scholarly journals Hydraulic and Mechanical Impacts of Pore Space Alterations within a Sandstone Quantified by a Flow Velocity-Dependent Precipitation Approach

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3100 ◽  
Author(s):  
Maria Wetzel ◽  
Thomas Kempka ◽  
Michael Kühn
Keyword(s):  
Flow Velocity ◽  
Power Law ◽  
Elastic Moduli ◽  
Rock Properties ◽  
Local Flow ◽  
Mineral Growth ◽  
Macro Scale ◽  
Elastic Rock ◽  
The Impact ◽  
Flow Velocities

Geochemical processes change the microstructure of rocks and thereby affect their physical behaviour at the macro scale. A micro-computer tomography (micro-CT) scan of a typical reservoir sandstone is used to numerically examine the impact of three spatial alteration patterns on pore morphology, permeability and elastic moduli by correlating precipitation with the local flow velocity magnitude. The results demonstrate that the location of mineral growth strongly affects the permeability decrease with variations by up to four orders in magnitude. Precipitation in regions of high flow velocities is characterised by a predominant clogging of pore throats and a drastic permeability reduction, which can be roughly described by the power law relation with an exponent of 20. A continuous alteration of the pore structure by uniform mineral growth reduces the permeability comparable to the power law with an exponent of four or the Kozeny–Carman relation. Preferential precipitation in regions of low flow velocities predominantly affects smaller throats and pores with a minor impact on the flow regime, where the permeability decrease is considerably below that calculated by the power law with an exponent of two. Despite their complete distinctive impact on hydraulics, the spatial precipitation patterns only slightly affect the increase in elastic rock properties with differences by up to 6.3% between the investigated scenarios. Hence, an adequate characterisation of the spatial precipitation pattern is crucial to quantify changes in hydraulic rock properties, whereas the present study shows that its impact on elastic rock parameters is limited. The calculated relations between porosity and permeability, as well as elastic moduli can be applied for upscaling micro-scale findings to reservoir-scale models to improve their predictive capabilities, what is of paramount importance for a sustainable utilisation of the geological subsurface.

scholarly journals Mechanism Underlying Flow Velocity and Its Corresponding Influence on the Growth of Euglena gracilis, a Dominant Bloom Species in Reservoirs

2019 ◽  
Vol 16 (23) ◽  
pp. 4641
Author(s):  
Yi Tan ◽  
Jia Li ◽  
Linglei Zhang ◽  
Min Chen ◽  
Yaowen Zhang ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Euglena Gracilis ◽  
Environmental Changes ◽  
Algal Species ◽  
Physiological Mechanisms ◽  
Algae Growth ◽  
The Impact ◽  
Stress Hysteresis ◽  
Static Flow ◽  
Flow Velocities

The effects of hydrodynamics on algae growth have received considerable attention, and flow velocity is one of the most frequently discussed factors. For Euglena gracilis, which aggregates resources and is highly resistant to environmental changes, the mechanism underlying the impact of flow velocity on its growth is poorly understood. Experiments were conducted to examine the response of algae growth to different velocities, and several enzymes were tested to determine their physiological mechanisms. Significant differences in the growth of E. gracilis were found at different flow velocities, and this phenomenon is unique compared to the growth of other algal species. With increasing flow velocity and time, the growth of E. gracilis is gradually inhibited. In particular, we found that the pioneer enzyme is peroxidase (POD) and that the main antioxidant enzyme is catalase (CAT) when E. gracilis experiences flow velocity stress. Hysteresis between total phosphorus (TP) consumption and alkaline phosphatase (AKP) synthesis was observed. Under experimental control conditions, the results indicate that flow velocities above 0.1 m/s may inhibit growth and that E. gracilis prefers a relatively slow or even static flow velocity, and this finding could be beneficial for the control of E. gracilis blooms.

