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Postdoctoral Position in Fluid Dynamics of Hydropower Transients

Chalmers University of Technology is pleased to invite applicants to apply for a postdoctoral researcher position in mechanical engineering. The funds for this fellowship are available for three years. Applicants should apply before November 18, 2018.

The department of Mechanics and Maritime Sciences (M2) conducts fundamental and applied research to achieve sustainable technological solutions. M2 holds one of Sweden's most extensive simulator centre for navigation and propulsion of ships, as well as world class laboratories within combustion engineering and wind tunnels. The department also offers and contributes to bachelor and master programs in areas such as Shipping, Automotive and Mechanical Engineering to mention a few. In addition, professional education is performed on both a national and international level, with specific designed mission training for different social actors, within our ambition for a lifelong learning. The department continuously strives to establish a cooperation between academia, industry, and society, with a great focus on utilization. M2 is characterized by an international environment with employees and students from around the world, as well as outstanding research and world class education. M2 consists of seven divisions within the areas of engineering and maritime sciences, and one division of administration and support.The present position is at the division of Fluid Dynamics.

Information about the division of Fluid Dynamics

Our mission is to gain fundamental knowledge about turbulent incompressible and compressible flows through numerical and experimental research, and develop new and improved computational and experimental techniques for the study of such flows in both fundamental and real-world environments. We also aim to assist industrial researchers and engineers in confronting problems involving turbulent and compressible phenomena.

The research at the Division covers turbulent flow (both compressible and incompressible), aero-acoustics and turbomachines. Our tools include both computations and experiments. The research covers a wide range of topics. In some research projects the smallest turbulent scales are studied whereas in others the function of a complete gas turbine is analyzed and modelled.

Our applied research is carried out in close cooperation with industry, both in national projects and in EU projects. Vehicles (cars, trucks, busses and trains), airplanes, gas turbines, water and wind turbines are important applications. The Division of Fluid Dynamics is part of Chalmers Sustainable Transport Initiative, Chalmers eScience Initiative and Chalmers Energy Initiative.

A large part of our teaching activity is carried out within our International Master Program in Applied Mechanics. In this program we offer courses covering a wide range of courses, including turbulence modelling, experimental fluid dynamics, CFD, heat transfer, turbomachinery and gas turbine technology.

Project background

Due to the new intermittent electric energy sources, hydropower is forced to run more and more at off-design conditions and to regulate the operating conditions. This causes flow instabilities with pressure fluctuations, and load variations that may deteriorate the machine. We have previously assessed state-of-the-art unsteady turbulence modeling (URANS, PANS, hybrid models and LES) for the use in hydro power applications under steady operating conditions. We have shown that it is possible to accurately predict the unsteady flow features under such conditions. The next step is to include the transients when continuously regulating the electric grid, when changing from one operating condition to another, during start-up/shut-down, or at a sudden load rejection. Another situation is when the turbines are running at speed no-load, ready to connect to the electric grid at very short notice. Numerical simulations of such situations require further research on turbulence modeling, wall functions, and coupling to the entire hydraulic system. In most cases the transients involve changes in blade angles that must be taken into account. That requires developments in mesh generation, mesh morphing, special treatment of small gaps, mapping of intermediate results, etc.

The numerical results will help gaining new knowledge on the flow physics during unsteady flow and transients in hydraulic turbines. The unsteady forces on the machine may be predicted and their origin may be understood. Such knowledge is beneficial for an expanded knowledge of the rotor dynamics of the machines. It is increasingly important to investigate the dynamic loads and transient response of new, refurbished and existing turbines and its impact on the rotating system which often results in strong vibrations with increased wear and decreased lifetime as consequence. Eventually, a coupling between rotor dynamic models and efficient unsteady flow modeling may be accomplished. With increasing demands on turbine flexibility the parameters that lead to damage from vibrations and dynamic load variations need to be investigated. To answer these questions new and improved computational tools are needed.

Special notes regarding the project

It should be recognized by anyone applying for the position that this is applied research, which to a very large extent depends on methods that are needed for the feasibility of the studies. Those methods need to be developed during the initial part of the project. There are already some implementations available, but they are far from ready to just use for the present application. Once those methods are working for the present kind of applications the project opens up for more detailed studies of the turbulent flow. Still, such simulations will be very challenging, not the least due to inherent practical problems related to mesh rotation and deformation.

Major responsibilities

Develop, in OpenFOAM, the required methods that are needed to study transients in hydro turbines. That particularly/initially involves the simultaneous mesh deformation due to guide vanes that change their angle at the same time as a part of the computatinal domain is rotating. Once the methods are working efficiently they should be used to do in-depth studies of the turbulent flow features encountered during transient operation of hydraulic turbines.

Your major responsibility as postdoc is to perform your own research in a research group. The position may also include teaching on undergraduate and master’s levels as well as supervising master’s and/or PhD students to a certain extent. Another important aspect involves collaboration within academia and with society at large. The position is meritorious for future research duties within academia as well as industry/the public sector.

Full-time temporary employment. The position is divided into 1+1 years, where the second year may be started after successful completion of the first year.

Qualifications

To qualify for the present post-doc position you must have a doctoral degree in Computational Fluid Dynamics or relevant field; the degree should generally not be older than three years. You are expected to be somewhat accustomed to teaching, and to demonstrate good potential within research and education.

Mandatory experiences and skills

In-depth knowledge of the underlying methods used in CFD and turbulence modelling. Experiences in programming of CFD codes, and in particular C++ and OpenFOAM.

Meritorious experiences and skills

Experience with methods that are useful for the simultaneous motion of guide vanes and runner rotation in hydraulic turbines, such as mesh morphing, overset mesh, immersed boundary etc. The project depends on a successful treatment of this combined mesh motion, which needs to be developed in the very initial part of the project. Anyone applying for the position should be confident that this will be feasible. Having those methods in place, experience in highly resolved simulations of turbulent flow is beneficial for the actual studies of the transients. Experience in CFD simulations in rotating machinery, or at least an understanding of the practical problems related to highly resolved CFD in rotating machinery, is highly beneficial.

Personal qualities

We are looking for a candidate that has a strong numerical analytic ability and a well-developed problem solving ability. Furthermore the candidate we are looking for has a strong internal motivation and is self-propelled. Since we work in an multi-cultural environment it is important to be able to communicate well with people from different backgrounds.

The position requires sound verbal and written communication skills in English. Chalmers offers Swedish courses.

Chalmers offers a cultivating and inspiring working environment in the dynamic city ofGothenburg.

Read more aboutworking at Chalmersand ourbenefitsfor employees.

Application procedure

The application should be marked with Ref 20180565 and written in English.

CV: (Please name the document as: CV, Surname, Ref.

CV, including complete list of publications

Previous teaching and pedagogical experiences

Two references that we can contact.

Personal letter:(Please name the document as: Personal letter, Family name, Ref.

1-3 pages where you introduce yourselfand present your qualifications.

Previous research fields and main research results.

Future goals and research focus. Are there any specific projects and research issues you are primarily interested in?

Attested copies of completed education, grades and other certificates.

Application deadline: 18 November, 2018

Professor Hkan Nilsson, Fluid Dynamics, hakan.nilsson@chalmers.se,+46 31-772 1414


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