Linearized Theory of Wind-tunnel Jet-boundary Corrections and Ground Effect for VTOL-STOL Aircraft

A linear_zed theory i._ ,tereloped to obtail_ iT_terferenee faetor._for wiml tunlwl,_ and grmtnd e[feet.The calculated re._ult._',presented in tabular form iu NASA 7'eehnieal Notes 1)-033, D-93_, 17-935, and D-936, indicate that the degree to which the wake is deflected downward has a primary e[[ect on the magnitude i( the interference.When the wake i._ undefleeted the corrections are essentially the same as those of classical theory.H'hen the wake is deflected seeerely downward, the eorreetion,_' are primarify determined by the .floor1( the wind tum_el.Under these eolulitions, the corrections are, in general, much larger than tho,_e given by previou._lyavailable results.Because of deformations at the lower boumtary of the .let, the eorr,!etiol_s for an open wind tun_nel are ul_certain.Testing at low speeds and high lift eoel'ficients i7_ opelt wind tumtels, therefore, is not recomTne_uled.Although the theory is developed expressly fl_r sire.tie-element,vani,_hil_gly smaU models, method,_, with ._amplecaleulatiol_s, arc givea for extending the results to multlelemeat aml.finite-span models.The theory is at least partially verified by available test data; however, complete verifieatiott would require a sub._tantially more detailed experimental study.