Simultaneous Measurement Of Flow Velocity Research Articles

Simultaneous Measurement of Flow Velocity and Electrical Conductivity of a Liquid Metal Using an Eddy Current Flow Meter in Combination with a Look-Up-Table Method.

The Eddy Current Flow Meter (ECFM) is a commonly employed inductive sensor for assessing the local flow rate or flow velocity of liquid metals with temperatures up to 700 ∘C. One limitation of the ECFM lies in its dependency on the magnetic Reynolds number for measured voltage signals. These signals are influenced not only by the flow velocity but also by the electrical conductivity of the liquid metal. In scenarios where temperature fluctuations are significant, leading to corresponding variations in electrical conductivity, it becomes imperative to calibrate the ECFM while concurrently monitoring temperature to discern the respective impacts of flow velocity and electrical conductivity on the acquired signals. This paper introduces a novel approach that enables the concurrent measurement of electrical conductivity and flow velocity, even in the absence of precise knowledge of the liquid metal's conductivity or temperature. This method employs a Look-Up-Table methodology. The feasibility of this measurement technique is substantiated through numerical simulations and further validated through experiments conducted on the liquid metal alloy GaInSn at room temperature.

Experimental investigation of aerodynamics and structure of a swirl-stabilized kerosene spray flame with laser diagnostics

A gas turbine model combustor was equipped with an industrial Lean Premixed fuel injection system operating with liquid commercial kerosene (Jet-A1) at atmospheric pressure. Large optical accesses enable joint Particle Image Velocimetry (PIV) and OH planar laser-induced fluorescence (PLIF) measurements at repetition rates up to 5 kHz and 10 kHz, respectively. Using these diagnostics, flame topologies and non-stationary events were investigated in operating conditions representative of the ones encountered in real aeronautic propulsion systems. The flame shape was analyzed in terms of interactions between the different flame zones responsible for flame stabilization in confined swirled flames. Data processing of the strain rate and vorticity fields highlighted the existence of two shear layers that interfere differently with the inlet air/fuel mixing jet. An inner shear layer (ISL) between the Inner Recirculation Zone (IRZ) and the fresh inlet flow is located at the upper base of the fuel spray. An Outer Shear Layer (OSL) is also identified between the Outer Recirculation Zone (ORZ) and the fresh incoming flow. Spanwise-oriented vortices are produced from this latter, with a growth rate function of the free stream speed ratio (fresh incoming reactants and the flow circulating inside ORZ). The detailed analysis of the shear layers gives new insight on the flame structures obtained from OH-PLIF data. Finally, high-speed simultaneous measurements of flow velocity and OH distributions highlighted unusual flame pinching mechanisms leading to the release of subsequent unburned pockets propagating in the burned gases.

Molecular tagging techniques and their applications to the study of complex thermal flow phenomena

This review article reports the recent progress in the development of a new group of molecule-based flow diagnostic techniques, which include molecular tagging velocimetry (MTV) and molecular tagging thermometry (MTT), for both qualitative flow visualization of thermally induced flow structures and quantitative whole-field measurements of flow velocity and temperature distributions. The MTV and MTT techniques can also be easily combined to result in a so-called molecular tagging velocimetry and thermometry (MTV&T) technique, which is capble of achieving simultaneous measurements of flow velocity and temperature distribution in fluid flows. Instead of using tiny particles, the molecular tagging techniques (MTV, MTT, and MTV&T) use phosphorescent molecules, which can be turned into long-lasting glowing marks upon excitation by photons of appropriate wavelength, as the tracers for the flow velocity and temperature measurements. The unique attraction and implementation of the molecular tagging techniques are demonstrated by three application examples, which include: (1) to quantify the unsteady heat transfer process from a heated cylinder to the surrounding fluid flow in order to examine the thermal effects on the wake instabilities behind the heated cylinder operating in mixed and forced heat convection regimes, (2) to reveal the time evolution of unsteady heat transfer and phase changing process inside micro-sized, icing water droplets in order to elucidate the underlying physics pertinent to aircraft icing phenomena, and (3) to achieve simultaneous droplet size, velocity and temperature measurements of “in-flight” droplets to characterize the dynamic and thermodynamic behaviors of flying droplets in spray flows.

