scholarly journals Hydraulic Characteristics of Emerged Rigid and Submerged Flexible Vegetations in the Riparian Zone

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1057
Author(s):  
Xin Meng ◽  
Yubao Zhou ◽  
Zhilin Sun ◽  
Kaixuan Ding ◽  
Lin Chong
Keyword(s):  
Velocity Distribution ◽  
Turbulence Intensity ◽  
Flow Resistance ◽  
Test Method ◽  
Relative Depth ◽  
Distribution Profile ◽  
Experimental Conditions ◽  
Different Types ◽  
Wooden Stick ◽  
Determining Factor

Flow resistance, velocity distribution, and turbulence intensity are significantly influenced by aquatic vegetations (AV) in riparian zones. Understanding the hydraulics of flow with planted floodplains is of great significance for determining the velocity distribution profile and supporting the fluvial processes management. However, the traditional flume experiment method is inefficient. Therefore, the multigroup simultaneous flume test method was carried out to describe the flow patterns affected by emerged rigid (reed and wooden stick) and submerged flexible vegetations (grass and chlorella). The Acoustic Doppler Velocimeter (ADV) was utilized to measure the velocity at one point for different experimental conditions. The results showed that hydraulic features were influenced by different types of vegetation. Furthermore, the relative depth (z/h) was a determining factor of those variations. In addition, the time-averaged velocity distributions of planted floodplains are not logarithmic. Instead, they represented “s-shape” profiles. In detail, for the vegetated floodplains, reed and wood followed an s-shape profile, but for grass and chlorella, they followed reverse s-shape profile. For all cases, turbulence is not isotropic and the change law of turbulence intensity is different in different sections. The flow resistance, turbulence intensities, and Reynold stresses influenced by different types of vegetation were also analyzed.

scholarly journals Experimental Study on the Water Selective Dense Membrane under an Absolute Pressure Difference with Simplified Test Method

2021 ◽  
Vol 11 (4) ◽  
pp. 1710
Author(s):  
Jinwook Lee ◽  
Hyo-Sun Kim ◽  
Donik Ku ◽  
Jihun Lim ◽  
Minkyu Jung ◽  
...  
Keyword(s):  
Measurement Methods ◽  
Test Method ◽  
Coefficient Of Performance ◽  
Absolute Pressure ◽  
Air Conditioner ◽  
Experimental Conditions ◽  
Simple Method ◽  
Performance Factors ◽  
Dense Membrane ◽  
Before And After

Membrane-based vacuum dehumidification technology is currently being actively studied. In most studies, the performance of the membrane-based systems is evaluated under the assumption that the membrane can achieve ideal separation, which results in ideal coefficient of performance (COP) values. However, the performance factors for membranes vary depending on the experimental conditions and measurement methods. Therefore, relevant values can only be calculated if the data are measured in an environment close to that of the application conditions. The cup measurement method is a simple method to measure the permeability, however, there are limitations regarding adding variables during the experiment. To overcome these limitations, a new experimental device was constructed that combines pressurized cell with the cup method. Using the device, the performance of polyethylene-amide-bonded dense membranes was evaluated under conditions where absolute pressure differentials occurred before and after the membrane, such as in air conditioner dehumidification systems.

Early Spelling Acquisition: Does Writing Really Beat the Computer?

1992 ◽  
Vol 15 (3) ◽  
pp. 223-228 ◽  
Author(s):  
Sharon Vaughn ◽  
Jeanne Shay Schumm ◽  
Jane Gordon
Keyword(s):  
Learning Disabled ◽  
Primary Grade ◽  
Group Differences ◽  
Experimental Conditions ◽  
Spelling Acquisition ◽  
Instructional Activity ◽  
Study Results ◽  
Different Types ◽  
Computer Based ◽  
Based Instruction

This research evaluated the efficacy of handwriting, letter tiles, and computer-based instruction on the early spelling acquisition of normal achieving (NLD) and learning disabled (LD) elementary students. The study replicated and extended the Cunningham and Stanovich (1990) study. Forty-eight primary-grade students (24 non-learning disabled; 24 learning disabled) received spelling training under three experimental conditions that involved different types of instructional activity: writing, sorting letter tiles, or typing on the computer. Results indicated no significant differences between the LD and NLD groups on words spelled correctly for any of the three conditions. Since the number of spelling words learned was low across conditions and groups, the number of correctly learned bigrams was examined. No within-group differences emerged for condition (writing, tile, computer); however, significant differences between the groups were found on number of bigrams learned for writing, tile, and computer, with the NLD group outperforming the LD group on all three conditions. Statistically significant time effects for bigrams were also noted for all three conditions. Unlike the Cunningham and Stanovich (1990) study, results did not replicate the superiority of the handwriting condition for the NLD group, nor was the handwriting condition found to be significantly more effective for the LD group.

