In the transition from hover to wingborn flight, V/STOL aircraft rely on the direct thrust of lift jets to supplement wing generated lift. The lifting jets interact with the flow over the aerodynamic surface to produce a complex flow around the aircraft. The simplest configuration which retains the essential characteristics of the jet/aerodynamic-surface interaction problem is a subsonic round jet exhausting perpendicularly through a large flat plate into a uniform crossflow. This configuration was studied extensively, both by experiment and by analysis. As a result, a fairly complete experiment data base exists for comparison with the numerical calculations. Research publications and presentations in this area are included. Each citation is followed by an abstract of the work

Fearn, Richard L.

English

NASA Technical Reports Server

A JET I N  A CROSSFLOW 
N A S A  GRANT N S G  2 2 8 8  
F INAL REPORT 
C o v e r i n g  t h e  p e r i o d  J a n u a r y  1 ,  1 9 7 8  - J u l y  3 1 ,  1 9 8 7  
(hasA-Ch-182469) A JEX IN A C f C S S P L O V  P i n a l  NBB-16674 
h e p o r t ,  1 Jan. 1576 - 3 1  Jul- 1SE7 ( P l o r i d a  
Cniv,) 8 p CSCL 01A 
Unclas 
G3/02 0123401 
P r i n c i p a l  I n v e s t i g a t o r :  R i c h a r d  L .  F e a r n  
D e p a r t m e n t  o f  E n g i n e e r i n g  S c i e n c e s  
U n i v e r s i t y  o f  F l o r i d a  
G a i n e s v i l l e ,  F l o r i d a  3 2 6 1 1  
Phone ( 9 0 4 ) - 3 9 2 - 0 9 6 1  
T e c h n i c a l  M o n i t o r :  Mr. R i c h a r d  J .  M a r g a s o n  
F i x e d  Wing A e r o d y n a m i c s  B r a n c h  
M a i l  S t o p  2 4 7 - 2  
N A S A  Ames R e s e a r c h  C e n t e r  
M o f f e t t  F i e l d ,  C a l i f o r n i a  9 4 0 3 5  
1 
https://ntrs.nasa.gov/search.jsp?R=19880007291 2020-03-20T07:21:02+00:00Z
Introduction 
In the transition from hover to wingborn flight, V/STOL 
aircraft rely on the direct thrust of lift jets to supplement 
wing generated lift. The lifting jets interact with the flow 
over the aerodynamic surface to produce a complex flow around the 
aircraft. This usually results in a l o s s  of lift and an increase 
in nose-up pitching moment (Ref. 1). Hence, the jet/aerodynamic- 
surface interference effect is a significant problem in V/STOL 
aerodynamics. 
The simplest configuration which retains the essential 
characteristics of the jetlaerodynamic-surface interaction 
problem is a subsonic round jet exhausting perpendicularly 
through a large flat plate into a uniform crossflow (Fig. 1). 
This configuration has been studied extensively, both by 
experiment (Refs. 2-7) and by analysis (Refs. 8-15). A s  a 
result, a fairly complete experimental data base exists for 
comparison with the numerical calculations. 
Cross Section to Jet Plume 
Contrarotating vortex pair 
Figure 1. Sketch of the Jet in a crossflow 
2 
SUMMARY OF PUBLICATIONS AND PRESENTATIONS 
T h e  research supported by this grant was presented t o  t h e  
research community i n  the following presentations and 
publications. Each citation is followed by an abstract o f  t h e  
work. 
1. Fearn, Richard L. and Weston, Robert P.: Velocity Field o f  a 
Round Jet i n  a Cross Flow for Various Jet Injection A n g l e s  
and Velocity Ratios. NASA TP-1506, Oct. 1979. 
