ESTIMATION OF DISCRETIZATION ERROR FOR THREE DIMENSIONAL CFD SIMULATIONS USING A TAYLOR SERIES MODIFIED EQUATION ANALYSIS

The Consortium for Advanced Simulation of LightWater Reactors (CASL) is working towards developing a virtual reactor called the Virtual Environment for Reactor Application (VERA). As part of this work, computational fluid dynamics (CFD) simulations are being made to inform lower fidelity models to predict heat transfer and fluid flow through a light water reactor core. A 5x5 fuel rod assembly with mixing vanes was chosen to represent a 17x17 fuel rod assembly. Even with this simplified geometry, it is estimated that hundreds of millions of cells are needed for a solution to be close to the asymptotic region. The large number of cells is an issue when completing solution verification studies because of computational cost. Solution verification studies traditionally involve the use of Roache’s grid convergence index (GCI) to estimate the error, but require the solution to be in the asymptotic region. This is a severely limiting restriction for simulations with large range of length scales as is the case with the 5x5 fuel rod assembly with mixing vanes. Unfortunately, GCI does not perform well when the solution is outside the asymptotic region. However, a new method called the robust multi-regression (RMR) solution verification method has the potential to produce good results, even when the solution is outside the asymptotic region. This study builds a software framework that improves the RMR solution verification analysis by improving the error model used to estimate the discretization error. Previous RMR work used a power function to model the error, which was the same function used in the Richardson extrapolation. The power function form is a result of a Taylor series expansion on a uniform grid for simple numerical schemes and physics. It can be improved by completing a Taylor series expansion for the numerical scheme, boundary conditions, and physics that are being employed in the simulation of interest. This framework was shown to improve the ability for the error model to estimate the discretization error and uncertainty. The improved error model was able to predict error on a refined grid within the uncertainty bounds, while the standard error model did not. In addition, the method of manufactured modified equation analysis solutions (MMMEAS) was developed and applied to justify the use of a down selection method for terms in the error model

Comparison of different strategies to measure medication adherence via claims data in patients with chronic heart failure

Medication adherence correlates with morbidity and mortality in patients with chronic heart failure (CHF), but is difficult to assess. We conducted a retrospective methodological cohort study in 3,808 CHF patients, calculating adherence as proportion of days covered (PDC) utilizing claims data from 2010 to 2015. We aimed to compare different parameters’ influence on the PDC of elderly CHF patients exemplifying a complex chronic disease. Investigated parameters were the assumed prescribed daily dose (PDD), stockpiling, and periods of hospital stay. Thereby, we investigated a new approach using the PDD assigned to different percentiles. The different dose assumptions had the biggest influence on the PDC, with variations from 41.9% to 83.7%. Stockpiling and hospital stays increased the values slightly. These results queries that a reliable PDC can be calculated with an assumed PDD. Hence, results based on an assumed PDD have to be interpreted carefully and should be presented with sensitivity analyses to show the PDC's possible range

On the Structure of the Lower Troposphere in the Summertime Stratocumulus Regime of the Northeast Pacific

Data collected in situ as part of the second field study of the Dynamics and Chemistry of Marine Stratocumulus field program are used to evaluate the state of the atmosphere in the region of field operations near 30°N, 120°W during July 2001, as well as its representation by a variety of routinely available data. The routine data include both the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and NCEP–NCAR reanalyses, forecasts from their respective forecast systems (the Integrated and Global Forecast Systems), the 30-km archive from the International Satellite Cloud Climatology Project (ISCCP), the Quick Scatterometer surface winds, and remotely sensed fields derived from radiances measured by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), the Advanced Microwave Sounding Unit, and the Advanced Very High Resolution Radiometer. The analysis shows that outside of the boundary layer the state of the lower troposphere is reasonably represented by the reanalysis and forecast products, with the caveat of a slight warm bias at 850 hPa in the NCEP–NCAR products. Within the planetary boundary layer (PBL) the agreement is not as good: both the boundary layer depth and cloud amount are underpredicted, and the boundary layer temperature correlates poorly with the available data, which may be related to a poor representation of SSTs in this region of persistent cloud cover. ERA-40 also suffers from persistently weak zonal winds within the PBL. Among the satellite records the ISCCP data are found to be especially valuable, evincing skill in both predicting boundary layer depth (from cloud-top temperatures and TMI surface temperatures) and cloud liquid water paths (from cloud optical depths). An analysis of interannual variability (among Julys) based on ERA-40 and the 1983–2001 ISCCP record suggests that thermodynamic quantities show similar interannual and synoptic variability, principally concentrated just above the PBL, while dynamic quantities vary much more on synoptic time scales. Furthermore, the analysis suggests that the correlation between stratocumulus cloud amount and lower-tropospheric stability exhibits considerable spatial structure and is less pronounced than previously thought

