Large eddy simulation of turbine internal cooling ducts

Large-Eddy Simulation (LES) and hybrid Reynolds-averaged Navier-Stokes-LES (RANSLES) methods are applied to a turbine blade ribbed internal duct with a 180 degree bend containing 24 pairs of ribs. Flow and heat transfer predictions are compared with experimental data and found to be in agreement. The choice of LES model is found to be of minor importance as the flow is dominated by large geometric scale structures. This is in contrast to several linear and nonlinear RANS models, which display turbulence model sensitivity. For LES, the influence of inlet turbulence is also tested and has a minor impact due to the strong turbulence generated by the ribs. Large scale turbulent motions destroy any classical boundary layer reducing near wall grid requirements. The wake-type flow structure makes this and similar flows nearly Reynolds number independent, allowing a range of flows to be studied at similar cost. Hence LES is a relatively cheap method for obtaining accurate heat transfer predictions in these types of flows.This is the accepted manuscript. The final version is available at http://www.sciencedirect.com/science/article/pii/S0045793015000663

Parallel computation of aeroacoustics of industrially relevant complex-geometry aeroengine jets

Jet noise is still a distinct noise component when a commercial aircraft is taking off. A parallel high-fidelity simulation framework for industrial jet noise prediction is presented in this paper. This framework includes complex geometry meshing and Ffowcs Williams-Hawkings (FW-H) surface placement during preprocessing, a parallel hybrid RANS-LES flow solver coupled with an FW-H acoustic solver in the simulation and mean and unsteady data processing after the simulation. The use of this framework is demonstrated through two jet noise prediction cases: in-flight heated jets and installed ultra-high bypass-ratio (UHBPR) engines. These simulations can provide more insight than experimental tests into jet flow physics for engineering model improvement. Additional advantages are also shown in the cost and turn-around time. Thus there is great potential for high-fidelity jet noise simulations to partly replace rig tests for industrial use in the future

Planning, Preparation, and Transport of the High-Enriched Uranium Spent Nuclear Fuel from the Czech Republic to the Russian Federation

The United States, Russian Federation, and the International Atomic Energy Agency have been working together on a program called the Russian Research Reactor Fuel Return (RRRFR) Program, which is part of the Global Threat Reduction Initiative. The purpose of this program is to return Soviet or Russian-supplied high-enriched uranium (HEU) fuel, currently stored at Russian-designed research reactors throughout the world, to Russia. In February 2003, the RRRFR Program began discussions with the Nuclear Research Institute (NRI) in Rež, Czech Republic, about returning their HEU spent nuclear fuel to the Russian Federation for reprocessing. In March 2005, the U.S. Department of Energy signed a contract with NRI to perform all activities needed for transporting their HEU spent nuclear fuel to Russia. After 2 years of intense planning, preparations, and coordination at NRI and with three other countries, numerous organizations and agencies, and a Russian facility, this shipment is scheduled for completion before the end of 2007. This paper will provide a summary of activities completed for making this international shipment. This paper contains an introduction and background of the RRRFR Program and the NRI shipment project. It summarizes activities completed in preparation for the shipment, including facility preparations at NRI in Rež and FSUE “Mayak” in Ozyorsk, Russia; a new transportation cask system; regulatory approvals; transportation planning and preparation in the Czech Republic, Slovakia, Ukraine, and the Russian Federation though completion of the Unified Project and Special Ecological Programs. The paper also describes fuel loading and cask preparations at NRI and final preparations/approvals for transporting the shipment across the Czech Republic, Slovakia, Ukraine, and the Russian Federation to FSUE Mayak where the HEU spent nuclear fuel will be processed, the uranium will be downblended and made into low-enriched uranium fuel for commercial reactor use, and the high-level waste from the processing will be stabilized and stored for less than 20 years before being sent back to the Czech Republic for final disposition. Finally, the paper contains a section for the summary and conclusions

Noise Sources of Closely Installed Subsonic Jets

Emitted noise of an installed jet is significantly louder, compared to an isolated jet. When the jet is installed closely under a solid surface, nonlinear jet-surface interactions occur and modify the jet turbulence in addition to the linear potential field interactions. In this paper, the noise sources are decomposed into quadrupole sources due to turbulent mixing and dipole sources due to the unsteady loadings on the surface. The change of the two sources due to the close installation is first characterised in the near-field and their contribution to the far-field noise is then quantified. The quadrupole source and noise are examined using Goldstein’s acoustic analogy, while the dipole noise is studied with the Amiet approach to model trailing edge scattering of evanescent hydrodynamic waves. The methods are first validated in a plate-jet configuration and then applied to analyze the noise sources of a closely installed jet-wing configuration. The results show that the increased quadrupole source primarily contributes to the installation noise at the polar angle of 30 degrees, while the dipole source is responsible for the installation noise at the higher polar angles.The ARCHER computing time is provided by the UK Turbulence Consortium under EPSRC grant EP/L000261/1 and PRACE Distributed European Computing Initiative. The simulation of jet-wing configuration was performed in the EU-funded project “JERONIMO” (ACP2-GA-2012-314692-JERONIMO). The authors would like to thank Drs Jack Lawerence and Anderson Proneca for providing the experimental measurement to validate the simulation of jet-plate configuration

