Study on the separation in the shock wave/boundary layer interaction induced by a curved fin

The multi-medium fluid flow around a supersonic sea-skimming flight is featured by the detached/attached shock wave, separation shock wave, and the reflected wave from the free surface. The complex wave structure and high nonlinearity pose a great challenge in accurate and stable numerical simulation. In this paper, a numerical model based on the high-order Runge–Kutta discontinuous Galerkin method is established to resolve the above problem. Based on the fact that the dimensionless vertical velocity is small, the air–water interface is linearized and a modified flux scheme is proposed to simplify the treatment of the multi-medium problem. A block-based adaptive mesh refinement scheme is adopted to capture the complex wave structure with the new nodes projected on the curved boundary. Finally, the numerical simulation of supersonic sea-skimming flight of the National Advisory Committee for Aeronautics 0012 airfoil is carried out by using the above-mentioned simplified numerical model based on the scheme of partition solution. The results show that the model can perform high-resolution simulations for the shock wave structure in various scenes. Meanwhile, the Mach number and distance between the airfoil and free surface are important factors affecting the structural characteristics of the shock wave systems and the airfoil loading characteristics. When the reflected shock wave acts on the airfoil's lower boundary, there will be a positive moment effect to make the airfoil dive, and the occurrence of this dangerous scene should be avoided. The relevant conclusions obtained can provide a reference for further research and engineering design.

Numerical simulation of supersonic sea-skimming flight based on discontinuous Galerkin method with adaptive mesh refinement framework

Kong,

Liu,

et al. 2023

Direct numerical simulations of high-enthalpy supersonic turbulent channel flows including finite-rate reactions

Chen,

Yang,

Zhao

2024

Direct numerical simulations of temporally evolving high-enthalpy supersonic turbulent channel flows are conducted at a Mach number of 3.0 and Reynolds number of 4880 under isothermal wall conditions. Air is assumed to behave as a five-species mixture, and chemical non-equilibrium and equilibrium assumptions are adopted to investigate the influence of finite-rate reactions on the turbulent statistics and large-scale structures. The two wall temperatures of 1733.2 and 3500 K are such that the mixture components undergo strong dissociation and recombination reactions along the channel. Investigation shows that the turbulent intensity is weakened and the mean and fluctuating temperatures are smaller when finite-rate reactions are considered. The mean dissociation degree is a quadratic function of the normal position, and its curvature under the chemical non-equilibrium assumption is greater than that under the chemical equilibrium assumption. The fluctuating mass fractions of the generated species seem to decrease slightly in the near-wall region, and their distributions are obviously different from those of the fluctuating velocity and fluctuating temperature. Finite-rate reactions increase the proportion of turbulent kinetic energy production in the skin friction decomposition, especially when the wall temperature is 3500 K. The large-scale structures visualized by the cross correlation between temperature and species mass fraction become stronger in the normal direction. The turbulent Schmidt number and several velocity–temperature correlations, including the recovery enthalpy and strong Reynolds analogy, are insensitive to the chemical reaction rate and wall temperature.

Effects of the wall temperature on separation flowfield of swept shock wave/boundary layer interactions

Zhou,

Zhao,

Zhao

et al. 2024

Swept shock wave/boundary layer interaction (SWBLI) is a complex flow phenomenon commonly observed in three-dimensional hypersonic inlets. Wall temperatures can influence the scale of the separation of the swept SWBLI. It may lead to inlets unstart, resulting in a significant decrease in mass flow rate. This study delves into the flowfield of swept SWBLI under varying wall temperatures, using both experimental and numerical methods to examine the effects of these temperature changes on the separation scaling and the fluctuating velocity within the SWBLI flowfield. The investigation uncovers that modifications in wall temperature significantly impact the boundary layer's subsonic layer thickness, streamwise momentum distribution, and shear stress, which collectively alter the separation scale. To estimate characteristic surface limiting streamline angles under changed wall temperature conditions, a predictive model is proposed that utilizes the boundary layer shape factor H as a metric. Additionally, it is established that wall temperature variations can influence surface friction coefficients, which can, in turn, affect the pressure rise process during separation and alter the spatial angle of the separation shock. The fluctuating velocity characteristic reveals that the wall temperature affects the separated flow mainly on the incoming boundary layer.