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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Why is spanwise flow more prevalent in the boundary layer?
Spanwise flow is stronger in the boundary layer, but to me it's kind of counterintuitive because the BL flow is slowed down by friction, experiencing less of a pressure gradient over the wing, ...
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What causes lift?
Now this seems to be the question of the ages, and various questions on this site regards it.
The often told description of lift is that it is due to air traveling faster over the wing than under it, ...
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Does the air in the region of pressure recovery over a wing decelerate in the vertical axis?
In this answer, it states that the deceleration of air in the region of pressure rise over a wing acts in a direction perpendicular to the lines of relative chord, explaining spanwise flow.
To be ...
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Is this method to calculate a biplane's center of gravity using 57% of the biplane's gap and 23% of each wing's MAC correct?
Once you have the MAC for both wings and the CG balance point as a percentage of the MAC. connect the two CG positions with a line. Measure up between the wing Gap distance and place your center of ...
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Why does the nose pitch up during power reduction in a T-tail with rear mounted engines?
For the CRJ700 for example, reducing thrust causes a pitch up. Why is that?
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Are there any sources that contain information on the airfoils of the Boeing 737-500 and 737NG Aircraft?
I have found some information about this on airfoiltools.com (http://airfoiltools.com/airfoil/details?airfoil=b737a-il) but it doesn't specify the exact version of the aircraft, as the generations ...
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Why does the F/A-18 use external aileron and flap hinges?
As seen in the picture, the legacy Hornet uses ailerons and flaps with external hinges, and I was wondering what were the advantages of external hinges compared to flush hinges in the land-based ...
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Is this "separation" caused by the boundary layer?
I was wondering if the void seen in this picture (on top of airfoil, not the wake from the airfoil) is from the boundary layer thickening, or from the fact that as you go further back on an airfoil, ...
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Does the pressure recovery on the rear side of an airfoil recover all of the pressure?
I was wondering if all of the low pressure created by the airfoil gets recovered on the rear side of the wing. (I know during a stall or flow separation, this doesn’t happen, I think)
My main question ...
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Type of airfoil used by Briggs, Hull, and Dryden
What airfoil do Briggs, Hull, and Dryden use in NACA Report No. 207: https://ntrs.nasa.gov/api/citations/19930091273/downloads/19930091273.pdf
They mention it a few times:
"The airfoils tested ...
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How does more lift help during a stall (ex. flaps deployed) [duplicate]
How does more lift help in a stall? For flaps, I thought the effective increase in camber of the wing would make the wing have a higher AoA, therefore making a stall happen sooner.
Thanks!
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Why does a helicopter that uses the Coandă effect need a direct jet thuster aswell
Why does a helicopter that uses the Coandă effect instead of a tail rotor need a direct jet thruster as well. Why couldn't they just vary the pitch of the ducted fan used for the Coandă effect?
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How does Propeller windmilling work?
I’ve got a problem with understanding propeller windmilling. What I know is that when rpm are low and tas is high the blade aoa goes „over” the blade and is some kind of negative now, producing thrust ...
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Chord Wise Load Distribution
I'm looking for some guidance on how to compute the chord-wise lift distribution of the wing using Xflr5 or OpenVsp or any analytical method. This is for designing the internal structure of the wing.
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Why does the turn tighten in a Spiral Dive as it progresses? Even without applying any elevator control?
Why does the turn keeps getting tighter as the spiral dive develops?
Use of elevator control makes sense as it would increase the horizontal lift vector inside the turn. But even without any elevator ...
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How exactly does the startup vortex form, and why does it occur when circulation around the wing changes?
So I was wondering how exactly the startup vortex forms, why it dissipates, and where it's located in relation to the trailing edge of the wing. Also, why does a startup vortex form when circulation ...
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What are the effects of wing washout and anhedral on induced drag?
I am studying for my ATPL and was curious if and how induced drag varies based on wing anhedral and geometric washout.
I have a basic understanding that spanwise flow affects induced drag since there'...
