New Coefficients and Interpretation 3.49.0

[Hans]

Hi!

I see that the same topics were posted, but they do not contain the clear/obvious answers (for me) what the best choise when I want to perform a hand calcution to compare VSPAERO with CFD results, and after decide where I should go further in changing the geometry of aircraft.

Please, could somebody explain me following: 

1. What is the best coefficient for the Drag analysis (CDwtot or CDtot), because usually they have 50-200% difference and it's important for the calculation of Vmax for the aircraft.

2. What is the best coefficinet for the Lift analysis (CLwtot or CLtot), because they can very near 30-50% as well.

3. Why does the fuselage with the flat tail cap have the bigger pressure at the tail cap than at the nose cap in VSPAERO? For all analysis types and forms. The pressure distibution like for the wing at the ends, but it's not a wing!

4. Why does VSPAERO not consider the fuselage lift, but affectes CMy as it has the lift.

5. Can I trust the VSPAERO results for the drag analysis in general? Or it's not acceptable even for the preliminary analysis, because it looks like this, when I compare with CFD results. (the fuselage with the flat tail cap)

5. Is the VSPAERO acceptable for the simple geomtry only? I mean for the one fuselage + wing. Becuase for the more complex geometry like a rectangle fuselage + wing + "X" empanges at the end of the fuselage + PODs (or small fuselages to simulate the motor presence) at the tips of the wings + additonal tails which I try to analysis together, it results in a spikes, or random wakes distibution, or their combination, or crushed mesh, or just unrealistic coefficients. I read enough articles that the VSPAERO can give fine results with the real test but all these test for the simple geometry like "fly wing" or "Boeing 737" in general form (All Thick: fuselage + 1 wing + 1 empanage: horizontal and vertical).

For an example:

I analyse the rectangle fuselage (thick) and wing (thin) parts, their combination and impact on each other. The main problem that the VSPAERO generates the spikes for Cl at the their interaciton. I've tried all combination of Num_W/U for the fuselage and placement of wing in/out fuselage, but the spikes still exists in more/less extent. Can I trust the CLwtot or CLtot, and CDwtot or CDtot for the general assessemnt? What the best choise? Or VSPAERO is omega in the world of CFD packges? Because all CFD results give much bigger values than VSPAERO (1.5-2 times for lift and 1-10 times for drag)