Status of the TRIGA shipments to the INEEL from Asia

This paper will report on preparations being made for returning Training, Research, Isotope, General Atomics (TRIGA) foreign research reactor (FRR) spent fuel from South Korea and Indonesia to the Idaho National Engineering and Environmental Laboratory (INEEL). The roles of US Department of Energy, INEEL, and NAC International in implementing a safe shipment are provided. Special preparations necessitated by making a shipment through a west coast port of the US to the INEEL will be explained. The institutional planning and actions needed to meet the unique political and operational environment for making a shipment from Asia to INEEL will be discussed. Facility preparation at both the INEEL and the FRRs is discussed. Cask analysis needed to properly characterize the various TRIGA configurations, compositions, and enrichments is discussed. Shipping preparations will include an explanation of the integrated team of spent fuel transportation specialists, and shipping resources needed to retrieve the fuel from foreign research reactor sites and deliver it to the INEEL

Efficient preprocessing of complex geometries for CFD simulations

Higher Education Commission, Pakistan; the Rolls-Royce pl

Artificial Compressibility Approaches in Flux Reconstruction for Incompressible Viscous Flow Simulations

Copyright © 2021 The Author(s). Several competing artificial compressibility methods for the incompressible flow equations are examined using the high-order flux reconstruction method. The established artificial compressibility method (ACM) of \citet{Chorin1967} is compared to the alternative entropically damped (EDAC) method of \citet{Clausen2013}, as well as an ACM formulation with hyperbolised diffusion. While the former requires the solution to be converged to a divergence free state at each physical time step through pseudo iterations, the latter can be applied explicitly. We examine the sensitivity of both methods to the parameterisation for a series of test cases over a range of Reynolds numbers. As the compressibility is reduced, EDAC is found to give linear improvements in divergence whereas ACM yields diminishing returns. For the Taylor--Green vortex, EDAC is found to perform well; however on the more challenging circular cylinder at $Re=3900$, EDAC gives rise to early transition of the free shear-layer and over-production of the turbulence kinetic energy. This is attributed to the spatial pressure fluctuations of the method. Similar behaviour is observed for an aerofoil at $Re=60,000$ with an attached transitional boundary layer. It is concluded that hyperbolic diffusion of ACM can be beneficial but at the cost of case setup time, and EDAC can be an efficient method for incompressible flow. However, care must be taken as pressure fluctuations can have a significant impact on physics and the remedy causes the governing equation to become overly stiff.https://arxiv.org/abs/2111.07915v

Imidazoline 2 binding sites reflecting astroglia pathology in Parkinson's disease:an in vivo11C-BU99008 PET study

Astroglia are multifunctional cells that regulate neuroinflammation and maintain homeostasis within the brain. Astroglial a-synuclein-positive cytoplasmic accumulations have been shown post-mortem in patients with Parkinson's disease and therefore astroglia may play an important role in the initiation and progression of Parkinson's disease. Imidazoline 2 binding sites are expressed on activated astroglia in the cortex, hippocampus, basal ganglia and brainstem; therefore, by measuring imidazoline 2 binding site levels we can indirectly evaluate astrogliosis in patients with Parkinson's disease. Here, we aimed to evaluate the role of astroglia activation in vivo in patients with Parkinson's disease using 11C-BU99008 PET, a novel radioligand with high specificity and selectivity for imidazoline 2 binding sites. Twenty-two patients with Parkinson's disease and 14 healthy control subjects underwent 3 T MRI and a 120-min 11C-BU99008 PET scan with volume of distribution (V T) estimated using a two-tissue compartmental model with a metabolite corrected arterial plasma input function. Parkinson's disease patients were stratified into early (n = 8) and moderate/advanced (n = 14) groups according to disease stage. In early Parkinson's disease, increased 11C-BU99008 V T uptake was observed in frontal (P = 0.022), temporal (P = 0.02), parietal (P = 0.026) and occipital (P = 0.047) cortical regions compared with healthy controls. The greatest 11C-BU99008 V T increase in patients with early Parkinson's disease was observed in the brainstem (52%; P = 0.018). In patients with moderate/advanced Parkinson's disease, loss of 11C-BU99008 V T was observed across frontal (P = 0.002), temporal (P &lt; 0.001), parietal (P = 0.039), occipital (P = 0.024), and insula (P &lt; 0.001) cortices; and in the subcortical regions of caudate (P &lt; 0.001), putamen (P &lt; 0.001) and thalamus (P &lt; 0.001); and in the brainstem (P = 0.018) compared with healthy controls. In patients with Parkinson's disease, loss of 11C-BU99008 V T in cortical regions, striatum, thalamus and brainstem correlated with longer disease duration (P &lt; 0.05) and higher disease burden scores, measured with Movement Disorder Society Unified Parkinson's Disease Rating Scale (P &lt; 0.05). In the subgroup of patients with moderate/advanced Parkinson's disease, loss of 11C-BU99008 V T in the frontal (r = 0.79; P = 0.001), temporal (r = 0.74; P = 0.002) and parietal (r = 0.89; P &lt; 0.001) cortex correlated with global cognitive impairment. This study demonstrates in vivo the role of astroglia in the initiation and progression of Parkinson's disease. Reactive astroglia observed early in Parkinson's disease could reflect a neuroprotective compensatory mechanisms and pro-inflammatory upregulation in response to a-synuclein accumulation. However, as the disease progresses and significant neurodegeneration occurs, astroglia lose their reactive function and such loss in the cortex has clinical relevance in the development of cognitive impairment. </p