Project Falcon

[#1]

What is Fd stand for in result? and if it is drag force then why am i getting lower drag force via calculation by using same coefficient of drag as shown in falcon.I m getting Cd approx 1.22 on a block of 1 m^2 cross section at the speed of 10m/s. then how it is possible that drag force calculated by the falcon is 83.189 N?? (Attched Photo)

While I am using formula for drag force .5*Cd*(rheo)*A*V^2 then i am getting 74.725 N (assuming the density of air 1.225 kg/m^3)...plz help if u can its really important for my project...or suggest me any alternataive way...
Thanks & Regards..

[#2]

Fd is the approximate drag force on the body, that is, the drag force along the direction

One factor to consider is that the air domain is rather small, and air has to fit between the object and the tunnel walls to make its way through. The true free stream velocity around the object is above 10m/s. If you are expecting something in the low 80N range, it only takes a few tenths of a m/s more to get to those kinds of values.

Another thought is that your image appears to show a thin 2D surface in a 3D volume, and I suspect the calculation of cross sectional area may be affected by the mesh resolution. Have you tried with a finer mesh?

[#3]

Please Reply as soon as possible...

I analysed a plate in different wind tunnel then I am getting different value of Drag Force Fd & Coefficient of Drag for a verticle plate of 1 m^2 cross sectional area and 100 mm thickness while changing the wind tunnel size in project Falcon by autodesk (I attached photo of analysis with different wind tunnel size..take a look) How it is possible?? Wht should i do so that i can get correct result? 

1. plz help me to decide optimal size of virtual wind tunnel in falcon so that i can get correct answer..

2. Wht is the volume stand for that i highlighted in the pics??

plz reply..
Thanks & Regards..