scholarly journals An Autonomous Open-Ocean Stereoscopic PIV Profiler

2010 ◽  
Vol 27 (8) ◽  
pp. 1362-1380 ◽  
Author(s):  
Jonah V. Steinbuck ◽  
Paul L. D. Roberts ◽  
Cary D. Troy ◽  
Alexander R. Horner-Devine ◽  
Fernando Simonet ◽  
...  
Keyword(s):  
Flow Direction ◽  
Vertical Plane ◽  
Free Fall ◽  
Open Ocean ◽  
Stereoscopic Particle Image Velocimetry ◽  
Frame Rate ◽  
Energy Estimates ◽  
Seeding Density ◽  
Stereoscopic Piv

Abstract Over the past decade, a novel free-fall imaging profiler has been under development at the Scripps Institution of Oceanography to observe and quantify biological and physical structure in the upper 100 m of the ocean. The profiler provided the first detailed view of microscale phytoplankton distributions using in situ planar laser-induced fluorescence. The present study examines a recent incarnation of the profiler that features microscale turbulent flow measurement capabilities using stereoscopic particle image velocimetry (PIV). As the profiler descends through the water column, a vertical sheet of laser light illuminates natural particles below the profiler. Two sensitive charge-coupled device (CCD) cameras image a 25 cm × 25 cm × 0.6 cm region at a nominal frame rate of 8 Hz. The stereoscopic camera configuration allows all three components of velocity to be measured in the vertical plane with an average spatial resolution of approximately 3 mm. The performance of the PIV system is evaluated for deployments offshore of the southern California coast. The in situ image characteristics, including natural particle seeding density and imaged particle size, are found to be suitable for PIV. Ensemble-averaged velocity and dissipation of turbulent kinetic energy estimates from the stereoscopic PIV system are consistent with observations from an acoustic Doppler velocimeter and acoustic Doppler current profiler, though it is revealed that the present instrument configuration influences the observed flow field. The salient challenges in adapting stereoscopic PIV for in situ, open-ocean turbulence measurements are identified, including cross-plane particle motion, instrument intrusiveness, and measurement uncertainty limitations. These challenges are discussed and recommendations are provided for future development: improved alignment with the dominant flow direction, mitigation of instrument intrusiveness, and improvements in illumination and imaging resolution.

scholarly journals Multi-Camera Based Setup for Geometrical Measurement of Free-Falling Molten Glass Gob

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1041
Author(s):  
Mazhar Hussain ◽  
Mattias O’Nils ◽  
Jan Lundgren
Keyword(s):  
Free Fall ◽  
Frame Rate ◽  
Geometrical Parameters ◽  
Contactless Method ◽  
Molten Material ◽  
Dynamic Changes ◽  
Direct Measurements ◽  
Molten Materials ◽  
Free Falling

High temperatures complicate the direct measurements needed for continuous characterization of the properties of molten materials such as glass. However, the assumption that geometrical changes when the molten material is in free-fall can be correlated with material characteristics such as viscosity opens the door to a highly accurate contactless method characterizing small dynamic changes. This paper proposes multi-camera setup to achieve accuracy close to the segmentation error associated with the resolution of the images. The experimental setup presented shows that the geometrical parameters can be characterized dynamically through the whole free-fall process at a frame rate of 600 frames per second. The results achieved show the proposed multi-camera setup is suitable for estimating the length of free-falling molten objects.

scholarly journals A Pixel Design of a Branching Ultra-Highspeed Image Sensor

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2506
Author(s):  
Nguyen Hoai Ngo ◽  
Kazuhiro Shimonomura ◽  
Taeko Ando ◽  
Takayoshi Shimura ◽  
Heiji Watanabe ◽  
...  
Keyword(s):  
Image Sensor ◽  
Frame Rate ◽  
Front Side ◽  
Digital Signals ◽  
Memory Element ◽  
Image Capture ◽  
Readout Circuits ◽  
Pros And Cons ◽  
Very High

A burst image sensor named Hanabi, meaning fireworks in Japanese, includes a branching CCD and multiple CMOS readout circuits. The sensor is backside-illuminated with a light/charge guide pipe to minimize the temporal resolution by suppressing the horizontal motion of signal carriers. On the front side, the pixel has a guide gate at the center, branching to six first-branching gates, each bifurcating to second-branching gates, and finally connected to 12 (=6×2) floating diffusions. The signals are either read out after an image capture operation to replay 12 to 48 consecutive images, or continuously transferred to a memory chip stacked on the front side of the sensor chip and converted to digital signals. A CCD burst image sensor enables a noiseless signal transfer from a photodiode to the in-situ storage even at very high frame rates. However, the pixel count conflicts with the frame count due to the large pixel size for the relatively large in-pixel CCD memory elements. A CMOS burst image sensor can use small trench-type capacitors for memory elements, instead of CCD channels. However, the transfer noise from a floating diffusion to the memory element increases in proportion to the square root of the frame rate. The Hanabi chip overcomes the compromise between these pros and cons.

