Background-Oriented Schlieren Velocimetry of Helium Coolant Flow in Additively Manufactured Channels

Cody S. Wiggins; Yuqiao Fan; Chris Crawford

doi:10.1109/TPS.2026.3680839

Background-Oriented Schlieren Velocimetry of Helium Coolant Flow in Additively Manufactured Channels

Cody S. Wiggins
, Yuqiao Fan
, Chris Crawford

Blanket and Fuel Cycle

Research output: Contribution to journal › Article › peer-review

Abstract

High-pressure helium gas cooling is an attractive solution for thermal management of the fusion blanket first wall, as this coolant is chemically and neutronically inert and separable from hydrogenic species. However, due to the low thermal mass of helium, geometric optimization of these channels is required to provide sufficient cooling at manageable flow rates and pumping burdens. Increasingly, analysis and optimization of these coolant channels rely on computational fluid dynamics (CFD) simulations, and these require relevant experimental data for turbulence model validation. Toward this end, a high-pressure helium gas flow visualization system has been employed to image the flow of helium in flow channels with one-sided heating, mimicking the blanket first wall environment. Flow of helium at 4 MPa pressure and flow rates up to 68 g/s (Reynolds number 57000) is supplied to rectangular channel test sections, with uniform heating applied to the bottom wall of the channel at heat fluxes varied between roughly 50 and 130 kW/m2. A high-speed camera is used to image index of refraction (IOR) gradients in the fluid via background-oriented schlieren (BOS), and temperature and pressure instrumentation are used to characterize thermal-hydraulic performance of each channel. Cross correlation of time-resolved BOS images is then used to calculate time-averaged 2-D helium velocity fields. Flow in additively manufactured (AM) channels is examined in this manner, including both featureless channels and those containing baffling as a heat transfer enhancement. The flow distribution seen in the featureless case differs significantly from that seen in prior simulations, whereas the flow in the baffled case shows the predicted behavior of flow forced along the heated wall. This augmented flow distribution is seen to increase the heat transfer coefficient in the baffled test section. Strategies are discussed for ongoing and future validation of these simulations, with the aim of model deployment for blanket cooling design and optimization.

Original language	English
Pages (from-to)	2530-2536
Number of pages	7
Journal	IEEE Transactions on Plasma Science
Volume	54
Issue number	6
DOIs	https://doi.org/10.1109/TPS.2026.3680839
State	Published - Jun 1 2026

Funding

This work was supported by the UT-Battelle, LLC, under Grant DE-AC05-00OR22725. The review of this article was arranged by Senior Editor M. Kovari. Chase Joslin and Keith Carver of ORNL's Manufacturing Science Division provided invaluable assistance in designing and printing additively manufactured (AM) test articles. Tracy Xu provided supplemental simulations in support of ongoing helium flow tests. The U. S. government retains, and the publisher, by accepting the article for publication, acknowledges that the U. S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U. S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy. gov/downloads/doe-public-access-plan). Received 29 August 2025; revised 12 March 2026; accepted 30 March 2026. This work was supported by the UT-Battelle, LLC, under Grant DE-AC05-00OR22725. The review of this article was arranged by Senior Editor M. Kovari. (Corresponding author: Cody S. Wiggins.) The authors are with the Fusion Energy Division, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA (e-mail: [email protected]). Color versions of one or more figures in this article are available at https://doi.org/10.1109/TPS.2026.3680839. Digital Object Identifier 10.1109/TPS.2026.3680839

Keywords

Additive manufacturing
background-oriented schlieren (BOS)
breeding blanket
flow visualization
fusion engineering
helium cooling

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10.1109/TPS.2026.3680839

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@article{548939324b05405098d5679e5118238c,

title = "Background-Oriented Schlieren Velocimetry of Helium Coolant Flow in Additively Manufactured Channels",

abstract = "High-pressure helium gas cooling is an attractive solution for thermal management of the fusion blanket first wall, as this coolant is chemically and neutronically inert and separable from hydrogenic species. However, due to the low thermal mass of helium, geometric optimization of these channels is required to provide sufficient cooling at manageable flow rates and pumping burdens. Increasingly, analysis and optimization of these coolant channels rely on computational fluid dynamics (CFD) simulations, and these require relevant experimental data for turbulence model validation. Toward this end, a high-pressure helium gas flow visualization system has been employed to image the flow of helium in flow channels with one-sided heating, mimicking the blanket first wall environment. Flow of helium at 4 MPa pressure and flow rates up to 68 g/s (Reynolds number 57000) is supplied to rectangular channel test sections, with uniform heating applied to the bottom wall of the channel at heat fluxes varied between roughly 50 and 130 kW/m2. A high-speed camera is used to image index of refraction (IOR) gradients in the fluid via background-oriented schlieren (BOS), and temperature and pressure instrumentation are used to characterize thermal-hydraulic performance of each channel. Cross correlation of time-resolved BOS images is then used to calculate time-averaged 2-D helium velocity fields. Flow in additively manufactured (AM) channels is examined in this manner, including both featureless channels and those containing baffling as a heat transfer enhancement. The flow distribution seen in the featureless case differs significantly from that seen in prior simulations, whereas the flow in the baffled case shows the predicted behavior of flow forced along the heated wall. This augmented flow distribution is seen to increase the heat transfer coefficient in the baffled test section. Strategies are discussed for ongoing and future validation of these simulations, with the aim of model deployment for blanket cooling design and optimization.",

