The pattern formation of a Poiseuille flow in a rectangular duct, which is heated from below, is studied experimentally for the Reynolds number Re = 200 within the Rayleigh number range 4 ×108 ≤ Ra ≤ 7 ×108 . The channel has an aspect ratio of Γ
= width : height = 25 : 2. As working fluid, water (Pr ≈ 6) is used. In order to study the influence of buoyancy on the forced flow, velocity fields are measured plane parallel to the heated bottom plate by means of Particle Image Velocimetry (PIV). Furthermore, the measured data is analyzed concerning the flow structure formation as a function of the temperature difference between the inflow and the bottom of the duct. In this connection, two different mechanisms can be distinguished, which cause the transition from a laminar to a turbulent flow: a successively progressing transition on the one hand and, above a certain Archimedes number Ar, an abrupt transition.
- Rayleigh Number
- Mixed Convection
- Instantaneous Velocity
- Rectangular Duct
- Longitudinal Vortex
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.