# Airfoil CL & CD Start at normal magnitude then skyrocket.

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October 26, 2020, 21:48
Airfoil CL & CD Start at normal magnitude then skyrocket.
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Trevor T
Join Date: Oct 2020
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I'm working with a few airfoils, NACA 23012, NACA 63015A, NACA 4412, RC4-10, and Boeing VR-7, analyzing the lift, drag and moment of each.

Currently working on the NACA 63015A. Using velocities(mph) with their respective lift/drag/moment coefficients are below.
• 25mph {-0.900/0.0257/0.0225}
• 50 {-3.7196/0.881/0.0856}
• 75 {-8.507/0.182/0.1837}
• 100 {-15.368/0.30669/0.3003}
• 125 {-24.249/0.4598/0.444}
• 140 {-21.468/1.4205/0.8104}
• 150 N/A

After 25mph both lift and drag are too high. I recently changed to reference values to get the 25mph to be in its normal range.

Airfoils' length are 8.9in = .22606m

Here are the details for the 2D case:
Solver:
Pressure-Based
Velocity formulation -> Absolute

Model:
Viscous Model -> Spalart-Allmaras (1eqn)
Vorticity-Based

Fluid:
Air
Density = 1.225 (kg/m^3)
Viscosity = 1.802e-5 (Kg/m-s)

Reference Values changes:
Area = 0.22606
Density = 1.225
Depth = 1
enthalpy = 0
Length = 0.22606
Pressure = 0
Temperature 288.16
Velocity = varies
Viscosity = 1.802e-5
Ratio of specific heat = 1.4
Yplus for heat tran. coef. = 300

Turbulence
Specification Method -> Turbulent Viscosity Ratio
Ratio = 1

Outlet pressure = 0

Solution Method
Coupled
Gradient -> Least Squares Cell Based
Pressure->Second Order
Momentum -> Second Order Upwind
Modified Turbulent Viscosity -> Second Order Upwind
Pseudo Transient ->off

Report definitions of drag
x=cos(angle)
y=sin(angle)

Report definitions of lift
x=-sin(angle)
y=cos(angle)

Report definitions of moment
Center
x=1/4 of span
y= location of x in y direction.

ONE LAST THING
The contour graphics are showing the boundaries of the elements instead of a filled in contoured graph.
Attached Images
 Screenshot 2020-10-26 213440.jpg (18.1 KB, 1 views) Screenshot 2020-10-26 213340.jpg (22.1 KB, 1 views) Screenshot 2020-10-26 213326.jpg (106.4 KB, 1 views) Screenshot 2020-10-26 213149.jpg (26.9 KB, 1 views) Screenshot 2020-10-26 212921.jpg (63.4 KB, 1 views)

Last edited by T-Top; October 27, 2020 at 09:29.

 Tags airfoil 2d, drag and lift, graphics window