Infotaxis in a turbulent 3D channel flow

In this paper, the infotaxis-based search algorithm is tested in several simulated turbulent channel flows. The algorithm is adapted to detect plumes of high concentration instead of independent particles. Direct numerical simulation is used to test this adapted search algorithm by detection of high concentration levels in turbulent channel flows with a Schmidt number Sc of 1.0 and Reynolds numbers Re of 5600 and 28000. For the direct numerical simulation with the adapted algorithm, there is a positive relation between the initial distances to the source and the running time, which holds for Re = 5600 but which is not observed at Re = 28000. This is caused by the low Schmidt number and the high velocity, which leads the searcher to the source very fast after the first detection of a high concentration level. The search algorithm is also tested in reverse to detect whether a fluid is well-mixed. The time required for a detection of a too high or low concentration and the number of detections are used as measures for success. By applying the algorithm to some prescribed concentration distributions in two dimensions, it is found that the method is very sensitive to the threshold values for the mixing indicators.