The vibration of a thin-walled cylindrical, compliant viscoelastic tube with internal turbulent flow due to an axisymmetric constriction is studied theoretically and experimentally. Vibration of the tube is considered with internal fluid coupling only, and with coupling to internal-flowing fluid and external stagnant fluid or external tissue-like viscoelastic material. The theoretical analysis includes the adaptation of a model for turbulence in the internal fluid and its vibratory excitation of and interaction with the tube wall and surrounding viscoelastic medium. Analytical predictions are compared with experimental measurements conducted on a flow model system using laser Doppler vibrometry to measure tube vibration and the vibration of the surrounding viscoelastic medium. Fluid pressure within the tube was measured with miniature hydrophones. Discrepancies between theory and experiment, as well as the coupled nature of the fluid-structure interaction, are described. This study is relevant to and may lead to further insight into the patency and mechanisms of vascular failure, as well as diagnostic techniques utilizing noninvasive acoustic measurements.

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Ultrasound (US) medical imaging technology is enhanced by integrating a simultaneous noninvasive audible frequency measurement of biological sounds that could be indicative of pathology. Measurement of naturally-occurring biological acoustic phenomena can augment conventional imaging technology by providing unique information about material structure and system function. Sonic phenomena of diagnostic value are associated with a wide range of biological functions, such as breath sounds, bowel sounds, and vascular bruits. The initial focus of this multimode technology was to provide an improved diagnostic tool for common peripheral vascular complications that result in transitional or turbulent blood flow, such as associated with arteriovenous (AV) grafts and stenoses in common carotid and other arteries due to plaque buildup. We review: (1) the development the multimode system by combining a commercial US system with a novel sonic sensor array and associated instrumentation, and (2) the evaluation of its capability via controlled phantom models of basic subsurface sound sources/structures, as well as simulations of constricted peripheral blood vessels. [Work supported by NIH EB002511 and HL55296, and Whitaker Foundation BME RG 01-0198.]

Efforts to develop fibrous ceramic monoliths for primarily structural applications are described. Fibrous monoliths (FMs) are relatively insensitive to flaws and can exhibit graceful failure and large work-of-fracture values. They can be inexpensively produced in a wide variety of forms by conventional ceramic processing methods such as extrusion. The FM project that is the subject of this report involved investigations to (1) develop FMs that can be pressureless sintered rather than hot pressed, (2) develop technologies to continuously extrude FM filaments and inexpensively fabricate FM components, (3) evaluate the performance of commercial and new, prototype FMs, (4) develop micromechanical models to guide the design of new FMs and predict their properties, and (5) forge collaborations with industry to produce useful parts.