Source and boundary condition effects on unconfined and confined vertically distributed turbulent plumes

2018 ◽  
Vol 850 ◽  
pp. 1032-1065 ◽  
Author(s):  
N. B. Kaye ◽  
P. Cooper
Keyword(s):  
Volume Flow Rate ◽  
Volume Flow ◽  
Buoyancy Flux ◽  
Boundary Effects ◽  
Volume Flux ◽  
Distributed Source ◽  
Physical Geometry ◽  
Self Similar ◽  
The Mean ◽  
The Impact

Plumes generated by vertically distributed sources of buoyancy have been observed to have substantially lower entrainment coefficients than their equivalent-geometry constant buoyancy flux plumes. Two differences between distributed and localized sources of buoyancy are the presence of a wall shear stress at the source and that non-ideal source conditions are distributed over the whole height of the enclosure for a vertically distributed source. Herein the impact of non-ideal source and boundary conditions on vertically distributed plumes is analysed. It is shown that, at small heights, the plume volume flow rate is significantly influenced by the wall-source volume flux. At larger heights the wall-source buoyancy is greater than the mean plume buoyancy, creating a non-self-similar horizontal buoyancy distribution within the plume. Recent experiments into the behaviour of a vertically distributed source of buoyancy in a confined region have also shown that the plume partially detrains in the stratified region of the enclosure. This detrainment has not been observed for constant buoyancy flux plumes in a confined region. Although models have been proposed to quantify the detrainment process, it is still unclear why vertically distributed buoyancy sources detrain while constant buoyancy flux plumes do not in the same physical geometry. The impact of source and boundary effects on previously published experiments on vertically distributed plumes are reviewed and the possible implications for plume entrainment and detrainment are discussed.

Thermal Performance Intensification of Car Radiator using SiO2/Water and ZnO/Water Nanofluids

2021 ◽  
pp. 1-25
Author(s):  
Hussein Maghrabie ◽  
Hamouda Mousa
Keyword(s):  
Heat Transfer ◽  
Working Conditions ◽  
Flow Rate ◽  
Thermal Performance ◽  
Cooling System ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Coolant Temperature ◽  
Inlet Temperature ◽  
The Impact

Abstract Recent progress in nanotechnology has lead to a revolution in the automotive cooling system. In the present work, enhancement of car radiator thermal performance was investigated using different nanofluids named SiO2/water, ZnO/water nanofluids as cooling mediums. The present study mainly aims to investigate the impact of (5 wt.%) from SiO2 and ZnO nanoparticles (NPs) dispersed in water based on car radiator heat transfer with spherical and hexagonal morphology, respectively. The experiments were performed in two working conditions of the nanofluids i.e coolant temperature and volume flow rate, moreover the present results were compared with the previous studies. The experimental working conditions were set at coolant inlet temperature (tc,i) ranged from 45 oC to 80 oC and the coolant volume flow rate (V) ranged from 3.5 lit/min to 6.5 lit/min. The experimental results show that the hexagonal ZnO/water nanofluid was superior towards enhancement of car radiator thermal performance comparing to that of SiO2 NPs. Additionally, at 6.5 lit/min and 45 °C, the enhancements of car radiator effectiveness due to using SiO2 and ZnO based water nanofluids and compared with that for the based water were 13.9% and 16%, respectively. The present study used the multiple regression analysis (MRA) and hence empirical correlations are suggested to estimate the overall heat transfer coefficient (U) for all coolants as functions of volume flow rate (V) and the coolant inlet temperature (tc,i) with a maximum STDEV of ± 1.85%.

