EMD Adaptive Filtering and Time-Frquency Analysis for Low Turbulence Intensity
Turbulence intensity is an important flow field parameter in wind tunnel, but variation interference noise cause the measurement of low turbulence intensity much trouble, so that lots of methods were used to process turbulence intensity signal. For purpose of improving measurement precision, an EMD(Empirical Mode Decomposition) adaptive filter is designed and HHT(Hilbert-Huang Transform) time-frquency analysis is used initially for low turbulence intensity. Experiment is carried out in three kinds of wind tunnel, includes a low turbulence wind tunnel, a general low speed wind tunnel and an open jet wind tunnel. The turbulence intensity signal is acquired with hot wire anemometry, the EMD method is compared with traditional methods, includes BPF(Band Pass Filter), ENC(Electronic Noise Correction), HPIA(High Pass Inertia Attenuation Filter). Using the EMD filter, the flow field turbulence intensity in the low turbulence wind tunnel test section is measured and found to be less than 0.05% at speed of 30m/s~100 m/s. Using HHT, the low frequency flow fluctuation signal is found in the open jet wind tunnel. To conclude, method of EMD adaptive filter can be used to control the interference of noise in hot wire signal, which is a practical method for low turbulence intensity digital signal process.
Hot-Wire Measurements in Cryogenic Environment
The hotwire anemometry is a well known measurement technique used in several applications to determine flow velocity and to investigate flow quality. Using this measurement technique in a cryogenic environment is not very common and therefore the knowledge about it is very limited. The European Transonic Windtunnel, as cryogenic high Reynolds number test facility, is establishing the hotwire measurement technique to support flow quality measurements required by future laminar flow test campaigns. The present paper describes the challenges of such a system setup in ETW, its application and presents first results gathered in the pilot facility of the European Transonic Windtunnel. Thereby the main objective of this paper is to give a general overview about the first achieved results and to discuss the different influencing parameters on the hotwire output signal over the complete operational envelope of ETW/PETW.
EL TRATAMIENTO NEOPRAGMATISTA DE LA VERDAD EN RICHARD RORTY NEOPRAGMATIST TREATMENT OF TRUTH IN RICHARD RORTY
Richard Rorty, one of the most influential authors of our time, presents a critique of the philosophical concept of truth as correspondence. The conclusion of Rorty's neopragmatism is that the idea of truth as correspondence between language and facts is ineffective because it no longer works. The neopragmatist conception of truth indicates the only possible uses for the term «truthful,» revolving around the idea of jus - tification. In this article, the neopragmatist notion of truth is presented in order to