07 giugno 17, 18:57 | #1 (permalink) Top |
Gran Decapo Data registr.: 18-03-2007
Messaggi: 14.605
| X Foil e Ncr.
Che significato ha il valore di Ncr impostabile in X Foil come descritto qui sotto ? -- Transition criterion -- Transition in an XFOIL solution is triggered by one of two ways: free transition: e^n criterion is met forced transition: a trip or the trailing edge is encountered The e^n method is always active, and free transition can occur upstream of the trip. The e^n method has the user-specified parameter "Ncrit", which is the log of the amplification factor of the most-amplified frequency which triggers transition. A suitable value of this parameter depends on the ambient disturbance level in which the airfoil operates, and mimics the effect of such disturbances on transition. Below are typical values of Ncrit for various situations. situation Ncrit ----------------- ----- sailplane 12-14 motorglider 11-13 clean wind tunnel 10-12 average wind tunnel 9 <= standard "e^9 method" dirty wind tunnel 4-8 |
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