4 research outputs found
ORMIR_XCT: A Python package for high resolution peripheral quantitative computed tomography image processing
High resolution peripheral quantitative computed tomography (HR-pQCT) is an
imaging technique capable of imaging trabecular bone in-vivo. HR-pQCT has a
wide range of applications, primarily focused on bone to improve our
understanding of musculoskeletal diseases, assess epidemiological associations,
and evaluate the effects of pharmaceutical interventions. Processing HR-pQCT
images has largely been supported using the scanner manufacturer scripting
language (Image Processing Language, IPL, Scanco Medical). However, by
expanding image processing workflows outside of the scanner manufacturer
software environment, users have the flexibility to apply more advanced
mathematical techniques and leverage modern software packages to improve image
processing. The ORMIR_XCT Python package was developed to reimplement some
existing IPL workflows and provide an open and reproducible package allowing
for the development of advanced HR-pQCT data processing workflows
State observer-based data assimilation: a PID control-inspired observer in the pressure equation
Pressure-Field Extraction from Lagrangian Flow Measurements
As a follow-up to a previous proof-of-principle study, a novel Lagrangian pressure-extraction technique is analytically evaluated and
experimentally validated. This technique employs a Poisson solver to extract the instantaneous pressure field on a network connecting
scattered Lagrangian data. The technique is analytically evaluated using the semi-three-dimensional Taylor-Green vortex, and experimentally
validated using flow data obtained for the case of a free-falling, index-matched sphere at Re = 2100. The experimental data was collected
using a four-camera particle tracking velocimetry measurement system, and processed using the recently-developed Shake-The-Box
algorithm. In the analytical evaluation, it is found that the Lagrangian technique out-performs the standard Eulerian technique when
Dirichlet boundary conditions are enforced. However, the Lagrangian technique suffers when Neumann boundary conditions are enforced.
In order to validate the experimental results, the surface pressure on the sphere is compared to results from literature, and is found to be
in agreement. Based on the extracted pressure fields, the pressure-drag coefficient of the sphere is calculated, and the resulting estimate
compares favourably with the expected value from literature. It is concluded that there is a clear advantage in using the proposed Lagrangian
technique compared to interpolating Lagrangian flow data to a grid, and that further investigation into Lagrangian analysis techniques is
merited
Pressure-field extraction from Lagrangian flow measurements: first experiences with 4D-PTV data
As a follow-up to a previous proof-of-principle study, a novel Lagrangian pressure-extraction technique is analytically evaluated, and experimentally validated using dense 4D-PTV data. The technique is analytically evaluated using the semi-three-dimensional Taylor–Green vortex, and it is found that the Lagrangian technique out-performs the standard Eulerian technique when Dirichlet boundary conditions are enforced. However, the Lagrangian technique produces worse estimates of the pressure field when Neumann boundary conditions are enforced on boundaries with strong pressure gradients. The technique is experimentally validated using flow data obtained for the case of a free-falling, index-matched sphere at Re = 2100. The experimental data were collected using a four-camera particle tracking velocimetry measurement system, and processed using 4D-PTV. The pressure field is then extracted using both the Eulerian and Lagrangian techniques, and the resulting pressure fields are compared. Qualitatively, the pressure fields agree; however, quantitative differences are found with respect to the magnitude of the pressure minima on the side of the sphere. Finally, the pressuredrag coefficient is estimated using each technique, and the two techniques are found to be in very close agreement. A comparison to a reference value from literature confirms that the drag coefficient estimates are reasonable, demonstrating the validity of the technique