Search results for "Flow velocity"
showing 10 items of 227 documents
Rill flow resistance law under equilibrium bed‐load transport conditions
2019
In this paper, a recently deduced flow resistance equation for open channel flow was tested under equilibrium bed-load transport conditions in a rill. First, the flow resistance equation was deduced applying dimensional analysis and the incomplete self-similarity condition for the flow velocity distribution. Then, the following steps were carried out for developing the analysis: (a) a relationship (Equation) between the Γ function of the velocity profile, the rill slope, and the Froude number was calibrated by the available measurements by Jiang et al.; (b) a relationship (Equation) between the Γ function, the rill slope, the Shields number, and the Froude number was calibrated by the same …
Velocity Distribution and Dip Phenomenon in a Large Amplitude Meandering Channel
2020
The prediction of the velocity-dip, whereby the location of the maximum velocity occurs below the water surface, could be important for defining the flow pattern and the momentum transport processes. This study explores the dip-phenomenon in a high-curvature meandering bend. With the aid of data collected in a laboratory flume, the influence of the distance to the outer bank, the channel's curvature and the aspect ratio on the formation and position of the velocity-dip is investigated. Results show that, for the aspect ratios examined, a dip forms in the velocity profiles and its position varies along the bend as a function of the channel's curvature and the aspect ratio. Based on the measu…
Bio-predictive tablet disintegration: Effect of water diffusivity, fluid flow, food composition and test conditions
2013
Abstract Food intake may delay tablet disintegration. Current in vitro methods have little predictive potential to account for such effects. The effect of a variety of factors on the disintegration of immediate release tablets in the gastrointestinal tract has been identified. They include viscosity of the media, precipitation of food constituents on the surface of the tablet and reduction of water diffusivity in the media as well as changes in the hydrodynamics in the surrounding media of the solid dosage form. In order to improve the predictability of food affecting the disintegration of a dosage form, tablet disintegration in various types of a liquefied meal has been studied under stati…
Constraining lithospheric flow.
2016
The motion of Earth's tectonic plates—the lithosphere—is driven by the subduction of relatively cold and dense oceanic plates into the mantle. The resulting forces drive the motions of continental plates, but the manner in which this happens depends on the effective viscosities of the lithosphere and mantle. On page 1515 of this issue, Liu and Hasterok ( 1 ) discuss a novel method of constraining viscosities of the lithosphere from geophysical data.
CK-BB as indicator of prenatal brain-cell injury in fetuses with absent or reverse end-diastolic flow velocities of the umbilical arteries
1994
The purpose of this study is to determine the levels of brain type isoenzyme of creatine kinase (CK-BB) as a possible indicator of a pre-existing intrauterine brain-cell damage in cord blood sera of fetuses with preceding absent or reverse end-diastolic flow velocities of the umbilical arteries (AREDFV). CK-BB isoenzyme activities were determined in umbilical cord sera of 13 newborn infants with preceding AREDFV and in 14 fetuses with low end-diastolic flow velocities (LEDFV) of the umbilical arteries. 50 newborn infants with elective cesarean section and normal umbilical artery blood flow velocity waveforms were used as controls. Two-tailed Student's t-test and Fischer's exact test were us…
Reduction of scouring downstream of a rigid bed by means of a vegetated carpet: experimental investigation in a laboratory flume
2016
Vegetation is a critical component of aquatic ecosystems and exerts an important role in river morphodynamics. This paper describes the results of laboratory study carried out to investigate the role of vegetation on flow field and erosion process developing in non-equilibrium situations. Particular attention is paid to scour evolving downstream of a rigid bed and to the effect of a vegetated carpet used as a protective measure against scouring. The reported experimental study shows that the introduction of the vegetated carpet results in a more favourable configuration than in its absence determining reduced values of flow velocity, turbulence intensity and bed shear stress, and modifying …
Effect of Vegetation on Fluvial Erosion Processes: Experimental Analysis in a Laboratory Flume
2013
Abstract The plane evolution of a meander wave is determined by the erosion processes at the banks. Particularly, the outer- bank is considerably vulnerable to the erosion processes. Indirect techniques, which act upon the reduction of the effect of the cross-circulation motion, have been recently proposed to limit the outer-bank erosion. This paper shows preliminary results on the role played by vegetation on cross-circulation motion. The analysis is conducted on the basis of experimental data collected in a large amplitude meandering channel constructed at the hydraulic laboratory of DICAM. Maps describing the cross-stream flow, both over the no-vegetated bed and over the vegetated bed, a…
Flow Velocity Measurements in Vegetated Channels
2002
Understanding of the hydraulics of flow over vegetation is very important to support the management of fluvial processes. In this paper the flow over flexible bottom vegetation is experimentally studied. A two-dimensional-acoustic doppler velocimeter is used to measure the local flow velocities for different vegetation concentrations, discharges, and flume slopes. The influence of vegetation concentration and the depth/vegetation height ratio on the measured velocity profiles is analyzed. All measured velocity distributions are S-shaped and exhibit a three-zone profile. The relationship between the velocity distribution and the turbulence intensity distribution is also analyzed. The charact…
Field investigation of rill and ephemeral gully erosion in the Sparacia experimental area, South Italy
2013
Abstract This paper reports the results of a field investigation aiming at characterizing the morphology and hydraulics of both rills and ephemeral gullies (EGs) monitored at Sparacia experimental area, Sicily, Italy. The comparison between rill and interrill erosion measurements showed that sediment delivery processes occurred in some erosive events and that the rill erosion rate was dominant in many cases. The measurements were used for testing both the empirical relationships between the channel (rill, EGs and gully) length and its eroded volume and among the morphological variables (length, width, depth and volume) describing the channelized process. Finally, the rill and EGs hydraulic …
Laser Doppler flowmetry in subepidermal tumours and in normal skin of rats during localized ultrasound hyperthermia.
1988
Laser Doppler flowmetry has been applied to normal skin and to subepidermal tumours during localized ultrasound hyperthermia in the rat. In normal skin, 40 degrees C hyperthermia only induced a marginal increase in the red blood cell flux. Significant increases occurred after 20 min at 42 degrees C and after 4 min at 44 degrees C. During 44 degrees C hyperthermia maximum fluxes were reached after 24 min. Thereafter, the flow declined and finally approached preheating values. In contrast, in subepidermal tumours 40 degrees C hyperthermia on the average induced a slight decrease of the flux. During 42 degrees C hyperthermia a significant flow decrease was found after 40 min of heating. Follow…