Terahertz Radar Inversion for Range-Resolved Solids Concentration Profiling in Gas--Solid Flows
Abstract
A stable inversion method is developed to reconstruct millimeter-scale solids-concentration profiles in particulate suspensions from monostatic sub-terahertz frequency-modulated continuous-wave (FMCW) radar measurements. In industrial particulate flows, cumulative attenuation renders the direct inversion of the path-integrated volume-scattering radar equation ill-conditioned. The method resolves this by an ensemble-averaged Mie-scattering closure coupled to a stable backward-integration scheme, yielding an analytical solution for the range-resolved solids concentration without case-specific parameter fitting against reference concentration measurements. The required range-dependent system response is determined by absolute near- and far-field calibration via external substitution with an electrically large metallic sphere. The method was evaluated against solids-volume-fraction estimates derived from differential-pressure measurements in a 3.1 m-tall circulating fluidized-bed riser operated with ambient air and copper powder (median diameter 32.6 μm, density 8920 kg m−3). The radar-derived and pressure-derived profiles agreed well across three superficial gas velocities producing distinct axial solids distributions, and the radar indicates sensitivity down to solids volume fractions of order 10−6.
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BibTeX
@misc{jepsen2026terahertz,
title = {{Terahertz Radar Inversion for Range-Resolved Solids Concentration Profiling in Gas--Solid Flows}},
author = {Philip Kjaer Jepsen and Albert Monteith and Diana Carolina Guío-Pérez and Lars Ulander and Tomas Bryllert and Henrik Ström and David Pallarès},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.18567},
eprint = {2609.18567},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.18567},
}
RIS
TY - UNPB
TI - Terahertz Radar Inversion for Range-Resolved Solids Concentration Profiling in Gas--Solid Flows
AU - Philip Kjaer Jepsen
AU - Albert Monteith
AU - Diana Carolina Guío-Pérez
AU - Lars Ulander
AU - Tomas Bryllert
AU - Henrik Ström
AU - David Pallarès
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.18567
UR - https://arxiv.org/abs/2609.18567
AB - A stable inversion method is developed to reconstruct millimeter-scale solids-concentration profiles in particulate suspensions from monostatic sub-terahertz frequency-modulated continuous-wave (FMCW) radar measurements. In industrial particulate flows, cumulative attenuation renders the direct inversion of the path-integrated volume-scattering radar equation ill-conditioned. The method resolves this by an ensemble-averaged Mie-scattering closure coupled to a stable backward-integration scheme, yielding an analytical solution for the range-resolved solids concentration without case-specific parameter fitting against reference concentration measurements. The required range-dependent system response is determined by absolute near- and far-field calibration via external substitution with an electrically large metallic sphere. The method was evaluated against solids-volume-fraction estimates derived from differential-pressure measurements in a 3.1 m-tall circulating fluidized-bed riser operated with ambient air and copper powder (median diameter 32.6 μm, density 8920 kg m^−3). The radar-derived and pressure-derived profiles agreed well across three superficial gas velocities producing distinct axial solids distributions, and the radar indicates sensitivity down to solids volume fractions of order 10^−6.
ER -