We can divide atmosphere into two mediums, barotropic and baroclinic. Due to horizontal gradient of density, baroclinic medium causes to produce various horizontal gradient of pressure with respect to height and implies various horizontal velocities at different layers of the atmosphere. Therefore; geostrophic wind varies with respect to height in this medium.The horizontal gradient of density not only would produce by horizontal gradient of temperature, but also by horizontal gradient of humidity or combination of both.If horizontal gradient of density would be by both horizontal gradient of temperature and horizontal gradient of humidity – as they are existing in natural air – in the case; vectorial difference of geostrophic wind with respect to height is; dense wind.If horizontal gradient of density is related to gradient of temperature solely; vectorial difference between geostrophic wind from top level and bottom level of the layer is; thermal wind.And if horizontal gradient of density is solely related to gradient of specific humidity; vectorial difference between geostrophic wind from top level and bottom level of the layer is; moist wind.The purpose of this paper is confirmation of three versions of dense wind, introduction five particular types of thermal wind and present two prominent types of moist wind in natural medium of air. Formulae related to each type are derived and every one of them, represents effects of one type of variation of geostrophic wind with respect to height.

In this article for two case studies mean sea level pressure data, height and wind at standard pressure levels were extracted from NCEP/NCAR archives relatedto a regular network, on the next step divergence quantities, vertical motion, upper levels vertical wind shear and thermal winds in different days were calculated by means of formulated equtions. The results of analysis of upper level vertical wind shear and thermal wind indicated that the maximum values of these two quantities coincide with jet stream axis. This result expresses the direct correlation between these two quantities and all energy producing interactions within the atmosphere. Moreover, this study showed that the maximum values of upper levels vertical wind shear were located between the trough line and the ridge line mid level altitude and their values at high latitudes were fewer than those of low latitudes.

From one point of view; we can divide atmosphere into two mediums. Barotropic medium, that in this medium, density doesn’t change in horizontal direction and isobaric surfaces are parallel to each other in vertical direction. This medium can be motionless, but if in this medium, motion would be taken place, geostrophic wind doesn’t change with respect to height. On the other hand, the baroclinic medium has horizontal gradient of density, and causes various horizontal gradient of pressure with respect to height and implies various horizontal velocity at different levels of the atmosphere. Therefore; geostrophic wind varies with respect to height in this medium. The horizontal gradient of density not only would produce by horizontal gradient of temperature, but also by horizontal gradient of humidity or combination of both. If horizontal gradient of density would be by both horizontal gradient of temperature and horizontal gradient of humidity – as in natural air, not in dry air – in the case; we name vectorial difference of geostrophic wind with respect to height; dense wind. The purpose of this paper is introduction of three versions of dense wind in natural medium of air, not dry air. Basic axis of first version of dense wind is founded by density, second by virtual temperature and third one by thickness of atmospheric layer. Formulae related to each version is derived and every one of them, represents effects of one type of variation of geostrophic wind with respect to height. First version exhibits advection of light or dense air, second represents virtual temperature advection and third one demonstrates advection of thickness in atmospheric layer. Dense wind is powerful tool for consistency of wind field. Therefore, because air is not dry, the variation of the geostrophic wind with respect to height should be describe with better tool, namely dense wind.

In this paper, the effects of the atmospheric boundary layer as well as the inflow turbulence on the performance of a large-scale wind turbine are investigated. The reference wind turbine is the NREL 5 megawatts with a rotor diameter of 126 meters. Wind shear modeling is carried out using the mixing length theory. Due to the importance of turbulence analysis, the Sandia method is applied. According to the reference level, the roughness coefficients of 0. 01, 0. 2 and 0. 5 and disturbances in the roughness of 0. 5 with the intensity of 1, 5 and 15 percent are studied. The aerodynamic forces of the rotor are calculated based on the modified blade element momentum theory. The results show that in the case of maximum roughness the averaged output power is reduced to 160 kW. Moreover, at 15% turbulence intensity, 50 kN and 25 kN are added to the maximum/minimum thrust force value, respectively.

