The performance of a fish guiding device located just upstream a hydropower plant is scrutinized. The device is designed to redirect surface orientated down-stream migrating fish (smolts) away from the turbines towards a spillway that act as a relatively safe fishway. Particles are added up-stream the device and the fraction particles going to the spillway is measured. A two-frame Particle Tracking Velocimetry algorithm is used to derive the velocity field of the water. The experimental results are compared to simulations with CFD. If the smolts move passively as the particles used in the study the guiding device works very well and some modifications may optimize its performance. In-field Particle Tracking Velocimetry is a suitable technique for the current case and the results compare well with numerical simulations.

Microparticle image velocimetry (μPIV) is used to measure the grease velocity profile in small seal-like geometries and the radial migration of contaminant particles is predicted. In the first part, the influence of shaft speed, grease type, and temperatures on the flow of lubricating greases in a narrow double restriction sealing pocket is evaluated. Such geometries can be found in, for example, labyrinth-type seals. In a wide pocket the velocity profile is one-dimensional and the Herschel-Bulkley model is used. In a narrow pocket, it is shown by the experimental results that the side walls have a significant influence on the grease flow, implying that the grease velocity profile is two-dimensional. In this area, a single empirical grease parameter for the rheology is sufficient to describe the velocity profile.In the second part, the radial migration of contaminant particles through the grease is evaluated. Centrifugal forces acting on a solid spherical particle are calculated from the grease velocity profile. Consequently, particles migrate to a larger radius and finally settle when the grease viscosity becomes large due to the low shear rate. This behavior is important for the sealing function of the grease in the pocket and relubrication

The flow dynamics of a lubrication mechanism is very complex, much due to the complex rheology and composition of the grease. In order to obtain an optimal lubrication, both the initial amount of grease and the position of the grease is highly important as too much grease will contribute to an increased friction, and grease in the wrong place will negatively affect the replenishment through oil bleeding. To understand the flow dynamics of grease hence is highly important for the understanding of the lubrication mechanism. Using micro Particle Image Velocimetry (μPIV) we have in a series of studies investigated the dynamics of grease flow in 2D straight channels with- and without restrictions, and in a full 3D configuration comprising a double restriction seal geometry. Velocity profiles for greases of different thickness have been measured, showing the influence of the grease rheology on the grease flow behaviour. KEYWORDS: Lubricants:Greases, Lubricant Physical Analysis:Non-Newtonian Behavior, Lubricant Physical Analysis:Rheology.

Grease is commonly used to lubricate various machine components such as rolling bearings and seals. In this paper the flow of lubricating grease passing restrictions is described. Such flow occurs in rolling bearings during relubrication events where the grease is flowing in the transverse (axial) direction through the bearing and is hindered by guide rings, flanges et cetera, as well as in seals where transverse flow occurs, for example during so-called breathing caused by temperature fluctuations in the bearing. This study uses a 2D flow model geometry consisting of a wide channel with rectangular cross-section and two different types of restrictions to measure the grease velocity vector field, using the method of Micro Particle Image Velocimetry. In the case of a single restriction, the horizontal distance required for the velocity profile to fully develop is approximately the same as the height of the channel. In the corner before and after the restriction, the velocities are very low and part of the grease is stationary. For the channel with two flow restrictions, this effect is even more pronounced in the “pocket” between the restrictions. Clearly, a large part of the grease is not moving. This condition particularly applies to the cases with a low-pressure drop and where high consistency grease is used. In practice this means that grease is not replaced in such “corners” and that some aged/contaminated grease will remain in seal pockets.

A new method to visualize and quantify grease flow in between two sealing lips or, in general, a double restriction seal is presented. Two setups were designed to mimic different types of seals; that is, a radial and an axial shaft seal. The flow of the grease inside and in between the sealing restrictions was measured using microparticle image velocimetry. The results show that grease flow due to a pressure difference mainly takes place close to the rotating shaft surface with an exponentially decaying velocity profile in the radial direction. Consequently, contaminants may be captured in the stationary grease at the outer radius, which explains the sealing function of the grease.

The flow field inside and downstream of an open channel placed near the surface of a free flow (such as the tail water of a turbine) is characterized in detail. The channel cross-section is U-shaped and in the downstream end is placed a ramp on the bottom which accelerates the flow passing through the channel. This flow is intended to catch the attention of fish and improve their entrance to fishways, which has also been successfully demonstrated in field tests.

The flow field inside and downstream of an open channel placed near the surface of a free flow (such as the tail water of a turbine) is characterized in detail. The channel cross-section is U-shaped and in the downstream end is placed a ramp on the bottom which accelerates the flow passing through the channel. This flow is intended to catch the attention of fish and improve their entrance to fishways, which has also been successfully demonstrated in field tests.The flow through the channel is subcritical and the ramp thus blocks some water from passing through. To find the optimum vertical position of the channel, a down-scaled model channel is placed in a water flume and flow fields in vertical planes directed along the flow are visualized using particle image velocimetry. Results show that increasing the depth over the ramp has little effect on the maximum velocity while it makes the accelerated water more perceptible downstream the channel. This will most likely improve the channel's ability to attract fish. It is also shown that a recirculation zone is formed in the channel for the small depths tested. Finally, it is shown that a modest tilt of the channel will not affect the flow field in any significant way.

Experimental fluid mechanics has for a long time been used to visualize flow phenomenonqualitatively. Traditionally, visualization has been done with dye or tracer particle dueto their ability to follow the flow pattern well. One of the early pioneers in experimentalfluid mechanics was Ludwig Prandtl who used mica particles in water flumes to accuratelydescribe the flow around wing profiles. Due to Prandtl’s results in the early 20thcentury, some of the most important theories in aviation were founded. By combiningPrandtl’s attempt to trace particles, and contemporary laser and computer technologiesa quantitative non-intrusive whole field technique, so called Particle Image Velocimetry(PIV), has been developed. The PIV technique has through the advances in computerscience the recent decades, been improved significantly and has also grown in popularityamong the scientific- and technological community.This thesis describes implementation of PIV in several diverse research areas frommacro- to micro scale. First, it is described how PIV is used as a pure measurementtechnique to understand complex flow phenomena. The technique is demonstrated on asmall U-shaped channel designed to facilitate salmonoid like fishes upstream migrationto their spawning grounds. Second, PIV is used as a validation tool for ComputationalFluid Dynamics, CFD. In the current situation, CFD is undergoing a generation shiftfrom Reynolds Averaged Numerical Simulation, RANS, to Large Eddy Simulations, LES.This is for instance motivated by energy production units which has many applicationswith high turbulence and temperature fluctuations. Hence it is desirable to be able toestimate the impact on thermal loads on the materials inside the plant (e.g. the pipewalls). An LES approach is superior to applying to RANS since the large eddies areresolved. However, LES is still not mature enough to be used without validation incritical applications. Therefore, PIV has been used to create a validation database fora generic T-junction. Finally, a description of how PIV technique can be adopted tostudy the flow of complex fluids in small geometries by means of microscopy, is given andapplied on lubrication grease flow in labyrinth seals which have been used in bearingsand other lubricated applications since the 1940’s. The intention with labyrinth seals isto lubricate the bearing and prevent contamination from entering the rolling elements.Although it is widely applied, little is known about the actual function and mechanismof labyrinth seals. To learn more about the flow and particle migration within a sealgeometry, a new method to visualize and quantify grease flow within a labyrinth seal hasbeen developed based upon micro-PIV.