Parameters Dependence of Fibers Diameter and Pores Area in Electrospinning

2018 ◽  
Vol 26 ◽  
pp. 67-73 ◽  
Author(s):  
Emilija Zdraveva ◽  
Budimir Mijovic
Keyword(s):  
Flow Rate ◽  
Polyethylene Oxide ◽  
Volume Flow Rate ◽  
Processing Parameters ◽  
Critical Value ◽  
Volume Flow ◽  
Production Technique ◽  
The World ◽  
The Mean ◽  
Two Parameters

Electrospinning has become the most popular nanofibers production technique that many scientists around the world were intrigued by. It is based on electrostatic forces stretching a polymer solution that undergoes bending instability and eventually results in number of fine nanoscaled filaments. The study reports of four processing parameters effect on electrospun polyethylene oxide (PEO) fibers diameter and pores area. Fibers diameter increase results from the increase of time, volume flow rate and tip to collector distance with a critical value of the first two parameters. The pores area showed both decrease and increase after a critical value of the electrical voltage at 19 kV, while the mean pores area decreased with the time increase. Irregular trends of increasing and decreasing trends of the means pores area were noticed with the change of the volume flow rate and tip to collector distance..

scholarly journals CONTROLLED LIFTING THE BELL OF THE STATE PRIMARY GAS VOLUME AND VOLUME FLOW RATE STANDARD

2021 ◽  
pp. 131-134
Author(s):  
Denys Serediuk ◽  
Yuriy Pelikan ◽  
Oleksandr Bas ◽  
Roman Manulyak
Keyword(s):  
Flow Rate ◽  
Volume Flow Rate ◽  
Primary Standard ◽  
Volume Flow ◽  
Excess Pressure ◽  
The State ◽  
Inert Gases ◽  
Air Purification ◽  
Gas Volume ◽  
The Impact

The article describes the implemented system of pneumatic lifting of the bell of the state primary standard gas volume and volume flow rate units. The system is composed of unified elements of industrial air preparation. There are elements for air purification in front of the compressor, dehumidifier, refrigerator dryer. With the use of a pneumatic system, the bell can be filled with prepared air with different values of excess pressure. The system is installed as a backup to the current to increase security. Pneumatic lifting of the bell allows you to connect a set of cylinders with pure inert gases or mixtures thereof to determine the impact on the gas meters metrological characteristics.

scholarly journals Direct Measurements of the Volume Flow Rate and Emissions in a Large Naturally Ventilated Building

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6223
Author(s):  
David Janke ◽  
Qianying Yi ◽  
Lars Thormann ◽  
Sabrina Hempel ◽  
Barbara Amon ◽  
...  
Keyword(s):  
Flow Rate ◽  
Laser Doppler Anemometry ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Normal Velocity ◽  
Tracer Gas ◽  
Flame Ionization ◽  
Constant Height ◽  
Emission Estimation ◽  
The Mean

The direct measurement of emissions from naturally ventilated dairy barns is challenging due to their large openings and the turbulent and unsteady airflow at the inlets and outlets. The aim of this study was to quantify the impacts of the number and positions of sensors on the estimation of volume flow rate and emissions. High resolution measurements of a naturally ventilated scaled building model in an atmospheric boundary layer wind tunnel were done. Tracer gas was released inside the model and measured at the outlet area, using a fast flame ionization detector (FFID). Additionally, the normal velocity on the area was measured using laser Doppler anemometry (LDA). In total, for a matrix of 65 × 4 sensor positions, the mean normal velocities and the mean concentrations were measured and used to calculate the volume flow rate and the emissions. This dataset was used as a reference to assess the accuracy while systematically reducing the number of sensors and varying the positions of them. The results showed systematic errors in the emission estimation up to +97%, when measurements of concentration and velocity were done at one constant height. This error could be lowered under 5%, when the concentrations were measured as a vertical composite sample.

Studies of Flow Induced on a Water Surface due to the Impingement of a Drop or a Water Source

2017 ◽  
Author(s):  
Naga Musunuri ◽  
Islam Benouaguef ◽  
Edison Amah ◽  
Denis Blackmore ◽  
Ian S. Fischer ◽  
...  
Keyword(s):  
Fresh Water ◽  
Particle Image ◽  
Water Drop ◽  
Volume Flow Rate ◽  
Water Source ◽  
Volume Flow ◽  
Piv Technique ◽  
Image Velocimetry ◽  
Line Passing ◽  
The Impact

