Flow development during low Reynolds number mixed convection

An experimental study was conducted to investigate the flow development inside a horizontal channel subjected to bottom wall heating at low Reynolds numbers. Velocity fields were measured in the vertical mid-plane at five locations along the channel heated section using Particle Image Velocimetry (PIV) technique. The developing lengths of mean and turbulent flows as well as the temperature field showed a strong dependency on the flow rate and the wall temperature. The developing length was found to increase with the increase of bottom wall temperature and/or the decrease of flow rate (i.e. increasing Gr/Re²). A strong correlation between the hydrodynamic and thermal development in the heated section was also observed. The Proper Orthogonal Decomposition (POD) was performed on the turbulent velocity fields. The results revealed the presence of local convective cells near the heated wall along the channel length. The results also showed an influence of flow rate on the size of the convective cell, however, no temperature dependency was observed.