A smoke visualisation technique for wake flow from a moving human mankind

An experimental technique using the chemical reaction between acetic acid (CH3COOH) and cyclohexylamine (C6H13N) generated smoke to visualise wake flow from a moving object. A 1/5th scaled manikin was dabbed with cyclohexylamine on specific locations and entered an acetic acid saturated chamber. Smoke was generated via the chemical reaction as the manikin moved through the chamber. High-speed photography and image processing techniques were used to determine whether qualitative and quantitative data could be produced for (1) better understanding the effects of trailing wakes on particle exposure induced by human movement and (2) validation data for computational fluid dynamic (CFD) modelling results. Image analysis showed three phases of manikin movement: peak velocity, deceleration, and stationary. Detailed flow separation images showed that regular vortices were produced at the left shoulder, while flow separating at the hand swirled behind and inwards. Analysis of flow over the head revealed how the separation point shifted from the back of the head to the front as the velocity decreased. The results demonstrated that the experimental method was feasible in producing meaningful results for wake flow phenomena behind a manikin and validation data for CFD simulations. Graphical abstract: [Figure not available: see fulltext.]