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Is blade flapping "fully automatic"?
I have a rather simple question just to "double check" if I understood blade flapping right. So, I understand that a helicopter, in forward flight faces an asymmetric lift. Blade flapping is ...
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For a fixed density altitude, how does climb performance depend on pressure altitude?
Below is the climb performance from the 1978 Cessna 152 POH, which I've plotted as climb rate versus density altitude. It shows that higher pressure altitude gives decreased performance even when the ...
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Is there an aerofoil that gives reasonably good lift for both air flow directions: forward and backward?
Could an aerofoil be designed to give reasonably good lift for both flow directions?
I was motivated by this related question on Aviation SE: Can a plane fly backward if its propeller is in reverse?
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Deriving Accurate Exit air velocity of rotor
My goal is to derive the equation for exit air velocity as a function of:
Pitch angle
RPM
Rotor Radius
Constants like ρ
Assumptions:
Vc is relative velocity of air upstream, and is = 0
Inflow is ...
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Helicopter Basics: How does lead-lag of blades actually help in compensating for increase/decrease in speed due to flapping?
I understand the following -
Due to dissymmetry of lift, flapping up and down occurs.
Since angular momentum has to be conserved, the speed of blade increases/decreases during flapping
up/down ...
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Why does Aerodynamic Center move to 50% chord when supersonic?
There are several sources available that state that when an airfoil is fully supersonic, the Aerodynamic Center will move to the 50% chord location. Some of these sources, the ANA shown above being ...
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Pressure coefficient over a flat plate against its length/width ratio
We conducted an experiment to measure the surface pressure distribution around a flat plate (dimensions below). The plate has 104 equally distributed tappings as shown below.
Where the arrows ...
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How does speed and angle of attack affect pressure distribution at the wingtip?
So I was wondering how speed and AoA affect lift distribution at the tip of a wing. For example, if you are flying level and at a high speed, does that mean your wing has more even lift distribution ...
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Moving from 2D wing to 3D wing design
In terms of the design perspective of an Aircraft, once we decide on the airfoil that would be used for the wing, how would an Aerodynamics Engineer (or you) proceed to construct the wing? The ...
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Can an airplane propeller become supersonic?
Is it possible for an aircraft propeller to become supersonic?
I am not referring as for the aircraft, only the rotating blade.
I know it is extremely unlikely for a propeller plane to go supersonic, ...
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Sources for Python Codes to do some aerodynamic Calculations [closed]
I am currently working to design a wing. I basically want the Python code which would take the coordinates of the airfoil (.dat file), freestream velocity, Span (b), planform of the wing as input, and ...
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Do winglets change the lift distribution of a wing?
In this answer, it claims that the reason for lift decreasing at the wingtips is due to airflow around the wingtips. If I'm thinking correctly, that is due to the air below the wing spilling on to the ...
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Why don't modern military aircraft typically keep their guns covered?
Back in the 1940s, it was common to cover gun ports with tape. As well as improving streamlining, it would presumably help keep them clean.
Spitfire Mk 1, with all eight .303 inch Browning machine ...
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How does changes in Power vary the aerodynamic forces on an aircraft?
When we make changes to the Thrust by adding or removing power. In what way does it affect the other forces? As Power controls Rate of Climb or Descent of an aircraft, How is it acting on the other ...
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pressure wave propagation of shockwaves? [duplicate]
I can’t find a simple explanation of how the pressure waves propagate that leads to a shock over an aerofoil online.
How does this happen with upstream flow that is high speed but subsonic?
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How does a shockwave form from a subsonic upstream?
How does a shockwave form over say an aerofoil from a subsonic upstream?
Wouldn’t the flow have to be supersonic before it ‘shocks’?
Also, does the flow in a shockwave jump from let’s say it is at M=1....
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Why do newer engines have such wide fan blades?
Every treatise I read about propellers/fan blades/wings states that long, thin wings are more efficient than wide stubby ones.
