In experiments using (1) a/an/θ/the wind tunnel, it is necessary to put (2) a/an/θ/the model into freestream region. i.e the region which has no influence of (3) a/an/θ/the wall effect on the model. The influence of it can (4) generate/generates/generating/ generated reading errors to the characteristics of flow for the model.
Nuno and Anthoine [1] stated that the maximum allowable size of the model to be put into the test section of the wind tunnel d/D ≈ 3%, where d is the model diameter and D is the wind tunnel width. With that size, it is (5) expected/expects/ expect/expecting that the effect of wall on the model can be (6) neglected/ neglects/ neglect/ neglecting. Practically, the value of d/D < 3% (7) is/are/was/were difficult to be applied, due to limitation of the wind tunnel’s size. As an example, during the experiment performed in the fluid mechanics laboratory at the Mechanical Engineering Department in ITS, the maximum ratio was more than 3%. These facts due to the limitation of the size of the test section.
The objective of this research was to find the appropriate ratio between model and the wind tunnel test section’s size without significant wall effect. The research (8) was/were/is/are done by putting the cylinder in the test section of the wind tunnel, and varying the ratio d/D = 3,79%, 9,09%, 21,21%, 25%, 32,73%. By study the effect of the variation d/D to the characteristics of the fluid flow (velocity and pressure) passing the cylinder, the indication of the blockage effect phenomenon was found. Besides varying the diameter of the model, the study was also varying the Reynolds numbers.
The experimental results and visualisation (9) show/shows/showing/showed that no significant influence of the wall effect at d/D < 9,09%. On the contrary the wall effect (10) become/becomes/became/ becomed more important at d/D > 21,21%.
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