| 51. |
- Hang, Trieu, et al.
(författare)
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Natural surface floaters in image-based river surface velocimetry: Insights from a case study
- 2024
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Ingår i: Flow Measurement and Instrumentation. - : Elsevier. - 0955-5986 .- 1873-6998. ; 96
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on utilizing image techniques for river velocity measurement, with a specific emphasis onnatural surface floating patterns. Employing a multi-camera system, we conducted 3D measurements on riversurfaces, including surface velocity and water surface reconstruction. A pattern-based tracking approach hasbeen adopted to improve the performance of image measurements on different types of natural floating tracers.The study employs the following approaches: 3D Lagrangian Pattern Tracking Velocimetry (3D-LPTV), 2DLagrangian Pattern Velocimetry (2D- LPTV), and Large-scale Particle Image Velocimetry (LSPIV), for surfacevelocity estimation. The outcomes revealed that all three approaches yielded consistent results in terms ofaveraged velocity. However, the LSPIV method produced about two times higher uncertainty in measured velocitiescompared to the other methods. A strategy to assess the quality of river surface patterns in velocityestimation is presented. Specifically, the sum of squared interrogation area intensity gradient (SSIAIG) was foundto be strongly correlated with measurement uncertainty. Additionally, a term related to the peak sidelobe ratio(PSR) of the cross-correlation map was found as an effective constraint, ensuring the image-tracking processachieves high reliability. The precision of measurements increases corresponding to the increase of image intensitygradient and PSR.
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| 52. |
- Hang, Trieu
(författare)
-
Performance of image-based velocimetry in river flow – Large Scale PIV and PTV
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- River flow velocity is critical information for hydraulic and hydrological applications. Monitoring flow fields in near-plant waterways and river reach has wide engineering applications insustainable hydropower generation. For instance, exploring eco-hydraulic concerns such as fish migration, pollutant transport, and river erosion and understanding river floating debris are a few examples of practical applications. Due to complicated geometry and large volumes of natural flows, the measurement task using traditional methods (e.g., velocity propellers, acoustic Doppler velocimetry, with acoustic Doppler current profilers) usually requires extensive investigative work. The measurement procedure also requires contact with waterbody, thus avoiding its use in severe flood conditions. Image analysis approach allows the measurement task to capture the surface-water velocity distribution over a large outdoor area. The main objectives of this research are to (1) evaluate the feasibility of employing multiple cameras in a single measuring system to estimate the flow surfacevelocity and (2) improve the capability to use natural floating materials in river flow observations.The properties of the camera system and particle tracking velocimetry (PTV) algorithm were investigated in a laboratory open channel flow measurement before being deployed for field measurements. The in situ camera calibration methods, which correspond to the two measurement situations, were used to mitigate the instability of the camera mechanism and camera geometry. The artificial tracer particles were deployed to seed the flows. Two photogrammetry-based PTV algorithms are presented regarding different types of employed seeding particles. The first algorithm uses the particle tracking method applied for individual particles, whereas the second algorithm employs correlation-based particle clustering tracking for clusters of small-size particles. The outcomes reveal that the method can offer a reliable and accurate assessment of 3D surface velocity.In river surface velocity measurements, flow seeding is unavoidable in some situations where the water flow is clear, and there are no occurrences of floating materials on the surface. This part of the study focuses on the application of this technique for river velocity measurements using natural surfacefloating patterns. The use of a multiple-camera system provides the ability to perform 3D measurements on the river surface, including surface velocimetry and water surface reconstruction. The pattern-based tracking approach is used to adapt the performance of image measurements on different types of naturalfloating tracers. A comparison of pattern-based tracking with particle tracking reveals that these two approaches are consistent. An analysis of the characteristics of floating patterns is performed to understand their influences on standard deviation of measured velocity. Considerations on practicing image velocimetry in river flows are also discussed.
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| 53. |
- Hang, Trieu, et al.
(författare)
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Photogrammetry for Free Surface Flow Velocity Measurement : From Laboratory to Field Measurements
- 2021
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Ingår i: Water. - : MDPI. - 2073-4441. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- This study describes a multi-camera photogrammetric approach to measure the 3D velocityof free surface flow. The properties of the camera system and particle tracking velocimetry (PTV)algorithm were first investigated in a measurement of a laboratory open channel flow to prepare forfield measurements. The in situ camera calibration methods corresponding to the two measurementsituations were applied to mitigate the instability of the camera mechanism and camera geometry.There are two photogrammetry-based PTV algorithms presented in this study regarding differenttypes of surface particles employed on the water flow. While the first algorithm uses the particletracking method applied for individual particles, the second algorithm is based on correlation-basedparticle clustering tracking applied for clusters of small size particles. In the laboratory, referencedata are provided by particle image velocimetry (PIV) and laser Doppler velocimetry (LDV). Thedifferences in velocities measured by photogrammetry and PIV, photogrammetry and LDV are 0.1%and 3.6%, respectively. At a natural river, the change of discharges between two measurement timesis found to be 15%, and the corresponding value reported regarding mass flow through a nearbyhydropower plant is 20%. The outcomes reveal that the method can provide a reliable estimation of3D surface velocity with sufficient accuracy.
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| 54. |
- Hedberg, P. A. Mikael, et al.
