Computational and Scientific Engineering

(Image: HLRS)

HPC technologies enable researchers to accelerate research and development in industrial processes. Simulation and modelling allow researchers to shorten time-to-market for new products, while also providing new insights into older technologies for power generation, air travel, and urban planning, among others.

The following is a list of recent reports submitted by users of HLRS's high-performance computing systems describing their scientific interests and research results.

Click on each title for a more detailed report. The complete reports are found on the website of the Gauss Centre for Supercomputing (GCS), the alliance of Germany's three national supercomputing centers.

Towards the Simulation of the Flow Phenomena at a Helicopter Rotor Using a High-order Method
The aerodynamic flow field around helicopters is challenging to simulate due to complex configurations in relative motion. In an effort to evolve computational fluid dynamics (CFD) technology to new levels of accuracy, reliability, and parallelization efficiency, the helicopter & aeroacoustics group at the IAG of University of Stuttgart employs advanced, high-order Discontinuous Galerkin (DG) methods to help solve difficult rotorcraft-based engineering applications. Complex geometries, curved surfaces, relative motion with elaborate kinematics, and fluid-structure coupling to blade dynamics call for sophisticated techniques within the simulation tool chain to account for all important physical phenomena relevant to the field of study.
Principal Investigator: Manuel Keßler
Affiliation: Institute of Aerodynamics and Gas Dynamics, University of Stuttgart

Uncertainty Quantification in Direct Noise Computations of Cavity Feedback
In order to quantify the uncertainty due to stochastic input in computer fluid dynamic simulations, researchers from the Institute of Aerodynamics and Gas Dynamics developed an Uncertainty Quantification framework and applied it to direct noise computations of aeroacoustic cavity flows. Simulations have been performed with the discontinuous Galerkin spectral element method on HPC system Hazel Hen at the High Performance Computing Center Stuttgart (HLRS). The aim of this investigation is to gain insight into the sensitivity of uncertain input with respect to the acoustic results and to get a reliable comparison between numerical and experimental results.
Principal Investigator: Andrea Beck(1), Claus-Dieter Munz(1), Christian Rohde(2)
Affiliation: (1) Institute of Aerodynamics and Gas Dynamics, University of Stuttgart, (2) Institute of Applied Analysis and Numerical Simulation, University of Stuttgart

Wall-Resolved Large Eddy Simulation of Complex Flows in Turbomachines
In order to analyse the complex flow in rotating turbomachinery components, researchers from the Institute for Aerodynamics and Gas Dynamics performed high fidelity, large-scale turbulent flow computations of stator-rotor interactions using the discontinuous Galerkin spectral element method on the HPC system Hazel Hen at the High Performance Computing Center Stuttgart (HLRS). The aim of this investigation is to gain insight into the intricate time-dependent behaviour of these flows and to inform future design improvements.
Principal Investigator: Andrea Beck, Claus-Dieter Munz
Affiliation: Institute of Aerodynamics and Gas Dynamics, University of Stuttgart

Numerical Simulation of Impinging Jets
An effective cooling of the gas turbine components subject to high thermal stresses is vital for the success of new engine and combustion concepts aiming at achieving further improvements in the energy conversion efficiency of the overall machine. The use of pulsating impinging jets - which enlarge vortex structures naturally occurring in the impinging jet flow when no pulsation is enforced - is a promising approach to develop a substantially more performant cooling system. To gain a deeper understanding of how the vortex system behaves under realistic conditions, researchers performed a DNS of a non-pulsating impinging jet flow with fully turbulent inflow conditions and compared its results with a reference case with a laminar inflow.
Principal Investigator: Jörn Sesterhenn
Affiliation: Institut für Strömungsmechanik und Technische Akustik, Technische Universität Berlin

