Abstract

This paper describes some fluid dynamic considerations for attaining realistic odor presentation using an olfactory display. Molecular diffusion is an extremely slow process and odor molecules released from their source are spread by being carried off by airflow. Therefore, we propose to use a computational fluid dynamics (CFD) simulation in conjunction with the olfactory display. The CFD solver is employed to calculate the turbulent airflow field in the given environment and the dispersal of odor molecules from their source. The simulation result is used to reproduce at the nose the realistic change in the odor concentration with time and space. However, our initial sensory test for evaluating the proposed method was not completely successful, and we also found some discrepancies between our real-life olfactory sensation and the experience of the CFD-based olfactory display. Here we report some insights to overcome these problems. In the initial sensory test, a nontrivial portion of the subjects did not properly recognize the spatial variation in the odor intensity. The result of our recent sensory test is presented in this paper to show that better contrast in the perceived odor intensity can be provided when the concentration range of the released odor is adjusted for the variation in the olfactory sensitivity of individual subjects. We noted that olfactory adaptation occurred more quickly in the initial sensory test of the CFD-based olfactory display than in real environments. In this paper, we show that olfactory adaptation can be alleviated by modulating the odor concentration randomly to mimic the random fluctuations of the turbulent flow fields in real environments. We also noted in our initial sensory test that there were sometimes discrepancies between our olfactory sensation in real environments and the simulated odor distribution. We show in this paper that the discrepancy can be attributed to the convection caused by the human body temperature that brings an odor vapor that is drifting around our feet up to our noses.

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