Force and moment Measurements
Force and moment measurement is very essential at given speed range in order to aerodynamically characterize any flying vehicle. The three forces and three moments viz; Lift, Drag, side force, pitching moment, yawing moment and rolling moment are the parameters studied in force and moment measurement tests. The overall forces, moments and location of centre of pressure can be measured/ derived from these tests. At initial design phase it is extremely important to know the force and moment information in order to refine the design parameters and to arrive at optimized vehicle design. The forces and moments are measured in model axes/body axes, which are then transformed to wind axes to give lift, drag and moments.
The models for testing are designed and fabricated in-house. Extremely experienced and dedicated design and fabrication groups realize the models. Generally high strength steel and Aluminium alloys are used to fabricate the model. In NTAF-NAL, six component internal strain gauge balances are used to measure force and moments on wind tunnel models. The balance is calibrated frequently and the matrix of coefficients is generated which is used for deriving the forces and moments during wind tunnel testing. Calibration and wind tunnel data reduction is done using state-of-the-art Global Regression Method. The acquisition and processing of the data takes place within minutes after completion of the blowdown. Specially designed balances are used to measure hinge moment other small component loads.