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Flow Components (flow + component)
Selected AbstractsReversal Blood Flow Component as Determinant of the Arterial Functional Capability: Theoretical Implications in Physiological and Therapeutic ConditionsARTIFICIAL ORGANS, Issue 3 2009Daniel Bia Abstract In several physiological, pathological, and therapeutic circumstances, the arterial blood flow is acutely modified, increasing, in some vascular segments the reversal (SSR) and oscillatory (SSO) components of the shear stress. Recently, in an in vivo model we found a relationship between acute changes in SSR and SSO, and variations in the arterial viscoelasticity. As the arterial viscoelasticity and diameter are the main determinants of the arterial buffering (BF) and conduit (CF) functions, changes in those functions could be expected associated with variations in SSR and SSO. The aim was to analyze the association between acute increases in SSR and SSO, and changes in the aortic CF and BF. Aortic flow, pressure, and diameter were measured in 16 sheep under basal and high reversal and oscillatory flow conditions (high SSR and SSO). Aortic BF and CF were quantified, and their potential association with the SSR and SSO components were analyzed. During high reversal flow rate conditions, a smooth muscle contraction-pattern was evidenced, with an increase in BF and a decrease in CF. Changes in BF and CF were associated with the changes in SSR and SSO. The acute effects on the arterial wall biomechanics of variations in SSR and SSO could contribute to comprehend their chronic effects, and the meaning of the acute vascular effects of changes in SSR and SSO would depend on the situation. Increases in SSR and SSO could be associated with smooth muscle tone increase-dependent changes in arterial BF and CF. [source] Heat transportation by oscillatory flow with steady flow componentHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2006Akira Inukai Abstract This paper deals with heat transportation by an oscillatory flow composed of a sinusoidal oscillatory flow superimposed with a steady flow. Velocity and temperature fields, heat transportation rate, work rate, and heat transportation efficiency were investigated through numerical analysis. Results obtained elucidated that (1) the phase difference between velocity and temperature variation remained the same as that of the sinusoidal reciprocal flow without the use of a steady flow component. (2) In the upstream direction heat was mainly transported by the steady flow component and in the downstream direction transportation was mainly performed by the oscillatory flow component. (3) The heat transportation rate of the present oscillatory flow composed of both steady and oscillatory flow components was less than the arithmetic sum of the rates produced by the steady flow and the sinusoidal oscillatory flow. (4) The heat transportation rate was increased immensely by superimposing the steady flow on the sinusoidal oscillatory flow. (5) Conversely, work done by the present oscillatory flow increased only slightly. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(7): 482,500, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20130 [source] Comparative assessment of two distributed watershed models with application to a small watershedHYDROLOGICAL PROCESSES, Issue 11 2006Latif Kalin Abstract Distributed watershed models are beneficial tools for the assessment of management practices on runoff and water-induced erosion. This paper evaluates, by application to an experimental watershed, two promising distributed watershed-scale sediment models in detail: the Kinematic Runoff and Erosion (KINEROS-2) model and the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model. The physics behind each model are to some extent similar, though they have different watershed conceptualizations. KINEROS-2 was calibrated using three rainfall events and validated over four separate rainfall events. Parameters estimated by this calibration process were adapted to GSSHA. With these parameters, GSSHA generated larger and retarded flow hydrographs. A 30% reduction in both plane and channel roughness in GSSHA along with the assumption of Green-Ampt conductivity KG-A = Ks, where Ks is the saturated conductivity, resulted in almost identical hydrographs. Sediment parameters not common in both models were calibrated independently of KINEROS-2. A comparative discussion of simulation results is presented. Even though GSSHA's flow component slightly overperformed KINEROS-2, the latter outperformed GSSHA in simulations for sediment transport. In spite of the fact that KINEROS-2 is not geared toward continuous-time simulations, simulations performed with both models over a 1 month period generated comparable results. Copyright © 2006 John Wiley & Sons, Ltd. [source] X-ray colour maps of the cores of galaxy clustersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2000J. S. Sanders We present an analysis of X-ray colour maps of the cores of clusters of galaxies, formed from the ratios of counts in different X-ray bands. Our technique groups pixels lying between contours in an adaptively smoothed image of a cluster. We