Evaluation and application of the Baldwin-Lomax turbulence model in two-dimensional, unsteady, compressible boundary layers with and without separation in engine inlets

There is a practical need to model high speed flows that exist in jet engine inlets. The boundary layers that form in these inlets may be turbulent or laminar and either separated or attached. Also, unsteady supersonic inlets may be subject to frequent changes in operating conditions. Some changes in the operating conditions of the inlets may include varying the inlet geometry, bleeds and bypasses, and rotating or translating the centerbody. In addition, the inlet may be either started or unstarted. Therefore, a CFD code, used to model these inlets, may have to run for several different cases. Also, since the flow conditions through an unsteady inlet may be continually fluctuating, the CFD code which models these flows may have to be run over many time steps. Therefore, it would be beneficial that the code run quickly. Many turbulence models, however, are cumbersome to implement and require a lot of computer time to run, since they add to the number of differential equations to be solved to model a flow. The Baldwin-Lomax turbulence model is a popular model. It is an algebraic, eddy viscosity model. The Baldwin-Lomax model is used in many CFD codes because it is quick and easy to implement. In this paper, we will discuss implementing the Baldwin-Lomax turbulence model for both steady and unsteady compressible flows. In addition, these flows may be either separated or attached. In order to apply this turbulence model to flows which may be subjected to these conditions, certain modifications should be made to the original Baldwin-Lomax model. We will discuss these modifications and determine whether the Baldwin-Lomax model is a viable turbulence model that produces reasonably accurate results for high speed flows that can be found in engine inlets

A quantum mechanical description of the experiment on the observation of gravitationally bound states

Quantum states in the Earth's gravitational field were observed, when ultra-cold neutrons fall under gravity. The experimental results can be described by the quantum mechanical scattering model as it is presented here. We also discuss other geometries of the experimental setup which correspond to the absence or the reversion of gravity. Since our quantum mechanical model describes, particularly, the experimentally realized situation of reversed gravity quantitatively, we can practically rule out alternative explanations of the quantum states in terms of pure confinement effects.Comment: LaTeX, 10 pages, 4 figures, v2: references adde

Predictive Value of the National Institutes of Health Stroke Scale and the Mini-Mental State Examination for Neurologic Outcome After Coronary Artery Bypass Graft Surgery

ObjectiveWe intended to define the role of the National Institutes of Health Stroke Scale and the Mini-Mental State Examination in identifying adverse neurologic outcomes in a large international sample of patients undergoing cardiac surgery.MethodsWe evaluated 4707 patients undergoing cardiac surgery with cardiopulmonary bypass at 72 centers in 17 countries between November 1996 and June 2000. Prespecified overt neurologic outcomes were categorized as type I (clinically diagnosed stroke, transient ischemic attack, encephalopathy, or coma) or type II (deterioration of intellectual function). The National Institutes of Health Stroke Scale and Mini-Mental State Examination were administered preoperatively and on postoperative day 3, 4, or 5. Receiver operating characteristic curves were plotted to determine the predictive value of worsening in National Institutes of Health Stroke Scale and Mini-Mental State Examination scores with respect to type I and II outcomes.ResultsThe receiver operating characteristic area under the curve for changes in National Institutes of Health Stroke Scale score (n = 4620) was 0.89 for type I outcomes and 0.66 for type II outcomes. A 1-point worsening in National Institutes of Health Stroke Scale score provided excellent discrimination (86% specificity; 84% sensitivity) of type I outcomes. The receiver operating characteristic area under the curve for changes in Mini-Mental State Examination score (n = 4707) was 0.75 for type I outcomes and 0.71 for type II outcomes. A 2-point worsening in Mini-Mental State Examination score provided only fair discrimination (73% specificity; 62% sensitivity) of type II outcomes.ConclusionWe used baseline controls and postoperative worsening in National Institutes of Health Stroke Scale and Mini-Mental State Examination scores to predict both serious adverse neurologic outcome and deterioration of intellectual function. Our findings provide the only reference for evaluating these tests that are used in cardiac surgical clinical trials

Predictive value of the National Institutes of Health Stroke Scale and the Mini-Mental State Examination for neurologic outcome after coronary artery bypass graft surgery

OBJECTIVE: We intended to define the role of the National Institutes of Health Stroke Scale and the Mini-Mental State Examination in identifying adverse neurologic outcomes in a large international sample of patients undergoing cardiac surgery. METHODS: We evaluated 4707 patients undergoing cardiac surgery with cardiopulmonary bypass at 72 centers in 17 countries between November 1996 and June 2000. Prespecified overt neurologic outcomes were categorized as type I (clinically diagnosed stroke, transient ischemic attack, encephalopathy, or coma) or type II (deterioration of intellectual function). The National Institutes of Health Stroke Scale and Mini-Mental State Examination were administered preoperatively and on postoperative day 3, 4, or 5. Receiver operating characteristic curves were plotted to determine the predictive value of worsening in National Institutes of Health Stroke Scale and Mini-Mental State Examination scores with respect to type I and II outcomes. RESULTS: The receiver operating characteristic area under the curve for changes in National Institutes of Health Stroke Scale score (n = 4620) was 0.89 for type I outcomes and 0.66 for type II outcomes. A 1-point worsening in National Institutes of Health Stroke Scale score provided excellent discrimination (86% specificity; 84% sensitivity) of type I outcomes. The receiver operating characteristic area under the curve for changes in Mini-Mental State Examination score (n = 4707) was 0.75 for type I outcomes and 0.71 for type II outcomes. A 2-point worsening in Mini-Mental State Examination score provided only fair discrimination (73% specificity; 62% sensitivity) of type II outcomes. CONCLUSION: We used baseline controls and postoperative worsening in National Institutes of Health Stroke Scale and Mini-Mental State Examination scores to predict both serious adverse neurologic outcome and deterioration of intellectual function. Our findings provide the only reference for evaluating these tests that are used in cardiac surgical clinical trials

Arm vein as a last autogenous option for infrainguinal bypass surgery: It is worth the effort

Objectives: Considerable evidence exists for the use of arm vein conduit in lower limb bypass surgery. The use of arm vein in preference to synthetic conduit as a last autogenous option was assessed for patency and limb salvage outcomes. Materials and methods: A prospective database was interrogated and checked against TQEH operating theatre database to detect all infrainguinal arm vein bypasses performed between 1997 and 2005. Patency, limb salvage and survival data for 37 arm vein bypasses was calculated using the Kaplan-Meier survival estimate method. Results: There were no perioperative deaths. 30 day patency rates were 89% primary, 95% secondary and 95% limb salvage. 12 month patency rates were 56% primary, 79% secondary and 91% limb salvage. 5 year patency rates were 37% primary, 76% secondary and 91% limb salvage. There was no significant patency advantage for primary vs. “redo” grafts (p = 0.54), single vessel vs. spliced conduits (p = 0.33) or popliteal vs tibial outflow (p = 0.80). Patient survival rate was 92% and 65% at 1 and 5 years respectively. Conclusion: Lower limb bypasses using arm vein can be performed with favourable patency and limb salvage compared to synthetic conduits. However, secondary interventions are frequently required to maintain patency. We recommend a vigilant surveillance program for early identification of patency threatening disease.R.L. Varcoe, W. Chee, P. Subramaniam, D.M. Roach, G.L. Benveniste and R.A. Fitridg