Showing papers by "National Aerospace Laboratories published in 1990"

Limits of adaptation, residual interferences

Abstract: Methods of determining linear residual wall interference appear to be well established theoretically; however they need to be validated, for example by comparative studies of test data on the same model in different adaptive-wall wind tunnels as well as in passive, ventilated-wall tunnels. The GARTEur CAST 7 and the CAST 10/DOA 2 investigations are excellent examples of such comparative studies. Results to date in both one-variable and two-variable methods for nonlinear wall interference indicate that a great deal more research and validation are required. The status in 2D flow is advanced over that in 3D flow as is the case generally with adaptive-wall development. Nevertheless, it is now well established that for transonic testing with extensive supercritical flow present, significant wall interference is likely to exist in conventional ventilated test sections. Consequently, residual correction procedures require further development hand-in-hand with further adaptive-wall development.

Identification Experiments for a Large Space Structure

Abstract: This paper considers the modal parameter identification problem for an LSS (Large Space Structure) from measured input-output data. The selection of setting parameters for identification, such as the sampling rate and identification model order, has great influence on the identification accuracy. This paper proposes a new identification method which uses decimated input-output data. The decimation consists of two parts, first the input-output data are filtered by low-pass filters, and then resampled by the lower sampling rate. The elastic modes can be identified accurately by proper choice of the cut-off frequency of the filter. In the proposed identification method, the model order is determined by the frequency domain criterion, that is, the flatness of the identification residual sequence. The effectiveness of the proposed identification method is shown by identification experiments which were carried out by using a groundbased test model.