The total length of the rectangular channel is 60 mm but by model, I am getting flow length with a range of 70 mm to 260 mm from 0.1 sec to 1.2 sec respectively. The channel radius is varied from 200 to 400 um. I calculated the maximum flow length of 30 mm experimentally . Capillary flow terms are the same as a previously derived Washburn model. So what can be the issue for my model? Need suggestions.