We propose a steady-state aerodynamic data-driven method to predict the incompressible flow around airfoils of NACA (National Advisory Committee for Aeronautics) 0012-series. Using the Signed Distance Function (SDF) to parameterize the geometric and flow condition setups, the prediction core of the method is constructed essentially by a consecutive framework of a convolutional neural network (CNN) and a deconvolutional neural network (DCNN). Impact of training parameters on the behavior of the proposed CNN-DCNN model is studied, so that appropriate learning rate, mini-batch size, and random deactivation rate are specified. Tested by “unseen” airfoil geometries and far-field velocities, it is found that the prediction process is three orders of magnitudes faster than a corresponding Computational Fluid Dynamics (CFD) simulation, while relative errors are maintained lower than 1% on most of the sample points. The proposed model manages to capture the essential dynamics of the flow field, as its predictions correspond reasonably with the reconstructed field by proper orthogonal decomposition (POD). The performance and accuracy of the proposed model indicate that the deep learning-based approach has great potential as a robust predictive tool for aerodynamic design and optimization.

Gel fuel potentially combines the advantages of solid fuel and liquid fuel due to its special rheological properties, which have essential impacts on the application of gel fuel in propulsion systems. In this paper, we study the rheological property of organic kerosene gel through a series of measurements on its viscosity as a function of the shear rate, temperature, and shear history. The measured datasets are then fitted with constitutive relationships between the viscosity and shear rate at three different levels: the power law shear-thinning model, the power law dependency on both the temperature and shear rate, and the thixotropic property. It is found that intense pre-shear could exhaust thixotropy and reduce viscosity of the kerosene gel. For the power law shear-thinning model, the consistency index increases with the gellant mass fraction, whereas the power law exponent remains constant. The dependence of viscosity on temperature could be well approximated by an empirical power law relationship. As for the thixotropic property of the kerosene gel, the fitted second-order kinetic model corresponds accurately to the viscosity at different shear rates and shear times. The constitutive models fitted in this work at different levels are consistent with each other and provide useful tools for further applications of organic kerosene gel fuel.

The flow characteristics of shock train in the isolator play an important role in the overall performance of the scramjet. Although several studies have concentrated on understanding this phenomenon in rigid isolators, few works have focused on methods to control it. The current study proposes a new concept shock train control strategy based on the aeroelastic effect of the flexible panel. An in-house developed code was used to solve the compressible Navier–Stokes equations and the geometric nonlinear equations of the panel, where the conventional serial staggered algorithm was adopted for the two-way fluid–structure interaction. Then, we numerically investigated the effect of cavity pressure on the dynamic behavior of the panel, location, and structure of the shock train, separation zone, and performance of the isolator. The results show that the dynamic response of the panel subjected to the different cavity pressure can be characterized into three states: static stability state, high-frequency second-order limit cycle flutter state, and multi-frequency periodic flutter state. The panel flutter mainly presents an approximately second-mode pattern for the limit cycle flutter state and a first-order vibration mode for the periodic flutter state. With increasing cavity pressure, the average value of shock-train head location moves downstream significantly, while the general trend of separation zone length on top and bottom walls becomes smaller. The flexible panel with the high-frequency second-order limit cycle flutter state can increase the total pressure recovery coefficient with the smaller side load and outlet flow distortion, reduce the averaged separation length, and make the shock-train head move downstream. This is due to the isentropic compression and expansion waves induced by the vibration and deformation of the flexible panel.

Pasty rocket engines have broad application prospects in the aerospace field. To study the internal ballistic characteristics of the pasty propellant rocket engine, the burning surface change model of pasty propellant was built. The calculation program was developed to calculate the pressure evolution in the combustion chamber, and the experiment was carried out based on a pasty propellant rocket test system. The data calculated by the program are in good agreement with the experiment, the error of the initial pressure peak is only 4.02%, and the internal ballistic characteristics of the rocket engine at each stage were analyzed detailly. The effects of ignition delay time, transport pipeline structure, free volume of the combustion chamber, mass flow rate, and flow velocity of the pasty propellant on internal ballistic characteristics of the pasty propellant rocket engine are investigated. The results indicate that when the ignition delay time increases, the pressure rises faster and the initial pressure peak increases obviously. The transport pipe diameter changes from 11.3 mm to 7.4 mm, and the initial combustion time and residual propellant combustion time decreased by 41.3% and 36.0%. The reduction of the free volume of the combustion chamber can reduce the initial pressure peak and the time to reach the equilibrium pressure. The initial pressure spike and equilibrium pressure rise with the increase of the pasty propellant flow velocity. While the ignition transient decreased with the increase of the pasty propellant flow velocity. The internal ballistic properties can be improved by reducing the ignition delay time, the diameter of the transport pipeline, and the free volume of the combustion chamber, or by increasing the mass flow rate of the pasty propellant rocket engine.