with the adoption by environmental scientists of cfd models there is a need for a book outlining cfd theory in a manner relevant to environmental applications that is accessible to those who have not done mathematics or physics as a first degree. part one will address the basic topics in cfd modelling in a thematic manner to provided the necessary theoretical background. part two will include global cases studies showing how cfd models can be used in practice demonstrating how good practice can be achieved , with reference to both established and new applications.