Ongoing projects

Slurry flows : Literature survey

A state of the art of slurry flows has been performed by the von Karman Institute. This study focused on slurries with solid particles in liquid, but also solid particles in gas in the case of fluidized bed. The study focused on the typical industrial areas where slurries are encountered; going from pipelines to pharmaceutical or food processing industry, showing emerging domains like phase change slurries or ice slurries. The study also investigated and compared correlations to model transitional velocities between flow regimes, pressure losses or the slurry viscosity. Finally, the study made an inventory or existing measurement techniques for particle size distribution, pressure loss, viscosity, flow rate, or liquid and solid velocities. For each measurement area, the different techniques were detailed and compared.

Experimental Characterization of Straw Jets using PIV

This study will experimentaly investigate the flow pattern in the chute of a straw blower machine using Particle Image Velocimetry (PIV). A test section identical to the industrial chute will be built in transparent material and will be sent to CETIM to be mounted on an actual straw blower machine. The measurements will focus on three vertical sections of the chute, locate on the central axis; the firs at the entrance of the chute, the second in the middle and the last at the chute exit. These three section will be measured for two rotating speeds and three obstructions of the entrance which will simulate the straw accumulation at different moments.

Prediction of low-speed fan trailing-edge noise based on RANS and on scale resolved simulations

This work compares the prediction of the broadband trailing-edge noise emitted by a four-bladed low-speed ventilation fan obtained with different computational approaches. The objective of each approach is to compute the spectrum of the wall pressure fluctuations close to the trailing-edge, which is an input to Amiet's theory for the computation of the far field noise spectrum. The wall pressure spectrum can be computed by applying Panton and Linebarger's theory to boundary layer data extracted from a time-averaged simulation, or it can be obtained directly by frequency analysis of a scale resolved simulation. The results of both kinds of computation are compared with the measurements taken on the same fan. A better correspondence with the experimental data has been obtained by using a Scale Adaptive Simulation (SAS) rather than a RANS flow solution.

Far field sound power level spectra, third octave average

Far field sound power level spectra, third octave average

Past projects

Experimental Investigation of Cavitation in a Safety Relief Valve

This study focused on the investigation of cavitation and its main consequence in the normal operation of a safety relief valve. The experiments were performed on the BECASSINE facility using a transparent model based on API 1 1/2G3 valve. Precise optical measurement techniques were applied to locally characterize the flow topology during cavitation.

High speed visualization allowed to qualitatively observe the flow pattern and the inception of liquid vaporization. Particle tracking suggest the vapor bubbles are formed in the core of vortices detached from the shear layers attached to the valve. These structures promote low pressure region allowing liquid vaporization.

High speed visualization of a cavitating flow in a SRV

Particle Image Velocimetry (PIV) technique was also applied to extract velocity fields in single phase and cavitating flow conditions. PIV confirms the existence of a submerged jet downstream the minimum section characterized by two non symmetric shear layers at its sides.

Example of velocity fields obtained by Particle Image Velocimetry

REFERENCE:
Jorge Pinho, Experimental Investigation of Cavitation in a Safety Relief Valve using water. Extension to Cryogenic Fluids, PhD Thesis, Université Libre de Bruxelles, Ecole Polytechnique de Bruxelles / von Karman Institute for Fluid Dynamics, 27 April 2015, ISBN 978-2-87516-089-8 - Thesis available on demand at This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Experimental Characterization of Straw Jets

This study used a non-intrusive experimental technique to characterize the dense particle laden jet flow produced by straw blowers machine. The experimental set up consists of a straw blower machine, a white background tarp and a color video camera filming the straw jet over a twelve meter test section, in daylight conditions. The technique is based on an image processing routine to detect and track straw particles from the video sequence. In particular, the processing combines two segmentation techniques: 1) a color segmentation, using k-means clustering in the CIElab color space and 2) an adaptive background subtraction, using Eigen-Background decomposition. For a set of four test cases, the straw jet trajectories obtained were complemented –and validated– with the measurement of straw distribution at the ground using a mesh of panels.

A typical snapshot image of straw jets

RGB (a), HSV (b) and Lab (c) representation of the image snapshot in Fig.3, and spatial definition of their components.

Final straw detection

REFERENCE
Miguel Alfonso Mendez and Jean-Marie Buchlin, Experimental Characterization of Straw Jets via Image Processing Techniques, 10th Pacific Symposium on Flow Visualization and Image Processing, Naples, Italy, 15-18 June, 2015