Large Eddy Simulation of a Complete Francis Turbine
In recent years, hydroelectric power plants have received increased attention for the role they play in integrating volatile renewable energies that contribute to stabilizing the electrical grid. One major issue, though, is rooted in running turbines under conditions they were not originally designed for, leading to undesirable flow phenomena. With the standard modeling approaches that are typically used in industry simulations of hydroelectric turbines, simulation accuracy in scenarios where the turbine is used off-design is rather poor. The goal of this project is to increase simulation accuracy by the selection of suitable modeling approaches and the use of a fine mesh resolution, which is only possible by the use of supercomputers.
Principal Investigator: Timo Krappel
Affiliation: Institute of Fluid Mechanics and Hydraulic Machinery, University of Stuttgart

Shock-related Buffeting in Aeroplanes
Shock-related buffeting is a phenomenon that occurs when air passes over the wing of an aeroplane under extreme conditions and can have profound consequences for how wings are engineered and their durability. Leveraging the computing capacities of HPC system Hazel Hen, researchers at the University of Southampton have been investigating this phenomenon using direct numerical simulations.
Principal Investigator: Neil Sandham
Affiliation: Faculty of Engineering and Physical Sciences, University of Southampton (U. K.)

Numerical Simulation of Primary Break-up in Spray Painting Processes
Spray painting is the most common application technique in coating technology. Typical atomizers used in spray coating industries are such as High-speed rotary bell and spray guns with compressed air. High-speed rotary bell atomizers provide an excellent paint film quality as well as high transfer efficiencies (approx. 90%) due to electrostatic support. Small and medium-sized enterprises continue, however, to use compressed air atomizers, although they no longer meet today's requirements from an economic and environmental point of view. It is very important to understand the atomization mechanisms of these two kinds of atomizers, in order to improve the paint quality, to reduce the overspray and to optimize the coating process.
Principal Investigator: Qiaoyan Ye and Bo Shen
Affiliation: Fraunhofer Institute for Manufacturing Engineering and Automation, Stuttgart

Simulation of Turbulent Flows Interacting with Non-Spherical Particles
Researchers of the Institute of Aerodynamics (AIA) at RWTH Aachen University conducted large-scale benchmark simulations on supercomputer Hazel Hen of the High-Performance Computing Center Stuttgart to analyze the interaction of non-spherical particles with turbulent flows. These simulations provide a unique data base for the development of simple models which can be applied to study complex engineering problems. Such models are required in a larger research framework to improve the efficiency of pulverized coal and biomass combustion to significantly reduce the CO2 emissions.
Principal Investigator: Wolfgang Schröder
Affiliation: Institute of Aerodynamics, RWTH Aachen University (Germany)

Fully Resolved Autoigniting Transient Jet Flame Simulation
Transient mixing and ignition play a significant role in many systems, where combustion efficiency and emissions are controlled by ignition and mixing dynamics. In the present work, high fidelity simulations of a pulsed fuel injection system are carried out using state of the art numerical tools and high-performance computing. The results contain all parameters that affect ignition dynamics and are mined and analyzed. The physics of transient reactive turbulent jets are thus identified and presented that partners in industry and academia can improve their understanding of the process and work on the design of better combustion devices.
Principal Investigator: Andreas Kempf
Affiliation: Institute for Combustion and Gas Dynamics, Chair of Fluid Dynamics, University of Duisburg-Essen

Simulation of Non-Ideal Effects in Shock-Tubes
Shock-tube experiments are a classical technique to provide data for reaction mechanisms and thus help to reduce emissions and increase the efficiency of combustion processes. A shock-tube experiment at critical conditions (low temperature), where the ignition occurs far away from the end wall, is simulated. Understanding the mechanism that leads to such a remote ignition is crucial to improve the quality of future experiments.
Principal Investigator: Andreas Kempf
Affiliation: Institute for Combustion and Gas Dynamics, Chair of Fluid Dynamics, University of Duisburg-Essen

Multi-Scale Study of Reactive Engine Spray
In order to support sustainable powertrain concepts, synthetic fuels show significant potential to be a promising solution for future mobility. It was found that the formation of soot and CO2 emissions during the energy transformation process of synthetic fuels can be reduced compared to conventional fuels and that sustainable fuel production pathways exists. Simulations of these multiphase, reactive systems are needed to fully unlock the potential of new powertrain concepts. Due to the large separation of scales, these simulations are only possible with current supercomputers.
Principal Investigator: Heinz Pitsch
Affiliation: Institute for Combustion Technology, RWTH Aachen University, Germany

