scholarly journals Measuring Hydrometeors with a Precipitation Microphysical Characteristics Sensor: Calibration and Field Measurements

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Yuntao Hu ◽  
Xichuan Liu ◽  
Taichang Gao ◽  
Xiaojian Shu
Keyword(s):  
Field Measurements ◽  
Rain Gauge ◽  
Sensor Calibration ◽  
Threshold Method ◽  
Fall Velocity ◽  
Axis Ratio ◽  
Measurement Results ◽  
Accumulated Rainfall ◽  
Typical Shape ◽  
Particle Imaging

Aiming at the simultaneous measurement of the size, shape, and fall velocity of precipitation particles in the natural environment, we present here a new ground-based precipitation microphysical characteristics sensor (PMCS) based on the particle imaging velocimetry technology. The PMCS can capture autocorrelated images of precipitation particles by double-exposure in one frame, by which the size, axis ratio, and fall velocity of precipitation particles can be calculated. The PMCS is calibrated by a series of glass balls with certain diameters under varying light conditions, and a self-adaptive threshold method is proposed. The shape, axis ratio, and fall velocity of raindrops were calculated and discussed based on the field measurement results of PMCS. The typical shape of large raindrop is an oblate ellipsoid, the axis ratio of raindrops decreases linearly with the diameter, the fall velocity of raindrops approaches its asymptote, and the above observed results are in good agreement with the empirical models; the synchronous observation of a PMCS, an OTT PARSIVEL disdrometer, and a rain gauge shows that the PMCS is able to measure the rain intensity, accumulated rainfall, and drop size distribution with high accuracy. These results have validated the performance of PMCS.

Snowflakes in the atmospheric surface layer: observation of particle–turbulence dynamics

2017 ◽  
Vol 814 ◽  
pp. 592-613 ◽  
Author(s):  
Andras Nemes ◽  
Teja Dasari ◽  
Jiarong Hong ◽  
Michele Guala ◽  
Filippo Coletti
Keyword(s):  
Large Scale ◽  
Isotropic Turbulence ◽  
Volume Fraction ◽  
Response Times ◽  
Field Measurements ◽  
Stokes Number ◽  
Inertial Particles ◽  
Natural Setting ◽  
Scale Particle ◽  
Particle Imaging

We report on optical field measurements of snow settling in atmospheric turbulence at $Re_{\unicode[STIX]{x1D706}}=940$. It is found that the snowflakes exhibit hallmark features of inertial particles in turbulence. The snow motion is analysed in both Eulerian and Lagrangian frameworks by large-scale particle imaging, while sonic anemometry is used to characterize the flow field. Additionally, the snowflake size and morphology are assessed by digital in-line holography. The low volume fraction and mass loading imply a one-way interaction with the turbulent air. Acceleration probability density functions show wide exponential tails consistent with laboratory and numerical studies of homogeneous isotropic turbulence. Invoking the assumption that the particle acceleration has a stronger dependence on the Stokes number than on the specific features of the turbulence (e.g. precise Reynolds number and large-scale anisotropy), we make inferences on the snowflakes’ aerodynamic response time. In particular, we observe that their acceleration distribution is consistent with that of particles of Stokes number in the range $St=0.1{-}0.4$ based on the Kolmogorov time scale. The still-air terminal velocities estimated for the resulting range of aerodynamic response times are significantly smaller than the measured snow particle fall speed. This is interpreted as a manifestation of settling enhancement by turbulence, which is observed here for the first time in a natural setting.

An Impedance Sensor of Water Cut with Three Electrodes and Relative Analysis on Experiment Results

2021 ◽  
Author(s):  
Chuan Yu ◽  
Qinghai Yang ◽  
Songbo Wei ◽  
Ming Li ◽  
Tao Fu
Keyword(s):  
Single Layer ◽  
High Water ◽  
Sensor Calibration ◽  
Mixing Ratios ◽  
Margin Of Error ◽  
Measurement Results ◽  
Oil Water ◽  
High Water Cut ◽  
Water Cut ◽  
Impedance Sensor

