Various publications in the past as well as more recent works have dealt with the validation of wet steam models. If the literature is read carefully, an interesting situation has persisted for almost 20 years. In this period the increase in available computational power has been used to realise impressive wet steam calculations of multi-stage turbines while, in our opinion, only small improvements in the reliability and confidence of wet steam modelling have been achieved.

It is well known that wet steam models and numerical schemes are not free from uncertainties. On the other hand, the accuracy of the available wetness measurements is also uncertain. Often there is not enough information about the experimental and numerical setup available, which makes the situation even worse. Currently most researchers accept that they are able to get a more or less good agreement between their numerical predictions and experimental data. Authors sometimes quote plausible reasons for the discrepancy, and some are brave enough to speculate, but almost no work can be found that investigates the existing shortcomings in further detail.

One of the main conclusions of the Baumann Centenary Conference held in Cambridge in the year 2012 was that more experimental data are needed to improve wet steam modelling. It is encouraging to see that some experimental work is currently in progress. We think that in the meantime some combined effort should be undertaken to examine the current state of wet steam modelling. We would like to initiate a joint validation project where calculations performed by different people, institutions, and companies are compared to each other. In order to make the numerical results more comparable we will provide the numerical grids for some famous test cases. Each participant will have the opportunity to run the calculations with their particular numerical method and settings and finally we will bring the results together in a paper. The objective of this project is to determine the strengths and weaknesses of wet steam modelling and to clarify the influence of different numerical setups and assumptions. We believe this will be a good starting point for further developments and may provide some wet steam modelling guidelines.