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Computational Investigation of Flow Development Through 22.5°/22.5° Sigmoid Diffuser

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In the present investigation the distribution of mean velocity, turbulence intensity, static pressure and total pressure are experimentally studied on a Sigmoid Diffuser of 22.5°/22.5 angle of turn with an area ratio of 1.5 aspect ratio 3.75 keeping inlet width 50 mm with centre line length 450 mm. The experimental results then were numerically validated with the help of Fluent. The velocity distribution shows that generation of secondary motion in the form of counter rotating vortices within the 1st half of the diffuser.  The secondary motion changes their sence of rotation after the inflexion plane of the test diffuser. The maximum values of the mass average static Pressure recovery and total pressure loss are 38% and 12% compared to the predicted results of 41% and 9% respectively, which shows a good agreement between the experimental and predicted results.
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Sigmoid Diffuser; k-ε Model; Fluent Solver; Five-Hole Probe

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