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.