So why is it that the blades in high-bypass turbofan engines fitted to ...
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What velocity is used to calculate maximum range and maximum endurance?
These are my data;
$C_{L_0} = 0.4$
$C_{L_{\alpha}} = 5.7$
$C_{L_{minD}} = 0.14$
$C_{D_{min}} = 0.022$
$k = 0.035$
$\alpha_{stall} = 15$
$S_{ref} = 20m^2$
Mass Data
$W_{total} = 2500 \text{ kg}$
$W_{...
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How does aspect ratio affect stall speed and stall AoA?
I've read a few answers on here but they didn't really tell me what I wanted to know. So I get that high AR wings will stall before low AR wings but what makes that true? Higher AR wings have a higher ...
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If in a coordinated turn, the horizontal lift vector is equal to the Centrifugal force. Then how is the aircraft still turning?
Image source
How does the Aircraft continue to turn when the both the Horizontal component of lift and the centrifugal force are equal?
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what is the cross section of an elevator and trailing edge flap?
Is the cross section of both a Trailing edge flap and elevator an aerofoil please or, like i've shwon in in image below? I tried to find a side view of an elevator and TE deflected to see this for ...
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What is monotonous and non-monotonous flow?
I'm not an engineering graduate so I'm learning as I go along. I've just read a sentence that states:
The transition shapes are identical, while the variety of growth rates of intermittency
are non-...
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How do I know which outer grid shape is best for CFD?
I’m looking into running a CFD simulation on an aerofoil in transonic flow (M=0.8) but am unsure about what external grid shape to choose for my computational domain?
I read into 3 main types:
C-grid
...
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If I know both Re number and Mach, how do I incorporate both into my simulation?
I’m trying to simulate an aerofoil based on experimental data with flow in the following conditions:
Mach=0.84
Reynolds number (Re) = 3*10^6
I wanted to keep my chord length at 1unit but then what ...
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Is the AOA on the horizontal stabilizer positive?
I am making a flight sim and would like some help.
If I am correct, the angle of attack on the horizontal stabilizer should look something like this:
aoa(Hstab) = aoa(Wing) - downwash + Hstab ...
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Why is it that when autopilot is maintaining cruise, we don’t feel the changes when lift increases?
When we’re inside an aeroplane, when we’re in cruise, why is it that we don’t feel the changes in altitude, lift and the adjustments for example from the elevator on the plane as the weight is burned ...
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How is an airliner trimmed nose-down or up? [duplicate]
so when a plane is in cruise, it loses weight and then the weight begins to exceed lift.when this happens, the plane begins to climb.
My question is this please:
The plane would be trimmed up or down ...
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What is aeroplane trim and how does it control/adjust the elevator in cruise?
so in my last question, ‘trim’ popped up a lot and after reading up on it I got this: it’s used to adjust the forces on the control surfaces so that the aircraft maintains like a set input
But what I ...
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How do Antishock Bodies / Cuchemann Carrots delay shock-induced flow separation?
There are several online resources that describe these aerodynamic devices as either "Antishock Bodies" or "Kuchemann Carrots" and that they are used to produce some combination of ...
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"Pure" Aerospace engineering vs mechanical engineering/pathway aerospace?
Does "pure" aerospace engineering give better aero-knowledge then mechanical engineering/pathway aerospace?
What is point of specialization aerospace at mechanical engineering, isn't ...
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How to find the location of the Aerodynamic centre?
Everywhere I look I'm only able to find information about airfoils.
How do I find out the location of the Aerodynamic centre of an arbitrary aircraft irrespective of its type or shape?
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What are the effects of whiteout (snow) and brownout (sand/dust) on helos?
Is there any other effect besides low visibility?
Both seem to show very similar conditions.
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Why is a flat turn less efficient than a coordinated turn?
How I understand a flat (rudder-only) turn:
AOA between relative wind and the fuselage of the airplane causes a sideslip in the direction of yaw.
Vertical stabilizer weathervanes into the relative ...
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