Large-Eddy-Simulations of the Unsteady Aerodynamics of Oscillating Airfoils at Moderately High Reynolds Numbers
Recently there has been a large push in the aircraft industry to reduce its carbon footprint. Laminar flow control and Natural Laminar Flow (NLF) wing design have been proposed as one of the main options for reducing the drag on the airplane and hence its fuel consumption. One of the important aspects of aircraft design concerns dynamic stability and an understanding of the unsteady behavior of NLF airfoils is important for predicting the stability characteristics of the aircraft. Recent experimental studies on NLF airfoils have shown that their dynamic behavior differs from that of turbulent airfoils and that classical linearized models for unsteady airfoils fail to predict the unsteady behavior of NLF airfoils. Most notably, NLF airfoils exhibit non-linear aerodynamic responses to small-amplitude pitch oscillations whereas the classical theories predict only a linear response. In the current work we investigate the dynamics of pitching airfoils to understand the flow phenomenon which causes the breakdown of classical models, and also attempt to describe a new simplified model which takes into account the non-linearities observed in the NLF airfoils.
Principal Investigator: Dan S. Henningson
Affiliation: KTH Royal Institute of Technology, Stockholm (Sweden)

Influence of Topography on the Turbulent Inflow of Wind Turbines in Complex Terrain
As part of the WindForS project WINSENT two wind turbines and four met masts will be installed in the Swabian Alps in Southern Germany for research proposes. The results of highly resolved numerical simulations of this wind energy test site located in complex terrain are shown. By means of Delayed Detached Eddy Simulations (DDES) the turbulent flow above a forested steep slope is analyzed in order to evaluate the inflow conditions of the planned wind turbine in detail. The complex inflow conditions and production of turbulence due to the shape of the topography and the vegetation are evaluated. The intention of using supercomputers for these applications is to analyze the local atmospheric flow field in as much detail as possible.
Principal Investigator: Thorsten Lutz
Affiliation: Institute of Aerodynamics and Gas Dynamics (IAG), University of Stuttgart (Germany)

Accident Scenario in a Nuclear Power Plant
The accident management in a generic nuclear power plant containment with a convection flow of high-temparature gases is simulated. An activated spray mixes the turbulent flow and inhibits the formation of a possibly explosive upper region filled with hydrogen. Condensation of the steam is promoted and the maximum pressure, which may also endanger the containment integrity, is limited.
Principal Investigator: Eckart Laurien
Affiliation: Institute of Nuclear Technology and Energy Systems (IKE), University of Stuttgart (Germany)

Simulation of Cavitation Phenomena in Francis Turbines
In the last decades, hydro power plants have experienced a continual extension of the operating range in order to integrate other renewable energy sources into the electrical grid. When operated at off-design conditions, the turbine experiences cavitation which may reduce the power output and can cause severe damage in the machine. Cavitation simulations are necessary to investigate phenomena like the full load instability. The goal of this project is to understand the physical mechanisms that result in an instability at off-design conditions to identify measures that can avoid the occurrence of instability.
Principal Investigator: Jonas Wack
Affiliation: Institute of Fluid Mechanics and Hydraulic Machinery, University of Stuttgart (Germany)

HEat (and Mass) Transfer in Turbulent Sprays - HETS
The focus of this project is the direct numerical simulation (DNS) of an evaporating spray in a turbulent channel flow. The complexity of the phenomenon lies in the nonlinear interaction of phase change thermodynamics and turbulent transport mechanisms at a multitude of scales. The recent availability of larger supercomputing power, together with our novel technique to treat efficiently the interface resolved phase change, enables us to perform the first DNS of more than 14k droplets evaporating in turbulent flow, with full coupling of momentum, heat and mass transfer, both intra- and inter-phase.
Principal Investigator: Luca Brandt
Affiliation: Department of Mechanics, KTH, Royal Institute of Technology (Sweden)

