Abstract
The visualization technique presented herein is based on white light differential interferometry using large Wollaston biprisms. The particularity of our set-up is that it yields two instantaneous interferograms, taken at precisely the same time, on which the interference fringes are differently oriented. Thus, the instantaneous fields of two different partial derivatives of density are simultaneously recorded and it is possible, through the use of both interferograms, to obtain the value of the density in domains where this cannot be done using a single interferogram. This method has been successfully tested in the two-dimensional unsteady flow past a cylinder.
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Abbreviations
- d :
-
diameter of the cylinder
- Oxy :
-
Cartesian reference system
- t :
-
time
- M ∞ :
-
upstream Mach number
- ϱ :
-
gas density
- P :
-
pressure
- δP :
-
pressure fluctuation
- N :
-
vortex street frequency
- ɛ :
-
birefringence angle
- Π :
-
double-prism median plane
- ξ :
-
biprism abscissa corresponding to any colour
- ξ 0 :
-
biprism abscissa corresponding to the background colour
- E :
-
optical thickness
- E e :
-
optical thickness corresponding to the background colour
- dE :
-
difference of optical thickness
- θ x :
-
deviation angle of light rays along Ox
- θ y :
-
deviation angle of light rays along Oy
- D :
-
diameter of the spherical mirror
- R :
-
radius of curvature of the spherical mirror
- L :
-
virtual distance from the middle of the test section to the spherical mirror
- T :
-
time between the trigger and the recording of interferograms
References
Desse, J. M. 1990: Instantaneous density measurement in two dimensional gas flow by high speed differential interferometry. Exp. Fluids 9, 85–91
Francon, M.; Sergent, B. 1955: Compensateur biréfringent à grand champ. Opt. Acta 182–184
Gontier, G. 1957: Contribution à l'étude de l'interférométrie différentielle à biprisme de Wollaston. Pub. Scien. et Tech. du Ministère de l'Air
Ishii, K., Kuwahara, K. 1984: Computation of compressible flow around a circular cylinder. AIAA Paper
Rodriguez, O. 1984: The circular cylinder in subsonic and transonic flow. AIAA J. 22, 1713–1718
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Desse, J.M., Pegneaux, J.C. Whole-field measurement of gas density from two simultaneously recorded interferograms. Experiments in Fluids 12, 1–9 (1991). https://doi.org/10.1007/BF00226559
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DOI: https://doi.org/10.1007/BF00226559