Similarities and Differences between Hot-film Anemometry and Particle Image Velocimetry in Open Channels

In this study a comparison between hot-film anemometry and Particle Image Velocimetry (PIV) measurements in open channels is investigated. For this reason individual experiments with these two methods were conducted. Initially, experiments were performed with hot-film anemometry method and then with PIV method in open channels with the same conditions. The comparison is curried out for two cases of study: a) impermeable bed and b) permeable bed. For the simulation of the permeable bed a porous filter with porous thicknesss'=2 cm and porosity ɛ=0.75 was used. Sixteen (16) laboratory experiments were carried out, eight (8) for each case. Velocity distribution and turbulent characteristics of the flow above the impermeable bed and above the porous filters for all the different total water heights and for the same channel slope were evaluated. Results show that the different method for experimental measurements influence in some cases the turbulent characteristics of the flow, especially in the case of permeable bed. Also the results show that there is a good agreement between these two methods, both for permeable and impermeable bed, regarding the velocity distribution.