The Effect of Magnetic and Hydrodynamic Control on the Susceptibility Anisotropy of Redeposited Silt
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Results are described of susceptibility anisotropy measurements made on natural medium to coarse silt that has been redeposited from flowing water in a laboratory flume. It is shown that the orientation of the axis of maximum susceptibility is controlled principally by the shear produced by the current flow tangential to the surface of the deposit. For sediment within this size range, the aligning effect of the earth's magnetic field on the magnetization induced in the particles is only apparent at the smaller values of applied fluid stress.Keywords:
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long throat flume is recommended nowadays to use in flow rate measurement in irrigation areas for its several advantages over other types of flumes known: ① with a simple flow rate table determined on the flume dimensions, errors of measurement results can be controlled to be less than 5%; ② water head loss over the flume is minimal; ③ this type of flume is suitable nearly to any kinds of channel and is nearly free from floating debris effects.
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Bole is a major area with loess sediments in Xinjiang Province.On the basis of a 11 m loess section from bole,a series of indices consisting of magnetic susceptibility,grain size,TOC and CaCO3 in the laboratory.And the results show that the average value of the magnetic susceptibility is far below than that of typical loess on loess plateau,the changing process is also different from that of the typical loess on loess plateau.Coarse silt(63-10 μm) is the dominant component of the section,and there are only a small amount of clay(5 μm),silt(63 μm) and fine silt(5-10 μm) in the section.There is a negative correlation between clay,fine silt and magnetic susceptibility.Clay and fine silt contain little magnetic minerals,so their impacts on magnetic susceptibility is limit,while the contribution of sand is relatively large;The section carries a small quantity of TOC,so TOC makes only a small contribution for magnetic susceptibility;The correlation between magnetic susceptibility and CaCO3 is weak.Thus,the factors influencing magnetic susceptibility in this area are very complex.More climatic indicators in combination with magnetic susceptibility are needed to restore the ancient climate and paleo-environment of the area.And then we can carry out multi-index analysis and synthesis to get more reliable and accurate explanations.
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Loess plateau
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When we compared the stroke frequency with the gradual increase of swimming speed,we found that the stroke frequency is significantly slower in the flume than in the swimming pool at 1.28、1.32 and 1.36m/s in the breaststroke and 1.90m/s in the freestyle.However,in the speed which is slower than 1.28m/s in the breaststroke and 1.90 in the freestyle,we found that there is no significant statistic difference in the stroke frequency between the flume swimming and pool swimming.With the same speed,there is no significant difference in the blood lactate after swimming,but the maximum heart stroke is significantly slower after the flume swimming as oppose to the pool swimming.It is our speculation that the swimmers could control the technique better in the flume because they had the reference in the flume when they swam,and consequently,retained a relatively more completed and effective technique and lower stroke frequency at a relatively higher speed.Lower heart stroke after flume swimming is also supportive to the view of improvement of technique efficiency after flume swimming.
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Stroke
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The purpose of this study was to discuss the effects in technical disciplinarian of free- style swimmers in flume and swimming pool,and compare the difference in two experiment conditions.After 23 swimmers were adapted to train in flume,enactment intensity to test in flume and swimming pool,and get theirs technical parameter.The result shows that the aver- age SR of freestyle swimmers in swimming pool higher than in flume,yet the average SL of the swimmers in swimming pool lower than in flume,and two technical parameters have no signifi- cant difference,but their difference get evident alone with speed increasing.EI has no signifi- cant difference,as the whole technical parameter in flume is higher than in swimming pool.The time of grab water of freestyle swimmer in flume is more-higher than in swimming pool,yet the time of hold water and push water have no difference in flume and swimming pool,the time of empty out water in flume is more-lower than in swimming pool.The conclusion is that free- style swimmers have no obvious difference in SR,SL and ST,so two conditions have no promi- nence difference.
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A group of Cutthroat flumes was rated under both free flow and submerged flow conditions. Generalized discharge rating curves can be developed due to the simplicity of the structure and the geometric similarity between flume sizes. Twelve flumes were used in this study, including three flume lengths of 1.5 ft (0.45 m), 3 ft (0.90 m), and 4.5 ft (1.35 m), with four different throat widths for each length. In addition, the flume sizes were selected so as to permit correlation with the initial Cutthroat flume studies, wherein a flume length of 9 ft. (2.7 m), and throat widths varying from 1 ft (0.3 m) to 6 ft (1.8 m), were studied.
