Exploring three-dimensional coupled fire–atmosphere interactions downwind of wind-driven surface fires and their influence on backfires using the HIGRAD-FIRETEC model

2011 ◽  
Vol 20 (6) ◽  
pp. 734 ◽  
Author(s):  
J.-L. Dupuy ◽  
R. R. Linn ◽  
V. Konovalov ◽  
F. Pimont ◽  
J. A. Vega ◽  
...  
Keyword(s):  
Reasonable Agreement ◽  
Three Dimensional ◽  
Limited Range ◽  
Two Dimensions ◽  
Strong Wind ◽  
Wind Speeds ◽  
Surface Fires ◽  
Atmosphere Interaction ◽  
Weak Wind ◽  
Three Dimensional Simulations

The obstruction of ambient winds and the possible existence of indrafts downwind of a wildfire are aspects of coupled fire–atmosphere interaction influencing the effectiveness of a backfiring operation. The fire-influenced winds behind a headfire as well as their influences on backfire spread are explored using the three-dimensional HIGRAD-FIRETEC model. Fires are simulated under weak to strong wind speeds and in shrubland and grassland fuel types. The importance of three-dimensionality in the simulation of such phenomena is demonstrated. Results suggest that when fire–atmosphere interaction is constrained to two-dimensions, the limitations of air moving through the head fire could lead to overestimation of downwind indrafts and effectiveness of backfiring. Three-dimensional simulations in surface fuels suggest that backfires benefit from the obstruction of ambient winds and potentially the existence of an indraft flow in only a limited range of environmental conditions. Simulations show that flows are most favourable when the wildfire is driven downslope by a weak wind and the backfire is ignited at bottom of the slope. Model simulations are compared with backfiring experiments conducted in a dense shrubland. Although this exercise encountered significant difficulties linked to the ambient winds data and their incorporation into the simulation, predictions and observations are in reasonable agreement.

scholarly journals Three-dimensional Floquet stability analysis of the wake in cylinder arrays

2007 ◽  
Vol 592 ◽  
pp. 79-88 ◽  
Author(s):  
N. K.-R. KEVLAHAN
Keyword(s):  
Reasonable Agreement ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Instability Mechanism ◽  
Cylinder Arrays ◽  
Spatial Periodicity ◽  
Wake Instability ◽  
Mode A ◽  
Three Dimensional Simulations

Three-dimensional stability of the periodic wake of tightly packed rotated and inline cylinder arrays is investigated for 60 ≤ Re ≤ 270. Results are compared with existing numerical and experimental studies for an isolated cylinder. Numerical Floquet analysis shows that the two-dimensional wakes of the rotated and inline arrays with spacing P/D = 1.5 become unstable at Rec = 64 ± 0.5 and Rec = 132 ± 1 respectively. Two-dimensional vortex shedding flow is unlikely in practice for such flows. The dominant spanwise wavelength is λ/D = 0.9 ± 0.1 for the rotated array at Re = 100 and λ/D = 3.0 ± 0.1 for the inline array at Re = 200. Three-dimensional simulations show excellent agreement with the Floquet analysis for the rotated case, and reasonable agreement for the inline case. The instability mechanism appears to be similar to Mode A for an isolated cylinder, although the structure of the three-dimensional vorticity is different due to the spatial periodicity of the flow. Unlike the isolated cylinder, both array flows are unstable as λ → ∞ (like a thin shear layer). This is the first investigation of three-dimensional wake instability in cylinder arrays, a problem of significant practical and theoretical interest.

scholarly journals On the Predictability of Mesoscale Convective Systems: Three-Dimensional Simulations

2010 ◽  
Vol 138 (3) ◽  
pp. 863-885 ◽  
Author(s):  
Matthew S. Wandishin ◽  
David J. Stensrud ◽  
Steven L. Mullen ◽  
Louis J. Wicker
Keyword(s):  
Weather Prediction ◽  
Surface Wind ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Mesoscale Convective Systems ◽  
Forecast Errors ◽  
Two Dimensional ◽  
Convective Systems ◽  
Mesoscale Convective ◽  
Three Dimensional Simulations

Abstract Mesoscale convective systems (MCSs) are a dominant climatological feature of the central United States and are responsible for a substantial fraction of warm-season rainfall. Yet very little is known about the predictability of MCSs. To help address this situation, a previous paper by the authors examined a series of ensemble MCS simulations using a two-dimensional version of a storm-scale (Δx = 1 km) model. Ensemble member perturbations in the preconvective environment, namely, wind speed, relative humidity, and convective instability, are based on current 24-h forecast errors from the North American Model (NAM). That work is now extended using a full three-dimensional model. Results from the three-dimensional simulations of the present study resemble those found in two dimensions. The model successfully produces an MCS within 100 km of the location of the control run in around 70% of the ensemble runs using perturbations to the preconvective environment consistent with 24-h forecast errors, while reducing the preconvective environment uncertainty to the level of current analysis errors improves the success rate to nearly 85%. This magnitude of improvement in forecasts of environmental conditions would represent a radical advance in numerical weather prediction. The maximum updraft and surface wind forecast uncertainties are of similar magnitude to their two-dimensional counterparts. However, unlike the two-dimensional simulations, in three dimensions, the improvement in the forecast uncertainty of storm features requires the reduction of preconvective environmental uncertainty for all perturbed variables. The MCSs in many of the runs resemble bow echoes, but surface winds associated with these solutions, and the perturbation profiles that produce them, are nearly indistinguishable from the nonbowing solutions, making any conclusions about the bowlike systems difficult.

scholarly journals Approximating a Three-Dimensional Fluidized Bed With Two-Dimensional Simulations

2008 ◽  
Author(s):  
Mirka Deza ◽  
Francine Battaglia ◽  
Theodore J. Heindel
Keyword(s):  
Fluidized Bed ◽  
Scale Up ◽  
Three Dimensional ◽  
Limited Range ◽  
Gas Holdup ◽  
Point Of View ◽  
Air Injection ◽  
Two Dimensional ◽  
Parametric Studies ◽  
Three Dimensional Simulations

Fluidized beds can be used to gasify biomass in the production of producer gas, a flammable gas that can replace natural gas in process heating. Modeling these reactors with computational fluid dynamics (CFD) simulations is advantageous when performing parametric studies for design and scale-up. From a computational resource point of view, two-dimensional simulations are easier to perform than three-dimensional simulations, but they may not capture the proper physics. This paper will compare two- and three-dimensional simulations in a 10.2 cm diameter fluidized bed with side air injection to determine when two-dimensional simulations are adequate to capture the bed hydrodynamics. Simulations will be completed in a glass bead fluidized bed operating at 1.5Umf and 3Umf, where Umf is the minimum fluidization velocity. Side air injection is also simulated to model biomass injection for gasification applications. The simulations are compared to experimentally obtained time-averaged local gas holdup values using X-ray computed tomography. Results indicate that for the conditions of this study, two-dimensional simulations qualitatively predict the correct hydrodynamics and gas holdup trends that are observed experimentally for a limited range of fluidization conditions.

scholarly journals The characteristics of weather-related wind load parameters and wind power quality over the Dabanchen strong gale area

2021 ◽  
Author(s):  
Yu Xin ◽  
Zonhui Liu ◽  
Qing He
Keyword(s):  
Wind Power ◽  
Three Dimensional ◽  
Measurement Data ◽  
Wind Load ◽  
Strong Wind ◽  
Dynamic Interactions ◽  
Integral Scale ◽  
Turbulence Structures ◽  
Wind Speeds ◽  
Three Dimensional Measurement

