1. Computational Fluid Dynamics and Applied Multi-Physics Center, Center for Innovation in Gas Research and Utilization (CIGRU), Center for Alternative Fuels, Engines and Emissions (CAFEE), Department of Mechanical and Aerospace Engineering, West Virginia University, 1306 Evansdale Drive, Morgantown, West Virginia 26506-6106, USA
2. Department of Physics, Umeå University, 901 87 Umeå, Sweden