Aerodynamics thread

[MiG-29]

Thrust Vectoring would be generating lift if it is balanced across the center of gravity of the airplane, i.e. at the front. So a plane with a front lifting thrust vector, namely VTOL, in theory, could use their trust vector to asist turning and compensate for the loss of lift, at a greater sacrefice of airspeed.

The speech Engineer posted hit the head with a nail. If you know your opponent had engaged trust vectoring, you know they had just blown off a ton of energy. Thus when you lift up your plane, there is no way they can follow you without stalling.

Gravity is a vector, thrust is a vector, lift is a vector.

Thrust vectoring generates a pitch up force increasing the pitch up of the nose in a turn, in few words goes parallel to the lift.

Thrust is a vector when is perpendicular to lift, is a vector, changing the angle with respect the lift won`t stop making it a vector.

In Physics the Resultant is the product of two or more vectors, you have 4 basic vectors when the aircraft is turning, lift, gravity, drag and thrust.

By the way, lift is not in the same position of gravity that is another fantasy, lift is ahead of the center of gravity in an unstable design generating a strong pitch up nose force.

 

[Engineer]

Re: J-20 The New Generation Fighter Thread IV

taiplane are airfoils, they do generate lift.

Thrust vectoring is not an airfoil, hence doesn't generate lift.

 

[Engineer]

Gravity is a vector, thrust is a vector, lift is a vector.

We are talking about thrust vectoring, not "gravity vectoring" or "lift vectoring. So, thrust vectoring has nothing to do with gravity or lift.

Thrust vectoring generates a pitch up force increasing the pitch up of the nose in a turn, in few words goes parallel to the lift.

Thrust is a vector when is perpendicular to lift, is a vector, changing the angle with respect the lift won`t stop making it a vector.

Thrust vectoring has to do with the components in the thrust, and has nothing to do with lift. Putting "thrust vectoring" and "lift" into a single sentence doesn't turn your fantasy into reality and doesn't make one equates to the other. Furthermore, pitch up is a moment, not a force. A brick can pitch up all it wants, but it will still flies straight because the brick doesn't have lift.

In Physics the Resultant is the product of two or more vectors, you have 4 basic vectors when the aircraft is turning, lift, gravity, drag and thrust.

Product of vectors is torque, not force. Lift, gravity, drag and thrust are forces.

By the way, lift is not in the same position of gravity that is another fantasy, lift is ahead of the center of gravity in an unstable design generating a strong pitch up nose force.

This doesn't make thrust vectoring generate lift.

 

[Engineer]

Thrust Vectoring would be generating lift if it is balanced across the center of gravity of the airplane, i.e. at the front. So a plane with a front lifting thrust vector, namely VTOL, in theory, could use their trust vector to asist turning and compensate for the loss of lift, at a greater sacrefice of airspeed.

Exactly. Without a balance, all thrust vectoring does is produce a torque. The so called increased maneuverability of TVC is typically associated with post-stall maneuvers. It was envisioned that a plane can literally flip backward to shoot an enemy at the tail through the use of TVC. However, that kind of maneuvering is not aerodynamically related, and is different from a maneuver such as turning which depends on aerodynamics. The latter kind depends on lift, which is limited by the airframe.

The speech Engineer posted hit the head with a nail. If you know your opponent had engaged trust vectoring, you know they had just blown off a ton of energy. Thus when you lift up your plane, there is no way they can follow you without stalling.

This has been proven in real world exercises.

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.

 

[MiG-29]

Re: J-20 The New Generation Fighter Thread IV

Thrust vectoring is not an airfoil, hence doesn't generate lift.

Thrust vectoring is a vector, lift is a vector and as a result you get a resultant


Dynamic interference effects caused by vectoring remain.
The lift coefficient was affected by approximately 0.1 with vectoring (Fig. 23). This value varied
slightly at the higher angles of attack. Vectoring-down caused an increase in lift coefficient (C'L), and
vectoring-up the converse, such as a blown flap might produce on a wing. 1° At higher angles of attack,
above the maximum CL, vectoring-down caused a larger increase in the absolute value of lift coefficientincrement from unvectored data than vectoring-up, approximately 0.10 to 0.06, respectively, at a = 55 °.

