Gas Kinetic Scheme Coupled with High-Speed Modifications for Hypersonic Transition Flow Simulations

The issue of hypersonic boundary layer transition prediction is a critical aerodynamic concern that must be addressed during the aerodynamic design process of high-speed vehicles. In this context, we propose an advanced mesoscopic method that couples the gas kinetic scheme (GKS) with the Langtry-Menter transition model, including its three high-speed modification methods, tailored for accurate predictions of high-speed transition flows. The new method incorporates the turbulent kinetic energy term into the Maxwellian velocity distribution function, and it couples the effects of high-speed modifications on turbulent kinetic energy within the computational framework of the GKS solver. This integration elevates both the transition model and its high-speed enhancements to the mesoscopic level, enhancing the method's predictive capability. The GKS-coupled mesoscopic method is validated through a series of test cases, including supersonic flat plate simulation, multiple hypersonic cone cases, the Hypersonic International Flight Research Experimentation (HIFiRE)-1 flight test, and the HIFiRE-5 case. The computational results obtained from these cases exhibit favorable agreement with experimental data. In comparison with the conventional Godunov method, the new approach encompasses a broader range of physical mechanisms, yielding computational results that closely align with the true physical phenomena and marking a notable elevation in computational fidelity and accuracy. This innovative method potentially satisfies the compelling demand for developing a precise and rapid method for predicting hypersonic boundary layer transition, which can be readily used in engineering applications.

Ultra-Tough Waterborne Polyurethane-Based Graft-Copolymerized Piezoresistive Composite Designed for Rehabilitation Training Monitoring Pressure Sensors

Effective training is crucial for patients who need rehabilitation for achieving optimal recovery and reducing complications. Herein, a wireless rehabilitation training monitoring band with a highly sensitive pressure sensor is proposed and designed. It utilizes polyaniline@waterborne polyurethane (PANI@WPU) as a piezoresistive composite material, which is prepared via the in situ grafting polymerization of PANI on the WPU surface. WPU is designed and synthesized with tunable glass transition temperatures ranging from -60 to 0 °C. Dipentaerythritol (Di-PE) and ureidopyrimidinone (UPy) groups are introduced, endowing the material with good tensile strength (14.2 MPa), toughness (62 MJ-1 m-3 ), and great elasticity (low permanent deformation: 2%). Di-PE and UPy enhance the mechanical properties of WPU by increasing the cross-linking density and crystallinity. Combining the toughness of WPU and the high-density microstructure derived by hot embossing technology, the pressure sensor exhibits high sensitivity (168.1 kPa-1 ), fast response time (32 ms), and excellent stability (10 000 cycles with 3.5% decay). In addition, the rehabilitation training monitoring band is equipped with a wireless Bluetooth module, which can be easily applied to monitor the rehabilitation training effect of patients using an applet. Therefore, this work has the potential to significantly broaden the application of WPU-based pressure sensors for rehabilitation monitoring.