A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

Meeting abstrac

Adverse-Pressure-Gradient Effects on Turbulent Boundary Layers: Statistics and Flow-Field Organization

This manuscripts presents a study on adverse-pressure-gradient turbulent boundary layers under different Reynolds-number and pressure-gradient conditions. In this work we performed Particle Image Velocimetry (PIV) measurements supplemented with Large-Eddy Simulations in order to have a dataset covering a range of displacement-thickness-based Reynolds-number 2300 34000 and values of the Clauser pressure-gradient parameter beta up to 2.4. The spatial resolution limits of PIV for the estimation of turbulence statistics have been overcome via ensemble-based approaches. A comparison between ensemble-correlation and ensemble Particle Tracking Velocimetry was carried out to assess the uncertainty of the two methods. The effects of beta, R e and of the pressure-gradient history on turbulence statistics were assessed. A modal analysis via Proper Orthogonal Decomposition was carried out on the flow fields and showed that about 20% of the energy contribution corresponds to the first mode, while 40% of the turbulent kinetic energy corresponds to the first four modes with no appreciable dependence on beta and R e within the investigated range. The topology of the spatial modes shows a dependence on the Reynolds number and on the pressure-gradient strength, in line with the results obtained from the analysis of the turbulence statistics. The contribution of the modes to the Reynolds stresses and the turbulence production was assessed using a truncated low-order reconstruction with progressively larger number of modes. It is shown that the outer peaks in the Reynolds-stress profiles are mostly due to large-scale structures in the outer part of the boundary layer.CSV acknowledges the financial support from Universidad Carlos III de Madrid within the program “Ayudas para la Movilidad del Programa Propio de Investigación”. RÖ, RV and PS acknowledge the financial support from the Swedish Research Council (VR) and the Knut and Alice Wallenberg Foundation. CSV, SD and AI were partially supported by the COTURB project (Coherent Structures in Wall-bounded Turbulence), funded by the European Research Council (ERC), under grant ERC-2014.AdG-669505. CSV, SD and AI have been partially supported by Grant DPI2016-79401-R funded by the Spanish State Research Agency (SRA) and European Regional Development Fund (ERDF)

Comparative Assessment of Synthetic Turbulence Methods in an Unstructured Compressible Flow Solver

The industrial use of scale-resolving methods in high-Reynolds-number applications (e.g., airplanes) requires efficient hybrid approaches, in which flow regions of interest are resolved by local LES embedded in a global RANS simulation. The transition from RANS to LES has to be augmented by synthetic turbulence to quickly transform the modelled turbulence into realistic velocity fluctuations. For compressible flow solvers such as the DLR-TAU code, the consistent treatment of density and temperature, and the generation of spurious noise need to be considered, as well. Over the last years, different methods for synthetic turbulence Generation have been implemented in the unstructured TAU code: the Synthetic-Eddy Method (SEM), the Divergence-Free SEM, and an extended variant of the Synthetic Turbulence Generator of Shur et al., denoted by Random Velocity Field Generator (RVFG). Their implementations in TAU allow for flexible grid-independent turbulence injection in multiple planes or volumetric regions via forcing source terms in the flow equations. While individual assessments for different flow cases have been conducted before, this paper presents the first systematic comparison of all These methods in TAU for the same test cases in a unified framework, ruling out uncertainties due to numerical and implementation details