scholarly journals Stereoscopic PIV measurements using low-cost action cameras

2021 ◽  
Vol 62 (3) ◽  
Author(s):  
Theo Käufer ◽  
Jörg König ◽  
Christian Cierpka
Keyword(s):  
Continuous Wave ◽  
Low Cost ◽  
Frame Rate ◽  
Processing Scheme ◽  
Piv Measurements ◽  
Stereoscopic Piv ◽  
Cost Action ◽  
Image Velocimetry ◽  
Frequency Generator ◽  
Educational Applications

Abstract Recently, large progress was made in the development towards low-cost PIV (Particle Image Velocimetry) for industrial and educational applications. This paper presents the use of two low-cost action cameras for stereoscopic planar PIV. A continuous wave laser or alternatively an LED was used for illumination and pulsed by a frequency generator. A slight detuning of the light pulsation and camera frame rate minimizes systematic errors by the rolling shutter effect and allows for the synchronization of both cameras by postprocessing without the need of hardware synchronization. The setup was successfully qualified on a rotating particle pattern in a planar and stereoscopic configuration as well as on the jet of an aquarium pump. Since action cameras are intended to be used at outdoor activities, they are small, very robust and work autarkic. In conjunction with the synchronization and image pre-processing scheme presented herein, those cameras enable stereoscopic PIV in harsh environments and even on moving experiments. Graphic abstract

An In-Situ Free-Fall Piezocone Penetrometer for Characterizing Soft and Sensitive Clays at Finneidfjord (Northern Norway)

2011 ◽  
pp. 99-109 ◽  
Author(s):  
Alois Steiner ◽  
Jean-Sebastien L’Heureux ◽  
Achim Kopf ◽  
Maarten Vanneste ◽  
Oddvar Longva ◽  
...  
Keyword(s):  
Free Fall ◽  
Northern Norway

Flow induced crystallization of LDPE nanocomposites: A rheological and morphological characterization

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Fiorenza Azzurri ◽  
Paola Stagnaro ◽  
Lucia Conzatti ◽  
Dario Cavallo ◽  
Luca Repetto ◽  
...  
Keyword(s):  
Shear Flow ◽  
Flow Direction ◽  
Crystallization Rate ◽  
Morphological Characterization ◽  
External Flow ◽  
Nucleation Density ◽  
Induced Crystallization ◽  
Flow Induced Crystallization ◽  
Nucleating Effect

AbstractThe flow induced crystallization behaviour of a LDPE:PE-g-MA:D72T 90:9:1 nanocomposite has been investigated by in-situ Rheo-SALS technique and data have been compared with those obtained from a reference LDPE:PE-g-MA 90:9 sample. Rheo SALS results, confirming thermal analysis findings, indicate that under mild shear flow fields the organoclay exhibits a negligible nucleating effect. Both nucleation density and, as a consequence, crystallization rate, are not appreciably affected by the application of external flow field for both the examined systems, revealing that no evident synergic effects between the organoclay and the shear flow are present. On the other hand, Rheo SALS analysis indicates that the nanocomposite submitted to flow exhibits a higher level of crystal orientation. TEM morphological analyses support this observation suggesting that the orientation of the nanofiller along the flow direction templates the growth of oriented crystals.

scholarly journals Bromocarbons in the tropical coastal and open ocean atmosphere during the 2009 Prime Expedition Scientific Cruise (PESC-09)

2014 ◽  
Vol 14 (15) ◽  
pp. 8137-8148 ◽  
Author(s):  
M. S. Mohd Nadzir ◽  
S. M. Phang ◽  
M. R. Abas ◽  
N. Abdul Rahman ◽  
A. Abu Samah ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Statistical Tests ◽  
Open Ocean ◽  
Common Source ◽  
Sampling Point ◽  
Coastal Regions ◽  
Chl A ◽  
June July ◽  
Strait Of Malacca

