Closure

Three fringe thinning algorithms based on a search for minimum intensity, curve fitting and the paintbrush option available on PCs have  been compared in the context of tomographic inversion. The main conclusions that have been drawn from the present study are: 

1. The three methods  of fringe thinning produce qualitatively similar temperature fields.
2. Quantitative analysis shows differences in the results, but large errors are localized and over 95% of the fluid region, errors are smaller the 1%.
3. The loss of a wall fringe during the automatic fringe thinning does not increase errors  either in the reconstructed temperature field or the Nusselt number. 
4. The automatic fringe thinning algorithm requires the most code preparation time. It is however superior to the other two methods since it is repeatable and takes the minimum computer time for execution. It is also physical meaningful since it closely satisfies the energy balance criterion.