| 1. |
- Pihl, E., et al.
(författare)
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Ten new insights in climate science 2020- A horizon scan
- 2020
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Ingår i: Global Sustainability. - : Cambridge University Press. - 2059-4798.
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Tidskriftsartikel (refereegranskat)abstract
- Non-technical summary We summarize some of the past year's most important findings within climate change-related research. New research has improved our understanding of Earth's sensitivity to carbon dioxide, finds that permafrost thaw could release more carbon emissions than expected and that the uptake of carbon in tropical ecosystems is weakening. Adverse impacts on human society include increasing water shortages and impacts on mental health. Options for solutions emerge from rethinking economic models, rights-based litigation, strengthened governance systems and a new social contract. The disruption caused by COVID-19 could be seized as an opportunity for positive change, directing economic stimulus towards sustainable investments. Technical summary A synthesis is made of ten fields within climate science where there have been significant advances since mid-2019, through an expert elicitation process with broad disciplinary scope. Findings include: (1) a better understanding of equilibrium climate sensitivity; (2) abrupt thaw as an accelerator of carbon release from permafrost; (3) changes to global and regional land carbon sinks; (4) impacts of climate change on water crises, including equity perspectives; (5) adverse effects on mental health from climate change; (6) immediate effects on climate of the COVID-19 pandemic and requirements for recovery packages to deliver on the Paris Agreement; (7) suggested long-term changes to governance and a social contract to address climate change, learning from the current pandemic, (8) updated positive cost-benefit ratio and new perspectives on the potential for green growth in the short- A nd long-term perspective; (9) urban electrification as a strategy to move towards low-carbon energy systems and (10) rights-based litigation as an increasingly important method to address climate change, with recent clarifications on the legal standing and representation of future generations. Social media summary Stronger permafrost thaw, COVID-19 effects and growing mental health impacts among highlights of latest climate science.
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| 2. |
- Bailey, S. C. C., et al.
(författare)
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Obtaining accurate mean velocity measurements in high Reynolds number turbulent boundary layers using Pitot tubes
- 2013
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Ingår i: Journal of Fluid Mechanics. - : Cambridge University Press (CUP). - 0022-1120 .- 1469-7645. ; 715, s. 642-670
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Tidskriftsartikel (refereegranskat)abstract
- This article reports on one component of a larger study on measurement of the zero-pressure-gradient turbulent flat plate boundary layer, in which a detailed investigation was conducted of the suite of corrections required for mean velocity measurements performed using Pitot tubes. In particular, the corrections for velocity shear across the tube and for blockage effects which occur when the tube is in close proximity to the wall were investigated using measurements from Pitot tubes of five different diameters, in two different facilities, and at five different Reynolds numbers ranging from Reθ = 11 100 to 67 000. Only small differences were found amongst commonly used corrections for velocity shear, but improvements were found for existing near-wall proximity corrections. Corrections for the nonlinear averaging of the velocity fluctuations were also investigated, and the results compared to hot-wire data taken as part of the same measurement campaign. The streamwise turbulence-intensity correction was found to be of comparable magnitude to that of the shear correction, and found to bring the hot-wire and Pitot results into closer agreement when applied to the data, along with the other corrections discussed and refined here.
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| 5. |
- Alfredsson, Bo, et al.
(författare)
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Low temperature creep in a high strength roller bearing steel
- 2016
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Ingår i: Mechanics of materials. - : Elsevier. - 0167-6636 .- 1872-7743. ; 100, s. 109-125
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Tidskriftsartikel (refereegranskat)abstract
- Noticeable low temperature creep was established for a bainitic and a martensitic microstructure of the 100CrMnMo8 high strength roller bearing steel. The response revealed primary creep that differed between the microstructures, following a power law for martensite and the logarithmic description for bainite. The detected creep was pressure sensitive, higher in tension than in compression for the same stress level, following the strength differential effect (SDE) at material yielding. Two models were proposed where the stress variable for the pressure effect was based on the Drucker-Prager yield function and deviatoric creep strains were derived from a non-associated von Mises potential. Model parameters were determined from experimental series on the respective microstructure. When the models were evaluated against the experiments the accuracy was of the same order as the effects of different heat treatment batches and different load application rates. The importance of different material parameters in the descriptions was discussed.
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| 6. |
- Alfredsson, Bo, et al.
(författare)
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Propagation of physically short cracks in a bainitic high strength bearing steel due to fatigue load
- 2016
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Ingår i: International Journal of Fatigue. - : Elsevier BV. - 0142-1123 .- 1879-3452. ; 90, s. 166-180
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Tidskriftsartikel (refereegranskat)abstract
- Physically short cracks in a bainitic high strength bearing steel were fatigue loaded. The rapid propagation rate of early open short cracks agreed with that of long closure free cracks. After some rapid growth, the short cracks entered a transition period to the rate of growth limited long cracks. Potential drop showed that the short cracks were open to the tip throughout the growth sequence, which excluded crack face closure in the wake as the growth limiting mechanism in this material. Instead the short crack effect was related to residual stresses and other mechanisms at the crack tip. Crack manufacturing procedures were determined for straight long and short start cracks in the present material. LEFM with effective material parameters and limit compensation predicted the short crack lives.