Abstract Analysis of data from cup and ultrasonic anemometers on a 100 m-tall wind mast in the Dabanchen Canyon reveals that the turbulence intensities, gust factors, and peak factors measured by cup anemometers tend to be severely undervalued compared to longitudinal values from an ultrasonic anemometer, and onsite three-dimensional measurement data are preferred for weather-related wind load calculation. This difference is related to the rotating responses of cup anemometers during wind speed acceleration or deceleration and the higher vertical fluctuation speeds driven by dynamic interactions with the sloped canyon terrain. The higher lateral turbulence is key consideration for determining wind turbine classes in Danbanchen strong wind area. The longitudinal gust and peak factors under wind speeds exceeding 25.0 m s−1 are comparable with those of typhoon-prone open, flat regions. The chances of high turbulence and unstable stratification convective processes are very high; thus, wind power collection efficiencies are not high. Except the longitudinal turbulence integral scale, China’s wind-resistance codes are not applicable due to occasional undesirable strong gales with extraordinary turbulence structures. The measured vertical power spectral density of fluctuating wind in the high-frequency domain cannot reflect the rapidly adapting features of the vast terrain under strong gales.

scholarly journals Snow Accretion on Electric Wires and its Prevention

1977 ◽  
Vol 19 (81) ◽  
pp. 657-657 ◽  
Author(s):  
Gorow Wakahama ◽  
Daisuke Kuroiwa ◽  
Kazuo Gotō
Keyword(s):  
Power Transmission ◽  
The Sea Of Japan ◽  
Strong Wind ◽  
Wind Tunnel Experiments ◽  
New Techniques ◽  
Wind Speeds ◽  
Transmission Towers ◽  
Wet Snow ◽  
Weak Wind

AbstractThis paper presents a study on the accretion of wet snowflakes transported by a strong cyclone on electric wires by means of wind-tunnel experiments and field observations with the aim of successfully preventing them from accreting on and causing damage to power lines and high-voltage power-transmission towers in snowy areas in such countries as Japan, Canada, and the U.S.A. Although extensive studies have been made on snow accretion in Japan since the 1930's by many workers, their studies have been restricted to the coastal regions of central Honshu facing the Sea of japan, which are typified by heavy wet snowfalls of the monsoon type in a weak wind of less than 3 m/s at a temperature between –1° and +1.5+C continuing throughout the day. However, it has long been known that a cyclone characterized by a strong wind exceeding 10 m/s that carries heavier and wetter snowflakes can cause snow accretion on electric wires to grow to 20–30 cm in diameter. Because its detailed accretion processes and mechanism had not been clarified, studies have been made on the growth processes of snow accretion, the adhesive stress of snow to a wire, the structure and texture of the accreted snow, coefficients of collision and collection of snow on the wire, and trajectories of individual snow particles impinging on or passing by a wire at various wind speeds. It has been confirmed that wet snow can accrete on wires at any wind speed between 0 and 20 m/s. Moreover, new techniques have been developed to prevent wet snow from accreting on wires, and these have proved to be effective in situ for any type of snow accretion in Hokkaido.

scholarly journals The Analysis of the Spatiotemporal Variations and Mechanisms for the Near-Surface Wind Speed Over China in the Last 40 Years

2021 ◽  
Author(s):  
Xia Li ◽  
Yongjie Pan ◽  
Yingsha Jiang
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
The Other ◽  
Strong Wind ◽  
Reanalysis Dataset ◽  
Near Surface ◽  
Wind Speeds ◽  
Dispersion Degree ◽  
Weak Wind

