SPH analysis of inkjet droplet impact dynamics

This paper presents a novel Smoothed Particle Hydrodynamics (SPH) framework for analysis of droplet impact dynamics in a 3D inkjet printing process. Results obtained are validated against experimentally derived high-speed imaging data. The numerical framework is based on the Smoothed Particle Hydrodynamics approach of Monaghan et al [1] which has been proven to be efficient and effective for analysis of dynamic fluid flow problems involving free surface interfaces. The SPH approach has been augmented through addition of the kernel gradient correction scheme proposed by Belytschko et al [2] and stabilization terms of Marrone et el [3]. This correction provides a more accurate approximation of the boundary forces including surface tension which dominate at typical inkjet droplet lengthscales (<100 µm). Analysis is expedited through adoption of the OpenACC programming paradigm to enable GPU based computation. Numerical analyses have been validated against analytical solutions, reference macroscale problems and through comparison with experimental high speed imaging data of the inkjet printing process. The experimental setup consisted of a Fuji Dimatix SL-128 inkjet printhead jetting an acrylate based 3D printing build material onto a glass substrate. Images of a single inkjet droplet impacting onto the glass slide were captured at a rate of 100,000 frames per second, with droplet diameter assessed using a weight test approach. Qualitative comparison of the numerical and experimental results showed a good agreement, indicating that the implemented framework is effective for analysis of the fluidic aspects of the printing process. The model is able to assist in tackling manufacturing issues that can detrimentally influence the quality of manufactured parts through provision of insight into the process

Magnetorheological landing gear: 2. Validation using experimental data

Aircraft landing gears are subjected to a wide range of excitation conditions with conflicting damping requirements. A novel solution to this problem is to implement semi-active damping using magnetorheological (MR) fluids. In part 1 of this contribution, a methodology was developed that enables the geometry of a flow mode MR valve to be optimized within the constraints of an existing passive landing gear. The device was designed to be optimal in terms of its impact performance, which was demonstrated using numerical simulations of the complete landing gear system. To perform the simulations, assumptions were made regarding some of the parameters used in the MR shock strut model. In particular, the MR fluid's yield stress, viscosity, and bulk modulus properties were not known accurately. Therefore, the present contribution aims to validate these parameters experimentally, via the manufacture and testing of an MR shock strut. The gas exponent, which is used to model the shock strut's nonlinear stiffness, is also investigated. In general, it is shown that MR fluid property data at high shear rates are required in order to accurately predict performance prior to device manufacture. Furthermore, the study illustrates how fluid compressibility can have a significant influence on the device time constant, and hence on potential control strategies

Spent fuel sabotage test program, characterization of aerosol dispersal : interim final report.

This multinational, multi-phase spent fuel sabotage test program is quantifying the aerosol particles produced when the products of a high energy density device (HEDD) interact with and explosively particulate test rodlets that contain pellets of either surrogate materials or actual spent fuel. This program provides source-term data that are relevant to plausible sabotage scenarios in relation to spent fuel transport and storage casks and associated risk assessments. We present details and significant results obtained from this program from 2001 through 2007. Measured aerosol results include: respirable fractions produced; amounts, nuclide content, and produced particle size distributions and morphology; measurements of volatile fission product species enhanced sorption--enrichment factors onto respirable particles; and, status on determination of the spent fuel ratio, SFR, needed for scaling studies. Emphasis is provided on recent Phase 3 tests using depleted uranium oxide pellets plus non-radioactive fission product dopants in surrogate spent fuel test rodlets, plus the latest surrogate cerium oxide results and aerosol laboratory supporting calibration work. The DUO{sub 2}, CeO{sub 2}, plus fission product dopant aerosol particle results are compared with available historical data. We also provide a status review on continuing preparations for the final Phase 4 in this program, tests using individual short rodlets containing actual spent fuel from U.S. PWR reactors, with both high- and lower-burnup fuel. The source-term data, aerosol results, and program design have been tailored to support and guide follow-on computer modeling of aerosol dispersal hazards and radiological consequence assessments. This spent fuel sabotage, aerosol test program was performed primarily at Sandia National Laboratories, with support provided by both the U.S. Department of Energy and the Nuclear Regulatory Commission. This program has significant input from, and is cooperatively supported and coordinated by both the U.S. and international program participants in Germany, France, and others, as part of the International Working Group for Sabotage Concerns of Transport and Storage Casks (WGSTSC)

Governing policy evaluation? Towards a new typology

As policy evaluation matures, thoughts are turning to its governance. However, few scholars have combined insights from the evaluation and governance literatures to shed new light on this matter. In order to address this important gap, this article develops a new typology of ways to comprehend and perhaps ultimately govern ex-post policy evaluation activities. The article then explores its validity in the context of climate policy evaluation activities, a vibrant policy area in which the demand for and practices of evaluation have grown fast, particularly in Europe. The analysis reveals that the typology usefully guides new thinking, but also highlights important gaps in our empirical knowledge of the various modes of governing policy evaluation. The article identifies a need for a new research agenda that simultaneously develops a fuller understanding of these evaluation practices and the options for governing them

Spent fuel sabotage aerosol ratio program : FY 2004 test and data summary.

This multinational, multi-phase spent fuel sabotage test program is quantifying the aerosol particles produced when the products of a high energy density device (HEDD) interact with and explosively particulate test rodlets that contain pellets of either surrogate materials or actual spent fuel. This program has been underway for several years. This program provides data that are relevant to some sabotage scenarios in relation to spent fuel transport and storage casks, and associated risk assessments. The program also provides significant technical and political benefits in international cooperation. We are quantifying the Spent Fuel Ratio (SFR), the ratio of the aerosol particles released from HEDD-impacted actual spent fuel to the aerosol particles produced from surrogate materials, measured under closely matched test conditions, in a contained test chamber. In addition, we are measuring the amounts, nuclide content, size distribution of the released aerosol materials, and enhanced sorption of volatile fission product nuclides onto specific aerosol particle size fractions. These data are the input for follow-on modeling studies to quantify respirable hazards, associated radiological risk assessments, vulnerability assessments, and potential cask physical protection design modifications. This document includes an updated description of the test program and test components for all work and plans made, or revised, during FY 2004. It also serves as a program status report as of the end of FY 2004. All available test results, observations, and aerosol analyses plus interpretations--primarily for surrogate material Phase 2 tests, series 2/5A through 2/9B, using cerium oxide sintered ceramic pellets are included. Advanced plans and progress are described for upcoming tests with unirradiated, depleted uranium oxide and actual spent fuel test rodlets. This spent fuel sabotage--aerosol test program is coordinated with the international Working Group for Sabotage Concerns of Transport and Storage Casks (WGSTSC) and supported by both the U.S. Department of Energy and the Nuclear Regulatory Commission