observations and those from other spacecraft to reduce statistical parameter uncertainties: V ISN ∞ = 25.99 ± 0.18 km s−1, λ ISN ∞ = 75 .° 28 ± 0 .° 13 , β ISN ∞ = −5 .° 200 ± 0 .° 075 , and T ISN ∞ = 7496 ± 172 K. IBEX ISN viewing is restricted almost perpendicular to the Earth–Sun line, which limits observations in ecliptic longitude to ∼130° ± 30° and results in relatively small uncertainties across the IBEX parameter tube but large uncertainties along it. Operations over the last three years enabled the IBEX spin axis to drift to the maximum operational offset (7°) west of the Sun, helping to break the ISN parameter degeneracy by weakly crossing the IBEX parameter tubes: the range of possible inflow longitudes extends over the range λ ISN ∞ = 75 .° 28 − 2.21 + 2.27 and the corresponding range of other ISN parameters is V ISN ∞ = 25.99 − 1.76 + 1.86 km s−1, β ISN ∞ = −5 .° 200 − 0.085 + 0.093 , and T ISN ∞ = 7496 − 1528 + 1274 K. This enhances the full χ 2 analysis of ISN parameters through comparison with detailed models. The next-generation IBEX-Lo sensor on IMAP will be mounted on a pivot platform, enabling IMAP-Lo to follow the ISN flow over almost the entire spacecraft orbit around the Sun. A near-continuous set of 4D parameter tube orientations on IMAP will be observed for He and for O, Ne, and H that cross at varying angles to substantially reduce the ISN flow parameter uncertainties and mitigate systematic uncertainties (e.g., from ionization effects and the presence of secondary components) to derive the precise parameters of the primary and secondary local interstellar plasma flows.

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.

Blockage and Distortion Effects on a Vane Island Type Diffuser Performance of Centrifugal Pumps for Various Flow Rates

2015 ◽  
Author(s):  
Qiaorui Si ◽  
Antoine Dazin ◽  
Patrick Dupont ◽  
Olivier Roussette ◽  
Gérard Bois
Keyword(s):  
Outer Part ◽  
Flow Distribution ◽  
Flow Structures ◽  
Inlet Section ◽  
Centrifugal Pumps ◽  
Mean Flow ◽  
Local Flow ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Island Type

Experimental investigation of mean flow velocity and pressure inside the vane-island type diffuser passage of a laboratory centrifugal pump model is presented in this paper. A three-hole directional probe was used to investigate hub to shroud flow properties at diffuser leading and trailing edge planes and at the mid-section between suction and pressure sides along the diffuser passage. All these measurements have been performed for five different flow conditions. The flow structures at the inlet section of the diffuser and along with the passage were analyzed in detail, with a focus on the flow distribution and the pressure recovery evolution of different diffuser part. Block age and distortion effects are analyzed using existing published Particle Image Velocimetry (PIV)measurements in the outer part of the impeller and around the diffuser throat in order to get a better understanding of the overall performances and local flow structures of such a diffuser design.

Skimming of microspheres in vitro: implications for measurement of intrarenal blood flow

1981 ◽  
Vol 241 (3) ◽  
pp. H342-H347 ◽  
Author(s):  
E. S. Ofjord ◽  
G. Clausen ◽  
K. Aukland
Keyword(s):  
Blood Flow ◽  
Flow Distribution ◽  
Blood Flow Distribution ◽  
Particle Inertia ◽  
Local Flow ◽  
Size Dependent ◽  
Dog Kidney ◽  
Intrarenal Blood Flow ◽  
Renal Cortical Blood Flow

Skimming could result in erroneous estimation of renal cortical blood flow distribution as measured by microspheres. Skimming of microspheres with diameters 10, 12, and 15 micrometers and red blood cells was therefore studied in a model in which an interlobular artery and its first arteriolar branch were simulated by 80- and 30-micrometers-wide slits between glass prisms. The experiments were performed with citrated blood at a hematocrit (Hct) of 40, flow velocities of 3 and 6 cm/s, and branch flow varying from 2 to 25%. At a branch flow fraction comparable to that of a deep arteriole in the dog kidney (3%), Hct in branch blood was 24% lower than that of input blood, whereas 10-, 12-, and 15-micrometers microsphere concentrations were 75, 81, and 87% lower, respectively. The size-dependent skimming was probably caused by wall exclusion in the main channel. Differences in particle inertia did not affect skimming. The results suggest that the disparate local flow values obtained by use of microspheres of different sizes in dog and rat kidneys are due to a size-dependent skimming of the microspheres.

Numerical Study of the Winter-Kennedy Method—A Sensitivity Analysis

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Binaya Baidar ◽  
Jonathan Nicolle ◽  
Chirag Trivedi ◽  
Michel J. Cervantes
Keyword(s):  
Boundary Conditions ◽  
Secondary Flow ◽  
Numerical Study ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Local Flow ◽  
Spiral Case ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Changes

The Winter-Kennedy (WK) method is commonly used in relative discharge measurement and to quantify efficiency step-up in hydropower refurbishment projects. The method utilizes the differential pressure between two taps located at a radial section of a spiral case, which is related to the discharge with the help of a coefficient and an exponent. Nearly a century old and widely used, the method has shown some discrepancies when the same coefficient is used after a plant upgrade. The reasons are often attributed to local flow changes. To study the change in flow behavior and its impact on the coefficient, a numerical model of a semi-spiral case (SC) has been developed and the numerical results are compared with experimental results. The simulations of the SC have been performed with different inlet boundary conditions. Comparison between an analytical formulation with the computational fluid dynamics (CFD) results shows that the flow inside an SC is highly three-dimensional (3D). The magnitude of the secondary flow is a function of the inlet boundary conditions. The secondary flow affects the vortex flow distribution and hence the coefficients. For the SC considered in this study, the most stable WK configurations are located toward the bottom from θ=30deg to 45deg after the curve of the SC begins, and on the top between two stay vanes.

