Direct Flow Measurements Research Articles

Flows in the Tasman Front south of Norfolk Island

The Tasman Front is a narrow band of eastward flowing subtropical water crossing the Tasman Sea from Australia to North Cape, New Zealand. It is the link between the two subtropical western boundary currents of the South Pacific, the East Australian Current (EAC) off eastern Australia, and the East Auckland Current (EAUC) off northeastern New Zealand. Here we report the first direct measurements of flow in the Tasman Front from a moored array deployed across gaps in the submarine ridges south of Norfolk Island and hydrographic and ADCP measurements during the deployment and recovery voyages. The mean flow through the array over July 2003 to August 2004 was found to be eastward only in the upper 800 m with a transport of ∼6 Sv. Below 800 m a weak westward mean flow (∼1.5 Sv) was measured, associated with Antarctic Intermediate Water (AAIW). Using sea surface height to account for additional transport south of the moored array results in a total mean eastward transport between Norfolk Island and North Cape, New Zealand of ∼8 Sv, varying between −4 and 18 Sv. The measurements show that the Tasman Front is much shallower than either the EAC or EAUC, both of which extend below 2000 m depth, has less transport than either the EAC or EAUC and has instances of flow reversal. Thus, the Tasman Front is a weaker connection between the EAC and EAUC than the paradigm of a contiguous South Pacific western boundary current system would suggest.

Abstract 186: Use of Optical Coherence Tomography to Study Arteriogenesis After Hind-Limb Ischemia

Introduction: Because of their small size, direct measurement of collateral artery flow and diameter is difficult, so laser Doppler perfusion is used as a surrogate with micro-computerized tomography (microCT) performed to assess collateral networks and diameters after sacrifice. We applied optical coherence tomography (OCT) to measure artery diameter, flow, and velocity serially after hindlimb ischemia. Hypothesis: OCT is superior to microCT for measuring arteriogenesis. Methods: OCT was performed on the hindlimb musculature of male C57BL/6 mice, ages 3-5 months (n=5) bilaterally prior to unilateral femoral artery ligation, immediately after, and weekly for four weeks. Femoral artery and collateral artery diameter, flow, and axial velocity were measured. On postoperative day 28, mice were sacrificed by pressure perfusion fixation with formalin and injected with contrast. MicroCT was then performed at 18 micron resolution. Collateral artery diameter and vessel density from 3-d reconstructed datasets were analyzed using Matlab. Results: Figure 1 shows representative OCT (1A) and microCT (1B) images. Femoral artery flow and axial velocity decreased significantly after ligation (0.046 ± 0.040 from 2.1 ± 0.5 mm 3 /sec, p =0.006 and 1.1 ± 1.0 from 16.0 ± 1.1 mm/sec, p <0.001). The velocity of the ligated femoral was still significantly slower at 28 days (5.0 ± 1.9 vs 11.9 ± 1.0 mm/sec). Collateral artery flow reversed direction after ligation. At 28 days, the velocity in the collateral artery had increased significantly (12.4 ± 2.1 from 1.7 ± 1.0 mm/sec at baseline). MicroCT tended to overestimate the unligated collateral diameter (95 ± 9 vs 63 ± 8 microns by OCT, p =0.0537), but was accurate for the ligated side collaterals. Conclusions: Optical coherence tomography provides important physiologic and structural data regarding arteriogenesis following hindlimb ischemia and is superior to microCT for assessment of arteriogenesis.

Quantifying the morphology of flow patterns in landslide-affected and unaffected soils

Summary In mountainous regions, landslides are a common natural phenomenon. They are often triggered by a combination of steep relief and long lasting rainfalls. Therefore, hydrological conditions in the soil are crucial for their initiation. Because direct measurements of water flow are difficult and model predictions uncertain, we used a dye to visualise flow patterns directly. We combined dye tracer experiments with field observations (root density and rock fragment content) and measurements of soil properties (bulk density, soil water retention curve and saturated hydraulic conductivity). We quantified the morphology of flow patterns by image indices and mutual information that measures the overall dependency between variables and compared two shallow landslides of different ages with a landslide-unaffected hillslope. Our results showed that flow patterns on the landslides were more fragmented and contained larger stained objects than on the landslide-unaffected site. We relate these findings to a larger stone content and a stronger macropore–soil matrix interaction. Moreover, we detected a fissure network on the younger landslide that probably affects its hydrological behaviour. Field observations, soil hydraulic properties and dye tracer studies describe different hydrological aspects of the studied sites and complement the information provided by the morphological image indices.

