Drag Measurements with High Blockage

The paper presents new data to document the effective test area in a model ¾ open jet wind tunnel with a long test section using drag measurements. The drag on MIRA Pickup models (up to 20% blockage) was tested and found to be virtually independent of blockage when tested in a non-resonant test section with L/D ratio of about 8. An analysis of these test results is presented to predict the required test section L/D as a function of blockage. In addition, the effects of plenum dimensions are presented. Based on these results, the test sections of present open jet test sections have a limited range for testing models without corrections for the effects of blockage, model location, and test section length. A longer test section enables direct measurement of drag even with high blockage models. Testing with higher blockage can mean lower test facility costs.

The test section design technology described in this report is the subject of a pending patent application.