Study of turbulent structure with hot-wires smaller than the viscous length

Measurements of the mean velocity profile and streamwise turbulence intensity profile are reported with the small U probes. Comparison of the turbulent intensity data with larger probes shows that the smaller probes measure more energy due to their better spatial resolution. The data measured by the small probes are also analyzed to determine the burst frequency at various distances from the wall and at two Reynolds numbers. The results show that the burst frequency scaled with respect to the wall parameters is less a function of Reynolds number than the burst frequency scaled with respect to the outer flow variables. To obtain more quantitative information regarding the turbulence structure, measurements are reported with two small U probes. From the correlation coefficient deduced from the measured data, it concluded that the turbulence structure increases in size in both the spanwise and transverse direction as the distance from the wall increases.