The term “immersed boundary method” was first used in reference to a method developed by Peskin (1972) to simulate cardiac mechanics and associated blood flow. The distinguishing feature of this method was that the entire simulation was carried out on a Cartesian grid, which did not conform to the geometry of the heart, and a novel procedure was formulated for imposing the effect of the immersed boundary (IB) on the flow. Since Peskin introduced this method, numerous modifications and refinements have been proposed and a number of variants of this approach now exist. In addition, there is another class of methods, usually referred to as “Cartesian grid methods,” which were originally developed for simulating inviscid flows with complex embedded solid boundaries on Cartesian grids (Berger & Aftosmis 1998, Clarke et al. 1986, Zeeuw & Powell 1991). These methods have been extended to simulate unsteady viscous flows (Udaykumar et al. 1996, Ye et al. 1999) and thus have capabilities similar to those of IB methods. In this review, we use the term immersed boundary (IB) method to encompass all such methods that simulate viscous flows with immersed (or embedded) boundaries on grids that do not conform to the shape of these boundaries. Furthermore, this review focuses mainly on IB methods for flows with immersed solid boundaries. Application of these and related methods to problems with liquid-liquid and liquid-gas boundaries was covered in previous reviews by Anderson et al. (1998) and Scardovelli & Zaleski (1999). Consider the simulation of flow past a solid body shown in Figure 1a. The conventional approach to this would employ structured or unstructured grids that conform to the body. Generating these grids proceeds in two sequential steps. First, a surface grid covering the boundaries b is generated. This is then used as a boundary condition to generate a grid in the volume f occupied by the fluid. If a finite-difference method is employed on a structured grid, then the differential form of the governing equations is transformed to a curvilinear coordinate system aligned with the grid lines (Ferziger & Peric 1996). Because the grid conforms to the surface of the body, the transformed equations can then be discretized in the

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Immersed boundary methods

Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Polymers for 3D Printing and Customized Additive Manufacturing

A coated implantable medical device 10 includes a structure 12 adapted for introduction into the vascular system, esophagus, trachea, colon, biliary tract, or urinary tract; at least one layer 18 of a bioactive material positioned over the structure 12; and at least one porous layer 20 positioned over the bioactive material layer 18. Preferably, the structure 12 is a coronary stent, and the bioactive material is at least one of heparin, dexamethasone or a dexamethasone derivative. The device 10 includes layers 18 and 22 of heparin and dexamethasone, the layer 22 of dexamethasone being positioned above the layer 18 of heparin. The layers of bioactive material also can be individual materials or a combination of different materials. Unexpectedly, the more soluble heparin markedly promotes the release of the less soluble dexamethasone above it. The porous layer 20 is composed of a polymer applied by vapor or plasma deposition and provides a controlled release of the bioactive material. It is particularly preferred that the polymer is a polyimide, parylene or a parylene derivative, which is deposited without solvents, heat or catalysts, merely by condensation of a monomer vapor.

Coated implantable medical device

A polymer-based, paclitaxel-eluting stent in patients with coronary artery disease☆

Light- and ink-based three-dimensional (3D) printing methods allow the rapid design and fabrication of materials without the need for expensive tooling, dies or lithographic masks. They have led to an era of manufacturing in which computers can control the fabrication of soft matter that has tunable mechanical, electrical and other functional properties. The expanding range of printable materials, coupled with the ability to programmably control their composition and architecture across various length scales, is driving innovation in myriad applications. This is illustrated by examples of biologically inspired composites, shape-morphing systems, soft sensors and robotics that only additive manufacturing can produce.

Printing soft matter in three dimensions

Measurements of the 3D velocity and concentration fields were obtained using magnetic resonance imaging for a pressure side cutback film cooling experiment. The cutback geometry consisted of rectangular slots separated by straight lands; inside each of the slots was an airfoil-shaped blockage. The results from this trailing edge configuration, the “island airfoil,” are compared to the results obtained with the “generic airfoil,” a geometry with narrower slots, wider, tapered lands, and no blockages. The objective was to determine how the narrower lands and internal blockages affected the average film cooling effectiveness and the spanwise uniformity. Velocimetry data revealed that strong horseshoe vortices formed around the blockages in the slots, which resulted in greater coolant non-uniformity on the airfoil breakout surface and in the wake. The thinner lands of the island airfoil allowed the coolant to cover a larger fraction of the trailing edge span, giving a much higher spanwise-averaged surface effectiveness, especially near the slot exit where the generic airfoil lands are widest.

