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ANALYSIS OF AERODYNAMIC CHARACTERISTICS OF ORIGINAL
AND MODIFIED WING-STRAKE ARRANGEMENT OF JF-17
THUNDER AIRCRAFT
A. Maqsood, J. Masud, O. A. Qazi
Department of Aerospace Engineering, College of Aeronautical Engineering,
National University ofSciences and Technology, Risalpur 24090, Pakistan
SUMMARY
The aim of the research is to carry out the comparative studies based on the change in aerodynamicbehavior of original and modified configurations of JF-17 wing-strake arrangement. Two geometries are analyzedto observe variation with the size of strake. The original configuration has comparatively smaller strake than themodified geometry. Both geometries are analyzed using a shareware software PANAIR based on linearized
potential flow theory to fulfill the baseline requirement of the project.
Even in this era of computer technology solving complete Navier-Stokes equations for an
aerodynamic problem for a complex geometryduring design phase is computationally very
expensive. Therefore there is a need for a simplifiedmodel that allows for an easy grasp of dominantaerodynamic effects. The classical model of a thinviscous boundary layer along a body’s surfacesurrounded by a mainly inviscid flow field has produced important engineering results. Thisapproach requires first the solution of the inviscidflow to obtain the pressure field and consequentlythe forces such as lift, induced drag and moments.
Then a solution of the viscous flow in the thin boundary layer allows for the calculation of the skinfriction effects. This methodology has been usedsuccessfully over years for most of the airplane andmarine vessel designs. With the development ofcomputer speed and capacity, the inviscid flow fieldover complex and detailed geometries like airplane,space shuttles, cars etc can be computed by means ofnumerical panel techniques.
A readily available shareware panel method codeA502i is a pilot version of PANAIR code developedjointly by Boeing and NASA. Modeling andmeshing were done in preprocessing softwareGambit. This research enabled us to establish theaccuracy of the available panel code A502i and alsostudy the effects of different flight conditions onaerodynamic characteristics of an aircraft withoutcarrying out the wind tunnel tests or solvingcomplete Navier-Stokes equations.
The analysis carried out in PANAIR isbased on potential flow theory. Both configurations
were tested at Mach# 0.6, 0.8, 1.4 and 1.6. Theangles of attack specified are 0,5,10 and 15 degrees
Following are the baseline objectives of the research carried out
(a) The prediction of forces and momentsdeveloped over both configurations in subsonic and
supersonic regimes.
(b) Visualization of flow over the surfaces of both configurations.
RESULTS & DISCUSSION
The computed results in subsonic andsupersonic flow conditions for coefficient of lift,drag and pitching moments are compared for bothconfigurations. The pressure distributions over thesurfaces for different flight conditions are alsoshown. The graphs are plotted to have anapproximation for the changes in various aerodynamic parameters because of themodification.
The basic flow field around the modeledgeometries consists of free stream flow beingmodified by the presence of the aircraft bodies. Theflow adjacent to the aircraft generally follows theaircraft contour and as per the limitation of potential
flow, no flow separation is expected to occur even at high angle of attacks. The pressure variation atsubsonic flows at lower angle of attacks is shown for
both configurations at M# 0.6. Since the present analysis is based on
potential flow assumptions therefore the regions of locally high or low velocity can easily be identifiedby corresponding regions of low or high Cp values.
As the angle of attack increases, the flowaccordingly accelerates around the aircraftincreasingly larger region of negative Cp on theupper surface of the wings can be witnessed.
Conclusion from the Results
It can be concluded from the results that the major purpose of the wing-strake modification is toincrease the instability of the aircraft. Initially JF-17
was not having fly-by-wire system but now thesystem has been introduced in the aircraft. Thepurpose of this aerodynamic modification is narrated
below.
In the beginning, if we want to trim the aircraft at higher angles of attack, large deflection in horizontal tail was required which resulted in higher trim and
pressure drags contributed to the aircraft. After this modification, if we want to trim the aircraft at a higher angle of attack, the drag produced by the
horizontal tail will be less and as a cumulative factor, overall drag reduction will happen.
Source : https://www.researchgate.net/public...-STRAKE_ARRANGEMENT_OF_JF-17_THUNDER_AIRCRAFT
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