Oxygen Consumption and Gill Water Flow in the Dogfish Scyliorhinus Canicula L

1968 ◽  
Vol 49 (3) ◽  
pp. 557-564 ◽  
Author(s):  
G. M. HUGHES ◽  
SHUN-ICHI UMEZAWA
Keyword(s):  
Oxygen Consumption ◽  
Hydrostatic Pressure ◽  
Pressure Gradient ◽  
Linear Relationship ◽  
Water Flow ◽  
Marked Change ◽  
Respiratory Frequency ◽  
Flow Rates ◽  
Scyliorhinus Canicula ◽  
The Relationship

1. Determinations of the standard oxygen consumption of the dogfish Scyliorhinus canicula, by several different methods, gave values in the range of 20-55 c.c./kg./hr. at 12°C. 2. When the rate of water flow over the resting fish is increased, there is an increase in oxygen consumption, but no marked change in respiratory frequency at the flow rates studied. An increase of respiratory frequency took place when the PO2 of the inspired water was reduced. 3. The ventilation volume of the dogfish was measured by collecting the water in chambers after it had passed over the gills. The resting ventilation volume was about 120 c.c./min./kg. at 12° C. 4. The relationship between the flow across the gills and the imposed hydrostatic pressure gradient (Δp) showed a linear relationship. The fish was unable to continue pumping water across the gills against adverse gradients in excess of 0.7 cm. H2O. 5. When the flow across the gills was relatively low, utilization of oxygen of at least 70% was observed, but with increasing flow rates this fell to between 40 and 50%.

The Effect of Surfactants on Vertical Air/Water Flow for Prevention of Liquid Loading

SPE Journal ◽  
2016 ◽  
Vol 21 (02) ◽  
pp. 488-500 ◽  
Author(s):  
A. T. van Nimwegen ◽  
L. M. Portela ◽  
R. A. Henkes
Keyword(s):  
Surface Tension ◽  
Pressure Gradient ◽  
Water Flow ◽  
Annular Flow ◽  
Surfactant Concentration ◽  
Gas Flow ◽  
Liquid Loading ◽  
Dynamic Surface ◽  
Flow Rates ◽  
Churn Flow

Summary From field experience in the gas industry, it is known that injecting surfactants at the bottom of a gas well can prevent liquid loading. To better understand how the selection of the surfactant influences the deliquification performance, laboratory experiments of air/water flow at atmospheric conditions were performed, in which two different surfactants (a pure surfactant, sodium dodecyl sulfate, and a commercial surfactant blend) were added to the water. In the experiments, a high-speed camera was used to visualize the flow, and pressure-gradient measurements were performed. Both surfactants increase the pressure gradient at high gas-flow rates and decrease the pressure gradient at low gas-flow rates. The minimum in the pressure gradient moves to lower gas-flow rates with increasing surfactant concentration. This is related to the transition between annular flow and churn flow, which is shifted to lower gas-flow rates because of the formation of an almost stagnant foam substrate at the wall of the pipe. At high surfactant concentration, it appears that the churn flow regime is no longer present at all and that there is a direct transition from annular flow to slug flow. The results also show that the critical micelle concentration, the equilibrium surface tension, the dynamic surface tension, and the surface elasticity are poor predictors of the effect of the surfactant on the flow.

scholarly journals Quinn’s Law of Fluid Dynamics Pressure-Driven Fluid Flow through Closed Conduits

2019 ◽  
Author(s):  
Hubert M Quinn
Keyword(s):  
Pressure Gradient ◽  
Linear Relationship ◽  
First Principles ◽  
Driving Force ◽  
Unique Minimum ◽  
Classical Studies ◽  
Flow Through ◽  
The Law ◽  
Solid Obstacles ◽  
The Relationship