Use of phase-contrast magnetic resonance angiography to measure adaptations of aortic and pulmonary artery flow during supine aerobic exercise

BackgroundCardiovascular adaptations to aerobic exercise are mediated through interactions of cardiac, hormonal, metabolic, and muscular mechanisms with a dominant role for increase in cardiac output to enhance oxygen delivery. However, increased demands for oxygen uptake and use during exercise depend on adequate adaptations of systemic and pulmonary vasculature. Assessment of exercise response is crucial in various cardiac and pulmonary diseases. Recent advances in MRI techniques allow for direct measurement of aortic and pulmonary blood flow with phase-contrast magnetic resonance angiography (PCMRA). We have studied aortic and pulmonary flow in healthy individuals to assess haemodynamic adaptations to exercise using PCMRA. MethodsNine adult healthy volunteers underwent PCMRA while doing heart-rate-targeted (180% of resting heart rate) aerobic supine leg exercise. Aortic flow was reassessed post exercise after 2 min rest. All flow variables were assessed by retrospective free-breathing pulse-gated PCMRA in the mid ascending aorta and main pulmonary artery (field of view [FOV] 320 mm, FOV phase 75%, base resolution 256, voxel 1·3 × 1·3 × 5·0 mm, TE 2·2 ms, TR 29·9 ms, slice thickness 5 mm, three averages, and 30 reconstructed phases, Venc 150 cm/s at rest, 300 cm/s during exercise). All images were assessed by three individuals trained in MRI flow evaluation and independently checked by an experienced cardiac radiologist. Flow sequence analysis was done with offline software (Argus, Siemens Medical Systems), by manually contouring the vessel of interest so that all flow was accounted for. Pulmonary and aortic blood flow was determined from the flow velocities in individual voxels in the region of interest. FindingsIncrease in heart rate during exercise (from a mean of 69 beats per min [SD 10] at rest to 120 [14] after exercise) resulted in increased cardiac output (mean 6·5 L/min [SD 1·4] to 12·4 [1·8]). All flow variables significantly increased with exercise compared with rest: aorta systolic peak velocity increased from mean 89 cm/s [SD 14] to 122 [34] (p=0·016); pulmonary artery systolic peak velocity 86 cm/s [18] to 140 [48] (p=0·007); aorta systolic peak flow rate 415 mL/s [83] to 550 [135] (p=0·002); and pulmonary artery systolic peak flow rate 410 mL/s [80] to 577 [180] (p=0·006). These variables showed a trend to normalisation at 2 min recovery. InterpretationUse of free-breathing pulse-gated PCMRA to measure aortic and pulmonary blood flow and velocity during exercise is feasible. Moderate aerobic exercise leads to a steep increase in blood flow and flow velocities in aorta and main pulmonary artery facilitating increased oxygen uptake. Exercise PCMRA could help in diagnosis, assessment of treatment response, and follow-up in many patient groups with pulmonary and cardiovascular disease. FundingBristol NIHR Cardiovascular Biomedical Research Unit, NIHR Academic Clinical Lectureship to GEP

Remote Gas Emission Flux Sensing in a Thermal Power Plant Using Shadow Image Processing

Total flue gas emission is a crucial quantity for control of environmental impact in thermal power plants. Direct gas flow measurements by Pitot tubes and other sensors are hampered by the very high temperature at the exhaust, high content of carbon soot and frequently turbulent flow conditions, which cause a non-parabolic flow profile across the exhaust cross section. We are developing an optical imaging method for gas flux measurements, using shadow video imaging of the dynamic hot gas emission profile at the power plant exhaust. All, high exhaust gas temperature, pressure increase and carbon soot content cause small variations of the refractive index. This deflects a considerable amount direct sunlight under inclined solar illumination conditions (at approx 38 deg inclination angle), and results in a rather sharp contrast and clear shadow image of the gas flow above the exhaust. This feature is not observable in direct transmission imaging. The distant flow shadow image pattern, as seen on the plant floor, is video monitored over a short time period and the dynamic image evolution digitally processed and analyzed. The presented method is similar to the well known optical so-called Schlieren imaging technique. Initial video processing algorithms and results are presented that provide the flue gas flow velocity directly at the exhaust exit, being close to the expected values, obtained from power plant process parameters.

