Fluid Dynamics of Axial Turbomachinery: Blade- and Stage-Level Simulations and Models

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Richard D. Sandberg ◽  
Vittorio Michelassi
Keyword(s):  
Fluid Dynamics ◽  
Fluid Mechanics ◽  
Gas Turbines ◽  
High Efficiency ◽  
Annual Review ◽  
Publication Date ◽  
Complex Flow ◽  
Key Factor ◽  
Flow Phenomena ◽  
The Rich

The current generation of axial turbomachines are the culmination of decades of experience, and detailed understanding of the underlying flow physics has been a key factor for achieving high efficiency and reliability. Driven by advances in numerical methods and relentless growth in computing power, computational fluid dynamics has increasingly provided insights into the rich fluid dynamics involved and how it relates to loss generation. This article presents some of the complex flow phenomena occurring in bladed components of gas turbines and illustrates how simulations have contributed to their understanding and the challenges they pose for modeling. The interaction of key aerodynamic features with deterministic unsteadiness, caused by multiple blade rows, and stochastic unsteadiness, i.e., turbulence, is discussed. High-fidelity simulations of increasingly realistic configurations and models improved with help of machine learning promise to further grow turbomachinery performance and reliability and, thus, help fluid mechanics research have a greater industrial impact. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 54 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Particle-Laden Turbulence: Progress and Perspectives

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Luca Brandt ◽  
Filippo Coletti
Keyword(s):  
Fluid Dynamics ◽  
Fluid Mechanics ◽  
Online Publication ◽  
Granular Media ◽  
Finite Size ◽  
Spherical Particles ◽  
Annual Review ◽  
Publication Date ◽  
Zero Gravity ◽  
Inertial Particles

This review is motivated by the fast progress in our understanding of the physics of particle-laden turbulence in the last decade, partly due to the tremendous advances of measurement and simulation capabilities. The focus is on spherical particles in homogeneous and canonical wall-bounded flows. The analysis of recent data indicates that conclusions drawn in zero gravity should not be extrapolated outside of this condition, and that the particle response time alone cannot completely define the dynamics of finite-size particles. Several breakthroughs have been reported, mostly separately, on the dynamics and turbulence modifications of small inertial particles in dilute conditions and of large weakly buoyant spheres. Measurements at higher concentrations, simulations fully resolving smaller particles, and theoretical tools accounting for both phases are needed to bridge this gap and allow for the exploration of the fluid dynamics of suspensions, from laminar rheology and granular media to particulate turbulence. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 54 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Using FlowLab, A Computational Fluid Dynamics Tool, to Facilitate the Teaching of Fluid Mechanics

2004 ◽  
Author(s):  
John Cimbala ◽  
Shane Moeykens ◽  
Ashish Kulkarni ◽  
Ajay Parihar
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Mechanics ◽  
Learning Experience ◽  
Learning Objective ◽  
Structured Learning ◽  
Complex Flow ◽  
Homework Problem ◽  
Flow Phenomena ◽  
Computer Based

Traditional fluid mechanics textbooks are generally written with problem sets comprised of closed, analytical solutions. However, it is recognized that complex flow fields are not easily represented in terms of a closed solution. A tool that allows the student to visualize complex flow phenomena in a virtual environment can significantly enhance the learning experience. Such a visualization tool allows the student to perform open-ended analyses and explore cause-effect relationships. Computational fluid dynamics (CFD) brings these benefits into the learning environment for fluid mechanics. With these benefits in mind, FlowLab was introduced by Fluent Inc. in 2002. FlowLab may be described as a virtual fluids laboratory - a computer-based analysis and visualization package. Using this software, students solve predefined CFD exercises, either as homework or in a supervised laboratory or practicum setting. Predefined exercises facilitate the teaching of fluid mechanics and provide students with hands-on CFD experience, while avoiding many of the difficulties associated with learning a generalized CFD package. A new fluid mechanics textbook is scheduled for release in early 2005. This book includes FlowLab as a textbook companion, where student-friendly CFD exercises are employed to convey important concepts to the student. Because of the unique design of end-of-chapter homework problems in this book and the intimate coupling between these problems and the CFD software, students are introduced to engineering problems and concepts, as well as to CFD, via a structured learning process. The CFD exercises are not meant to stand alone; rather, they are designed to support and emphasize the theory and concepts taught in the textbook, which is the primary learning vehicle. Each homework problem has a specific fluid mechanics learning objective. Through use of the software, a second learning objective is also achieved, namely a CFD objective. The scope, content, and presentation of these CFD exercises are discussed in this paper. Additionally, one of the exercises is explained in detail to show the value of using CFD to teach introductory fluid mechanics to undergraduate engineers.

