<p>Thermal diffusivity is an important material property for understanding and characterizing transient behavior in many heat transfer applications. This study investigates the accuracy and approximations of inverse mathematical models for measuring thermal diffusivity of materials via the widely used Flash Method. High-fidelity simulations of the Flash Method in copper, silicon carbide, silicon, and glass were performed as numerical experiments and included physics such as in-depth absorption, radial conduction, and surface convection. Data from those numerical experiments were used to estimate material thermal diffusivity using seven traditional and new inverse models. Parker’s original model had relative errors <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$\epsilon <5\%$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ϵ</mi> <mo><</mo> <mn>5</mn> <mo>%</mo> </mrow> </math></EquationSource> </InlineEquation> when the approximations it makes were enforced in numerical experiments. Newer models performed well even when experimental restrictions were relaxed. Models that include radial heat conduction were capable of accurately measuring thermal diffusivity (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\epsilon <1\%$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ϵ</mi> <mo><</mo> <mn>1</mn> <mo>%</mo> </mrow> </math></EquationSource> </InlineEquation>) when a Gaussian energy source was used. Models with radial conduction and in-depth material absorption of the laser source could calculate thermal diffusivity for semi-transparent materials such as silicon (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\epsilon <1\%$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ϵ</mi> <mo><</mo> <mn>1</mn> <mo>%</mo> </mrow> </math></EquationSource> </InlineEquation>) and even transparent materials like glass (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\epsilon <10\%$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ϵ</mi> <mo><</mo> <mn>10</mn> <mo>%</mo> </mrow> </math></EquationSource> </InlineEquation>). Convective losses from the material’s front surface had a negligible impact on measurements except for very low thermal diffusivity materials. Using temperatures from many locations of the test material’s surface increased resilience to noise, reducing the distribution of thermal diffusivity measurements by more than an order of magnitude. The models developed in this study could enable a more relaxed Flash Method experimental setup that maintains thermal diffusivity accuracy and extend the utility of the Flash Method to semi-transparent materials.</p>

Analysis of Approximations in Flash Thermal Diffusivity Measurements Using High-Fidelity Simulations

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发表日期：

2026年5月5日

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Tage T. Burnett,
Jakob G. Bates,
Matthew R. Jones,
Christopher R. Dillon,
John Tencer

摘要

Thermal diffusivity is an important material property for understanding and characterizing transient behavior in many heat transfer applications. This study investigates the accuracy and approximations of inverse mathematical models for measuring thermal diffusivity of materials via the widely used Flash Method. High-fidelity simulations of the Flash Method in copper, silicon carbide, silicon, and glass were performed as numerical experiments and included physics such as in-depth absorption, radial conduction, and surface convection. Data from those numerical experiments were used to estimate material thermal diffusivity using seven traditional and new inverse models. Parker’s original model had relative errors $\epsilon <5\%$ $ϵ < 5 %$ when the approximations it makes were enforced in numerical experiments. Newer models performed well even when experimental restrictions were relaxed. Models that include radial heat conduction were capable of accurately measuring thermal diffusivity ( $\epsilon <1\%$ $ϵ < 1 %$ ) when a Gaussian energy source was used. Models with radial conduction and in-depth material absorption of the laser source could calculate thermal diffusivity for semi-transparent materials such as silicon ( $\epsilon <1\%$ $ϵ < 1 %$ ) and even transparent materials like glass ( $\epsilon <10\%$ $ϵ < 10 %$ ). Convective losses from the material’s front surface had a negligible impact on measurements except for very low thermal diffusivity materials. Using temperatures from many locations of the test material’s surface increased resilience to noise, reducing the distribution of thermal diffusivity measurements by more than an order of magnitude. The models developed in this study could enable a more relaxed Flash Method experimental setup that maintains thermal diffusivity accuracy and extend the utility of the Flash Method to semi-transparent materials.