Fluid mechanics in centrifugal and displacement pumps, hydraulic components, and systems

The use of CFD methods is state-of-the-art in the design phase. However, the calculation of highly transient off-design operation, such as part-load and overload, places high demands on accurate turbulence modeling. Therefore, at HSM, scale-resolving and adaptive methods are practically used continuously. For some specific types of machines and operating conditions, such as low-specific-speed centrifugal pumps, single and double-blade pumps, oscillating displacement or screw spindle pumps, very accurate and specific simulation methods are required. Other research focuses include reducing CFD models to simple real-time capable models, methods for loss calculation through entropy production evaluation, and the development of coupled 3D-1D-CFD methods for holistic pump system calculations.

Multiphase flows (air degassing and transport, particle-laden flows)

Multiphase flows in hydraulic turbomachinery include, for example, gas- or particle-laden liquids. Predicting these extremely complex flows requires highly specialized CFD models, the development of which is being advanced at HSM. In both fundamental and application-oriented projects, the pumping of gas/liquid mixtures with centrifugal pumps, liquid/liquid extraction with pump mixers, and spray formation in injection processes are investigated. The interaction of multiphase and turbulence modeling is another important aspect of these studies.

Cavitation, cavitation erosion und bubble dynamics

Cavitation is the formation of small vapor- and air-filled cavities in the liquid, which is typically associated with harmful effects such as cavitation erosion. This process is a classic multiscale problem. The calculation of detailed transport processes at individual bubbles, as well as the development of CFD methods for simulating cavitating flows in pumps and ship propulsion systems, are part of the research portfolio of HSM. In particular, cavitation in complex fluids such as fuels and hydraulic oils is a research focus at HSM.

Simulation of transitional and turbulent flows

Statistical turbulence models are computationally efficient, but they can be inaccurate for highly transient flows. A research focus of HSM is the development of scale-resolving turbulence models for hydraulic machinery and components. Given the extremely high Reynolds numbers in hydraulic systems, the resolution requirements for Large-Eddy Simulation (LES) are very demanding, so turbulence-scale adaptive simulation methods (SAS) are primarily used.