Simulation of firebrands transport generated by the seat of fire

Physical and mathematical model of the seat of fire, taking into account the transport of firebrands from the combustion zone was developed. The results received in the study are tentative and can be used only for a qualitative description of the process. The motion of firebrands is mainly determined by the aerodynamic processes accompanying the combustion process. At the initial stage of the motion the medium and large size firebrands are transported by the rising flow in the direction to the upper boundary of the thermal column, then are trapped by a toroidal vortex and are transported from the combustion zone to the external boundary of the circulating flow, where they are deposited on the underlying surface. The maximum rise height of the particles transported from the peripheral area is smaller, and the transport range is greater compared to the particles transported from the central area. Large firebrands have a small specific surface area (the ratio between the particle surface area and volume) compared to small firebrands. As a result, the temperature of large firebrands during landing is above the critical one in contrast to small firebrands, which may initiate the ignition of the underlying surface and the formation of the secondary seat of fire. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Some of the features of the viscoplastic media

The article considers the influence of the structure and the chemical composition of ground blast furnace slag on rheological properties of slag suspensions. Different composition and structure of blast furnace slags were studie

Laser sounding of instantaneous and mean speed of wind using correlation method

The correlation methods for laser sounding of wind speed are based on mutual processing of lidar signals scattered from several spatially separated volumes at each altitude investigated. The time of atmospheric aerosol transport between the scattering volumes estimated by the position of maximum of the mutual correlation function is the measure of corresponding wind speed. In this case the distance between the scattering volumes (the measuring base), defining the time of aerosol movement through the measuring base also determines the lidar possibilities for measuring the instantaneous (during the time interval of several seconds) or the mean wind speed (some minutes). Based on the experimental investigations performed using two lidars, these possibilites are analyzed

Modeling of wood surface ignition by wildland firebrands

The probability of structural ignition is dependent both on physical properties of materials and the fire exposure conditions. In this study, the effect of firebrand characteristics (i.e., firebrand size, number of firebrands) on wood ignition behavior was considered. Mathematical modeling and laboratory experiment were conducted to better understand the conditions of wood ignition by a single or group of firebrands with different geometry. This model considers the heat exchange between the firebrands, wood layer and the gas phase, moisture evaporation in the firebrands and the diffusion gases of water vapor in the pyrolysis zone. In order to test and verify the model, a series of experiments to determine probability and conditions for ignition of wood-based materials (plywood, oriented strand board, chipboard) caused by wildland firebrands (pine twigs with a diameter of 6–8 mm and a length of 40 ± 2 mm) were conducted. The experiments investigated the firebrand impact on the wood layer under different parameters, such as firebrand size and quantity, wind speed, and type of wood. The results of experiments showed that the increase in wind speed leads to the increase in probability of wood ignition. Based on the received results, it can be concluded that the ignition curve of wood samples by firebrands is nonlinear and depends on the wind speed and firebrand size as well as their quantity. At the same time, there is no ignition of wood samples in the range of wind speed of 0–1 m/s. The ignition of wood is possible with a decrease in the distance between the firebrands with a decrease in the firebrand length. This result agrees more closely with the model

Experimental investigation of surface litter ignition by bark firebrands

Probability and conditions for ignition of surface litter (pine needles) caused by firebrands is studied in the laboratory conditions. For modeling of firebrands, pine bark of various sizes 10×10, 15×15, 20×20, 25×25, 30×30 mm2 and 5 mm in thickness is used. The experiment was conducted in the absence of wind and at different wind velocities: 1, 1.5, 2 and 3 m/s. To conduct investigations, an experimental setup was constructed for generation of firebrands and their impact on surface litter. The results of experiments have shown that the increase in air velocity leads to the increase in probability of surface litter ignition. Thus, wind plays a role of catalyst in the ignition process, bringing an oxidizing agent to firebrands and supporting the process of smoldering. However, if the wind velocity is insufficient for ignition, then there is only the process of smoldering. The area of “uncertainty”, where there is smoldering of surface litter without transition to ignition, is found to decrease with increasing the wind velocity. Based on the received results, it can be concluded that the ignition curve of surface liter by firebrands is nonlinear and depends on the wind velocity. At the same time, there is no smoldering and ignition of surface litter for all the wind velocities and the particles with a size of 10 × 10 mm2, regardless of their number

Molecular labeling of <i>Vrn</i>, <i>Ppd</i> genes and vernalization response of the ultra-early lines of spring bread wheat <i>Triticum aestivum</i> L.

