Light extinction tomography for measurement of ice crystals and other small particles

Inventors

Bencic, Timothy J. • Rohler, David P. • Fagan, Amy F. • Izen, Steven H. • Maniyedath, Arjun K.

Assignees

PLEXAR ASSOCIATES Inc

Abstract

A tomography duct for wind tunnels includes a plurality of light sources and sensors displaced around a support structure. The light sources are cycled and sensor measurements are made from sensors opposite the light sources. Tomographic algorithms are used to determine an extinction map from the sensor measurements. The extinction map provides details about particles in a cross-section of the air flow through the tomography duct.

Core Innovation

A wind-tunnel tomography system positions a geometric simulation component in a tomography duct of a wind tunnel and characterizes airflow in a flow cross-section. A plurality of electromagnetic emitters displaced along the tomography duct illuminate the duct in an illumination pattern, while sensor elements displaced along the tomography duct receive light that is at least partially extinguished by one or more features of the geometric simulation component.

The method measures extinguished light intensity from one or more selected sensor elements for each of a plurality of illumination cycles in the illumination pattern. Using a tomography algorithm, an extinction map is reconstructed based at least in part on the plurality of measurements of extinguished light intensity, and the reconstructed extinction map is compared with an expected extinction map for the geometric simulation component.

Tomography algorithm parameters are adjusted based at least in part on the comparison between the reconstructed extinction map and the expected extinction map. Documented embodiments describe iterative reconstruction, filtered backprojection, truncated singular value decomposition (TSVD), and diffraction tomographic reconstruction, along with cross-shaped and ring-shaped geometric simulation components including concentric rings.

The document also describes calibration using dark current and unextinguished measurements and includes real-time updates for monitoring an ice/water spray and deriving particle characteristics such as ice/water density.

Claims Coverage

The independent claim identifies seven core inventive actions, yielding reconstruction of an extinction map from wind-tunnel tomography measurements and parameter adjustment by comparison with an expected extinction map. Dependent claims further specify cross-shaped and/or ring-shaped geometric simulation components and add iterative reconstruction and comparison.

Overall, the claim set centers on wind-tunnel tomography that reconstructs an extinction map from extinguished light intensity measured across illumination cycles, compares the reconstructed map to an expected extinction map generated for a geometric simulation component, and adjusts tomography algorithm parameters accordingly. Dependent claims specify cross-shaped and ring-shaped geometric simulation components, including concentric rings, and iterative reconstructing and comparing for parameter adjustment.

Stated Advantages

Documented Applications