Hydrodynamic Behavior of Gap Resonance in Multiple-Box Systems with Sharp and Round Inlet Configurations

Fluid resonance within narrow gaps in multiple-box systems with sharp and round inlet configurations are investigated by using the potential flow and viscous fluid flow models in the OpenFOAM^(■)package.Evident discrepancy between two numerical models can be observed for sharp inlet configurations.In addition to the dramatical decrease of resonant amplitude in narrow gaps,some peak values at the higher resonant frequencies predicted by the potential flow model even disappear in the viscous fluid flow results.The decreased normalized resonant amplitudes with the increase of incident wave amplitude can be observed for sharp inlet configurations.However,the hydrodynamic behaviors of multiple-box system with round inlet configurations between potential flow and viscous fluid flow models are quite similar with each other.The normalized resonant amplitudes are nearly independent of incident wave amplitudes for multiple-box systems with round inlet configurations.This implies that the energy dissipation associated with fluid viscosity and flow rotation plays an important role in the gap resonance for sharp inlet configurations;while it is insignificant for round inlet configurations.

Synthesis and performance characterization of Hafnium-based multilayer coating applied over carbon/carbon composites with sharp leading edge

Carbon/carbon(C/C)composites have been acknowledged as potential candidates in aerospace vehicles,but their oxygen sensitivity still remains an enormous challenge.In this work,a novel multilayer coating consisted of HfC-2.5 mol.%Hf_(6)Ta_(2)O_(17),HfC-40 mol.%SiC,HfC-2.5 mol.%Hf_(6)Ta_(2)O_(17) and HfC-60 mol.%SiC sublayers from surface to inside was designed and fabricated on the surface of C/C composites with sharp leading edge by plasma spraying.Its ablation resistance was assessed using oxyacetylene torch with a maximum temperature over 2300℃ and compared with monolayered coatings.The multilayer coating revealed preferable ablation retardation capacity evidenced by its integrated profile and less flaw quantity.Such benefits were primarily stemmed from the effective structural design and rational material selection.The former was able to reduce the thermal stress within the ablated scale,the latter contributed to rising the high-temperature resistance and oxygen barrier ability of the coating.

Ablation behavior of(ZrC/SiC)_(3)alternate coating prepared on sharp leading edge C/C composites by CVD

A(ZrC/SiC)_(3)alternate coating was deposited on sharp leading edge(SLE)C/C composites by chemical vapor deposition(CVD).The ablation behavior was examined via oxyacetylene torch with heat flux of 2.38 MW/m^2.The results indicated that the alternate coating exhibited great ablation resistance,providing an effective protection for C/C composites.In initial rapid heating stage,the(ZrC/SiC)_(3) alternate coating can relieve thermal stress,avoiding the peeling of coating and keeping an intact coating structure.In subsequent ablation,the Si C layers in central region were consumed rapidly,leaving layered interspaces.Three stacked ZrO_(2) layers were reserved with the assistance of the release of thermal stress by interspaces,offering a great anti-scouring effect.In transition and border regions,the alternate Si C layers can delay oxygen erosion of inner coating and C/C substrate by the formation of SiO_(2).It is believed that the results would be helpful for the design and application of anti-ablation coatings on SLE C/C composites.