Experimental study of the velocity field around a falling needle viscometer

Fully developed velocity profiles around the side of a needle falling at terminal velocity in a falling needle viscometer and the flow disturbance region near the ends of the needle were experimentally investigated. A flow visualization technique was used to obtain the main features of the flow field around the falling needle. Comparisons made between the experimental and predicted fully developed velocity profile showed good agreement. The regions where the flow field is disturbed by the needle ends were analyzed from photographs and found to be about 6% of the total needle length.