Abstract Single-layer water cut measurement is of great significance for identifying and shutting off the unwanted water, analyzing oil remained and optimizing production. Currently, however, only the water cut of multilayer mixture can be measured by testing samples taken from wellhead, a way which is widely used in oilfields. That of single-layer fluid cannot be determined yet To address the problem, this paper puts forward a new impedance sensor that offers long-term online monitoring of single-layer water cut. This sensor is based on the different electrical conductivity of oil and water. It has two layers. The inner one contains three electrodes - two at both sides sending sinusoidal excitation signals and one at the middle receiving signals that have been attenuated by the water-oil medium. With the Maxwell's model of oil-water mixed fluid, the receiver then can measure the water cut online. The outer layer of the sensor is made of PEEK, an insulative protection. In front of the electrodes lies a static mixer which makes the measurement more accurate by fully blending the two media when they flow through the electrodes. Laboratory tests are carried out with the prototype of the sensor at various oil-water mixing ratios, fluid flow rates, and temperatures. Results show that the average margin of error is within ± 3%. Higher accuracy is seen when high water cut and flow rate enable oil globules to disperse more evenly and the space in between to get wider and the RMS error is less than 2%. If the water cut drops below 80%, the aggregation of the droplets will cause wild fluctuation and more errors in the measurement. In addition, the mineralization of the mixture directly changes its conductivity, which largely impacts the result. Meanwhile, temperature can influence the ionic movement intensity and then alter the conductivity of the medium. Therefore, in practice, the sensor calibration needs to be performed according to the range of medium salinity, and the temperature of the medium is collected in real time for temperature compensation. It is shown that after the adjustment, the water cut measurement results have higher accuracy and consistency. The impedance sensor can realize online water cut monitoring for a single-layer, indicated by tests. It is more suitable for the increasing high water cut oilfields in that it is more accurate as the water cut grows.

scholarly journals Characterising optical array particle imaging probes: implications for small-ice-crystal observations

2021 ◽  
Vol 14 (3) ◽  
pp. 1917-1939
Author(s):  
Sebastian O'Shea ◽  
Jonathan Crosier ◽  
James Dorsey ◽  
Louis Gallagher ◽  
Waldemar Schledewitz ◽  
...  
Keyword(s):  
Field Experiments ◽  
Field Measurements ◽  
Sample Volume ◽  
Ice Crystal ◽  
Cloud Particle ◽  
Ice Clouds ◽  
Cloud Properties ◽  
Imaging Probes ◽  
New Methodologies ◽  
Particle Imaging

Abstract. The cloud particle concentration, size, and shape data from optical array probes (OAPs) are routinely used to parameterise cloud properties and constrain remote sensing retrievals. This paper characterises the optical response of OAPs using a combination of modelling, laboratory, and field experiments. Significant uncertainties are found to exist with such probes for ice crystal measurements. We describe and test two independent methods to constrain a probe's sample volume that remove the most severely mis-sized particles: (1) greyscale image analysis and (2) co-location using stereoscopic imaging. These methods are tested using field measurements from three research flights in cirrus. For these cases, the new methodologies significantly improve agreement with a holographic imaging probe compared to conventional data-processing protocols, either removing or significantly reducing the concentration of small ice crystals (< 200 µm) in certain conditions. This work suggests that the observational evidence for a ubiquitous mode of small ice particles in ice clouds is likely due to a systematic instrument bias. Size distribution parameterisations based on OAP measurements need to be revisited using these improved methodologies.

scholarly journals Near-Field Antenna Measurements with Manual Collection of the Measurement Samples

2020 ◽  
Vol 18 ◽  
pp. 17-22
Author(s):  
Fabian T. Faul ◽  
Hans-Jürgen Steiner ◽  
Thomas F. Eibert
Keyword(s):  
Near Field ◽  
Field Measurements ◽  
Controlled Environment ◽  
Positioning System ◽  
Probe Position ◽  
Site Testing ◽  
Error Level ◽  
Measurement Results ◽  
Anechoic Chambers ◽  
Chamber Measurements

Abstract. Near-field measurements are commonly performed in anechoic chambers which limits the flexibility of the measurements and requires high precision equipment to achieve exact results. In this contribution, we investigate a simple near-field measurement setup which does not use any sophisticated positioning system nor operates in a controlled environment. Instead, the probe antenna is moved by an operator person while the probe position is measured by a laser tracker. This implies that the measurement results will have a higher error level in comparison with antenna chamber measurements. However, excellent error levels are not always necessary, especially when it comes to on-site testing of the principle functionality of antennas. Measurement results are shown to illustrate the performance of the system.

scholarly journals Measurement-based modeling of daytime and nighttime oxidation of atmospheric mercury