Abstract. Atmospheric concentrations of very short-lived species (VSLS) bromocarbons, including CHBr3, CH2Br2, CHCl2Br, CHClBr2, and CH2BrCl, were measured in the Strait of Malacca and the South China and Sulu–Sulawesi seas during a two-month research cruise in June–July 2009. The highest bromocarbon concentrations were found in the Strait of Malacca, with smaller enhancements in coastal regions of northern Borneo. CHBr3 was the most abundant bromocarbon, ranging from 5.2 pmol mol−1 in the Strait of Malacca to 0.94 pmol mol−1 over the open ocean. Other bromocarbons showed lower concentrations, in the range of 0.8–1.3 pmol mol−1 for CH2Br2, 0.1–0.5 pmol mol−1 for CHCl2Br, and 0.1–0.4 pmol mol−1 for CHClBr2. There was no significant correlation between bromocarbons and in situ chlorophyll a, but positive correlations with both MODIS and SeaWiFS satellite chlorophyll a. Together, the short-lived bromocarbons contribute an average of 8.9 pmol mol−1 (range 5.2–21.4 pmol mol−1) to tropospheric bromine loading, which is similar to that found in previous studies from global sampling networks (Montzka et al., 2011). Statistical tests showed strong Spearman correlations between brominated compounds, suggesting a common source. Log–log plots of CHBr3/CH2Br2 versus CHBr2Cl/CH2Br2 show that both chemical reactions and dilution into the background atmosphere contribute to the composition of these halocarbons at each sampling point. We have used the correlation to make a crude estimate of the regional emissions of CHBr3 and to derive a value of 32 Gg yr−1 for the Southeast (SE) Asian region (10° N–20° S, 90–150° E). Finally, we note that satellite-derived chlorophyll a (chl a) products do not always agree well with in situ measurements, particularly in coastal regions of high turbidity, meaning that satellite chl a may not always be a good proxy for marine productivity.

Hydraulic Fracture Geometry: Fracture Containment in Layered Formations

1982 ◽  
Vol 22 (03) ◽  
pp. 341-349 ◽  
Author(s):  
H.A.M. van Eekelen
Keyword(s):  
Stress Field ◽  
Cross Section ◽  
Horizontal Plane ◽  
Fluid Pressure ◽  
Vertical Plane ◽  
Fracture Propagation ◽  
In Situ Stress ◽  
Design Procedures ◽  
Fracture Height

Abstract One of the main problems in hydraulic fracturing technology is the prediction of fracture height. In particular, the question of what constitutes a barrier to vertical fracture propagation is crucial to the success of field operations. An analysis of hydraulic fracture containment effects has been performed. The main conclusion is that in most cases the fracture will penetrate into the layers adjoining the pay zone, the depth of penetration being determined by the differences in stiffness and in horizontal in-situ stress between the pay zone and the adjoining layers. For the case of a stiffness contrast, an estimate of the penetration depth is given. Introduction Current design procedures for hydraulic fracturing of oil and gas reservoirs are based predominantly on the fracturing theories of Perkins and Kern, Nordgren, and Geertsma and de Klerk. In the model proposed by Perkins and Kern, and improved by Nordgren, the formation stiffness is concentrated in vertical planes perpendicular to the direction of fracture propagation, The fracture cross section in these planes is assumed elliptical, and the stiffness of the formation in the horizontal plane is neglected. In the model proposed by Geertsma and de Klerk, the stiffness of the formation is concentrated in the horizontal plane. The fracture cross section in the vertical plane is assumed rectangular, and the stiffness in the vertical plane is neglected. In both models, the fluid pressure is assumed a function of the distance from the borehole, independent of the transverse coordinates. The theory by Perkins and Kern is more appropriate for long fractures (L/H >1, where L and H are length and height of the fracture), whereas the model by Geertsma and de Klerk is applicable for short fractures, L/H less than 1. The main shortcoming of these fracture-design procedures is that they assume a constant, preassigned fracture height. H. The value of H has a strong influence on the result, for fracture length, fracture width, and proppant transport. Usually, the estimated fracture height is based on assumed "barrier action" of rock layers above and below the pay zone. This situation is rather unsatisfactory. Moreover, if these layers do not contain the fracture, large volumes of fracturing fluid may be lost in fracturing unproductive strata, and communication with unwanted formations may be opened up. Whether an adjacent formation will act as a fracture barrier may depend on a number of factors: differences in in-situ stress, elastic properties, fracture toughness, ductility, and permeability; and the bonding at the interface. We analyze these factors with respect to their relative influence on fracture containment. Differences in in-situ stress and differences in elastic properties affect the global or overall stress field around the fracture, and, hence, the three-dimensional shape of the fracture. This shape, together with the horizontal and vertical fracture propagation rates, determines the fluid pressure distribution in the fracture, which in turn affects the stress field around the fracture. Consequently, the elastic stress field, the fluid pressure field, and the fracture propagation pattern are intimately coupled, which makes the fracture propagation problem a complicated one. Whether at a certain point of the fracture edge the fracture will propagate is determined by the intensity of the stress concentration at that point. This stress concentration depends on the global stress distribution in and around the fracture, but it also is affected directly by local ductility, permeability, and elastic modulus in the tip region. SPEJ P. 341^

scholarly journals Determination of the Origin of Anomalous Eutectic Structures from In Situ Observation of Recalescence Behaviour

