Back to Search
Start Over
Extracting a mixing parameter from 2D radiographic imaging of variable-density turbulent flow
- Source :
- Physica D: Nonlinear Phenomena. 405:132354
- Publication Year :
- 2020
- Publisher :
- Elsevier BV, 2020.
-
Abstract
- We extract a suitably averaged fluctuating density from the two-dimensional radiographic image of a flow. The X-ray attenuation is given by the Beer–Lambert law which exponentially damps the incident beam intensity by a factor proportional to the density, opacity and thickness of the target. By making reasonable assumptions for the mean density, opacity and effective thickness of the target flow, we estimate the density fluctuation contribution to the attenuation. The extracted density fluctuations averaged across the thickness of the flow in the direction of the beam may be used to form the density–specific-volume correlation b . In a statistical description of variable-density turbulence, b quantifies the degree of mixedness. The ability to extract a measure of mixedness from experimental data would be a powerful tool that could be used in the validation of mix models. The scheme proposed is tested for DNS data computed for variable density buoyancy-driven mixing. We quantify the deficits in the extracted value of b due to target thickness, Atwood number and modeled signal noise. This analysis justifies using the proposed scheme to infer the mix parameter from thin targets at moderate to low Atwood numbers. To illustrate how the scheme might be used in a practical problem, we demonstrate its application to a radiographic image of counter-shear flow obtained from experiments at the National Ignition Facility.
- Subjects :
- Physics
Opacity
Turbulence
Attenuation
Statistical and Nonlinear Physics
Mechanics
Condensed Matter Physics
01 natural sciences
Noise (electronics)
010305 fluids & plasmas
Intensity (physics)
Physics::Fluid Dynamics
Flow (mathematics)
Atwood number
0103 physical sciences
010306 general physics
Mixing (physics)
Subjects
Details
- ISSN :
- 01672789
- Volume :
- 405
- Database :
- OpenAIRE
- Journal :
- Physica D: Nonlinear Phenomena
- Accession number :
- edsair.doi...........384aee5d305c383301ab57e27921621f