In this paper we develop from first principles a unique law pertaining to the flow of fluids through closed conduits. This law, which we call “Quinn’s Law”, may be described as follows: When fluids are forced to flow through closed conduits under the driving force of a pressure gradient, there is a linear relationship between the normalized dimensionless pressure gradient, PQ, and the normalized dimensionless fluid current, CQ. The relationship is expressed mathematically as: PQ = k1 +k2CQ. This linear relationship remains the same whether the conduit is filled with or devoid of solid obstacles. The law differentiates, however, between a packed and an empty conduit by virtue of the tortuosity of the fluid path, which is seamlessly accommodated within the normalization framework of the law itself. When movement of the fluid is very close to being at rest, i.e., very slow, this relationship has the unique minimum constant value of k1, and as the fluid acceleration increases, it varies with a slope of k2 as a function of normalized fluid current. Quinn’s Law is validated herein by applying it to the data from published classical studies of measured permeability in both packed and empty conduits, as well as to the data generated by home grown experiments performed in the author’s own laboratory.

Water movement: does thermodynamic interpretation distort reality?

1989 ◽  
Vol 256 (3) ◽  
pp. C694-C698 ◽  
Author(s):  
A. Essig ◽  
S. R. Caplan
Keyword(s):  
Hydrostatic Pressure ◽  
Pressure Gradient ◽  
Partition Coefficient ◽  
Water Flow ◽  
Chemical Potential ◽  
Water Movement ◽  
Potential Gradient ◽  
Porous Membrane ◽  
Chemical Potential Gradient ◽  
Hydrostatic Pressure Gradient

In a recent theoretical analysis of water flow, Finkelstein (Water Movement Through Lipid Bilayers, Pores, and Plasma Membranes: Theory and Reality, 1987) has attacked the contributions of irreversible thermodynamics, stating that "the thermodynamic treatment of uphill water flow completely distorts reality." Instead he presents a mechanistic formulation. For a porous membrane, water flow is attributed to convection generated by a favorable hydrostatic pressure gradient within pores, even when in the presence of permeant solutes water moves against its chemical potential gradient; water flow may "drag", solute, to an extent determined by the solute partition coefficient, but the possibility that solute flow may drag water is excluded. We argue that this formulation violates the second law of thermodynamics. Water cannot move against its chemical potential gradient because of the influence of only part of the chemical potential gradient. Furthermore, the proposed mechanism requires that at one of the membrane-solution interfaces water must move against both its concentration gradient and the hydrostatic pressure gradient. Also considered by Finkelstein is the nature of the reflection coefficient sigma, a kinetic variable, which he concludes can be evaluated (in a porous membrane) by measurement of the (equilibrium) solute partition coefficient. We claim that in general it is not possible to evaluate a kinetic variable from measurements of equilibrium parameters alone. A valid kinetic analysis must incorporate the contribution of all coupled flows.

Lymphatic pump function curves in awake sheep

1996 ◽  
Vol 270 (2) ◽  
pp. R486-R488 ◽  
Author(s):  
R. E. Drake ◽  
S. Dhother ◽  
V. M. Oppenlander ◽  
J. C. Gabel
Keyword(s):  
Pressure Gradient ◽  
Mathematical Models ◽  
Flow Rate ◽  
Lymphatic Vessels ◽  
Ringer Solution ◽  
Nonlinear Flow ◽  
Flow Rates ◽  
Passive Flow ◽  
Lymphatic Pumping ◽  
The Relationship

We determined the relationship between flow rate and inflow pressure for intestinal lymphatic vessels in six sheep. First we anesthetized the sheep and cannulated both ends of a 6- to 10-cm-long segment of intestinal lymphatic. We allowed the sheep to recover from the anesthesia for 2-24 h. To determine the flow rate-inflow pressure relationship, we recorded the inflow pressure and infused Ringer solution into the lymphatic at rates from 34 to 510 microliters/min. The flow rate-pressure relationship was not linear and it had two regions. For flow rates less than approximately 150 microliters/min, inflow pressure was greater than outflow pressure. Thus the lymphatic pumped fluid against a pressure gradient. For flow rates > 150 microliters/min, inflow pressure was greater than outflow pressure, and we attributed most of the flow to the favorable inflow-outflow pressure gradient (passive flow). When we used verapamil to inhibit lymphatic pumping, we found no flow for inflow pressure less than outflow pressure, and flow increased linearly for inflow pressure greater than outflow pressure. Our data for actively pumping lymphatic vessels are consistent with the flow vs. pressure relationships derived from mathematical models of the lymphatic pump. Furthermore, our data with verapamil confirm that active lymphatic pumping was responsible for the nonlinear flow vs. pressure relationship for the lymphatic vessels.

