The flow over a set of tandem cylinders at a moderate Reynolds numbers (Re), and with different separation lengths has been studied. Two dimensional (2D) and three-dimensional (3D) plasma actuators were used to control the flow over the leading cylinder to change the vortex shedding, and subsequently the flow on the second cylinder. The 3D plasma actuator was segmented along the length of the cylinder with a spacing of λ = 4 while the 2D actuator simply ran straight down the span of the cylinder. Particle image velocimetry (PIV) measurements were used to investigate the flow along the central plane in the wake of the cylinders. The image pairs were processed into velocity grids which were then averaged. Plots of the shear, vorticity, and turbulent kinetic energy were created. These plots are used to understand how the character of vortex shedding from the upstream cylinder changes the same from the downstream one.

The utilization of steady state flow of air over tandem circular cylinders has several applications in engineering systems. Incompressible flow over circular cylinders in tandem at different spacing with and without plasma actuation on the leading cylinder will be investigated in this paper to understand the effects of plasma actuation on flow properties and wake region of the two cylinders in cross flow. The principal focus of the research is on the use of experimental and computational methods to study and provide valid results, the research will analyze the wake region, the effect of Reynolds number and the longitudinal spacing between cylinder on vortex shedding, aerodynamic parameters i.e. lift, drag, pressure differential, etc. The research will be conducted for steady flow at Reynold number, Re = U∞ L/v between 5000 and 8000 for air. The turbulence of the wake and dynamic instability of the experimental is characterized by the Strouhal number, St = fL/U∞ frequency of the vortex shedding in the wake which is directly proportional to the spacing, λ from center to center of cylinders between 3 to 5 inches. The dependencies on critical values of Re and St in symmetric flow over cylinders to show the instability of the flow regime in previous research. At Re = 5000 the vortex co-shedding on the second cylinder would occur at critical spacing, λccharacterized by the Re - St relationship at 3 ≤ λ ≤ 5 in the flow regime. The use of plasma actuation in fluid dynamics to control flow velocity by generating momentum to force atmospheric pressure and velocity in external flow with Single- Dielectric Barrier Discharge(SDBD) for both two and three-dimensional, 2D and 3D actuator (straight and segmented actuator). The SDBD actuators are mounted spanwise on the leading cylinder for both 2D and 3D to impact momentum, therefore, forcing the wake regime. Computational Analysis is utilized for result and data pre-processing. The steady three-dimensional flow of tandem cylinders can be studied through Large Eddy Simulation (LES) using a subgrid-scale model to compare numerical and experimental results for the same setup and physical conditions. Particle Image Velocimetry (PIV) is used to resolve time series images from flow visualization of the experiment, the images are processed to visualize velocity vectors of the flow regimes. The velocity profile of the flow can be averaged and plotted for all instantaneous time-series images processed in PIV by Dynamic Mode Decomposition (DMD) or Proper Orthogonal Decomposition (POD) to generate common eigenvalues and eigenvector of the large dimension PIV data which shows the average properties of the flow properties.