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Titel |
Turbulent boundary layer flow over a steep 2-D hill: atmospheric stability effects |
VerfasserIn |
Wei Zhang, Fernando Porté-Agel |
Konferenz |
EGU General Assembly 2011
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 13 (2011) |
Datensatznummer |
250056784
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Zusammenfassung |
Complex topography affects the distribution of turbulent fluxes of momentum and
heat in thermally stratified boundary layers. Neutrally stratified boundary-layer
flows over simplified topography (for example, blocks or sinusoidal hills) have been
extensively studied by wind-tunnel experiments and numerical simulation such as
Large-Eddy Simulation (LES). Atmospheric stability, however, is seldom considered
due to the difficulty of physical simulation in wind tunnel. In addition, accurate
prediction of separated flow induced by steep hills remains a challenge to LES
modeling.
Experimental investigation of various thermal stratification effects (neutral, stable and
convective) on the boundary-layer flows over a steep 2-D hill were conducted at the Saint
Anthony Falls Laboratory atmospheric boundary-layer wind tunnel. The 2-D model hill has a
steepest slope of 0.73 and its shape follows h=H cos(Ï x/L) for -L/2 -¤ x -¤ -L/2
(H=7cm and L=14.5 cm). The hill is fully immersed in the surface layer with a
ratio of the height to the boundary layer depth (H/δ) about 0.12. High-resolution
Particle Image Velocimetry (PIV) provided dynamic flow information of the onset of
separation, the recirculation zone and flow reattachment location. Turbulent momentum
and heat fluxes as the function of height were characterized using a triple-wire at
selected stream-wise locations. Emphasis is made on the effects of atmospheric
stability on the dynamics of flow separation induced by the hill as well as the flow
recovery process. The present study can hopefully improve our understanding of
thermally-stratified boundary layer flow behavior over a steep 2-D hill from well-controlled
tests, and provide reliable database for development and validation of LES models. |
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