Abstract Near-surface wind speed is of great significance in many aspects of the human production and living. This study analyses the spatiotemporal characteristics of the near-surface wind speed and wind speed percentiles with meteorological station observations in China from 1979 to 2019. Furthermore, the mechanisms of the wind speed variations are also investigated with ERA-Interim reanalysis dataset. Spatially, the wind speeds in the northern and eastern regions of China are larger than that in the central and southern regions. Seasonally, the wind speed in spring is significantly larger than that in the other seasons. The dispersion degree of wind speed in spring is larger than that in the other seasons both spatially and temporally. The near-surface wind speed in China shows significantly decreasing trends during 1979–2019, particularly in 1979–1999, but the wind speed trend reversed after 2000. After dividing the wind speed into different percentiles, it recognizes that the decreasing trend of stronger winds are more significant than that of weaker winds. The weaker the wind speed, the more significant increasing trend after 2000. Therefore, the decreasing wind speed trend before 2000 is mainly caused by the significant reduction of strong wind, while the reversal trend after 2000 results from the increase of weak wind. The variations of the wind speed over China attributed to both the U and V wind components, and the variations of zonal wind is closely related to the weakened upper westerly wind field and the uneven warming between high and low latitudes.

scholarly journals The characteristics of weather-related wind load parameters and wind 2 power quality over the Dabanchen strong gale area

2021 ◽  
Author(s):  
Yu Xin ◽  
Zonhui Liu ◽  
Qing He
Keyword(s):  
Three Dimensional ◽  
Measurement Data ◽  
Wind Load ◽  
Strong Wind ◽  
Dynamic Interactions ◽  
Integral Scale ◽  
Turbulence Structures ◽  
Wind Speeds ◽  
Three Dimensional Measurement ◽  
Ultrasonic Anemometer

Abstract Analysis of data from cup and ultrasonic anemometers on a 100 m-tall wind mast in the Dabanchen Canyon reveals that the turbulence intensities, gust factors, and peak factors measured by cup anemometers tend to be severely undervalued compared to longitudinal values from an ultrasonic anemometer, and onsite three-dimensional measurement data are preferred for weather-related wind load calculation. This difference is related to the rotating responses of cup anemometers during wind speed acceleration or deceleration and the higher vertical fluctuation speeds driven by dynamic interactions with the sloped canyon terrain. The higher lateral turbulence is key consideration for determining wind turbine classes in Danbanchen strong wind area. The longitudinal gust and peak factors under wind speeds exceeding 25.0 m s−1 are comparable with those of typhoon-prone open, flat regions. The chances of high turbulence and unstable stratification convective processes are very high; thus, wind power collection efficiencies are not high. Except the longitudinal turbulence integral scale, China’s wind-resistance codes are not applicable due to occasional undesirable strong gales with extraordinary turbulence structures. The measured vertical power spectral density of fluctuating wind in the high-frequency domain cannot reflect the rapidly adapting features of the vast terrain under strong gales.

Laser Scanning Confocal Microscopy and Three-Dimesnsional Reconstruction of the Mitotic Spindles of Unequally Dividing Embryonic Cells

1990 ◽  
Vol 48 (3) ◽  
pp. 166-167
Author(s):  
J. Holy ◽  
G. Schatten
Keyword(s):  
Confocal Microscopy ◽  
Mitotic Spindle ◽  
Laser Scanning ◽  
Three Dimensional ◽  
Laser Scanning Confocal Microscopy ◽  
Two Dimensions ◽  
Embryonic Cells ◽  
Mitotic Spindles ◽  
Cleavage Division ◽  
Scanning Confocal Microscopy

One of the classic limitations of light microscopy has been the fact that three dimensional biological events could only be visualized in two dimensions. Recently, this shortcoming has been overcome by combining the technologies of laser scanning confocal microscopy (LSCM) and computer processing of microscopical data by volume rendering methods. We have employed these techniques to examine morphogenetic events characterizing early development of sea urchin embryos. Specifically, the fourth cleavage division was examined because it is at this point that the first morphological signs of cell differentiation appear, manifested in the production of macromeres and micromeres by unequally dividing vegetal blastomeres.The mitotic spindle within vegetal blastomeres undergoing unequal cleavage are highly polarized and develop specialized, flattened asters toward the micromere pole. In order to reconstruct the three-dimensional features of these spindles, both isolated spindles and intact, extracted embryos were fluorescently labeled with antibodies directed against either centrosomes or tubulin.

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