TY - JOUR A1 - Christen, Marc A1 - Kowalski, Julia A1 - Bartelt, Perry T1 - RAMMS: Numerical simulation of dense snow avalanches in three-dimensional terrain JF - Cold Regions Science and Technology N2 - Numerical avalanche dynamics models have become an essential part of snow engineering. Coupled with field observations and historical records, they are especially helpful in understanding avalanche flow in complex terrain. However, their application poses several new challenges to avalanche engineers. A detailed understanding of the avalanche phenomena is required to construct hazard scenarios which involve the careful specification of initial conditions (release zone location and dimensions) and definition of appropriate friction parameters. The interpretation of simulation results requires an understanding of the numerical solution schemes and easy to use visualization tools. We discuss these problems by presenting the computer model RAMMS, which was specially designed by the SLF as a practical tool for avalanche engineers. RAMMS solves the depth-averaged equations governing avalanche flow with accurate second-order numerical solution schemes. The model allows the specification of multiple release zones in three-dimensional terrain. Snow cover entrainment is considered. Furthermore, two different flow rheologies can be applied: the standard Voellmy–Salm (VS) approach or a random kinetic energy (RKE) model, which accounts for the random motion and inelastic interaction between snow granules. We present the governing differential equations, highlight some of the input and output features of RAMMS and then apply the models with entrainment to simulate two well-documented avalanche events recorded at the Vallée de la Sionne test site. KW - RAMMS KW - snow KW - avalanche Y1 - 2010 U6 - https://doi.org/10.1016/j.coldregions.2010.04.005 SN - 1872-7441 VL - 63 IS - 1-2 SP - 1 EP - 14 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Christen, Marc A1 - Bartelt, Perry A1 - Kowalski, Julia T1 - Back calculation of the In den Arelen avalanche with RAMMS: Interpretation of model results JF - Annals of Glaciology N2 - Two- and three-dimensional avalanche dynamics models are being increasingly used in hazard-mitigation studies. These models can provide improved and more accurate results for hazard mapping than the simple one-dimensional models presently used in practice. However, two- and three-dimensional models generate an extensive amount of output data, making the interpretation of simulation results more difficult. To perform a simulation in three-dimensional terrain, numerical models require a digital elevation model, specification of avalanche release areas (spatial extent and volume), selection of solution methods, finding an adequate calculation resolution and, finally, the choice of friction parameters. In this paper, the importance and difficulty of correctly setting up and analysing the results of a numerical avalanche dynamics simulation is discussed. We apply the two-dimensional simulation program RAMMS to the 1968 extreme avalanche event In den Arelen. We show the effect of model input variations on simulation results and the dangers and complexities in their interpretation. KW - avalanche Y1 - 2010 SN - 1727-5644 U6 - https://doi.org/10.3189/172756410791386553 VL - 51 IS - 54 SP - 161 EP - 168 PB - Cambridge University Press CY - Cambridge ER - TY - JOUR A1 - Bühler, Yves A1 - Christen, Marc A1 - Kowalski, Julia A1 - Bartelt, Perry T1 - Sensitivity of snow avalanche simulations to digital elevation model quality and resolution JF - Annals of Glaciology N2 - Digital elevation models (DEMs), represent the three-dimensional terrain and are the