Experimental investigations of aeration efficiency in high-head gated circular conduits

2014 ◽  
Vol 69 (6) ◽  
pp. 1275-1281 ◽  
Author(s):  
M. Cihat Tuna ◽  
Fahri Ozkan ◽  
Ahmet Baylar
Keyword(s):  
Froude Number ◽  
Cross Sectional Area ◽  
Experimental Investigations ◽  
Sectional Area ◽  
Flow Area ◽  
Cross Sectional ◽  
Air Bubble ◽  
Aeration Efficiency ◽  
High Head ◽  
Closed Conduit

The primary purpose of water aeration is to increase the oxygen saturation of the water. This can be achieved by using hydraulic structures because of substantial air bubble entrainment at these structures. Closed conduit aeration is a particular instance of this. While there has been a great deal of research on air-demand ratio within closed conduit, very little research has specifically addressed aeration efficiency of closed conduit. In the present work an experimental study was conducted to investigate the aeration efficiency of high-head gated circular conduits. Results showed that high-head gated circular conduits were effective for oxygen transfer. The effects of Froude number and ratio of the water cross-sectional flow area to the conduit cross-sectional area on aeration efficiency were particularly significant, whereas the effect of conduit length was only moderate. Further, a design formula for the aeration efficiency was presented relating the aeration efficiency to ratio of water cross-sectional flow area to conduit cross-sectional area and Froude number. The obtained results will be useful in future modeling processes and aid the practicing engineer in predicting aeration efficiency for design purposes.

Optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits

2014 ◽  
Vol 70 (5) ◽  
pp. 871-877 ◽  
Author(s):  
Fahri Ozkan ◽  
M. Cihat Tuna ◽  
Ahmet Baylar ◽  
Mualla Ozturk
Keyword(s):  
Froude Number ◽  
High Speed ◽  
Water Mixture ◽  
High Speed Flow ◽  
Mixture Flow ◽  
Speed Flow ◽  
Aeration Efficiency ◽  
High Head ◽  
Closed Conduit ◽  
Air Vent

Oxygen is an important component of water quality and its ability to sustain life. Water aeration is the process of introducing air into a body of water to increase its oxygen saturation. Water aeration can be accomplished in a variety of ways, for instance, closed-conduit aeration. High-speed flow in a closed conduit involves air-water mixture flow. The air flow results from the subatmospheric pressure downstream of the gate. The air entrained by the high-speed flow is supplied by the air vent. The air entrained into the flow in the form of a large number of bubbles accelerates oxygen transfer and hence also increases aeration efficiency. In the present work, the optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits was studied experimentally. Results showed that aeration efficiency increased with the air-demand ratio to a certain point and then aeration efficiency did not change with a further increase of the air-demand ratio. Thus, there was an optimum value for the air-demand ratio, depending on the Froude number, which provides maximum aeration efficiency. Furthermore, a design formula for aeration efficiency was presented relating aeration efficiency to the air-demand ratio and Froude number.

Investigation of a Diffuser-Volute Combination With Variable Cross-Sectional Area for Centrifugal Fans

2016 ◽  
Author(s):  
Tore Fischer ◽  
Manuel Rudersdorf ◽  
Sebastian Burgmann ◽  
Thorsten kleine Sextro ◽  
Joerg R. Seume
Keyword(s):  
Numerical Models ◽  
Cross Sectional Area ◽  
Experimental Investigations ◽  
Variable Cross ◽  
Centrifugal Fan ◽  
Sectional Area ◽  
Cross Sectional ◽  
Centrifugal Fans ◽  
Flow Mechanisms ◽  
Dynamics Simulations

The present paper focuses on the potential efficiency improvements and the stable operating range of a centrifugal fan for fuel cell applications. Improvements will be achieved by variability of the cross-sectional area of diffuser and volute by use of a moving backplate. The investigation consists of three parts: The first part describes the design and the performance prediction of a diffuser-volute combination with a variable cross-sectional area, based on empirical correlations and low-resolution CFD (Computational Fluid Dynamics) simulations. For the second part, high-resolution 360 degree CFD simulations are used to gain deeper insight into the flow mechanisms and their influence on fan performance. The last part presents the experimental investigations carried out to validate the numerical models. For this purpose, a demonstrator of the fan including a diffuser-volute combination with variable cross-sectional area is manufactured and investigated using optical PIV (Particle Image Velocimetry) measurements.

