U. From results, Configuration 2 has better flow

U.
Ali (2016) research objective was to study control the flow by inserting
leading-edge and cross-flow slots and analysis the viscous flow over the outer
plane to maximize the performance of elevons control surfaces 10. Second objective
was to predict high lift performance particularly the maximum –lift
characteristics 10.
 The author carry out experimental (wing
tunnel experiment) and numerical CFD analysis on the clean baseline models in
order to achieve the objectives. Two flying wing models configuration was
involve in the research, one has a sweep angle of 40° and a root chord of 0.4m
called Configuration 1 whereas the other model has leading edge sweep angle 60°
and root chord of 0.53m called Configuration 2. The computational methods from
vortex-lattice, Euler and Reynold-Average Navier-Stroke (RANS) were implemented
to evaluate the flow configurations and validate the wind tunnel experiment. A
commercial CFD code Fluent was used to conduct turbulence simulation and CFD
solver was used to perform non-linear Euler simulations. Fluent help solve the
RANS equations. As for the geometry and grid details the CAD models used were
created in SolidWorks then exported to a CAE system grid generator called ANSA
for meshing. Three different meshes for Configuration 1 and four different
meshes for Configuration 2 were generated where grid size increased from course
to medium and then fine and very fine. The simulation for the grids were
performed where angle of attack generate maximum lift for each configurations. From
the analysis, for Configuration 1 half a million cells (0.5m) at angle of
attack 19.197° and for Configuration 2 two million grids (2m) at angle of
attack 29.041° was chosen respectively for full flight envelop computations.  Spalart-Allmars turbulence model was used for
all computational analysis. Free stream condition are provided from the wind
tunnel tests where Mach number was 0.1 and Reynold number was . Aerodynamic characteristic and moment were measured
as a function of angle of attack range from -20° to 40°.  From results, Configuration 2 has better flow
control due to higher lift noticed at high angle of attack.  It can be seen that the moment coefficient
decrease as angle of attack increases.   Computation
using Euler equations is better to capture the separated-vortex flow behavior
and maximum-lift characteristics. 
However, results obtain from RANS method provide similar level of
agreement with the experiment to the Euler equations.  The research concludes that the leading-edge
slot technique works for low angle of attack only. 

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