An experimental investigation o f  a subsonic round j e t  
injected from a flat plate into a subsonic crosswind o f  t h e  
same temperature has been conducted i n  t h e  Langley V/STOL 
tunnel. Velocity a n d  pressure measurements i n  planes 
perpendicular to t h e  path of the j e t w a r e  presented f o r  
nominal jet injection angles of 4 5 " ,  60", 7 S 0 ,  90" and 1 0 5 "  
and for jet/cross-flow velocity ratios o f  4 and 8. Th e s e  
velocity measurements were obtained for t h e  purpose o f  
-inferring the properties of the vortex pair that is 
associated with a jet i n  a cross flow. Jet c e n t e r l i n e  and 
vortex trajectories are determined a n d  fit with an empirical 
equation that includes the effects o f  j e t  injection angle, 
j e t  core length, and jet/cross-flow velocity ratios. 
2. Fearn, Richard L. and Benson, J. Paul: Ve'locity Field Near 
t h e  Jet Orifice of a Round Jet i n  a Crossflow. NASA 
CR-137,857, Dec., 1979. 
Experimentally determined velocities at selected 
locations near t h e  jet orifice are presented a n d  analyzed 
f o r  a round jet i n  a crossflow. J e t - t o - c r o s s f l o w  velocity 
ratios o f  four and eight were studied experimentally for a 
round subsonic jet o f  air exhausting perpendicularly through 
a flat plate into a subsonic crosswind o f  t h e  same 
temperature. Velocity measurements were m a d e  i n  cross 
sections t o  t h e  j e t  plume located from o n e  t o  f o u r  jet 
d i a m e t e r s  from t h e  o r i f i c e .  Jet centerline and vortex 
properties are presented a n d  utilized t o  extend t h e  r e s u l t s  
o f  a previous study into the region close t o  t h e  j e t  
ori f ice. 
3. Fearn, R.; Kalota, C. and Dietz, W. E., Jr.: A 
Jet/Aerodynamic Surface Interference Model. Proceedings o f  
a Workshop on V/STOL Aircraft Aerodynamics, Naval 
Postgraduate School, Monterey, CA, May, 1979. 
A model is presented that relates the pressure distribution 
on an aerodynamic surface to properties o f  t h e  j e t  plume. 
T h e  primary characteristics o f  a j e t  i n  a c r o s s f l o w  t h a t  
determine the pressure distribution on t h e  aerodynamic 
surface are assumed t o  be: 
3 
( 1 )  the pair o f  contrarotating vortices associated 
(2) entrainment o f  fluid by t h e  jet. 
(3) a wake region near the aerodynamic surface 
The model is applied t o  the configuration o f  a round j e t  
exhausting through a flat plate into a crossflow. 
Experimentally determined properties o f  t h e  vortex pair are 
utilized in t h e  model for perpendicular j e t  injection and a 
range o f  j e t  t o  crossflow velocity ratios. Reasonable 
values o f  entrainment and a simple wake assumption a r e  used. 
Comparisons o f  t h e  calculated pressure distributions and 
aerodynamic loading with experimental results are included. 
with the jet. 
immediately downstream o f  t h e  jet. 
4. Braden, Susan: Vorticity Associated with Multiple J e t s  i n  a 
Crossflow. AIAA 31st Annual Southeastern Region Student 
Conference, Atlanta, GA, 1980. 
A preliminary investigation vortex patterns from 
multiple subsonic jets exiting perpendicularly through a 
flat plate into a subsonic crossflow has been conducted at 
t h e  Engineering Sciences Department, University o f  Florida. 
Two multiple j e t  configurations, tandem and transverse, were 
examined. A paddle wheel sensor was utilized t o  indicate 
the presence a n d  relative magnitude o f  streamwise vorticity 
in t h e  flow. This method is shown t o  be an effective and 
inexpensive way t o  obtain qualitative information about 
streamwise vorticity associated with a j e t  in a crossflow. 
Results are presented i n  the form o f  contour plots o f  
rotational speed o f  the paddle wheel as measured i n  planes 
downstream from t h e  j e t s  and perpendicular t o  t h e  crossflow. 