Direct velocity measurement of a turbulent shear flow in a planar Couette cell

In a plane Couette cell a thin fluid layer consisting of water is sheared between the sides of a transparent band at Reynolds numbers ranging from 300 to 1400. The length of the cell's flow channel is large compared to the film separation. To extract the flow velocity in the experiments, a correlation image velocimetry method is used on pictures recorded with a high-speed camera. The flow is recorded at a resolution that allows us to analyze flow patterns similar in size to the film separation. The fluid flow is then studied by calculating flow velocity autocorrelation functions. The turbulent patterns that arise on this scale above a critical Reynolds number of Re=360 display characteristic patterns that are proven by use of the calculated velocity autocorrelation functions. The patterns are metastable and reappear at different positions and times throughout the experiments. Typically these patterns are turbulent rolls which are elongated in the stream direction, which is the direction in which the band is moving. Although the flow states are metastable they possess similarities to the steady Taylor vortices known to appear in circular Taylor Couette cells.

Performance of Variable Energy Cyclotron Centre superconducting cyclotron liquid nitrogen distribution system

The liquid nitrogen distribution at Variable Energy Cyclotron Centre, Kolkata, India K500 superconducting cyclotron uses parallel branches to cool the thermal shield of helium vessel housing the superconducting coil and the cryopanels. Liquid nitrogen is supplied to the thermal shields from a pressurised liquid nitrogen dewar. Direct measurement of flow is quite difficult and seldom used in an operational cryogenic system. The total flow and heat load of the liquid nitrogen system was estimated indirectly by continuous measurement of level in the liquid nitrogen tanks. A mathematical model was developed to evaluate liquid nitrogen flow in the parallel branches. The model was used to generate flow distribution for different settings and the total flow was compared with measured data.

Combined effects of diffuse phase transition and microstructure on the electrocaloric effect in Ba1−xSrxTiO3 ceramics

This paper demonstrates the combined effects of diffuse phase transition and microstructure on the electrocaloric effect (ECE) in Ba1−xSrxTiO3 (x = 0.2–0.4) ferroelectric ceramics. The ECE was characterized by direct heat flow measurement and an indirect thermodynamic method, which both provided consistent results. With increasing amount of Sr, the phase transition diffused and the grains grew larger. Since larger grains favor a high ΔTmax while a diffuse phase transition does not, the combination of these two effects induced nonmonotonic variation of the ECE. The x = 0.35 sample showed the best performance, with an ECE strength of 0.23 K·m/MV near room temperature.

Tidal breathing flow measurement in awake young children by using impedance pneumography

Characteristics of tidal breathing (TB) relate to lung function and may be assessed even in young children. Thus far, the accuracy of impedance pneumography (IP) in recording TB flows in young children with or without bronchial obstruction has not been evaluated. The aim of this study was to evaluate the agreement between IP and direct flow measurement with pneumotachograph (PNT) in assessing TB flow and flow-derived indices relating to airway obstruction in young children. Tidal flow was recorded for 1 min simultaneously with IP and PNT during different phases of a bronchial challenge test with methacholine in 21 wheezy children aged 3 to 7 years. The agreement of IP with PNT was found to be excellent in direct flow signal comparison, the mean deviation from linearity ranging from 2.4 to 3.1% of tidal peak inspiratory flow. Methacholine-induced bronchoconstriction or consecutive bronchodilation induced only minor changes in the agreement. Between IP and PNT, the obstruction-related tidal flow indices were equally repeatable, and agreement was found to be high, with intraclass correlation coefficients for T PTEF/T E, V PTEF/V E, and parameter S being 0.94, 0.91, and 0.68, respectively. Methacholine-induced changes in tidal flow indices showed significant associations with changes in mechanical impedance of the respiratory system assessed by the oscillometric technique, with the highest correlation found in V PTEF/V E (r = -0.54; P < 0.005 and r = -0.55; P < 0.005 by using IP or PNT, respectively). The results indicate that IP can be considered as a valid method for recording tidal airflow profiles in young children with wheezing disorders.

