Date of Graduation


Document Type


Degree Name

Master of Science in Chemical Engineering (MSChE)

Degree Level



Chemical Engineering


Tom O. Spicer, III

Committee Member

Heather Walker

Second Committee Member

Larry Roe


Flow Visualization, Jack Rabbit II, Wind Tunnel


Unintentional releases of hazardous gases have led to significant injuries and fatalities in severe cases. Field tests can be used to release hazardous gases to document and evaluate the behavior of the gases. Chlorine is an especially hazardous gas due to its toxicity. The Jack Rabbit II Phase I field tests released chlorine within a mock urban environment (MUE) consisting of Conex containers arranged in rows to simulate buildings and streets. The number of field tests is limited by both expense and time. Simulation of a field test using a wind tunnel model can provide additional data and opportunity for study of relevant phenomena at reduced cost.

This study focused on Phase I of the Jack Rabbit II trials which consisted of five vertically downward chlorine releases into the MUE. The chlorine deflected horizontally off the underlying concrete pad to spread radially outward into the MUE. In the wind tunnel model, the field releases were simulated by releasing a gas mixture of theater fog, sulfur hexafluoride, carbon dioxide, and air into the 1:50 scale tunnel model through an area source. A polycarbonate disk was positioned above the area source to deflect the vertically upward tunnel release into a radially spreading horizontal wall jet similar to what was observed in the field tests.

The flow rate, composition, and wall jet initial height are source gas parameters that must be determined to model the field tests. Jack Rabbit II Trial 4 was used to determine the source gas parameters by adjusting each parameter and comparing the gas behavior of the tunnel model to the behavior of the field trial. Once the video record parameters were determined, the parameters were validated by comparison to Jack Rabbit II Trial 5.

Jack Rabbit II Trial 3 had inconsistent wind data to model with confidence in the wind tunnel. The tunnel model was used to estimate the wind direction during Trial 3 by simulating different wind directions and comparing release behavior of the tunnel releases and field test. The tunnel model was further used to determine the maximum upwind extent of the field chlorine release if the MUE offered the least upwind resistance by changing the wind direction.

The release method and parameters determined in this study were used in further tunnel model simulations to measure the concentration of the release gas in instrument locations with the MUE. The release method was further used to study the wind direction within the MUE at specific locations and planes.

Additional videos are included along with this paper to demonstrate the tunnel model simulating the field releases. The videos show a comparison of the field release and the similar behavior of the tunnel release. Each of the three videos is labeled with the trial number of the field release that the wind tunnel model is simulating: Flow Visualization of Jack Rabbit II Trial 3, 4, and 5.

Flow Visualization of Jack Rabbit II Trial 3.mp4 (155191 kB)
Flow Visualization Trial 3

Flow Visualization of Jack Rabbit II Trial 4.mp4 (155415 kB)
Flow Visualization Trial 4

Flow Visualization of Jack Rabbit II Trial 5.mp4 (155139 kB)
Flow Visualization Trial 5