List of Submitted Art-in-science Entries

This video shows the detonation-tube driven initiation of our rotating detonation engine looking in from the back. The video is captured at 100,000 frames/second and slowed down to ~1/6000th speed here. In this particular case a perforated acoustic liner was installed in the outer wall which lead to some interesting unintended interactions during the initiation process.

Unraveling the dynamics of wall geometry and the corresponding two-dimensional flow field using digital image correlation and particle image velocity measurements.

Multi-agent inspection missions are a key enabler for recent advances in on-orbit operations such as servicing, manufacturing, and debris removal. The ability to leverage distributed assets to collaboratively inspect a single target increases the applicability of an inspection to targets that may be in an uncontrolled rotation or have a strict time window in which inspection must take place. Often optimal trajectory design for complex scenarios, such as a multi-agent inspection, is prohibitively computationally expensive to take place on orbit and must be done offline. The attitude requirements of a multi-agent inspection mission may necessitate an attitude controller capable of enforcing a desired attitude while avoiding certain constraint zones. An Artificial Potential Function (APF)-based attitude controller enables each inspector to point towards the desired target while avoiding a sun exclusion zone. The visualization all takes place in the relative, local-vertical, local-horizontal (LVLH) frame that is centered on the inspection target. The emergent, time-variant behavior of the APF is based on two factors. First, the sun exclusion zone moves in the relative frame as the earth moves in relation to the sun---an annual oscillating effect---and the spacecraft moves around the earth, rotating the LVLH frame---a daily oscillating effect. Second, the desired attitude for the controller is dictated based on the position of the inspector relative to the target. For an inspection, constant target pointing is typically desired and the translational movement of the inspector relative to the target dictates a constantly changing desired attitude. For this example, the inspector is placed in a natural motion circumnavigation (NMC) trajectory around the target. An important property of an NMC can be observed in the piece as any NMC around a reference orbit will have the same period as that reference orbit's inertial period. In this case, as the inertial period of the reference orbit determines both the inspector's NMC period and the rate of rotation of the LVLH frame, both time varying components move at roughly the same rate. The elevation change throughout the inspection is due to the relative inclination of the inspector's NMC.

The video shows the instantaneous high-speed flow velocity and mixture image of the free propane jet with a flow rate of 50 standard liter per minute (slpm) into ambient air. Velocity vectors estimated using deep-learning based optical flow analysis, CRoss-Attentional Flow Transformer (CRAFT) are superimposed on the image. 100 consecutive image pairs within each burst were obtained with a frame rate of 100 kHz. The mixture fraction is illustrated by the colorbar on the right. The velocity magnitude is shown as an arrow above the colorbar.

Intermittent combustion oscillations are observed in a fuel staged Multi Nozzle Lean Direct Injection combustor. The combustor array is categorized into three independent fuel stages, consisting of thirteen nozzles, namely, the pilot, the intermediate, and the outer. The flame reaction zones corresponding to these nozzles have been highlighted. During these intermittent oscillations the combustor was operated at an equivalence ratio of 0.6, fuel split to the pilot nozzles was 45%, intermediate had 30% and outer had 20% of the total fuel. The unstable periodic and aperiodic thermoacoustic oscillations formed two type-II intermittency states which depicted kite-like patterns, identified through nonlinear time series analysis. Spectral Proper Orthogonal Decomposition performed on the time resolved OH* Chemiluminescence images corresponding to these intermittent states are shown here demonstrating the propagation of the instability. The first type-II intermittent state is oscillating at 540 Hz and the second is oscillating at 560 Hz.

CFD simulation showing the complex boundary layer transition of f-BoLT 35. Disturbances, in the form of broadband noise, are introduced to a base flow field solution outside the and along the bow shock. Flow field slices along the the symmetry and outflow planes show density gradients, while the surface is contours of Stanton number. The nose curvature of f-BoLT creates a stream-wise vortex which sweeps toward the symmetry plane, resulting in two distinct boundary layer regions. As the disturbances reach these boundary layer regions, they stimulate transition to occur in a distinct and visually pleasing pattern. Distribution Statement A: Approved for Public Release; Distribution is Unlimited. PA# AFRL-2024-0796

A laser beam with typical Gaussian beam of when passes through random change in refractive index (RI) creates speckles at image plane. Stars in the night sky twinkle because of the random change in RI caused by atmospheric turbulence. This video shows the “twinkling” caused by an emulated atmospheric turbulence using phase plates at AFIT’s Quantum Optics Lab.