Inst. Strömungsmechanik und Technische Akustik (ISTA)

136 Items

Recent Submissions
An acoustic time-of-flight technique for unsteady temperature measurements in combustion chambers

Waßmer, Dominik (2018)

In consideration of the manifold alternative electric energy sources, load flexibility in modern gas turbines is an essential requirement. To this end, the operational range of the engines must be extended. However, this is often impeded by low-frequency combustion instabilities that are associated with acoustics generated within the gas turbine combustor. These high-amplitude pressure oscillat...

Untersuchung einer neuen Herzklappe für Herzunterstützungssysteme

Lambertz, M. ; Affeld, K. ; Ziemann, A. (1998)

Ein bewährtes Verfahren zur Behandlung erkrankter natürlicher Heizklappen ist die Implantation von Heizklappenprothesen. Neben diesem Einsatz entwickelt sich zur Zeit ein weiteres Anwendungsgebiet; der Einsatz von Herzklappenprothesen in Herzunterstützungssystemen. Eine häufig dabei auftretende Komplikation stellt die Thrombenbildung dar. Diese tritt insbesondere im Bereich der verwendeten Herz...

On the Potential of Power Generation from Thermoelectric Generators in Gas Turbine Combustors

Stathopoulos, Panagiotis ; Fernàndez-Villa, Javier (2018-10-16)

Thermoelectric generators (TEGs) offer an attractive power generation option. They have no moving parts, are robust and emit no pollutants. The current work explores the integration of high temperature TEGs in gas turbine combustors. The latter have a thermal shield at their inner surface to protect them against high temperatures. This is supplemented by convective and film cooling. This work s...

Modification of a high pressure test rig for thermoacoustic measurements

Niether, Sebastian (2018)

Current stationary gas turbines for power generation rely on lean premixed combustion, in order to achieve low emissions of detrimental exhaust gases, such as NOx. However, employment of this combustion process can lead to the occurrence of thermoacoustic instabilities. Characterized by strong pressure fluctuations inside the combustion chamber, this phenomenon has negative effects on exhaust g...

The influence of impeller designs on the performance of a vortex pump

Gerlach, Angela (2018)

Vortex pumps are particularly suitable for the transportation of solids-containing fluids. Hence, vortex pumps are applied to a wide range of operation domains, from wastewater transport to food processing. Characteristics of vortex pumps are their recessed, semi-open impeller and their enlarged gap between the impeller and the casing. These features strongly reduce the risk of clogging compare...

A Finite-Time Thermodynamics of Unsteady Fluid Flows

Noack, Bernd R. ; Schlegel, Michael ; Ahlborn, Boye ; Mutschke, Gerd ; Morzyński, Marek ; Comte, Pierre ; Tadmor, Gilead (2008)

Turbulent fluid has often been conceptualized as a transient thermodynamic phase. Here, a finite-time thermodynamics (FTT) formalism is proposed to compute mean flow and fluctuation levels of unsteady incompressible flows. The proposed formalism builds upon the Galerkin model framework, which simplifies a continuum 3D fluid motion into a finite-dimensional phase-space dynamics and, subsequently...

Experimental Three-Dimensional Velocity Data of a Sweeping Jet from a Fluidic Oscillator

Ostermann, Florian ; Woszidlo, Rene ; Nayeri, Christian Navid ; Paschereit, Christian Oliver (2018-09-28)

The dataset contains three-dimensional, quasi time-resolved velocity field of a sweeping jet from a fluidic oscillator. The data is acquired experimentally at the Technische Universität Berlin by employing a traversable stereoscopic particle image velocimetry system. The presented data served as the basis for several publications. Detailed information on the scientific background, the associate...

Experimental Three-Dimensional Velocity Data of a Sweeping Jet from a Fluidic Oscillator Interacting with a Crossflow

Ostermann, Florian ; Woszidlo, Rene ; Nayeri, Christian Navid ; Paschreit, Christian Oliver (2018-09-28)

The dataset contains three-dimensional, quasi time-resolved velocity fields of the complex flow field that is caused by a sweeping jet from a fluidic oscillator interacting with an attached turbulent crossflow. The data is acquired experimentally at the Technische Universität Berlin by employing a traversable stereoscopic particle image velocimetry system. The presented data served as the basis...

Drag reduction of a bluff body model in water and air

Schmidt, Hanns-Joachim (2018)

The presented work describes and discusses the results of wind tunnel and towing tank experiments carried out on a rectangular bluff body model equipped with base flaps as passive and fluidic oscillators as active means for drag reduction. The geometry of the model is based on the Generic European Transport System (GETS) which is similar to a 10 % scaled truck trailer combination without any ge...

Simulation-based determination of systematic errors of flow meters due to uncertain inflow conditions

Weissenbrunner, Andreas ; Fiebach, André ; Schmelter, Sonja ; Bär, Markus ; Thamsen, Paul Uwe ; Lederer, Thomas (2016-12)

Computational fluid dynamics (CFD) provides well-established tools for the prediction of the velocity profiles in turbulent pipe flows. As far as industrial pipe and district heating systems are concerned, combinations of elbows are the most common pipe assemblies. Among the different pipe combinations, double elbows out-of-plane are of special interest, since they introduce strong disturbances...

