Questions tagged [aerodynamics]

Aerodynamics is the study of how air moves and interacts with solid objects. It is an essential part of aircraft design.

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How does the pressure distribution at the blades of a radial turbocharger look like?

Consider a piston engine equipped with a turbocharger. In the turbine section of the turbocharger, the pressurized exhaust airflow comes from the center (radially) to the blades, then changes ...
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Does use of flaps or ailerons affect the aerodynamic forces distribution on the wing area before them?

Assume I want to use the flaps or ailerons at a specific altitude for some maneuevers on an aircraft. We know that the overall aerodynamic forces like lift and drag on an aircraft wing will change ...
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How can a small airflow that passes through a slots redirect all the outer flow?

If this is normal wing without slots behind wing will be huge wake; airflow will separate, which is very easy to predict. Why would the outer flow follow the wing's couture; how can a small airflow ...
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Can pitot tube measure boundary layer? Why? [closed]

Can pitot tube measure boundary layer? Why? Why not?
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Assuming a descent at 250kt IAS and idle thrust, will the resulting ROD be higher at a higher GW, or lower? [duplicate]

I was recently told by a pilot that it works in inverse order: Keeping indicated airspeed steady, and using idle thrust, the rate of descent will be lower with a higher gross weight (and a higher rate ...
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Does the optimum LRC speed increase or decrease as the GW of the aircraft decreases during a long range flight?

I do not know what defines the optimum LRC speed for each aircraft, aeronautically speaking. I suspect it has something to do with optimum AoA but even then I am not sure if the LRC speed should ...
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Why is aspect ratio important to pilots?

Aspect ratio is mentioned in chapter 1 of AFM .. why do pilots need to know this and its specific value; what should a pilot derive from that value?
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Does the nacelle strut experience reaction forces due to lift, drag, thrust, weight of engine during cruise flight?

Cruise flight indicates that total lift and weight of aircraft cancel and thrust forces generated cancels with total drag forces. However, I am looking closely at the nacelle instead of the whole ...
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Can I just differentiate my Euler rates to get the angular rates?

There is this matrix: $${W_{\eta}}=\begin{bmatrix} -\sin(\theta) & 0 & 1 \\ \cos(\theta) \sin(\phi) & \cos(\phi) & 0 \\ \cos(\theta) \cos(\phi) & -\sin(\phi) & 0 \end{bmatrix}$...
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How to calculate drag of a flat rectangular surface at given area, air density, airspeed and angle of attack?

I'm a complete noob in aerodynamics, and I'm trying to calculate the drag of a rectangular flat area, given the air pressure / density, area, angle of attack and airspeed. I've read this question, but ...
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In a banked turn, why does the center of gravity, rather than the center of lift, follow the path of a circular arc?

I'm a post-solo student pilot who sometimes gets hung up on fundamental points of aerodynamics. "As long as the aircraft is banked, the side force is a constant, unopposed force on the aircraft. ...
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Is it possible to have a separated boundary layer without having reversal flow?

To fix the ideas, let's consider an airfoil instead of a generic shape. As far as I understand, the separation of the boundary layer takes place after there is a region of reversal flow on the suction ...
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What happens to the assumption ∂p/∂y≈0 in the region of separated boundary layer? is it still valid?

I am reading about Boundary Layer(BL) and seems that in the derivation of the governing equations there is an assumption that the pressure, $p$, in $y$ direction is constant, that is: $${\partial p \...
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What effect does towing a glider have on the stall speed of the tow plane?

I can see that if the tow is perfectly aligned with the axis of the engine thrust, that it is equivalent to pure parasitic drag and similar to some reduction of thrust. However, in the real world the ...
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OV-10 Bronco using airbrakes to fight adverse yaw?

Watching this Bronco display, perhaps this is an incorrect observation, but it looks like the airbrakes are independently used to counteract adverse yaw. What is the domain of use for these airbrakes? ...
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How would flying into Frankfurt a.M. Airport be problematic for the Tu-154?

A friend of the family lives in the approach path of Frankfurt a.M. Airport (FRA, EDDF). Until a few years ago, Tupolev Tu-154s were still flying to this airport, although as I understand, they don't ...
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How to turn inviscid data to viscous?

I have used Panel method to calculate Cp vs x/c graph and CL. But as panel method assumes attached flow it does not give an flow separation and thus in CL vs alpha graph I could not find any stall. My ...
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What is the purpose of the tiny doors used by the 787's laminar control?

