Impulse Force Balance for Ultrashort Duration Hypersonic Test Facilities

P Singh,H Hosseini,V Menezes,K J Irimpan

doi:10.1155/2015/803253

P Singh, H Hosseini + Show 2 more

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https://doi.org/10.1155/2015/803253

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Abstract

This paper presents the measurement of side force, pitching, and yawing moments on a model, using an accelerometer force balance, in a short duration hypersonic shock tunnel. The test model is a blunt-nosed, flapped delta wing, mounted on a support sting through a force balance. The flexible rubber bushes constituting the balance allow the model to float freely on the sting during the test. The accelerometers were located in the model to record accelerations in the directions of interest. The model was tested in shock tunnel at Mach 8 at different angles of incidence with the freestream. Dynamic calibration of the test assembly was carried out for the acquisition of impulse response functions for the above components of force and moments, using an impulse hammer. The convolution technique was applied to derive the impulse response functions. The accelerometer outputs from the model in the hypersonic freestream were processed using the respective impulse response functions to derive the unknown aerodynamic force and moments. The newly adopted convolution technique has been found very effective for data reduction from accelerometer force balances developed for shock tunnel applications.

Highlights

Impulse mode of operation is common in most of the groundbased hypersonic test facilities as the requirement on energy and thermal survival would exceed the system capabilities otherwise
The aerodynamic forces and moments on a test model in a hypersonic shock tunnel can be measured by surface pressure measurement [5] and visual [6] techniques, but the output of the force balances is free of the concerns of geometrical complexity, spatial resolution, and time-dependency
The impulse response functions obtained through the calibration procedure were operated on the above output signals of the system in their frequency domains, as described by (2), and were transformed back into the time domain by Inverse Fast Fourier Transform (IFFT) as force-time and moment-time histories, which were the unknown input to the system from the hypersonic freestream in the tunnel

Summary

Introduction

Impulse mode of operation is common in most of the groundbased hypersonic test facilities as the requirement on energy and thermal survival would exceed the system capabilities otherwise. The aerodynamic forces and moments on a test model in a hypersonic shock tunnel can be measured by surface pressure measurement [5] and visual [6] techniques, but the output of the force balances is free of the concerns of geometrical complexity, spatial resolution, and time-dependency. In this backdrop, we developed an accelerometer-based force balance to measure forces and moments on hypersonic lifting models in shock tunnels. The acquired impulse response function of the system was used to derive the forces and moments under unknown conditions, such as in a hypersonic freestream in the shock tunnel

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