Measurements of the temperature and velocity distributions in the very near field of turbulent diffusion flames are made to investigate the significance of flame geometry effects on the plume properties. The flame geometry effects are formulated in terms of a "virtual heat source" as a function of heat release rate and fuel size. It was also shown that the location of virtual heat sources for a round fuel and for a square one are practically identical if the diameter and the side are regarded as the characteristic fuel sizes respectively. The proposed formula for the location of the virtual source seems to be consistent with the results of current works in which the location has been determined in different ways.