Flood Inundation Prediction

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Paul D. Bates
Keyword(s):  
Fluid Mechanics ◽  
Land Surface ◽  
High Performance ◽  
Numerical Algorithms ◽  
Economic Damage ◽  
Annual Review ◽  
Publication Date ◽  
Flood Inundation ◽  
Damage Mapping ◽  
Performance Computing

Every year flood events lead to thousands of casualties and significant economic damage. Mapping the areas at risk of flooding is critical to reducing these losses, yet until the last few years such information was available for only a handful of well-studied locations. This review surveys recent progress to address this fundamental issue through a novel combination of appropriate physics, efficient numerical algorithms, high-performance computing, new sources of big data, and model automation frameworks. The review describes the fluid mechanics of inundation and the models used to predict it, before going on to consider the developments that have led in the last five years to the creation of the first true fluid mechanics models of flooding over the entire terrestrial land surface. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 54 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The Visual Opsin Gene Repertoires of Teleost Fishes: Evolution, Ecology, and Function

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Zuzana Musilova ◽  
Walter Salzburger ◽  
Fabio Cortesi
Keyword(s):  
Sensory System ◽  
Photoreceptor Cells ◽  
Opsin Gene ◽  
Annual Review ◽  
Specific Gene ◽  
Publication Date ◽  
Teleost Fishes ◽  
Opsin Genes ◽  
The Rich ◽  
Species Specific

Visual opsin genes expressed in the rod and cone photoreceptor cells of the retina are core components of the visual sensory system of vertebrates. Here, we provide an overview of the dynamic evolution of visual opsin genes in the most species-rich group of vertebrates, teleost fishes. The examination of the rich genomic resources now available for this group reveals that fish genomes contain more copies of visual opsin genes than are present in the genomes of amphibians, reptiles, birds, and mammals. The expansion of opsin genes in fishes is due primarily to a combination of ancestral and lineage-specific gene duplications. Following their duplication, the visual opsin genes of fishes repeatedly diversified at the same key spectral-tuning sites, generating arrays of visual pigments sensitive from the ultraviolet to the red spectrum of the light. Species-specific opsin gene repertoires correlate strongly with underwater light habitats, ecology, and color-based sexual selection. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

In Situ Surface-Enhanced Raman Spectroscopy Characterization of Electrocatalysis with Different Nanostructures

2021 ◽  
Vol 72 (1) ◽  
Author(s):  
Bao-Ying Wen ◽  
Qing-Qi Chen ◽  
Petar M. Radjenovic ◽  
Jin-Chao Dong ◽  
Zhong-Qun Tian ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
High Efficiency ◽  
Spectroscopic Characterization ◽  
Surface Enhanced Raman Spectroscopy ◽  
Annual Review ◽  
Publication Date ◽  
Oxygen Reduction Reactions ◽  
Surface Enhanced ◽  
Surface Enhanced Raman

As energy demands increase, electrocatalysis serves as a vital tool in energy conversion. Elucidating electrocatalytic mechanisms using in situ spectroscopic characterization techniques can provide experimental guidance for preparing high-efficiency electrocatalysts. Surface-enhanced Raman spectroscopy (SERS) can provide rich spectral information for ultratrace surface species and is extremely well suited to studying their activity. To improve the material and morphological universalities, researchers have employed different kinds of nanostructures that have played important roles in the development of SERS technologies. Different strategies, such as so-called borrowing enhancement from shell-isolated modes and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS)-satellite structures, have been proposed to obtain highly effective Raman enhancement, and these methods make it possible to apply SERS to various electrocatalytic systems. Here, we discuss the development of SERS technology, focusing on its applications in different electrocatalytic reactions (such as oxygen reduction reactions) and at different nanostructure surfaces, and give a brief outlook on its development. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 72 is April 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals The Elusive Peace Dividend of Development Policy: From War Traps to Macro Complementarities

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Dominic Rohner ◽  
Mathias Thoenig
Keyword(s):  
Development Policy ◽  
Civil Conflict ◽  
Annual Review ◽  
Publication Date ◽  
Peace Dividend ◽  
Key Factor ◽  
Development Objectives ◽  
Socioeconomic Consequences ◽  
Peace And Development ◽  
Consequences Of Violence

