Eddy가 존재하는 cavity를 내포한 계를 이용하여 평균 체류 시간을 실험을 통하여 조사하였다. 펄스입력에 대한 자극 응답 곡선의 first moment로부터 결정되는 system mean time과 계의 부피를 부피유속으로 나누어 얻어지는 mean residence time의 관계를 집중적으로 조사하였다. 일종의 분리 영역인 eddy가 없는 경우 system mean time과 mean residence time은 크기가 같다. 그러나 eddy를 내포하는 cavity가 존재하는 경우 system mean time은 mean residence time 보다 크며 Reynold수가 작을수록 cavity의 깊이가 깊을수록 그 차이는 더욱 커지는 경향을 보았다.

The mean residence time of a material in the system containing an eddy was calculated with the experimental results. The relation between the system mean time which was obtained by the first moment of the stimulus-response curve and the mean residence time which was the ratio of the system volume to the fluid flow rate was investigated. If there was no eddy in the system, the system mean time equaled to the mean residence time. For the system containing an eddy, the system mean time was greater than the mean residence time. And the numerical value of the discrepancy between them increased with the aspect ratio, AR and inversely with the Reynolds number.