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[MiG-29]

This doesn't make thrust vectoring generate lift.

Thrust is a vector, lift is a vector and the aircraft flight path is a resultant of all the vectors

 

[MiG-29]

Exactly. Without a balance, all thrust vectoring does is produce a torque.

Flight path = resultant specially on a fighter that is unstable and where the lift is ahead of the center of gravity

Regardless of nozzle geometry, the post-exit vane
yaw vectoring concept always produced resultant yaw
vector angles which were smaller than the geometric
yaw vector angle of the vanes. Other investigations
of thrust-vectoring concepts (refs. 16, 26, and 27) in-
dicated that low values of resultant thrust-vector an-
gle can result from turning supersonic exhaust flow.
Vectoring supersonic flow at the nozzle exit is less
efficient in turning than vectoring lower velocity flow
in the vicinity of the nozzle throat. Thrust-vectoring
concepts which initiate flow turning inside the noz-
zle at subsonic or slightly supersonic conditions tend
to result in thrust-vector angles which are equal to
or, in some cases, greater

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after this go an read Physics and linear algebra

 

[Engineer]

Thrust is a vector, lift is a vector and the aircraft flight path is a resultant of all the vectors

Wrong. Flight path is the resultant of all the forces. Since thrust vectoring produces a moment, vectoring does not affect flight path.

 

[Engineer]

Flight path = resultant specially on a fighter that is unstable and where the lift is ahead of the center of gravity

Flight path has nothing to do with thrust vectoring. Thrust vectoring causes change in thrust components. These components are orthogonal. Those components that do not act on the aircraft's center-of-gravity hence produces a moment. Therefore, those components do not change the aircraft's flight direction, nor do they enhances lift.

Regardless of nozzle geometry, the post-exit vane yaw vectoring concept always produced resultant yaw vector angles which were smaller than the geometric yaw vector angle of the vanes. Other investigations of thrust-vectoring concepts (refs. 16, 26, and 27) indicated that low values of resultant thrust-vector angle can result from turning supersonic exhaust flow. Vectoring supersonic flow at the nozzle exit is less efficient in turning than vectoring lower velocity flow in the vicinity of the nozzle throat. Thrust-vectoring concepts which initiate flow turning inside the nozzle at subsonic or slightly supersonic conditions tend to result in thrust-vector angles which are equal to or, in some cases, greater

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after this go an read Physics and linear algebra

Your paper said "yaw angle", which is not a lift. LMAO! In fact, nowhere in the paper does it mention that thrust vectoring produces lift. Yes, you go back and study physics and linear algebra. Given that you think yaw has anything to do with lift, you obviously have no idea what you are talking about.

 

[Engineer]

Re: J-20 The New Generation Fighter Thread IV

Thrust vectoring is a vector, lift is a vector and as a result you get a resultant

Side components of thrust resulting from thrust vectoring produces a moment and not a force, hence has nothing to do with the resultant. In other words, thrust vectoring does not increase lift.

Dynamic interference effects caused by vectoring remain. The lift coefficient was affected by approximately 0.1 with vectoring (Fig. 23). This value varied slightly at the higher angles of attack. Vectoring-down caused an increase in lift coefficient (C'L), and vectoring-up the converse, such as a blown flap might produce on a wing. 1° At higher angles of attack, above the maximum CL, vectoring-down caused a larger increase in the absolute value of lift coefficientincrement from unvectored data than ectoring-up, approximately 0.10 to 0.06, respectively, at a = 55 °.

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Thrust vectoring up takes place when an aircraft needs a pitch up moment, as would occur during a turn. Your quote from the paper says that vectoring-up decreases lift coefficient, because the converse increases lift coefficient. In other words, the tests showed thrust vectoring on that F-18 kills lift during a turn. This is summarized elegantly in the conclusion section:

Results from the 30- by 60-ft wind-tunnel aerodynamic interaction test showed that vectoring thrust acted like a blown flap by favorably affecting moment coefficients and unfavorably affecting force coefficients. This results in a favorable increase of up to 0.12 in pitching moment coefficient, and an approximately 0.1 decrease in lift coefficient. The results, using a low NPR of 1.3 and subcriticial exhaust, were correlated with plume deflection and not vane deflection to alleivate the low NPR effects.

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