(författare)
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Measurements and Simulations of the Flow Distribution in a Down-Scaled Multiple Outlet Spillway with Complex Channel
- 2024
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Ingår i: Water. - : Multidisciplinary Digital Publishing Institute (MDPI). - 2073-4441. ; 16:6
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of mass flow through a three-outlet spillway modeled after a scaled-down spillway were conducted. The inlet and channel leading up to the outlets were placed to lead the water toward the outlet at an angle. With this, measurements of the water level at three locations were recorded by magnetostrictive sensors. The volumetric flow rates for each individual outlet were recorded separately to study the differences between them. Additionally, Acoustic Doppler Velocimetry was used to measure water velocities close to the outlets. The conditions changed were the inlet volume flow rate and the flow distribution was measured at 90, 100, 110, and 200 L per second. Differences between the outlets were mostly within the error margin of the instruments used in the experiments with larger differences shown for the 200 L test. The results produced together with a CAD model of the setup can be used for verification of CFD methods. A simulation with the k-epsilon turbulence model is included and compared to earlier experiments and the new experimental results. Larger differences are seen in the new experiments. Differing inlet conditions are assumed as the principal cause for the differences seen.
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| 55. |
- Hedberg, P. A. Mikael, 1989-, et al.
(författare)
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Numerical modelling of flow in parallel spillways
- 2020
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Ingår i: Proceedings of the 8th IAHR International Symposium on Hydraulic Structures ISHS2020. - : The University of Queensland.
-
Konferensbidrag (refereegranskat)abstract
- Mathematical modelling of single spillways is well documented in literature. For parallel spillways however, there is a lack of documented, verified, and validated cases. Here, in this article, ANSYS-CFX is used to simulate the flow over three parallel ogee-crested spillways. For mesh size verification, a grid convergence study is performed by Richardson extrapolation. The turbulence model chosen for this simulation is the k-ε model and the volume of fluid method is used to simulate the water-air interface. This article details the models ability to accurately predict flow distribution at the spillways, and the water levels. The mesh is kept relatively coarse at the channel inlet with increased mesh density at the spillways. The results are validated against experimental data from Vattenfall AB, R&Ds laboratories. The geometry and boundary conditions of the experiment are tailored for CFD. The flow rate of each spillway is measured separately with high accuracy, and for several different inlet volumetric flows. The simulation results lie within the error estimates of the measuring tools used in the experiments, within ±1%. The volume flow rate differences between the three outlets is very small, within ±1%.
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| 56. |
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| 57. |
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| 58. |
- Hong, S. J., et al.
(författare)
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TMEM106B and CPOX are genetic determinants of cerebrospinal fluid Alzheimer's disease biomarker levels
- 2021
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Ingår i: Alzheimers & Dementia. - : Wiley. - 1552-5260 .- 1552-5279. ; 17:10, s. 1628-1640
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction Neurofilament light (NfL), chitinase-3-like protein 1 (YKL-40), and neurogranin (Ng) are biomarkers for Alzheimer's disease (AD) to monitor axonal damage, astroglial activation, and synaptic degeneration, respectively. Methods We performed genome-wide association studies (GWAS) using DNA and cerebrospinal fluid (CSF) samples from the EMIF-AD Multimodal Biomarker Discovery study for discovery, and the Alzheimer's Disease Neuroimaging Initiative study for validation analyses. GWAS were performed for all three CSF biomarkers using linear regression models adjusting for relevant covariates. Results We identify novel genome-wide significant associations between DNA variants in TMEM106B and CSF levels of NfL, and between CPOX and YKL-40. We confirm previous work suggesting that YKL-40 levels are associated with DNA variants in CHI3L1. Discussion Our study provides important new insights into the genetic architecture underlying interindividual variation in three AD-related CSF biomarkers. In particular, our data shed light on the sequence of events regarding the initiation and progression of neuropathological processes relevant in AD.
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| 59. |
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| 60. |
- Jonsson, Patrick, et al.
(författare)
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Smoothed particle hydrodynamics modeling of hydraulic jumps
- 2011
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Ingår i: Particle-based Methods – Fundamentals and Applications. - Barcelona : International Center for Numerical Methods in Engineering (CIMNE). - 9788489925670 ; , s. 490-501
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study focus on Smoothed Particle Hydrodynamics (SPH) modeling of twodimensional hydraulic jumps in horizontal open channel flows. Insights to the complex dynamics of hydraulic jumps in a generalized test case serves as a knowledgebase for real world applications such as spillway channel flows in hydropower systems. In spillways, the strong energy dissipative mechanism associated with hydraulic jumps is a utilized feature to reduce negative effects of erosion to spillway channel banks and in the old river bed. The SPH-method with its mesh-free Lagrangian formulation and adaptive nature results in a method that handles extremely large deformations and numerous publications using the SPH-method for free-surface flow computations can be found in the literature. Hence, the main objectives with this work are to explore the SPH-methods capabilities to accurately capture the main features of a hydraulic jump and to investigate the influence of the number of particles that represent the system. The geometrical setup consists of an inlet which discharges to a horizontal plane with an attached weir close to the outlet. To investigate the influence of the number of particles that represents the system, three initial interparticle distances were studied, coarse, mid and fine. For all cases it is shown that the SPH-method accurately captures the main features of a hydraulic jump such as the transition between supercritical- and subcritical flow and the dynamics of the highly turbulent roller and the air entrapment process. The latter was captured even though a single phase was modeled only. Comparison of theoretically derived values and numerical results show good agreement for the coarse and mid cases. However, the fine case show oscillating tendencies which might be due to inherent numerical instabilities of the SPH-method or it might show a more physically correct solution. Further validation with experimental results is needed to clarify these issues.
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