1. Faculty of Mechanical and Process Engineering, Institute of Fluid Mechanics and Fluid Machinery, Technical University Kaiserslautern, Gottlieb Daimler Straße, Kaiserslautern D-67663, Germany e-mail:
2. Professor Faculty of Mechanical and Process Engineering, Institute of Fluid Mechanics and Fluid Machinery, Technical University Kaiserslautern, Gottlieb Daimler Straße, Kaiserslautern D-67663, Germany e-mail: