Advanced Models for Aeroelastic Analysis of Propulsion Systems
This report describes an integrated, multidisciplinary simulation capability for aeroelastic analysis and optimization of advanced propulsion systems. This research is intended to improve engine development, acquisition, and maintenance costs. One of the proposed simulations is aeroelasticity of blades, cowls, and struts in an ultra-high bypass fan. These ducted fans are expected to have significant performance, fuel, and noise improvements over existing engines. An interface program was written to use modal information from COBSTAN and NASTRAN blade models in aeroelastic analysis with a single rotation ducted fan aerodynamic code.
Cascade flutter analysis with transient response aerodynamics
Abstract Two methods for calculating linear frequency domain unsteady aerodynamic coefficients from a time-marching full-potential cascade solver are developed and verified. In the first method, the influence coefficient method, solutions to elemental problems are superposed to obtain the solutions for a cascade in which all blades are vibrating with a constant interblade phase angle. The elemental problem consists of a single blade in the cascade oscillating while the other blades remain stationary. In the second method, the pulse response method, the response to the transient motion of a blade is used to calculate influence coefficients. This is done by calculating the Fourier transforms of the blade motion and the response. Both methods are validated by comparison with the harmonic oscillation method, in which all the airfoils are oscillated, and are found to give accurate results. The aerodynamic coefficients obtained from these methods are used for frequency domain flutter calculations involving a typical section blade structural model. Flutter calculations are performed for two examples over a range of subsonic Mach numbers using both flat plates and actual airfoils.
Follicular Dendritic Cell Tumor of the Liver: A Clinicopathologic and Epstein-Barr Virus Study of Two Cases
Two cases of hepatic follicular dendritic cell (FDC) tumor are described. Both patients were female, aged 57 and 51 years. They presented with epigastralgia or abdominal fullness and weight loss. The first patient refused surgical resection. She developed progressive polyclonal gammopathy and then bilateral purpura over the legs. Skin biopsy revealed leukocytoclastic vasculitis with granular vascular deposits of IgA and C3. The second patient had marked peripheral blood and tissue eosinophilia. The histological diagnosis was confirmed by positive staining for CD21 and CD23. The stromal lymphocytes were predominantly composed of CD3(+) and CD8(+) cells. In situ hybridization for EBER showed a positive nuclear signal in tumor cells but not in inflammatory cells. Polymerase chain reaction amplification for Exon 3 of the latent membrane protein-1 (LMP-1) gene showed a characteristic 30-bp deletion between nucleotides 168282 and 168253, corresponding to the B95-8 sequence. The unique clinicopathological features of our cases have not been reported for FDC tumors before. The clinical significance of the 30-bp deletion in Exon 3 of the LMP-1 gene in FDC tumor of the liver warrants further investigation.