DIRECT NUMERICAL SIMULATION OF ARTIFICIALLY INDUCED BOUNDARY LAYER TURBULENCE AND VORTEX PROPAGATION IN A ۲D CHANNEL

Fluid turbulence plays a critical role in many natural and engineering systems, yet directly solving the complete Navier–Stokes equations to capture all turbulent scales remains computationally expensive, especially for complex domains and high Reynolds numbers. This study investigates the artificial generation and downstream propagation of vortical structures in an incompressible two-dimensional channel flow using Direct Numerical Simulation (DNS) at a Reynolds number of ۲۰۰. The main purpose is to examine whether a controlled inlet disturbance can reproduce early-stage transitional flow features without requiring the long computational domain usually needed for natural boundary-layer transition. A time-dependent periodic perturbation is imposed at the channel inlet, while the governing equations are discretized using a fourth-order compact finite difference scheme in space and advanced in time by a third-order Runge–Kutta method. The computations are performed on an algebraically stretched ۲۴۰ × ۸۰ grid, with refined nodes near the lower boundary layer to improve the resolution of high-gradient regions. The results show the formation, shedding, and downstream convection of localized vortex structures along the channel wall. Velocity and pressure fields indicate that the inlet disturbance generates coherent unsteady motion and localized pressure variations associated with vortex cores. The findings suggest that the perturbation amplitude and fluid viscosity have stronger effects on the initiation and development of vortical structures than the excitation frequency alone. Overall, the study demonstrates the usefulness of artificial inlet excitations for investigating controlled transitional flow structures with manageable computational cost.

کلیدواژه ها:

Direct Numerical Simulation ، Artificially Induced Turbulence ، Boundary Layer ، Vortex Propagation ، ۲D Channel Flow