These contour plots indicate the presence o f  well developed 
diffuse contrarotating vortices for the configurations 
studied. The location a n d  strength o f  t h e s e  vortices 
depends on the multiple jet configuration and t h e  distance 
downstream from the jets. The results f o r  single jet c a s e s  
are compared with those o f  previous experiments. 
5. Furlong, Kelly L .  and Fearn, Richard L . :  A lifting S u r f a c e  
Computer code with Jet-in-Crossflow Interference Effects, 
vol. 1-Theoretical Description, vol. 2-Users Guide for 
WBWJAS. NASA CR-166524, Aug., 1983. This work was also 
supported by NASA Grant NCC2-133. 
A method is proposed to combine a numerical description 
o f  a jet i n  a crossflow with a lifting surface panel code t o  
calculate t h e  jet/aerodynamic-surface interference effects 
on a V/STOL aircraft. An iterative technique is suggested 
that starts with a model for the properties o f  a jet/flat 
plate configuration and modifies these properties based on 
t h e  flow field calculated for t h e  configuration o f  interest. 
4 
The method would estimate the pressures, forces, and moments 
on an aircraft out of ground effect. 
A first-order approximation to the method suggested is 
developed an applied to two simple configurations. The 
first-order approximation is a non-iterative procedure which 
does not allow for interactions between multiple jets in a 
crossflow and also does not account for the influence of 
lifting surfaces on the jet properties. The jet/flat plate 
model utilized in the examples presented is restricted to a 
uniform round jet injected perpendicularly into a uniform 
crossflow for a range of jet-to-crossflow velocity ratios 
from three to ten. Numerical results for a streamlined body 
of revolution and a symmetrical airfoil are presented. The 
numerical results show that there is good agreement between 
experimental and model calculated surface pressure data for 
the body of revolution and the non-lifting wing, but 
indicate the need for iterative techniques for handling the 
interactions between lifting surfaces and a jet in a 
crossflow. 
This report is divided into two volumes. The first 
volume i s  a theoretical description of the computer code 
developed. The second volume is a detailed Users Guide for 
the computer code. 
6. Fearn, R.L.; Progress Toward a Model to Describe 
Jet/Aerodynamic-Surface Interference Effects. Synoptic in 
A I A A  Jour., vol. 22, pp. 752-753, June, 1984. Full paper in 
Recent Advances in Aerodvnamics, Proceedings of an 
International Symposium at Stanford, Aug., 1983, ed. A .  
Krothapalli and C . A .  Smith, Springer-Verlag, 1985. 
pressure distribution on an aerodynamic surface to 
properties of the jet plume. The characteristics of a jet 
in a cross flow that are of primary importance in 
determining pressure distribution on the aerodynamic surface 
are assumed t o  b e :  1)  a pair of contrarotating vortices 
associated with a jet in a cross flow, 2) entrainment of 
cross-flow fluid into the jet plume, and 3 )  a wake region 
near the aerodynamic surface and extending downstream from 
the jet orifice. The model is applied to the configuration 
of a round jet exhausting perpendicularly through a flat 
plate into a uniform cross flow for a range of jet-to-cross- 
flow velocity ratios o f  3-10. It is demonstrated that the 
model is capable o f  describing the measured pressure 
distribution on the first plate with model parameters that 
are compatible with the known properties of the jet plume. 
A first-generation model is presented that relates the 
5 
7. Roth, K.R.: Stability o f  Closed Loop Filaments as 
Computational Elements for a Three-Dimensional Vortex 
Filament Algorithm. MS thesis, University o f  Florida, 1986. 
