Research projects

 

 

 

Investigation of a radial blade cascade subject to forced excitation: Fluid structure interactions

 

The current project is academic research project aimed at fundamental research in the field of fluid structure interactions. The research work is conducted by a doctoral researcher, Gabriele Gaiti. The project scheduled for three years starting from August 2021.

Turbine resonance and fatigue are critical challenges in hydropower. Water being highly dense fluid induce complex characteristics and modes of vibrations. The characteristics are transient in nature therefore challenging to correlate with the prototype conditions.

In order to understand the complexity, understanding on interaction of the water and the blades is highly important at the fundamental level. More specifically, how every exchange takes place.
The research focuses on simplified test-case of blades. The isolated environment will help us to understand how blade and water interact and what happens in the blade channel during the resonance.

BLADE CASCADE

A radial blade cascade is designed and manufactured for the experimental and numerical investigations. Several blades of symmetric profile will be integrated.

Initially, pressure, strain and particle image velocimetry measurements are proposed to study overall performance characteristics of the blades with respect to the Reynolds numbers, the important aspect is to find out resonance velocity with respect to vortex shedding.

During the next phase of measurements, the blade will be energized using piezoelectric mussels. This will create resonance in the blade, which will influence the water in radial direction and response on another blade will be studied.

test section of blade cascade

Research question 1

How turbine blades react during resonance?

Research question 2

What is role of fluid added damping during the resonance?

Research question 3

Can we reduce resonance using damping as manipulating parameter?

 

 

Project goal

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test site

 

 

Investigation of a Francis turbine during start-stop


OBJECTIVES

  • Credible verification and validation
  • Study inception of passage vortex
  • Study trajectory of vortex
  • Study transition from large eddy vortex to stochastic vortex at the runner outlet
  • Study high energy stochastic eddies

 

guide vane vortex les

gas turbine

Hydrofoil dns simulation

Fabian Camillo Eitzen


Large eddy simulations

Turbine startup and shutdown are complex situation of a turbine, where flow inside the turbine becomes extremely chaotic. More importantly, the blade loading, and unloading is transient in nature therefore, sophisticated start-stop procedure is needed to optimize the fatigue load on the blades. For smooth blade loading and unloading, understanding of flow field inside the turbine is extremely important.

This student project aims to study flow field inside the turbine during the shutdown process. This can be achieved through computational fluid dynamic (CFD) techniques. The Francis type hydraulic turbine is proposed to model numerically. Investigate flow field with specific emphasize on blade loading, rotor stator interaction, vorticity, pressure amplitudes, frequencies, stochastic loading using one selected rate of guide vane opening and closing.

Investigation of pressurized and free-surface type sand trap of hydroelectric power plant


OBJECTIVES

  • Credible verification and validation
  • Study inception of passage vortex
  • Study trajectory of vortex
  • Study transition from large eddy vortex to stochastic vortex at the runner outlet
  • Study high energy stochastic eddies

 

guide vane vortex les

Hydrofoil dns simulation

Fredrik Joakim Daving


Three-phase simulations

Several large hydropower plants in Norway have been upgraded with a higher installed capacity, however, this has resulted in certain operational challenges associated with sediments entering the penstock and causing wear to the hydro turbine. One of the reasons may be a limitation in the sand trap that may not function as anticipated after the refurbishment.

Prepare a flat sand trap, at least for the initial 100 m. Investigate both free-surface and pressurized flow with positive inclination, negative inclination and flat bottom.

Aim for modelling of three-phases, i.e., air, water and sand. Investigate turbulence length scale and determine refinements of mesh for resolving small turbulent eddies.

Develop an optimization model/parameters of free-surface sand trap, including flow calming structure and ribs. This will create a strong foundation for the future research of generic sand trap and can be optimized for a hydroelectric power plant.

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