NASA-CR-175624 

19850014056 

Status Report on NASA Grant NAG 1-396 

"Calculation of Vortex-Flap Aerodynamic Characteristics" 

" , 

October 1, 1984 - March 31, 1985 

by 

C. Edward Lan and C. C. Hsing 

April 22, 1985 

The Flight Research Laboratory 

Department of Aerospace Engineering 

The University of Kansas 

Lawrence, Kansas 66045 

liBRARY COpy 

LANGLEY RES:::ARCH CENTER 

LIBRARY, NASA 

HAMPTON, VIRGINIA 

111111111111111111111111111111111111111111111 

NF00727 
The primary objective in this reporting period (October 1, 1984 to 

March 31, 1985) was the calculation of lateral-directional characteristics 

for configurations with vortex flaps. The calculation was done with the 

VORSTAB code (Ref. 1). The latter was also used by Grantz in Reference 2. 

In view of the poor correlation between the VORSTAB results and data in 

Reference 2, it was decided to examine in detail the reasons behind the 

discrepancy. At first, it was found from the input data of Reference 2 

that the leading edge shape used in the VORSTAB code was inconsistent with 

that for the NASA VLM-SA code. Secondly, the straight fuselage was described by only a few input points of largely different intervals and - through the cubic spline interpolation. As a result, the interpolated 

shape was largely distorted. This was corrected by using straight-segment 

interpolation. Finally, one error in calculating the lateral-directional 

derivatives for configurations with leading-edge vortex flaps with or 

without deflections was discovered in the code. After these corrections, 

characteristics for Grantz configurations were re-calculated with results 

presented in Figs. 1 - 4. In Fig. 1, it is seen that C

L with undef1ected 

vortex flap is underpredicted for this configuration. The same situation 

is true also for the NASA VLM-SA code (Ref. 2). In addition, data show 

that full effect of vortex bursting does not occur until at a higher angle 

of attack than that predicted by the theory. On the other hand, with the 

vortex flap deflected at 40 deg., the lift is over-predicted as shown in 

Fig. 3. It is possible that this may have been caused by the presence of 

forbody vortices. 

The prediction of dihedral effect is now largely improved as shown 

in Figs 2 and 4. The original calculation by Grantz can be found on pages 

138 and 140 of Reference 2. 

In addition to calculating lateral-directional characteristics for 

configurations with vortex flaps, exercising the design concept of vortex 

flaps with two-level optimization for a 700 /500 cranked arrow wing has also 

been under way during this reporting period. 

References 

1. Lan, C. E., "VORSTAB-A Computer Program for Calculating Lateral-Directional Stability Derivatives with Vortex Flow Effect", NASA CR-172501, 

January 1985. 

2. Grantz, A.C., "The Lateral-Directional Characteristics of a 74-Degree 

Delta Wing Employing Gothic Planform Vortex Flaps", NASA CR-3848, Nov. 1984. 

1 
References, Continued: 

3. Johnson, J. L., Jr., Grafton, S.B. and Yip, L.P., "Exploratory 

Investigation of the Effects of Vortex Bursting on the High-Angle-ofAttack Lateral-Directional Stability Characteristics of Highly-Swept 

Wings", AIAA Paper 80-0463. 

2 
d 

1~------------------------------------~~ 

, e- Data (NASA CR-3848) e, --- Vortex Buret on 

- - - - - • Vortex Bum off 

G 

, e 

G' , 

, 

O.O'-----'----"-----'---I...-o-~---il.-------' 

o 10 20 

Angle of attack (deg.) 

F1g-1 Comparfson of theoretical and experfmental 

longttudlnal 11ft coeffictents with $,,-0. 

3 
c -- o 

~~--------------------------------------------, 

------~e~--------~ --------

e 

G 

a- DatG (Ref. 2 ) 

~- Data (Ref. 3) -70-deg Delta 

VORTEX BURS!" ON - - - - _. VORTEX BURSr OFF 

" .. .. 

2D • 

Angle of attack (deg.) 

(a) Tall off 

Flg-2 Comparison of theoretical and experimental lateraldIrectional atabtnt;y characteristics with ~,,- o. 

4 
.J 

o 

1~~--------------------------------------

G 

(3- Data (NASA CR-3IU8) 

--- Vortex Burst on - - - - - • Vortex Bum off 

, 

~O~--------~--~--~~--~--~~--~--~ 

o 10 20 

Angle of attack (<leg.) 

Ftg-3 Comparfaon of theoretical and experimental 

Jongltudtnal 11ft coefficIents with ~u -.a. 

5 
· , 

~~------------------------------------------~ 

L-------.:~-:....;-~-...:-~- - - Q .. - - • - - ........ - .. 

e e 

8'----___ -...«a....._ ........ O::,,_ -:_:""':_::-:_-:_~ __ ........ - - - _-.;;;....0 

a- DATA (NASA CR-3IW8) 

VORTEX BURST ON - - - - -. VORTEX BURST OFF 

e 

2D 21 

AnP of crttac:k (deg.) 

(a) Tan off 

... ... .. .. .. .. .. .. .. .. .. .. 

FJg-4 Comparilion of theoretical and experfmental lateraldIrectional stabtltty charactertstlcs with ~ I.E. - 40. 

6 
End of Document