Influence of Nozzle Aspect Ratio and Orientation on Flow Characteristics of Multiple Elliptic Jets

2019 ◽  
Author(s):  
Hiroshi Teramoto ◽  
Takahiro Kiwata ◽  
Kako Yajima
Keyword(s):  
Flow Characteristics ◽  
The Self ◽  
Equivalent Diameter ◽  
Hot Wire ◽  
Ambient Fluid ◽  
Aspect Ratios ◽  
Multiple Jets ◽  
Induced Flow ◽  
The Mean ◽  
Axis Switching

Abstract An experimental study is conducted to investigate the flow characteristics of multiple elliptic jets issuing from a 6 × 6 nozzle array at a relatively low-Reynolds number (Re = 4.3 × 103). Two aspect ratios of the multiple elliptic nozzles (equivalent diameter, de, of a nozzle was 6 mm), namely a/b = 2.25 and 6.25, where a and b are the radii of the major and minor axes of an elliptic nozzle, respectively, and two nozzle azimuthal orientations, namely the same and alternate azimuthal orientation arrangements, were used. The mean and fluctuating velocities were measured using a constant-temperature hot-wire anemometer. The multiple jets located at the side of the ambient fluid were stretched due to interactions between the self-induced flow of an elliptic vortex ring and the secondary flow caused by the entrainment of the ambient fluid. For a/b = 2.25, axis switching occurred only once in the range of 1 < x/de ≤ 3 for both nozzle azimuthal orientations. For a/b = 6.25 and the same azimuthal orientation arrangement, axis switching occurred only once at 3 < x/de ≤ 5; axis switching did not occur for the alternate azimuthal orientation arrangement. Thus, the flow characteristics of multiple elliptic jets are influenced by the azimuthal orientation of adjoining nozzles.

Flow characteristics of two-dimensional synthetic jets under diaphragm resonance excitation

2019 ◽  
Vol 91 (4) ◽  
pp. 575-581 ◽  
Author(s):  
Chi-Yu Lin ◽  
Jih Lung Lin
Keyword(s):  
Flow Field ◽  
Flow Characteristics ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Hot Wire ◽  
Content Type ◽  
Velocity Response ◽  
The Mean ◽  
Excitation Waveform ◽  
40 Hz

Purpose This paper aims to experimentally study the external flow characteristic of an isolated two-dimensional synthetic jet actuator undergoing diaphragm resonance. Design/methodology/approach The resonance frequency of the diaphragm (40 Hz) depends on the excitation mechanism in the actuator, whereas it is independent of cavity geometry, excitation waveform and excitation voltage. The velocity response of the synthetic jet is influenced by excitation voltage rather than excitation waveform. Thus, this investigation selected four different voltages (5, 10, 15 and 20 V) under the same sine waveform as experiment parameters. Findings The velocity field along the downstream direction is classified into five regions, which can be obtained by hot-wire measurement. The first region refers to an area in which flow moves from within the cavity to the exit of orifice through the oscillation of the diaphragm, but prior to the formation of the vortex of a synthetic jet. In this region, two characteristic frequencies exist at 20 and 40 Hz in the flow field. The second region refers to the area in which the vortices of a synthetic jet fully develop following their initial formation. In this region, the characteristic frequencies at 20 and 40 Hz still occur in the flow field. The third region refers to the area in which both fully developed vortices continue traveling downstream. It is difficult to obtain the characteristic frequency in this flow field, because the mean center velocities (ū) decay downstream and are proportional to (x/w)−1/2 for the four excitation voltages. The fourth region reveals variations in both vortices as they merge into a single vortex. The mean center velocities (ū) are approximately proportional to (x/w)0 in this region for the four excitation voltages. A fifth region deals with variations in the vortex of a synthetic jet after both vortices merge into one, in which the mean center velocities (ū) are approximately proportional to (x/w)−1 in this region for the four excitation voltages (x/w is the dimensionless streamwise distance). Originality/value Although the flow characteristics of synthetic jets had reported for flow control in some literatures, variations of flow structure for synthetic jets are still not studied under the excitation of diaphragm resonance. This paper showed some novel results that our velocity response results obtained by hot-wire measurement along the downstream direction compared with flow visualization resulted in the classification of five regions under the excitation of diaphragm resonance. In the future, it makes valuable contributions for experimental findings to provide researchers with further development of flow control.