High Resolution Particle Image Velocimetry and CH-PLIF Measurements and Analysis of a Shear Layer Stabilized Flame

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
C. W. Foley ◽  
I. Chterev ◽  
J. Seitzman ◽  
T. Lieuwen
Keyword(s):  
Particle Image Velocimetry ◽  
High Resolution ◽  
Shear Layer ◽  
Flow Velocity ◽  
Particle Image ◽  
Flame Stabilization ◽  
Flow Conditions ◽  
Local Flow ◽  
Image Velocimetry ◽  
Flow Velocities

Understanding the mechanisms and physics of flame stabilization and blowoff of premixed flames is critical toward the design of high velocity combustion devices. In the high bulk flow velocity situation typical of practical combustors, the flame anchors in shear layers where the local flow velocities are much lower. Within the shear layer, fluid strain deformation rates are very high and the flame can be subjected to significant stretch levels. The main goal of this work was to characterize the flow and stretch conditions that a premixed flame experiences in a practical combustor geometry and to compare these values to calculated extinction values. High resolution, simultaneous particle image velocimetry (PIV) and planar laser induced fluorescence of CH radicals (CH-PLIF) measurements are used to capture the flame edge and near-field stabilization region. When approaching lean limit extinction conditions, we note characteristic changes in the stretch and flow conditions experienced by the flame. Most notably, the flame becomes less critically stretched when fuel/air ratio is decreased. However, at these lean conditions, the flame is subject to higher mean flow velocities at the edge, suggesting less favorable flow conditions are present at the attachment point of the flame as blowoff is approached. These measurements suggest that blowoff of the flame from the shear layer is not directly stretch extinction induced, but rather the result of an imbalance between the speed of the flame edge and local tangential flow velocity.

High Resolution PIV and CH-PLIF Measurements and Analysis of a Shear Layer Stabilized Flame

2015 ◽  
Author(s):  
C. W. Foley ◽  
I. Chterev ◽  
J. Seitzman ◽  
T. Lieuwen
Keyword(s):  
High Resolution ◽  
Shear Layer ◽  
Flow Velocity ◽  
Near Field ◽  
Flame Stabilization ◽  
Flow Conditions ◽  
Mean Flow ◽  
Local Flow ◽  
High Bulk ◽  
Flow Velocities

Understanding the mechanisms and physics of flame stabilization and blowoff of premixed flames is critical towards the design of high velocity combustion devices. In the high bulk flow velocity situation typical of practical combustors, the flame anchors in shear layers where the local flow velocities are much lower. Within the shear layer, fluid strain deformation rates are very high and the flame can be subjected to significant stretch levels. The main goal of this work was to characterize the flow and stretch conditions that a premixed flame experiences in a practical combustor geometry and to compare these values to calculated extinction values. High resolution, simultaneous PIV and CH-PLIF measurements are used to capture the flame edge and near-field stabilization region. When approaching lean limit extinction conditions, we note characteristic changes in the stretch and flow conditions experienced by the flame. Most notably, the flame becomes less critically stretched when fuel/air ratio is decreased. However, at these lean conditions, the flame is subject to higher mean flow velocities at the edge, suggesting less favorable flow conditions are present at the attachment point of the flame as blowoff is approached. These measurements suggest that blowoff of the flame from the shear layer is not directly stretch extinction induced, but rather the result of an imbalance between the speed of the flame edge and local tangential flow velocity.

scholarly journals Technical Note: Flow velocity and discharge measurement in rivers using terrestrial and unmanned-aerial-vehicle imagery

2020 ◽  
Vol 24 (3) ◽  
pp. 1429-1445 ◽  
Author(s):  
Anette Eltner ◽  
Hannes Sardemann ◽  
Jens Grundmann
Keyword(s):  
Flow Velocity ◽  
Unmanned Aerial Vehicle ◽  
Cross Section ◽  
Flow Characteristics ◽  
Technical Note ◽  
Surface Flow ◽  
Contactless Measurement ◽  
Aerial Vehicle ◽  
The Impact ◽  
Flow Velocities

Abstract. An automatic workflow to measure surface flow velocities in rivers is introduced, including a Python tool. The method is based on particle-tracking velocimetry (PTV) and comprises an automatic definition of the search area for particles to track. Tracking is performed in the original images. Only the final tracks are geo-referenced, intersecting the image observations with water surface in object space. Detected particles and corresponding feature tracks are filtered considering particle and flow characteristics to mitigate the impact of sun glare and outliers. The method can be applied to different perspectives, including terrestrial and aerial (i.e. unmanned-aerial-vehicle; UAV) imagery. To account for camera movements images can be co-registered in an automatic approach. In addition to velocity estimates, discharge is calculated using the surface velocities and wetted cross section derived from surface models computed with structure-from-motion (SfM) and multi-media photogrammetry. The workflow is tested at two river reaches (paved and natural) in Germany. Reference data are provided by acoustic Doppler current profiler (ADCP) measurements. At the paved river reach, the highest deviations of flow velocity and discharge reach 4 % and 5 %, respectively. At the natural river highest deviations are larger (up to 31 %) due to the irregular cross-section shapes hindering the accurate contrasting of ADCP- and image-based results. The provided tool enables the measurement of surface flow velocities independently of the perspective from which images are acquired. With the contactless measurement, spatially distributed velocity fields can be estimated and river discharge in previously ungauged and unmeasured regions can be calculated, solely requiring some scaling information.