Analysis of an Aircraft Honeycomb Sandwich Panel with Circular Face Sheet/Core Disbond Subjected to Ground-Air Pressurization

The ground-air pressurization of lightweight honeycomb sandwich structures caused by alternating pressure differences between the enclosed air within the honeycomb core and the ambient environment is a well-known and controllable loading condition of aerospace structures. However, initial face sheet/core disbonds intensify the face sheet peeling effect of the internal pressure load significantly and can decrease the reliability of the sandwich structure drastically. Within this paper, a numerical parameter study was carried out to investigate the criticality of initial disbonds in honeycomb sandwich structures under ground-air pressurization. A fracture mechanics approach was used to evaluate the loading at the disbond front. In this case, the strain energy release rate was computed via the Virtual Crack Closure Technique. Special attention was paid to the pressure-deformation coupling which can decrease the pressure load within the disbonded sandwich section significantly when the structure is highly deformed

Electronic integration of the uk-1 international ionosphere satellite

Electronic integration of international ionosphere satellit

Face Sheet/Core Disbond Growth in Honeycomb Sandwich Panels Subjected to Ground-Air-Ground Pressurization and In-Plane Loading

Typical damage modes in light honeycomb sandwich structures include face sheet/core disbonding and core fracture, both of which can pose a threat to the structural integrity of a component. These damage modes are of particular interest to aviation certification authorities since several in-service occurrences, such as rudder structural failure and other control surface malfunctions, have been attributed to face sheet/core disbonding. Extensive studies have shown that face sheet/core disbonding and core fracture can lead to damage propagation caused by internal pressure changes in the core. The increasing use of composite sandwich construction in aircraft applications makes it vitally important to understand the effect of ground-air-ground (GAG) cycles and conditions such as maneuver and gust loads on face sheet/core disbonding. The objective of the present study was to use a fracture mechanics based approach developed earlier to evaluate the loading at the disbond front caused by ground-air-ground pressurization and in-plane loading. A honeycomb sandwich panel containing a circular disbond at one face sheet/core interface was modeled with three-dimensional (3D) solid finite elements. The disbond was modeled as a discrete discontinuity and the strain energy release rate along the disbond front was computed using the Virtual Crack Closure Technique (VCCT). Special attention was paid to the pressure-deformation coupling which can decrease the pressure load within the disbonded sandwich section significantly when the structure is highly deformed. The commercial finite element analysis software, Abaqus/Standard, was used for the analyses. The recursive pressure-deformation coupling problem was solved by representing the entrapped air in the honeycomb cells as filled cavities in Abaqus/Standard. The results show that disbond size, face sheet thickness and core thickness are important parameters that determine crack tip loading at the disbond front. Further, the pressure-deformation coupling was found to have an important load decreasing effect [6]. In this paper, a detailed problem description is provided first. Second, the analysis methodology is presented. The fracture mechanics approach used is described and the specifics of the finite element model, including the fluid-filled cavities, are introduced. Third, the initial model verification and validation are discussed. Fourth, the findings from a closely related earlier study [6] are summarized. These findings provided the basis for the current investigation. Fifth, an aircraft ascent scenario from 0 to 12192 m (0 to 40000 ft) is considered and the resulting crack tip loading at the disbond front is determined. In-plane loading to simulate maneuvers and gust conditions are also considered. Sixth, the results are shown for a curved panel, which was used to simulate potential fuselage applications. Finally, a brief summary of observations is presented and recommendations for improvement are provided

