FINITE-ELEMENT MODELING OF A 3-COMPONENT FORCE BALANCE FOR HYPERSONICFLOWS

Measurement of aerodynamic forces on a model craft exposed to hypervel ocity how in a shock tunnel must be performed during the period of ste ady flow which may be less than a millisecond. Measurement of drag has previously been achieved in this time frame at The University of Quee nsland, by deconvolution of strain signals measured in a sting attache d to the model craft. This procedure has been extended to include meas urement of lift and pitching moment. Finite element modelling has play ed a major role in the design of the device used to achieve this. Limi tations of finite element predictions of strain signals are discussed, as is the applicability of two- and three-dimensional models in the d esign process. Finite element modelling has enabled questions to be an swered that cannot easily be investigated experimentally: in particula r, establishing what strain signals can be successfully processed to r ecover the input loading and what physical configurations produce acce ptable strain signals. As well, the sensitivity of the procedure to th e time history of loading, the distribution of loading and the flexibi lity of the model is studied. The chosen configuration for lift measur ement involves mounting the craft to the sting by means of symmetrical triangulated bars, in which the axial strains are measured. Experimen tal tests on this support arrangement are compared to the finite eleme nt simulations.