Learning Forum

[Akankhya Patro]

I want to find drag coefficent of a sphere for reynlod no. 1000000.As reynold vary with velocity so in order to calculate what velocity should be in the inlet I need to use characterstics length of the fluid but I am unable to understand what should be the characterstics length for box cfd domain

[SRP]

Hi,

 For a sphere, the characteristic length is typically the sphere diameter. In general, the characteristic length can vary depending on the geometry of the domain. For a box-shaped CFD domain, the characteristic length can depend on the particular flow problem you are studying. Some possible choices for the characteristic length of a box-shaped domain could be: The length of the box along the direction of the flow. The hydraulic diameter of the box (a measure of the effective diameter of a non-circular cross-section).

Thank  you.