A three-dimensional vortex filament model is developed 
and validated for inviscid f l o w  calculations. T h e  
propagation of a single vortex ring and t h e  leapfrogging o f  
t w o  vortex rings are simulated. Results o f  t h e s e  
simulations are compared with theoretically and numerically 
predicted values. A parametric study is conducted t o  assess 
t h e  stability o f  the closed loop filaments which are t h e  
basic computational element. Simulation o f  t h e  
jet/aerodynamic-surface interference effect f o r  V/STOL 
aircraft with the three-dimensional vortex filament method 
is discussed. 
6 
~. . , . . .  . ,  .i_l... , - . . .  ~ . . . .  - , 
References 
1. 
2. 
3 .  
4. 
5. 
6. 
7. 
8 .  
9. 
10.  
1 1 .  
12. 
1 3 .  
Margason, R. J. and Fearn, R .  L . :  Jet-Wake Characteristics 
and Their Induced Aerodynamic Effects on V/STOL Aircraft. 
NASA SP-228, 1969. 
Fearn, R. L .  and Weston, R. P.: Vorticity Associated with a 
Jet i n  a Crossflow. A I A A  J., Vol. 12, No. 12, pp.1666-1671, 
1974. 
Fearn, R. L. and Weston, R. P . :  Induced Pressure 
Distribution o f  a Jet in a Crossflow. N A S A  TN D-7626, 1975. 
Fearn, R. L .  and Weston, R. P.: Induced Velocity Field o f  a 
Jet in a Crossflow. NASA TP-1087, 1978. 
Fearn, R .  L. and Weston, R. P.: Velocity Field o f  a Round 
Jet i n  a Crossflow for Various Jet Injection Angles and 
Velocity Ratios. NASA TP-1506, 1979. 
Schetz, J. A,, Jakubowski, A. K. and Aoyagi, K . :  Jet 
Trajectories and Surface Pressures Induced on a Body o f  
Revolution with Various Dual Jet Configurations. 
3. Aircraft, Vol. 20, No. 1 1 ,  1983. 
Snyder, P. and Orloff, K .  L . :  Three-Dimensional Laser 
Doppler Anemometer Measurements o f  a Jet in a Crossflow. 
NASA TM 85997, 1984. 
Adler, D .  and Baron, A.: Prediction o f  a Three-Dimensional 
Circular Turbulent Jet in a Crossflow. AIAA J., Vol. 17, 
N O .  2, p p .  168-174, 1978. 
Baker, A. J. and Orzechowski, J. A . :  Prediction o f  
Turbulent Near-Field Evolution o f  a Jet i n  a Crossflow Using 
a PNS Solver. NADC Report 85177, 1986. 
Chang, H . :  Aufrollung lines rylindrischen Strables durch 
Querwind. Doctoral Dissertation, Gottingen, 1942. 
Fearn, R. L. :  Progress Towards a M o d e 1 , t o  Describe 
Jet/Aerodynamic-Surface Interference Effects. A I A A  J., Vol. 
22, NO. 6, p p .  752-753, 1984. 
Karagozian, A. and Greber, I.: A n  Analytical Model f o r  t h e  
Vorticity Associated with a Transverse Jet. AIAA Paper 8 4 -  
1662, 1984. 
Maskew, B., Strash, D., Nathman, J. and Dvorak, F. A.: 
Investigation t o  Advance Prediction Techniques o f  t h e  L o w -  
Speed Aerodynamics o f  V/STOL Aircraft. 
1983. 
NASA GR-166479, 
7 
14. Sykes, R. I., Lewellen, W .  S. and Parker, S. F.: On t h e  
Vorticity Dynamics o f  a Turbulent Jet in a Crossflow. 
J .  Fluid Mech., Vol. 168, p p .  393-413, 1986. 
15. Wooler, P. T . ,  Kao, H .  C., Schwendemann, M. F., Wasson, H. 
R .  and Ziegler, H.: V / S T O L  Aircraft, Aerodynamic Prediction 
Methods Investigation. Technical Report A F F D L - T R - 7 2 - 2 6 ,  
Vol. I - I V ,  1972. 
a 


A jet in a crossflow

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server