Date of Award
Doctor of Philosophy (PhD)
Mechanical and Aerospace Engineering
Hypersonic aerodynamics., Hydrodynamics., Aeroacoustics., Computational fluid dynamics.
Vibrations plague wind tunnel data and are caused by several factors, such as sensor placement, flow inconsistencies due to imperfect collimation, and the sub-scale model mechanically vibrating upon its mounting apparatus, called a sting. This study focuses on the latter source, particularly at hypersonic velocities, due to fundamental changes that occur within the flow at these speeds. These flow changes differ from those at lower velocities, where the mechanical vibrations are generally superimposed upon the data and thus are easily remove via notch or band-stop filtering. Therefore, traditional post-processing noise removal techniques are not as effective. This dissertation presents an investigation into these flow changes as well as a computational fluid dynamics (CFD) method to simulate the behavior in order to more effectively characterize, and predict, how sting vibrations affect the data collected within a hypersonic wind tunnel. The CFD techniques used are based on a mesh-free Lagrangian technique called Smoothed Particle Hydrodynamics (SPH) in which the solid boundaries are able to move about as necessary, i.e. model vibrations, in contrast to more traditional, static gridded CFD codes. The SPH method is first verified in 2D and 3D flow cases, and then validated against actual wind tunnel data, wherein the noise itself it modeled and matched. Confident in the method’s accuracy, simulations are then performed with vibrations based on a hypothetical sting. The results show the sting’s frequencies are not superimposed upon the output data, with some frequencies shifted or attenuated, which is caused by fundamental changes in the hypersonic flow itself.
Englestad, Tyler, "Study of effects of rigid body vibrations on external hypersonic flow using smoothed particle hydrodynamics" (2019). Dissertations. 189.