MEASUREMENT OF SAP FLOW DYNAMICS THROUGH THE TOMATO PEDUNCLE USING A NON-INVASIVE SENSOR BASED ON THE HEAT FIELD DEFORMATION METHOD

Recent contradicting evidence on the contributions of xylem and phloem to tomato fruit growth highlights the need for a more thorough insight into the dynamics of sap flow through the tomato peduncle. In fact, knowledge on sap flow dynamics through small plant parts remains scarce, due to a lack of direct measurements. Most currently available sap flow sensors use needles, making them inappropriate for the direct measurement of sap flow through small plant parts such as a tomato peduncle. Therefore, a non-invasive sap flow sensor based on the heat field deformation (HFD) principle was tested on the peduncle of a tomato truss. This mini HFD sensor, consisting of a heater element and three thermocouples stitched on insulation tape, was wrapped around the peduncle and allowed continuous monitoring of changes in the heat field around the heater caused by sap flow. Actual influx into the tomato truss was calculated based on fruit growth data and estimates of fruit transpiration and was compared with the dynamics measured with the mini HFD sensor. Additionally, heat girdling of the peduncle was performed to block phloem influx to study the dynamics of xylem and phloem influx using the mini HFD sensor. First results of the mini HFD sensor were promising and the measured sap flow dynamics through the tomato peduncle agreed well with the calculated sap influx. Results of the girdling experiment suggested opposite patterns of xylem and phloem influx, with a decreased xylem influx during the daytime. Furthermore, the pattern of xylem influx revealed a close relation with the total water potential in the stem. As such, the mini HFD sensor provided direct measurements of sap flow dynamics through a tomato peduncle and, hence, has a large potential to finally resolve the controversy on water influx into developing fruits.

A research of dynamic compensation of coriolis mass flowmeter based on BP neural networks

As a resonate sensor, Coriolis Mass Flowmeter (CMF) provides a direct measurement of mass flow and is widely used in flow measurement field. However, defect of dynamic characteristics has become the main factor which restricts its further application in batch filling processes. Based on theoretical analysis, a dynamic compensation system, BP (Back-Propagation) neural network dynamic compensation method is designed in order to solve this problem. Adding a neural network dynamic compensation segment after the sensor’s output, the method uses the gradient descent method with an additional momentum factor for neural network training. Studies have shown that this method greatly improves the dynamic characteristics of the Coriolis mass flowmeter.

Near-infrared spectroscopy versus magnetic resonance imaging to study brain perfusion in newborns with hypoxic–ischemic encephalopathy treated with hypothermia

BackgroundThe measurement of brain perfusion may provide valuable information for assessment and treatment of newborns with hypoxic–ischemic encephalopathy (HIE). While arterial spin labeled perfusion (ASL) magnetic resonance imaging (MRI) provides noninvasive and direct measurements of regional cerebral blood flow (CBF) values, it is logistically challenging to obtain. Near-infrared spectroscopy (NIRS) might be an alternative, as it permits noninvasive and continuous monitoring of cerebral hemodynamics and oxygenation at the bedside. ObjectiveThe purpose of this study is to determine the correlation between measurements of brain perfusion by NIRS and by MRI in term newborns with HIE treated with hypothermia. Design/methodsIn this prospective cohort study, ASL-MRI and NIRS performed during hypothermia were used to assess brain perfusion in these newborns. Regional cerebral blood flow (CBF) values, measured from 1–2 MRI scans for each patient, were compared to mixed venous saturation values (SctO2) recorded by NIRS just before and after each MRI. Analysis included groupings into moderate versus severe HIE based on their initial background pattern of amplitude-integrated electroencephalogram. ResultsTwelve concomitant recordings were obtained of seven neonates. Strong correlation was found between SctO2 and CBF in asphyxiated newborns with severe HIE (r=0.88; p value=0.0085). Moreover, newborns with severe HIE had lower CBF (likely lower oxygen supply) and extracted less oxygen (likely lower oxygen demand or utilization) when comparing SctO2 and CBF to those with moderate HIE. ConclusionsNIRS is an effective bedside tool to monitor and understand brain perfusion changes in term asphyxiated newborns, which in conjunction with precise measurements of CBF obtained by MRI at particular times, may help tailor neuroprotective strategies in term newborns with HIE.

