(Double Click) Setup in "Unsteady Flow", the duplicate project. Select Double Precision, and if using a computer with multiple cores, select parallel, and set the number of cores to be used.
Then click OK
In this step here we will, tell FLUENT to solve for the unsteady flow. As you can see, by default FLUENT will solve for the steady flow.
Problem Setup > General. Set Time to Transient.
Specify Material Properties
To achieve a Reynolds number of 120, as required in the problem statement, we will change the material viscosity, to 8.333*10^-3 kg/m*s.
Problem Setup > Materials > Fluid > air > Create/Edit.... Set the viscosity to 8.333E-3 (kg/m*s). Click Change/Create.
Then click Close.