Background. The knowledge of genetic control of vernalization response in the ultra-early accessions can facilitate bread wheat breeding for a high adaptive capacity. Materials and methods. The study involved the ultra-early lines Rico (k-65588) and Rimax (k-67257) as the earliest maturing lines in the VIR bread wheat collection, as well as 10 Rifor lines (k-67120, k-67121, k-67250-67256) with a high rate of development before heading. A late ripening accession ‘Forlani Roberto’ (k-42641) and ‘Leningradskaya 6’ variety (k-64900), regionally adapted to Northwestern Russia, were also studied. The alleles of the Vrn and Ppd genes were identified by the PCR analysis using the allele-specific primers published in literature sources. The response to vernalization (30 days at 3°C) and a short 12-hour day were determined using a methodology accepted at VIR. Results. The ultra-early lines respond to a short 12-hour day and 30-day vernalization very poorly. The genotype of ultra-early wheat lines is mainly represented by three genes, Vrn-A1, Vrn-B1a, and Vrn-D1, which ensure insensitivity to vernalization alongside with the expression of Ppd-D1a, which controls the response to photoperiod. The ultra-early lines Rifor 4 and Rifor 5 have a recessive allele vrn-A1a, like the original ‘Forlani Roberto’ accession. The lines Rifor 4 and Rifor 5 are vernalization-insensitive under the long day and have a very weak response under the short day (3.5±0.42 days and 4.0±0.61 days, respectively). However, ‘Forlani Roberto’ with the vrn-A1a gene responds to vernalization in the same way under any photoperiod (12.3±1.58 days and 12.2±0.74 days). Conclusion The ultra-early lines of bread wheat Rifor 4 and Rifor 5 with the vrn-A1a gene can have no response to vernalization or have a low level response. This effect can be a reason for the formation of a complex of modifier genes along with the dominant gene Vrn-D1, which forms during the hybridization of F7-8 Rico × Forlani Roberto. The ultra-early lines of bread wheat Rico, Rimax and Rifor (k-67120, k-67121, k-67250-67256) can serve as effective sources of genes for earliness in common wheat breeding

Diversity of photoperiodic responses in oats

The article presents the results of an evaluation of the earliness and photoperiodic response (PPR) in the long-day oat accessions  of various geographic origin. The material for this study were 139 oat accessions  from the global collection of plant genetic resources  maintained by the Vavilov Institute (VIR), which included  landraces, breeding cultivars, and lines. In addition,  the donors  of low sensitivity to photoperiod developed at VIR were tested. A preliminary field study of the oat collection for early maturity and growing plants in the vegetation experiment was carried out according to the VIR Guidelines. The early accessions from VIR’s oat collection identified in the field showed a great diversity of their photoperiodic responses during the vegetation experiment in a photoperiod facility. By origin, most of the accessions described in the vegetation experiment as earliness  and weakly responsive to photoperiod were from Brazil (66 %); others from the USA, Portugal, Turkey, Colombia and Australia. Most of the Russian cultivars studied (77 %) were sensitive to a short  photoperiod. Among donors  with different  photoperiodic responses, Skorospely 1 and  Skorospely 2 were weakly responsive to photoperiod, while Srednespely 1 and  Srednespely 2 showed medium  responses. Many years of field studies  and vegetation experiments with the  oat genetic diversity from the VIR global collection  have resulted in identifying genotypes characterized by earliness and weak photoperiodic responses. These accessions  are of special value for breeders and currently being used to develop new early and productive oat cultivars

The WF1 (White Flower 1) gene controlling the white color of petals and flowering time in lines from a mapping population of flax (Linum usitatissimum L.)

Flax (Linum usitatissimum  L.) is grown  in different  climatic zones  as both  a spring  and  winter  crop. Adaptation to different growing conditions produced genotypes with different growth  durations and degrees of photosensitivity. It was always of great importance for breeders to create varieties with rapid development, in particular, early-flowering ones. The evaluation of lines from the VIR flax genetic collection revealed  a wide intraspecific diversity in the duration of growth  phases,  the number of leaves on the stem  (physiological indicator  of early flowering), and the degree of photosensitivity. Line gc-109, early flowering under the long-day conditions, but greatly photosensitive, was found to possess the wf1 (white flowers) gene, associated with early flowering and a small number of leaves. This line was crossed to the late-flowering but low-photosensitive line gc-375, which had reddish purple flowers. The analysis of segregation in F2 held under  the long (19 hours) and short (12 hours, daylength at the equator) day conditions showed that  the number of leaves on the plant stem was associated with the flowering time and controlled by close genetic systems only under the long-day conditions. In addition, no relationship between the flowering time and petal color was found under  the short-day  conditions. Thus, different groups  of genes  are active in different light schedules. More than 200 lines of the 6th generation of inbreeding were obtained from the plants of the hybrid population. Their field testing under  the long-day  conditions showed that  although the majority of the lines with white petals  flowered early and had a small number of leaves, some of them bloomed later and were leafier. On the contrary, the early flowering and less leafy lines appeared among the lines with colored flowers. Therefore, it is reasonable to assume  that a crossover between the gene  participating in the control of early flowering, which came from the gc-109 line, and its wf1 gene occurred  in meiosis of F1. The linkage between the genes  controlling  early flowering and white petals  suggests that flower color can serve as a marker of early flowering in the selection of early breeding material