1998/1999 Trap Wing Data Archive

CFD Challenge – Flap Effectiveness

For the high lift designer, the ability to accurately predict increments in lift due to changes in flap deflection is vital. Configuration decisions (e.g. the choice of double-slotted vs. single-slotted flaps) rely on an accurate assessment of flap effectiveness. In the past, the high lift designer has relied on wind tunnel and flight test results to evaluate proposed configurations. A CFD code whose absolute levels of lift and drag are in error is still highly useful if its predicted increments are accurate.

Sensitivity to flap deflection for the full-span and part-span landing configurations is shown in Figure 19 for the intermediate Reynolds number Rec=8.8x106. Of interest are the increments in CL at fixed alpha (here, a=10deg), and in CLmax. For the full-span configuration, increasing flap deflection from 25 to 30 degrees results in DCL|a=10=0.15, while DCLmax » 0.02. For the part-span configuration, an increase in flap angle from 20 to 25 degrees produces DCL|a=10=0.11, while DCLmax » 0.07.

Lift changes due to flap deflection for full-span and part-span landing flaps configuration.

 

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