In the present work, wind shear flow (atmospheric boundary layer) effects on aerodynamic performance of the NREL 5MW baseline wind turbine were investigated. In this regard, the steady three-dimensional actuator disk method, based on computational fluid dynamics with low computational cost, was developed, utilizing user-defined function (UDF) in a finite volume-based commercial software package. The rotor was not modeled directly, such that its momentum effect was added to the Navier-Stokes equations as a body force (source term). The developed solver was adopted to compare the flow field behavior around the rotor under uniform and wind shear inflow conditions. Different cases for the rotor azimuth angle were considered to evaluate the radial distribution of rotor power and thrust. Numerical results show that wind shear inflow leads to skew rotor wake, as well as asymmetrical pressure, vorticity, and velocity fields. Moreover, rotor experiences cyclical loading during each rotation. Note, for the selected wind shear profile of this work, the maximum difference in thrust on the rotor plane is about 125KN for each period of rotation.

Wind measurement is important for estimating wind energy potential, but it is relatively cost intensive and often conducted at a narrow height from the ground level. The typical range of most turbine hub heights is from 30-50 m or even higher. Extrapolation on wind data thus becomes necessary to estimate the wind speed at different heights. Doing so requires the essential understanding of wind shear characteristics representative to a location or a region. The analysis is carried out from the vertical profile of meteorological observation collected from 50 m tower at Sathyabama University during the period of 2010-2014. The tower is located near the coastal region in Chennai. The tower is equipped with instruments to measure several meteorological variables. For wind speed and direction, they are routinely measured at different heights, which are considered well suitable for wind shear characterization. In this work, the characteristics of wind shear exponent at the tower were investigated and discussed, with emphasis on temporal (diurnal and monthly) variation and spatial distribution.

The behavior of the oceans and the atmosphere in mid-latitudes may be considered as a small departure from the background rotation of the Earth as a solid body. This provides a ground for the quasigeostrophic (QG) approximation, which is obtained by a formal expansion of the primitive equations in Rossby number that measures the intensity of such departures from the background rotation. The resulting equations, though much simpler than the full set, are still complex enough that it is not always clear what they imply about the nature of their solutions. Therefore, further simplifications have been sought in particular contexts, looking for more tractable models. A model of this kind constructed based on the assumption of a uniform interior QG potential vorticity is discussed in this paper. A further simplification may be obtained by assuming uniform stratification in the atmosphere/ocean. This model has been proposed for explaining some aspects of instability in the atmosphere by Charney and Eady and is used in this paper for studying some effects of wind shear on baroclinic instability.In the Eady model, the wind shear on the lower (ground surface) and upper (tropopause surface) boundaries plays a determining role in the occurrence of instability. However, in the classic form of the baroclinic instability theory of Charney and Eady, wind shear is considered constant with height, and therefore the effect of variations in wind shear on the ground and tropopause surfaces are not covered.According to the Charney–Stern–Pedlosky theorem, with uniform interior potential vorticity, for instability to occur, the wind shear at the upper and lower boundaries must be of the same sign. This theorem provides the necessary condition for instability but gives no further information on the effect of the wind shear at the two boundaries.Then here, the objective is to assess the effects of the wind shear on Eady-like models, that is, models with uniform interior QG potential vorticity. After examining a quadratic vertical zonal wind profile for the basic state as a special case, the arbitrary variation of the wind shear at the two boundaries is studied in an Eady-like model. It is shown that for each wavenumber, there are upper and lower bounds, respectively denoted by g1 and g2, for the ratio of the tropopause wind shear `uzH to the earth's surface wind shearuz `uz0, beyond which instability cannot occur. That is, for instability the ratio must be in the interval g1>`uzH/`uz0>g2 which serves as an additional necessary condition for instability. Considering all the wavenumbers, the lowest value for g2 is found to be 0.3. With nondimensional wavenumbers k*=(2p/L) LR in which L and LR are respectively the dimensional wavelength and Rossby deformation radius, for k*>2.4, instability occurs provided that the wind shear at the lower boundary is greater than that at the upper boundary. For k* between 1 and 1.4, g1 tends to infinity which means that for instability there is no restriction on the magnitude of the wind shear at the upper boundary.

