Bluff Body Dynamic Distortion Generators: Design and RANS CFD Analysis of Dynamic StreamVanes

StreamVanes and ScreenVanes, developed at Virginia Tech, are used to create realistic swirl and pressure distortion profiles for engine testing. However, they are limited to producing steady distortion patterns, restricting their applicability in simulating dynamic inlet flow conditions. This research introduces a next-generation StreamVane capable of generating unsteady distortion to better evaluate modern aircraft engines. Serpentine diffusers naturally generate unsteady, counter-rotating vortices that can negatively impact turbomachinery. This study explored leveraging the natural periodic vortex shedding of bluff bodies with the steady distortion profiles of StreamVanes in order to design a passive method to replicate this type of real-world flow. Two types of bluff bodies were integrated into a twin-swirl StreamVane design: square prisms, which produce predictable vortex streets based on their Strouhal number, and the BeVERLI Hill, a symmetric hill geometry known for its asymmetric, chaotic vortex shedding. These configurations were analyzed using RANS/URANS CFD to evaluate their interaction with the steady StreamVane flow, their frequency content, and the influence of bluff body size. The CFD results provided a proof-of-concept for this type of passive, unsteady distortion generator. It was found that the vortices were shed similarly to how they would if the bluff bodies were on their own, and they were carried in the direction of the flow from the twin swirl StreamVane as they moved downstream. Additionally, there was evidence of the frequencies scaling with bluff body size that roughly aligned with expected relationships. However, more extensive testing of the designs is needed to fully understand how bluff bodies can be sized to generate specific dynamic distortion profiles with specific average frequencies at a given AIP. This research provides a solid baseline from which to further develop dynamic StreamVane technology.