basic input for numerical snow avalanche dynamics simulations. DEMs can be acquired using topographic maps or remote-sensing technologies, such as photogrammetry or lidar. Depending on the acquisition technique, different spatial resolutions and qualities are achieved. However, there is a lack of studies that investigate the sensitivity of snow avalanche simulation algorithms to the quality and resolution of DEMs. Here, we perform calculations using the numerical avalance dynamics model RAMMS, varying the quality and spatial resolution of the underlying DEMs, while holding the simulation parameters constant. We study both channelized and open-terrain avalanche tracks with variable roughness. To quantify the variance of these simulations, we use well-documented large-scale avalanche events from Davos, Switzerland (winter 2007/08), and from our large-scale avalanche test site, Valĺee de la Sionne (winter 2005/06). We find that the DEM resolution and quality is critical for modeled flow paths, run-out distances, deposits, velocities and impact pressures. Although a spatial resolution of ~25 m is sufficient for large-scale avalanche modeling, the DEM datasets must be checked carefully for anomalies and artifacts before using them for dynamics calculations. KW - snow KW - avalanche Y1 - 2011 SN - 1727-5644 VL - 52 IS - 58 SP - 72 EP - 80 PB - Cambridge University Press CY - Cambridge ER - TY - JOUR A1 - Fischer, Jan-Thomas A1 - Kowalski, Julia A1 - Pudasaini, Shiva P. T1 - Topographic curvature effects in applied avalanche modelling JF - Cold Regions Science and Technology N2 - This paper describes the implementation of topographic curvature effects within the RApid Mass MovementS (RAMMS) snow avalanche simulation toolbox. RAMMS is based on a model similar to shallow water equations with a Coulomb friction relation and the velocity dependent Voellmy drag. It is used for snow avalanche risk assessment in Switzerland. The snow avalanche simulation relies on back calculation of observed avalanches. The calibration of the friction parameters depends on characteristics of the avalanche track. The topographic curvature terms are not yet included in the above mentioned classical model. Here, we fundamentally improve this model by mathematically and physically including the topographic curvature effects. By decomposing the velocity dependent friction into a topography dependent term that accounts for a curvature enhancement in the Coulomb friction, and a topography independent contribution similar to the classical Voellmy drag, we construct a general curvature dependent frictional resistance, and thus propose new extended model equations. With three site-specific examples, we compare the apparent frictional resistance of the new approach, which includes topographic curvature effects, to the classical one. Our simulation results demonstrate substantial effects of the curvature on the flow dynamics e.g., the dynamic pressure distribution along the slope. The comparison of resistance coefficients between the two models demonstrates that the physically based extension presents an improvement to the classical approach. Furthermore a practical example highlights its influence on the pressure outline in the run out zone of the avalanche. Snow avalanche dynamics modeling natural terrain curvature centrifugal force friction coefficients. KW - Snow KW - Avalanche Y1 - 2012 U6 - https://doi.org/10.1016/j.coldregions.2012.01.005 SN - 1872-7441 VL - 74-75 SP - 21 EP - 30 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Börner, Sebastian A1 - Funke, Harald A1 - Hendrick, P. A1 - Recker, E. T1 - LES of Jets In Cross-Flow and Application to the “Micromix” Hydrogen Combustion