Development of Empirical Estimators for Feedback Control of High-Speed Axisymmetric Jets

of the unforced jet has been developed. An existing direct numerical simulation database, with a configuration similar to previous experiments, formed the testbed for this modeling phase. Real-time flow state estimation is a challenging problem in the implementation of feedback control for such complex flows of practical interest. Sensing the pressure in the irrotational near field close to the nozzle exit offers a suitable nonintrusive measurement that is drivenbythejet’sshearlayerdynamics.Owingtoconvection,suchaconfigurationnaturallyresultsinthemeasured pressure having a time lead compared with the state of the reduced-order model, which is very useful for feedback control. The sensing configuration used consists of an azimuthal ring array along with a linear array. Several estimation strategies are implemented and assessed using the numerical database. The time-invariant version of the linear Kalman filter is shown to have similar or better accuracy compared with a quadratic stochastic estimator, whichinturnsignificantlyoutperformsalinearstochasticestimator.The filterisonlyascomputationallycomplexas the linear stochastic estimator, thereby making it the strategy of choice.