Effect of Aspect Ratios on the Performance Characteristics of Air Amplifier

2015 ◽  
Author(s):  
Jeong-Min Lee ◽  
Yi-Seul Jo ◽  
Sung-Min Kim ◽  
Youn-Jea Kim
Keyword(s):  
Shear Stress ◽  
Total Pressure ◽  
Applied Pressure ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Compressed Air ◽  
Turbulent Model ◽  
Aspect Ratios ◽  
Ansys Cfx ◽  
Induced Flow

In this study, the flow characteristics of the Coandă nozzle were studied with various values of the aspect ratio of induced flow inlet to outlet. Furthermore, four different applied pressure conditions of compressed air were also considered. Numerical analysis was performed using the commercial CFD code, ANSYS CFX with a shear stress transport (SST) turbulent model. The results of total pressure and velocity distributions were graphically depicted with various geometrical configurations and operating conditions.

A Comparison of Physiological Demand between Self-Propelled and Motorized Treadmill Exercise

2018 ◽  
Vol 7 (4) ◽  
pp. 13-21
Author(s):  
Todd Backes ◽  
Charlene Takacs
Keyword(s):  
Respiratory Exchange Ratio ◽  
Treadmill Exercise ◽  
Cardiopulmonary Exercise Testing ◽  
Mean Value ◽  
The Self ◽  
Mixing Chamber ◽  
Wide Range ◽  
The Subject ◽  
The Mean ◽  
Computer Controlled

There are a wide range of options for individuals to choose from in order to engage in aerobic exercise; from outdoor running to computer controlled and self-propelled treadmills. Recently, self-propelled treadmills have increased in popularity and provide an alternative to a motorized treadmill. Twenty subjects (10 men, 10 women) ranging in age from 19-23 with a mean of 20.4 ± 0.8 SD were participants in this study. The subjects visited the laboratory on three occasions. The purpose of the first visit was to familiarize the subject with the self-propelled treadmill (Woodway Curve 3.0). The second visit, subjects were instructed to run on the self-propelled treadmill for 3km at a self-determined pace. Speed data were collected directly from the self-propelled treadmill. The third visit used speed data collected during the self-propelled treadmill run to create an identically paced 3km run for the subjects to perform on a motorized treadmill (COSMED T150). During both the second and third visit, oxygen consumption (VO2) and respiratory exchange ratio (R) data were collected with COSMED’s Quark cardiopulmonary exercise testing (CPET) metabolic mixing chamber system. The VO2 mean value for the self-propelled treadmill (44.90 ± 1.65 SE ml/kg/min) was significantly greater than the motorized treadmill (34.38 ± 1.39 SE ml/kg/min). The mean R value for the self-propelled treadmill (0.91 ± 0.01 SE) was significantly greater than the motorized treadmill (0.86 ± 0.01 SE). Our study demonstrated that a 3km run on a self-propelled treadmill does elicit a greater physiological response than a 3km run at on a standard motorized treadmill. Self-propelled treadmills provide a mode of exercise that offers increased training loads and should be considered as an alternative to motorized treadmills.

scholarly journals Experimental study on the mean flow characteristics of a supersonic multiple jet configuration

2021 ◽  
Vol 108 ◽  
pp. 106377
Author(s):  
Mohammed Faheem ◽  
Aqib Khan ◽  
Rakesh Kumar ◽  
Sher Afghan Khan ◽  
Waqar Asrar ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Characteristics ◽  
Mean Flow ◽  
The Mean

COLONY OF THE FUNGUS Aspergillus oryzae AND SELF-AFFINE FRACTAL GEOMETRY OF GROWTH FRONTS

