ENVIRONMENT AND ENERGY

In the framework of the ASCETE (Advanced Simulation of Coupled Earthquake and Tsunami Events) project, the computational seismology group of LMU Munich and the high performance computing group of TUM jointly used the SuperMUC HPC infrastructures for running large-scale modeling of earthquake rupture dynamics and tsunami propagation and inundation, to gain insight into earthquake physics and to better understand the fundamental conditions of tsunami generation. The project merges a variety of methods and topics, of which we highlight selected results and impacts in the following sections.

A multi-institutional team of researchers is developing a data assimilation framework for coupled atmosphere-land-surface-groundwater models. These coupled models, which potentially allow a more accurate description of the coupled terrestrial water and energy fluxes, in particular fluxes across compartments, are affected by large uncertainties related to uncertain input parameters, initial conditions and boundary conditions. Data assimilation can alleviate these limitations and this project is focused in particular on the value of coupled data assimilation which means that observations in one compartment (e.g., subsurface) are used to update states, and possibly also parameters, in another compartment (e.g., land surface).

To avoid dangerous climate change, we have to reduce the emission of greenhouse gases radically. This requires – among other measures – an increase of renewable sources of energy like solar and wind. In 2019, already a quarter of Germanys electricity demand has been met by wind power. In order to increase this share, one has to develop sites in hilly terrain. High resolution models are required to assess the suitability of candidate sites with respect to turbulence intensity, power production and variability. This project supports the development of the test-site WINSENT, which is located on the Swabian Alp near Stuttgart.

Rotating convection is ubiquitous in geophysical systems. In generates the Earth magnetic field, stirs the deep atmospheres of giant planets and possibly also drives their strong surface winds. A thorough understanding of these objects requires comprehensive insight into the physics of turbulent convective flows that are strongly constrained by Coriolis forces. Numerical simulations reveal the full three-dimensional structure of the flow, and can be used to guide theoretical modeling.

Regional climate simulations at the convection-permitting scale (< 4 km) have the potential to improve seasonal forecasts, especially where complex topography hinders global models. Due to high computational costs, tests using state-of-the-art ensemble forecasts have not been performed yet. In this one-year case study, a Weather Research and Forecasting (WRF) multi-physics ensemble was used to downscale the SEAS5 ensemble forecast over the Horn of Africa. Reliability of precipitation prediction is improved, although the global model’s biases in temperature and precipitation are not reduced. Measurable added value against the global model is provided for intense precipitation statistics over the Ethiopian highlands.

A new avenue towards the study of the Planetary Boundary Layer (PBL), namely direct numerical simulation, is pursued in this project. The geophysical problem—characterized by enormous number of degrees of freedom—is condensed to its fluid mechanical core and solved explicitly which does not require assumptions or closures for the turbulent exchange of heat pollutants, heat and momentum: It rather represents the whole cascade of turbulent motion in a miniature problem. For the first time, this allows to quantify and understand surface fluxes without utilization of simplifying assumptions and theories such as Monin—Obukhov Similarity Theory.

Hydrometeorological extremes, such as droughts and floods are one of the grand challenges of our future and pose great interest and concern for water management and public safety. Hence, the ClimEx project disaggregates the response of the climate system into changing anthropogenic forcing and natural variability by analyzing a novel large-ensemble of climate simulations, operated using High-Performance Computing. The comprehensive new dataset (CRCM5-LE) generated 50 transient independent and evenly likely realizations of the past and the future climate (1950-2099) over two large domains (Europe, Eastern North America) in high spatial (12km) and temporal (1h-1d) resolution. The resulting 7500 model years allow for a thorough analysis of…

Using the Model for Prediction Across Scales (MPAS), four years of climate simulations at convection-permitting resolutions where carried out using a variable 30-3km resolution mesh, transitioning the so-called gray zone of convection around 5-10km. The comprehensive data set generated following the protocol of the CORDEX Flagship Pilot Study (FPS) on convection-permitting climate simulations will allow the CORDEX-FPS community to study the added value of global, variable-resolution simulations down to convective scales over traditional approaches employing regional climate models and/or coarse horizontal resolutions.

