Thermally Driven Upslope Flow Separation in Steep Mountainous Terrain

Thermally driven upslope flow and its separation from mountain slopes are important processes that determine mesoscale and regional flows in mountainous areas. Such flow configurations have applications in mountain meteorology, from pollution dispersion to thunderstorm genesis. A combined experimental and theoretical study toward improving our understanding of the mechanisms governing upslope flow processes, in particular, buoyancy influenced flow separation and upslope velocity at separation are presented. The experiments were performed in a 125x35x30cm water tank, using an inclined (5° to 45° from the horizontal) electrical embedded foil as the heated slope. Particle tracking Velocimetry (PTV) and Feature Tracking Visualizations (FTV) color mapped according to track length and/or velocity were used for the diagnostics of the flow separation point and mean upslope velocity at separation. Theoretical arguments are presented to explain the results for steep slopes (slope angles ≥ 20°).