select the contour levels to minimize the uncertainties in the colour ratios, whilst preserving the structure of the object. We extend the work of Allen & Fabian by investigating the spatial distributions of cooling gas and absorbing material in cluster cores. Their sample is almost doubled: we analyse archive ROSAT Position Sensitive Proportional Counter (PSPC) data for 33 clusters from the sample of the 55 brightest X-ray clusters in the sky. Many of our clusters contain strong cooling flows. We present colour maps of a sample of the clusters, in addition to adaptively smoothed images in different bands. Most of the cooling flow clusters display little substructure, unlike several of the non-cooling-flow clusters. We fitted an isothermal plasma model with galactic absorption and constant metallicity to the mid-over-high energy colours in our clusters. Those clusters with known strong cooling flows have inner contours which fit a significantly lower temperature than the outer contours. Clusters in the sample without strong cooling flows show no significant temperature variation. The inclusion of a metallicity gradient alone was not sufficient to explain the observations. A cooling flow component plus a constant temperature phase did account for the colour profiles in clusters with known strong cooling flow components. We also had to increase the levels of absorbing material to fit the low-over-high colours at the cluster centres. Our results provide more evidence that cooling flows accumulate absorbing material. No evidence for increased absorption was found for the non-cooling-flow clusters. [source] Föhn as a response to changing upstream and downstream air massesTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 635 2008Georg J. Mayr Abstract Observations of föhn from the field phase of the Mesoscale Alpine Programme (MAP) are used to study how differences between the air masses upstream and downstream of the central Alpine crest determine whether the flow can descend to the lee as either shallow föhn, when it passes through passes in the mountains, or deep föhn, when it overflows the Alpine crest. First, the föhn case of 30 October 1999 is examined using ECMWF analyses and radiosonde data at various upstream and downstream locations. Additional measurements from aircraft, dropsondes, an instrumented car and automatic weather stations are then used for a detailed study of the föhn flow across the Brenner Pass. Advection of cold air around the eastern edges of the Alps and warm air around the western edge of the Alps ahead of a synoptic ridge set up a reservoir of colder air on the south side of the Alps and a reservoir of warmer air to the north. The depth to where the air was colder on the southern side was sufficient for a shallow föhn to flow through the pass. After the passage of the ridge axis, synoptic cold air advection provided another source of colder air, this time from the southwest, growing deeper with time and having a synoptically imposed cross-barrier flow component. The maximum depth to where the air upstream was colder than downstream extended just above the peaks of the highest mountains. An analysis of the detailed measurements across the Brenner Pass showed that this depth was also the top of the layer that descended and accelerated down the lee slopes of the Wipp Valley. Upstream, air above the föhn layer had an even stronger cross-barrier component yet did not descend because it did not have lower potential temperatures than the downstream side at that level. Deep föhn never developed. An examination of other well-documented MAP föhn cases confirmed the conclusion from the 30 October event that shallow and deep föhns , at least for the central Alps , are mostly a response to differences in air masses between the upstream and downstream side. A cross-barrier component of the flow was only a modification but in itself not sufficient to cause the flow to both descend and accelerate down the lee slope, unless potential temperatures on the upstream side were lower in this layer than on the downstream side. Copyright © 2008 Royal Meteorological Society [source] Measurements of Directional Flow Using a Directional Langmuir Probe in Weakly Magnetized PlasmasCONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2006T. Shikama Abstract Measurement of flow directed with respect to the magnetic field is performed using a directional Langmuir probe (DLP). A previously proposed practical formula for measurement of the Mach number under a weakly magnetized condition is modified for application to the directional flow field which consists of parallel and azimuthal flow components. The effect of density gradient caused by the rotational DLP measurement in the measurement of the radial profile of ion current angular distribution is modified. For the verification of the DLP measurement, parallel flow velocity is measured from the Doppler shift of HeII emission, while azimuthal flow velocity is calculated from E × B and diamagnetic drifts. It is revealed that this method provides plausible Mach numbers in the parallel and azimuthal directions with inclusion of the effect of density gradient. