Search Results
You are looking at 1 - 2 of 2 items for :
- Author or Editor: D. K. LILLY x
- Monthly Weather Review x
- Refine by Access: Content accessible to me x
Abstract
A system is proposed for grid allocation and differencing of apparently general applicability to purely marching-type systems of equations of fluid dynamics. The method is based on casting of the equations into the conservation form, which then permits use of a staggered space-time grid system with interpolations required only in certain linear terms. The method is illustrated by application to two systems of equations, on one of which numerical experiments have been successfully performed. Advantages and drawbacks of the method are described in comparison to other currently used grid systems, and the possibility and desirability of parametric simulation of turbulent eddy exchange processes are discussed.
Abstract
A system is proposed for grid allocation and differencing of apparently general applicability to purely marching-type systems of equations of fluid dynamics. The method is based on casting of the equations into the conservation form, which then permits use of a staggered space-time grid system with interpolations required only in certain linear terms. The method is illustrated by application to two systems of equations, on one of which numerical experiments have been successfully performed. Advantages and drawbacks of the method are described in comparison to other currently used grid systems, and the possibility and desirability of parametric simulation of turbulent eddy exchange processes are discussed.
Abstract
The lee flow disturbances produced by the Front Range of the Colorado Rockies have been quantitatively observed in a continuing program at the National Center for Atmospheric Research. The results of midtroposphere constant-volume ballon and aircraft flights in the winter of 1966/67 are here presented. The relative merits and limitations of the two methods are compared with respect to various operational and inherent phenomenological difficulties of the subject. The nonstationarity of many flow features is inescapable and poses serious problems for data evaluation and theory. Schematically, we distinguish between smooth, wavy, and hydraulic jump-type flow patterns, but also observe some cases that do not fit well into any of these categories. The stronger stationary wave features can be compared with the “stable” resonance modes computed from stationary linear theory, that is, those modes which are insensitive to small changes in the upstream flow. The frequent occurrence of erratic and nonstationary flows may relate to the frequent existence of “unstable” or sensitive modes in the linear theory predictions. Examples of smooth and hydraulic jumplike flows are also shown and qualitatively compared to current theoretical predictions. Some suggestions are made for improvement of observational techniques in the downslope boundary layer.
Abstract
The lee flow disturbances produced by the Front Range of the Colorado Rockies have been quantitatively observed in a continuing program at the National Center for Atmospheric Research. The results of midtroposphere constant-volume ballon and aircraft flights in the winter of 1966/67 are here presented. The relative merits and limitations of the two methods are compared with respect to various operational and inherent phenomenological difficulties of the subject. The nonstationarity of many flow features is inescapable and poses serious problems for data evaluation and theory. Schematically, we distinguish between smooth, wavy, and hydraulic jump-type flow patterns, but also observe some cases that do not fit well into any of these categories. The stronger stationary wave features can be compared with the “stable” resonance modes computed from stationary linear theory, that is, those modes which are insensitive to small changes in the upstream flow. The frequent occurrence of erratic and nonstationary flows may relate to the frequent existence of “unstable” or sensitive modes in the linear theory predictions. Examples of smooth and hydraulic jumplike flows are also shown and qualitatively compared to current theoretical predictions. Some suggestions are made for improvement of observational techniques in the downslope boundary layer.