Cardiac output and stroke volume in exercising ducks and pigeons

1982 ◽  
Vol 53 (1) ◽  
pp. 207-211 ◽  
Author(s):  
B. R. Grubb
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Stroke Volume ◽  
Linear Relationship ◽  
Body Mass ◽  
Content Difference ◽  
The Relationship

The purpose of this study was to determine the relationship between oxygen consumption (VO2) and cardiac output, stroke volume, and arteriovenous O2 content differences in resting and exercising birds. Pigeons and ducks showed a linear relationship between oxygen consumption and cardiac output and appeared to have a greater cardiac output for a given oxygen consumption than do mammals of the same body mass. In these birds the arteriovenous O2 content difference was hyperbolically related to oxygen consumption. The cardiac output was relatively high, implying a smaller arteriovenous O2 content difference than found in mammals. Resting stroke volume, relative to body mass, was greater in these birds than in mammals. However, as birds have disproportionately larger hearts for their body mass, these birds showed almost the same stroke volume per gram of heart as do mammals.

On the Respiration of the Killifish Oryzias Latipes

1973 ◽  
Vol 58 (2) ◽  
pp. 305-325
Author(s):  
SHUN-ICHI UMEZAWA ◽  
HIDEKI WATANABE
Keyword(s):  
Oxygen Consumption ◽  
Marked Change ◽  
The Body ◽  
Platinum Electrodes ◽  
Head Region ◽  
Active Electrode ◽  
Small Surface ◽  
Flow Rates ◽  
Ventilatory Frequency ◽  
Gill Opening

1. Factors influencing respiration in this small surface-living freshwater fish (100-290 mg body weight) have been investigated using through-flow respirometers. 2. When the rate of flow over the resting fish is increased, there is an increase in oxygen consumption, but no marked change in ventilatory frequency. Percentage of oxygen removed from the water during its passage over the fish decreases with increase in flow rate in some ranges, and seems to increase again with even greater flow rates notwithstanding a rise in oxygen consumption. 3. The standard oxygen consumption is in the range 250-400 c.c./kg/h at 20°C, and 300-500 c.c./kg/h at 25°C with average flow rates (50-150 c.c./h). 4. Oxygen consumption of the fish is directly related to ambient POO2 over the range 40-500 mmHg. Increases both in ventilatory frequency and in percentage of oxygen removed from the water during its passage over the fish occur during hypoxia, but decrease with increases in ambient POO2 although O2 uptake increases. 5. Ventilatory frequency decreases during darkness and increases in light. After stimulation with light both oxygen consumption and percentage of oxygen removed showed temporary high rates which only gradually subsided. 6. Ventilation volume, measured directly by collecting the water which had passed over the gills, is about 800 c.c./min/kg at 25°C, when the positive hydrostatic pressure is about 5 mm of water. 7. Determinations of gill areas of the fish gave values in the range of 1211-1700 mm2/g weight. The larger values in the fish are probably related to its greater oxygen consumption. 8. Slow potentials associated with respiratory movements were recorded around the head region of the fish by means of external platinum electrodes. When the active electrode was shifted tailwards along the body, the size of the potentials changed, being maximal just posterior to the opercular opening and rather large beside the mouth. The higher values obtained in the potential were 900-1100 µV. The polarity of the potential was reversed at a position anterior to the gill opening.

