I solve structured grid volume arround sphere using navier stocks equations , it exact the same flow paths like those produced from fluent, when i calculate the drag coeffecient, it always gives different values for different sphere diminsion, i use pressure*area integration arround all ponits of sphere border to get the drag force, but i always get wrong value of Cd (1.3-->4.9), any one can tell me the reason and how to detect the problem in my code?

1. Include viscous drag in your calculation

2. Cd will change with Re which in changing when you change the dimensions.

-- Jarmo

Can you please give me a valid fromula to calulate the prssure and viscuse terms in the drag force. i want to be sure of my equations?

Pressure drag - pressure * area Viscous - viscosity * du/dn * area

Or something along those lines. Any fluids book should have this.

-- Jarmo

hi ! Even i am writing a code for Cd but it is around a cylinder. Please help me in grid discritization as i am mesing up th grid thts why i got errors. Please give me links or method of grid u used so tht I can have an idea for a cylinder

Thanks ANy help will be appreciated

actually i use a structured gride "cubes" arround the sphere, it is more simple for calculation, put untill now i fail to get an accurate value for Cd