The recent Oct 2021 YouTube video (The Insane Engineering of the 787 by Real Engineering) in the related question remarks: [...] tiny doors whose purpose are a mystery to me with little to no ...
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Why aren't HLFC panels mounted on wing?

I watched The Insane Engineering of the 787 by Real Engineering. He just gave short detail about the HLFC(Hybrid Laminar Flow Control) panel and mentioned their purpose isn't available online. I found ...
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Does thickness of boundary layer rise with AoA?

When increasing the angle of attack, the Cl and adverse pressure gradient rise. Does boundary layer thickness rise as well? Or has an airfoil with higher Cl a thicker boundary layer?
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Why is the CG assumed to be between the CP and the tail?

While discussing stability (Longitudinal, Lateral, Directional), invariably, all texts assume CG to be between CP and tail. Ex: Look at the specific image in wikipedia https://en.wikipedia.org/wiki/...
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Does $C_d$ change with speed? [closed]

In aircraft drag calculations, drag D is computed as $ D = C_D \cdot \frac{1}{2} \rho V^2 \cdot S$, with $C_D$ a dimensionless factor determined by the "streamline shape" of the measured ...
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Why do fixed slats have a cusp?

Reading this about slat cove filler meant to reduce aeroacoustic noise, it seems there is no big difference in lift if the cove filler is deployed or not. I understand the shape of a retractable slat ...
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When pitching, how do planes establish a pitch rate which corresponds to the centripetal acceleration?

Coordinated flight requires that the yaw rate and the centripetal acceleration correspond. In other words, for a given $a_{centripetal} = v^2/r = \omega ^2 r$ this means that the yaw rate must equal $\...
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What are the effects of increasing Wing Aspect Ratio?

I can think of only 2 effects that is The Induced Dag would Reduce with increasing AR of wing. This goes by the simple formula: $$ C_{d(i)} = \frac{K \times C_l^2}{\pi \times \text{AR}} $$ As drag ...
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6 votes
1 answer
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Charger vs Bronco horizontal stabilizer volume?

While watching this video on the Convair Model 48 Charger, I was surprised by the dimensions of the horizontal stabilizer. Compared to the North American OV-10 Bronco, which is relatively similar in ...
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4 votes
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What is the maximum control surfaces deflection on a Cessna 210N?

Does someone know how far the control surfaces (rudder, ailerons, elevator and nose gear) can deflect in a Cessna 210N? I've been searching Google and the POH for hours now and can't find it.
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3 votes
1 answer
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How does the stick force and behaviour of aircraft relate to the CG locations?

I'm struggling with developing an intuition for flight behaviour and stick force with CG locations. Assuming conventional wing and tail configuration, When the CG is moved from aft to forward, the ...
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How to calculate how much horsepower is needed to negate wing tip vortices with a wing tip prop?

How to calculate how much horsepower is needed to negate wing tip vortices with a wing tip prop? I understand 80% of drag is at the wing tips. Source: Xflaero software notes. I understand NASA's X-57 ...
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Is NASA's X-57 using a fan, a prop, or a prop/fan and what is the difference visually/physically?

Is the NASA's X-57 or the Opener BlackFly using a fan, a prop, or a prop/fan and what is the difference visually/physically? NASA X-57 Maxwell, courtesy of Wikipedia Opener BlackFly v3 courtesy of the ...
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Do aircraft usually fly with CG at 50 percent of chord or do I need to reduce the tail volume?

I'm working on a design having a 3.2-metre wing with a constant chord section in the middle and taper on the sides. With a tail volume of about 0.68, the neutral point is at 60% chord from the leading ...
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15 votes
6 answers
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Why aren't takeoff flaps used all the way up to cruise altitude?