keywords = "Additive manufacturing, background-oriented schlieren (BOS), breeding blanket, flow visualization, fusion engineering, helium cooling",

author = "Wiggins, \{Cody S.\} and Yuqiao Fan and Chris Crawford",

note = "Publisher Copyright: {\textcopyright} 2026 IEEE.",

year = "2026",

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doi = "10.1109/TPS.2026.3680839",

language = "English",

volume = "54",

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T1 - Background-Oriented Schlieren Velocimetry of Helium Coolant Flow in Additively Manufactured Channels

AU - Wiggins, Cody S.

AU - Fan, Yuqiao

AU - Crawford, Chris

PY - 2026/6/1

Y1 - 2026/6/1

N2 - High-pressure helium gas cooling is an attractive solution for thermal management of the fusion blanket first wall, as this coolant is chemically and neutronically inert and separable from hydrogenic species. However, due to the low thermal mass of helium, geometric optimization of these channels is required to provide sufficient cooling at manageable flow rates and pumping burdens. Increasingly, analysis and optimization of these coolant channels rely on computational fluid dynamics (CFD) simulations, and these require relevant experimental data for turbulence model validation. Toward this end, a high-pressure helium gas flow visualization system has been employed to image the flow of helium in flow channels with one-sided heating, mimicking the blanket first wall environment. Flow of helium at 4 MPa pressure and flow rates up to 68 g/s (Reynolds number 57000) is supplied to rectangular channel test sections, with uniform heating applied to the bottom wall of the channel at heat fluxes varied between roughly 50 and 130 kW/m2. A high-speed camera is used to image index of refraction (IOR) gradients in the fluid via background-oriented schlieren (BOS), and temperature and pressure instrumentation are used to characterize thermal-hydraulic performance of each channel. Cross correlation of time-resolved BOS images is then used to calculate time-averaged 2-D helium velocity fields. Flow in additively manufactured (AM) channels is examined in this manner, including both featureless channels and those containing baffling as a heat transfer enhancement. The flow distribution seen in the featureless case differs significantly from that seen in prior simulations, whereas the flow in the baffled case shows the predicted behavior of flow forced along the heated wall. This augmented flow distribution is seen to increase the heat transfer coefficient in the baffled test section. Strategies are discussed for ongoing and future validation of these simulations, with the aim of model deployment for blanket cooling design and optimization.

AB - High-pressure helium gas cooling is an attractive solution for thermal management of the fusion blanket first wall, as this coolant is chemically and neutronically inert and separable from hydrogenic species. However, due to the low thermal mass of helium, geometric optimization of these channels is required to provide sufficient cooling at manageable flow rates and pumping burdens. Increasingly, analysis and optimization of these coolant channels rely on computational fluid dynamics (CFD) simulations, and these require relevant experimental data for turbulence model validation. Toward this end, a high-pressure helium gas flow visualization system has been employed to image the flow of helium in flow channels with one-sided heating, mimicking the blanket first wall environment. Flow of helium at 4 MPa pressure and flow rates up to 68 g/s (Reynolds number 57000) is supplied to rectangular channel test sections, with uniform heating applied to the bottom wall of the channel at heat fluxes varied between roughly 50 and 130 kW/m2. A high-speed camera is used to image index of refraction (IOR) gradients in the fluid via background-oriented schlieren (BOS), and temperature and pressure instrumentation are used to characterize thermal-hydraulic performance of each channel. Cross correlation of time-resolved BOS images is then used to calculate time-averaged 2-D helium velocity fields. Flow in additively manufactured (AM) channels is examined in this manner, including both featureless channels and those containing baffling as a heat transfer enhancement. The flow distribution seen in the featureless case differs significantly from that seen in prior simulations, whereas the flow in the baffled case shows the predicted behavior of flow forced along the heated wall. This augmented flow distribution is seen to increase the heat transfer coefficient in the baffled test section. Strategies are discussed for ongoing and future validation of these simulations, with the aim of model deployment for blanket cooling design and optimization.

KW - Additive manufacturing

KW - background-oriented schlieren (BOS)

KW - breeding blanket

KW - flow visualization

KW - fusion engineering

KW - helium cooling

UR - https://www.scopus.com/pages/publications/105036717396

U2 - 10.1109/TPS.2026.3680839

DO - 10.1109/TPS.2026.3680839

M3 - Article

AN - SCOPUS:105036717396

SN - 0093-3813

VL - 54

SP - 2530

EP - 2536

JO - IEEE Transactions on Plasma Science

JF - IEEE Transactions on Plasma Science

IS - 6

ER -

Background-Oriented Schlieren Velocimetry of Helium Coolant Flow in Additively Manufactured Channels

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