3D Velocity and Scalar Field Measurements of an Airfoil Trailing Edge With Slot Film Cooling: The Effect of an Internal Structure in the Slot

Magnetic Resonance Thermometry (MRT) is a maturing diagnostic used to measure three-dimensional temperature fields. It has great potential for investigating fluid flows within complex geometries leveraging medical grade MRI equipment and software along with novel measurement techniques. The efficacy of the method in engineering applications increases when coupled with other well established MRI-based techniques such as Magnetic Resonance Velocimetry (MRV). In this study, a challenging geometry is presented with direct application to a complex gas turbine blade cooling scheme. Turbulent external flow with a Reynolds number of 136,000 passes a hollowed NACA-0012 airfoil with internal cooling features. Inserts within the airfoil, fed by a second flow line with an average temperature difference of 30 K from the main flow and a temperature-dependent Reynolds number in excess of 1,800, produce a conjugate heat transfer scenario including impingement cooling on the inside surface of the airfoil. The airfoil cooling scheme also includes zonal recirculation, surface film cooling, and trailing edge ejection features. The entire airfoil surface is constructed of a stereolithography resin — Accura 60 — with low thermal conductivity. The three-dimensional internal and external velocity field is measured using MRV. The fluid temperature field is measured within and outside of the airfoil with MRT and the results are compared with a computational fluid dynamics (CFD) solution to assess the current state of the art for combined MRV/MRT techniques for investigating these complex internal and external flows. The accompanying CFD analysis provides a prediction of the velocity and temperature fields, allowing for errors in the MRT technique to be estimated.

Three Dimensional Velocity and Temperature Field Measurements of Internal and External Turbine Blade Features Using Magnetic Resonance Thermometry

A trailing edge slot film cooling configuration designed for enhanced surface effectiveness at a decreased coolant flowrate is proposed. Magnetic resonance imaging (MRI) techniques were used to obtain measurements of the mean 3D velocity and concentration fields. These measurements are compared to previously reported results on two other trailing edge configurations. The surface effectiveness of the proposed slot film cooling configuration is higher than that of the baseline configuration, even at a 25% lower coolant flowrate. The mean fields are used to calculate an isotropic, spatially-varying turbulent diffusivity for each of these trailing edge configurations. These diffusivities are compared to offer insight into the effect of land shape on turbulence properties.Copyright © 2013 by ASME

Measurements of a Trailing Edge Slot Film Cooling Geometry Designed for Reduced Coolant Flowrate and High Surface Effectiveness

Hot streaks from the combustor and cool streaks from nozzle vane film cooling impose strong inlet temperature variations on high pressure turbine blades, which can lead to local hot or cold spots, high thermal stresses, and fatigue failures. Furthermore, the complex three dimensional flows around the vane may act to concentrate cool or hot fluid exiting the vane row. In order to optimize the cooling design of the turbine blades, the designer must be able to predict the temperature distribution entering the turbine rotor. Therefore, it is important to understand and predict how combustor hot streaks are dispersed as they pass through the vane row. The goal of the present work is to provide detailed three dimensional velocity and temperature data for simulated combustor hot streaks developing through a film cooled vane cascade using the Magnetic Resonance Velocity/Concentration experimental technique. The measurements show that the hot streaks are thinned by acceleration through the vane cascade and diffused by turbulence. The turbulent diffusivity is suppressed by acceleration and leaves significant temperature nonuniformity in the vane wake.Copyright © 2015 by ASME

Quantitative MRI Measurements of Hot Streak Development in a Turbine Vane Cascade

Methods of altering properties of tissues, by providing an effective modifying amount of zinc, which may be in the form of zinc ions. This is accomplished through the use of topical compositions containing one or more zinc-containing components such as salts and/or other zinc compounds or complexes, particularly zinc acetate. Altering properties of tissues includes increasing or decreasing fatty tissue, increasing or decreasing epidermal thickness, increasing elastin content, and preventing or treating gum regression or atrophy. Also disclosed is the provision of a contact lens coated with a zinc-containing material, to improve vision by increasing elastin content of the lens of the eye through release of zinc ions.

Christopher J. Elkins

Papers

3D Velocity and Scalar Field Measurements of an Airfoil Trailing Edge With Slot Film Cooling: The Effect of an Internal Structure in the Slot

Three Dimensional Velocity and Temperature Field Measurements of Internal and External Turbine Blade Features Using Magnetic Resonance Thermometry

Measurements of a Trailing Edge Slot Film Cooling Geometry Designed for Reduced Coolant Flowrate and High Surface Effectiveness

Quantitative MRI Measurements of Hot Streak Development in a Turbine Vane Cascade

Modulation of zinc levels to improve tissue properties