Iterative design for active control of fluid flow

This paper considers iterative controller design for planar Poiseuille flow by model unfalsification and controller redesign. The main contribution is to show that model-unfalsification-based iterative design can be useful in flow control problems. The a priori knowledge of the dynamics of the sampled system is obtained from the analytic approximation of the Navier-Stokes equations by a Galerkin method. Pole-positions, expected model orders and feasible dynamic variations are valuable prior knowledge which can be taken into account in the uncertainty-model unfalsification-based iterative design scheme developed

Model Penilaian Kinerja Instruktur SMK Mikael Surakarta: Dalam Upaya Mempersiapkan Lulusan Siap Kerja

Performance appraisal is a formal and structured system of measuring and assessing employees\u27 work performance using performance standards defined by organization. The focus of performance appraisal is to determine the employee productivity, whose results can later be used to motivation the employees to work better. If poor performance appraisal is found, the organization should follow up by providing training so that the employees are able to improve the performance as expected by the organization. Performance appraisals should have validity, agreement, realism, and objectivity, so that the result can be beneficial to the employee being assessed, the assessment team and the company

Addressing the Safety and Trauma Issues of Abused Women: A Cross-Canada Study of YWCA Shelters

Shelters for women are often seen as the major resource for intimate partner violence, yet few evaluations have been published. This study describes the needs, trauma symptoms and safety issues of 368 women as they enter and leave emergency shelters in ten Canadian violence against women emergency shelters; nine operated by the YWCA and a private shelter in Nova Scotia. The results capture the nature of the abuse, what the women wanted from shelter residence, the services they received, and their plans for afterwards. On shelter entry, on the Danger Assessment over 75% of women residents fell in the range of Extreme or Severe Danger. Although still in the clinical range, total and subscales on the Impact of Event Scale-Revised significantly reduced from shelter entry to exit. The women strongly endorsed the shelter in assisting them with safety, support and access to essential basic needs

Sum-of-squares of polynomials approach to nonlinear stability of fluid flows: an example of application

With the goal of providing the first example of application of a recently proposed method, thus demonstrating its ability to give results in principle, global stability of a version of the rotating Couette flow is examined. The flow depends on the Reynolds number and a parameter characterising the magnitude of the Coriolis force. By converting the original Navier-Stokes equations to a finite-dimensional uncertain dynamical system using a partial Galerkin expansion, high-degree polynomial Lyapunov functionals were found by sum-of-squares-of-polynomials optimization. It is demonstrated that the proposed method allows obtaining the exact global stability limit for this flow in a range of values of the parameter characterising the Coriolis force. Outside this range a lower bound for the global stability limit was obtained, which is still better than the energy stability limit. In the course of the study several results meaningful in the context of the method used were also obtained. Overall, the results obtained demonstrate the applicability of the recently proposed approach to global stability of the fluid flows. To the best of our knowledge, it is the first case in which global stability of a fluid flow has been proved by a generic method for the value of a Reynolds number greater than that which could be achieved with the energy stability approach

Sum-of-Squares approach to feedback control of laminar wake flows

A novel nonlinear feedback control design methodology for incompressible fluid flows aiming at the optimisation of long-time averages of flow quantities is presented. It applies to reduced-order finite-dimensional models of fluid flows, expressed as a set of first-order nonlinear ordinary differential equations with the right-hand side being a polynomial function in the state variables and in the controls. The key idea, first discussed in Chernyshenko et al. 2014, Philos. T. Roy. Soc. 372(2020), is that the difficulties of treating and optimising long-time averages of a cost are relaxed by using the upper/lower bounds of such averages as the objective function. In this setting, control design reduces to finding a feedback controller that optimises the bound, subject to a polynomial inequality constraint involving the cost function, the nonlinear system, the controller itself and a tunable polynomial function. A numerically tractable approach to the solution of such optimisation problems, based on Sum-of-Squares techniques and semidefinite programming, is proposed. To showcase the methodology, the mitigation of the fluctuation kinetic energy in the unsteady wake behind a circular cylinder in the laminar regime at Re=100, via controlled angular motions of the surface, is numerically investigated. A compact reduced-order model that resolves the long-term behaviour of the fluid flow and the effects of actuation, is derived using Proper Orthogonal Decomposition and Galerkin projection. In a full-information setting, feedback controllers are then designed to reduce the long-time average of the kinetic energy associated with the limit cycle. These controllers are then implemented in direct numerical simulations of the actuated flow. Control performance, energy efficiency, and physical control mechanisms identified are analysed. Key elements, implications and future work are discussed