Measurement of flow velocity and inference of liquid viscosity in a microfluidic channel by fluorescence photobleaching.

We present a simple, noninvasive method for simultaneous measurement of flow velocity and inference of liquid viscosity in a microfluidic channel. We track the dynamics of a sharp front of photobleached fluorescent dye using a confocal microscope and measure the intensity at a single point downstream of the initial front position. We fit an exact solution of the advection diffusion equation to the fluorescence intensity recovery curve to determine the average flow velocity and the diffusion coefficient of the tracer dye. The dye diffusivity is correlated to solute concentration to infer rheological properties of the liquid. This technique provides a simple method for simultaneous elucidation of flow velocity and liquid viscosity in microchannels.

Validity of the Water Hammer Formula for Determining Regional Aortic Pulse Wave Velocity: Comparison of One-Point and Two-Point (Foot-to-Foot) Measurements Using a Multisensor Catheter in Human

Lack of high-fidelity simultaneous measurements of pressure and flow velocity in the aorta has impeded the direct validation of the water-hammer formula for estimating regional aortic pulse wave velocity (AO-PWV1) and has restricted the study of the change of beat-to-beat AO-PWV1 under varying physiological conditions in man. Aortic pulse wave velocity was derived using two methods in 15 normotensive subjects: 1) the conventional two-point (foot-to-foot) method (AO-PWV2) and 2) a one-point method (AO-PWV1) in which the pressure velocity-loop (PV-loop) was analyzed based on the water hammer formula using simultaneous measurements of flow velocity (Vm) and pressure (Pm) at the same site in the proximal aorta using a multisensor catheter. AO-PWV1 was calculated from the slope of the linear regression line between Pm and Vm where wave reflection (Pb) was at a minimum in early systole in the PV-loop using the water hammer formula, PWV1 = (Pm/Vm)/ρ, where ρ is the blood density. AO-PWV2 was calculated using the conventional two-point measurement method as the distance/traveling time of the wave between 2 sites for measuring P in the proximal aorta. Beat-to-beat alterations of AO-PWV1 in relationship to aortic pressure and linearity of the initial part of the PV-loop during a Valsalva maneuver were also assessed in one subject. The initial part of the loop became steeper in association with the beat-to-beat increase in diastolic pressure in phase 4 during the Valsalva maneuver. The linearity of the initial part of the PV-loop was maintained consistently during the maneuver. Flow velocity vs. pressure in the proximal aorta was highly linear during early systole, with Pearson's coefficients ranging from 0.9954 to 0.9998. The average values of AO-PWV1 and AO-PWV2 were 6.3 ± 1.2 and 6.7 ± 1.3 m/s, respectively. The regression line of AO-PWV1 on AO-PWV2 was y = 0.95x + 0.68 (r = 0.93, p <0.001). This study concluded that the water-hammer formula (one-point method) provides a reliable and conventional estimate of beat-to-beat aortic regional pulse wave velocity consistently regardless of the changes in physiological states in human clinically. (English Translation of J Jpn Coll Angiol 2011; 51: 215-221).

Thermal effects on the wake of a heated circular cylinder operating in mixed convection regime

