Hi
I've been working with FloWorks for about ½ a year now. For the purpose of gettin' to know the program, I've done some external simulations on a sphere of 6mm diameter.
Fluid = Air (SW defined) Fluidvelocity = 80 m/s
The drag force Fd on a sphere can be calculated by Fd = 1/2*Cd*A*rho*v^2
where Cd = Drag Coefficient (aprox. constant when Reynolds number Re>1000) I've used Cd = 0.47 A = crosssectional area normal to flow direction. rho = density of fluid. v = velocity of fluid relative to the sphere.
The difference between the CFD and the "calculated" values are minimal.
THE QUESTION!!! (aye, that's right...I'm actually gettin' to it)
To get the drag force in FloWorks, I take a "Surface Parameters" on the sphere's surface (all of it). Of cause I only need the component that points in the flow direction. BUT!! the value is presented in two parts. A field saying "Normal Force" and one saying "Force". Why is that? I have to add these values to get the correct number. What's the difference between "Normal Force" and "Force"?
TIA Lars Schmidt Mech. Ing. Denmark