| 1. |
- Johansson, Bert, et al.
(författare)
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Application of wedge-shaped hot-film probes in a gas-particle flow
- 2003
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Ingår i: Experimental Thermal and Fluid Science. - 0894-1777. ; 27:2, s. 187-191
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Tidskriftsartikel (refereegranskat)abstract
- A wedge-shaped hot-film probe is used to perform measurements of turbulence intensity and an estimate of the turbulent kinetic energy as well as the Eulerian spectra, macro- and micro-scales of the gas phase in a horizontal pipe flow carrying pulp fibres or spherical particles. In addition, the paper gives a summary of a method for handling the poor frequency response of the probe and discusses how to sort out "bad samples", occurring when the probe is hit by particles.
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| 3. |
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| 4. |
- Ljus, Camilla, 1971
(författare)
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On Particle Transport and Turbulence Modification in Air-Particle Flows
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The transport of particles by airflow was studied for two different flow cases, the transport of pulp fibres in a mat-forming process and the transport of pulp fibres and spherical particles in a horizontal pipe. The transport of pulp fibres in the mat-forming process is first considered. Numerical calculations are made of the air-fibre flow through the forming head using an Eulerian two-fluid model. The calculations show that the flow field is governed mainly by the boundary conditions, which are rather complicated for the transport channel and forming head of the mat-forming device. Measurements of velocity and pressure are performed and used to verify the numerical results. To be able to measure turbulence in a dilute air-particle suspension, a measuring method is developed that uses a wedge-shaped hot-film probe in airflow. The poor frequency response of a wedge-shaped probe in airflow normally makes it necessary to make a dynamic calibration. To avoid this, a method that uses a correction function applied to the turbulent spectrum is developed and tested in a fully developed pipe flow. The second flow case investigated is the transport of pulp fibres and spherical particles through a horizontal pipe. Measurements of turbulence modification are made. The results show that the turbulence is damped close to the wall and enhanced in the centre region of the channel by the spherical (450 .my.m) particles. For the pulp fibres, the turbulence is damped over the entire cross section. Calculations are made of the transport of particles in a horizontal channel. The two-fluid model is extended to take into account turbulence, and a model for the turbulent dispersion of particles is suggested. The gas phase turbulence is calculated using a modified k-.epsilon. model that takes into account the influence of particles, both additional dissipation and additional production, on gas phase turbulence. The calculated results agree qualitatively with the experimental results for the horizontal pipe.
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| 5. |
- Ljus, Camilla, et al.
(författare)
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Turbulence modification by particles in a horizontal pipe flow
- 2002
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Ingår i: International Journal of Multiphase Flow. - 0301-9322. ; 28:7, s. 1075-1090
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Tidskriftsartikel (refereegranskat)abstract
- Measurements were made of turbulence intensities and turbulent energy spectra in a fully developed, turbulent air-particle pipe flow. The influence of the particles on the turbulence was studied. Measurements were made with spherical particles and particles with a large aspect ratio (pulp fibres). There is a significant change in turbulence intensity at higher particle concentrations with loading ratios of m = 0.1 and 0.03. The measurements show that the turbulence intensity increases close to the centre of the pipe while the turbulence intensity decreases close to the pipe wall for the spherical particles. These results are in agreement with earlier measurements found in the literature. For the fibres, the turbulence intensity decreases over the whole pipe cross-section. Fibre flocs, however, give variations in the mean velocity that result in the production of turbulence in the lower part of the channel.
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| 6. |
- Löfdahl, Lennart, 1948, et al.
(författare)
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A Fast Simple Hot-Wire Method of Determining the Mean Velocity Vector of Complex Three-Dimensional Flows
- 1996
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Ingår i: Experiments in Fluids. ; 20, s. 398-400
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Tidskriftsartikel (refereegranskat)abstract
- A fast and simple method of determining the mean velocity vector of complex three-dimensional flow fields is outlined. Straight and slanted single hot-wires are rotated in two perpendicular planes. This method increases the angular resolution, which is of importance in flow situations where one of the velocity components dominates and the other changes rapidly from one point to another. The method was calibrated in a wind tunnel and assessed in the internal flow field at the outlet of a fan in a defroster channel. It is shown that the hot-wire method yields good agreement with corresponding flow visualizations determined using a textile thread, and an integration of the measured mean flow yields a flow rate which agrees within a few percent with corresponding direct measurements on an orifice plate.
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