The study of the two test cases proposed by JAXA on the cooperative research on cryogenic fluid behavior between JAXA and CNES is the aim of this work. Gambit and Fluent v6.3 with User Defined Functions (UDF) are the computational software picked in order to obtain the requested outputs for each test case. In order to validate the simulation software used, two similar test cases previously performed by CNES from the benchmark of 2010 with an older version of the software have been tested with Fluent v6.3. These test cases are TC1: Liquid surface in low gravity and TC2: Isothermal sloshing. Once the results obtained with the newest software version are equal to the ones obtained with the oldest, then the solver is validated. The objective of the present work is to study the test cases proposed. They are TC4: Liquid surface in low gravity and TC5: Isothermal sloshing. The first case (TC4) studies the interaction between the walls and the liquid on microgravity conditions. By the contrary, the test case TC5 studies the dynamic of the liquid inside a tank after applying a lateral acceleration to the whole system.