2017 ◽  
Author(s):  
Maor Gabay ◽  
Mordechai Peleg ◽  
Erick Fredj ◽  
Eran Tas
Keyword(s):  
Lower Limit ◽  
Rate Constant ◽  
Field Measurements ◽  
Elemental Mercury ◽  
Chemical Oxidation ◽  
Atmospheric Mercury ◽  
Gaseous Elemental Mercury ◽  
Measurement Results ◽  
Kinetic Calculations ◽  
First Time

Abstract. Accurate characterization of gaseous elemental mercury (GEM) chemical oxidation pathways and their kinetics is critically important for assessing the transfer of atmospheric mercury to bioaquatic systems. Recent comprehensive field measurements have suggested that the nitrate radical (NO3) plays a role in efficient nighttime oxidation of GEM, and that the role of the hydroxyl radical (OH) as a GEM oxidant has been underestimated. We used the CAABA/MECCA chemical box model and additional kinetic calculations to analyze these measurement results, in order to investigate the nighttime and daytime oxidation of GEM. We assumed a second-order reaction for the NO3 induced nighttime oxidation of GEM. Our analysis demonstrated that nighttime oxidation of GEM has to be included in the model to account for the measured variations in nighttime reactive gaseous mercury (RGM) concentration. A lower limit and best-fit rate constant for GEM nighttime oxidation are provided. To the best of our knowledge, this is the first time that a rate for nighttime oxidation of GEM has been determined based on field measurements. Our analysis further indicates that OH has a much more important role in GEM oxidation than commonly considered. A lower-limit rate constant for the OH–RGM reaction is provided.

scholarly journals High-Speed Optical Disdrometer for Rainfall Microphysical Observations

2016 ◽  
Vol 33 (2) ◽  
pp. 231-243 ◽  
Author(s):  
F. Y. Testik ◽  
M. K. Rahman
Keyword(s):  
High Speed ◽  
Focal Depth ◽  
Field Tests ◽  
Video Camera ◽  
Rain Gauge ◽  
Accurate Information ◽  
Fall Velocity ◽  
Led Light ◽  
High Speed Video ◽  
High Speed Video Camera

AbstractA high-speed optical disdrometer (HOD) that was developed for measuring rainfall microphysical quantities, including raindrop shape, size distribution, and fall velocity/acceleration, is the subject of this paper. The main components of the HOD are a high-speed video camera, a light-emitting diode (LED) light, and a sensing unit to detect raindrops passing through the camera view frame. The high-speed video camera is directed at the LED light to capture the silhouettes of the backlit drops when triggered by a raindrop that is detected within a specified focal depth by the sensing unit. The use of a sensing unit enables the confinement of a measurement volume around the camera focal plane. This innovative operation principle ensures the capture of sharp images of raindrop silhouettes, which are then digitally processed to provide accurate information on various raindrop characteristics. The measurement capabilities of the HOD were evaluated through both laboratory and field tests. In the laboratory tests, high-precision spherical lenses with known diameters and water drops of different sizes generated for a known volume of water were used. In the field tests, the HOD was evaluated against a reference rain gauge in a number of rain events. These tests demonstrated the precise accuracy of HOD measurements and the HOD’s technological readiness for field deployment for various applications. It is expected that the HOD will play an important role in generating new insights on raindrop dynamics and related research through its unique measurement capability of providing sequential high-speed images of raindrops.

scholarly journals The flow field downstream of a hydraulic jump

1995 ◽  
Vol 287 ◽  
pp. 299-316 ◽  
Author(s):  
Hans G. Hornung ◽  
Christian Willert ◽  
Stewart Turner
Keyword(s):  
Flow Field ◽  
Froude Number ◽  
Hydraulic Jump ◽  
Control Volume ◽  
Field Measurements ◽  
Number Range ◽  
Strong Shear ◽  
The Mean ◽  
Generation Mechanisms ◽  
Particle Imaging

A control-volume analysis of a hydraulic jump is used to obtain the mean vorticity downstream of the jump as a function of the Froude number. To do this it is necessary to include the conservation of angular momentum. The mean vorticity increases from zero as the cube of Froude number minus one, and, in dimensionless form, approaches a constant at large Froude number. Digital particle imaging velocimetry was applied to travelling hydraulic jumps giving centre-plane velocity field images at a frequency of 15 Hz over a Froude number range of 2–6. The mean vorticity determined from these images confirms the control-volume prediction to within the accuracy of the experiment. The flow field measurements show that a strong shear layer is formed at the toe of the wave, and extends almost horizontally downstream, separating from the free surface at the toe. Various vorticity generation mechanisms are discussed.