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Determining friction coefficients for interrill flows: the significance of flow filaments and backwater effectsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2003Dr David L. Dunkerley Abstract Friction coefficients in overland flows are customarily estimated from mean flow properties (depth, velocity, slope) that subsume spatial variations in flow arising from two major causes: microtopography and obstacles. This paper uses laboratory experiments in shallow flumes to examine the extent of non-uniformity in flow conditions associated with each cause. Randomly placed emergent obstacles in a flume with a shallow axial channel generally yielded higher hydraulic roughness than the same pattern of obstacles on a planar flume, as well as greater variation in roughness as the obstacle locations were altered. In both flumes, hydraulic roughness fell with increasing Reynolds number for 10% obstacle cover, showed a flattening trend at 20% cover, and exhibited a convex-downward trend at 30% obstacle cover. These results indicate the progressive onset of flow controls at narrow gaps in the obstacle field. In such flows, the use of mean flow properties conceals the existence of two main subdivisions of flow: flow filaments and backwater flows. In the experiments, flow filaments involved velocities more than twice the overall mean, whereas backwater flows were much slower than the mean. The existence of fast-moving flow filaments may be significant in understanding soil transport in surface runoff, and backwater depths may modify splash detachment. Similarly, friction coefficients that fail to reflect these important non-uniform flow components may not be optimal for hydraulic calculations or in erosion models. It is concluded that new approaches to observing and processing flow data may be required, in order to avoid the loss of important flow detail that is entailed in assuming uniform flow conditions. Copyright © 2003 John Wiley & Sons, Ltd. [source] Heat transportation by oscillatory flow with steady flow componentHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2006Akira Inukai Abstract This paper deals with heat transportation by an oscillatory flow composed of a sinusoidal oscillatory flow superimposed with a steady flow. Velocity and temperature fields, heat transportation rate, work rate, and heat transportation efficiency were investigated through numerical analysis. Results obtained elucidated that (1) the phase difference between velocity and temperature variation remained the same as that of the sinusoidal reciprocal flow without the use of a steady flow component. (2) In the upstream direction heat was mainly transported by the steady flow component and in the downstream direction transportation was mainly performed by the oscillatory flow component. (3) The heat transportation rate of the present oscillatory flow composed of both steady and oscillatory flow components was less than the arithmetic sum of the rates produced by the steady flow and the sinusoidal oscillatory flow. (4) The heat transportation rate was increased immensely by superimposing the steady flow on the sinusoidal oscillatory flow. (5) Conversely, work done by the present oscillatory flow increased only slightly. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(7): 482,500, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20130 [source] Parameter estimation in semi-distributed hydrological catchment modelling using a multi-criteria objective functionHYDROLOGICAL PROCESSES, Issue 22 2007Hamed Rouhani Abstract Output generated by hydrologic simulation models is traditionally calibrated and validated using split-samples of observed time series of total water flow, measured at the drainage outlet of the river basin. Although this approach might yield an optimal set of model parameters, capable of reproducing the total flow, it has been observed that the flow components making up the total flow are often poorly reproduced. Previous research suggests that notwithstanding the underlying physical processes are often poorly mimicked through calibration of a set of parameters hydrologic models most of the time acceptably estimates the total flow. The objective of this study was to calibrate and validate a computer-based hydrologic model with respect to the total and slow flow. The quick flow component used in this study was taken as the difference between the total and slow flow. Model calibrations were pursued on the basis of comparing the simulated output with the observed total and slow flow using qualitative (graphical) assessments and quantitative (statistical) indicators. The study was conducted using the Soil and Water Assessment Tool (SWAT) model and a 10-year historical record (1986,1995) of the daily flow components of the Grote Nete River basin (Belgium). The data of the period 1986,1989 were used for model calibration and data of the period 1990,1995 for model validation. The predicted daily average total flow matched the observed values with a Nash,Sutcliff coefficient of 0·67 during calibration and 0·66 during validation. The Nash,Sutcliff coefficient for slow flow was 0·72 during calibration and 0·61 during validation. Analysis