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Irene Ndindabahizi

Bio: Irene Ndindabahizi is an academic researcher from Royal Military Academy. The author has contributed to research in topics: Muzzle flash & Schlieren. The author has an hindex of 1, co-authored 1 publications receiving 1 citations.

Papers
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TL;DR: The implemented experimental high-speed BOS setup has demonstrated its ability to capture clearly the salient features of the precursor and the propellant gas flow fields and their interactions, confirming the BOS capability to visualize complex density flow fields.
Abstract: Several experimental and numerical studies on muzzle blast and flow fields have been performed. However, due to the extremely short duration and the spatiotemporal evolution of these flows, experimental quantitative techniques are limited. As a consequence, the number of validated numerical calculations is limited as well. On the other hand, despite the development of computer models that have succeeded in predicting the measured pressure and velocity, they show unrealistic temperatures and densities. Therefore, temperature and/or density measurements are required to validate these codes, thus the motivation of this research. The present paper focuses on the development of a density-sensitive and non-intrusive measurement technique and the implementation of a quantitative flow visualization method based on Background-Oriented Schlieren (BOS) combined with a high-speed camera. In BOS, the experimental setup of conventional Schlieren (mirrors, lenses, and knife-edge) is replaced by a background pattern and a single digital camera. The muzzle flow fields and the flow field around a 5.56-mm projectile in flight were successfully visualized. Indeed, the implemented experimental high-speed BOS setup has demonstrated its ability to capture clearly the salient features of the precursor and the propellant gas flow fields and their interactions. The captured structures such as vortex, barrel shock, Mach disk, and blast wave show a good agreement with that issued from a realized conventional Schlieren setup and the bibliography, confirming the BOS capability to visualize complex density flow fields.

9 citations


Cited by
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TL;DR: In this paper , the authors present insights into the establishment of a laboratory scale technique to generate a combined blast loading and single or multiple projectile impacts on a target, where steel ball bearings are used to simulate the projected fragments.
Abstract: This work is a part of a larger research effort to better understand the combined effect of the blast wave and fragment impacts following the detonation of a shrapnel bomb. It is known that the time interval Δt, which represents the difference in arrival time between the blast wave front and the fragment at the position of a given target object, has a significant influence on its response mode. This paper presents insights into the establishment of a laboratory scale technique to generate a combined blast loading and single or multiple projectile impacts on a target. The objective of the setup is to control the time interval Δt to a certain extent so that the different response modes of the tested structures can be investigated. In order to reduce the complexity associated with the random nature of the shrapnel, steel ball bearings are used to simulate the projected fragments. They are embedded in a solid explosive charge, which is detonated at the entrance of an explosive driven shock tube. The experimental work demonstrates that it is possible to orient the path of a single projectile inside the tube when aiming at a target positioned at its exit. The setup guarantees the generation of a well-controlled planar blast wave characterized by its peak pressure, impulse and blast wave arrival time at the exit of the tube. The influence of the mass of the charge and the diameter of the projectile on its velocity study shows that for the same charge mass, the time interval increases with increasing projectile diameter. The experiments are numerically simulated based on an Eulerian approach using the LS-DYNA finite element software. The computational model allows to reveal details about the projectile flight characteristics inside the tube. Both the experimental and numerical data show the influence of the charge and projectile parameters on the time interval.

3 citations

Journal ArticleDOI
TL;DR: In this paper , the applicability of the Particle Image Velocimetry (PIV) technique to provide accurate velocity measurements in the challenging environment of the propellant flow of a .300 blackout weapon was evaluated.

3 citations

Journal ArticleDOI
TL;DR: In this paper , a new method for the reconstruction of three-dimensional axisymmetric refractive index fields is presented, which takes advantage of the bi-sensitivity quality of BOS to gain more accuracy in the reconstructed fields.
Abstract: Background-oriented schlieren (BOS) is an optical visualization technique that reconstructs a whole-field flow based on its density gradient. Thanks to the cost-effectiveness of its optical setup and its unlimited field of view, BOS has become an attractive technique for laboratory and large-scale experiments. In BOS, the reconstruction of the refractive index field involves various mathematical calculations, which depend on the flow geometry. In this context, the present study presents a new method for the reconstruction of three-dimensional axisymmetric refractive index fields. The proposed method takes advantage of the bi-sensitivity quality of BOS to gain more accuracy in the reconstructed fields. We demonstrate the method’s precision and robustness against experimental noise throughout a synthetic axisymmetric refraction index field. The application of this new approach is not restricted to the BOS technique but can be extended to several other measurement techniques such as moiré deflectometry, laser speckle photography, and rainbow schlieren.

1 citations

Journal ArticleDOI
TL;DR: In this article , a new method for the reconstruction of three-dimensional axisymmetric refractive index fields is presented, which takes advantage of the bi-sensitivity quality of BOS to gain more accuracy in the reconstructed fields.
Abstract: Background-oriented schlieren (BOS) is an optical visualization technique that reconstructs a whole-field flow based on its density gradient. Thanks to the cost-effectiveness of its optical setup and its unlimited field of view, BOS has become an attractive technique for laboratory and large-scale experiments. In BOS, the reconstruction of the refractive index field involves various mathematical calculations, which depend on the flow geometry. In this context, the present study presents a new method for the reconstruction of three-dimensional axisymmetric refractive index fields. The proposed method takes advantage of the bi-sensitivity quality of BOS to gain more accuracy in the reconstructed fields. We demonstrate the method’s precision and robustness against experimental noise throughout a synthetic axisymmetric refraction index field. The application of this new approach is not restricted to the BOS technique but can be extended to several other measurement techniques such as moiré deflectometry, laser speckle photography, and rainbow schlieren.

1 citations

Journal ArticleDOI
TL;DR: In this paper , a detailed approach for an a posteriori estimation of uncertainty when using background-oriented schlieren (BOS) measurements to reconstruct the refractive index/density field is presented.
Abstract: Background-oriented schlieren (BOS) technique is a density-based optical measurement technique. BOS measurement is similar to particle image velocimetry (PIV) ones in terms of experiments design and the computation of the displacements. However, in the BOS technique, the reconstruction of the refractive index field involves further mathematical calculations, which depend on the flow geometry, such as Poisson solver, Abel inversion, algebraic reconstruction technique, and filtered back-projection. This lengthy combination of experimental measurements, cross-correlation evaluation, and mathematical computation complicates the uncertainty quantification of the reconstructed field. In this study, we present a detailed approach for an a posteriori estimation of uncertainty when using BOS measurements to reconstruct the refractive index/density field. The proposed framework is based on the Monte Carlo simulation (MCS) method and can consider all kinds of sources of error, ranging from experimental measurements to those arising from image processing. The key features of this methodology are its capacity to handle different mathematical reconstruction procedures and the ease with which it can integrate additional sources of error. We demonstrate this method first by using synthetic images and a Poisson solver with mixed boundary conditions in a 2D domain. The accuracy of the proposed approach is assessed by comparing analytical and MCS results. Then, the modular nature of the proposed framework is experimentally demonstrated using a combination of Abel inversion and inverse gradient techniques to reconstruct a 3D axisymmetric density field around a transonic projectile in free-flight. The results are compared with computational fluid dynamics (CFD) and show high levels of agreement with only limited discrepancies, which are attributed to the space-filtering effect within cross-correlation resulting from shock waves.