We describe the physics potential of e + e − linear colliders in this report. These machines are planned to operate in the first phase at a center-of-mass energy of 500 GeV, before being scaled up to about 1 TeV. In the second phase of the operation, a final energy of about 2 TeV is expected. The machines will allow us to perform precision tests of the heavy particles in the Standard Model, the top quark and the electroweak bosons. They are ideal facilities for exploring the properties of Higgs particles, in particular in the intermediate mass range. New vector bosons and novel matter particles in extended gauge theories can be searched for and studied thoroughly. The machines provide unique opportunities for the discovery of particles in supersymmetric extensions of the Standard Model, the spectrum of Higgs particles, the supersymmetric partners of the electroweak gauge and Higgs bosons, and of the matter particles. High precision analyses of their properties and interactions will allow for extrapolations to energy scales close to the Planck scale where gravity becomes significant. In alternative scenarios, like compositeness models, novel matter particles and interactions can be discovered and investigated in the energy range above the existing colliders up to the TeV scale. Whatever scenario is realized in Nature, the discovery potential of e + e − linear colliders and the high-precision with which the properties of particles and their interactions can be analysed, define an exciting physics programme complementary to hadron machines.

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Steady-state simulations of a high-flow centrifugal compressor stage with return channel for industrial applications are carried out to determine the flow conditions in a new compressor test rig at the RWTH Aachen University. Overall performance predictions, conducted by means of CFD simulations, will be shown and discussed in this paper. Furthermore, a detailed analysis of the stage components is presented, providing an insight into the flow phenomena responsible for the compressor performance. Thereby, the analysis focuses on the return channel. The compressor has a shrouded impeller with 3D-twisted blades, operating at a high flow coefficient and moderate pressure ratios, as usual for multistage single-shaft compressors. The complete computational domain consists of an inlet duct, the impeller, a vaneless diffuser and return channel with bends to guide the flow. All CFD simulations have been carried out in advance of the test rig construction. The results of the simulations have been used to define the measurement locations within the test rig. Within this paper, the predicted flow phenomena in the return channel, which are strongly three-dimensional, are detailed and analyzed against the backdrop of their origin and their contribution to the overall losses. Furthermore, the available measurement results of the overall compressor performance are compared to the numerical simulations to validate the numerical setup. The objective of this paper is to give a detailed analysis of the flow in the return channel of a new compressor test rig built up at the Institute of Jet Propulsion and Turbomachinery of the RWTH Aachen University. The investigation is conducted to get an insight into the formation processes of the dominant flow phenomena affecting the overall stage performance. These investigations can form the basis for developing new strategies for return channel improvements.

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