of high and low flows indicated that the model is unbiased. A sensitivity analysis revealed that for the modelling of the daily total flow, accurate estimation of all 10 calibration parameters in the SWAT model is justified, while for the slow flow processes only 4 out of the set of 10 parameters were identified as most sensitive. Copyright © 2007 John Wiley & Sons, Ltd. [source] Estimation of irrigation flow by hydrograph analysis in a complex agricultural catchment in subtropical ChinaHYDROLOGICAL PROCESSES, Issue 10 2007Jia-Liang Tang Abstract Estimating the amount of irrigation water is challenging at the catchment scale because of the difficulties in direct measurement and interactions between the flow components. The objectives of the study were to characterize the catchment flows in an agricultural catchment with an irrigation system in subtropical China and to estimate catchment irrigation flow using hydrograph analysis methods. A weighting model and multiple regression models were established to estimate catchment irrigation outflow according to the hydrographs of the inflows and outflows of the catchment. The multiple regression models took into consideration the drainage time of base flow, resulting in better estimation on an event and annual basis. Using the MR-6d method, the estimated irrigation outflows amounted to 3700 mm, 2600 mm and 2760 mm during 2001, 2002 and 2003 respectively, which covered 70%, 60% and 64% respectively of the total catchment outflows in the corresponding years. Copyright © 2007 John Wiley & Sons, Ltd. [source] Investigating mechanisms of stormflow generation by natural tracers and hydrometric data: a small catchment study in the Black Forest, GermanyHYDROLOGICAL PROCESSES, Issue 2 2001E. Hangen Abstract The importance and interaction of various hydrological pathways and identification of runoff source areas involved in solute transport are still under considerable debate in catchment hydrology. To reveal stormflow generating areas and flow paths, hydrometric behaviour of throughfall, soil water from various depths, runoff, and respective concentrations of the environmental tracers 18O, Si, K, SO4 and dissolved organic carbon were monitored for a 14-week period in a steep headwater catchment in the Black Forest Mountains, Germany. Two stormflow hydrographs were selected and, based on 18O and Si, chemically separated into three flow components. Their sources were defined using mixing diagrams. Additional information about stormflow generating mechanisms was derived from recession analyses of the basin's complete 5-year hydrograph record. By providing insight into storage properties and residence times of outflowing reservoirs of the basin, recession analysis proved to be a valuable tool in runoff model conceptualization. Its results agreed well with hydrometric and hydrochemical data. Supported by evaluation of 30 hillslope soil profiles a coherent concept of stormflow generation could be derived: whereas in many steeply sloped basins in the temperate region soil water from hillslopes appears to have an immediate effect on the shape of the stormflow hydrograph, its role at this basin is basically restricted to the recharge of the groundwater reservoir in the near-channel area. Storm hydrograph peaks appear to be derived from a small direct runoff component supplemented by a fast delivery of baseflow from the groundwater reservoir in the valley bottom. Copyright © 2001 John Wiley & Sons, Ltd. [source] Divergent effects of ephedrine and phenylephrine on cardiovascular hemodynamics of near-term fetal sheep exposed to hypoxemia and maternal hypotensionACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2007T. Erkinaro Background:, We hypothesized that the administration of ephedrine and phenylephrine for maternal hypotension modifies cardiovascular hemodynamics in near-term sheep fetuses. Methods:, At 115,136 days of gestation, chronically instrumented, anesthetized ewes with either normal placental function or increased placental vascular resistance after placental embolization were randomized to receive boluses of ephedrine (n = 12) or phenylephrine (n = 12) for epidural-induced hypotension after a short period of hypoxemia. Fetal cardiovascular hemodynamics were assessed by Doppler ultrasonography at baseline, during hypotension and after vasopressor treatment. Results:, During hypotension, fetal PO2 decreased and proximal branch pulmonary arterial and pulmonary venous vascular impedances increased. Additionally, in the embolized fetuses, the time-velocity integral ratio between the antegrade and retrograde blood flow components of the aortic isthmus decreased. These parameters were restored to baseline conditions by ephedrine but not by phenylephrine. With phenylephrine, weight-indexed left ventricular cardiac output and ejection force decreased in the non-embolized fetuses, and the proportion of isovolumetric contraction time of the total cardiac cycle was elevated in the embolized fetuses. Conclusions:, After exposure to hypoxemia and maternal hypotension, ephedrine restored all fetal cardiovascular hemodynamic parameters to baseline. Phenylephrine did not reverse fetal pulmonary vasoconstriction