Without its magnetic field, life on Earth’s surface is impossible, since the magnetic field screens us from deadly solar radiation. In order to gain a better understanding of the generation of Earth’s magnetic field and heat flow in the Earth--which is crucial for understanding Earth's history--scientists have performed large scale simulations of crystalline and liquid iron alloys at conditions of Earth’s core, up to 6000K and over 300 million atmospheres of pressure, and have computed the electrical and thermal conductivity. The computationally very intensive first-principles molecular dynamics simulations for fluids required more than 60 million core hours of computing time on SuperMUC.

Data Assimilation is an integral tool to enable precise forecasts and becomes increasingly important to derive the values of uncertain parameters due to lack of observations. Numerical models of Earth system compartments are coupled in order to simulate physically consistent water and energy fluxes in the subsurface-landsurface-atmosphere system. Such model systems become increasingly important to analyze and understand the complex processes at boundaries of terrestrial compartments and interdependencies of states across these boundaries. As such, data assimilation for these coupled systems needs to be developed.

Modelling of the regional present day as well as future climate is of great interest both scientifically as well as for applications. The “Regional Climate and Water Cycle Group” at KIT Karlsruhe uses the COSMO-CLM regional climate model for detailed climate simulations in various parts of the world. Many of these quite expensive and storage intensive runs are performed on Hazel Hen at HLRS. After giving a motivation for high resolution climate modelling, the scientists briefly describe some technical aspects like nesting and ensemble building and then go to a short presentation of some results concerning the future climate in Baden-Württemberg.

Understanding the physics of earthquake rupture occurring on multiple scales and at depths that cannot be probed directly is a ‘Grand Challenge’ of Earth sciences. Geophysicists at the Ludwig-Maximilians-Universität use the in-house-developed SeisSol earthquake simulation software to improve fundamental comprehension of earthquake dynamics by numerical simulation of complicated wave and rupture phenomena.

Gas exchange across water surfaces receives increasing attention because of its importance to the global greenhouse budget. At present, most models used to estimate the gas flux only consider wind-shear. To improve the accuracy of the predictions a detailed study of buoyancy-driven gas transfer, which is a major contributor at low to moderate wind-speed, is necessary.  The main challenge lies in resolving the extremely thin gas concentration boundary layer. To address this, direct numerical simulations (DNS) of gas transfer induced by surface-cooling were performed on SuperMUC using a numerical scheme that is capable of resolving the thin diffusive layers on a relatively coarse mesh while avoiding spurious oscillations of the scalar…

The SMOC (SubMesoscale Ocean Modelling for Climate) project aimed to shed light on the role of submesoscale turbulent processes in the overall functioning of the ocean. Leveraging HPC power, the researchers in particular tried to get answers to: A) how deep do submesoscale fronts penetrate and can they be a significant source of dissipation for the ocean circulation away from the surface?, and B) to which extent do submesoscale fronts participate in the transfer into the deep ocean of the near-inertial energy injected by the wind at the ocean surface?

Turbulence-chemistry interaction in well characterized partially premixed and premixed laboratory-scale experiments has been investigated numerically by two different methods (M1 & M2) based on the large eddy simulation (LES) technique. It could be shown that the developed transported filtered density function method (M1) is capable of reproducing the turbulence chemistry interaction in the investigated opposed jet flame configurations. The flame resolved simulations (M2) revealed the importance of flame wrinkling and scalar geometry for flame propagation and allowed for further development of sub-filter models for future LES.

Two-phase flows with water droplets greatly affect the thermal-hydraulic behaviour in the containment of a Pressurized Water Reactor (PWR). In order to predict the local thermal-hydraulic behaviour in a real containment in the case of a severe accident, scientists of the University of Stuttgart generated a three-dimensional geometry of a model containment based on a German PWR. 