Drought predisposes piñon–juniper woodlands to insect attacks and mortality

To test the hypothesis that drought predisposes trees to insect attacks, we quantified the effects of water availability on insect attacks, tree resistance mechanisms, and mortality of mature piñon pine (Pinus edulis) and one-seed juniper (Juniperus monosperma) using an experimental drought study in New Mexico, USA. The study had four replicated treatments (40 × 40 m plot/replicate): removal of 45% of ambient annual precipitation (H2 O-); irrigation to produce 125% of ambient annual precipitation (H2 O+); a drought control (C) to quantify the impact of the drought infrastructure; and ambient precipitation (A). Piñon began dying 1 yr after drought initiation, with higher mortality in the H2 O- treatment relative to other treatments. Beetles (bark/twig) were present in 92% of dead trees. Resin duct density and area were more strongly affected by treatments and more strongly associated with piñon mortality than direct measurements of resin flow. For juniper, treatments had no effect on insect resistance or attacks, but needle browning was highest in the H2 O- treatment. Our results provide strong evidence that ≥ 1 yr of severe drought predisposes piñon to insect attacks and increases mortality, whereas 3 yr of the same drought causes partial canopy loss in juniper.

Pain response measured with arterial spin labeling

The majority of functional MRI studies of pain processing in the brain use the blood oxygenation level-dependent (BOLD) imaging approach. However, the BOLD signal is complex as it depends on simultaneous changes in blood flow, vascular volume and oxygen metabolism. Arterial spin labeling (ASL) perfusion imaging is another imaging approach in which the magnetically labeled arterial water is used as an endogenous tracer that allows for direct measurement of cerebral blood flow. In this study, we assessed the pain response in the brain using a pulsed-continuous arterial spin labeling (pCASL) approach and a thermal stimulation paradigm. Using pCASL, response to noxious stimulation was detected in somatosensory cortex, anterior cingulate cortex, anterior insula, hippocampus, amygdala, thalamus and precuneus, consistent with the pain response activation patterns detected using the BOLD imaging approach. We suggest that pCASL is a reliable alternative for functional MRI pain studies in conditions in which blood flow, volume or oxygen extraction are altered or compromised.

Assessment of ductal blood flow in newborns with obstructive left heart lesions by cardiovascular magnetic resonance.

BackgroundNewborns with obstructive left heart lesions often depend on a patent ductus arteriosus to sustain the systemic circulation. Our aims were to validate the direct measurement of ductal flow, and to characterize the magnitude, determinants and hemodynamic effects of patent ductus arteriosus in newborns with obstructive left heart lesions by cardiovascular magnetic resonance (CMR).MethodsIn this retrospective study, the CMR and clinical information of newborns with obstructive left heart lesions were reviewed. The feasibility and validity of measuring ductal flow and the correlations between ductal flow and ventricular volumes, ascending aortic flow, post-ductal oxygen saturation and Qp:Qs were assessed.ResultsThe CMR examinations of 32 newborns were included. It was possible to measure the ductal flow in all of them, with moderate-to-good agreement between measured and calculated ductal flow volume. The flow was bidirectional in all patients, with a net right-to-left shunt in 72%. Net ductal flow correlated inversely with ascending aortic flow (Rho −0.63; p 0.0002), post-ductal oxygen saturation (Rho −0.58; p 0.0004), Qp:Qs (Rho −0.43; p 0.02), and with left ventricular end-diastolic volume index (Rho −0.38; p 0.04). There was no correlation with the diameter of the ductus. The contribution of ductus flow to the systemic circulation correlated with the left ventricular end-diastolic volume index (Rho −0.47; p 0.02).ConclusionsDirect measurement of ductal flow in newborns with obstructive left heart lesions is feasible. From these measurements, we were able to demonstrate that patients with smaller left ventricles and lower ascending aortic flow have a greater contribution of ductal flow to the systemic circulation. The size of the ductus arteriosus does not predict net ductal flow. Phase-contrast CMR can be an adjunct method for the assessment of the physiology for very ill neonate patients.

