摘要 :
In this part-review part-new work, studies on branching tube flows are described. These are based on modelling for increased flow rates as well as on direct numerical simulations and are motivated by applications to the cardiovasc...
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In this part-review part-new work, studies on branching tube flows are described. These are based on modelling for increased flow rates as well as on direct numerical simulations and are motivated by applications to the cardiovascular system, lung airways and cerebral arteriovenous malformations. Small pressure differentials acting across a multiple branching are considered first, followed by substantial pressure differentials in a side branching, multiple branching or basic three-dimensional branching. All cases include a comparison of results between the modelling and the direct simulations. Wall shear, pressure variation, influence lengths, and separation or its suppression are examined, showing in particular sudden spatial adjustment of the pressure'between mother and daughter tubes, nonunique flow patterns and a linear increase of flow rate with increasing number of daughters, dependent on the specific conditions. The agreement between modelling and direct simulations is generally close at moderate flow rates, suggesting their combined use in the biomedical applications.
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摘要 :
This study is motivated by applications to near-wall shear flow (ⅰ) as a longitudinal wall shaping starts, (ⅱ) around a surface obstacle, or (ⅲ) through a pipe bend. All are shown to be governed, at relatively high flow rates, ...
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This study is motivated by applications to near-wall shear flow (ⅰ) as a longitudinal wall shaping starts, (ⅱ) around a surface obstacle, or (ⅲ) through a pipe bend. All are shown to be governed, at relatively high flow rates, by essentially the same theoretical problem. This concerns three-dimensional nonlinear longitudinal vortex-like motion under a prescribed displacement which continues to increase with distance downstream. Symmetry-plane solutions are obtained mainly through forward marching computation followed by analysis of the far-downstream response. The behaviour far downstream is found to involve either a strengthening attachment or an increasing three-dimensional separation (lift-off) with no backflow.
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摘要 :
Forecasts of noise pollution from a highway line segment noise source are obtained from a sound propagation model utilizing effective sound speed profiles derived from a Numerical Weather Prediction (NWP) limited area forecast wit...
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Forecasts of noise pollution from a highway line segment noise source are obtained from a sound propagation model utilizing effective sound speed profiles derived from a Numerical Weather Prediction (NWP) limited area forecast with 1 km horizontal resolution and near-ground vertical resolution finer than 20 m. Methods for temporal along with horizontal and vertical spatial nesting are demonstrated within the NWP model for maintaining forecast feasibility. It is shown that vertical nesting can improve the prediction of finer structures in near-ground temperature and velocity profiles, such as morning temperature inversions and low level jet-like features. Accurate representation of these features is shown to be important for modeling sound refraction phenomena and for enabling accurate noise assessment. Comparisons are made using the parabolic equation model for predictions with profiles derived from NWP simulations and from field experiment observations during mornings on November 7 and 8, 2006 in Phoenix, Arizona. The challenges faced in simulating accurate meteorological profiles at high resolution for sound propagation applications are highlighted and areas for possible improvement are discussed.
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