Thin flat balances for testing thin delta wings at hypersonic speeds

Abstract

This paper concerns the design and development of two special novel thin internal strain gauge balances for testing thin slab delta wings at hypersonic speeds. Of the two balances, one is a thin three-component balance and the other is a thin six-component balance. Unlike the conventional balances, which are circular in cross section, the balances discussed here are flat and have rectangular cross sections. Here, the design philosophy and the metallic architecture of these balances are discussed in detail. This paper is divided into three parts wherein the first part deals with the thin three-component balance the second part addresses the thin six-component balance and, in the third part, typical results obtained using these two balances are presented. The thin three-component balance has a thickness of 2.5 mm and can be housed inside a wing as thin as 6 mm. Because of its thinness, the axial output exhibited non-linear interaction from the normal force loading. Hence, combined loading is performed. In order to deduce the second-order coefficients, a new method has been proposed and a comparison with the existing method shows that this is better than the previous method. This balance has been used to generate aerodynamic data on thin slab delta wings with and without lee-side balance housing bodies. In this way, it is demonstrated that the lee-side bodies do interfere even when they come into the aerodynamic shadow of the wing. The thin six-component balance has a thickness of 4 mm and can be housed inside an 8 mm thick wing. Although this balance is also thin, it exhibited excellent linearity in all the bridges. In spite of this, it is subjected to several possible combinations of combined loading and the `work back' loads are calculated using the linear coefficients. The work back loads agree very well with the applied loads. Hence, linear coefficients have been used for the purpose of data reduction. The effects of flap deflection on the aerodynamic characteristics of thin slab delta wings have been studied using this balance. All the experiments were conducted at Mach 8.2 and a Reynolds number of 2.13×106.