MODELING OF PROCESSES OF OCCURRENCE AND SPREAD OF FIRES IN GRASS ECOSYSTEMS

Abstract

Formulation of the problem. Fires in natural ecosystems are emergency that leads to a violation of the balance of the environment and human life. Along with forest fires, the consequences of which are significant material damage and a detrimental effect on the atmosphere, grass fires occur, which entail the destruction of phytocenoses and representatives of the animal world. Prevention of grass fires is an urgent task that requires research in this direction.

The purpose of the work is to assess the fire hazard in areas dominated by creeping pyrium (Elytrigia repens) as a representative of the widespread species of grass vegetation in meadows, pastures, agricultural areas that are not exploited, etc., under meteorological conditions favorable for the spread of fires, and the humidity of combustible material, as well as the geometric parameters of plants.

Description of the material. A study of the fire hazard of areas covered by grassy vegetation from the average grass height and wind speed using computer simulation of a grass fire in the environment of the Wildland-Urban Fire Dynamics Simulator (WFDS) physical model was carried out. The fire hazard was estimated for creeping wheatgrass with an average plant height of 20, 40, 60, 80 and 100 cm from the propagation speed of the fire front, taking into account wind speeds of 0, 1, 2, 3, 4, 6, 8 m/s. Cases are noted in which, under the influence of weather conditions, ignition did not occur, but only ignition of combustible material was observed without further spread of fire, as well as cases of occurrence and spread of burning over the entire area of grass cover.

Results. Based on the simulation results, the values of the propagation rates of the fire front in grassy areas were obtained. The fire speed is greatest at a height of grass cover of 40 cm and a wind speed of 3 m/s, and the lowest at a height of grass cover of 60 cm and a wind speed of 0 m/s. A relationship is established that describes the dynamics of a fire along the height of the grass cover as a combustible material.

Scientific novelty. It has been established that in terms of the speed of propagation of the fire front, the greatest fire hazard of the grassland of creeping grass is observed at an average grass height of 40 cm and a wind speed of 3 m/s, which is more than 5 times this figure compared to a grass height of 60 cm in the absence of wind.