2014 ◽  
Vol 790-791 ◽  
pp. 349-354 ◽  
Author(s):  
Andrew M. Mullis ◽  
Caroline R. Clopet ◽  
Robert F. Cochrane
Keyword(s):  
Dendritic Morphology ◽  
Frame Rate ◽  
Two Phase ◽  
Lamellar Eutectic ◽  
Cu Alloy ◽  
Complex Process ◽  
Planar Front ◽  
Eutectic Morphology ◽  
Anomalous Eutectic

A melt encasement (fluxing) method has been used to undercool Ag-Cu alloy at its eutectic composition. The recalescence of the undercooled alloy has been filmed at high frame rate. At low undercooling lamellar eutectic is observed to grow, giving way to a mixed anomalous-lamellar structure at higher undercooling. In situ observation of the spot brightness reveals, as expected, that the lamellar eutectic grows via a planar front mechanism, while the anomalous eutectic grows via a more complex process characterised by a double recalescence. The first recalescence is non-space-filling (dendritic) in character and is followed shortly afterwards by a second recalescence which appears to be of the planar front type. Moreover, the first recalescence event appears to be to a temperature in excess of the equilibrium eutectic temperature. This is strongly suggestive that the anomalous eutectic morphology arises due to the growth and subsequent partial remelting of a dendritic morphology, probably a two-phase (eutectic) dendrite, followed by planar front growth of a lamellar eutectic into the residual liquid.

scholarly journals Bromocarbons in the tropical coastal and open ocean atmosphere during the Prime Expedition Scientific Cruise 2009 (PESC 09)

2014 ◽  
Vol 14 (1) ◽  
pp. 953-984 ◽  
Author(s):  
M. S. Mohd Nadzir ◽  
S. M. Phang ◽  
M. R. Abas ◽  
N. Abdul Rahman ◽  
A. Abu Samah ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Statistical Tests ◽  
Open Ocean ◽  
Common Source ◽  
Sampling Point ◽  
The South ◽  
Coastal Regions ◽  
Chl A ◽  
Strait Of Malacca

Abstract. Atmospheric concentrations of very short-lived species (VSLS) bromocarbons, including CHBr3, CH2Br2, CHCl2Br, CHClBr2, CH2BrCl, were measured in the Strait of Malacca and the South China and Sulu-Sulawesi Seas during a two month research cruise in June/July 2009. The highest bromocarbon concentrations were found in the Strait of Malacca, with smaller enhancements in coastal regions of Northern Borneo. CHBr3 was the most abundant bromocarbon, ranging from 5.2 pmol mol−1 in the Strait of Malacca to 0.94 pmol mol−1 over the open ocean. Other bromocarbons showed lower concentrations, in the range of 0.8–1.3 pmol mol−1 for CH2Br2, 0.1–0.5 pmol mol−1 (CHCl2Br) and 0.1–0.4 pmol mol−1 (CHClBr2). There was no significant correlation between bromocarbons and in situ chlorophyll a. Together the short-lived bromocarbons contribute an average of 8.9 pmol mol−1 (range 5.2–21.4 pmol mol−1) to tropospheric bromine load, which is similar to that found in previous studies (Montzka et al., 2011). Statistical tests showed strong Spearman correlations amongst brominated compounds suggesting a common source. Log-log plots of CHBr3/CH2Br2 vs. CHBr2Cl/CH2Br2 show that both chemical reactions and dilution into the background atmosphere contribute to the composition of these halocarbons at each sampling point. We have used the correlation to make a crude estimate of the regional emissions of CHBr3 and derive a value of 63 Gg yr−1 for the South East (S.E.) Asian region (10° N–20° S, 90–150° E). Finally, we note that satellite-derived chlorophyll a (chl a) products do not always agree well with in situ measurements, particularly in coastal regions of high turbidity, meaning that satellite chl a may not always be a good proxy for marine productivity.

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