scholarly journals Hydrology of a segment of a glacier situated in an overdeepening, Storglaciären, Sweden

1994 ◽  
Vol 40 (134) ◽  
pp. 140-148 ◽  
Author(s):  
Roger Leb. Hooke ◽  
Veijo A. Pohjola
Keyword(s):  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Video Observations ◽  
Pressure Melting ◽  
Bed Slope ◽  
Energy Dissipated ◽  
Total Discharge ◽  
Tracer Experiments

AbstractTracer experiments, and water-level observations made while drilling 47 boreholes in an overdeepened section of Storglaciären, have demonstrated that nearly all of the water passing through this part of the glacier moves in englacial conduits. Much of the viscous energy dissipated by subglacial water flowing up an adverse bed slope out of such an overdeepening may be needed to warm the water to keep it at the pressure-melting point. If the adverse slope is sufficiently steep, freezing may occur within the conduits. The possibility for enlargement of conduits by melting is thus limited and water pressures become high. We infer that this, combined with possible blocking of conduits by freezing, forces the water to seek englacial pathways.The frequency with which englacial conduits are encountered during drilling suggests that there are several hundred of them in any given cross-section of the glacier. Consequently, each must carry a small fraction of the total discharge, say ∼ 10−3 m3 s−1. Tracer experiments suggest that flow rates in these conduits are < 10− m s−1, so conduit cross-sectional areas must be ∼10−2 m2, a size that is consistent with video observations in boreholes. The observed mean hydraulic gradient through the overdeepening is ∼0.04. If the conduits were of uniform cross-sectional area, the roughness implied by these figures would be unreasonably high and water pressures in them would be lower than observed. Thus, we hypothesize that conduits are locally constricted to only a small fraction of their average cross-sectional area.

scholarly journals Hydrology of a segment of a glacier situated in an overdeepening, Storglaciären, Sweden

1994 ◽  
Vol 40 (134) ◽  
pp. 140-148 ◽  
Author(s):  
Roger Leb. Hooke ◽  
Veijo A. Pohjola
Keyword(s):  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Video Observations ◽  
Pressure Melting ◽  
Bed Slope ◽  
Energy Dissipated ◽  
Total Discharge ◽  
Tracer Experiments

AbstractTracer experiments, and water-level observations made while drilling 47 boreholes in an overdeepened section of Storglaciären, have demonstrated that nearly all of the water passing through this part of the glacier moves in englacial conduits. Much of the viscous energy dissipated by subglacial water flowing up an adverse bed slope out of such an overdeepening may be needed to warm the water to keep it at the pressure-melting point. If the adverse slope is sufficiently steep, freezing may occur within the conduits. The possibility for enlargement of conduits by melting is thus limited and water pressures become high. We infer that this, combined with possible blocking of conduits by freezing, forces the water to seek englacial pathways.The frequency with which englacial conduits are encountered during drilling suggests that there are several hundred of them in any given cross-section of the glacier. Consequently, each must carry a small fraction of the total discharge, say ∼ 10−3m3s−1. Tracer experiments suggest that flow rates in these conduits are &lt; 10−m s−1, so conduit cross-sectional areas must be ∼10−2m2, a size that is consistent with video observations in boreholes. The observed mean hydraulic gradient through the overdeepening is ∼0.04. If the conduits were of uniform cross-sectional area, the roughness implied by these figures would be unreasonably high and water pressures in them would be lower than observed. Thus, we hypothesize that conduits are locally constricted to only a small fraction of their average cross-sectional area.

Enhanced Flow Boiling Heat Transfer Using Radial Microchannels

2016 ◽  
Author(s):  
Alyssa Recinella ◽  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Flow Boiling ◽  
Cross Sectional Area ◽  
Working Fluid ◽  
Transfer Performance ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Flow Cross

Flow boiling has the ability to remove high heat fluxes while maintaining a low wall superheat. Various researchers have developed enhanced microchannel geometries to improve the heat transfer performance of the system. Recently, a number of new studies have used the increasing flow cross-sectional area concept to overcome flow instabilities and record high CHF. In this work, a new geometry is experimentally investigated utilizing a radial cross-section, which provides the increasing fluid flow cross-sectional area in the flow direction. The flow boiling performance is studied using radial microchannels and water as the working fluid. Four different flow rates ranging from 120–400 mL/min are studied for this new geometry. Heat transfer performance (boiling curve and heat transfer coefficient) and pressure drop characteristics are discussed for all flow rates. Furthermore, the work is supported by high speed visualization of the bubble dynamics. The boiling performance obtained is compared to the existing data in the literature.

