scholarly journals Wind speed variability study based on the Hurst coefficient and fractal dimensional analysis

2019 ◽  
Vol 7 (2) ◽  
pp. 361-378 ◽  
Author(s):  
Erasmo Cadenas ◽  
Rafael Campos‐Amezcua ◽  
Wilfrido Rivera ◽  
Marco Antonio Espinosa‐Medina ◽  
Alma Rosa Méndez‐Gordillo ◽  
...  
Keyword(s):  
Wind Speed ◽  
Dimensional Analysis ◽  
Hurst Coefficient ◽  
Variability Study

Regimes of Dry Convection above Wildfires: Idealized Numerical Simulations and Dimensional Analysis*

2009 ◽  
Vol 66 (4) ◽  
pp. 806-836 ◽  
Author(s):  
Michael T. Kiefer ◽  
Matthew D. Parker ◽  
Joseph J. Charney
Keyword(s):  
Wind Speed ◽  
Pressure Gradient ◽  
Dimensional Analysis ◽  
Mixed Layer ◽  
Wind Profile ◽  
Dynamic Pressure ◽  
Fire Behavior ◽  
Hybrid Mode ◽  
Surface Buoyancy ◽  
Dry Convection

Abstract Wildfires are capable of inducing atmospheric circulations that result predominantly from large temperature anomalies produced by the fire. The fundamental dynamics through which a forest fire and the atmosphere interact to yield different convective regimes is still not well understood. This study uses the Advanced Regional Prediction System (ARPS) model to investigate the impact of the environmental (i.e., far upstream, undisturbed by fire) wind profile on dry convection above a prescribed heat source of an intensity and spatial scale comparable to a wildfire. Dimensional analysis of the fire–atmosphere problem provides two relevant parameters: a surface buoyancy parameter that addresses the amount of heat a parcel of air receives in transiting above the fire and an advection parameter that addresses the degree to which the environmental wind advects updrafts away from the fire. Two-dimensional simulations are performed in which the upstream surface wind speed and mixed layer mean wind speed are varied independently to better understand the fundamental processes governing the organizational mode and updraft strength. The result of these experiments is the identification of two primary classes of dry convection: plume and multicell. Simulated plume cases exhibit weak advection by the mean wind and are subdivided into intense plume and hybrid classes based on the degree of steadiness within the convection column. Hybrid cases contain columns of largely discrete updrafts versus the more continuous updraft column associated with the intense plume mode. Multicell cases develop with strong mixed layer advection and are subdivided into strong and weak classes based on the depth of convection. Intense plume and strong multicell (hybrid and weak multicell) cases occur when the surface buoyancy is large (small). Parcel analyses are performed to more closely examine the forcing of convection within different areas of the parameter space. The multicell (strong and weak) and intense plume modes are forced by a combination of buoyancy and dynamic pressure gradient forcing associated with the perturbation wind field, whereas the hybrid mode is forced by a combination of buoyancy and dynamic pressure gradient forcing associated with the strong background shear. The paper concludes with a discussion of the degree of nonlinearity that is likely to exist at the fire front for each of the convective modes; nonlinear fire behavior is most likely for the hybrid mode and least likely for the weak multicell mode. Knowledge of the sensitivity of the convective mode to upstream conditions can provide information about the degree of nonlinear or erratic fire behavior expected for a given wind profile upstream of the fire.

Performance Testing and Dimensional Analysis of Multi-Blade Wind Turbine for Low Wind Speed Applications

2013 ◽  
Vol 860-863 ◽  
pp. 305-308
Author(s):  
Yuttachai Keawsuntia
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Dimensional Analysis ◽  
Wind Velocity ◽  
Performance Testing ◽  
Mechanical Power ◽  
Low Wind Speed ◽  
Water Pumping ◽  
Study Results ◽  
Pi Theorem

This article is to present the study results of small multi blade wind turbine for use in low wind speed area. In this experiment, the wind turbine has a diameter is 1 m, 30 blades. Each blade has the chord length of 6.5 cm, the length of 0.25 m, which has a curvature plate ratio of 0.15, and blade setting angle of 30 degree. Wind turbine was tested by wind tunnel at wind velocity of 3, 4 and 5 m/s. The results from the test run of, this the wind turbine give maximum mechanical power in each wind velocity of 3.66, 9.91 and 21.76 watts, respectively. From the dimensional analysis of wind rotor turbine by using Buckingham Pi theorem, the wind turbine is up to two times as large that is 2 m diameter; give maximum mechanical power increased to 14.64, 39.24 and 87.04 watts, this power can be generate electric power or use for water pumping for a household.

