Examination of the Influence of Flight Altitude and Speed on the Efimtsov Model Parameters

Abstract

A flight test was conducted and the data was evaluated in order to investigate the influence of flight altitude and flight speed on the coherence length model by Efimtsov. An underestimation of the measured values by the model was found below a frequency of 1kHz. Above this frequency, the predicted values matched the measured values very well. The Efimtsov ansatz was found to be suitable for the description of coherence length, when the parameters are adapted. Three further analyses were performed: the flight speed was varied with constant altitude, the altitude was varied with constant flight speed, and both speed & altitude were varied together. No considerable variation was measured when the flight speed was varied separately. A small variation was determined at low frequency when the flight altitude was altered separately. When varying the parameters together, a distinct variation was found for the cases of highest speed and altitude. The applicability of the exponential coherence decay was analyzed. The absolute deviation was found to increase with lower frequency. The characteristic of the deviation was found to collapse in different regions with different scaling of the strouhal number.