Highly-Resolved Numerical Simulation of Combustion in Energy Conversion Processes
Direct numerical simulation (DNS) has been applied to study the noise emitted by combustion processes. A highly efficient numerical tool based on the public domain code OpenFOAM has first been developed for DNS of chemically reacting flows, including detailed calculations of transport fluxes and chemical reactions. It has then be used to simulate different turbulent flame configurations to gain an insight into the flame-turbulence interaction, which represents the main noise generation mechanisms. Based on the DNS results, simple correlation models have been developed to predict combustion noise by means of unsteady heat release due to turbulent combustion.
Principal Investigator: Hening Bockhorn
Affiliation: Engler-Bunte-Institute/Combustion Technology, Karlruhe Institute of Technology (Germany)

Direct Numerical Simulation of Turbulent Flow Past an Acoustic Cavity Resonator
A cavity (a hollow in an object) in a turbulent gas flow often leads to an interaction of vortex structures and acoustics. By exploiting this interaction, in some applications sound can be suppressed: silencers for jet engines (so-called Liner) or exhausts. In other cases, sound can be equally produced: squealing of open wheel-bays (i.e. aircraft during take-off and landing), sunroof and window buffeting (any vehicle), noise of pipeline intersection and tones of wind instruments (i.e. transverse flute, pipe organ). Typically, in expansive experimental runs, various configurations are tested in order to fulfill the design objectives of the respective application. Based on a `Direct Numerical Simulation’, the aim is to improve the understanding of the interactions between turbulence and acoustics of cavity resonators and to develop standalone sound prediction models, which improve and simplify the design process.
Principal Investigator: Lewin Stein
Affiliation: Institut für Strömungsmechanik und Technische Akustik, Technische Universität Berlin (Germany)

Extreme-Scale Molecular Dynamics Simulation of Droplet Coalescence
The coalescence of nano-droplets is investigated using the highly optimized molecular dynamics software ls1 mardyn. Load balancing of the inhomogeneous vapor-liquid system is achieved through k-d trees, augmented by optimal communication patterns. Several solution strategies that are available to compute molecular trajectories on each process are considered, and the best strategy is automatically selected through an auto-tuning approach. Recent simulations that focused on large-scale homogeneous systems were able to leverage the performance of the entire Hazel Hen supercomputer, simulating for the first time more than twenty trillion molecules at a performance of up to 1.33 Petaflops.
Principal Investigator: Philipp Neumann
Affiliation: Scientific Computing Group, Universität Hamburg (Germany)

Numerical Simulation of Rotary Wing Aerodynamics, Aeroelasticity and Aeroacoustics (HELISIM)
Researchers of the Insitute of Aerdynamics and Gasdynamics at the University of Stuttgart leverage high-performance computing to analyse the behaviour of helicopters during various states of flight. Investigations range from deep analyses of fundamental aerodynamic phenomena like dynamic stall on the retreating blade to surveys over a broad spectrum of flight states over the full flight envelope of new configurations, to reduce flight mechanical risks. Recently, the group was able to simulate the first robust representation of the so-called tail-shake phenomenon—an interference between the aerodynamic wake of the rotor and upper fuselage and the tail boom with its elastic behaviour.
Principal Investigator: Manuel Keßler
Affiliation: Institut für Aerodynamik und Gasdynamik, Universität Stuttgart (Germany)

CARo - Computational Aeroacoustics of Rotors
Using state-of-the-art simulation technology for highly resolved computational fluid dynamics (CFD) solutions, the helicopter and aeroacoustics group at the Institute of Aerodynamics and Gasdynamics at the University of Stuttgart has simulated the complex aerodynamics, aeromechanics, and aeroacoustics of rotorcraft for years. By advancing the established flow solver FLOWer, which now integrates higher order accuracy and systematic concentration of spatial resolution in targeted regions, the IAG-based group was able to obtain results for complete helicopters at certification-relevant flight states within the variance of individual flight tests for the aerodynamic noise.
Principal Investigator: Manuel Keßler
Affiliation: Institut für Aerodynamik und Gasdynamik, Universität Stuttgart