In general aviation aircraft such as Diamond star DA-40, flaps to take-off are used until 500ft AGL and speed before retracting flaps is Vy (best ROC speed)-67kts and after retracting flaps is 80kts. ...
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1 vote
1 answer
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I have a projectile going through the air, point in front, flat plate in the rear. How do I calculate the aerodymanic forces on the rear plate? [closed]

The project that the projectile is being developed for has nothing to do with aerodynamics, but the problem is that the rear plate is being sucked off - obviously not attached sufficiently. How can I ...
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I don't quite understand the derivative in this vertical wind gust formula

First my english writing skill is still bad so pardon me if i accidentally made any mistake TT-TT. So recently I have learnt about how the vertical gust affect the load factor and the calculation ...
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1 vote
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Variables of Dryden Wind Model

How to determine the turbulence intensities (σu, σv, σw), scale lengths (Lu, Lv, Lw) & Angular frequency (ω0) in the given Dryden wind model to generate wind speeds (u_w, v_w, w_w) of civil jet ...
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Does the Prandtl-Glauert correction use the airplane's Mach number, or its effective Mach number corrected for sweep?

The Prandtl-Glauert correction adjusts the lift curve slope of an airfoil to different Mach numbers. Should the Mach number of the airplane be used or the effective Mach number that the leading edge ...
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5 votes
2 answers
260 views

Will air accelerate over a wing and generate lift, if the air has zero viscosity? [duplicate]

Will air accelerate over a wing, if the air has zero viscosity? Will the wing produce any lift under these conditions?
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Streamline Curvature Theorem applied to Airfoils?

I am new to studying aerodynamics and taking up aeromodelling and am currently learning how lift is obtained in-depth. When studying the two common explanations as to how lift is generated by an ...
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4 votes
1 answer
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Is all the extra lift from flaps added upstream where the spars sit?

Flaps can significantly increase the lift for a wing, is all that extra lift added upstream where the spars sit? I ask this question because the flaps in airliners seem to be only connected by a few ...
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How would you adjust C_l airfoil values for different Reynolds numbers?

I have graph of C_l (airfoil lift coefficient) as a function of AoA, for Mach 0.7 and Re = 6x10^6. For a given value of C_l, what would be a good way to estimate that value at a different Reynolds ...
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3 votes
3 answers
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How do thick and thin airfoils compare in lift generation?

I find myself confused when comparing the lift generation amongst Thick and Thin Airfoils. A paper to which I have added reference below claims that thin airfoils are better in generating lift because ...
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1 vote
3 answers
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With 77% less wing area than the Lazair Ultralight, how does the Blackfly meet FAA ultralight category requirement of power off stall speed of 28mph?

With 77% less wing area, how does the Opener BlackFly do a power off stall at less than 28mph (or fly with no power at 28mph)? I understand the Lazair with 140 sq ft of wing area, was able to fly at ...
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Is the compressor required on jet engines? Can air be rammed into the turbine?

In the context of a common airliner (say Boeing 777), when the airplane is on the ground, and the turbines are on, air is getting sucked in and compressed/bypassed. The engine has to do work to ...
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1 answer
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Are shrouds and stators needed to maximize thrust from stacked props and motors in electric aircraft like the Lilium Jet?

Do some e-vtol aircraft, like the Lilium need shrouds and stators to maximize thrust from stacked electric motors and props? The aircraft is actually called the Lilium Jet, although it does not heat ...
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Why do low pressure arrows point away from the surface if the pressure/air cannot pull/suck?

Pressure is always positive, so at the upper part of a wing pressure is positive as well, just lower than the free stream, but still PUSHes on wing surface, not PULLs. Words like pull or suction don't ...
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4 votes
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Is there a name for the fast decline + pull to climb pattern?

I'm a hobby photographer and I've noticed some patterns in the bird flights, so I tried to poke a bit into the aviation terminology for it. Phalacrocorax carbo does this movement similar to the ...
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2 votes
2 answers
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Do all Fuselage sections have same performances?

The Burnelli machines had an airfoil shaped fuselage; some indicate near 10% of lift in a 21 century airliner comes from fuselage; 'Flying Wing' concept is old, and still attracts many; bottom of ...
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What are the relations between Angle of attack and Calibrated Airspeed?

I would like to estimate Angle of Attack using trigonometric relations i.e AoA = arctan (w/u) airspeed components (i.e u, v, w). When I am considering body 'x' velocity ('u' component), is it ...
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9 votes
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Why are there two local maximums on some CL vs AOA curves?

I know what a stall is but I don't understand why there are in some cases two local maximums on the $C_L$ vs AOA curve of some airfoils. What is the reason for the mini stall that occurs before the ...
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Does form drag require skin drag?

Theoretically, if there was sphere with zero skin drag, would that make form drag nonexistent? If fluid could flow around symetric object whose shape doesnt generate any lift without any skin friction,...
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