An accelerometer balance system for measurement of aerodynamic force coefficients over blunt bodies in a hypersonic shock tunnel

Abstract

A miniature three-component accelerometer balance system for measuring the fundamental aerodynamic force coefficients over blunt bodies has been designed, fabricated and tested in the Indian Institute of Science hypersonic shock tunnel HST2 at a nominal Mach number of 5.75. The model and the balance system are supported by rubber bushes, thereby ensuring unrestrained free-floating conditions of the model in the test section during the flow duration. Exhaustive axisymmetric finite-element simulations are carried out to select appropriate rubber bushes and materials for the model and the balance system. The internally mountable accelerometer balance is used to measure the drag, lift and pitching moment coefficients for a 60 • apex angle blunt cone within the effective tunnel test time of 800 µs. The measured aerodynamic force coefficients match very well with the theoretical values predicted using modified Newtonian theory at moderate specific enthalpy levels of the test gas.

Design and analysis of a flat accelerometer-based force balance system for shock tunnel testing

“…In fact, this was found to be the optimum quality that can be used for shock tunnel applications. This is also one of the most important conclusions reported in the previous literature [13]. However, as one goes for shock tunnel testing of larger models, the residual stresses in the flexible mounts and alignment problem may complicate the design paradigm.…”

“…rubber bushes). The concept of finite-element analysis for the accelerometer balance system was first introduced by Sahoo et al [12,13] to study the dynamic behavior of the integrated model-balance system. However, the analysis was limited to simple axi-symmetric blunt-cone configuration.…”

“…The design of a three-component accelerometer balance system for blunt cone configurations was earlier reported by the authors for two-dimensional axi-symmetric case [12,13]. The stainless steel balance with two annular rubber bushes as supports over the sting, one drag accelerometer and two differential lift accelerometers was fitted within a blunt cone (without flare) made off aluminum.…”

Shock tunnel testing of a Mach 6 hypersonic waverider

“…The waverider part was assigned the properties of Duralumin and the rubber bush was specified as an isotropic material with E = 3 MPa [5]. Four-node tetrahedral elements were used to build the finite element model.…”

A gasdynamic gun driven by gaseous detonation

“…2 The higher the natural frequencies, the better the justification for the neglected acceleration compensation. For such test conditions, many researchers proposed several special balances to measure the aerodynamic forces in the impulse facilities, that is, accelerometer balance, [5][6][7] stress-wave force balance, [8][9][10] free-flight measurement technique, [11][12][13][14][15][16] and compensated balance. 17 Owing to the very short test time, however, the mature technology was undeveloped for the force measurements in a shock tunnel.…”