Towards Exascale Simulations of Plasma Fusion Devices
The generation of clean, sustainable energy from plasma fusion reactors is currently limited by the presence of microinstabilities that arise during the fusion process, despite international efforts such as the ITER experiment, currently under construction in southern France. Numerical simulations are crucial to understand, predict, and control plasma turbulence with the help of large-scale computations. Due to the high dimensionality of the underlying equations, the fully resolved simulation of the numerical ITER is out of scope with classical discretization schemes, even for the next generation of exascale computers. With five research groups from mathematics, physics, and computer science, the SPPEXA project EXAHD has proposed to use a hierarchical discretization scheme, so-called Sparse Grids, to overcome the current computational limits (number of discretization points per dimension and memory requirements). This way, it will be possible to enable high-resolution simulations, to ensure scalability of the simulations to future exascale computers and beyond, and even to be able to cope with faults and failures which will be more frequent for the next generation of supercomputers.
Principal Investigator: Dirk Pflüger
Affiliation: Institute for Parallel and Distributed Systems, University of Stuttgart (Germany)

Direct Numerical Simulation of Turbulent Heat Transfer with a Supercritical Fluid
In the quest for efficiency enhancement in energy conversion, supercritical carbon dioxide (sCO2) is an attractive alternative working fluid. However, the heat transfer to sCO2 is much different in the supercritical region than the subcritical region due to the strong variation of thermophysical properties which bring the effects of flow acceleration and buoyancy. The peculiarity in heat transfer and flow characteristics cannot be predicted accurately by using conventional correlations or Reynolds-Averaged Naiver-Stokes (RANS) simulations based on the turbulence models. Therefore, direct numerical simulation (DNS) is used in this ongoing project at Institute of Nuclear Energy and Energy Systems (IKE) at the University of Stuttgart. In DNS, the Naiver-Stokes equations are numerically solved without any turbulence models. For this accurate and reliable approach, one needs to resolve very fine spatial and temporal scales, which ultimately results in the requirement of high-performance computing platforms, such as Hazel Hen at HLRS.
Principal Investigator: Eckart Laurien
Affiliation: Institute of Nuclear Energy and Energy Systems (IKE), University of Stuttgart (Germany)

Fathoming the Processes inside Rocket Combustion Chambers
At the Institute of Combustion Technology for Aerospace Engineering (IVLR) of the University of Stuttgart a team of scientists numerically investigates reacting flows at conditions typical for modern space transportation systems. The goal of the project is the better understanding of the ongoing processes in the combustion chambers and an improvement of the thermal load predictions. The research is integrated into the program "Technological Foundations for the Design of Thermally and Mechanically Highly Loaded Components of Future Space Transportation Systems" funded by the DFG.
Principal Investigator: Peter Gerlinger
Affiliation: Institut für Verbrennungstechnik der Luft- und Raumfahrt, Universität Stuttgart (Germany)

Numerical Analysis of Space Launcher Wake Flows
A research group from the Institute of Aerodynamics (AIA) of the RWTH Aachen University utilized the computing power of Hazel Hen for large-scale simulations to analyze the intricate wake flow phenomena of space launchers. The objective of the project is the fundamental understanding of the origin of so called buffet loads acting on the nozzle which can lead to critical structural damage and to develop flow control devices to increase the efficiency and reliability of orbital transportation systems necessary for the steadily increasing demand for communication and navigation satellites.
Principal Investigator: Wolfgang Schröder
Affiliation: Institute of Aerodynamics, RWTH Aachen University (Germany)

Simulation of Turbulent Flow Around a Wing
This project aims at the simulation of the influence of a turbulent atmospheric boundary layer flow on a wing. For this purpose the compressible flow solver DLR-TAU is used, which is developed by the German Aerospace Center (DLR). For initialising the simulation with a turbulent wind field a method to generate synthetic turbulence is used. This method uses statistics from measured time series from the atmospheric boundary layer to generate a threedimensional turbulent wind field which can be used as initial field in the flow simulations.
Principal Investigator: Torsten Auerswald and Jens Bange
Affiliation: Center for Applied Geoscience, University of Tübingen (Germany)