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Studies of internal gravity waves in the stably stratified troposphereRees, J. M. January 1988 (has links)
No description available.
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Viscous-inviscid interaction in a transonic flow caused by a discontinuity in wall curvatureYumashev, Dmitry January 2010 (has links)
The work addresses an important question of whether a discontinuity in wall curvature can cause boundary layer separation at transonic speeds. Firstly an inviscid transonic flow in the vicinity of a curvature break is analysed. Depending on the ratio of the curvatures, several physically different regimes can exist, including a special type of supersonic flows which decelerate to subsonic speeds without a shock wave, transonic Prandtl-Meyer flow and supersonic flows with a weak shock. It is shown that if the flow can be extended beyond the limiting characteristic, it subsequently develops a shock wave. As a consequence, a fundamental link between the local and the global flow patterns is observed in our problem. From an asymptotic analysis of the Karman-Guderley equation it follows that the curvature discontinuity leads to singular pressure gradients upstream and downstream of the break point. To find these gradients, we perform computations and employ both the hodograph method and the phase portrait technique. The focus is then turned to analysing how the given pressure distribution affects the boundary layer. It is demonstrated that the singular pressure gradient, which appears to be proportional to the inverse cubic root of the distance form the curvature break, corresponds to a special resonant case for the boundary layer upstream of the singularity. Consequently, the boundary layer approaches the interaction region in a pre-separated form. This changes the background on which the viscous-inviscid interaction develops, allowing to construct an asymptotic theory of the incipient viscous-inviscid interaction for our particular problem. The analysis of the interaction which takes place near a weak curvature discontinuity leads to a typical three-tier structure. It appears to be possible to obtain analytical solutions in all the tiers of the triple deck when the curvature break is small. As a result, the interaction equation may be derived in a closed form. The analytical solution of the interaction equation reveals a local minimum in the skin friction distribution, suggesting that a local recirculation zone can develop near the curvature break. In fact, the recirculation zone is formed when the ratio of the curvatures is represented as a series based on negative powers of the logarithm of the Reynolds number. This proves that a discontinuity in wall curvature does evoke boundary layer separation at transonic speeds. The result is fundamentally different from the effect of a curvature break at subsonic and supersonic speeds, as no separation takes place in these two regimes (Messiter & Hu 1975).
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An examination of lake breezes in southern ManitobaCurry, Michelle 01 1900 (has links)
Lakes represent a major topographic feature in southern Manitoba, having a direct meteorological influence on a number of communities, including Winnipeg. Therefore, it is crucial that we have an understanding of the characteristics of lake breezes in the region and the influence that they can have on local weather. The Effects of Lake Breezes on Weather in Manitoba (ELBOW-MB) project in 2013 sought to fill in the gaps in our current knowledge of lake breezes in southern Manitoba. The primary research objectives of this thesis are to: (1) provide a radar-based climatology of lake breeze frequency and characteristics and, (2) to characterize the detailed thermodynamic and kinematic properties of lake breezes and lake-breeze fronts. The two results papers presented within this thesis represent the first detailed analysis of lake breezes in southern Manitoba and help to fill important gaps in our knowledge about the occurrence and characteristics of lake-breeze circulations. / February 2016
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Analysis of lateral boundary effects on inner domain of COAMPS / Analysis of lateral boundary effects on inner domain of Coupled Ocean/Atmosphere Mesoscale Prediction SystemHarris, Brad G. 09 1900 (has links)
Approved for public release; distribution is unlimited. / One of the major problems with a Limited Area Model is the introduction of error from the lateral boundaries. The boundary condition provides a source of forcing to the interior of the model. This forcing typically originates from a global model such as NOGAPS. The transition at the boundary from one model to another invariably produces errors. Traditionally, the way to minimize boundary error is to move the boundary as far away from the area of interest as possible. In this way, the errors do not have time to infest the LAM with "bad" information. Moving the boundary far away from the area of interest increases the computational forecast load and decreases its timeliness. This study looks at how close the lateral boundary can be to minimize computational time and still maintain a forecast that is useful. It was found that when the entire inner COAMPS nest was analyzed, the differences between the control forecast and the test forecast where within the natural variability of the control grid. It was also found that there where localized areas within the model domain that differed between the control domain and the test domain by up to 20 mb for the sea level pressure after a six day forecast. / Lieutenant, United States Navy
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Some progress on Prandtl's system. / CUHK electronic theses & dissertations collectionJanuary 2003 (has links)
Chu Shun Yin. / "August 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 55-60). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.
