Full Length Article Flame characteristics and burning rate of small pool fires under downslope and upslope oblique winds P. Zhu a , X.S. Wang a,b,⇑ , Y.P. He c , C.F. Tao a , X.M. Ni a a State Key Lab. of Fire Science, University of Science & Technology of China, Hefei 230026, PR China b Anhui Province Center of Collaborative Innovation for City Public Security, Hefei 230027, PR China c School of Computing, Engineering and Mathematics, University of Western Sydney, Locked Bag 1797, Australia highlights  Burning rates under upslope wind reduce more obviously than that under downslope wind.  Inverse variations of flame shape occur between upslope and downslope wind.  Flame lengths first increase, then decrease with increasing wind speed.  Flame tilt angle increases until to an asymptotic value with increasing wind speed.  The modified correlations are presented to describe the flame tilt characteristics. article info Article history: Received 30 May 2016 Received in revised form 11 July 2016 Accepted 15 July 2016 Available online 25 July 2016 Keywords: Combustion characteristic Pool fire Flame tilt angle Flame length Oblique wind abstract This paper presents an experimental investigation on burning rate, flame tilt angle and flame length of small ethanol pool fires under different oblique winds. Square pool fires with dimension of 4 cm and 6 cm with wind attack angles from 0° to 30° and wind speeds from 0 to 3.28 m s 1 for downslope airflow and from 0 to 1.90 m s 1 for upslope airflow are tested. Flame tilt angle and flame length are determined based on luminous flame intermittency from the flame images. The results show that the burning rate under downslope wind is relatively larger than that under upslope wind at the same absolute wind speed and slope angle. The flame tilt angle and flame length generally increase with the increase of wind slope angle for downslope airflow, but decrease with the increase of upslope airflow angle. At a given wind slope angle, the flame tilt angle generally increases with the increase of wind speed until to an asymptotic value when the wind speed exceeds 0.35 m s 1 ; the flame length first increases and then decreases for downslope wind, but initially decreases then increases before decrease again for upslope wind. In addi- tion, some modified correlations are developed to analyze the flame tilt angle and flame length data under oblique wind conditions. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Pool fires are the most frequently occurred industry accidents [1,2], which may be either the initiators, or the consequences in most industry accidents involving fires and explosions [3,4]. In fact, pool fires may occur under many topographical and meteorological conditions, such as oblique wind conditions. For instance, the oil tanker fires [5] occurred in oil tank battery located at hilly land and the fires occurred in a sloped road tunnel are all related to both of the downslope and upslope wind conditions. In this kind of circumstance, the combustion of the fuel can be affected not only by the wind speed, but also by the wind direction. The fire hazard would be extended by the deflected flame under oblique wind conditions. As an important fundamental topic in fire and combustion research, liquid pool fire behaviour has been studied for decades [6], and most of them focused on flame characteristics under qui- escent or horizontal wind conditions, such as burning rate [7– 11], flame thermal radiation [12–14], flame tilt angle [15–25], flame length [15–18,20,24]. Flame shape is a dominant factor for determination of flame radiant emission hazards of a real fire scenario. Under quiescent condition, flame height would be the most important dimension in characterizing the flame geometry. However, under wind condition, the flame will deflect with an http://dx.doi.org/10.1016/j.fuel.2016.07.059 0016-2361/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: State Key Lab. of Fire Science, University of Science & Technology of China, Hefei 230026, PR China. E-mail addresses: wxs@ustc.edu.cn (X.S. Wang), Y.HE@uws.edu.au (Y.P. He). Fuel 184 (2016) 725–734 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel