Natural ventilation of buildings is the flow generated by temperature differences and by the wind. The governing feature of this flow is the exchange between an interior space and the external ambient. Although the wind may often appear to be the dominant driving mechanism, in many circumstances temperature variations play a controlling feature on the ventilation since the directional buoyancy force has a large influence on the flow patterns within the space and on the nature of the exchange with the outside. Two forms of ventilation are discussed: mixing ventilation, in which the interior is at an approximately uniform temperature, and displacement ventilation, where there is strong internal stratification. The dynamics of these buoyancy-driven flows are considered, and the effects of wind on them are examined. The aim behind this work is to give designers rules and intuition on how air moves within a building; the research reveals a fascinating branch of fluid mechanics.

The fluid mechanics of natural ventilation

A comprehensive review of measurements and data analysis of laminar burning velocities for various fuel+air mixtures

Recent advances in understanding of flammability characteristics of hydrogen

This article gives an overview of the back- ground-oriented schlieren (BOS) technique, typical appli- cations and literature in the field. BOS is an optical den- sity visualization technique, belonging to the same family as schlieren photography, shadowgraphy or interferometry. In contrast to these older techniques, BOS uses correlation techniques on a background dot pattern to quantitatively characterize compressible and thermal flows with good spatial and temporal resolution. The main advantages of this technique, the experimental simplicity and the robust- ness of correlation-based digital analysis, mean that it is widely used, and variant versions are reviewed in the arti- cle. The advantages of each variant are reviewed, and fur- ther literature is provided for the reader. List of symbols

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Background-oriented schlieren (BOS) techniques

Hydrogen safety: The road toward green technology

http://conference.ing.unipi.it/ichs2011/papers/131.pdf

Flammability limits and laminar flame speed of hydrogen–air mixtures at sub-atmospheric pressures

An analysis of the hydrogen explosion in the Fukushima-Daiichi accident

http://conference.ing.unipi.it/ichs2009/images/stories/papers/221.pdf

The structure and flame propagation regimes in turbulent hydrogen jets

GASFLOW-MPI: A new 3-D parallel all-speed CFD code for turbulent dispersion and combustion simulations. Part I: Models, verification and validation

This paper presents results of an experimental investigation on the deflagration and deflagration-to-detonation transition (DDT) in an obstructed (blockage ratio BR = 50%), semi-confined flat layer filled with uniform hydrogen–air mixtures. The effect of mixture reactivity depending on flat layer thickness and its width is studied to evaluate the critical conditions for sonic flame propagation and the possibility for detonation onset. The experiments were performed in a transparent, rectangular channel with a length of 2.5 m. The flat layer thickness was varied from 0.06 to 0.24 m and the experiments were performed for different channel widths of 0.3, 0.6 and 0.9 m. The experimental results show flame velocity vs. hydrogen concentration for different thicknesses and widths of the semi-confined flat layer. Three different flame propagation regimes were observed: slow subsonic flame (M  > 1). It is shown that flame acceleration (FA) to sonic speed is independent of the width of the flat layer. The critical expansion ratio for effective flame acceleration to sonic speed was found to be linearly dependent on the reciprocal layer thickness.

Mike Kuznetsov

Papers

Flammability limits and laminar flame speed of hydrogen–air mixtures at sub-atmospheric pressures

An analysis of the hydrogen explosion in the Fukushima-Daiichi accident

The structure and flame propagation regimes in turbulent hydrogen jets

GASFLOW-MPI: A new 3-D parallel all-speed CFD code for turbulent dispersion and combustion simulations. Part I: Models, verification and validation

Experimental investigation of hydrogen–air deflagrations and detonations in semi-confined flat layers