The thrust measurement system research for combined nozzle in small space

2018 ◽  
Vol 41 (4) ◽  
pp. 1149-1159
Author(s):  
Yonghua Lu ◽  
Jing Li ◽  
Xiang Zhang ◽  
Yang Li
Keyword(s):  
Measurement System ◽  
Force Sensor ◽  
Test Method ◽  
Small Space ◽  
System A ◽  
Calibration Experiment ◽  
Different Types ◽  
Thrust Measurement ◽  
Nozzle Thrust ◽  
Thrust Forces

For measuring the thrust of combined nozzles in satellite thruster with a small space, the test method that the nozzle directly sprays on the load baffle is employed in this paper. The key problem is how to design the positions of 10 load baffles and how to construct the measurement system. A set of complete and automatic nozzle thrust measurement system is designed and built, and the influence of the load baffle applied on the flow field of nozzles is analyzed using the software FLUENT. Furthermore, the load surface locations of the sensors for the different types of nozzles are analyzed. We draw the conclusion that the load baffle position should range from 4–8 mm for the I-type nozzle and range in 6–12 mm for II-type and III-type nozzle. The correction coefficients of the thrust forces for all channels of the measurement system are determined in the calibration experiment. The uncertainty of measurement system is estimated and the error source of the measurement system is traced. We found that the systematic uncertainty is mainly contributed by the A-type uncertainty which is related with the nozzle dimension and its inner structure. The B-type uncertainty of system is contributed by the force sensor.

scholarly journals Combination of Autohydrolysis and Catalytic Hydrolysis of Biomass for the Production of Hemicellulose Oligosaccharides and Sugars

Reactions ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 30-46
Author(s):  
Léa Vilcocq ◽  
Agnès Crepet ◽  
Patrick Jame ◽  
Florbela Carvalheiro ◽  
Luis C. Duarte
Keyword(s):  
Agricultural Waste ◽  
Solid Acid Catalyst ◽  
Acid Catalyst ◽  
Energy Crop ◽  
Catalytic Hydrolysis ◽  
Experimental Conditions ◽  
Different Types ◽  
Hemicellulosic Sugars ◽  
Hydrolysis Of

Three different types of biomass sourced from forestry waste (eucalyptus residues), agricultural waste (wheat straw), and energy crop (miscanthus) were used as starting materials to produce hemicellulosic sugars, furans (furfural and hydroxymethylfurfural), and oligosaccharides. A two-step hybrid process was implemented; biomass was first autohydrolysed without any additive to extract hemicelluloses and dissolve it in water. Then, the hydrolysate was treated with a solid acid catalyst, TiO2-WOx, in order to achieve hydrolysis and produce monomeric sugars and furans. This article investigates the role of the biomass type, autohydrolysis experimental conditions, polymerisation degree and composition of hemicelluloses on the performance of the process coupling autohydrolysis and catalytic hydrolysis. The highest global yields of both oligosaccharides and monomeric sugars were obtained from Eucalyptus (37% and 18%, respectively).

Needle water potential and soil-to-foliage flow resistance during soil drying: a comparison of Douglas-fir, western hemlock, and mountain hemlock

1985 ◽  
Vol 15 (1) ◽  
pp. 185-188 ◽  
Author(s):  
T. M. Ballard ◽  
M. G. Dosskey
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Water Flow ◽  
Flow Resistance ◽  
Soil Water Potential ◽  
Douglas Fir ◽  
Western Hemlock ◽  
Soil Drying ◽  
Experimental Conditions ◽  
Needle Water Potential

Needle water potential in western and mountain hemlock falls as the soil dries, but under our experimental conditions, it remained stable in Douglas-fir. Resistance to water flow from soil to foliage is higher for the hemlocks and increases more steeply as the soil dries. These findings physically account for the observation that water uptake is reduced relatively more for the hemlocks than for Douglas-fir, as soil water potential declines.

Numerical Simulation of Impacts of Different Types of Air Duct Outlets on Ventilation Efficiency

2013 ◽  
Vol 438-439 ◽  
pp. 1098-1103
Author(s):  
Chun Zi Nan ◽  
Ji Ming Ma ◽  
Luo Zhao
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Velocity Distribution ◽  
Flow Velocity ◽  
Numerical Method ◽  
Concentration Effect ◽  
Mixing Zone ◽  
Mixing Effect ◽  
Ventilation Efficiency ◽  
Different Types

To enhance the exhaust efficiency during ventilation, three types of air duct outlets were imported. According to the characteristics of velocity distribution simulated by numerical method, the flow field is divided into the mixing zone and the exhaust zone. The gradual contracted air duct outlet can enhance the mixing effect between fresh air and smoke. In the exhaust zone, however, the flow velocity on the upper section of the tunnel is weakened, which is unfavorable for smoke exhaust. Gradual expanded air duct outlet, on the contrary, may weaken the concentration effect of the airflow. The flow velocity on the upper section of the tunnel is increased in the exhaust zone, thus the flow field is more homogenized, which is in favor of smoke exhaust.

