Computational and subjective assessment of ventilated helmet with venturi effect and backvent

Abstract

The effectiveness of providing venturi effect and backvent in full face ventilated motorcycle helmets to provide thermal comfort to a rider is investigated using Computational fluid dynamics (CFD) simulations of air flow and human thermoregulation system in the microclimate of the helmet. Thermal comfort of a motorcycle rider is then predicted using heat indices. The effect of increase in ambient air temperature on the thermal comfort of a rider wearing a modified ventilated helmet, with venturi effect and backvent on the air flow, and temperature distribution in the region above the head is studied. The results are then compared with the conditions when the rider is wearing a full-face, conventional non-ventilated helmet, ventilated helmet with three vents in front and a helmet with only venturi effect. Results are also compared for the conditions when the rider is not wearing any helmet.It is observed that the venturi effect in a ventilated helmet increases the local air velocities in the air gap as compared to a ventilated helmet with three vents in the front of the helmets. Further, it is observed that backvent in venturi helmet augments the thermal comfort of the rider if the ambient air temperature is less than normal body temperature. When air temperatures are higher than the body temperature (36 °C), it is found that the trends are reversed and ventilated helmets are no longer able to provide thermal comfort to the motorcycle rider.For better understanding of effect of newly designed ventilated helmets on the cognitive performance and the willingness of a rider to wear helmets, subjective evaluation of the prototype of venturi helmet is done. Each set of trials required riders to ride with different types of helmets. Based on the results of numerical simulations of ventilation in helmets and responses from subjective human trials, a set of fluid dynamics and design guidelines is also proposed for the helmet manufacturing industries.