Short student presentations
Pennsylvania State University
Student presentations
Aravinth Sadagopan
Department of Aerospace Engineering
Modal analysis of a shear layer in high-supersonic cavity flows using data-driven and operator-based resolvent analysis
Shear layer oscillations (SLO) are common phenomena in aerospace applications inducing unfavorable acoustic radiation and structural fatigue. SLO driving mechanism over open cavity flows at subsonic and supersonic speeds have been well studied. However, for SLO over a cavity in high supersonic flows, the stability properties are relatively unexplored, i.e., for flow regimes beyond Mach 3. The classical Rossiter model fails to predict the SLO characteristics. Therefore, in this work resolvent analysis has been employed to identify the dominant dynamic mechanisms and modal characteristics of self-sustained SLO at high Mach numbers. In particular, the resolvent analyses are performed with both the data-driven and operator-based frameworks. The comparisons between both implementations will be highlighted for the resolvent modes and spectra. We will also discuss the influence of the baseflows due to the differences in the solver fidelity. With a series of implicit large-eddy simulations at Mach numbers 2 to 5, we observe a weak coupling between standing waves within the cavity and SLO. The strong compression/expansion waves on the shear layer and cavity wall reflected Mach waves significantly contribute to the SLO characteristics.
Arshia Merdasi
Department of Mechanical Engineering
The role of droplet modeling in a five-field model of ice accretion
The impingement and ice accretion of droplets on wing surfaces presents a serious challenge to aircraft safety and efficiency. We have developed an Eulerian multiphase model of icing. Five fields are transported including compressible air, water-vapor, droplets, film and ice. An immersed boundary method is employed to accommodate ice accretion. In this talk we will focus on droplet dynamics and heat and mass transfer modeling. Specifically, we have incorporated models for film deposition due to impaction and turbulent diffusion mechanisms, splashing, bouncing and re-entrainment, droplet heat transfer and attendant mass transfer evaporation, condensation, and freezing. We present predictions of collection efficiency on different airfoils to validate the numerous interfacial mass and dynamics models involved in the deposition process. It is found that for airfoil ice-shape modeling at relevant atmospheric conditions, it is critical to incorporate accurate modeling of the impaction, diffusion and splash/bounce elements of deposition processes, whereas re-entrainment is not as dynamically important. Also, the roles of droplet initial conditions (liquid, partially frozen, ice) and size distributions are explored in the context of their impact on ice shape.
Eric Anderson
Department of Mechanical Engineering
Simulating the flow of human crowds
The simulation of high-density crowds is used to design a safer building layout to reduce the risks of suffocation in crowds. Due to the intelligence of people, crowds are typically thinking fluids, decreasing the possibility to simulate accurately what individuals may do within the crowd. If the density of the crowd is very high and the goal of the majority is similar, then it is feasible to treat a high-density crowd as a Newtonian fluid. This simulation can then locate the high-pressure zones and the layout can be adjusted to reduce the pressure difference to reduce the risk of death by suffocation or the displeasure of individuals during travel. The effects of Stokes flow are also seen in some of the simulations.