scholarly journals Evaluation of the Possibility of Performing Cold Backward Extrusion of Axisymmetrical Thinwalled Aluminum Die Stampings with Square Section / Ocena Możliwości Wyciskania Przeciwbieżnego Na Zimno Osiowosymetrycznych Wyprasek Z Cienką Ścianką O Przekroju Kwadratowym Z Aluminium

2015 ◽  
Vol 60 (4) ◽  
pp. 3043-3050 ◽  
Author(s):  
T. Miłek ◽  
B. Kowalik ◽  
B. Kuliński
Keyword(s):  
Mechanical Properties ◽  
Flow Curve ◽  
Computer Modelling ◽  
Cross Sectional Area ◽  
Experimental Investigations ◽  
Sectional Area ◽  
Cross Sectional ◽  
Industrial Practice ◽  
Backward Extrusion ◽  
Thin Walled

The paper presents evaluation of the possibility of performing cold backward extrusion of axisymmetrical thin-walled aluminum (Al 99.50, ENAW-1050A) die stampings with a square section at the strain ε=ln(A0/A1)=2 (where A0 - cross sectional area of the billet, A1 - cross sectional area of the die stamping), and the ratio h1/b=3.6 (where h1 - height of the die stamping in mm, b - width of the base of the die stamping in mm). The analysis was conducted on the basis of the results of computer modelling (FEM) and experimental investigations on backward extrusion. The boundary conditions for numerical calculations were determined experimentally with respect to the flow curve and mechanical properties of aluminum. The results of investigations into backward extrusion of thin-walled square-sectioned aluminum die stampings might be used as guidelines to develop a technological process for industrial practice.

scholarly journals Modeling of Subcooled Flow Boiling with Nanoparticles under the Influence of a Magnetic Field

Symmetry ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1275 ◽  
Author(s):  
Mohammad Abdollahzadeh Jamalabadi ◽  
Milad Ghasemi ◽  
Rezvan Alamian ◽  
Somchai Wongwises ◽  
Masoud Afrand ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Froude Number ◽  
Volume Fraction ◽  
Flow Boiling ◽  
Fluid Velocity ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow

Subcooled flow boiling is one of the major issues in the nuclear and power generation industries. If the fluid inlet temperature in the boiling area is less than the boiling temperature, the boiling process is called subcooled boiling. The symmetry of a physical system is a constant property of the system and is fixed by deformation. Using magnetohydrodynamic (MHD) forces and broken symmetry induced by nanosized particles, fluid and thermal systems can be more controlled. In this study, the effect of a magnetic field and nanoparticles on subcooled flow boiling in a vertical tube was investigated. For this purpose, a one-dimensional numerical code was used to simulate the flow and variations of various parameters that have been investigated and evaluated. The results showed that as the flow entered the heated area, the vapor volume fraction, Froude number, fluid cross-sectional area forces, mixture velocity, fluid velocity, bubble departure diameter, liquid and vapor Reynolds numbers, squared ratio of the Froude number to the Weber number, and fluid cross-sectional area forces coefficient increased. In the same region, the Eötvös number, root mean square (RMS) of the fluid cross-sectional area force, sound velocity, liquid superficial velocity, critical tube diameter, bubble departure frequency, and density of the active nucleation site were reduced. It was also observed that after the heated area and under the influence of the magnetic field and the nanoparticles, the values of the vapor volume fraction, Froude number, fluid cross-sectional area force, mixture velocity, fluid velocity, vapor, liquid Reynolds number, and squared ratio of the Froude number to the Weber number were decreased. Moreover, there was no significant effect on the Eötvös number, liquid superficial velocity, Taylor bubble Sauter mean diameter, bubble departure diameter, critical tube diameter, bubble departure frequency, or density of the active nucleation site.

