Statistical Speckle Study of Copper Nanofluids

We report on a statistical analysis of copper nanofluid speckle image patterns. The far-field speckle images are formed by illuminating the copper nanoparticle (CuNP) suspension using low power continuous wave laser light at 532 nm. The nanofluids is prepared by nanosecond pulsed laser ablation of the highly pure copper target in polysiloxane oil. A stochastic approach based on the fractional Brownian motion and the classical frequential method is applied on the speckle patterns. These methods enable us to extract statistical parameters such as mean speckle size, Hurst coefficient and saturation of variance. Our results show that the mean speckle size remains unchanged with respect to time while the Hurst exponent and the saturation of variance exhibit changes. It has been shown that the stochastic approach makes it possible to characterize the copper nanofluid. The statistical analysis indicates that the Brownian motion of nanoparticles play important role in thermal properties of the copper nanofluids. Including the Brownian motion, the thermal conductivity of the copper nanofluids is calculated.