Figure 4.

Synthetic schlieren images of the forced convection and thermal wake produced by someone walking slowly through a quiescent room. (a) Thermal convection is not visible in front of the person but a thermal signal is clearly visible in the high-Reynolds-number wake of a person walking without breathing. (b) The thermal signature of the wake one second after the passage of the person. Significant mixing has occurred without obvious effects of buoyancy. (c) Air exhaled by nasal breathing is swept around the head by the motion and entrained into the wake. (d) Although laughing still produces a jet that reaches in front of the subject, it is soon overtaken and the associated breath is incorporated into the wake.