Transient Temperature Data Analysis for a Supersonic Flight Test

Abstract

Determination of transient surface heat flux from the temperature data is one of the traditional techniques applied in many engineering applications. With respect to high speed flight experiments, the time scale of measured temperature data is usually very small (∼ms). So, one-dimensional heat conduction analysis is expensively used to infer surface heating rates on the body. For an analytical modeling, it is necessary to obtain a closed form solution from experimentally measured temperature data. In this paper, a temperature data obtained from a nickel film sensor during a supersonic flight test is considered for analysis. Three different curve fitting techniques are used to recover the temperature history of real time flight, namely, piecewise linear fit, polynomial fitting, and cubic-spline method. A one-dimensional transient heat transfer modeling is used to infer surface heating rates from the closed form temperature solutions. Results obtained from these analysis are compared and it is seen that peak surface heat flux values match very closely for polynomial and cubic-spline fitting of temperature data. But, the piecewise linear fit of temperature data underpredicts the peak surface heat flux value by four times from its counterparts.

Heat flux measurement analysis from thin film gauge in convective heat transfer mode

“…It has been proposed by several researchers that the substrate body dimension of TFG is to be chosen in such a way to consider it as semi-infinite body along with the assumptions that measured surface temperature at stagnation point (point ‘M’ as shown in Figure 7) on thin film is same as that of substrate surface and heat transfer through rear end of the substrate is negligible, while substrate thermal properties throughout the experiment remains constant (Schultz and Jones, 1973; Taler, 1996). In order to predict the heat flux at stagnation point ‘M’, the instantaneous surface temperature data recorded at ‘M’ is fed to the simplified expression of the solution of one dimensional heat conduction problem for semi-infinite body as shown in equation (3) (Sahoo and Kumar, 2016; Sahoo and Peetala, 2010; Schultz and Jones, 1973, Taler, 1996). The quantity within square root outside the bracket in numerator in equation (3) is collectively termed as effective thermal product of the substrate.…”

“…A number of existing numerical techniques are available to evaluate the value of heat flux from equation (3). It has been observed that trapezoidal and Simpson rule of approximation methods have limitations owing to the existence of singularity condition at the upper limit, t=τ, while piecewise linear approximation method evades this problem and results obtained through this method are more accurate with less computational time (Cook, 1970; Sahoo and Peetala, 2010). In the present work cubic spline method is used for discretization purpose to deduce the heat flux values from transient temperature histories.…”

“…A number of researchers have explored the development of traditional TFG for various applications with modification and improvement in measurement technique (Holmberg and Diller, 1995; Kumar et al, 2011; Sahoo and Peetala, 2010). The TFG has nowadays gained the promising future in the field of thin film measurement technique for transient temperature measurement and surface heat flux prediction.…”

Conjugate Heat Transfer Analysis for a Finite Thickness Cylinder in a Hypersonic Flow

“…These investigations for small time scales of a few milliseconds (ms), can be related to the experimental testing for heat transfer measurements in ground‐based impulse facilities (e.g., shock tunnels) because the typical test duration of these facilities ranges from a few hundred microseconds to a couple of milliseconds . In such facilities, the most preferred measurement technique is the prediction of surface heat flux from temperature signals with appropriate heat conduction modeling . These short duration temperature signals are acquired from thin film sensors consisting of a sensing element and substrate material.…”

“…Accordingly, the gauge is treated as thin film or thick film gauge for which heat transfer models will be different . The Conventional CFD studies reported in the open literature do highlight the methods for determination of wall heat flux and support the experimental investigations . However, such methods have limitation on the prediction of wall temperature and heat flux that are claimed to be accurate for short duration time scale of measurements.…”