This article reviews the literature on civil conflict and development with a focus on the socioeconomic consequences of violence and on promising policies for fostering peace. We make four main points. First, one of the reasons conflict is still often overlooked as key factor for development is that conflict costs are typically underestimated, in particular the shadow costs of deterrence. Second, there are several types of war traps that hold countries back, both economically and politically. Third, to break these traps, policies must be calibrated to address jointly both poverty and social tensions, as there is a strong macro complementarity between peace and development objectives. We document how single-minded policies that ignore this dual challenge can spectacularly fail, and we discuss in depth a series of particularly promising policies. Fourth, we highlight the increasing potential of novel data collection methodologies and the need for policy evaluation tools in violent contexts. Expected final online publication date for the Annual Review of Economics, Volume 13 is August 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Designing Complex Fluids

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Randy H. Ewoldt ◽  
Chaimongkol Saengow
Keyword(s):  
Fluid Mechanics ◽  
Newtonian Fluid ◽  
Online Publication ◽  
Complex Fluids ◽  
Annual Review ◽  
Publication Date ◽  
Small Step ◽  
Fluid Behavior ◽  
Fluid Properties ◽  
Organizing Principles

Taking a small step away from Newtonian fluid behavior creates an explosion in the range of possibilities. Non-Newtonian fluid properties can achieve diverse flow objectives, but the complexity introduces challenges. We survey useful rheological complexity along with organizing principles and design methods as we consider the following questions: How can non-Newtonian properties be useful? What properties are needed? How can we get those properties? Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 54 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals Fluid mechanics of human fetal right ventricles from image-based computational fluid dynamics using 4D clinical ultrasound scans

2016 ◽  
Vol 311 (6) ◽  
pp. H1498-H1508 ◽  
Author(s):  
Hadi Wiputra ◽  
Chang Quan Lai ◽  
Guat Ling Lim ◽  
Joel Jia Wei Heng ◽  
Lan Guo ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Kinetic Energy ◽  
Fluid Mechanics ◽  
Animal Studies ◽  
Shear Stresses ◽  
Complex Flow ◽  
Congenital Heart Malformations ◽  
Wall Shear ◽  
Dynamics Simulations

There are 0.6–1.9% of US children who were born with congenital heart malformations. Clinical and animal studies suggest that abnormal blood flow forces might play a role in causing these malformation, highlighting the importance of understanding the fetal cardiovascular fluid mechanics. We performed computational fluid dynamics simulations of the right ventricles, based on four-dimensional ultrasound scans of three 20-wk-old normal human fetuses, to characterize their flow and energy dynamics. Peak intraventricular pressure gradients were found to be 0.2–0.9 mmHg during systole, and 0.1–0.2 mmHg during diastole. Diastolic wall shear stresses were found to be around 1 Pa, which could elevate to 2–4 Pa during systole in the outflow tract. Fetal right ventricles have complex flow patterns featuring two interacting diastolic vortex rings, formed during diastolic E wave and A wave. These rings persisted through the end of systole and elevated wall shear stresses in their proximity. They were observed to conserve ∼25.0% of peak diastolic kinetic energy to be carried over into the subsequent systole. However, this carried-over kinetic energy did not significantly alter the work done by the heart for ejection. Thus, while diastolic vortexes played a significant role in determining spatial patterns and magnitudes of diastolic wall shear stresses, they did not have significant influence on systolic ejection. Our results can serve as a baseline for future comparison with diseased hearts.

Mitochondria and Inflammatory Bowel Diseases: Toward a Stratified Therapeutic Intervention

2021 ◽  
Vol 84 (1) ◽  
Author(s):  
Gwo-tzer Ho ◽  
Arianne L. Theiss
Keyword(s):  
Mitochondrial Dysfunction ◽  
Intestinal Inflammation ◽  
Critical Role ◽  
Annual Review ◽  
Publication Date ◽  
Cellular Functions ◽  
Targeted Interventions ◽  
Bowel Diseases ◽  
Key Factor ◽  
Inflammatory Bowel

Mitochondria serve numerous critical cellular functions, rapidly responding to extracellular stimuli and cellular demands while dynamically communicating with other organelles. Mitochondrial function in the gastrointestinal epithelium plays a critical role in maintaining intestinal health. Emerging studies implicate the involvement of mitochondrial dysfunction in inflammatory bowel disease (IBD). This review presents mitochondrial metabolism, function, and quality control that converge in intestinal epithelial stemness, differentiation programs, barrier integrity, and innate immunity to influence intestinal inflammation. Intestinal and disease characteristics that set the stage for mitochondrial dysfunction being a key factor in IBD, and in turn, pathogenic mitochondrial mechanisms influencing and potentiating the development of IBD, are discussed. These findings establish the basis for potential mitochondrial-targeted interventions for IBD therapy. Expected final online publication date for the Annual Review of Physiology, Volume 84 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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