Large Eddy Simulation of Riverflows

Keynote Lecture

Rayleigh Wave Dispersion Curve Inversion: Occam Versus the L1-Norm

We compare inversions of Rayleigh wave dispersion curves for shear wave velocity depth profiles based on the L2-norm (Occam\u27s Inversion) and L1-norm (TV Regularization). We forward model Rayleigh waves using a finite-element method instead of the conventional technique based on a recursion formula and root-finding. The forward modeling naturally leads to an inverse problem that is overparameterized in depth. Solving the inverse problem with Occam\u27s Inversion gives the smoothest subsurface model that satisfies the data. However, the subsurface need not be smooth and we therefore also solve the inverse problem with TV Regularization, a procedure that does not penalize discontinuities. The use of such a regularization scheme for such an overparameterized inverse problem means blocky subsurface models can be obtained without fixing the layer boundaries in advance. This represents an entirely new philosophy for surface wave inversion

Heat transfer from the stagnation area of a heated cylinder at Re(D) = 140,000 affected by free-stream turbulence

This is the post-print version of the final paper published in International Journal of Heat and Mass Transfer. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2011 Elsevier B.V.The effect of free-stream grid-turbulence on the flow around and heat transfer from the stagnation region of a circular cylinder was studied using direct numerical simulations (DNS). Simulations with and without free-stream fluctuations were carried out at a Reynolds number of Re(D) = 140,000 (based on the inflow velocity and the cylinder diameter D), which is in the higher subcritical range. A splitter plate was introduced behind the cylinder to counteract the formation of a vortex street. To resolve the flow up to 746.5 million grid points were employed. Compared to the fully laminar simulation, the addition of Tu = 30% grid turbulence at the inflow plane was found to lead to an increase in heat transfer at the stagnation line of the cylinder of 66%. A very good agreement was obtained with the correlations of Dullenkopf and Mayle [K. Dullenkopf, R. Mayle, The effects of incident turbulence and moving wakes on laminar heat transfer in gas turbines, ASME J. Turbomach. 116 (1994) 23–28; K. Dullenkopf, R. Mayle, An account of free-stream-turbulence length scale on laminar heat transfer, ASME J. Turbomach. 117 (1995) 401–406].The German Research Foundatio

A preliminary study on the relevancy of sustainable building design to commercial property depreciation

This preliminary study aims to explore the relationship between sustainable building designparadigms and commercial property depreciation, to assist in the understanding of sustainable building design impact towards commercial building value and rental deemploys the qualitative method and analyses valuers’ current perception of sustainable design and depreciation issues in Malaysia. The findings present evidence that the eleven factors of sustainable building design paradigms are relevant to commercial property depreciation and obsolescence as agreed by the sample as a whole. Nevertheless, the level of relevancy varied from one factor to another with sustainable HVAC system, sustainable building status and sustainable building system dominate the top three ranking in this study.Keywords: design and architecture; depreciation; commercial property

Grain‐energy release governs mobility of debris flow due to solid–liquid mass release

Debris flows often exhibit high mobility, leading to extensive hazards far from their sources. Although it is known that debris flow mobility increases with initial volume, the underlying mechanism remains uncertain. Here, we reconstruct the mobility–volume relation for debris flows using a recent depth‐averaged two‐phase flow model without evoking a reduced friction coefficient, challenging currently prevailing friction‐reduction hypotheses. Physical experimental debris flows driven by solid–liquid mass release and extended numerical cases at both laboratory and field scales are resolved by the model. For the first time, we probe into the energetics of the debris flows and find that, whilst the energy balance holds and fine and coarse grains play distinct roles in debris flow energetics, the grains as a whole release energy to the liquid due to inter‐phase and inter‐grain size interactions, and this grain‐energy release correlates closely with mobility. Despite uncertainty arising from the model closures, our results provide insight into the fundamental mechanisms operating in debris flows. We propose that debris flow mobility is governed by grain‐energy release, thereby facilitating a bridge between mobility and internal energy transfer. The initial volume of debris flow is inadequate for characterizing debris flow mobility, and a friction‐reduction mechanism is not a prerequisite for the high mobility of debris flows. By contrast, inter‐phase and inter‐grain size interactions play primary roles and should be incorporated explicitly in debris flow models. Our findings are qualitatively encouraging and physically meaningful, providing implications not only for assessing future debris flow hazards and informing mitigation and adaptation strategies, but also for unravelling a spectrum of earth surface processes including heavily sediment‐laden floods, subaqueous debris flows and turbidity currents in rivers, reservoirs, estuaries, and ocean

INDICATION OF META-ANTHRACITE BY MAGNETOTELLURICS IN THE KŐSZEG-RECHNITZ PENNINIC WINDOW : A TEST AREA

One of the Penninic Nappes is the Kőszeg-Rechnitz (K-R) tectonic window at the Eastern end of the Eastern Alps. It has a complicated metamorphic history from the Jurassic time. The organic material of the Penninic Ocean was transformed to electrically conductive meta-anthracite. Its amount in the chalcophyllite is estimated by geochemists to 0.2 per cent. Taking this conducting structure as a test area pilot deep magnetotelluric (MT) soundings have been carried out and we determined - the structure of the conductivity anomaly due to 0.2 per cent meta anthracite in the K-R window and its surroundings - the different kinds of MT distortions as lateral (side) effect of the conductor appearing in the crust and mantle - the most probable depth of the conductive asthenosphere at the border of the Pannonian Basin (having extreme shallow asthenosphere). The obtained ~140 km depth is in correlation with value of the asthenospheric map based mainly on seismic data