Scientists of the RWTH Aachen University have carried out a peta-scale direct numerical simulation (DNS) of a temporally evolving lean premixed methane/air jet flame. The DNS is intented to closely mimic gas turbine combustion and can be regarded as an idealized representation of a premixed flame element inside a jet burner. To realize high resolution of flame and turbulence and to obtain converged statistics, the simulation domain was discretized with almost three billion grid points which together with the chemistry model resulted in nearly 100 billion degrees of freedom.

Predicting weather and climate and its impacts on the environment, including hazards such as floods, droughts and landslides, continues to be one of the main challenges of the 21st century – in particular for the European region as it is exposed to intense Atlantic synoptic perturbations. Scientists performed for the first time long climate simulations over the European domain at a very fine cloud-permitting resolution of about 4 km with explicitly resolved convection and a sharp representation of orography, thanks to the possibility of running very computationally and data storage demanding simulations on SuperMUC.

Thanks to the availability of HLRS’s petascale HPC system Hornet, researchers of the Institute of Physics and Meteorology of the University of Hohenheim were able to run a highly complex climate simulation for a time period long enough to cover various extreme weather events on the Northern hemisphere at a previously unmatched spatial resolution. Deploying the highly scalable Weather Research and Forecasting (WRF) model on 84,000 compute cores of Hornet, the achieved results confirm an extraordinary quality with respect to the simulation of fine scale meteorological processes and extreme events.

Scientists from the University of Hohenheim (Stuttgart/Germany) aim to investigate and to improve the performance of regional climate simulations in Europe with the Weather Research and Forecast (WRF) model. The model is operated from 12 km down to the convection permitting scale of 3 km, for advancing process understanding.

The flow in the earth's atmosphere involves many complex features. One of these features are so-called gravity waves. They become important as soon as they break somewhere in the atmosphere, since this breaking results in a strong patch of turbulence for no apparent reason. In order to improve the basic understanding of the breaking process, scientists conducted high-resolution simulations of different types of gravity-wave breaking events.

Scientists of the Institute for Hydrodynamics of the Karlsruhe Institute of Technology (KIT) have – for the first time – performed high-fidelity numerical simulations of the formation of sediment patterns in a channel flow configuration.

Using the computing capabilities of HLRS system Hermit, a team of scientists used the Community Earth System Model (CESM) with a strongly eddying ocean submodel to study the presence of ocean eddies on the sensitivity of the Meridional Overturning Circulation (MOC) in the Atlantic Ocean to the Greenland Ice Sheet (GrIS) freshwater anomalies.

A team of scientists of the Technische Universtität München employed an instantaneous steady-state approximation to present steady-state reactivity data from kinetic Monte Carlo (kMC) simulations in the form of an interpolated data field as boundary conditions for the computational fluid dynamics simulation.Their goal was to test the capability of the code in managing complex computational domains, thus allowing for the first time to extend kMC simulations to geometries and conditions relevant to technological applications. 

The cold combustion in fuel cells is a promising alternative energy technology that does not produce greenhouse gases. One of the main problems of solid oxide fuel cells (SOFC) that reduces the efficiency dramatically is the chromium poisoning. The current collectors in SOFCs are made of stainless steel which contains chromium. By chemical reaction chromium can migrate into the porous cathode and react with its surface. This effect degrades the efficiency and has to be controlled.

In past decades, high performance computing has become a valuable tool in many fields of environmental science and technology to utilize computational power for better characterization of the complexity of environmental systems as well as predicting their evolution in time. The challenge is to develop efficient numerical schemes and software implementations which can take full advantage of today’s supercomputing hardware (i.e. PetaFlop platforms). The JUQUEEN project „Massive parallel computation of non-linear multi-field problems in terrestrial systems“ strives to meet this challenge for the solution of thermo-hydro-mechanical-chemical problems in fractured porous media with applications in hydrology, geotechnical engineering and renewable…

Minerals, melts and fluids are the building blocks of our planet Earth. Their formation and alteration are driven by thermodynamics and depend on pressure, temperature and the local availability of chemical elements. Geological processes are especially efficient at high temperatures as prevalent in the Earth's interior and in the presence of melts or (aqueous) fluids. However, direct observations, e.g. by deep drilling, are limited to about 12 km depth. Experimental studies at the extreme conditions of the deeper Earth are challenging and not always easy to interpret. Therefore, a good understanding of what happens beneath our feet can only be obtained by combined efforts from various disciplines of the Earth sciences.