or the relative decrease in the net forward flow through the aortic isthmus observed in fetuses with increased placental vascular resistance. Moreover, fetal left ventricular function was impaired during phenylephrine administration. [source] STREAMFLOW DEPLETION: MODELING OF REDUCED BASEFLOW ANI INDUCED STREAM INFILTRATION FROM SEASONALLY PUMPED WELLS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2001Xunhong Chen ABSTRACT: Numerical modeling techniques are used to analyze streamflow depletion for stream-aquifer systems with baseflow. The analyses calculated two flow components generated by a pumping well located at a given distance from a river that is hydraulically connected to an unconfined aquifer. The two components are induced stream infiltration and reduced baseflow; both contribute to total streamflow depletion. Simulation results suggest that the induced infiltration, the volume of water discharged from the stream to the aquifer, has a shorter term impact on streamflow, while the reduced baseflow curves show a longer term effect. The peak impacts of the two hydrologic processes on streamflow occur separately. The separate analysis helps in understanding the hydrologic interactions between stream and aquifer. Practically, it provides useful information about contaminant transport from stream to aquifer when water quality is a concern, and for areas where water quantity is an issue, the separate analysis offers additional information to the development of water resource management plan. [source] X-ray colour maps of the cores of galaxy clustersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2000J. S. Sanders We present an analysis of X-ray colour maps of the cores of clusters of galaxies, formed from the ratios of counts in different X-ray bands. Our technique groups pixels lying between contours in an adaptively smoothed image of a cluster. We select the contour levels to minimize the uncertainties in the colour ratios, whilst preserving the structure of the object. We extend the work of Allen & Fabian by investigating the spatial distributions of cooling gas and absorbing material in cluster cores. Their sample is almost doubled: we analyse archive ROSAT Position Sensitive Proportional Counter (PSPC) data for 33 clusters from the sample of the 55 brightest X-ray clusters in the sky. Many of our clusters contain strong cooling flows. We present colour maps of a sample of the clusters, in addition to adaptively smoothed images in different bands. Most of the cooling flow clusters display little substructure, unlike several of the non-cooling-flow clusters. We fitted an isothermal plasma model with galactic absorption and constant metallicity to the mid-over-high energy colours in our clusters. Those clusters with known strong cooling flows have inner contours which fit a significantly lower temperature than the outer contours. Clusters in the sample without strong cooling flows show no significant temperature variation. The inclusion of a metallicity gradient alone was not sufficient to explain the observations. A cooling flow component plus a constant temperature phase did account for the colour profiles in clusters with known strong cooling flow components. We also had to increase the levels of absorbing material to fit the low-over-high colours at the cluster centres. Our results provide more evidence that cooling flows accumulate absorbing material. No evidence for increased absorption was found for the non-cooling-flow clusters. [source] Forced Alveolar Flows and Mixing in the LungPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009David Borer The air flows deep inside the lung are not only important in gas exchange processes but they also determine the efficiency of particle deposition and retention. The study aims at quantifying the relative influence of different flow components in the transport of small particles in alveolar geometries such as convective breathing patterns, wall movement, gravitational settling and Brownian motion. In addition, the possibility and efficiency of external forcing is studied, relying on the mechanism of internal acoustic streaming. A viscous oscillating boundary layer flow is converted into a steady, viscosity-independent bulk motion which is very efficient at low Reynolds numbers. The streaming can be controlled by external parameters (excitation amplitude, frequency, beam shape) and may thus be of diagnostic and therapeutic relevance. Numerical simulations are performed to analyze the flow patterns in 3D model geometries and to measure deposition rates. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Value-added maps: fluid-dynamics descriptors from ring diagramsASTRONOMISCHE NACHRICHTEN, Issue 3-4 2007R. W. Komm Abstract We describe fluid-dynamics descriptors derived from maps of the horizontal flow components measured with ring-diagram analysis. Here, we focus on quantities, such as vorticity and kinetic helicity density, and discuss three examples of results derived from them: subsurface flows associated with active regions, subsurface flows and flare activity, and large-scale behavior of horizontal flows. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||