**Data-driven interpolation of dynamical systems with delay**

*Schulze, Philipp ; Unger, Benjamin* (2015)

We present a data-driven realization for systems with delay, which generalizes the Loewner framework. The realization is obtained with low computational cost directly from measured data of the transfer function. The internal delay is estimated by solving a least-square optimization over some sample data. Our approach is validated by several examples, which indicate the need for preserving the d...

**A Matlab toolbox for the regularization of descriptor systems arising from generalized realization procedures**

*Binder, Amelie ; Mehrmann, Volker ; Miedlar, Agnieszka ; Schulze, Philipp* (2015)

In this report we introduce a Matlab toolbox for the regularization of descriptor systems. We apply it, in particular, for systems resulting from the generalized realization procedure of [16], which generates, via rational interpolation techniques, a linear descriptor system from interpolation data. The resulting system needs to be regularized to make it feasible for the use in simulation, opti...

**The shifted proper orthogonal decomposition**

*Reiss, Julius ; Schulze, Philipp ; Sesterhenn, Jörn* (2015)

Transport-dominated phenomena provide a challenge for common mode-based model reduction approaches. We present a model reduction method, which extends the proper orthogonal decomposition (POD) by introducing time-dependent shifts of the snapshot matrix. The approach, called shifted proper orthogonal decomposition (sPOD), features a determination of the multiple transport velocities and a separa...

**Port-Hamiltonian realizations of linear time invariant systems**

*Beattie, Christopher ; Mehrmann, Volker ; Xu, Hongguo* (2015)

The question when a general linear time invariant control system is equivalent to a port-Hamiltonian systems is answered. Several equivalent characterizations are derived which extend the characterizations of [38] to the general non-minimal case. An explicit construction of the transformation matrices is presented. The methods are applied in the stability analysis of disc brake squeal.

**On the port-Hamiltonian structure of the Navier-Stokes equations for reactive flows**

*Altmann, Robert ; Schulze, Philipp* (2016)

We consider the problem of finding an energy-based formulation of the Navier-Stokes equations for reactive flows. These equations occur in various applications, e. g., in combustion engines or chemical reactors. After modeling, discretization, and model reduction, important system properties as the energy conservation are usually lost which may lead to unphysical simulation results. In this pa...

**Numerical solution of singularly perturbed convection-diffusion-reaction problems with two small parameters**

*Das, Pratibhamoy ; Mehrmann, Volker* (2015)

This paper discusses the numerical solution of 1-D convection-diffusion-reaction problems that are singularly perturbed with two small parameters using a new mesh-adaptive upwind scheme that adapts to the boundary layers. The meshes are generated by the equidistribution of a special positive monitor function. Uniform, parameter independent convergence is shown and holds even in the limit that ...

**Shockless explosion combustion**

*Bobusch, Bernhard C. ; Berndt, Phillip ; Paschereit, Christian Oliver ; Klein, Rupert* (2014-09-30)

Constant volume combustion (CVC) in gas turbines is a promising way to achieve a step change in the efficiency of such systems. The most widely investigated technique to implement CVC in gas turbine systems is pulsed detonation combustion (PDC). Unfortunately, the PDC is associated with several disadvantages, such as sharp pressure transitions, entropy generation due to shock waves, and exergy ...

**Investigation of Fluidic Devices for Mixing Enhancement for the Shockless Explosion Combustion Process**

*Bobusch, Bernhard ; Berndt, Phillip ; Paschereit, Christian Oliver ; Klein, Rupert* (2014-09)

Fuel-air mixing is a crucial process in low emission combustion systems. A higher mixing quality leads to lower emissions and higher combustion efficiencies. Especially for the innovative constant volume combustion processes "Shockless Explosion Combustion" (SEC) the mixing of fuel and air is an important parameter, since the whole combustion process is triggered and controlled via the equivale...

**Experimental investigation of a turbine sealing cavity exposed to free stream pressure fluctuation**

*Schliwka, Tobias ; Malzacher, Leonie ; Chemnitz, Silvio ; Peitsch, Dieter* (2014-09-10)

The current investigation examines the impact of a new pulsed unsteady combustion to the turbine sealing cavity, which prevents hot gas ingestion into the inner machine. Sealing flow is ensured by relatively cold secondary air blowing radially through the rotor-stator-wheel space. The interaction between the sealing flow and the main gas flow however causes aerodynamic losses. These losses as w...

**Active Flow Control by Adaptive Blade Systems in Periodic Unsteady Flow Conditions**

*Hammer, Steffen ; Phan, Dat Tien ; Peter, Julija ; Werder, Tobias ; Meyer, Robert ; Liebich, Robert ; Thamsen, Paul Uwe* (2014-09-10)

A test stand to investigate the rotor-stator interaction of a compressor stage is presented. This water channel allows to investigate the influence of wake depressions and choking to a stator cascade. Furthermore, adaptive blade systems are presented to affect the operating of stator under periodic unsteady flow conditions. The piezoelectric actuators are one of these adaptive blade systems. Th...

**Experimental Investigation of a 7 by 7 Nozzle Jet Array for Dynamic Impingement Cooling**

*Haucke, Frank ; Kroll, Henning ; Peltzer, Inken ; Nitsche, Wolfgang* (2014-09-10)

Dynamic impingement cooling is a promising way for more efficient exploitation of cooling air in highly heat charged environments. In many applications the deployed impinging jets are subjected to crossflow superimposed on the flow field of the transverse jets. The present study describes the initial experimental investigations regarding dynamic heat transfer between a flat surface and an array...

**Review: Active Control of Shock-associated Unsteady Flow Phenomena in Aeroengines - Suppression Techniques for Transonic Cascade Flutter and Supersonic Jet Noise -**

*Watanabe, Toshinori* (2014-09-10)

Active control techniques for cascade flutter suppression and supersonic jet noise reduction were studied in the University of Tokyo. For flutter suppression, piezoelectric devices were installed on the blade surfaces. The active oscillation of the trailing edge of a blade was found to suppress the flutter instability in the numerical analysis. The effect was qualitatively confirmed in a trial ...

**Internal Flow Physics of a Fluidic Oscillator in the Transition Regime**

*Gregory, James W. ; Tomac, Mehmet N.* (2014-09)

An experimental investigation of the underlying flow physics of a dual jet interaction fluidic oscillator has been conducted in the transition regime for a Reynolds number of 1680. The transition regime is defined as a narrow range of flow rates between two other operating modes of the fluidic oscillator. Particle image velocimetry (PIV) was used with refractive index matching sodium iodide sol...