Краткое описание

We examine the spatial-development process of a thermally driven flow above the center of a finite-sized heat source, which corresponds to a cooking oven, by using a particle image velocimetry technique. After verifying the accuracy through the comparison with a hot-wire measurement, we investigate the effects of the heat-source thermal conditions on turbulence structures of the flow fields; we carry out three experiments with a gas ring with a heat flux of 2 kW (CaseQ) and an isothermally heated and round-shaped plate with a surface temperature of 373 K (CaseTL) and 473 K (CaseTH). Turbulence structures in the vicinity of the center of a heat source, which are revealed with a proper orthogonal decomposition for instantaneous velocity fields, strongly depend on the thermal condition. The gas ring (CaseQ) leads to inhomogeneous plumes with vortexes, while the isothermally heated plate (CaseTL, CaseTH) causes homogeneous plumes with meandering motions. Despite the apparent differences of turbulence structures near a heat source, the similarity for turbulence statistics of the fully developed plume is preserved among experiments.