Main results of the analysis of the HOMER Lagrangian Particle Tracking and Data Assimilation database

In this work, we extend the analysis of Lagrangian Particle Tracking (LPT) and Data Assimilation (DA) algorithms, presented at the ISPIV21 conference, to the case of a turbulent wall-bounded flow interacting with a moving panel. The work is conducted within the European project HOMER and the data is processed by the partners of the project consortium. A synthetic experiment is performed that reproduces the air flow around a cylinder in ground effect, whereby a flexible panel is placed undergoing periodic oscillations. The database comprises two different panel's materials, namely metal and rubber, different marker densities on the panel’s surface and different concentrations of tracer particles in the flow. Images of the flow tracers and of the surface markers are acquired either with a fourcamera volumetric imaging setup or with a dual setup composed of four LPT cameras and two Digital Image Correlation (DIC) cameras. Additionally, three image acquisition modes are simulated, namely time-resolved, twopulse and four-pulse. The data are analyzed in terms of percentages of correctly reconstructed, missed and ghost particles, errors of the measured particles’ positions, velocities and accelerations (LPT analysis) and errors of the reconstructed flow fields, panel’s positions and surface pressures (DA analysis)

Main results of the first Lagrangian Particle Tracking Challenge

This work presents the main results of the first Lagrangian Particle Tracking challenge, conducted within the framework of the European Union’s Horizon 2020 project HOMER (Holistic Optical Metrology for Aero-Elastic Research), grant agreement number 769237. The challenge, jointly organised by the research groups of DLR, ONERA and TU Delft, considered a synthetic experiment reproducing the wall-bounded flow in the wake of a cylinder which was simulated by LES. The participants received the calibration images and sets of particle images acquired by four virtual cameras, and were asked to produce as output the particles positions, velocities and accelerations (when possible) at a specific time instant. Four different image acquisition strategies were addressed, namely two-pulse (TP), four-pulse (FP) and time-resolved (TR) acquisitions, each with varying tracer particle concentrations (or number of particles per pixel, ppp). The participants’ outputs were analysed in terms of percentages of correctly reconstructed particles, missed particles, ghost particles, correct tracks and wrong tracks, as well as in terms of position, velocity and acceleration errors, along with their distributions. The analysis of the results showed that the best-performing algorithms allow for a correct reconstruction of more than 99% of the tracer particles with positional errors below 0.1 pixels even at ppp values exceeding 0.15, whereas other algorithms are more prone to the presence of ghost particles already for ppp < 0.1. While the velocity errors remained contained within a small percentage of the bulk velocity, acceleration errors as large as 50% of the actual acceleration magnitude were retrieved

Main results of the first Data Assimilation Challenge

This work presents the main results of the first Lagrangian Particle Tracking challenge, conducted within the framework of the European Union’s Horizon 2020 project HOMER (Holistic Optical Metrology for Aero-Elastic Research), grant agreement number 769237. The challenge, jointly organised by the research groups of DLR, ONERA and TU Delft, considered a synthetic experiment reproducing the wall-bounded flow in the wake of a cylinder which was simulated by LES. The participants received the calibration images and sets of particle images acquired by four virtual cameras, and were asked to produce as output the particles positions, velocities and accelerations (when possible) at a specific time instant. Four different image acquisition strategies were addressed, namely two-pulse (TP), four-pulse (FP) and time-resolved (TR) acquisitions, each with varying tracer particle concentrations (or number of particles per pixel, ppp). The participants’ outputs were analysed in terms of percentages of correctly reconstructed particles, missed particles, ghost particles, correct tracks and wrong tracks, as well as in terms of position, velocity and acceleration errors, along with their distributions. The analysis of the results showed that the best-performing algorithms allow for a correct reconstruction of more than 99% of the tracer particles with positional errors below 0.1 pixels even at ppp values exceeding 0.15, whereas other algorithms are more prone to the presence of ghost particles already for ppp < 0.1. While the velocity errors remained contained within a small percentage of the bulk velocity, acceleration errors as large as 50% of the actual acceleration magnitude were retrieved

Interleukin‑6 signalling as a valuable cornerstone for molecular medicine (Review)

The biological abilities of interleukin‐6 (IL‐6) have been under investigation for nearly 40 years. IL‐6 works through an interaction with the complex peptide IL‐6 receptor (IL‐6R). IL‐6 is built with four α‐chain nanostructures, while two different chains, IL‐6Rα (gp80) and gp130/IL6β (gp130), are included in IL‐6R. The three‐dimensional shapes of the six chains composing the IL‐6/IL‐6R complex are the basis for the nanomolecular roles of IL‐6 signalling. Genes, pseu‐ dogenes and competitive endogenous RNAs of IL‐6 have been identified. In the present review, the roles played by miRNA in the post‐transcriptional regulation of IL‐6 expression are evaluated. mRNAs are absorbed via the ‘sponge’ effect to dynamically balance mRNA levels and this has been assessed with regard to IL‐6 transcription efficiency. According to current knowledge on molecular and nanomolecular structures involved in active IL‐6 signalling, two different IL‐6 models have been proposed. IL‐6 mainly has functions in inflamma‐ tory processes, as well as in cognitive activities. Furthermore, the abnormal production of IL‐6 has been found in patients with severe acute respiratory syndrome coronavirus 2 (SARS‐coV‐2; also known as cOVId‐19). In the present review, both inflammatory and cognitive IL‐6 models were analysed by evaluating the cytological and histological loca‐ tions of IL‐6 signalling. The goal of this review was to illustrate the roles of the classic and trans‐signalling IL‐6 pathways in endocrine glands such as the thyroid and in the central nervous system. Specifically, autoimmune thyroid diseases, disorders of cognitive processes and SARS‐coV‐2 virus infection have been examined to determine the contribution of IL‐6 to these disease states