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| 7. |
- Alfredsson, Eva C., et al.
(författare)
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Prospects for economic growth in the 21st century : A survey covering mainstream, heterodox and scientifically oriented perspectives
- 2017
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Ingår i: Economic Issues. - : ECONOMIC ISSUES EDUCATION FUND. - 1363-7029. ; 22, s. 65-87
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Tidskriftsartikel (refereegranskat)abstract
- Despite the importance of economic growth for the current economy, business and societal planning there are few long-term growth projections undertaken. There is, however, a vivid debate on what is called the 'new normal' - secular stagnation - which is undertaken within academic disciplines. This overview covers mainstream, heterodox and scientifically oriented economic perspectives on the prospects for economic growth in the 21st century. The survey shows that existing long-term projections and scenarios indicate growth rates ranging from around half a percentage point less than during the last two decades (projected by the Organisation for Economic Co-operation and Development, OECD), to dramatically lower growth rates). Differences stem from different perspectives on the determinants of economic growth and the potential for improvements in productivity. Headwinds are: an aging population, especially in OECD countries; resource constraints, including energy; increasing environmental costs in particular due to the consequences of climate change; overaccumulation; increasing income differences; and declining social capital. One conclusion is that policymaking based on the assumption that economic growth will continue at pre-crisis levels is unwise and risky.
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| 8. |
- Alfredsson, P. Henrik, et al.
(författare)
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Rotation Effects on Wall-Bounded Flows : Some Laboratory Experiments
- 2014
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Ingår i: Modeling Atmospheric and Oceanic Flows: Insights from Laboratory Experiments and Numerical Simulations. - Hoboken, NJ : Wiley-Blackwell. - 9781118856024 - 9781118855935 ; , s. 83-100
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter focuses on three different categories: (1) system rotation vector parallel to mean-flow vorticity; (2) flows set up by the rotation of one or more boundaries; and (3) system rotation aligned with the mean-flow direction. The flows in the different categories above differ with respect to their geometry but, more importantly, in how rotation affects them. The chapter focuses on three different flows that are relatively amenable to laboratory investigation, one from each category described above: One is plane Couette flow undergoing system rotation about an axis normal to the mean flow, another is the von Kármán boundary layer flow, and the third is axially rotating pipe flow. It defines important nondimensional parameters that govern them and discuss some of their interesting flow features in various parameter ranges. Various experimental realizations of the three different flow systems are described and considerations and limitations regarding the laboratory systems are discussed.
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| 9. |
- Alfredsson, P. Henrik, et al.
(författare)
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Turbulent boundary layers over flat plates and rotating disks-The legacy of von Karman : A Stockholm perspective
- 2013
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Ingår i: European journal of mechanics. B, Fluids. - : Elsevier BV. - 0997-7546 .- 1873-7390. ; 40, s. 17-29
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Tidskriftsartikel (refereegranskat)abstract
- Many of the findings and ideas of von Karman are still of interest to the fluid dynamics community. For instance, his result that the mean velocity distribution in turbulent flows has a logarithmic behavior with respect to the distance from the centreline is still a cornerstone for everybody working in wall-bounded turbulence and was first presented to an international audience in Stockholm at the Third International Congress for Applied Mechanics in 1930. In this paper we discuss this result and also how the so-called von Karman constant can be determined in a new simple way. We also discuss the possibility of a second (outer) maximum of the streamwise velocity fluctuations, a result that was implicit in some of the assumptions proposed by von Karman.
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| 10. |
- Appelquist, Elinor, et al.
(författare)
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Investigation of the Global Instability of the Rotating-disk Boundary Layer
- 2015
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Ingår i: Procedia IUTAM. - : Elsevier. - 2210-9838. ; , s. 321-328
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Konferensbidrag (refereegranskat)abstract
- The development of the flow over a rotating disk is investigated by direct numerical simulations using both the linearized and fully nonlinear incompressible Navier-Stokes equations. These simulations allow investigation of the transition to turbulence of the realistic spatially-developing boundary layer. The current research aims to elucidate further the global linear stability properties of the flow, and relate these to local analysis and discussions in literature. An investigation of the nonlinear upstream (inward) influence is conducted by simulating a small azimuthal section of the disk (1/68). The simulations are initially perturbed by an impulse disturbance where, after the initial transient behaviour, both the linear and nonlinear simulations show a temporally growing upstream mode. This upstream global mode originates in the linear case close to the end of the domain, excited by an absolute instability at this downstream position. In the nonlinear case, it instead originates where the linear region ends and nonlinear harmonics enter the flow field, also where an absolute instability can be found. This upstream global mode can be shown to match a theoretical mode from local linear theory involved in the absolute instability at either the end of the domain (linear case) or where nonlinear harmonics enter the field (nonlinear case). The linear simulation grows continuously in time whereas the nonlinear simulation saturates and the transition to turbulence moves slowly upstream towards smaller radial positions asymptotically approaching a global upstream mode with zero temporal growth rate, which is estimated at a nondimensional radius of 582.
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