Intrinsic microvasculature of the sciatic nerve in the rat

Microvasculature associated with the sciatic nerve was examined using high-resolution micro-CT scanning in one group of rats and surgical exploration in another. The results indicate that blood supply to the sciatic nerve is an "open-ended" system in which the vessels run longitudinally within the epineurium and connect with external vasculature primarily at junction points. Although the range of vasculature found extended down to 4-5 μ, only a few isolated vessels of this size were found, with no capillary "mesh" as such, possibly because of the close proximity of the intrinsic vessel to nerve fibers within the epineurium. While the study did not include direct measurements of flow or nerve function, the "open-ended" pattern of vasculature found has important implications regarding the relationship between the two. Specifically, the nerve is less vulnerable to a severe or complete disruption in blood supply than it would be under a close-ended system such as that of the heart or brain, where a severe disruption can occur with the obstruction of only a single vessel. Indeed, the pattern of vasculature found, subject to further study of vasculature at the capillary level, suggests that flow within the intrinsic vessels may be in either direction, depending on circumstances, somewhat like flow within the circle of Willis in the cerebral circulation.

Research on efficiency test of a turbine in Khan Khwar hydropower station

The efficiency test is an important indicator to evaluate the energy conversion performance of a hydraulic turbine. For hydropower stations which do not have the direct flow measurement conditions, whether the characteristic curve of a turbine obtained through similarity theory conversion by using the comprehensive characteristic curve of the turbine can correctly reflect the operating performance of the prototype unit is a key issue in this industry. By taking the No.1 unit of Khan Khwar hydropower station as the example, the efficiency test of this turbine was studied on the site, including the measurement method of test parameters, the configuration of the computer test system, as well as the processing and analysis of test data.

Uncertainty analysis of a virtual water flow measurement in building energy consumption monitoring

The virtual flow meter introduced in this article is developed by calculating water flow rates through two measurable inputs (differential pressure measurements and pump speed measurements) and a calibrated pump curve. However, due to the fact that the flow measurements are achieved by indirect calculations based on multiple input variable measurements, the possibility of error is significantly increased compared with direct flow measurements. This article first introduces the mechanism of virtual flow measurements, analyzes typical errors that can result in incorrect flow readings, and compares the sensitivity index of each input variable and its error impacts on the output variable. Finally, experimental results are presented to validate the uncertainty analysis. As a result, the pump speed is found to be the most influential variable in determining the accuracy of the virtual flow meter. The experiment shows that, compared with the measurement results of an ultrasonic flow meter, a 1% error at full scale (i.e., twice the pump design flow rate) can be achieved with 95% confidence. The analysis in this article demonstrates a theoretical method to quantify the propagated uncertainties of the virtual flow meter through its input variable uncertainties.

CFD–DEM study and direct measurement of the granular flow in a rotor granulator

In this work, the fluid and particle dynamics in a rotor granulator system (fluid bed rotor processor) are investigated. The mathematical model is based on a three-dimensional Computational Fluid Dynamics (CFD) approach for the gas phase coupled with a Discrete Element Method (DEM). The physical properties and collision behaviour of test particles are investigated experimentally and incorporated in a viscoelastic particle contact model. The influence of several process parameters, e.g. air gap velocity and rotor speed, on the particle motion and collision behaviour is investigated.In order to check applicability and limitations of the simulation model, a novel non-intrusive Magnetic Particle Tracking (MPT) technique was used for the continuous measurement of the particle position and orientation of a single tracer particle. Thus particle trajectories as well as translational and angular velocities are obtained. The simulation model shows a good agreement with the experimental results.

Abstract No. 95: Direct intra-access flow measurement as a problem solving tool in hemodialysis access interventions

The technical success of percutaneous dialysis access interventions can usually be determined by physical examination (PE). However, when a discrepancy exists between PE and angiographic findings, we believe that intra-access direct flow measurements offer supplemental information, and thus may be used as a problem solving tool or to gain additional information about the access. The purpose of this study was to identify procedural scenarios in which flow measurements were made and how they affected the chosen course of action.