The particle image velocimetry (PIV) technique is used to study the flow induced on the surface of a salt waterbody when a drop impinges on the surface or when a source is present on the surface. The measurements show that the impingement of a fresh water drop causes a strong axisymmetric solutocapillary flow about the vertical line passing through the center of impact. The fluid directly below the center of impact rises upward, and near the surface, it moves away from the center of impact. The flow, which develops within a fraction of second after the impact, persists for several seconds. Similarly, when a fresh water source is present on a salt waterbody there is a solutocapillary flow which on the surface is away from the source and below the surface is towards the source. The solutocapillary flow is quasi-steady when the volume flow rate from the source is small in the sense that the salt concentration in the waterbody changes slowly.

scholarly journals IMPACT OF CHANGING ABSORBER SHAPE ON AN AIR FLOW BEHAVIOR IN A THERMO-SOLAR CONVERTER

2021 ◽  
Vol 5 (6) ◽  
pp. 74-86
Author(s):  
Hamidou Benzenine ◽  
Said Abboudi ◽  
Rachid Saim
Keyword(s):  
Numerical Study ◽  
Volume Flow Rate ◽  
Flow Behavior ◽  
Volume Flow ◽  
Low Flow ◽  
Solar Air Heater ◽  
Flow Rates ◽  
Average Temperature ◽  
Axial Variation ◽  
The Impact

In this paper, a two-dimensional numerical study of heat exchange by forced convection of an incompressible laminar flow in a solar air heater duct (SAH), which is equipped with a shoulder attached to the absorber, was performed. The impact of three locations of this shoulder and their three heights on friction losses, as well as the drag coefficient, the variations of velocity, and temperature at the exit section of the SAH, were analyzed for a volume flow rate in the range [20-80 m3/h.]. The results obtained numerically prove that the insertion of a shoulder on the absorber improves the heat transfer and the dynamics of the flow very significantly. An average temperature difference (inlet-outlet) of the collector of 23.51 °C at 29.94 °C and 50.64 °C at 67.53 °C is acquired respectively for the high and the low flow rates. This paper also showed that the height of the shoulder used can ensure an acceleration of the flow with an axial variation of the order of 1.25 up to 2.5 times (> twice) compared with the simple case.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

Novel epoxy/anhydride alternatives for biological electron microscopy: Physical and performance characteristis of embed 812 and LX 112 in combination with NSA/NMA/DMAE

1989 ◽  
Vol 47 ◽  
pp. 1000-1001
Author(s):  
Joe A. Mascorro ◽  
Gerald S. Kirby
Keyword(s):  
Electron Microscopy ◽  
Flow Rate ◽  
Succinic Anhydride ◽  
Volume Flow Rate ◽  
Mass Density ◽  
Uranyl Acetate ◽  
Volume Flow ◽  
Base Resin ◽  
And Performance ◽  
Acid Anhydrides

Embedding media based upon an epoxy resin of choice and the acid anhydrides dodecenyl succinic anhydride (DDSA), nadic methyl anhydride (NMA), and catalyzed by the tertiary amine 2,4,6-Tri(dimethylaminomethyl) phenol (DMP-30) are widely used in biological electron microscopy. These media possess a viscosity character that can impair tissue infiltration, particularly if original Epon 812 is utilized as the base resin. Other resins that are considerably less viscous than Epon 812 now are available as replacements. Likewise, nonenyl succinic anhydride (NSA) and dimethylaminoethanol (DMAE) are more fluid than their counterparts DDSA and DMP- 30 commonly used in earlier formulations. This work utilizes novel epoxy and anhydride combinations in order to produce embedding media with desirable flow rate and viscosity parameters that, in turn, would allow the medium to optimally infiltrate tissues. Specifically, embeding media based on EmBed 812 or LX 112 with NSA (in place of DDSA) and DMAE (replacing DMP-30), with NMA remaining constant, are formulated and offered as alternatives for routine biological work.Individual epoxy resins (Table I) or complete embedding media (Tables II-III) were tested for flow rate and viscosity. The novel media were further examined for their ability to infilftrate tissues, polymerize, sectioning and staining character, as well as strength and stability to the electron beam and column vacuum. For physical comparisons, a volume (9 ml) of either resin or media was aspirated into a capillary viscocimeter oriented vertically. The material was then allowed to flow out freely under the influence of gravity and the flow time necessary for the volume to exit was recored (Col B,C; Tables). In addition, the volume flow rate (ml flowing/second; Col D, Tables) was measured. Viscosity (n) could then be determined by using the Hagen-Poiseville relation for laminar flow, n = c.p/Q, where c = a geometric constant from an instrument calibration with water, p = mass density, and Q = volume flow rate. Mass weight and density of the materials were determined as well (Col F,G; Tables). Infiltration schedules utilized were short (1/2 hr 1:1, 3 hrs full resin), intermediate (1/2 hr 1:1, 6 hrs full resin) , or long (1/2 hr 1:1, 6 hrs full resin) in total time. Polymerization schedules ranging from 15 hrs (overnight) through 24, 36, or 48 hrs were tested. Sections demonstrating gold interference colors were collected on unsupported 200- 300 mesh grids and stained sequentially with uranyl acetate and lead citrate.