AbstractThe thermal effects on the wake flow behind a heated circular cylinder operating in the mixed convection regime were investigated experimentally in the present study. The experiments were conducted in a vertical water channel with the heated cylinder placed horizontally and the flow approaching the cylinder downwards. With such a flow arrangement, the direction of the thermally induced buoyancy force acting on the fluid surrounding the heated cylinder would be opposite to the approach flow. During the experiments, the temperature and Reynolds number of the approach flow were held constant. By adjusting the surface temperature of the heated cylinder, the corresponding Richardson number ($\mathit{Ri}= \mathit{Gr}/ {\mathit{Re}}^{2} $) was varied between 0.0 (unheated) and 1.04, resulting in a change in the heat transfer process from forced convection to mixed convection. A novel flow diagnostic technique, molecular tagging velocimetry and thermometry (MTV&amp;T), was used for qualitative flow visualization of thermally induced flow structures and quantitative, simultaneous measurements of flow velocity and temperature distributions in the wake of the heated cylinder. With increasing temperature of the heated cylinder (i.e. Richardson number), significant modifications of the wake flow pattern and wake vortex shedding process were clearly revealed. When the Richardson number was relatively small ($\mathit{Ri}\leq 0. 31$), the vortex shedding process in the wake of the heated cylinder was found to be quite similar to that of an unheated cylinder. As the Richardson number increased to${\ensuremath{\sim} }0. 50$, the wake vortex shedding process was found to be ‘delayed’, with the wake vortex structures beginning to shed much further downstream. As the Richardson number approached unity ($\mathit{Ri}\geq 0. 72$), instead of having ‘Kármán’ vortices shedding alternately at the two sides of the heated cylinder, concurrent shedding of smaller vortex structures was observed in the near wake of the heated cylinder. The smaller vortex structures were found to behave more like ‘Kelvin–Helmholtz’ vortices than ‘Kármán’ vortices, and adjacent small vortices would merge to form larger vortex structures further downstream. It was also found that the shedding frequency of the wake vortex structures decreased with increasing Richardson number. The wake closure length and the drag coefficient of the heated cylinder were found initially to decrease slightly when the Richardson number was relatively small ($\mathit{Ri}\lt 0. 31$), and then to increase monotonically with increasing Richardson number as the Richardson number became relatively large ($\mathit{Ri}\gt 0. 31$). The average Nusselt number ($ \overline{\mathit{Nu}} $) of the heated cylinder was found to decrease almost linearly with increasing Richardson number.

A novel molecular tagging technique for simultaneous measurements of flow velocity and temperature fields

A novel molecular tagging technique for simultaneous measurements of flow velocity and temperature fields

Simultaneous measurement of flow velocity and Doppler angle by the use of Doppler optical coherence tomography

Monitoring blood flow velocity could have great value for biomedical research and clinical diagnostics. One of current restrictions to determine flow velocity by the use of Doppler optical coherence tomography (Doppler OCT) is that the Doppler angle should be predefined. However, from a practical point of view, it is not easy to predetermine Doppler angle for a flow beneath the tissue surface. In this work, a novel method for measuring both flow velocity and Doppler angle simultaneously by the use of Doppler OCT is proposed and demonstrated. Based on Doppler spectrum analysis, this technique measures both longitudinal and transverse components of flow velocity by detecting its Doppler shift and Doppler bandwidth to determine velocity and Doppler angle simultaneously. Such a technique extends flow velocity measurement into a broadening practical use of Doppler OCT where Doppler angle would not need to be predefined, for example, blood flow beneath the tissue surface. Therefore, with this technique, Doppler OCT could be applied to more practical diagnoses of microcirculation.

A numerical investigation of flow past a bluff body using three-state anemometry

SUMMARY An application of a new flow measurement technique is described which allows for the non-intrusive simultaneous measurement of flow velocity, density, and viscosity. The viscosity information can be used to derive the flow field temperature. The combination of the three measured variables and the perfect-gas law then leads to an estimate of the flow field thermodynamic pressure. Thus, the instantaneous state of a flow field can be completely described. Three-state anemometry (3SA), a derivative of particle image velocimetry (PIV), which uses a combination of three monodisperse sizes of styrene seeding particles is proposed. A marker seeding is chosen to follow the flow as closely as possible, while intermediate and large seeding populations provide two supplementary velocity fields, which are also dependent on fluid density and viscosity. A simplified particle motion equation, aimed at turbomachinery applications, is then solved over the whole field to provide both density and viscosity data. The three velocity fields can be separated in a number of ways. The simplest and that proposed in this paper is to dye the different populations and view the region of interest through interferometric filters. The two critical aspects needed to enable the implementation of such a technique are a suitable selection of the diameters of the particle populations, and the separation of the velocity fields. There has been extensive work on the seeding particle behaviour which allows an estimate of the suitable particle diameters to be made. A technique is described in this paper to allow the separation of particles in a range of micrometer sized velocity fields through fluorescence (separation through intensity also being possible). Some preliminary results by direct numerical simulation (DNS) of a 3SA image are also presented. The particle sizes chosen were 1 mm and 5 mm, tested on the near-wake flow past a cylinder to investigate viscosity only, assuming uniform flow density. The accuracy of the technique, derived from simulations of swirling flows, is estimated as 0.5% RMS for velocity, 2% RMS for the density and viscosity, and 4% RMS for the temperature estimate. © 1998 John Wiley & Sons, Ltd.

