Numerical analysis of hydrofoil ventilated cavitation under wave impact

Unsteady ventilated cavitation of a hydrofoil is analyzed with coupling of the perturbed steady two-dimensional incompressible flow of water out of the cavity and the compressible one-dimensional air flow within the cavity. The air flux from cavity at its oscillating tail and along its side boundary with the water is taken into account. The employed equations include air mass conservation law and pressure constancy condition along the cavity in both media. On the cavity boundary, however, the impermeability condition is considered from the water side and the differential momentum equation from the air side. The developed model of ventilated cavitation has been verified with the already published [1] measurements of hydrodynamic loads and their pulsations on the low-drag partially cavitating hydrofoil OK-2003A satisfactory agreement of the computed results with experimental data was manifested. Influence of the wavelength variations and air compressibility on lift and its pulsations were analyzed.http://deepblue.lib.umich.edu/bitstream/2027.42/84258/1/CAV2009-final8.pd

Effects of surface characteristics on hydrofoil cavitation

This was an exploratory research project aimed at capitalizing on our recent research experience with unsteady partially cavitating flows. Earlier work identified the significant and unexpected effect of surface properties and water quality on the dynamics of these flows. The aim of this study was to explore the possibility of using hydrophobic surfaces to control or minimize unwanted vibration and unstable operation in the partially cavitating regime. A candidate shape, denoted as the Cav2003 hydrofoil, was selected on the basis of theoretical analysis for a given range of contact angle. We manufactured three hydrofoils of identical cross section, but different surface characteristics. Three different surfaces were studied: anodized aluminium (hydrophilic), Teflon (hydrophobic), and highly polished stainless steel (hydrophobic). Contact angle was measured with a photographic technique developed by three of the undergraduates working on the project. Studies were made in both weak and strong water. Significant surface effects were found, but were unexpected in the sense that they did not correlate with measured contact angles.http://deepblue.lib.umich.edu/bitstream/2027.42/84293/1/CAV2009-final112.pd

Analysis of the Airfoil Stall With a Modification of Viscous-Inviscid Interaction Concept

A modification of the viscous-inviscid interaction concept with the employment of coupled vortices around the airfoil wake is introduced for analyzing the airfoil stall. The analyzed flow includes the laminar boundary layers, laminar separation bubble, laminar-turbulent transition zone, turbulent boundary layers, turbulent separation zone, wake, and outer inviscid flow. Integral methods are employed for the boundary layers. The boundaries of separation zones are analyzed as free surfaces, however, their lengths and shapes depend on the Reynolds number. The described modification is validated by a comparison of the numerical results with the previously published experimental data for various airfoils and Reynolds numbers at low Mach numbers. This modification achieves a reasonably good agreement of the computed lift and moment coefficients with their measured values

Low‐carbon transition risks for finance

The transition to a low‐carbon economy will entail a large‐scale structural change. Some industries will have to expand their relative economic weight, while other industries, especially those directly linked to fossil fuel production and consumption, will have to decline. Such a systemic shift may have major repercussions on the stability of financial systems, via abrupt asset revaluations, defaults on debt, and the creation of bubbles in rising industries. Studies on previous industrial transitions have shed light on the financial transition risks originating from rapidly rising “sunrise” industries. In contrast, a similar conceptual understanding of risks from declining “sunset” industries is currently lacking. We substantiate this claim with a critical review of the conceptual and historical literature, which also shows that most literature either examines structural change in the real economy, or risks to financial stability, but rarely both together. We contribute to filling this research gap by developing a consistent theoretical framework of the drivers, transmission channels, and impacts of the phase‐out of carbon‐intensive industries on the financial system and on the feedback from the financial system into the rest of the economy. We also review the state of play of policy aiming to protect the financial system from transition risks and spell out research implications