PIV and numerical analysis of natural convection in tilted enclosures filled with air and with opposite active walls

In this paper an analysis of natural convection in an enclosure filled with air and with opposite heated and cooled walls is performed; four different tilts of the cavity are investigated: θ=0,π6,π3 and π2. A complete definition of the velocity field in the cavity is obtained through PIV (particle image velocimetry) and is shown in terms of velocity contour maps and streamlines; the same results are obtained through numerical analysis and compared with the experimental ones: a very good agreement is found. In addition the thermal field is calculated and the value of the Nusselt number (Nu) next to the how wall is reported. A brief overview on a new PIV aspect is also discussed: since very small velocity fields are investigated, the effect of heating by the pulsed laser light becomes relevant, thus introducing a disturb on the measuring field that has never been considered for PIV, since it is generally treated as a completely non-intrusive technique.