An Improved Method for Calibration of X-Probe Hot-wires

An Improved Method for Calibration of X-Probe Hot-wires

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Part of #An Improved Method for Calibration of X-Probe Hot-wires# :

Publishing year : 2007

Conference : The 7th Conference of the Iranian Aerospace Society

Number of pages : 9

Abstract: A new method for finding the direct calibration equation of the X-probes used in the 2-D flow based on the genetic algorithm (GA) is presented. This GA method introduces a new way for the polynomials used as a calibration equation, which makes them most adaptable to the hot-wire data. The polynomials had a predefined fixed form and their coefficients were obtained from the least squared fitting method using QR factorization algorithm. Each of the former methods of direct calibration has proposed a new format for these polynomials to obtain a calibration equation with less value of error in velocity calculation. However, all of the suggested formats in the former methods had some restrictions in their application speed range, and they were also not adaptive to any set of hot-wire data set. For the comparison between the new proposed GA method and the well-known former method in the direct calibration of the 2-D flow that uses one of the most frequent polynomials formats will be explained in this paper (named in this paper as the QR method because of using the QR factorization algorithm), and it will be implemented on a set of experimental hot-wire data. Then the GA method will be presented, using a stochastic algorithm to find the most adaptive format of the polynomial as a calibration equation to the same experimental hot-wire data set. Then a comparison will be made in the velocity calculation error between the two methods (GA & amp; QR). The results show a decrease of up to 10 times in error by the presented GA method relative to the QR method. Furthermore, the GA method shows that the error is small in a large range of velocities (10-100 m / s), while the QR method is limited to a specified range of low velocities, because of the use of a fixed form of polynomial for each set of hot -wire data