The default material properties for air need to be changed so that it now has a density of 1.205 kg/m^3 and a dynamic viscosity of 1.81e-5 PaS.
- Select the Air > Models > Gas > Air > Material Properties > Density> Constant node.

- In the Properties window, set the Value property to
1.205 kg/m^3.

- Still within the Air node, open the Dynamic Viscosity node and select the Constant node
- Set the Value property to
1.81e-5 Pa-s.