A low-computational-cost inverse heat transfer technique for convective heat transfer measurements in hypersonic flows

Abstract

The measurement of the convective wall heat flux in hypersonic flows may be particularly challenging in the presence of high-temperature gradients and when using high-thermal-conductivity materials. In this case, the solution of multidimensional problems is necessary, but it considerably increases the computational cost. In this paper, a low-computational-cost inverse data reduction technique is presented. It uses a recursive least-squares approach in combination with the trust-region-reflective algorithm as optimization procedure. The computational cost is reduced by performing the discrete Fourier transform on the discrete convective heat flux function and by identifying the most relevant coefficients as objects of the optimization algorithm. In the paper, the technique is validated by means of both synthetic data, built in order to reproduce physical conditions, and experimental data, carried out in the Hypersonic Test Facility Delft at Mach 7.5 on two wind tunnel models having different thermal properties

Experimental characterization of the hypersonic flow around a cuboid

“…Following filtering, the IR video is stabilised to remove the effect of model and sting vibration during tunnel start-up and shut-down. The image registration algorithm used to stabilise the IR video is the single-step discrete Fourier transform approach proposed by Guizar-Sicairos et al (2008), which has already been used successfully on IR videos (Avallone et al 2015). This algorithm calculates the displacement between two images to a sub-pixel accuracy by computing the upsampled cross-correlation between an image and a reference image by the fast Fourier transform.…”

“…In the context of measuring heat fluxes using IRT, the heat flux to the surface is estimated by considering the evolution of the surface temperature. IHCPs, while offering maximum flexibility in heat flux calculations (Avallone et al 2015) also have their disadvantages, namely their significant complexity and computational cost. In addition to this, they are ill-posed problems as their solutions are not unique, meaning their solutions are extremely sensitive to small changes in input data (Ozisik and Orlande 2000).…”

Experimental method to quantify the efficiency of the first two operational stages of nanosecond dielectric barrier discharge plasma actuators

“…The wall heat flux distribution is computed from the surface temperature signal by solving a onedimensional IHTP based on the semi-infinite slab model coupled with a least squares approach [25,32]. Starting from the temperature dynamics of the barrier, the heat flux (q) is evaluated by minimizing the difference between the computed temperature drop (eq.…”

“…This results in an increase of the impedance mismatch between the actuator and the feeding system, increasing the energy losses, and reducing efficiency. From a thermodynamic point of view, an increase in thickness will also result in an increase in thermal energy loss due to thermal diffusion within the material and tangential conduction (the second factor might be taken into account solving a two dimensional IHTP [32]). Therefore, a thicker barrier corresponds to a lower efficiency.…”

Thermal Protection System and Thermal Management for Combined-Cycle Engine: Review and Prospects

“…An algorithm that conducts a Fourier transform of the heat flux function is entirely possible to be applied to measure the combustion chamber temperature. In a study by Avallone [158], an algorithm was proposed to measure heat conduction in hypersonic flow environments at low computational costs . Combining the recursive least squares method [159] and the trust-region-reflective algorithm [160], this algorithm efficiently reduces the computational amount by conducting discrete Fourier transform [161] of the discrete heat flow function and optimizing the correlation coefficient.…”