scholarly journals Flow velocity and discharge measurement in rivers using terrestrial and UAV imagery

2019 ◽  
Author(s):  
Anette Eltner ◽  
Hannes Sardemann ◽  
Jens Grundmann
Keyword(s):  
Flow Velocity ◽  
Cross Section ◽  
Flow Characteristics ◽  
Surface Flow ◽  
Spatially Distributed ◽  
Adcp Measurements ◽  
River Reach ◽  
Definition Of ◽  
The Impact ◽  
Flow Velocities

Abstract. An automatic workflow to measure surface flow velocities in rivers is introduced, including a Python tool. The method is based on PTV and comprises an automatic definition of the search area for particles to track. Tracking is performed in the original images. Only the final tracks are geo-referenced, intersecting the image observations with water surface in object space. Detected particles and corresponding feature tracks are filtered considering particle and flow characteristics to mitigate the impact of sun glare and outliers. The method can be applied to different perspectives, including terrestrial and aerial (i.e. UAV) imagery. To account for camera movements images can be co-registered in an automatic approach. In addition to velocity estimates, discharge is calculated using the surface velocities and wetted cross-section derived from surface models computed with structure-from-motion and multi-media photogrammetry. The workflow is tested at two river reaches (paved and natural) in Germany. Reference data is provided by ADCP measurements. At the paved river reach highest deviations of flow velocity and discharge reach 5 % and 4 %, respectively. At the natural river deviations are larger (up to 31 %) due to the irregular cross-section shapes hindering accurate contrasting of ADCP- and image-based results. The provided tool enables the measurement of surface flow velocities independently of the perspective from which images are acquired. With the contact-less measurement spatially distributed velocity fields can be estimated and river discharge in previously ungauged and unmeasured regions can be calculated.

Intraoperative transesophageal assessment of coronary artery flow can predict 5 type myocardial infarction

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
A Zagatina ◽  
M Novikov ◽  
N Zhuravskaya ◽  
V Balakhonov ◽  
S Efremov ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Cardiac Surgery ◽  
Coronary Artery ◽  
Flow Velocity ◽  
Coronary Flow ◽  
Index Number ◽  
Left Main ◽  
Coronary Flow Velocity ◽  
Before And After ◽  
Flow Velocities

Abstract Background Stenosis of a coronary artery results in an increase in flow velocity in the pathologic segment. Effective grafting should decrease the stenotic native coronary velocity according to hemodynamic law. The range of decreased velocity before and after cardiac surgery can hypothetically reflect the effectiveness of a graft. The aim of the study is to determine if measuring coronary flow velocity changes during coronary artery bypass grafting (CABG) can predict intraoperative myocardial infarction. Methods One hundred sixty-six (166) consecutive patients (121 men, 64±9 years old) referred for cardiac surgery, were prospectively included in the study. A standard basic perioperative transesophageal echocardiography (TEE) examination was performed with additional scans of the left main, left anterior descending (LAD), and circumflex (LCx) arteries' proximal segments. Measurements of coronary flow velocities were performed before and after grafting in the same sites of the arteries. The maximal value of cardiac troponin I (cTnI) after CABG and the additive criteria were accounted for in the analysis as it is described in the expert consensus document for Type 5 myocardial infarction (MI) definition. Results One hundred sixty-three patients (98%) had arterial hypertension, 28 patients (17%) had diabetes mellitus, 35 patients (21%) were currently smokers. The feasibility of coronary flow assessment during cardiac operations was 95%. Before grafting, the mean velocity in the left main artery was 91±49 cm/s, in LAD 101±35 cm/s, and in LCx 117±49 cm/s. There was a significant correlation between changes in coronary flow velocities during operation and the value of cTnI (R=0.34, p<0.0001). Ten patients met the criteria for Type 5 MI. There were no differences in age, body mass index, number of coronary arteries with stenoses, frequency of prior MI, ejection fraction or coronary flow velocity before surgery in patients with and without Type 5 MI. The group of patients with Type 5 MI had an increase in native artery velocities during surgery in comparison with patients without MI, who had a significant decrease in coronary flow velocity after grafting (30±48 vs. −10±30 cm/s; p<0.0006). Increases in native coronary velocities greater than 3 cm/s predicted Type 5 MI with 81% accuracy (sensitivity 88%, specificity 70%). Conclusion Coronary flow velocity assessment during cardiac surgery could predict an elevation of cardiac troponins and Type 5 MI. Funding Acknowledgement Type of funding source: None

