Component Force Balance Research Articles

Static Calibration and Dynamic Behaviour of a Six-Component Force Balance for Variable Pressure Water Tunnel Facilities

The presented six component force balance is a novel design used for many of the force measurements on hydrofoils and other bodies in the University of Tasmania’s cavitation tunnel. This balance is a versatile piece of equipment, the distribution of its six load cells gives it a high degree of sensitivity and stiffness in all directions. The accuracy of the balance in operating conditions has yet to be defined and its use for investigations of low frequency fluid-structure interactions warrants an analysis of its dynamic properties. This paper outlines a critical analysis of the balances calibration methodologies and its measurement uncertainties. A dynamic vibration model was built and validated with finite element modelling and experiment to give a prediction of the force balances natural frequencies and how they change with different test article mass and added masses. These results provide confidence in the data produced by this device and guide future experimental investigations into fluid structure interactions.

EFFECT OF HEIGHT AND ORIENTATION OF INTERFERING BUILDINGS ON WIND LOADS ON TALL BUILDINGS

The research work presented in this paper investigates the effect of interference on wind loads on a tall building (instrumented building) having rectangular cross-sectional shape due to the presence of two interfering buildings close to the instrumented building. The effect of interference on the instrumented building is studied with the variation of height and relative orientation of the interfering buildings with respect to the instrumented building. Wind tunnel experiments are undertaken using five component force balance load cell and the results are reported in the form of X-Y plots. The effect of interference in both shielding as well as enhancing the wind load on the instrumented building, is seen to increase with the increase in the height of the interfering building. Negative drag force is also observed in few cases where shielded part of the instrumented building is large. Value of torsion on the instrumented building is observed to be as high as ten times of that in the isolated case.

Design of Artificial Neuro-fuzzy Based Methodology for Six Component Force Balance

A blunt cone model of 600 apex angle and 150 flare with internally mountable accelerometer balance has been considered for the present investigation on six component force balance. The finite element method (FEM) has been incorporated at predetermined angles of the applied force to obtain multiple accelerations in three spatial directions so as to replicate a six component force balance system. A novel intelligent soft computing technique, Artificial Neuro-Fuzzy Inference System (ANFIS) has been implemented for accurate prediction of the magnitude and trend of aerodynamic forces and moments from the transient acceleration history. The same method is also used to validate the universal approximation nature of the impulse force by accurate prediction of the hat and ramp forces from the training of the impulse forces. Furthermore, a training algorithm is deduced so as to predict the force and moment magnitude for the three and single component force balance from the six component training data. Henceforth, novelty of this study involves in deduction of a universal training method and successful implementation of it to predict short duration transient force and moment histories.

Design, modelling and analysis of a six component force balance for hypervelocity wind tunnel testing

A combination of modelling and analysis techniques was used to design a six component force balance. The balance was designed specifically for the measurement of impulsive aerodynamic forces and moments characteristic of hypervelocity shock tunnel testing using the stress wave force measurement technique. Aerodynamic modelling was used to estimate the magnitude and distribution of forces and finite element modelling to determine the mechanical response of proposed balance designs. Simulation of balance performance was based on aerodynamic loads and mechanical responses using convolution techniques. Deconvolution was then used to assess balance performance and to guide further design modifications leading to the final balance design.

Force measurements in low density hypersonic air flows

In recent years several wind tunnels have been designed to operate at a pressure level of approximately 0.1 mmHg absolute pressure. The problems associated with the measurement of low aerodynamic pressures of this order has been the subject of many publications. The problem of measuring forces, both lift and drag, has not received as much attention. This paper describes a single component force balance capable of measuring either lift or drag forces up to 100 g. The balance, by the use of various quartz springs, may be used for the measurement of forces as low as 100 mg with a sensitivity of 0.1 mg.