Evaluation and validation of a CFD solver adapted to atmospheric flows: Simulation of topography-induced waves

Norbert Rácz, Gergely Kristóf, Tamás Weidinger

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Mountain wave phenomena have been simulated by using a well-known general purpose computational fluid dynamic (CFD) simulation system adapted to atmospheric flow modeling. Mesoscale effects have been taken into account with a novel approach based on a system of transformations and customized volume sources acting in the conservation and governing equations. Simulations of linear hydrostatic wave fields generated by a two-dimensional obstacle were carried out, and the resulting vertical velocity fields were compared against the corresponding analytic solution. Validation with laboratory experiments and full-scale atmospheric flows is a very important step toward the practical application of the method. Performance measures showed good correspondence with measured data concerning flow structures and wave pattern characteristics of non-hydrostatic and nonlinear mountain waves in low Reynolds number flows. For highly nonlinear atmospheric scale conditions, we reproduced the well-documented downslope windstorm at Boulder in January 1972, during which extreme weather conditions, with a wind speed of approximately 60 m s-1, were measured close to the ground. The existence of the hydraulic jump, the strong descent of the stratospheric air, wave breaking regions, and the highly accelerated downslope wind were well reproduced by the model. Evaluation based on normalized mean square error (NMSE), fractional bias (FB), and predictions within a factor of two of observations (FAC2) show good model performance, however, due to the horizontal shift in the flow pattern, a less satisfactory hit rate and correlation value can be observed.

Original languageEnglish
Pages (from-to)239-275
Number of pages37
JournalIdojaras
Volume117
Issue number3
Publication statusPublished - Sep 30 2013

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Keywords

  • CFD simulation
  • Complex terrain
  • Gravity waves
  • Model validation
  • Numerical weather prediction

ASJC Scopus subject areas

  • Atmospheric Science

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