Fluid Power Machinery
Selected Research Projects
Optimization of the hydraulic Savonius Turbine
This project aims at maximizing the output power of a hydraulic Savonius turbine by modifying freely the blade profile for difference concave and convex sides. Twelve geometrical parameters are involved during shape optimization. 636 transient computational fluid dynamics (CFD) simulations are performed using the industrial flow simulation code Star-CCM+. Finally, the optimized shape increases the performance of Savonius turbine by 15% compared to the standard shape. The Picture shows the pressure distribution around the optimized blade turbine at two different rotation angles. The video shows the velocity distribution and streamlines around the optimized blade for one complete revaluation.
Pitot Tube Pump: High Pressure Delivery and Adaptation to the Purification of Polluted Waters
as part of the BMWI-funded ZIM-Project KF2473102VT1
Responsible person: M.Sc. Jessica Köpplin
The Pitot tube pump is a rather unknown centrifugal pump that works with low volumetric flow and high pressure. It is still used today in the purification sector of paper, food, and mining industries. Its design has not really changed over the 100 years since its development. Through the progress made in numerical methods, the optimization potential was identified and subsequently validated experimentally by industry partner bench tests. The properties of the characteristic Pitot tube are used to separate materials of different density from one another in a continuous process using a Pitot tube pump. The impeller maintains the pumping action in a manner that allows for simultaneous delivery and separation.
Figure: (left) Pitot tube pump setup purely for delivery; components with index ‘r’ rotate and index ‘f’ are stationary (right) Pitot tube pump adaptation for the continuous separation of two materials with different densities through centrifugal forces in the rotor
Figure: (left) Numerical simulations and (right) results of the first experiments using a prototype at the LSS with water and sunflower oil (Δ ρ≈70 kg/m3)
Figure: Grundidee und Forschungsergebnisse auf dem Weg zur funktionierenden Trennpumpe
Numerical Investigations and Optimization of Blood Pumps
Responsible person: M.Sc. Sebastian Engel
Blood as a medium poses great challenges to the design of blood delivery machines such as those found in operating rooms, dialysis, as well as in artificial hearts. This project examines blood pumps by modeling blood damage (mechanical hemolysis and platelet activation) and utilizing computational fluid dynamics methods. The goal is to develop methods and applications in order to improve existing types of pumps (via numerical optimization) as well as explore unusual designs. Axial pump designs have already been investigated and optimized in this endeavor. Furthermore, we participated in the FDA’s (Food and Drug Administrations) project “Critical Path – Blood Damage”.
Figure: Flow lines in the pump for the FDA’s „Critical Path“ challenge and pressure distribution on the rotor. Source: H. Yu, PhD “Flow design optimization of blood pumps considering hemolysis.”
Figure: Simulation of an axial blood pump. Shown are wall shear stress and the velocity distribution along flow lines.
Development of Modern Water Wheels
as part of the BMBF-funded “Growth Core Fluss-StromPlus” (project number 1714)
Responsible person: M.Sc. Olivier Cleynen
Nowadays, hydropower generation occurs mainly in connection with an obstruction of waterways. The operation of small-scale machines that function without congestion or obstruction — especially water wheels — is an environmentally friendly alternative. Such machines would bring our energy sector a step towards a sustainable, decentralized power grid.
The fluid mechanical consideration of equipment with a low velocity, a free surface without a dam system is, however, complex. The dynamics of two phases (air and water) need to be calculated in an unsteady, turbulent environment. 2D as well as 3D CFD models are being used in order to understand and characterize the influence of single blade geometry, rotor dimensions, or floating bodies. The numerical simulations are being carried out in parallel with experimental trials. PIV (Particle Image Velocimetry) measurements on a smaller scale model are being performed in the institute’s new water channel in order to calibrate and validate the numerical simulations. By recording parameters such as the increase in rotor power density, operation outside of the design points, tolerance of foreign bodies, and mechanical power output stability, this study shall lead to a quantitative description of the performance of modern hydraulic equipment operating at a free surface.
Figure: Velocity profile and water surface of a rotating water wheel prototype
Fluid-Structure Interaction in a Water Turbine with Deformable Blades
Responsible person: Dr.-Ing. Stefan Hörner
Compared to conventional concepts for the use of hydropower, the growth core “Flussstrom” is researching new technologies for the sustainable use of this resource. Darrieus water turbines can operate as small floating power plants in rivers and oceans or tidal currents without a dam. The vertical design offers many advantages, like ease of construction or positioning the generator outside of the water. Beyond that, this type of turbine has a higher efficiency when compared to other ecologically sound hydraulic turbomachinery.
The use of a deformable blade design shall enable the turbine to adapt to the widely varying flow conditions with every revolution. This aims to lead to improved performance and also durability, since highly alternating loads are reduced. The approach encompasses numerical simulations of coupled fluid and structure calculations for the conception and design of the blades. Additionally, the results will be verified in the water channel, which was built for growth core.
The project takes place as part of a German-French joint thesis (Cotutelle de thèse) with the Grenoble Alpes University. It is sponsored by the Franco-German University and a PhD scholarship from the Rosa Luxembourg Foundation.
Figure: left: structure of a flexible blade, right: 3D calculation mesh of a Darrieus water turbine for a CFD calculation.
Research project RETERO: Reduktion von Tierversuchen zum Schädigungsrisiko bei Turbinenpassagen durch Einsatz von Roboterfischen, Strömungssimulationen und Vorhersagemodellen" (Förderkennzeichen 031L0152A)
Responsible person: M.Sc. Dennis Powalla
The main goal of the RETERO research project is to minimize the use of live-fish in injury risk assessment in downstream turbine passages. Within this context, a new method shall be developed. This method will be based on experiments, complemented with partly-autonomous robotic sensor fish surrogates, as well as on numerical simulations, featuring a risk assessment with help of fish behaviour models and computational fluid dynamics (CFD).There are two major approach paths to this project at the laboratory.
The first is to minimize the injury and mortality rate by developing a prediction model. This model should forecast the movement of a migrating fish in a complex 3D hydrodynamic field and account for possible contacts between fish body and surrounding structures, such as moving turbine blades. The current approach is to develop a multi-agent system algorithm based on results provided by CFD simulations, where agents and associated behaviour response are derived from live-fish observations.The second part is involved in the development of a robotic fish surrogate. Forces acting on a moving fish body are assessed to gain information about the necessary forces of a propulsion device of a fish robot. The movement of the fish is realized by a morphing mesh model. The grid vertices morph to accommodate the body movement according to a predefined function in accordance to real fish motion characteristics.
Numerical Investigations of a Gravitation Water Vortex Power Plant as a Fish Ladder
as part of the BMBF-funded “Growth Core Fluss-StromPlus” (project number 1714)
The requirements for good water quality in Europe’s bodies of water also mean restoring the ecosystem and therefore allowing fish to freely migrate upstream and downstream. As a consequence, measures that are taken and structures that are built must allow for such migration. This project deals with the resulting geometric and hydraulic requirements for such structures. Based on simulation results, the suitability of a gravitation water vortex power plant as a fish ladder is underlined, since all the requirements for flow velocity are maintained. The system houses a complex, time-dependent vortex structure, which leads to constantly changing positions of the vortex core. In the optimization of computation times, an ongoing adaption of the mesh size is carried out. This results in a particularly good mesh density in areas with a high velocity gradient and the free surface.
Figure: left: schematic representation of the gravitation water vortex power plant, right: velocity profile with representation of the mesh refinement in areas with a large velocity gradients and the free surface.