Manufacturing Influences on Pressure Losses of Channel Fed Holes

2013 ◽  
Author(s):  
Michael Barringer ◽  
Karen A. Thole ◽  
Vaidyanathan Krishnan ◽  
Evan Landrum
Keyword(s):  
Reynolds Number ◽  
Pressure Loss ◽  
Cross Sectional Area ◽  
Channel Inlet ◽  
Sectional Area ◽  
Exit Hole ◽  
Cross Sectional ◽  
Flow Rates ◽  
Channel Exit ◽  
Loss Coefficients

Variations from manufacturing can influence the overall pressure drop and subsequent flow rates through supply holes in such applications as film-cooling, transpiration cooling, and impingement cooling that are supplied by micro-channels, pipe-flow systems, or secondary air systems. The inability to accurately predict flow rates has profound effects on engine operations. The objective of this study was to investigate the influence of several relevant manufacturing features that might occur for a cooling supply hole being fed by a range of channel configurations. The manufacturing variances included the ratio of hole diameter to channel width, the number of channel feeds (segments), the effect of hole overlap with respect to the channel sidewalls, and channel Reynolds number. Results showed that the friction factors for the typically long channels in this study, were independent of the inlet and exit hole configurations tested. Results also showed that the non-dimensional pressure loss coefficients for the flow passing through the channel inlet holes and through the channel exit holes were found to be independent of the channel flow Reynolds number over the range tested. The geometric scaling ratio of the hole cross-sectional area to the channel cross-sectional area collapsed the pressure loss coefficients the best for both one and two flow segments for both the channel inlet and channel exit hole.

Maximal Expiratory Flow and Lung Volume Changes Associated with Exercise-Induced Asthma in Children and the Effect of Breathing a Low-Density Gas Mixture

1974 ◽  
Vol 46 (3) ◽  
pp. 317-329 ◽  
Author(s):  
S. R. Benatar ◽  
P. König
Keyword(s):  
Flow Rate ◽  
Vital Capacity ◽  
Forced Expiratory Volume ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Lung Volumes ◽  
Flow Rates ◽  
Before And After ◽  
Expiratory Flow

1. Lung volumes and maximum expiratory flow volume (MEFV) curves were measured before and after exercise and after a bronchodilator in eight asthmatic children. 2. Exercise produced significant changes in all volumes and flow rates measured, but the most sensitive measurement was of flow rate at an absolute volume in the terminal portion of the forced vital capacity. Of the more simply obtained measurements maximal flow at 50% of the exhaled vital capacity was the most sensitive, but reductions in forced expiratory volume at 1 s and peak flow rate were almost as marked. 3. The marked reductions in flow rates at low lung volumes after exercise were accompanied by large increases in residual volume and a reduction in the slope of the MEFV curve. These changes suggest functional closure of some lung units and an increase in the time-constant of emptying of other units. 4. The response of flow to breathing helium—oxygen (79:21, v/v) was assessed in the dilated state (before exercise or after bronchodilator) and the constricted state (after exercise) in five of the subjects. 5. An increase in density-dependence of flow rates at all lung volumes during constriction is evidence that, despite the reduction in flow rates, convective acceleration and turbulent flow constitute a greater proportion of the total upstream resistance after exercise than before exercise. The implication is that the cross-sectional area at equal pressure points (EPP) is smaller after exercise than before exercise. This could result from either bronchoconstriction with no change in the location of EPP, or from progression of the EPP further upstream to a region where loss of airways or reduction in their diameter has rendered the total cross-sectional area considerably smaller than under normal circumstances.

