Aerodynamic forces and moments are among the most important data required for flight vehicle performance simulation and design, and such data can be obtained through wind tunnel model tests among other methods. The work described here relates to wind tunnel tests based on relativity and similarity principles. Test models of the studied objects were fabricated in accordance with similarity criteria and connected to a balance and support system fixed on a motion‐controlling mechanism for changing or controlling the attitude angles of the model. This has been installed in the test section of a wind tunnel. When gas flows under test conditions through the wind tunnel section, aerodynamic forces and moments exerted on the model are transferred to the balance and converted into electrical signals. These signals are filtered and amplified by a signal‐conditioning system, sampled by a data acquisition system and then processed to obtain the aerodynamic forces and moments. Other parameters such as total and static pressures, total temperature, and model attitude angle are measured by a pressure transducer, temperature sensor, and angle sensor, respectively. After synthesizing all the measurements, the non‐dimensional aerodynamic force and moment coefficients are obtained and then used for vehicle design and simulation.

The purpose of this work is to improve the efficiency of sample selection with recursive method for wall-bounded turbulent flows. In the proposed physics-assisted recursive method, the flow field is divided into several sub-regions along the wall distance. Since the distributions of the flow variables have certain similarity along the wall normal direction, fast clustering of similar data can be achieved, which paves the way for the rapid elimination of redundant data. Then the recursive method is used for sample selection in each sub-region. The effectiveness of the proposed method is investigated through several cases. The results show that the proposed method has good convergence and grid independence, and improves the computational efficiency of the recursive method for sample selection. Since the amount of training data is reduced, the time consumption of model training is decreased. In addition, it is demonstrated that sample selection can also be helpful to achieve more balanced model performance by changing the distribution of training data.

A fast and reliable turbine design method is necessary in aeroengine development practice. As Q3D time-marching method iteration process can be time consuming and unstable, a novel S2 stream surface approximation approach coupled with flow tangential condition is proposed to reduce the computation requirement. The surface approximation uses a quadratic function of axial coordinate x to formulate distribution of circumferential coordinate θ . The flow tangential condition inherently represents inviscid blade force effect, and the formulation of inviscid blade force is not needed. A corresponding personal Q3D turbine computer code was developed, which was suitable for both design and analysis applications. The Q3D design method solves Euler’s equation through third-order Godunov’s scheme with TVD property in finite volume method. Semi-implicit Crank-Nicolson’s temporal scheme is implemented. Profile, secondary, and tip clearance energy loss models are added to predict viscous losses. Blade row exit swirl is required as the convergence target for Q3D design. A two-stage turbine and a single-stage high-pressure turbine were designed and analyzed by the Q3D method. Viscous 3D CFD was utilized to check design performances. The results showed that the Q3D method could finish a design case within 1 min. At design point, Q3D mass flow rate error was no more than 1.25%, expansion ratio error was no less than -0.022, and isentropic efficiency error was no more than 0.37 percentage points. The Q3D design method is fast and accurate. The stream surface approximation approach is suitable for Q3D design and analysis.

To visualize the flow in the test section of an indraft supersonic wind tunnel in the University of Glasgow as long as possible, a background-oriented schlieren system was built up preliminarily. A MATLAB program based on a random dot algorithm developed in this study provides a fully customizable tool to generate background patterns with different sizes and dot densities. Background patterns produced by the in-house developed program then can be printed by a common ink-jet printer. To enhance the signal-noise ratio of the measurement system, white reflective film sheets, or semi-transparent paper can be employed. The correlation algorithm base on fast Fourier transform that is also applicable for PIV was chosen to process background oriented schlieren images. A validation test was performed to visualize the flow structure around a Pitot tube at M = 2.0. The experimental result proves that the BOS system established in this study is capable of visualizing the supersonic flow structure around the Pitot tube and sensitive enough to reveal weak density changes produced by the boundary layer, expansion waves, and weak oblique shock waves. Next, the current BOS system will be improved further by increasing the intensity of light sources to shorten the exposure time, using new cameras with better spatial resolution, and optimizing the background pattern.

Direct numerical simulations are carried out to identify the effects of shock impingement on the behavior of bump flow at free-stream Mach number of 2.25. Two cosine-shaped bump cases, with and without an impinging oblique shock at an angle of 33.2{degree sign}, are compared. The shock impingement exhibits a remarkable influence on the pattern of the shock system and on the size of the separation region. Spectral analysis finds that low-frequency unsteadiness is significantly enhanced by the impingement interaction, and the proper orthogonal decomposition highlights the low-frequency breathing motion of the separation bubble, which is accurately reconstructed using only the first ten low-order modes. Downstream of the bump, the Reynolds stress components and the turbulence kinetic energy both exhibit a general amplification, with the peaks reoccurring at outer wall-normal locations. Turbulent kinetic energy budget analysis shows the greatly increased production in the outer layer which is balanced by turbulent transport and dissipation. Anisotropy-invariant map analysis identifies enhanced isotropic turbulence in the vicinity of the bump, which is qualitatively modified into a two-component axisymmetric state around the reattachment point. In addition, the mean skin friction decomposition suggests that the shock impingement has little influence on the predominant contribution of turbulence kinetic energy production, apart from the spatial growth dominance at the bump summit in the absence of the impinging shock. Interestingly, a scale-decomposed analysis quantitatively demonstrates that the contributions of small-scale structures are attenuated, but those of large-scale ones are relatively increased, with a contribution of more than 80% with shock impingement.