Sound Production Treatment for Acquired Apraxia of Speech: An Examination of Dosage in Relation to Probe Performance

2020 ◽  
pp. 1-16
Author(s):  
Julie L. Wambaugh ◽  
Lydia Kallhoff ◽  
Christina Nessler
Keyword(s):  
Retrospective Analysis ◽  
Sound Production ◽  
Apraxia Of Speech ◽  
Practice Schedule ◽  
Practice Schedules ◽  
Baseline Performance ◽  
The Mean ◽  
Number Of Treatment ◽  
The Impact

Purpose This study was designed to examine the association of dosage and effects of Sound Production Treatment (SPT) for acquired apraxia of speech. Method Treatment logs and probe data from 20 speakers with apraxia of speech and aphasia were submitted to a retrospective analysis. The number of treatment sessions and teaching episodes was examined relative to (a) change in articulation accuracy above baseline performance, (b) mastery of production, and (c) maintenance. The impact of practice schedule (SPT-Blocked vs. SPT-Random) was also examined. Results The average number of treatment sessions conducted prior to change was 5.4 for SPT-Blocked and 3.9 for SPT-Random. The mean number of teaching episodes preceding change was 334 for SPT-Blocked and 179 for SPT-Random. Mastery occurred within an average of 13.7 sessions (1,252 teaching episodes) and 12.4 sessions (1,082 teaching episodes) for SPT-Blocked and SPT-Random, respectively. Comparisons of dosage metric values across practice schedules did not reveal substantial differences. Significant negative correlations were found between follow-up probe performance and the dosage metrics. Conclusions Only a few treatment sessions were needed to achieve initial positive changes in articulation, with mastery occurring within 12–14 sessions for the majority of participants. Earlier occurrence of change or mastery was associated with better follow-up performance. Supplemental Material https://doi.org/10.23641/asha.12592190

Slip And Hall Effects On The Flow Of A Hyperbolic Tangent Fluid Through Porous Medium In A Planar Channel With Peristalsis

GIS Business ◽  
2020 ◽  
Vol 15 (1) ◽  
pp. 383-394
Author(s):  
K. Shalini ◽  
K.Rajasekhar
Keyword(s):  
Porous Medium ◽  
Pressure Gradient ◽  
Volume Flow Rate ◽  
Perturbation Technique ◽  
Volume Flow ◽  
Planar Channel ◽  
Hyperbolic Tangent ◽  
Closed Form Solutions ◽  
Long Wavelength ◽  
Hall Effects

In this paper, the effect of Slip and Hall effects on the flow of Hyperbolic tangent fluid through a porous medium in a planar channel with peristalsis under the assumption of long wavelength is investigated. A Closed form solutions are obtained for axial velocity and pressure gradient by employing perturbation technique. The effects of various emerging parameters on the pressure gradient, time averaged volume flow rate and frictional force are discussed with the aid of graphs.

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