Manufacturing Influences on Pressure Losses of Channel Fed Holes

2013 ◽  
Vol 136 (5) ◽  
Author(s):  
Michael Barringer ◽  
Karen A. Thole ◽  
Vaidyanathan Krishnan ◽  
Evan Landrum
Keyword(s):  
Reynolds Number ◽  
Pressure Loss ◽  
Cross Sectional Area ◽  
Channel Inlet ◽  
Sectional Area ◽  
Exit Hole ◽  
Cross Sectional ◽  
Flow Rates ◽  
Channel Exit ◽  
Loss Coefficients

Variations from manufacturing can influence the overall pressure drop and subsequent flow rates through supply holes in such applications as film-cooling, transpiration cooling, and impingement cooling that are supplied by microchannels, pipe-flow systems, or secondary air systems. The inability to accurately predict flow rates has profound effects on engine operations. The objective of this study was to investigate the influence of several relevant manufacturing features that might occur for a cooling supply hole being fed by a range of channel configurations. The manufacturing variances included the ratio of the hole diameter to the channel width, the number of channel feeds (segments), the effect of hole overlap with respect to the channel sidewalls, and the channel Reynolds number. The results showed that the friction factors for the typically long channels in this study were independent of the tested inlet and exit hole configurations. The results also showed that the nondimensional pressure loss coefficients for the flow passing through the channel inlet holes and through the channel exit holes were found to be independent of the channel flow Reynolds number over the tested range. The geometric scaling ratio of the hole cross-sectional area to the channel cross-sectional area collapsed the pressure loss coefficients the best for both one and two flow segments for both the channel inlet and channel exit hole.

Physiology of Cough

1974 ◽  
Vol 83 (6) ◽  
pp. 761-768 ◽  
Author(s):  
P. T. MacKlem
Keyword(s):  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Lung Volumes ◽  
Flow Rates ◽  
Velocity Flow ◽  
Large Airways ◽  
Total Cross Sectional Area ◽  
Expiratory Flow ◽  
Expiratory Flow Rates

The effectiveness of cough depends upon the linear velocity of the gas in the airways. Because velocity = flow/cross-sectional area, a high flow and a small cross-section are the ideal conditions for an effective cough. Pleural pressures become positive during cough and compress the large airways producing a marked reduction in cross-sectional area. At high lung volumes, expiratory flow rates are high so that the linear velocities in the trachea are approximately one-third of the speed of sound. The velocity falls in higher bronchial generations, both because the total cross-sectional area of each generation becomes progressively larger beyond the lobar bronchi, and because at high volumes the compressed segment of the airway only extends from the lobar bronchi to the thoracic outlet of the trachea. In normal lungs cough is effective in clearing secretions from these airways only. In chronic bronchitis and emphysema, expiratory flow rates are markedly reduced. Furthermore, in some cases the large airways are more easily compressed than normal. This results in a shorter segment of the airway being compressed. For both reasons, the efficiency of cough is markedly decreased leading to retention of secretions. In cystic and varicose bronchiectasis the problem is different. There is no flow through the bronchiectatic segments because they are blind sacs, and the efficiency of cough is independent of the velocity. To empty them of their secretions is analogous to squeezing toohpaste out of a tube. This is theoretically possible at low lung volumes when the compressed segment is longer.

scholarly journals The Determination of the Inward Leakage through the Skin–Facepiece Interface of the Protective Half-Mask

2021 ◽  
Vol 11 (17) ◽  
pp. 8042
Author(s):  
Tomáš Brestovič ◽  
Marián Lázár ◽  
Natália Jasminská ◽  
Jozef Živčák ◽  
Radovan Hudák ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Air Leakage ◽  
Cross Sectional ◽  
Flow Rates ◽  
Pressure Drops ◽  
The Face ◽  
The Cross

The present article describes the measurements of flow rates of the inward air leakage through the skin–facepiece interface of a protective half-mask with replaceable filters. The measurements were carried out while applying an indirect method in which the pressure drops in a compressed air container were measured, and subsequently, the total flow rate of the leak was calculated. This methodology facilitated measuring extremely low air flow rates at the atmospheric pressure of 3.2 × 10−6 m3·s−1. A numerical analysis of the inward air leakage through the gaps between the face and the facepiece of the mask was carried out with the aim of identifying the cross-sectional area of the leak. With the tested mask, which was made of Santoprene 8281-45MED, the leakage measured during inhalation was 0.21%, which corresponded to the cross-sectional area of only 0.14 mm2.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

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