Computational modeling of plasma-assisted shock wave control using the Cartesian cut cell method
Date
2024
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Abstract
To control shock waves using plasma discharges, we have developed a numerical model focusing on improving the accuracy and efficiency of simulating supersonic channel flow. Shock waves are essential in high-speed air-breathing propulsion devices such as ramjets and scramjets. The lack of turbomachinery means that shock waves compress air prior to combustion. The shocks decelerate the high-speed flow, increasing static temperature and pressure, which is necessary for efficient combustion. However, the advantage of simplicity (no moving parts) to achieve compression is counteracted by increased wave drag, total pressure losses, and flow separation inside the engine. In this context, the generation of shock wave trains (a sequence of reflected oblique and normal shocks propagating through the engine) must be appropriately managed and optimized to reduce drag and enhance thrust. To tackle these challenges, we use the APDL-CFD code to model a Ma=2.5 supersonic flow over a 10-degree triangular wedge inside a straight channel. The wedge generates a shock wave train that is typically encountered inside the isolator of a scramjet engine. These conditions are indicative of conditions that are currently being tested in supersonic wind tunnels. The code solves the compressible Navier-Stokes equations, incorporating advective and diffusive fluxes. The advective fluxes account for mass, momentum, and energy transport, while the diffusive fluxes capture viscous stresses and thermal conduction. This formulation includes viscous dissipation and heat diffusion, ensuring accurate modeling of compressible flow behavior. Furthermore, we enhance the APDL-CFD code with the Cartesian cut cell method, which allows the representation of complex geometries on a Cartesian mesh. This research represents geometries found in wind tunnel models and internal vehicle designs. Using the cut cell method, the model can capture flow caused by geometries that do not conform to a Cartesian mesh, like the wedge that generates the oblique shock waves. This improves accuracy and significantly reduces computational costs, allowing for lower grid resolutions on a Cartesian mesh. The cut cell method is implemented to research the use of plasma actuators as an active control mechanism. The model investigates how varying key parameters, such as the location and temperature of the plasma, affect shock wave dynamics and the associated separation bubbles. Results show that the plasma kernel alters the flow and provides an effective way to shift the position and reduce the intensity of the shock waves inside the channel. The numerical simulations aim to optimize this control, showing that shocks can be dynamically managed with the proper plasma parameters to enhance flow stability and performance. The results demonstrate significant improvements in controlling shock waves and flow separation when plasma actuators are employed, showing potential for their use in high-speed propulsion systems such as scramjets. Moreover, incorporating the cut cell method has optimized the APDL-CFD code, making it more efficient and better suited for running rapid test simulations. The results can inform future experiments, such as those planned for the Colorado State University (CSU) wind tunnel. Overall, the research offers valuable insights into active flow control in supersonic and hypersonic vehicles for improving vehicle performance, efficiency, and reliability.
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Subject
cut cell method
plasma-assisted control
shock wave boundary layer interaction
hypersonic flow
computational fluid dynamics
separation bubble