scholarly journals Rectal–vaginal pressure gradient in patients with pelvic organ prolapse and symptomatic rectocele

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Cheng Tan ◽  
Man Tan ◽  
Jing Geng ◽  
Jun Tang ◽  
Xin Yang
Keyword(s):  
Pelvic Organ Prolapse ◽  
Pressure Gradient ◽  
Obstructed Defecation ◽  
Elevated Pressure ◽  
Pelvic Organ ◽  
Lower Grade ◽  
Translabial Ultrasound ◽  
Rectal Ampulla ◽  
The Relationship ◽  
Posterior Vaginal Prolapse

Abstract Objective The aim of this study is to examine the relationship between rectal–vaginal pressure and symptomatic rectocele in patients with pelvic organ prolapse (POP). Method Patients with posterior vaginal prolapse staged III or IV in accordance with the POP Quantitation classification method who were scheduled for pelvic floor reconstructive surgery in the years 2016–2019 were included in the study. Rectocele was diagnosed using translabial ultrasound, and obstructed defecation (OD) was diagnosed in accordance with the Roma IV diagnostic criteria. Both rectal and vaginal pressure were measured using peritron manometers at maximum Vasalva. To ensure stability, the test was performed three times with each patient. Results A total of 217 patients were enrolled in this study. True rectocele was diagnosed in 68 patients at a main rectal ampulla depth of 19 mm. Furthermore, 36 patients were diagnosed with OD. Symptomatic rectocele was significantly associated with older age (p < 0.01), a higher OD symptom score (p < 0.001), and a lower grade of apical prolapse (p < 0.001). The rectal–vaginal pressure gradient was higher in patients with symptomatic rectocele (37.4 ± 11.7 cm H2O) compared with patients with asymptomatic rectocele (16.9 ± 8.4 cm H2O, p < 0.001), and patients without rectocele (17.1 ± 9.2 cm H2O, p < 0.001). Conclusion The rectal–vaginal pressure gradient was found to be a risk factor for symptomatic rectocele in patients with POP. A rectal–vaginal pressure gradient of > 27.5 cm H2O was suggested as the cut-off point of the elevated pressure gradient.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

scholarly journals Comparison of Optimization-Regulation Algorithms for Secondary Cooling in Continuous Steel Casting

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 237
Author(s):  
Michal Brezina ◽  
Tomas Mauder ◽  
Lubomir Klimes ◽  
Josef Stetina
Keyword(s):  
Convergence Rate ◽  
Water Flow ◽  
Steel Casting ◽  
Casting Process ◽  
Continuous Steel Casting ◽  
Continuous Steel ◽  
Cooling Zone ◽  
Secondary Cooling ◽  
Flow Rates ◽  
Secondary Cooling Zone

The paper presents the comparison of optimization-regulation algorithms applied to the secondary cooling zone in continuous steel casting where the semi-product withdraws most of its thermal energy. In steel production, requirements towards obtaining defect-free semi-products are increasing day-by-day and the products, which would satisfy requirements of the consumers a few decades ago, are now far below the minimum required quality. To fulfill the quality demands towards minimum occurrence of defects in secondary cooling as possible, some regulation in the casting process is needed. The main concept of this paper is to analyze and compare the most known metaheuristic optimization approaches applied to the continuous steel casting process. Heat transfer and solidification phenomena are solved by using a fast 2.5D slice numerical model. The objective function is set to minimize the surface temperature differences in secondary cooling zones between calculated and targeted surface temperatures by suitable water flow rates through cooling nozzles. Obtained optimization results are discussed and the most suitable algorithm for this type of optimization problem is identified. Temperature deviations and cooling water flow rates in the secondary cooling zone, together with convergence rate and operation times needed to reach the stop criterium for each optimization approach, are analyzed and compared to target casting conditions based on a required temperature distribution of the strand. The paper also contains a brief description of applied heuristic algorithms. Some of the algorithms exhibited faster convergence rate than others, but the optimal solution was reached in every optimization run by only one algorithm.

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