A porous medium is a material characterized by the presence of holes, or “pores“. These pores are usually surrounded by a solid and can be filled with a gas or a liquid. In nature one can find many examples of porous media, such as many types of rock (e.g. in oil reservoirs or aquifers). Many types of man-made porous media exist too, as they can be designed to have very useful properties. For example, porous media form the basis of many types of reactors, filters, or fuel cells.

Supported by the experts of the Leibniz Supercomputing Centre (LRZ), computer scientists, mathematicians, and geophysicists of the Technische Universität München (TUM) and the Ludwig-Maximilians-Universität München (LMU) collectively optimised and completely parallelised the 70,000 lines of code of SeisSol, a software to simulate earth quakes, to optimally leverage the parallel architecture of SuperMUC.

Fusion energy is a very attractive option to provide large-scale and CO2-free electricity production for centuries to come. Here, the goal is to mimic the way the sun generates its power under laboratory conditions on earth. To this aim, one confines a plasma (i.e., an ionized gas), consisting of two heavy versions of hydrogen, namely deuterium and tritium, in a doughnut-shaped magnetic cage and heats it to about 100 million degrees. In order for this to work, however, the energy confinement – which is controlled by turbulent transport – must exceed a certain level. 

Mantle convection is a vital component of the Earth system. The relentless deformation taking place in the mantle by viscous creep has a far greater impact on our planet than might be immediately evident. Immense forces are at work in mantle convection cells: continuously reshaping Earth's surface, the mantle provides the enormous driving forces necessary to support large scale horizontal motion, in the form of plate tectonics and associated earthquake and mountain building activity.

Atmospheric processes and climate change take place on all spatial scales: global, continental down to regional or local scales. Not only do processes on the different scales differ from each other but also regions exhibit various characteristics. Regional and local climate as such depends on small-scale structures such as urbanisation, land use, soil types, water surfaces, orography and vegetation.

Ground shaking due to an earthquake not only depends on the energy radiated at the source but also on propagation effects and amplification due to the response of geological structures. A further step in the assessment of seismic hazard, beyond the evaluation of the earthquake generation potential, requires then a detailed knowledge of the local Earth structure and of its effects on the seismic wave field. 

In order to invest in a sustainable energy mix and avoid CO₂ emissions, new energy sources such as fusion energy need to be developed. Understanding turbulent transport is needed for further optimization of fusion reactors but realistic transport time scale simulations of plasma turbulence are computationally very demanding. The aim of the present project is to increase the understanding of the mechanisms behind the sudden improvement in confinement observed in experiments. 

Prediction of turbulence-induced erosion and near-bed transport of sediment particles in turbulent flow is important for many processes in environmental engineering. Beyond its relation to sediment transport, the results of the present study are relevant as well for numerous industrial applications, particularly in the field of process technology, where solid particles are conveyed by a carrier flow. Traditional methods for the prediction of sediment transport are empirical and based on averaged bulk quantities. 

To study the aerodynamics of vertical axis wind turbines (VAWT) and to carefully characterize the vortex dynamics and decay of VAWT wakes, a team of scientists conducts extensive simulation runs on GCS supercomputers.

The imaging of the Earth‘s interior three-dimensional structure is a prerequisite for the understanding of the mechanisms that drive the continental plates, shape our landscapes, and lead to earthquakes and volcanoes.

Scientists use GCS supercomputers for compute-intensive simulations in order to increase the fidelity of global climate simulations and provide quantitative information about the frequency of high-impact events and their risks. The research activity comprises a large series of global experiments (an ensemble), with each member of the ensemble dynamically simulating 27 years of both current and future climates.

Concerns about the present global energy situation and the impacts of climate change are the driving forces for optimizing combustion power plants operation towards maximum efficiency, and thus minimizing the emission of greenhouse gases. Computational modelling of the combustion process in industrial scale combustion systems has become a key technology to achieve this ambitious goal.