scholarly journals Effects of Free-Stream Turbulence Intensity on a Boundary Layer Recovering From Concave Curvature Effects

1993 ◽  
Author(s):  
Michael D. Kestoras ◽  
Terrence W. Simon
Keyword(s):  
Boundary Layer ◽  
Velocity Distribution ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Outer Region ◽  
Free Stream Turbulence ◽  
Flat Wall ◽  
Curvature Effects ◽  
Turbulent Eddies ◽  
Concave Wall

Experiments are conducted on a flat recovery wall downstream of sustained concave curvature in the presence of high free-stream turbulence (TI∼8%). This flow simulates some of the features of the flow on the latter parts of the pressure surface of a gas turbine airfoil. The combined effects of concave curvature and TI, both present in the flow over a turbine airfoil, have so far little been studied. Computation of such flows with standard turbulence closure models has not been particularly successful. This experiment attempts to characterize the turbulence characteristics of this flow. In the present study, a turbulent boundary layer grows from the leading edge of a concave wall then passes onto a downstream flat wall. Results show that turbulence intensities increase profoundly in the outer region of the boundary layer over the recovery wall. Near-wall turbulent eddies appear to lift off the recovery wall and a “stabilized” region forms near the wall. In contrast to a low-free-stream turbulence intensity flow, turbulent eddies penetrate the outer parts of the “stabilized” region where sharp velocity and temperature gradients exist. These eddies can more readily transfer momentum and heat. As a result, skin friction coefficients and Stanton numbers on the recovery wall are 20% and 10%, respectively, above their values in the low-free-stream turbulence intensity case. Stanton numbers do not undershoot flat-wall expectations at the same ReΔ2 values as seen in the low-TI case. Remarkably, the velocity distribution in the core of the flow over the recovery wall exhibits a negative gradient normal to the wall under high free-stream turbulence intensity conditions. This velocity distribution appears to be the result of two effects: 1) cross transport of kinetic energy by boundary work in the upstream curved flow and 2) readjustment of static pressure profiles in response to the removal of concave curvature.

The influence of some physical characteristics of the milking machine on the rate of new mastitis infections

1973 ◽  
Vol 40 (1) ◽  
pp. 117-129 ◽  
Author(s):  
C. C. Thiel ◽  
Carol L. Cousins ◽  
D. R. Westgarth ◽  
F. K. Neave
Keyword(s):  
Short Duration ◽  
Streptococcus Agalactiae ◽  
The Other ◽  
Vacuum Fluctuations ◽  
Infection Rates ◽  
Experimental Conditions ◽  
Different Types ◽  
Before And After ◽  
Milking Machine ◽  
Do So

SummaryLarge differences in new infection rates occurred with half-udder milking machines in which one half of the cluster operated substantially free from vacuum fluctuations while the other half was subjected to various combinations of different types of fluctuation in vacuum. To increase the rate of new infection all teats were contaminated before and after each milking by immersion in a suspension of Streptococcus agalactiae and Str. dysgalactiae. A series of short-duration trials indicated that neither irregular nor cyclic fluctuations in vacuum acting alone were able to increase new infection rate. However, either the Nyhan and Cowhig irregular fluctuation, or a variant of it in combination with cyclic fluctuations in vacuum, was able to do so under the particular experimental conditions used.

Effects of Trailing Edge Position of Splitter Blade on the Pressure Pulsation in a Low Specific Centrifugal Pump

2019 ◽  
Author(s):  
Jinfeng Zhang
Keyword(s):  
Velocity Distribution ◽  
Turbulence Intensity ◽  
Pressure Fluctuation ◽  
Relative Velocity ◽  
Pressure Pulsation ◽  
Suction Side ◽  
Maximum Pressure ◽  
Trailing Edge ◽  
Flow Rates ◽  
Pulsation Amplitude

Abstract A combination of experimental and numerical simulation was carried out to analyze influence of trailing edge position of splitter blade on the pressure fluctuation in low specific pumps with and without splitter blades under different flow rates. Performance experiments and PIV tests were performed to verify the results of numerical calculation. Several monitor points were placed in the calculation model pump to collect the pressure fluctuation signals, which were processed by Fast Fourier Transform to obtain the frequency results for further analysis. Besides, turbulence intensity and relative velocity distribution were also analyzed in regions of impeller and volute. The results showed that compared with prototype without splitter blade and the splitter blade schemes, when the trailing edge of splitter blade deviates to the suction side of main blade, the maximum pressure pulsation amplitudes are the lowest at different monitoring points of model pump. And the variation of pressure pulsation amplitude in this scheme is relatively stable with the change of flow rates compared with other schemes. Furthermore, the splitter blade scheme with an appropriate trailing edge position has the lowest average turbulence intensity and optimal relative velocity distribution in main flow passage component. Therefore, this paper proposes a reference scheme of the trailing edge position of the splitter blade to effectively decrease predominate pressure pulsation amplitude.

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