Fractals ◽  
1993 ◽  
Vol 01 (01) ◽  
pp. 11-19 ◽  
Author(s):  
SHU MATSUURA ◽  
SASUKE MIYAZIMA
Keyword(s):  
Aspergillus Oryzae ◽  
Environmental Conditions ◽  
Fractal Geometry ◽  
Nutrient Concentration ◽  
Incubation Temperature ◽  
Characteristic Exponent ◽  
Growth Front ◽  
Favorable Condition ◽  
The Self ◽  
The Mean

A variety of colony shapes of the fungus Aspergillus oryzae under varying environmental conditions such as the nutrient concentration, medium stiffness and incubation temperature are obtained, ranging from a homogeneous Eden-like to a ramified DLA-like pattern. The roughness σ(l, h) of the growth front of the band-shaped colony, where h is the mean front height within l of the horizontal range, satisfies the self-affine fractal relation under favorable environmental conditions. In the most favorable condition of our experiments, its characteristic exponent is found to be a little larger than that of the 2-dimensional Eden model.

scholarly journals Interactions between Tandem Cylinders in an Open Channel: Impact on Mean and Turbulent Flow Characteristics

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1718
Author(s):  
Hasan Zobeyer ◽  
Abul B. M. Baki ◽  
Saika Nowshin Nowrin
Keyword(s):  
Turbulent Flow ◽  
Open Channel ◽  
Recirculation Zone ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Flow Recirculation ◽  
Tandem Cylinders ◽  
Flow Development ◽  
The Mean ◽  
Recirculation Length

The flow hydrodynamics around a single cylinder differ significantly from the flow fields around two cylinders in a tandem or side-by-side arrangement. In this study, the experimental results on the mean and turbulence characteristics of flow generated by a pair of cylinders placed in tandem in an open-channel flume are presented. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components. This study investigated the effect of cylinder spacing at 3D, 6D, and 9D (center to center) distances on the mean and turbulent flow profiles and the distribution of near-bed shear stress behind the tandem cylinders in the plane of symmetry, where D is the cylinder diameter. The results revealed that the downstream cylinder influenced the flow development between cylinders (i.e., midstream) with 3D, 6D, and 9D spacing. However, the downstream cylinder controlled the flow recirculation length midstream for the 3D distance and showed zero interruption in the 6D and 9D distances. The peak of the turbulent metrics generally occurred near the end of the recirculation zone in all scenarios.

Effect of Self - Care Program on the Self- Esteem of Multiple Sclerosis Patients

2009 ◽  
Vol 24 (S1) ◽  
pp. 1-1
Author(s):  
H. Madani ◽  
H. Navipoor ◽  
P. Roozbayani
Keyword(s):  
Multiple Sclerosis ◽  
Self Care ◽  
Care Program ◽  
Self Esteem ◽  
The Self ◽  
Self Report ◽  
The Mean ◽  
Muscular Spasm ◽  
Multiple Sclerosis Patients ◽  
Paired T Test

Aims:According to decreased self- esteem in multiple sclerosis (MS) patients, it is necessary to utilize appropriate methods in order to improve self- esteem in MS patients. So this study was conducted on patients with MS supported by the Iranian MS society for determining the effect of self - care program on their self- esteem.Method:In this semi - experimental study 34 patients with MS who were not in the acute phase of disease were selected. The data were collected via personal questionnaires, problem list, Cooper and smith standard questionnaire for self- esteem and self report check lists. Self - care program(self - care for muscular spasm, fatigue, constipation and amnesia and …) was educated, then it was performed for one month period and the data were analyzed using paired t- test, wilcoxon, croscal - wallis and manwithney tests.Results:Application of self - care program improve the self- esteem and reduced some symptoms such as muscular spasm, fatigue, constipation and amnesia in MS patients. The mean valve of self- esteem increased from 54 before performing the program to 68 after the program ( p < 0.05).Conclusion:Using self-care program can be an effective method for improving self- esteem of MS patients.

scholarly journals Self-care in heart failure patients

2015 ◽  
Vol 23 (4) ◽  
pp. 578-586 ◽  
Author(s):  
Ana Paula da Conceição ◽  
Mariana Alvina dos Santos ◽  
Bernardo dos Santos ◽  
Diná de Almeida Lopes Monteiro da Cruz
Keyword(s):  
Heart Failure ◽  
Self Care ◽  
Left Ventricular ◽  
The Self ◽  
Left Ventricular Ejection ◽  
Ventricular Ejection Fraction ◽  
Failure Index ◽  
Joint Monitoring ◽  
The Mean ◽  
Care Behavior