ESTIMATION OF DISCRETIZATION ERROR FOR THREE DIMENSIONAL CFD SIMULATIONS USING A TAYLOR SERIES MODIFIED EQUATION ANALYSIS

The Consortium for Advanced Simulation of LightWater Reactors (CASL) is working towards developing a virtual reactor called the Virtual Environment for Reactor Application (VERA). As part of this work, computational fluid dynamics (CFD) simulations are being made to inform lower fidelity models to predict heat transfer and fluid flow through a light water reactor core. A 5x5 fuel rod assembly with mixing vanes was chosen to represent a 17x17 fuel rod assembly. Even with this simplified geometry, it is estimated that hundreds of millions of cells are needed for a solution to be close to the asymptotic region. The large number of cells is an issue when completing solution verification studies because of computational cost. Solution verification studies traditionally involve the use of Roache’s grid convergence index (GCI) to estimate the error, but require the solution to be in the asymptotic region. This is a severely limiting restriction for simulations with large range of length scales as is the case with the 5x5 fuel rod assembly with mixing vanes. Unfortunately, GCI does not perform well when the solution is outside the asymptotic region. However, a new method called the robust multi-regression (RMR) solution verification method has the potential to produce good results, even when the solution is outside the asymptotic region. This study builds a software framework that improves the RMR solution verification analysis by improving the error model used to estimate the discretization error. Previous RMR work used a power function to model the error, which was the same function used in the Richardson extrapolation. The power function form is a result of a Taylor series expansion on a uniform grid for simple numerical schemes and physics. It can be improved by completing a Taylor series expansion for the numerical scheme, boundary conditions, and physics that are being employed in the simulation of interest. This framework was shown to improve the ability for the error model to estimate the discretization error and uncertainty. The improved error model was able to predict error on a refined grid within the uncertainty bounds, while the standard error model did not. In addition, the method of manufactured modified equation analysis solutions (MMMEAS) was developed and applied to justify the use of a down selection method for terms in the error model

Patients’ handling of a standardized medication plan: a pilot study and method development

Purpose: The Action Plan for Medication Safety by the German Federal Ministry of Health introduced a standardized medication plan (MP), a printable document for the patient. The practical handling needs to be tested before the nationwide implementation in Germany. Therefore, the aims of our study were 1) to develop an instrument to evaluate the usage of the standardized MP, 2) to assess if patients can locate, and 3) understand important information. Moreover, we explored patients’ opinion and suggestions regarding the standardized MP template. Patients and methods: We conducted a cross-sectional study to evaluate the practical handling of the standardized MP. We interviewed 40 adult patients in seven community pharmacies in Germany, who took at least five medicines regularly and gave their written informed consent. The interview consisted of questions regarding finding and understanding information provided on a mock-up MP, patients’ opinion and the execution of the information on the MP by filling pill boxes. We eventually developed a new evaluation method to quantify the practical handling of the MP by rating the pill boxes filled by the patients. Results: Overall, the participants rated the MP positively. Thirty-nine (98%) participants found important information on a mock-up standardized MP. Patients were questioned to identify if they understood information on medical intake as it relates to meals. In particular, they were questioned about medicine intake “1 hour before a meal”, which 98% (n=39) interpreted correctly, and “during a meal”, which 100% (n=40) interpreted correctly. The less precise advice of “before a meal” was interpreted correctly by 73% (n=29), and only 15% (n=6) correctly interpreted the term “after the meal”. The evaluation of the filled pill boxes resulted in the “Evaluation Tool to test the handling of the Medication Plan” (ET-MP) – a weighted scoring system. Conclusion: The standardized MP is clearly arranged, and patients are able to find important information. The findings of this study resulted in minor but important revisions of the standardized MP template. The developed evaluation tool ET-MP may serve as an objective instrument to assess patients’ ability to transfer written information on the MP into practical handling of medicines