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An experimental study of turbulent natural convection in water and mercuryJain, Ashok January 2011 (has links)
Digitized by Kansas Correctional Industries
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Turbulence structure within an inclined laboratory convection tankNance, Jon D. 09 February 1989 (has links)
A baroclinic, convective mixed-layer was modeled, using
water, in a laboratory convection tank identical to that
used in the free convection study of Deardorff and Willis
(1985). Baroclinicity and mean-flow shearing were achieved
by tilting the tank by an angle of 1O⁰. The resulting
mechanical-production rate of turbulence kinetic energy was
comparable in magnitude to the buoyancy-production rate at
mid-levels within the mixed-layer.
Velocities were obtained by taking time-lapse
photographs of neutrally-buoyant oil droplets suspended in
the mixed-layer fluid. Variances and other statistical
descriptors of the turbulence obtained from these
velocities are presented in comparison to the free
convection results of Deardorff and Willis (1985). The
deviation of the present results from those of Deardorff
and Willis (1985) are assumed to be related to the effects
of mean-flow shearing and are explained wherever possible
with the aid of an appropriate kinetic energy budget
(kinetic energy, here, refers to the kinetic energy of the
turbulence and is not to be confused with the kinetic
energy of the mean-flow).
The results indicate that a maximum in downstream
horizontal kinetic energy at mid-levels within the mixed layer
was generated by shear-production and, also, by
conversion from vertical kinetic energy. In the lower
mixed-layer, vertical kinetic energy was amplified by a
mechanical-production term associated with the divergence
of the mean vertical velocity. Total turbulence kinetic
energy, normalized by the square of the convective velocity
scale, was much larger at mid-levels than in Deardorff and
Willis (1985) due to mechanical-production which is not
accounted for by simple mixed-layer scaling. Horizontal
turbulence structure was predominately controlled by
convection while vertical turbulence structure was
significantly altered by mean-flow shearing. / Graduation date: 1989
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A nonlocal mixing formulation for the atmospheric boundary layerFrech, Michael C. 17 December 1993 (has links)
A two-scale approach for the turbulent mixing of momentum in an unstable
stratified boundary layer is proposed in an attempt to eliminate existing inconsistencies
between parameterized mixing of heat and momentum. The parameterization
of the large eddy stress is suitable for simple boundary layer models where computational
efficiency is important. We test the proposed formulation in a simple
boundary layer model and compare predicted momentum profiles with Lidar mean
momentum profiles from FIFE 1989. We examine the sensitivity of the proposed
mixing scheme to baroclinicity. While the proposed two-scale approach is able to
better predict observed conditions of well mixed momentum profiles, the complexity
of momentum transport in baroclinic conditions is not well approximated. / Graduation date: 1994
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Turbulent structure in the bora and stable boundary layerFrank, Helmut P. 03 April 1986 (has links)
An eigenvector analysis of the velocity-temperature correlation
matrix is applied to clear-air turbulence measured by aircraft in the
Bora. The eigenvectors are identified with the main eddies of the
turbulence. This study attempts to infer the three-dimensional
structure of these eddies. The results are compared with turbulent
structures in the stable boundary layer. The turbulence in the
strongly stratified boundary layer appears to be dominated by double
roller eddies with their axes of rotation tilted in the shear direction.
The clear-air turbulence shows a larger variety of motion
types. / Graduation date: 1986
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Parameterization of shallow convection in the boundary layerChu, Cheng-tsong 23 September 1986 (has links)
A shallow convection scheme is derived from several data sets
(BOMEX, GATE, AMTEX, BLX83) and developed for the OSU 1-D boundary
layer model. Results of the model structure and characteristics of
the saturation point (SP) profile are compared against the constant
cloud diffusivity scheme of Tiedtke (1983) and the ECMWF boundary
layer parameterization scheme.
The results indicate that the primary mechanism that transports
moisture away from the lower boundary layer is the boundary layer
turbulent flux and that the boundary turbulent mixing alone is
capable of maintaining an apparent moisture source near the
inversion. While the sensible heat flux over ocean becomes quite
small after a few hours of model simulation, the virtual heat flux
remains positive and the boundary layer remains in the unstable
regime. / Graduation date: 1987
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