Introducing the HOMER numerical benchmark: LPT and DA datasets of turbulent flow over moving panels

Following the First Challenge on Lagrangian Particle Tracking (LPT) and Data Assimilation (DA), organized in 2020 (see http://cfdforpiv.dlr.de/ and Leclaire et al.), the next numerical benchmark activities within the HOMER project take as their objectives to assess LPT and DA algorithms in a fluid-structure interaction situation. The physical situation that has been retained is that of a turbulent wall-bounded flow, with a part of the wall consisting of a flexible panel entrained in forced oscillation, a situation which has been investigated experimentally within one of the HOMER tasks, led by the Delft University of Technology. In the numerical benchmark, a spanwise infinite cylinder has been added within the turbulent boundary layer, in order to enhance the intensity of turbulent fluctuations in the flow, and of pressure fluctuations at the wall

Time-resolved image analysis for turbulent flows Conference paper

International audienceClassical Particle Image Velocimetry (PIV) uses two representations of the particle image distribution to determine the displacement of the particle image pattern by spatial cross-correlation. The accuracy and the robustness are however limited by the fact that only two representations at t and t +Δt are present. Thus, only a first order approximation of the velocity can be estimated. To enhance the precision in estimating the flow velocity, multi-pulse or multi-frame techniques were already investigated in the early days of PIV as summarized by Adrian (1991) and Hain and Kähler (2007). Today with the increasing power of high repetition rate lasers and enhanced sensitivity of the digital cameras it is possible to have a time-resolved sampling of even aerodynamically relevant flows, were the particles are much smaller than in water flows. The easiest sampling scheme is the equidistant temporal sampling of the particle distribution such that a robust displacement estimation between successive frames (1+2, 2+3, 3+4, ...) is possible. This so called TR-PIV does not only provide the possibility to follow the evolution of flow structures, but offers the ability to strengthen the data processing by using information from more than two frames (e.g. Hain and Kähler, 2007). Within the AFDAR-project (Advanced Flow Diagnostics for Aeronautical Research funded by the European Union) different approaches to evaluat time-resolved image series were developed by the different groups. The current contribution focuses on the comparison of the algorithms that were developed within the AFDAR project by the partners of the consortium. To verify and validate the performance of the different algorithms a short image sequence of an experiment on the flow over periodic hills (ERCOFTAC test case 81) was provided to all partners and evaluated with the current version of the algorithms

First Lagrangian Particle Tracking and Data Assimilation challenge: datasets description and evolution to an open online benchmark

In the last decade, Lagrangian Particle Tracking (LPT) has emerged as one of the leading measurement techniques for the quantitative determination of fluid flows in three-dimensional domains (see e.g. Schanz et al., 2016), due to its accuracy in reconstructing particles velocities and material accelerations. Due to the scattered nature of the obtained result, at the particles positions only, significant research efforts have also been placed in the development of dedicated Data Assimilation (DA) techniques, aiming at finally reconstructing full 3D velocity and pressure fields on regular Cartesian grids (see, e.g., Schneiders et al. 2016)

Circulating Vitamin D levels status and clinical prognostic indices in COVID-19 patients

BACKGROUND: Several immune mechanisms activate in COVID-19 pathogenesis. Usually, coronavirus infection is characterized by dysregulated host immune responses, interleukine-6 increase, hyper-activation of cytotoxic CD8 T lymphocytes. Interestingly, Vitamin D deficiency has been often associated with altered immune responses and infections. In the present study, we evaluated Vitamin D plasma levels in patients affected with different lung involvement during COVID-19 infection.METHODS: Lymphocyte phenotypes were assessed by flow cytometry. Thoracic CT scan involvement was obtained by an image analysis program.RESULTS: Vitamin D levels were deficient in (80%) of patients, insufficient in (6.5%) and normal in (13.5%). Patients with very low Vitamin D plasma levels had more elevated D-Dimer values, a more elevated B lymphocyte cell count, a reduction of CD8+T lymphocytes with a low CD4/CD8 ratio, more compromised clinical findings (measured by LIPI and SOFA scores) and thoracic CT scan involvement.CONCLUSIONS: Vitamin D deficiency is associated with compromised inflammatory responses and higher pulmonary involvement in COVID-19 affected patients. Vitamin D assessment, during COVID-19 infection, could be a useful analysis for possible therapeutic interventions.TRIAL REGISTRATION: 'retrospectively registered'

High-resolution turbofan intake flow characterization by automated stereoscopic-PIV in an industrial wind tunnel environment

Unsteady inlet flow distortion can influence the stability and performance of any propulsion system, in particular for more novel, short and slim intakes of future aero-engine configurations. As such, the requirement for measurement methods able to provide high spatial resolution data is important to aid the understanding of these flow fields. This work presents flow field characterisations at a crossflow plane within a short aeroengine intake using stereoscopic particle image velocimetry (SPIV). A series of tests were conducted across a range of crosswind and high angle of attack conditions for a representative short and slim aspirated intake configuration at two operating points in terms of mass flow rate. The velocity maps were measured at a crossflow plane within the intake at an axial position L/D = 0.058 from where a fan is expected to be installed. The diameter of the measurement plane was 250 mm, and the final spatial resolution of the velocity fields had a vector pitch of 1.5 mm which is at least two orders of magnitude richer than conventional pressure-based distortion measurements. The work demonstrates the ability to perform robust non-intrusive flow measurements within modern intake systems in an industrial wind tunnel environment across a wide range of operating conditions; hence, it is suggested that SPIV can potentially become part of standard industrial testing. The results provide rich datasets that can notably improve our understanding of unsteady distortions and influence the design of novel, closely coupled engine-intake systems