![[Company Logo Image]](images/logo.jpg){kind=logo}
F.F.V.S. J22 Fighter Aircraft
From a technical perspective
Service in the Swedish Airforce 1943-1952
From a technical perspective Service in the Swedish Airforce 1943-1952 |
|
Fighter comparison, 1000-1150hp Fighter comparison, mid to late 1943 |
CFD analysisMy friend and former colleague, Leonard Wish, LW CFD Solutions Inc., did a CFD (Computational Fluid Dynamics) analysis of the J22, based upon a 3D computer model that I had prepared. Leonard is a consultant in the Aerospace industry. The software he is using is the NASA TetrUSS which is capable of both inviscid and viscous (Navier-Stokes/Euler) solutions. We did this in order to visualize the pressure distribution and to see if there was any areas of flow separation or general concern that could have been avoided. We also wanted to know where the stick-fixed neutral point was, in order to compare with other WWII fighters. The Center of Gravity locations of the J22 are not known to me, but based upon pilot reports we can conclude the it was just marginally stable as it was extremely quick is control responsiveness, just like the FW190. The initial analysis was inviscid. Speed is 357mph true at 11,500ft at 0° angle of attack.
Initial comments: It seems like the wing-fuselage intersection is very clean and they did a great job decreasing the interference drag. There seems to be an area of concern around the leading edge of the empennage. The lower portion of the wing leading edge shows an area of lower pressure which is the increased camber. The front lower portion of the windshield has an area of high pressure buildup, due to the slope of the windshield. Overall impression is that the aircraft is very clean. Blue color corresponds to low pressure and Red color to high pressure. Oil tracesIn order to better visualize the air flow, Leonard prepared an Oil trace solution.
The area in the leading edge of the wind shield might have separated air flow. We will have to run a viscous solution to find out for sure.
The area around the empennage seems to be ok. Again, a viscous solution will tell for sure.
Wing tip vortices.
Exhaust stub flow pattern. The simulation is not performed with an open cowl, thus the true flow through the exhaust is not shown, however, It still shows the flow pattern around and behind the stub.
Chord wise and span wise pressure distributionLeonard prepared some plots of the chord wise and span wise pressure distributions. 3 cuts span wise and 2 chord wise. Span wise cuts were made at FS=71, 81.5 and 90. Chord wise were made at BL=30 and BL=175.
It is interesting to see, that at a STA=71, the upper and lower pressure of the wing-fuselage intersection equals the pressure to almost zero! No lift in the area. Note that the cut is made at the front portion of the windshield where pressure is highly positive, hence the increase in pressure on the upper surface.
The cut at STA=81.5 still shows the higher pressure are of the windshield in the upper surface graph.
The cut at STA=90 is where the slope of the windshield is changing. Note the pressure drop (peak) on the upper surface. 2 cuts were made chord wise, at BL=30 and BL=175
The section cut at BL=30 shows an increase in upper and lower surface pressure gradient at the leading edge. The wing has a gradual increase in leading edge camber from BL=0 to the wing tip. At this section you can notice the slight increase in leading edge camber due to the slight pressure peak.
At BL=175 the leading edge camber is more defined. Upper surface shows a nice gradual pressure gradient. The lower surface shows an increase in pressure just aft of the leading edge.
Stick-fixed, power off and power on, Neutral point locationHere is the stick-fixed, power off, N/P location of a few fighters. Neutral point location and static stability is in reference to the MAC (mean aerodynamic chord) (Ref. 22). Aft c/g position used as reference.
Power on moves the N/P fwd by approx. 4-5%, which concludes that the Spitfire IX and the FW190D-9 were neutrally stable during normal flight, the FW190A-8 was slightly unstable, where as the P-51 was just marginally positively stable. The J22 was, as far as I know, positively stable, power on. My assessment is that the power off/power on stability margin of the J22 was about the same as for the P-51B. The static stability margin, Sm, would then have been similar to the P-51B.
|
|
Send mail to hlangebro@hotmail.com with
questions or comments about this web site.
|
