Vortex Generator Installation Drag on an Airplane Near Its Cruise Condition

A method is discussed for predicting the drag increment caused by the installation of a blade-type vortex generator (VG) on a transonic-transport airplane. The original Nash and Bradshaw magnie cation concept of roughness drag is extended to cover compressible e ows and then is applied to VG blades to estimate the VG installation drag on an airplane. Thedrag of a VG blade placed on a wing will beamplie ed dueto thegrowth of the boundary layerwith distance along thewing surface. Nash and Bradshaw showed that thedegree of magnie cation cannot be approximated simply by the ratio of local to freestream dynamic pressure ( q effect). To demonstrate the magnie cation effects, some VG installation drag analyses for transonic-transport airplane models are performed using the new magnie cation factor formula. It can be seen that the agreement between these predicted drag increments and the wind-tunnel test results is good, but the drag increment based on the q effect is seriously underestimated.