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Wave flume
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The effects of longitudinal slope on the estimation of discharge in a 0.762-meter (m) (depth at flume entrance) H flume were tested under controlled conditions with slopes from −8 to +8 percent and discharges from 1.2 to 323 liters per second. Compared to the stage-discharge rating for a longitudinal flume slope of zero, computed discharges were negatively biased (maximum −31 percent) when the flume was sloped downward from the front (entrance) to the back (exit), and positively biased (maximum 44 percent) when the flume was sloped upward. Biases increased with greater flume slopes and with lower discharges. A linear empirical relation was developed to compute a corrected reference stage for a 0.762-m H flume using measured stage and flume slope. The reference stage was then used to determine a corrected discharge from the stage-discharge rating. A dimensionally homogeneous correction equation also was developed, which could theoretically be used for all standard H-flume sizes. Use of the corrected discharge computation method for a sloped H flume was determined to have errors ranging from −2.2 to 4.6 percent compared to the H-flume measured discharge at a level position. These results emphasize the importance of the measurement of and the correction for flume slope during an edge-of-field study if the most accurate discharge estimates are desired.
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Possessing such following characteristics as high measuring accuracy,simple design,strong water-passing capacity and low backwater in the upper stream,the cutthroat measuring flume is the best measuring structure applied in the irrigation district.At present,it is used to measure the discharge in some irrigation districts.However,through the investigation,we can't find the standard calculation formula for the cutthroat flume and the impact of outflow on flows in all situations has not been made clear.Under the conditions of free outflow and submerged outflow,this paper theoretically derives the formula of flow calculation and presents the revised formula.
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Outflow
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Abstract. Cutthroat flumes are widely used in field projects to estimate discharge via a stage-discharge relationship. Flumes are commonly tested and calibrated in a laboratory to develop the stage-discharge relationship, but field installations often occur under non-idealized conditions, specifically with respect to bed slope. We calibrated a cutthroat flume with dimensions of 0.91 m length and 0.35 m throat width for bed slopes ranging from 0% to 2% to represent a range of field conditions. The experiment was conducted in the Water Resources Lab of the College of Engineering at the University of Wyoming, which provided highly accurate discharge measurements. Results showed negligible impact of slope on the resulting stage-discharge relationship under free flow conditions. We were able to generate a composite rating curve for bed slopes ranging from 0% to 2% for flumes of this size. Our study indicates that, under free flow conditions, longitudinal floor slopes ranging from 0% to 2% do not significantly affect the cutthroat flume rating curve . Keywords: Cutthroat flume, Flume calibration, Free flow, Rating curve, Stream discharge.
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A study was conducted to revise the procedure for adjusting discharge measurements in a cutthroat flume subjected to settlement in free-flowing conditions. A series of 57 tests was performed on six different size cutthroat flumes. Each flume was systematically adjusted to simulate settlement in both the lateral and the longitudinal directions. Discharge inaccuracies were then recorded for each settlement condition. The test results were combined with the results of three cutthroat flumes previously reported. The coefficients describing the flume geometry, Cdlat and Cdlong, were determined to be significantly different than previously indicated. New expressions for Cdlat and Cdlong were formulated for inclusion into the previously reported discharge measurement adjustment procedure.
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Settlement (finance)
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Distributions of bed shear stress across the width of a rotating circular flume with smooth and rough bed surfaces were obtained by measurement and model prediction. Results with flows over smooth beds showed that the flow in the central part may be considered to be two-dimensional and that effects of flow depth over the operating range of the flume are minor for flow depths not exceeding 0.14 m. For rough beds, the bed shear stress distributions were found to be skewed toward the inner wall. This can be corrected if a compensating roughness is added to the bottom of the ring. Such measures are also effective for flumes with smooth beds. Measured bed shear stress distributions agreed well with the predicted distributions for smooth beds and reasonably well for rough beds. The modified Preston tube, for measurement of bed shear stress in flows over rough beds, was found to give promising results. Further tests are required to completely define the uncertainty in bed shear stress measurements made with this instrument.
Flume
Hydraulic roughness
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