T2 - XIX International Symposium on Air Breathing Engines 2009 (ISABE 2009) : Proceedings of a meeting held 7-11 September 2009, Montreal, Canada Y1 - 2009 SN - 9781615676064 SP - 1555 EP - 1561 ER - TY - JOUR A1 - Olaru, Alexandra Maria A1 - Kowalski, Julia A1 - Sethi, Vaishali A1 - Blümich, Bernhard T1 - Exchange relaxometry of flow at small Péclet numbers in a glass bead pack JF - Journal of Magnetic Resonance (JMR) N2 - In this paper we consider low Péclet number flow in bead packs. A series of relaxation exchange experiments has been conducted and evaluated by ILT analysis. In the resulting correlation maps, we observed a collapse of the signal and a translation towards smaller relaxation times with increasing flow rates, as well as a signal tilt with respect to the diagonal. In the discussion of the phenomena we present a mathematical theory for relaxation exchange experiments that considers both diffusive and advective transport. We perform simulations based on this theory and discuss them with respect to the conducted experiments. KW - NMR exchange relaxometry KW - Low-field NMR Y1 - 2012 U6 - https://doi.org/10.1016/j.jmr.2012.04.015 SN - 1096-0856 VL - 220 SP - 32 EP - 44 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kowalski, Julia A1 - McElwaine, Jim N. T1 - Shallow two-component gravity-driven flows with vertical variation JF - Journal of Fluid Mechanics Y1 - 2013 SN - 0022-1120 VL - 714 SP - 434 EP - 462 PB - Cambridge Univ. Press CY - Cambridge ER - TY - CHAP A1 - Funke, Harald A1 - Börner, Sebastian A1 - Keinz, Jan A1 - Hendrick, P. A1 - Recker, E. T1 - Low NOx Hydrogen combustion chamber for industrial gas turbine applications“, 14th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery T2 - ISROMAC-14 : the Forteenth International Symposium on Transport Phenomena and Dynamics of Rotating Machinery ; Honolulu, Hawaii, February 27 - March 02nd, 2012 Y1 - 2012 N1 - International Symposium on Transport Phenomena and Dynamics of Rotating Machinery ; (14 ; 2012.02.27-03.02 ; Honolulu, Hawaii) ER - TY - CHAP A1 - Funke, Harald A1 - Börner, Sebastian A1 - Keinz, Jan A1 - Kusterer, K. A1 - Kroninger, D. A1 - Kitajima, J. A1 - Kazari, M. A1 - Horikama, A. T1 - Numerical and experimental characterization of low NOx Micromix combustion principle for industrial hydrogen gas turbine applications T2 - Proceedings of ASME Turbo Expo 2012 Y1 - 2013 N1 - ASME Turbo Expo 2012, GT2012, June 11-15, 2012, Copenhagen, Denmark ER - TY - BOOK A1 - Janser, Frank A1 - Havermann, Marc T1 - Inkompressible Strömungen Y1 - 2012 SN - 978-3-86130-446-3 N1 - Strömungslehre und Aerodynamik PB - Mainz CY - Aachen ER - TY - JOUR A1 - Dachwald, Bernd A1 - Schmidt, Tanja D. A1 - Seboldt, Wolfgang A1 - Auweter-Kurtz, T1 - Flight Opportunities from Mars to Earth for Piloted Missions Using Continuous Thrust Propulsion / Schmidt, Tanja D. ; Dachwald, Bernd ; Seboldt, Wolfgang ; Auweter-Kurtz, Monika Y1 - 2003 N1 - 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 20-23 July 2003, Huntsville, Alabama ; AIAA 2003-4573 SP - 1 EP - 9 PB - - ER - TY - JOUR A1 - Havermann, Marc A1 - Beylich, A. E. T1 - Combined Measurement of Velocity, Temperature and Pressure in Compressible Gas Flows Using Laser-Induced Iodine Fluorescence / Havermann, M. ; Beylich, A. E. Y1 - 1998 N1 - 9th International Symposium on Applications of Laser Techniques to Fluid Mechanics, Lisbon (Portugal), 1998 PB - - ER - TY - JOUR A1 - Havermann, Marc A1 - Seiler, F. A1 - George, A. A1 - Leopold, F. T1 - Enhanced Doppler Picture Velocimetry (DPV) for Planar Velocity Measurements in High-Speed Shock Tunnel Flow / Seiler, F. ; George, A. ; Leopold, F. ; Havermann, M. ; Srulijes, J. JF - 10th International