Efficient CFD-based PID Control of Free Shear Layer Flow

摘要

A rigorous approach to controlling low speed free shear (mixing) layer flows is proposed. The flow control is achieved in the temporal domain by using proportional-integral-derivative (PID) control. It is proposed here that the initial conditions in the temporal problem can be mapped to the inflow boundary conditions for direct numerical simulation (DNS) of the spatially growing free shear layers. Simulations carried out in the spatial domain support this proposal. The approach constitutes in perturbing the spatially growing mixing layer by an appropriate perturbation (mapped from the temporal problem) close to the origin of the mixing layer and then letting the mixing layer evolve downstream. Depending on the imposed perturbations, the mixing layer growth can be enhanced or suppressed, as desired. The perturbations can be imposed via temperature or velocity or both. A rapidly converging simple linear control has been demonstrated in this study to control the mixing layer in a feedback loop, based on a given set point. Detailed DNS results of the spatially growing free shear layers presented demonstrate that the growth of the mixing layer in the two domains is quite similar, and the mixing layer dynamics is achieved that reflects what is observed in various experimental studies. Therefore, it is sufficient to control the mixing layer in the temporal domain, which is achieved very rapidly and forms the basis for a potential real-time control of such flows.