Temporal measurements of the interstellar helium focusing cone by the Magnetospheric Multiscale Mission(MMS)

2020 ◽  
Author(s):  
Roman Gomez ◽  
Stephen Fuselier ◽  
James Burch ◽  
Joey Mukherjee ◽  
Carrie Gonzalez ◽  
...  
Keyword(s):  
Radiation Environment ◽  
Neutral Density ◽  
The Sun ◽  
Plasma Composition ◽  
Local Interstellar Medium ◽  
Pickup Ions ◽  
Neutral Particles ◽  
Hot Plasma ◽  
Magnetospheric Multiscale ◽  
Magnetospheric Multiscale Mission

<p>The Sun and its associated heliosphere travels through the local interstellar medium (LISM) at 26 km/s.  This results in a flow of neutral particles constantly entering the heliosphere at the same velocity.  Neutral atoms with trajectories close to the Sun, which survive its ionizing radiation environment, become gravitationally attracted to it resulting in a focusing cone, a region of enhanced neutral density, downwind of the Sun.  The increased neutral density in these regions leads to a higher density of pickup ions created by charge-exchange of the neutrals.  In near-Earth orbit, the Magnetospheric Multiscale spacecraft (4 in all) have orbital apogees on the dayside during Earth’s annual encounter with the helium focusing cone (from mid-November to mid-December).  Since launching in March of 2015, regular acquisitions with the Hot Plasma Composition Analyzers (HPCAs) have been conducted, with acquisitions from 2017 through 2019 occurring with a 29 RE apogee, ensuring long intervals in the pristine Solar Wind.   We provide measurements of the focusing cone during the declining phase of the previous solar cycle. These measurements are used to investigate the effect of solar radiation on the focusing cone.</p>

scholarly journals Effect of Air Extraction for Cooling and/or Gasification on Combustor Flow Uniformity

1998 ◽  
Author(s):  
T. Wang ◽  
J. S. Kapat ◽  
W. R. Ryan ◽  
I. S. Diakunchak ◽  
R. L. Bannister
Keyword(s):  
Flow Field ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Coal Gasification ◽  
Field Experiments ◽  
Fuel Injection ◽  
Flow Distribution ◽  
Flow Uniformity ◽  
Complex Flow ◽  
Local Flow

Reducing emissions is an important issue facing gas turbine manufacturers. Almost all of the previous and current research and development for reducing emissions has focused, however, on flow, heat transfer, and combustion behavior in the combustors or on the uniformity of fuel injection without placing strong emphasis on the flow uniformity entering the combustors. In response to the incomplete understanding of the combustor’s inlet air flow field, experiments were conducted in a 48% scale, 360° model of the diffuser-combustor section of an industrial gas turbine. In addition, the effect of air extraction for cooling or gasification on the flow distributions at the combustors’ inlets was also investigated. Three different air extraction rates were studied: 0% (baseline), 5% (airfoil cooling), and 20% (for coal gasification). The flow uniformity was investigated for two aspects: (a) global uniformity, which compared the mass flow rates of combustors at different locations relative to the extraction port, and (b) local uniformity, which examined the circumferential flow distribution into each combustor. The results indicate that even for the baseline case with no air extraction there was an inherent local flow aonuniformity of 10 ∼ 20% at the inlet of each combustor due to the complex flow field in the dump diffuser and the blockage effect of the cross-flame tube. More flow was seen in the portion further away from the gas turbine center axis. The effect of 5% air extraction was small. Twenty-percent air extraction introduced approximately 35% global flow asymmetry diametrically across the dump diffuser. The effect of air extraction on the combustor’s local flow uniformity varied with the distances between the extraction port and each individual combustor. Longer top hats were installed with the initial intention of increasing flow mixing prior to entering the combustor. However, the results indicated that longer top hats do not improve the flow uniformity; sometimes, adverse effects can be seen. Although a specific geometry was selected for this study, the results provide sufficient generality to benefit other industrial gas turbines.

A Study of Inlet Flow Distortion Effects on Automotive Catalytic Converters

1991 ◽  
Vol 113 (3) ◽  
pp. 419-426 ◽  
Author(s):  
G. Bella ◽  
V. Rocco ◽  
M. Maggiore
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Flow Distribution ◽  
Catalytic Converters ◽  
Flow Distortion ◽  
Local Flow ◽  
Positive Effects ◽  
Local Boundary Condition

This paper will focus on the influence exerted by a nonuniform flow distribution at the inlet of oxidizers to catalytic converters on conversion efficiency evaluated channel by channel. To this aim the flow inside the whole domain, constituted by the exhaust manifold and an elliptic-cross-sectional pipe connecting it with the converter shell, is simulated by means of a three-dimensional fluid-dynamic viscous model. In this way, after assigning typical converter size and geometry (i.e., elliptic) the gas flow rate distribution can be described at its inlet surface, also varying the total mass flow rate. After calculating the flow field at converter inlet by means of a three-dimensional model, evaluation is possible of local flow distortion in comparison with the ideal conditions of constant velocity of the gas entering the honeycomb converter channels. The abovementioned distorted flow field is then assigned as a local boundary condition for another model, developed by the authors, able to describe, through a one-dimensional fluid-dynamic approach, the reacting flow into the converter channels. It was also shown that, due to this flow distortion, honeycomb converters are not uniformly exploited in terms of pollutants of different quantities to be converted in each channel (i.e., a nonuniform exploitation of all the metals coating the ceramic monolith). Finally, the positive effects determined by a diffuser upstream of the converter on flow distribution are analyzed.

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