__This isssue has been split into #839 #838 #837 and will be closed.__ There is a myriad of benchmarks, numerical and analytical solutions for free-flow problems. We should incorporate more of them in our free-flow tests. Thomas and Christoph had some of them for their staggered grid implementation. Currently, there are two test which come with an analytical solution: `test_donea` and `test_kovasznay` Here a some ideas what could be added: - [ ] Analytical solution for simple stationary 2d channel test (test already exists) - [ ] [Ghia 1982](https://ac.els-cdn.com/0021999182900584/1-s2.0-0021999182900584-main.pdf?_tid=e9f7486c-d67c-11e7-96b6-00000aab0f26&acdnat=1512121945_6871c2de3e7d5699f53ef718416dc341) - [x] Transient flow field test with analytical solution - [ ] Transient flow field test: lid driven cavity - [ ] Analytical solution for diffusion (mass/energy) tests - [x] Ensure same results for mass and mole formulation (see !950) More suggestions welcome! - [ ] Improve the description of the tests and the help-message Could be a job for a HiWi.