Relationship between haemodynamics and morphology in pulmonary hypertension. A quantitative intravascular ultrasound study.

Intravascular ultrasound imaging of the pulmonary arteries has been demonstrated to be a reliable method of quantifying vessel diameter, luminal area and pulsatility. Simultaneous measurement of flow velocity and its response to vasodilators allows the relationship between morphology and functional compromise to be studied, especially endothelial dysfunction. In 51 patients (mean age = 49.8 +/- 12.6 years, 17 female) we performed right heart catheterization and simultaneous intravascular ultrasound of pulmonary artery branches. The patients were divided in two groups: group 1 with normal pulmonary artery pressure and pulmonary vascular resistance, and group 2 with pulmonary hypertension (peak pulmonary artery pressure > 30 mmHg and/or mean pulmonary artery pressure > 20 mmHg). Vessel wall and lumen were studied using a 2.9 F intravascular ultrasound catheter with a 30 MHz phased array transducer. Measurement of blood flow velocity was accomplished by a Doppler flow wire (0.018 inch). The maximal flow change during acetylcholine infusion (adjusted to 10(-6); 10(-5), and 10(-4) M concentration in the blood vessel) was measured. There were no significant differences between groups 1 and 2 with respect to age (48.5 +/- 14.3 years vs 50.3 +/- 12.3 years; P = ns), gender (4 female/8 male vs 13 female/26 male; P = ns), luminal area of the vessel segment in which the intravascular ultrasound measurements were obtained (11.8 +/- 6.1 mm2 vs 16.7 +/- 14.3 mm2; P = ns), internal diameter (3.9 +/- 1.2 mm vs 4.2 +/- 1.7 mm; P = ns), and external diameter (6.1 +/- 1.3 mm vs 6.9 +/- 2.1 mm; P = ns). Cross-sectional images of the pulmonary artery wall demonstrated a single ring with high echodensity with a thin inner layer regarded as intima in group 1. In contrast, the majority of patients (n = 35/39) in group 2 demonstrated a thickening of the intimal layer and/or a disturbance of layering of the echogenic arterial wall. The relative wall thickness was higher in group 2 than in group 1 (22.5 +/- 10.4% vs 15.3 +/- 6.5%; P < 0.05). There were no significant correlations between pulmonary artery pressure and wall thickness pulmonary artery pressure and area change in the cardiac cycle, acetylcholine-dependent increase in pulmonary flow and morphological changes in the vessel wall. We conclude that intravascular ultrasound is capable of detecting morphological changes in the pulmonary vessel wall in pulmonary hypertension and that vessel wall hypertrophy of small pulmonary segment arteries, as detected by intravascular ultrasound, is not predictive of functional vasodilatory response of resistance vessels of the same vessel area.

An integrated mass flow sensor with on-chip CMOS interface circuitry

A multielement monolithic mass flow sensor which developed for possible use in automotive and industrial process control applications is reported. The chip illustrates the use of a common microstructure (a thin dielectric window/diaphragm) for the simultaneous measurement of flow velocity (rate), flow direction, gas type, and pressure. These transducers are merged with on-chip interface electronics to amplify and multiplex the transducer signals, control on-chip actuators, perform self-test, reduce the number of external leads required, and demonstrate process compatibility with a p-well CMOS process. The on-chip circuitry also implements a bandgap sensor for the measurement of ambient temperature. Thus, the chip simultaneously monitors all parameters needed for the computation of true mass flow, requires only ten external leads, and delivers high-level buffered output signals.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Noncontact optoacoustic determination of gas flow velocity and temperature simultaneously

We have developed a new noncontact optoacoustic method for simultaneous measurement of flow velocity and temperature in a flowing fluid to accuracies of 5 cm/s and 0.1 °C, respectively. It is applicable for pure particulate-free gases and liquids. A pulsed ND-doped yttrium aluminum garnet (YAG) laser of 40-mJ energy and 10-ns duration generates an acoustic pulse whose propagations in directions along and against the flow are monitored by a total of three cw probe beams. We also describe the minimization of errors due to a blast wave (which propagates faster than sound) being generated at the source.