Computing Streamfunction and Velocity Potential in a Limited Domain of Arbitrary Shape. Part II: Numerical Methods and Test Experiments |
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Authors: | CAO Jie and Qin XU |
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Institution: | Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, USA,NOAA/National Severe Storms Laboratory, Norman, Oklahoma, USA |
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Abstract: | Built on the integral formulas in Part I, numerical
methods are developed for computing velocity potential and
streamfunction in a limited domain. When there is no inner boundary
(around a data hole) inside the domain, the total solution is the
sum of the internally and externally induced parts. For the
internally induced part, three numerical schemes (grid-staggering,
local-nesting and piecewise continuous integration) are designed to
deal with the singularity of the Green's function encountered in
numerical calculations.
For the externally induced part, by setting the velocity potential
(or streamfunction) component to zero, the other component of the
solution can be computed in two ways: (1) Solve for the density
function from its boundary integral equation and then construct the
solution from the boundary integral of the density function. (2) Use
the Cauchy integral to construct the solution directly. The boundary
integral can be discretized on a uniform grid along the boundary. By
using local-nesting (or piecewise continuous integration), the
scheme is refined to enhance the discretization accuracy of the
boundary integral around each corner point (or along the entire
boundary).
When the domain is not free of data holes, the total solution
contains a data-hole--induced part, and the Cauchy integral method
is extended to construct the externally induced solution with
irregular external and internal boundaries. An automated algorithm
is designed to facilitate the integrations along the irregular
external and internal boundaries. Numerical experiments are
performed to evaluate the accuracy and efficiency of each scheme
relative to others. |
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Keywords: | numerical method streamfunction velocity potential domain of arbitrary shape |
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