A novel stabilized formulation for 3D compressible viscous flows on moving domains is developed. New weak imposition of essential boundary conditions and sliding-interface formulations are also proposed in the context of moving-domain compressible flows. The new formulation is successfully tested on a set of examples spanning a wide range of Reynolds and Mach numbers showing its superior robustness. Experimental validation of the new formulation is also carried out with good success. In addition, the formulation is applied to simulate flow inside a gas turbine stage, illustrating its potential to support design of real engineering systems through high-fidelity aerodynamic analysis.

Sand corrosion, thermal expansion, and ablation properties of a new class of medium-and high-entropy compositionally complex fluorite oxides (CCFOs) are examined as potential protective coating materials. Five binary oxides were mixed and sintered into dense, single-phase CCFOs of the general formula: [Hf (1-2x)/3 Zr (1-2x)/3 Ce (1-2x)/3 Y x Yb x ]O 2-δ (x = 0.2, 0.074, and 0.029). These CCFOs exhibit decreased molten sand infiltration and interaction at intermediate temperatures (1200-1300°C) in comparison with a cubic yttria-stabilized zirconia (YSZ) reference; however, at higher temperatures, the trend is reversed due to the increased chemical reactivity. The equimolar high-entropy (Hf 0.2 Zr 0.2 Ce 0.2 Y 0.2 Yb 0.2)O 2-δ exhibits no grain boundary penetration by molten sand at all examined temperatures (1200°C-1500°C), although reaction and precipitation are significant. Moreover, these CCFOs exhibit higher intrinsic thermal expansion coefficients (CTE) than the YSZ reference, thereby being more compatible with Ni-based superalloys. The 8YSZ-like (Hf 0.284 Zr 0.284 Ce 0.284 Y 0.074 Yb 0.074)O 2-δ exhibits the highest CTE in this series of CCFOs due to oxygen clustering effects. Finally, these CCFOs also exhibit lower emissivities and form unique faceted microstructures in ablative environments.

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Gas turbine engines are generally optimized to operate at nearly a fixed speed with fixed blade geometries for the design operating condition. When the operating condition of the engine changes, the flow incidence angles may not be optimum with the blade geometry resulting in reduced off-design performance. Articulating the pitch angle of turbine blades in coordination with adjustable nozzle vanes can improve performance by maintaining flow incidence angles within the optimum range at all operating conditions of a gas turbine engine. Maintaining flow incidence angles within the optimum range can prevent the likelihood of flow separation in the blade passage and also reduce the thermal stresses developed due to aerothermal loads for variable speed gas turbine engine applications. U.S. Army Research Laboratory (ARL) has partnered with University of California San Diego and Iowa State University Collaborators to conduct high fidelity stator–rotor interaction analysis for evaluating the aerodynamic efficiency benefits of articulating turbine blade concept. The flow patterns are compared between the baseline fixed geometry blades and articulating conceptual blades. The computational fluid dynamics (CFD) studies were performed using a stabilized finite element method developed by the Iowa State University and University of California San Diego researchers. The results from the simulations together with viable smart material-based technologies for turbine blade actuations are presented in this paper.

Commercial/military fixed-wing aircraft and rotorcraft engines often have to operate in significantly degraded environments consisting of sand, dust, ash, and other particulates. Marine gas turbine engines are subjected to salt spray, while the coal-burning industrial power generation turbines are subjected to fly ash. The presence of solid particles in the working fluid medium has an adverse effect on the durability of these engines as well as performance. Typical turbine blade damages include blade coating wear, sand glazing, calcia–magnesia–alumina–silicate (CMAS) attack, oxidation, and plugged cooling holes, all of which can cause rapid performance deterioration including loss of aircraft. This research represents the complex thermochemomechanical fluid structure interaction problem of semimolten particulate impingement and infiltration onto ceramic thermal barrier coatings (TBCs) into its canonical forms. The objective of this research work is to understand the underpinning interface science of interspersed graded ceramic/metal and ceramic/ceramic composites at the grain structure level for robust coatings and bulk material components for vehicle propulsion systems. This research enhances our understanding of the fundamental relationship between interface properties and the thermomechanical behavior in dissimilar materials for materials by design systems, and creates the ability to develop and fabricate materials with targeted macroscale properties as a function of their interfacial behavior. This project creates a framework to enable the engineered design of solid–solid and liquid–solid interfaces in dissimilar functionalized materials to establish a paradigm shift toward science from the traditional empiricism in engineering TBCs and high temperature highly loaded bulk materials. An integrated approach of modeling and simulation, characterization, fabrication, and validation to solve the fundamental questions of interface mechanisms which affect the properties of novel materials will be validated to guide component material solutions to visionary 2040+ military vehicle propulsion systems.