324 citations · 989 across the 29 of their papers we have counts for
29 papers
Trapping Regions for Quadratic Systems with Generalized Lossless Nonlinearities
Diganta Bhattacharjee, Shih-Chi Liao, Peter J. Seiler +1
We consider a class of quadratic systems, primarily motivated by incompressible fluid flows, where the nonlinearities are generalized lossless: they do not produce or dissipate ene…
On Boundedness of Quadratic Dynamics with Energy-Preserving Nonlinearity
Shih-Chi Liao, Maziar S. Hemati, Peter Seiler
Boundedness is an important property of many physical systems. This includes incompressible fluid flows, which are often modeled by quadratic dynamics with an energy-preserving non…
Data-driven nonlinear aerodynamics models with certifiably optimal boundedness properties
A. Leonid Heide, Shih-Chi Liao, Sergio Castiblanco-Ballesteros +3
Obtaining predictive low-order models is a central challenge in fluid dynamics. Data-driven frameworks have been widely used to obtain low-order models of aerodynamic systems; yet,…
Local Stability and Stabilization of Quadratic-Bilinear Systems using Petersen's Lemma
Amir Enayati Kafshgarkolaei, Maziar S. Hemati
Quadratic-bilinear (QB) systems arise in many areas of science and engineering. In this paper, we present a scalable approach for designing locally stabilizing state-feedback contr…
Identifying spatially-localized instability mechanisms using sparse optimization
Talha Mushtaq, Maziar S. Hemati
Recent investigations have established the physical relevance of spatially-localized instability mechanisms in fluid dynamics and their potential for technological innovations in f…
Structured Input-Output Modeling and Robust Stability Analysis of Compressible Flows
Diganta Bhattacharjee, Talha Mushtaq, Peter Seiler +1
The recently introduced structured input-output analysis is a powerful method for capturing nonlinear phenomena associated with incompressible flows, and this paper extends that me…
A Convex Optimization Approach to Compute Trapping Regions for Lossless Quadratic Systems
Shih-Chi Liao, A. Leonid Heide, Maziar S. Hemati +1
Quadratic systems with lossless quadratic terms arise in many applications, including models of atmosphere and incompressible fluid flows. Such systems have a trapping region if al…
An optimization framework for analyzing nonlinear stability due to sparse finite-amplitude perturbations
A. Leonid Heide, Maziar S. Hemati
Recent works have established the utility of sparsity-promoting norms for extracting spatially-localized instability mechanisms in fluid flows, with possible implications for flow…
On the convexity of static output feedback control synthesis for systems with lossless nonlinearities
Talha Mushtaq, Peter Seiler, Maziar S. Hemati
Computing a stabilizing static output-feedback (SOF) controller is an NP-hard problem, in general. Yet, these controllers have amassed popularity in recent years because of their p…
Exact Solution for the Rank-One Structured Singular Value with Repeated Complex Full-Block Uncertainty
Talha Mushtaq, Peter Seiler, Maziar S. Hemati
In this note, we present an exact solution for the structured singular value (SSV) of rank-one complex matrices with repeated complex full-block uncertainty. A key step in the proo…
Robust Local Stabilization of Nonlinear Systems with Controller-Dependent Norm Bounds: A Convex Approach with Input-Output Sampling
Sze Kwan Cheah, Diganta Bhattacharjee, Maziar S. Hemati +1
This letter presents a framework for synthesizing a robust full-state feedback controller for systems with unknown nonlinearities. Our approach characterizes input-output behavior…
Structured Singular Value of a Repeated Complex Full-Block Uncertainty
Talha Mushtaq, Diganta Bhattacharjee, Peter Seiler +1
The structured singular value (SSV), or mu, is used to assess the robust stability and performance of an uncertain linear time-invariant system. Existing algorithms compute upper a…
Quadratic Constraints for Local Stability Analysis of Quadratic Systems
Shih-Chi Liao, Maziar S. Hemati, Peter Seiler
This paper proposes new quadratic constraints (QCs) to bound a quadratic polynomial. Such QCs can be used in dissipation ineqaulities to analyze the stability and performance of no…
Estimating Regions of Attraction for Transitional Flows using Quadratic Constraints
Aniketh Kalur, Talha Mushtaq, Peter Seiler +1
This letter describes a method for estimating regions of attraction and bounds on permissible perturbation amplitudes in nonlinear fluids systems. The proposed approach exploits qu…
Model-based multi-sensor fusion for reconstructing wall-bounded turbulence
Mengying Wang, C. Vamsi Krishna, Mitul Luhar +1
Wall-bounded turbulent flows can be challenging to measure within experiments due to the breadth of spatial and temporal scales inherent in such flows. Instrumentation capable of o…
Reducing transient energy growth in a channel flow using static output feedback control
Huaijin Yao, Yiyang Sun, Talha Mushtaq +1
Transient energy growth of flow perturbations is an important mechanism for laminar-to-turbulent transition that can be mitigated with feedback control. Linear quadratic optimal co…
Feedback control of transitional shear flows: Sensor selection for performance recovery
Huaijin Yao, Yiyang Sun, Maziar S. Hemati
The choice and placement of sensors and actuators is an essential factor determining the performance that can be realized using feedback control. This determination is especially i…
Reconstructing the time evolution of wall-bounded turbulent flows from non-time resolved PIV measurements
C. Vamsi Krishna, Mengying Wang, Maziar S. Hemati +1
Particle Image Velocimetry (PIV) systems are often limited in their ability to fully resolve the spatiotemporal fluctuations inherent in turbulent flows due to hardware constraints…
Nonlinear Stability Analysis of Transitional Flows using Quadratic Constraints
Aniketh Kalur, Peter Seiler, Maziar S. Hemati
The dynamics of transitional flows are governed by an interplay between the non-normal linear dynamics and quadratic nonlinearity in the incompressible Navier-Stokes equations. In…
A Hybrid Model for Lift Response to Dynamic Actuation On A Stalled Airfoil
Xuanhong An, David R. Williams, Maziar S. Hemati
The current research focuses on modeling the lift response due to dynamic (time-varying) 'burst-type' actuation on a stalled airfoil. Dynamic `burst-type' actuation exhibits two di…
Data-Driven Selection of Actuators for Optimal Control of Airfoil Separation
Debraj Bhattacharjee, Bjoern Klose, Gustaaf B. Jacobs +1
We present a systematic approach for determining the optimal actuator location for separation control from input-output response data, gathered from numerical simulations or physic…
Feedback control for transition suppression in direct numerical simulations of channel flow
Yiyang Sun, Maziar S. Hemati
For channel flow at subcritical Reynolds numbers (), a laminar-to-turbulent transition can emerge due to a large transient amplification in the kinetic energy of small per…
Control-oriented model reduction for minimizing transient energy growth in shear flows
Aniketh Kalur, Maziar S. Hemati
A linear non-modal mechanism for transient amplification of perturbation energy is known to trigger sub-critical transition to turbulence in many shear flows. Feedback control stra…
Modal Analysis of Fluid Flows: Applications and Outlook
Kunihiko Taira, Maziar S. Hemati, Steven L. Brunton +5
We present applications of modal analysis techniques to study, model, and control canonical aerodynamic flows. To illustrate how modal analysis techniques can provide physical insi…