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Aerodynamics, Ground Effect, Lift, Drag, l:d and lofts

Question asked by Karl Mohr on Oct 24, 2011
Latest reply on Nov 5, 2011 by Karl Mohr

Hi All


I have about 10 years on SW and almost as many with FloWorks/Sim. (presently using 2011 sp 0.0)


Many months of time now on a Nurflugel, Flying Wing or Blended Wing Body (BWB) in Boeing parlance.


The concept under investigation is envisaged for Ground Effect (Surface Effect) operation @ 5-40%C:


MTOW: 1.5T

L (root chord): 5m

Span (B): 6m

Wing Area (planform): 28m

Wing loading: <54/m2

t~16.5% C


1) On DRAG: please confirm that this program (if used properly; fine mesh and converged) is suitable for estimations of thrust/power needed at various speeds and angles of attack.


2) On BOUNDARIES, there is an entry here 'apearing' to quote COSMOS stating (for 2D) 2C in front of LE, 2C above and below and 3C behind TE, please (somebody) confirm that the boundary conditions DO NOT need to be set at 200 x C as per other entry here state.


3) On LOFT: more than three 'shells' have been lofted, most with concurent results, however, two created from the SAME set of 11 scaled foil curves (scaled in excel and impoted as 'curve throgh xyz'), one shell lofted WITH four guide curves the other lofted without yield VASTLY different results: with GC giving about half the lift and DRAG tending to and becoming THRUST (perpetual motion??? )


I have tried to rationalize this, understanding that THRUST is/can be generated at wing tips (usually relatively long wings and relatively thin tips!)


Therefore with a short 'wing' with a significant 'tip' it is reasonable that tip thrust would be greater and drag on the mid section lower!  BUT.... net THRUST????