Numerical analysis of 6-DOF independent external balance for subsonic wind tunnel

Abstract

Measurement of aerodynamic forces and moments is very important in the aviation, aeronautical and automotive industries. A force balance is used to measure the aerodynamic load acting on the test model. Previous research on force balance has been primarily conducted through experimental methods, which requires a demonstration of the balance's strength. While, an analytical method can be used to analyze the balance's behavior, they may not consider the impact of material stiffness properties on the calibration matrix's accuracy, which quantifies the light coupling effect. A new study is needed to address these limitations and improve the accuracy of the calibration matrix. The FEA method is used to analyze complex 6DOF (six degrees of freedom) independent external balances with cases of nonlinear static mechanics. This balance model is able to measure lift, drag and side independently and a global calibration matrix has been obtained. Tests were carried out to predict CL, CD, dan Cm of a wing with a NACA 4415 airfoil cross section and compared with the results of the analysis from XFLR5. The prediction results obtained are able to follow the trend curves of CL, CD, dan Cm from XFLR5. The maximum errors in CL, CD, dan Cm are 0.85 %, 2.54 %, and 2.31 %, respectively. The maximum error values occur when Re=163×103. This value is classified as a minor error in aerodynamic measurements.

Keywords

• 6 DOF
• Aerodynamic forces
• Force balance
• FEA
• Independent