scholarly journals Sensitivity of Ultrasonic Coda Wave Interferometry to Material Damage—Observations from a Virtual Concrete Lab

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4033
Author(s):  
Claudia Finger ◽  
Leslie Saydak ◽  
Giao Vu ◽  
Jithender J. Timothy ◽  
Günther Meschke ◽  
...  
Keyword(s):  
Elastic Moduli ◽  
Concrete Specimen ◽  
Coda Wave ◽  
Velocity Change ◽  
Damage Scenarios ◽  
Different Types ◽  
Source Signal ◽  
The Impact ◽  
Structural Scale ◽  
Coda Wave Interferometry

Ultrasonic measurements are used in civil engineering for structural health monitoring of concrete infrastructures. The late portion of the ultrasonic wavefield, the coda, is sensitive to small changes in the elastic moduli of the material. Coda Wave Interferometry (CWI) correlates these small changes in the coda with the wavefield recorded in intact, or unperturbed, concrete specimen to reveal the amount of velocity change that occurred. CWI has the potential to detect localized damages and global velocity reductions alike. In this study, the sensitivity of CWI to different types of concrete mesostructures and their damage levels is investigated numerically. Realistic numerical concrete models of concrete specimen are generated, and damage evolution is simulated using the discrete element method. In the virtual concrete lab, the simulated ultrasonic wavefield is propagated from one transducer using a realistic source signal and recorded at a second transducer. Different damage scenarios reveal a different slope in the decorrelation of waveforms with the observed reduction in velocities in the material. Finally, the impact and possible generalizations of the findings are discussed, and recommendations are given for a potential application of CWI in concrete at structural scale.

scholarly journals Searching for energy-resolved quasi-periodic oscillations in AGN

2021 ◽  
Author(s):  
Dominic I Ashton ◽  
Matthew J Middleton
Keyword(s):  
Power Law ◽  
Spectral Component ◽  
Broad Band ◽  
Initial Study ◽  
Periodic Oscillations ◽  
Single Observation ◽  
Curved Space ◽  
Multiple Observations ◽  
Band Noise ◽  
The Impact

Abstract X-ray quasi-periodic oscillations (QPOs) in AGN allow us to probe and understand the nature of accretion in highly curved space-time, yet the most robust form of detection (i.e. repeat detections over multiple observations) has been limited to a single source to-date, with only tentative claims of single observation detections in several others. The association of those established AGN QPOs with a specific spectral component has motivated us to search the XMM-Newton archive and analyse the energy-resolved lightcurves of 38 bright AGN. We apply a conservative false alarm testing routine folding in the uncertainty and covariance of the underlying broad-band noise. We also explore the impact of red-noise leak and the assumption of various different forms (power-law, broken power-law and lorentzians) for the underlying broad-band noise. In this initial study, we report QPO candidates in 6 AGN (7 including one tentative detection in MRK 766) from our sample of 38, which tend to be found at characteristic energies and, in four cases, at the same frequency across at least two observations, indicating they are highly unlikely to be spurious in nature.

The Impact of Rock Properties on Acid Jetting in Carbonate Rocks: An Experimental Study

2016 ◽  
Author(s):  
V. Ndonhong ◽  
E. Belostrino ◽  
D. Zhu ◽  
A. D. Hill ◽  
R. E. Beckham ◽  
...  
Keyword(s):  
Experimental Study ◽  
Carbonate Rocks ◽  
Rock Properties ◽  
The Impact
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