Comparative analysis of tip vortex flow using RANS and LES

The current study focuses on the numerical analysis of tip vortex flows, with the emphasis n the investigation of turbulence modelling effects on tip vortex prediction. The analysis includes comparison of RANS and LES methods at two different mesh resolutions. Implicit LES, ILES, modelling is employed here to mimic the turbulent viscosity. In RANS, the two equation k-ω SST model is adopted. In order to also address possible benefits of using streamline curvature variations in RANS, two curvature correction methods proposed for k-ω SST are tested, and compared. ILES results show very good agreement with the experimental observations. The predicted vortex in ILES is also stronger than RANS predictions. ILES has predicted accelerated vortex core axial velocity very well, while tested RANS models under predict the axial velocity. Adoption of curvature correction has not improved the tip vortex prediction, even though it has reduced the turbulent viscosity at the vortex core

Propeller Tip Vortex Mitigation By Roughness Application

In this study, the application of surface roughness on model and full scale marine propellers in order to mitigate tip vortex cavitation is evaluated. To model the turbulence, SST kOmegamodel along with a curvature correction is employed to simulate the flow on an appropriate grid resolution for tip vortex propagation, at least 32 cells per vortex diameter according to our previous guidelines. The effect of roughness is modeled by modified wall functions. The analysis focuses on two types of vortices appearing on marine propellers: tip vortices developing in lower advance ratio numbers and leading-edge tip vortices developing in higher advance ratio numbers. It is shown that as the origin and formation of these two types of vortices differ, different roughness patterns are needed to mitigate them with respect to performance degradation of propeller performance. Our findings clarify that the combination of having roughness on the blade tip and a limited area on the leading edge is the optimum roughness pattern where a reasonable balance between tip vortex cavitation mitigation and performance degradation can be achieved. This pattern in model scale condition leads to an average TVC mitigation of 37% with an average performance degradation of 1.8% while in full scale condition an average TVC mitigation of 22% and performance degradation of 1.4% are obtained

Experimental Analysis of Tip Vortex Cavitation Mitigation By Controlled Surface Roughness

This study presents results of experiments where roughness applications are evaluated in delaying the tip vortex cavitation inception of an elliptical foil. High-speed video recordings and Laser Doppler Velocimetry (LDV) measurements are employed to provide further details on the cavitation behaviour and tip vortex flow properties in different roughness pattern configurations. The angular momentum measurements of the vortex core region at one chord length downstream of the tip indicate that roughness leads to a lower angular momentum compared to the smooth foil condition while the vortex core radius remains similar in the smooth and roughened conditions. The observations show that the cavitation number for tip vortex cavitation inception is reduced by 33 % in the optimized roughness pattern compared to the smooth foil condition where the drag force increase is observed to be around 2 %. During the tests, no obvious differences in the cavitation inception properties of uniform and non-uniform roughness distributions are observed. However, the drag force is found to be higher with a non-uniform roughness distribution

HRS white paper on clinical utilization of digital health technology.

This collaborative statement from the Digital Health Committee of the Heart Rhythm Society provides everyday clinical scenarios in which wearables may be utilized by patients for cardiovascular health and arrhythmia management. We describe herein the spectrum of wearables that are commercially available for patients, and their benefits, shortcomings and areas for technological improvement. Although wearables for rhythm diagnosis and management have not been examined in large randomized clinical trials, undoubtedly the usage of wearables has quickly escalated in clinical practice. This document is the first of a planned series in which we will update information on wearables as they are revised and released to consumers

Critical appraisal of technologies to assess electrical activity during atrial fibrillation: a position paper from the European Heart Rhythm Association and European Society of Cardiology Working Group on eCardiology in collaboration with the Heart Rhythm Society, Asia Pacific Heart Rhythm Society, Latin American Heart Rhythm Society and Computing in Cardiology

We aim to provide a critical appraisal of basic concepts underlying signal recording and processing technologies applied for (i) atrial fibrillation (AF) mapping to unravel AF mechanisms and/or identifying target sites for AF therapy and (ii) AF detection, to optimize usage of technologies, stimulate research aimed at closing knowledge gaps, and developing ideal AF recording and processing technologies. Recording and processing techniques for assessment of electrical activity during AF essential for diagnosis and guiding ablative therapy including body surface electrocardiograms (ECG) and endo- or epicardial electrograms (EGM) are evaluated. Discussion of (i) differences in uni-, bi-, and multi-polar (omnipolar/Laplacian) recording modes, (ii) impact of recording technologies on EGM morphology, (iii) global or local mapping using various types of EGM involving signal processing techniques including isochronal-, voltage- fractionation-, dipole density-, and rotor mapping, enabling derivation of parameters like atrial rate, entropy, conduction velocity/direction, (iv) value of epicardial and optical mapping, (v) AF detection by cardiac implantable electronic devices containing various detection algorithms applicable to stored EGMs, (vi) contribution of machine learning (ML) to further improvement of signals processing technologies. Recording and processing of EGM (or ECG) are the cornerstones of (body surface) mapping of AF. Currently available AF recording and processing technologies are mainly restricted to specific applications or have technological limitations. Improvements in AF mapping by obtaining highest fidelity source signals (e.g. catheter–electrode combinations) for signal processing (e.g. filtering, digitization, and noise elimination) is of utmost importance. Novel acquisition instruments (multi-polar catheters combined with improved physical modelling and ML techniques) will enable enhanced and automated interpretation of EGM recordings in the near future

2021 ISHNE/ HRS/ EHRA/ APHRS collaborative statement on mHealth in Arrhythmia Management: Digital Medical Tools for Heart Rhythm Professionals: From the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia Pacific Heart Rhythm Society.

This collaborative statement from the International Society for Holter and Noninvasive Electrocardiology/ Heart Rhythm Society/ European Heart Rhythm Association/ Asia Pacific Heart Rhythm Society describes the current status of mobile health ("mHealth") technologies in arrhythmia management. The range of digital medical tools and heart rhythm disorders that they may be applied to and clinical decisions that may be enabled are discussed. The facilitation of comorbidity and lifestyle management (increasingly recognized to play a role in heart rhythm disorders) and patient self-management are novel aspects of mHealth. The promises of predictive analytics but also operational challenges in embedding mHealth into routine clinical care are explored

Integrating new approaches to atrial fibrillation management: the 6th AFNET/EHRA Consensus Conference.

There are major challenges ahead for clinicians treating patients with atrial fibrillation (AF). The population with AF is expected to expand considerably and yet, apart from anticoagulation, therapies used in AF have not been shown to consistently impact on mortality or reduce adverse cardiovascular events. New approaches to AF management, including the use of novel technologies and structured, integrated care, have the potential to enhance clinical phenotyping or result in better treatment selection and stratified therapy. Here, we report the outcomes of the 6th Consensus Conference of the Atrial Fibrillation Network (AFNET) and the European Heart Rhythm Association (EHRA), held at the European Society of Cardiology Heart House in Sophia Antipolis, France, 17-19 January 2017. Sixty-two global specialists in AF and 13 industry partners met to develop innovative solutions based on new approaches to screening and diagnosis, enhancing integration of AF care, developing clinical pathways for treating complex patients, improving stroke prevention strategies, and better patient selection for heart rate and rhythm control. Ultimately, these approaches can lead to better outcomes for patients with AF