Bernhard Semlitsch
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View article: On the Generation of Large-Scale Vortical Flow Structures in Pipe Multifurcations
On the Generation of Large-Scale Vortical Flow Structures in Pipe Multifurcations Open
In many hydraulic power plants, the water supplied through the penstock needs to be distributed to multiple turbines. The application of pipe multifurcations is motivated by economic and efficiency reasoning. However, flow instabilities an…
View article: Predicting bifurcation and amplitude death characteristics of thermoacoustic instabilities from PINNs-derived van der Pol oscillators
Predicting bifurcation and amplitude death characteristics of thermoacoustic instabilities from PINNs-derived van der Pol oscillators Open
Self-sustained thermoacoustic oscillations as observed in low-emission combustion- involved gas turbines and aero-engines involve complicated thermal fluid–acoustics interaction and rich nonlinear dynamics. Such pulsating oscillations are …
View article: Electrical power, energy efficiency, NO and CO emissions investigations of an ammonia/methane-fueled micro-thermal photovoltaic system with a reduced chemical reaction mechanism
Electrical power, energy efficiency, NO and CO emissions investigations of an ammonia/methane-fueled micro-thermal photovoltaic system with a reduced chemical reaction mechanism Open
Ammonia is an alternative renewable green fuel with significant potential for addressing climate change concerns. Blending ammonia with methane has emerged as a viable strategy to improve the laminar burning velocity of ammonia. In this st…
View article: On the Water Jet Quality at Part-Load Operation of Pelton turbines
On the Water Jet Quality at Part-Load Operation of Pelton turbines Open
Pelton turbines with multiple nozzles are characterised by their excellent performance over a wide operating range of mass flow rates. Thus, Pelton turbine manifolds must also be designed to deliver good flow quality to the nozzles at part…
View article: Effect of inflow disturbances in Pelton turbine distributor lines on the water jet quality
Effect of inflow disturbances in Pelton turbine distributor lines on the water jet quality Open
The proper design of the manifold, distributing the flow to the individual nozzles, is crucial for the Pelton turbine performance. The generation of both energy losses and secondary flows must be reduced to a minimum to provide optimal wat…
View article: SHAPE Project: CFD calculations for side-by-side (SBS) propulsion
SHAPE Project: CFD calculations for side-by-side (SBS) propulsion Open
Water depths become forbiddingly shallow to allow ship traffic in connection rivers. Propellers can damage by interacting with the riverbed under low water conditions because they are designed with the largest possible diameter for efficie…
View article: Numerical Investigation of Pelton Turbine Distributor Systems with Axial Inflow
Numerical Investigation of Pelton Turbine Distributor Systems with Axial Inflow Open
In an agile power grid environment, hydroelectric power plants must operate flexibly to follow the demand. Their wide operating range and high part-load efficiencies allow for multi-injector Pelton turbines to fulfil these demands as long …
View article: Boundary conditions to represent the wave impedance characteristics of axial compressors
Boundary conditions to represent the wave impedance characteristics of axial compressors Open
Thermo-acoustic oscillations can damage gas turbines. Numerical predictions guide the combustor design to prevent the occurrence of this hazardous resonance phenomenon. Uncertainties, such as incomplete knowledge of boundary conditions, ch…
View article: On the numerical assessment of flow losses and secondary flows in Pelton turbine manifolds
On the numerical assessment of flow losses and secondary flows in Pelton turbine manifolds Open
Different methods combining analytical guidelines, numerical simulations, and the manufacturer’s experience are employed to design and optimise the distributor manifold of a Pelton turbine. All these methods have in common to assume undist…
View article: Shape Optimisation of Turbomachinery Components
Shape Optimisation of Turbomachinery Components Open
Low-order models are the first choice to find the initial design of turbomachinery components screening many configurations. The final optimisation of the three-dimensional geometry is crucial for the best performance. Because of the abili…
View article: Evaluation of Injection Strategies in Supersonic Nozzle Flow
Evaluation of Injection Strategies in Supersonic Nozzle Flow Open
The ability to manipulate shock patterns in a supersonic nozzle flow with fluidic injection is investigated numerically using Large Eddy Simulations. Various injector configurations in the proximity of the nozzle throat are screened for nu…
View article: The generation mechanism of higher screech tone harmonics in supersonic jets
The generation mechanism of higher screech tone harmonics in supersonic jets Open
The generation mechanism of screech harmonics in supersonic exhausts is revealed using shadowgraph imaging and acoustic far-field measurements for a rectangular, high aspect-ratio nozzle. The coherent information associated with screech an…
View article: Flow Structure Generation by Multiple Jets in Supersonic Cross-Flow
Flow Structure Generation by Multiple Jets in Supersonic Cross-Flow Open
The flow structure generation by multiple jets impinging a supersonic crossflow in the divergent section of a Convergent-Divergent (C-D) duct is investigated using compressible Large Eddy Simulations (LES). The supersonic flow-field in the…
View article: Entropy and Vorticity Wave Generation in Realistic Gas Turbine Combustors
Entropy and Vorticity Wave Generation in Realistic Gas Turbine Combustors Open
Understanding the nature of the unsteady flow at the combustor exit is required to accurately simulate time-dependent phenomena in the turbine entry, such as indirect noise generation. Using large-eddy simulations of the combustion process…
View article: Transforming the Shock Pattern of Supersonic Jets Using Fluidic Injection
Transforming the Shock Pattern of Supersonic Jets Using Fluidic Injection Open
Double shock diamonds establish in the exhaust of modular convergent–divergent nozzles. These consist of two shock structures: one originating from the nozzle throat, and another from its exit. Analyzing the shock pattern developing for di…
View article: Fluidic Injection Scenarios for Shock Pattern Manipulation in Exhausts
Fluidic Injection Scenarios for Shock Pattern Manipulation in Exhausts Open
By numerically screening internal fluidic injection scenarios for the manipulation of the double diamond shock pattern in convergent–divergent nozzle exhausts, the individual importance of design parameters is demonstrated. It is found tha…
View article: Effect of Clocking on Compressor Noise Generation
Effect of Clocking on Compressor Noise Generation Open
The effect of stator clocking on the acoustic noise-generation characteristics in an axial high-pressure compressor is analyzed. A realistic geometry with 1.5 stages is assessed using high-fidelity and low-order numerical methods for diffe…
View article: <i>G</i>-equation modelling of thermoacoustic oscillations of partially premixed flames
<i>G</i>-equation modelling of thermoacoustic oscillations of partially premixed flames Open
Numerical simulations aid combustor design to avoid and reduce thermoacoustic oscillations. Non-linear heat release rate estimation and its modelling are essential for the prediction of saturation amplitudes of limit cycles. The heat relea…