In situ investigation of the primary recrystallization of alpha titanium in HVEM

1978 ◽  
Vol 36 (1) ◽  
pp. 634-635
Author(s):  
S. Naka ◽  
R. Penelle ◽  
R. Valle
Keyword(s):  
Dimensional Analysis ◽  
Texture Evolution ◽  
Cold Work ◽  
Three Dimensional ◽  
Primary Recrystallization ◽  
Thin Foils ◽  
In Situ Investigation ◽  
Grain Growth Model ◽  
Alpha Titanium

The in situ experimentation technique in HVEM seems to be particularly suitable to clarify the processes involved in recrystallization. The material under investigation was unidirectionally cold-rolled titanium of commercial purity. The problem was approached in two different ways. The three-dimensional analysis of textures was used to describe the texture evolution during the primary recrystallization. Observations of bulk-annealed specimens or thin foils annealed in the microscope were also made in order to provide information concerning the mechanisms involved in the formation of new grains. In contrast to the already published work on titanium, this investigation takes into consideration different values of the cold-work ratio, the temperature and the annealing time.Two different models are commonly used to explain the recrystallization textures i.e. the selective grain growth model (Beck) or the oriented nucleation model (Burgers). The three-dimensional analysis of both the rolling and recrystallization textures was performed to identify the mechanismsl involved in the recrystallization of titanium.

Dimensional Analysis of Protective Factors and Suicidality Among Combat Vietnam Veterans

2009 ◽  
Author(s):  
Rumi Price ◽  
Gregory Widner ◽  
William True ◽  
Monica Matthieu
Keyword(s):  
Protective Factors ◽  
Dimensional Analysis ◽  
Vietnam Veterans

Characterizing the convective heat exchange with plastic shading nets under natural arid conditions

2019 ◽  
pp. 11-20
Author(s):  
Ahmed M Abdel-Ghanya ◽  
Ibrahim M Al-Helal
Keyword(s):  
Wind Speed ◽  
Thermal Radiation ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Convective Heat Exchange ◽  
Radiative Properties ◽  
Wooden Frame ◽  
Arid Conditions ◽  
Air Temperatures ◽  
Radiation Fluxes

Plastic nets are extensively used for shading purposes in arid regions such as in the Arabian Peninsula. Quantifying the convection exchange with shading net and understanding the mechanisms (free, mixed and forced) of convection are essential for analyzing energy exchange with shading nets. Unlike solar and thermal radiation, the convective energy, convective heat transfer coefficient and the nature of convection have never been theoretically estimated or experimentally measured for plastic nets under arid conditions. In this study, the convected heat exchanges with different plastic nets were quantified based on an energy balance applied to the nets under outdoor natural conditions. Therefore, each net was tacked onto a wooden frame, fixed horizontally at 1.5-m height over the floor. The downward and upward solar and thermal radiation fluxes were measured below and above each net on sunny days; also the wind speed over the net, and the net and air temperatures were measured, simultaneously. Nets with different porosities, colors and texture structures were used for the study. The short and long wave’s radiative properties of the nets were pre-determined in previous studies to be used. Re and Gr numbers were determined and used to characterize the convection mechanism over each net. The results showed that forced and mixed convection are the dominant modes existing over the nets during most of the day and night times. The nature of convection over nets depends mainly on the wind speed, net-air temperature difference and texture shape of the net rather than its color and its porosity.

Monitoring Coastal Wind Speed Using BeiDou GEO Reflected Signals

2016 ◽  
Author(s):  
Qiang Wang ◽  
Dongkai Yang ◽  
Hongxing Gao ◽  
Weiqiang Li ◽  
Yunlong Zhu ◽  
...  
Keyword(s):  
Wind Speed

FORECASTING THE AVERAGE MONTHLY WIND SPEED WITH THE USE OF THE BAYES APPROACH TO FORECASTING

2018 ◽  
Vol 27 (103) ◽  
pp. 151-156
Author(s):  
V. Rosen, ◽  
◽  
A. Chermalykh, ◽  
A. Buchkivskii
Keyword(s):  
Wind Speed ◽  
Bayes Approach

THE INFLUENCE OF THE WIND SPEED PREDICTION ERROR ON THE SIZE OF THE STORAGE CONTROLLED OPERATION ZONE IN THE SYSTEM WITH THE WIND GENERATOR

2020 ◽  
Vol 2020 (57) ◽  
pp. 35-41
Author(s):  
K.S. Klen ◽  
◽  
M.K. Yaremenko ◽  
V.Ya. Zhuykov ◽  
◽  
...  
Keyword(s):  
Wind Speed ◽  
Prediction Error ◽  
Average Energy ◽  
Interpolation Formula ◽  
Wind Speed Prediction ◽  
Wind Generator ◽  
Prediction Horizon ◽  
Speed Prediction ◽  
Using Data ◽  
Predictor Corrector

The article analyzes the influence of wind speed prediction error on the size of the controlled operation zone of the storage. The equation for calculating the power at the output of the wind generator according to the known values of wind speed is given. It is shown that when the wind speed prediction error reaches a value of 20%, the controlled operation zone of the storage disappears. The necessity of comparing prediction methods with different data discreteness to ensure the minimum possible prediction error and determining the influence of data discreteness on the error is substantiated. The equations of the "predictor-corrector" scheme for the Adams, Heming, and Milne methods are given. Newton's second interpolation formula for interpolation/extrapolation is given at the end of the data table. The average relative error of MARE was used to assess the accuracy of the prediction. It is shown that the prediction error is smaller when using data with less discreteness. It is shown that when using the Adams method with a prediction horizon of up to 30 min, within ± 34% of the average energy value, the drive can be controlled or discharged in a controlled manner. References 13, figures 2, tables 3.

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