Uncertainty evaluation for velocity–area methods

Steinbock, Jonas ; Weissenbrunner, Andreas ; Juling, Markus ; Lederer, Thomas ; Thamsen, Paul Uwe (2016-02)

Velocity–area methods are used for flow rate calculation in various industries. Applied within a fully turbulent flow regime, modest uncertainties can be expected. If the flow profile cannot be described as “log-like”, the recommended measurement positions and integration techniques exhibit larger errors. To reduce these errors, an adapted measurement scheme is proposed. The velocity field insi...

Fundamental properties of a spatially oscillating jet emitted by a fluidic oscillator

Ostermann, Florian (2018)

A jet is a fundamental flow scenario underlying several technical applications. Recently, spatially oscillating jets emitted by fluidic oscillators are employed to enhance mixing or control separation. Fluidic oscillators are able to emit a jet that spatially oscillates within a plane. Although their efficacy has been proven for many applications, the reasons for their performance remain unknow...

The dynamics of volcanic jets

Cigala, V. ; Kueppers, U. ; Peña Fernández, J. J. ; Taddeucci, J. ; Sesterhenn, J. ; Dingwell, D. B. (2017-07-24)

Pyroclast ejection during explosive volcanic eruptions occurs under highly dynamic conditions involving great variations in flux, particle sizes, and velocities. This variability must be a direct consequence of complex interactions between physical and chemical parameters inside the volcanic plumbing system. The boundary conditions of such phenomena cannot be fully characterized via field obser...

Contact electrification in aerosolized monodispersed silica microspheres quantified using laser based velocimetry

Alois, Stefano ; Iversen, Jens Jacob ; Merrison, Jonathan ; Sesterhenn, Jörn (2017-04)

The contact electrification of aerosolized micro particles has been studied using a novel technique involving laser velocimetry. This has allowed the simultaneous determination of size and electrical charge of individual silica microspheres (in the range 1 – 8 µm). Interestingly the particles interacting with the injector tube have been seen to become electrified with a relatively narrow range ...

Investigation of the Global Mode in Swirling Combustor Flows: Experimental Observations and Local and Global Stability Analysis

Terhaar, Steffen ; Paredes, P. ; Oberleithner, Kilian ; Theofilis, V. ; Paschereit, Christian Oliver (2015)

Self-excited helical flow oscillations are frequently observed in gas turbine combustors. In the present work a new approach is presented tackling this phenomenon with stability concepts. Three reacting swirling flows are investigated. All of them undergo vortex breakdown, but only two of them show self-excited global flow oscillations at well-defined frequencies. The oscillations feature a pre...

Stability Analysis of Time-averaged Jet Flows: Fundamentals and Application

Oberleithner, Kilian ; Paschereit, Christian Oliver ; Soria, Julio (2015)

We report on experimental and theoretical investigations of shear flow instabilities in jet flows. Linear stability analysis is applied to the time-averaged flow taken from experiments, contrasting the ‘classic’ stability approach that is based on a stationary base flow. To some extend, mean flow stability eigenmodes may deal as a model for instability waves at their nonlinearly saturated state...

The compressible starting jet

Peña Fernández, Juan José (2018)

Jets are involved in numerous industrial applications and in nature: fuel injection, jet engines, volcanic jets, air-bag devices, but also water jet cutters, jet packs (rocket belts), jet injectors for vaccination, astrophysical jets, etc. Continuous jets have been already studied in the incompressible and compressible case for almost a century, focused mainly on the characterization of the flu...

Simulation und Analyse einer Verdichterkaskade mit aktiver Strömungsbeeinflussung

Gmelin, Christoph (2018)

Axiale Verdichter erreichen heutzutage sehr hohe Gesamtdruckverhältnisse, wozu eine hohe Anzahl von Verdichterstufen notwendig ist. Bei Flugtriebwerken stellt das Einsparen ganzer Stufen eine Möglichkeit dar, gleichzeitig das Gewicht und den Bauraum zu reduzieren. Für stationäre Gasturbinen wird der Teillastbetrieb mit steigendem Anteil an regenerativen Energien immer bedeutsamer. Beide Forderu...

Rotierende Instabilität in Axialverdichtern

Pardowitz, Benjamin (2018)

Die vorliegende Arbeit befasst sich mit der Identifikation und experimentellen Analyse von einem physikalischen Effekt der in Verbindung mit instationären Vorgängen in Turbomaschinen und vorwiegend an Axialverdichtern auftritt. Dieser Effekt wird als Rotierende Instabilität (RI) bezeichnet und im Rahmen dieser Arbeit sowohl an einer einzelnen Statorbeschaufelung, als auch an einer axialen Rotor...

Kreiselpumpe mit horizontalem Leistungsverlauf über dem Volumenstrom

Beck, Marcus Klaus (2018-03)

In der Doktorarbeit wurde der neuartige Ansatz verfolgt, eine Kreiselpumpe kleiner Baugröße mit einer Hydraulik zu entwickeln, welche bei Veränderung des Volumenstromes die Leistungsaufnahme der Pumpe konstant hält, so dass sich ein horizontaler Verlauf der elektrischen Leistungskennlinie über den gesamten Volumenstrombereich ergibt. Eine flache Leistungskurve ist für kleine Maschinen interessa...