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This article discusses systematic errors of the 6GS-40M calibration machine. This machine was designed at the Central Aerohydrodynamic Institute for the calibration of external and internal six-component strain-gauge balances with a maximum normal force of 40 kN. Based on the requirements of the aerodynamic characteristic errors of aircraft models during their tests in wind tunnels, the error of calibration benches, referred to as half the range of each of the six weight components on the bench, should not exceed 0.05%. A method was developed for the experimental evaluation of the systematic errors of the calibration machine, and such errors were determined. Previously derived analytical expressions for the systematic errors were verified using the obtained error values. We estimated the corrections to the loads set by the 6GS-40M calibration machine to external and internal six-component strain-gauge balances. The correction range was 0.09% to 0.90% for the different components of the balances. The developed experimental determination method of systematic errors may be used for other calibration machines. [ABSTRACT FROM AUTHOR]

Wind tunnel testing of small-scale models using aerodynamic balances is a widely used and valuable methodology, particularly in pivotal sectors as wind energy and aerospace industry. Previous works introduced a novel concept of scalable, external, three-component strain gauge balance, which was further validated showing a remarkable agreement against existing experimental data. However, potential applications involving complex airfoil flow environments, or the examination of passive flow control devices are highly demanding in terms of precision, accuracy and uncertainty. This research presents a complete dataset from extensive measurements and explores different calibration methods to address these challenges. Special effort was placed on providing a detailed description of the methodology to ensure reproducibility, and the distinct requirements of each calibration method have been meticulously considered in a comprehensive comparison. The results lead to significant conclusions, indicating that exact solution linear calibration methods are adequate for some applications when suitable calibration loads are used. Nevertheless, for more advanced applications, third-order least-squares models offer the most accurate results and are thus recommended. Finally, this work identifies potential areas for further research, such as exploring double-sided calibration models and assessing the influence of model mounting on the balance behavior, which could contribute to advances in the field. [Display omitted] ■ Complete measurements performed with a novel balance and a calibration system. ■ Different calibration models studied with emphasis in methodology reproducibility. ■ Exact-solution linear calibration is valid for applications over 40% of the full-scale. ■ Third order least-squares calibration is recommended for advanced applications. [ABSTRACT FROM AUTHOR]

• Non-stationary force and moment vectors are measured using a strain-gauge balance. • The balance is modelled as six, linear, uncoupled SDOF systems. • A dynamic problem was solved for the non-inertial balance coordinate system. • The desired arbitrary load can be determined at any arbitrary moment. • The measuring frequency range of the strain-gauge balance is estimated. A novel method using six-component strain-gauge balances has been proposed to solve an important mechanics problem in aircraft model wind tunnel testing – measuring the non-stationary force and moment vectors. A physical model is at the method's core: the sensitive elements of each balance component are replaced by damped springs. This model measures arbitrary non-stationary loads over the entire frequency range of the balance, including the natural frequency. The problem is solved for the general case of a non-inertial balance coordinate system. The standard deviation of the proposed method for measuring non-stationary loads did not exceed 2.8%. The proposed method solves a second problem – measuring object mass and the positions of its centre of mass and moments of inertia with respect to three mutually perpendicular axes. The method is experimentally verified. An estimation of the frequency range of the strain-gauge balance for measuring non-stationary loads was made using the developed method. [ABSTRACT FROM AUTHOR]

The inertial vibration of the force measurement system (FMS) has a large influence on the force measuring result of aircraft, especially on some tests carried out in high-enthalpy impulse facilities, such as in a shock tunnel. When force tests are conducted in a shock tunnel, the low-frequency vibrations of the FMS and its motion cannot be addressed through digital filtering because of the inertial forces, which are caused by the impact flow during the starting process of the shock tunnel. Therefore, this paper focuses on the dynamic characteristics of the performance of the FMS. A new method—i.e., deep-learning-based single-vector dynamic self-calibration (DL-based SV-DSC) of an impulse FMS, is proposed to increase the accuracy of aerodynamic force measurements in a shock tunnel. A deep-learning technique is used to train the dynamic model of the FMS in this study. Convolutional neural networks with a simple structure are applied to describe the dynamic modeling so that the low-frequency vibration signals are eliminated from the test results of the shock tunnel. By validation of the force test results measured in a shock tunnel, the current trained model can realize intelligent processing of the balance signals of the FMS. Based on this new method of dynamic calibration, the reliability and accuracy of force data processing are well verified.

We present a schematic diagram of the automated calibration stand 6GS-40M intended for calibration of an intra- and out-of-model six-component strain-gauge balance. The basic features of the stand construction are stated and its elastic model is constructed. The main sources of the occurrence of systematic errors in weights are considered. A technique for calculating the movement of the origin of the stand during the calibration of the balance is described. A technique for calculating loads in the Earth coordinate system is described by recording the equation of equilibrium of forces for an arbitrary position of the calibration device in space. [ABSTRACT FROM AUTHOR]

Experiments are performed to study the possibility of decreasing the net drag of a flat plate with the use of streamwise-oriented vertical elements mounted normal to the surface in an incompressible equilibrium turbulent boundary layer. The Reynolds number based on the boundary-layer momentum thickness in the section where the vertical elements are placed is 820. It is demonstrated that vertical large eddy breakup elements with the geometry used do not reduce the drag of a flat plate in the major part of the range of Reynolds numbers Re examined. It is only at extremely low values of Re that a certain gain in the net drag is reached, as compared with the value for a non-modified flow. [ABSTRACT FROM AUTHOR]

The inertial vibration of the force measurement system (FMS) has a large influence on the force measuring result of aircraft, especially on some tests carried out in high-enthalpy impulse facilities, such as in a shock tunnel. When force tests are conducted in a shock tunnel, the low-frequency vibrations of the FMS and its motion cannot be addressed through digital filtering because of the inertial forces, which are caused by the impact flow during the starting process of the shock tunnel. Therefore, this paper focuses on the dynamic characteristics of the performance of the FMS. A new method—i.e., deep-learning-based single-vector dynamic self-calibration (DL-based SV-DSC) of an impulse FMS, is proposed to increase the accuracy of aerodynamic force measurements in a shock tunnel. A deep-learning technique is used to train the dynamic model of the FMS in this study. Convolutional neural networks with a simple structure are applied to describe the dynamic modeling so that the low-frequency vibration signals are eliminated from the test results of the shock tunnel. By validation of the force test results measured in a shock tunnel, the current trained model can realize intelligent processing of the balance signals of the FMS. Based on this new method of dynamic calibration, the reliability and accuracy of force data processing are well verified. [ABSTRACT FROM AUTHOR]