Effect of the spatial variation of permeability on air bubble creation and compression

2020 ◽  
Vol 39 (7-8) ◽  
pp. 285-298
Author(s):  
Bouchra Aaboud ◽  
Laurent Bizet ◽  
Abdelghani Saouab ◽  
Yasir Nawab
Keyword(s):  
Cross Sectional Area ◽  
Process Time ◽  
Void Content ◽  
Sectional Area ◽  
Cross Sectional ◽  
Air Bubble ◽  
Bubble Distribution ◽  
Sinusoidal Shape ◽  
Sewing Threads

Tow bundles inside a quasi-unidirectional non-crimp fabric are maintained by sewing threads that induce variation in the bundles’ shape. Indeed, the sewing threads apply a light clamping force that gives a periodical and sinusoidal shape to the tow’s cross-sectional area. This tow cross-sectional area heterogeneity, as a function of position in the fabric, induces a variation of the permeability values. Consequently, while injecting liquid into the fibrous bed, preform's impregnation is influenced as well as the fabric’s void content. The aim of this paper is to consider the effect of tow cross-sectional area heterogeneity on the quality of the manufactured composite part. It leads to reveal the influence of the fibrous reinforcement’s microstructure on the air bubble creation and compression phenomena, especially in terms of process time and the micro and macro air bubble distribution.

116 THE CHARACTERISTICS OF CORPUS LUTEUM SIZE, BLOOD FLOW, AND PLASMA PROGESTERONE CONCENTRATION AFTER OVULATION OF THE FIRST AND SECOND WAVE DOMINANT FOLLICLE

2014 ◽  
Vol 26 (1) ◽  
pp. 172
Author(s):  
R. Miura ◽  
H. Takahashi ◽  
S. Haneda ◽  
M. Matsui
Keyword(s):  
Blood Flow ◽  
Corpus Luteum ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Preovulatory Follicle ◽  
Dominant Follicle ◽  
Flow Area ◽  
Cross Sectional ◽  
Follicular Wave ◽  
And Function

The characteristics of the corpus luteum (CL) are greatly affected by the characteristics of the preceeding preovulatory follicle, such as follicle size and function. A previous study reported that the concentration of oestradiol in follicular fluid and production of androstenedione and progesterone (P4) by cultured theca cells are higher in the first follicular wave dominant follicle than in the second follicular wave dominant follicle. In addition, blood flow in the wall of the preovulatory follicle is higher in the first follicular wave than in the second follicular wave. These results suggest that the characteristics of the dominant follicle in the first and the second follicular wave may be different. The objective of this study was to compare CL characteristics, such as diameter, cross-sectional area, blood flow area, and plasma P4 concentration after ovulation of the dominant follicle between the first and the second follicular waves. Preovulatory follicles and CL formed after ovulation of the first follicular wave (W1; n = 5) and second follicular wave (W2; n = 6) were examined in non-lactating Holstein cows. In W1, PGF2α and GnRH were administrated on D7 and D9 of the oestrus cycle (D0 = oestrus), respectively, to induce follicular maturation. In W2, GnRH was administrated on D6 to induce a new follicular wave; subsequently, PGF2α and GnRH were administrated on D14 and D16, respectively. Diameter and percentage of follicular circumference with blood flow of preovulatory follicle on D10 in W1 and D17 in W2 were measured by transrectal colour Doppler ultrasonography. Diameter, cross-sectional area, and blood flow area of CL formed after ovulation in W1 (W1CL) and W2 (W2CL) were also examined on Day 3, 6, and 9 after ovulation (Day 1 = ovulation day). Blood samples were collected from Day 1 to 9 for P4 measurement. Quantitative end-points for diameter and percentage of follicular circumference with blood flow of the preovulatory follicle were analysed between the groups by using the unpaired Student's t-test. Diameter, cross-sectional area, blood flow area of CL, and plasma P4 concentration were analysed by repeated-measures ANOVA followed by Scheffe's F-test as a multiple comparison test. Larger diameter and higher percentage of follicular circumference with blood flow of the preovulatory follicle were observed in W1 compared with those in W2 (P < 0.01). Diameter of CL was larger in W1CL than in W2CL regardless of day (P < 0.001). Cross-sectional area of CL was larger in W1CL than in W2CL on Day 6 and 9 but not on Day 3. Blood flow area of CL was larger in W1CL than in W2CL on Day 3 and 6 but not in Day 9. Plasma P4 concentrations were higher in W1CL than in W2CL on Day5 and 7 (P < 0.05). In conclusion, larger size and higher percentage of follicular circumference with blood flow of preovulatory follicle in W1 lead to a larger size and a blood flow area of CL as well as higher plasma P4 concentration. These results suggest that preovulatory blood flow status affects the morphology and function of CL.

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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