The Numerical Simulation of Underwater Electric Field Sensor Calibration Traceability

2014 ◽  
Vol 548-549 ◽  
pp. 646-649
Author(s):  
Ping Hu ◽  
Rui Yong Yue ◽  
Ji Tian
Keyword(s):  
Numerical Simulation ◽  
Electric Field ◽  
Magnetic Field Gradient ◽  
Gradient Methods ◽  
Field Measurements ◽  
Test Methods ◽  
Sensor Calibration ◽  
Electric Field Sensors ◽  
Electric Field Sensor ◽  
Field Sensor

The traceability of underwater electric field sensors is to track the most essential reason for underwater electric field generated by the sensor.When exploring marine electromagnetic field by underwater electric field sensors ,the underwater electric field sensor calibration traceability of the underwater electric field directly affects the final research significance .Therefore,the underwater electric field sensor calibration traceability technique is very important.The underwater electric field sensor calibration traceability is still in its infancy in our country recently .In this paper,underwater electric field sensor calibration traceability based on Ohm's law and magnetic field gradient methods are proposed through theoretical analysis and numerical simulation,which provide test methods for our underwater electric field sensor calibration and solve the bottleneck problem of underwater electric field measurements.

scholarly journals A Preliminary Study on the Adaptive SNR Threshold Method for Depth of Penetration Measurements in Diagnostic Ultrasounds

2020 ◽  
Vol 10 (18) ◽  
pp. 6533
Author(s):  
Giorgia Fiori ◽  
Fabio Fuiano ◽  
Andrea Scorza ◽  
Jan Galo ◽  
Silvia Conforto ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
General Purpose ◽  
Threshold Method ◽  
Depth Of Penetration ◽  
Naked Eye ◽  
Measurement Results ◽  
Automatic Methods ◽  
The Mean ◽  
Preliminary Study ◽  
Adaptive Signal

Maximum depth of penetration (DOP) is among the most relevant parameters in quality assurance programs for Ultrasound (US) scanners. Nowadays, a generally-accepted protocol for DOP estimation is still awaited and, in common practice, DOP is visually assessed despite the low accuracy. To overcome the eye-based assessment subjectivity, automatic image analysis methods have been proposed in literature. The present work focuses on a novel automatic method, namely the adaptive Signal to Noise Ratio (SNR) threshold method (AdSTM), developed in the MATLAB environment, by comparing it with an existing automatic approach, namely the tangent threshold method (TTM), and the mean judgment of eight observers (naked eye method). The three investigated methods were applied on data acquired from four US scanners for general purpose imaging, equipped with linear, convex, and vector array probes. Tests were carried out in two different configuration settings (raw scanner and default preset working conditions). AdSTM outcomes were tested by means of Monte Carlo Simulations. Most of measurement results were compatible despite the fact that the AdSTM seemed to be more sensitive and faster than the TTM. The results analysis confirms the higher dispersion of the naked eye method in DOP assessment with respect to the proposed automatic methods.

Microprocessor Field Impactometer Calibration: Do We Measure Drops’ Momentum or Their Kinetic Energy?

2008 ◽  
Vol 25 (5) ◽  
pp. 742-753 ◽  
Author(s):  
Paweł Licznar ◽  
Janusz Łomotowski ◽  
Sławomir Błoński ◽  
Grzegorz J. Ciach
Keyword(s):  
Kinetic Energy ◽  
Physical Quantity ◽  
Calibration Curve ◽  
High Speed ◽  
Low Cost ◽  
Field Measurements ◽  
Rain Gauge ◽  
High Speed Photography ◽  
Sensor Output ◽  
Impact Position

Abstract This study presents the construction and calibration of a low-cost piezoelectric microprocessor impactometer designed for the field measurements of the rainfall kinetic energy (KE) flux. Its precise calibration was performed in laboratory conditions using waterdrops of different sizes and fall velocities. High-speed photography was applied to measure the velocity of each waterdrop. Although the impactometer constructed for this study is not able to measure the momentum of waterdrops, its accuracy for measuring their KE is excellent. It was found that the processing of the piezoelectric signal might determine which physical quantity is measured by different impactometers. It was also found that the distance between the waterdrop impact position and the impactometer center has a significant effect on the sensor output. A scheme to account for this effect is developed in this study, and the calibration curve for field applications of the impactometer is derived. In addition, an example comparison of the concurrent field measurements of KE flux using the impactometer and rainfall rates using a weighing rain gauge is given.

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