AbstractObjective: to describe self-care behavior and its associated factors in a sample of heart failure Brazilian patients.Method: descriptive cross-sectional study with non-probabilistic sample of 116 ambulatory patients undergoing heart failure treatment. Self-care was evaluated using the Self-Care of Heart Failure Index, (scores ≥70 points=appropriate self-care). Association tests were applied, considering a descriptive level of 0.05.Results: the mean age of participants was 57.7 (SD =11.3) years; 54.3% were male; the mean schooling was 5.5 (SD = 4.0) years; and 74.1% had functional class II-III. The mean scores on the subscales of the Self-Care of Heart Failure Index indicated inappropriate self-care (self-care maintenance: 53.2 (SD =14.3), selfcare management: 50.0 (SD = 20.3) and self-care confidence: 52.6 (SD=22.7)) and it was found low frequencies of participants with appropriate self-care (self-care maintenance, 6.9%), self-care management (14.7%) and self-care confidence (19%). Higher scores of the Self-Care of Heart Failure Index were associated with: reduced left ventricular ejection fraction (p=0.001), longer time of experience with the disease (p=0.05) and joint monitoring by physician and nurse (p=0.007).Conclusion: investments are needed to improve the self-care behavior and the nursing can play a relevant role in this improvement.

Numerical Simulation of Flow and Heat Transfer in Rectangular Channel With Different Aspect Ratios

2016 ◽  
Author(s):  
Liu Wenhua ◽  
Mo Yang ◽  
Li Ling ◽  
Qiao Liang ◽  
Yuwen Zhang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Aspect Ratio ◽  
Characteristic Length ◽  
Rectangular Channel ◽  
Equivalent Diameter ◽  
Correction Coefficient ◽  
Corner Region ◽  
Flow And Heat Transfer ◽  
Aspect Ratios

Turbulent flow and heat transfer in rectangular channel has an important significance in engineering. Conventional approach to caculate Nusselt number of rectangular channel approximately is to take the equivalent diameter as the characteristic length and use the classic circular channel turbulent heat transfer coefficient correlations. However, under these conditions, the caculation error of Nusselt number can reach to 14% and thus this approach can not substantially describe the variation of Nusselt number of rectangular cross-sections with different aspect ratios. Therefore, caculation by using equivalent diameter as the characteristic length in classic experiment formula needs to be corrected. Seven groups of rectangular channel models with different aspect ratios have been studied numerically in this paper. By using standard turbulence model, the flow and heat transfer law of air with varing properties has been studied in 4 different sets of conditions in Reynolds number. The simulation and experimental results are in good agreement. The simulation results show that with the increase of aspect ratio, the cross-sectional average Nusselt number increased, Nusselt number of circumferential wall distributed more evenly and the difference between the infinite plate channel and square channel went up to 25%. The effects of corner region and long\short sides on heat transfer have also been investigated in this paper. Results show that in rectangular channel, heat transfer in corner region is significantly weaker than it in other region. With the increase of aspect ratio, effect on the long side of heat transfer of the short side is gradually reduced, and then eventually eliminates completely in the infinite flat place. Based on the studies above, correction coefficient for rectangular channels with different aspect ratios has been proposed in this paper and the accuracy of the correction coefficient has been varified by numerical simulations. This can reflect the variation of Nusselt number under different aspect ratios more effectively and thus has current significance for project to calculate Nusselt number of heat transfer in rectangular channel.

Flow Characteristics of Cavitating Jet through a Rectangular Orifice with Different Aspect Ratios

2021 ◽  
Vol 2021.58 (0) ◽  
pp. F021
Author(s):  
Kohei TERAKWA ◽  
Shouichiro IIO ◽  
Kotaro TAKAMURE ◽  
Tomomi UCHIYAMA
Keyword(s):  
Flow Characteristics ◽  
Aspect Ratios ◽  
Cavitating Jet
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