High-rise tubular buildings experience the shear lag phenomenon due to wind load. This phenomenon results in tension in upper storey columns that may adversely affect building stability. Shear lag varies with many factors such as building layout, outer peripheral columns spacing, and load applied to the building. Therefore, it is essential to accurately analyze the shear lag phenomenon by considering these factors, especially, with due emphasize on the pattern of the applied wind loading. This paper attempts to study the effect of wind loading pattern on the shear lag phenomenon. Six load cases are taken from American and Canadian codes to analyze the wind load effects on a 40-storeyed tubular building. The results indicate that axial force distribution changes significantly with change in the loading patterns of the building. A difference in axial force distribution is observed between torsional and non-torsional load cases. Axial force in columns in the case of uniform loading is more significant as compared to partial loading cases. Due to loading on half of the face, axial force distribution becomes unsymmetrical, and a minimum axial force in corner columns is observed. Also, notable differences can be seen in the axial force distribution of load cases having both direction loadings compared to single direction loadings. Axial force distributions in cases of both face loading are unsymmetrical for the central column.

Microburst wind shear is very dangerous and threatening for aircraft in low altitude flight, which makes aircraft uncontrollable and also difficult in forecasting and detection. This is consequential research in order to make the aircraft controllable when encountering the phenomenon. Most studies have simulated aircraft encountering the microburst by applying single-point model. This model, consider location of microburst on the aircraft center of gravity, where microburst must be applied all through fuselage, wing and tail combination. For more realistic simulation, microburst should be applied to more points of aircraft body in addition to C.G., which is known as developed multi-points model. Applying the influence of wind gradients to aircraft body is the advantage of this model. In this paper, results of both single and multi-points was conducted and compared. In comparison of single-point model with existing methods in references, has provided a proper consistency with the tolerance of 10%. Considerable results have shown in comparison of single-point and multi-points model in accordance to flight trajectory response, heading angle and pitching moment to wind shear model and the ability of the multi-points model for modeling of aircraft realistic flight encountering microburst has been proved.

Background & Aim: The purpose of this study was to evaluate the micro-shear bond strength of two kinds of resin-based cements with fluoride release with the usage of five adhesive systems to enamel and dentin. Materials & methods: Bovine flat enamel or dentin surfaces were used in this study. Micro cylinders of resin cement with Xeno Cem Plus (XCP) or Panavia Fluoro Cement (PFC) were bonded to enamel or dentin as followed: XCP or PFC as instructions prior to the usage of their own adhesive systems, Xeno CF II+XCP, SE Bond+PFC, or Clearfil Liner Bond II (CLB) + PFC. After the storage in 37°c water for 24 hrs, micro-shear bond test was applied for all the test groups. The data were statistically analyzed using two-way analysis of variance (ANOVA). After two-way ANOVA, one-way ANOVA and multiple comparisons with Fishers PLSD test were made.Results: Are given as follow (enamel and dentin, mean±SD in MPa); XCP, 13.7±4.0 and 15.5±9.2; PFC, 23.7±10.6 and 15.0±7.3; XCP+XCF II, 35.4±11.5 and 17.1±4.0; PFC+SE, 54.2±9.8 and 41.7±12.0; PFCCLB, 31.39±3.09 and 15.09±4.35. ANOVA (α=0.05) analyze revealed the usage of SE Bond under PFC significantly increased the bond strength to both enamel and dentin. Bonding of Xeno CFII was only improved the bonding to enamel with the application of XCP.Conclusion: Light-cure adhesive systems significantly improve the bonding of current resin cements.