The ALDL research team is developing a high-speed three-dimensional density measurement technique. In order to develop this technique, a flow field with strong density variations was necessary. Thus, the flow field over a hemispherical turret was chosen. Flow phenomena such as a necklace vortex, a separated shear layer, and a rear turbulent wake are typical for a hemisphere in a freestream. A shockwave is also possible at a high enough MACH number and this occurs before the separated shear layer. A transonic wind tunnel was also created to mount this hemispherical turret.         

                                                                            Average Schlieren Image of                                                 Single-Shot Schlieren Image of                                                                                                                                          Flow Over Hemispherical Turret                                            Flow Over Hemispherical Turret                                    

The acetone PLIF technique is being used to obtain 2D-Laser Induced Fluorescence images of this flow field. Density information can be obtained from these images. In the future, a high-speed scanning mirror will be used to obtain sets of acetone PLIF images scanned laterally across the test section. These images will then be stacked together and three dimensional images will be created. The density information from each image will give a complete picture of the 3D density field.

This high-speed three-dimensional density measurement technique is important because aero-optic distortions can be calculated from the index of refraction, which is directly related to density.

                                                                                                                             Acetone PLIF Experimental Set-Up

                                                                                        Single-Shot Acetone PLIF Image (After Laser Sheet Non-Uniformity Correction)

Brian S. Thurow, Associate Professor, Thurow@auburn.edu

Department of Aerospace Engineering

211 Davis Hall , Auburn University, AL 36849-5338

Phone: (334) 844-6827      Fax: (334) 844-6803