Symposium on Flow Visualization : Kyōto, Japan, August 26 - 29, 2002 / sponsored by International Flow Visualization Society . [Chairman:] Toshio Kobayashi Y1 - 2002 SN - 4906497829 N1 - International Symposium on Flow Visualization ; (10 ; 2002.08.26-29 ; Kyōto) PB - Visualization Society of Japan CY - Kyoto ER - TY - JOUR A1 - Havermann, Marc A1 - Salve, M. de A1 - Tin, G. del A1 - Panella, B. T1 - Experimental Study of the Temperature Field along a Density Lock / Salve, M. de ; Tin, G. del ; Panella, B. ; Sansoldo, D. ; Havermann, M. JF - Proceedings : International Conference on New Trends in Nuclear System Thermohydraulics, May 30th - June 2nd, 1994, Pisa / organized by Dipartimento di Costruzioni Meccaniche e Nucleari ... . Ed. by Francesco Oriolo Y1 - 1994 N1 - International Conference on New Trends in Nuclear System Thermohydraulics ; (1994.05.30-06.02 ; Pisa) SP - 623 EP - 630 PB - - CY - Pisa ER - TY - JOUR A1 - Havermann, Marc A1 - Haertig, J. A1 - Rey, C. A1 - George, F. T1 - PIV measurements in Mach 3.5 and 4.5 shock tunnel flow / Haertig, J. ; Havermann, M. ; Rey, C. ; George, F. Y1 - 2001 N1 - AIAA-2001-699 Aerospace Sciences Meeting and Exhibit, 39th, Reno, NV, Jan. 8-11, 2001 PB - - ER - TY - JOUR A1 - Havermann, Marc T1 - Systematic Shock Tube Experiments on Vortex Ring Generation and Propagation / Havermann, M. ; Kainuma, M. ; Takayama, K. JF - Shock waves : proceedings of the 25th International Symposium on Shock Waves-ISSW25, July 17 - 22, 2005, Bangalore, India / ed.: G. Jagadeesh Y1 - 2006 SN - 978-81-7371571-6 N1 - International Symposium on Shock Waves ; 25 (Bangalore) : 2005.07.17-22 ISSW ; 25 (Bangalore) : 2005.07.17-22 PB - Universities Pr. CY - Hyderabad ER - TY - JOUR A1 - Havermann, Marc A1 - Kainuma, M. A1 - Takayama, K. T1 - Influence of Physical and Geometrical Parameters on Vortex Rings Generated by a Shock Tube / Havermann, M. ; Kainuma, M. ; Takayama, K. JF - Non-lethal options enhancing security and stability : 3rd European Symposium on Non-Lethal Weapons, May 10 - 12, 2005, Ettlingen, Germany / ICT, Fraunhofer-Institut Chemische Technologie; European Working Group Non-Lethal Weapons Y1 - 2005 N1 - European Symposium on Non-Lethal Weapons ; (3 ; 2005.5.10-12 ; Ettlingen); V 24 PB - ICT CY - Pfinztal ER - TY - JOUR A1 - Havermann, Marc A1 - Moeglin, J.-P. T1 - ISL's Research on Systems with Controlled Effects for Non-Lethal Applications / Moeglin, J.-P. ; Havermann, M. et al. JF - Non-lethal options enhancing security and stability : 3rd European Symposium on Non-Lethal Weapons, May 10 - 12, 2005, Ettlingen, Germany / ICT, Fraunhofer-Institut Chemische Technologie; European Working Group Non-Lethal Weapons Y1 - 2005 N1 - European Symposium on Non-Lethal Weapons ; (3 ; 2005.5.10-12 ; Ettlingen); P 35 PB - ICT CY - Pfinztal ER - TY - BOOK A1 - Havermann, Marc T1 - Development of a free flight force measuring (FFM) technique at the ISL shock tube laboratory : 25th International Symposium on Shock Waves, ISSW25, Bangalore, India, July 17 - 22, 2005 / Institut Franco-Allemand de Recherches de Saint-Louis. Seiler, F. ; Mathieu, G. ; George, A. ; Srulijes, J. ; Sauerwein, B. ; Havermann, M. Y1 - 2005 N1 - Publication / Institut Franco-Allemand de Recherches de Saint-Louis ; 620 PB - ISL CY - Saint-Louis ER - TY - BOOK A1 - Havermann, Marc A1 - Seiler, F. A1 - Gnemmi, P. A1 - Ende, H. T1 - Study on lateral jet/cross flow interaction in the High Energy ISL Shock Tunnel : 23rd International Symposium on Shock Waves, Fort Worth/TX, USA, July 22 - 27, 2001 / Institut Franco-Allemand de Recherches de Saint-Louis. Seiler, F. ; Gnemmi, P. ; Ende, H. ; Havermann, M. ; Schwenzer, M.... Y1 - 2001 PB - ISL CY - Saint-Louis ER -