Aerodynamic Drag: Turbulent Flow & Exchange of Momentum

  • Thread starter Thread starter fatlady1ac
  • Start date Start date
  • Tags Tags
    Drag
AI Thread Summary
Turbulent flow significantly increases aerodynamic drag due to momentum exchange between slower and faster-moving particles, with drag increasing by an order of magnitude during this transition. Friction drag, resulting from viscous effects, is higher in turbulent flow due to steep velocity gradients. Pressure drag, influenced by the shape of an object, remains constant regardless of flow type, although a turbulent boundary layer can reduce form drag by preventing flow separation. Wave drag occurs at supersonic speeds and is not directly affected by turbulence. Understanding these dynamics is crucial for optimizing aerodynamic performance.
fatlady1ac
Messages
17
Reaction score
0
Does turbulent flow create more drag due to the exchange of momentum between the slower moving particles and faster moving particles?
 
Physics news on Phys.org
Yes. The drag goes up by roughly an order of magnitude when the flow transitions to turbulence.
 
From what I understand, there are multiple types of drag that come into play with turbulent flow. Friction drag arises due to the viscous effects of the fluid. Since the turbulent flow profile has such a large change from the free stream velocity to zero over a very short distance (du/dy is large), it causes a larger friction drag than would a laminar flow profile. Pressure drag is created by a pressure difference due mainly to the shape of a body and how the flow profile changes over the shape of the body. If the flow over the body at any point is turbulent enough to considered supersonic, you get wave drag.
 
timthereaper said:
From what I understand, there are multiple types of drag that come into play with turbulent flow. Friction drag arises due to the viscous effects of the fluid. Since the turbulent flow profile has such a large change from the free stream velocity to zero over a very short distance (du/dy is large), it causes a larger friction drag than would a laminar flow profile.

This is true, and is the physical reason the drag is greater.

timthereaper said:
Pressure drag is created by a pressure difference due mainly to the shape of a body and how the flow profile changes over the shape of the body. If the flow over the body at any point is turbulent enough to considered supersonic, you get wave drag.

Pressure drag (or form drag) remains the same regardless of whether the ball is laminar or turbulent. The only real exception is when a boundary layer is turbulent which prevents it from separating (as in a golf ball) in which case the form drag actually decreases. However, this is not a direct result of turbulence, but a secondary result due to a turbulent boundary layer's tendency to remain attached.

The concepts of turbulence and supersonic flow are disjoint and have nothing to do with one another. Wave drag has nothing to do with turbulence and turbulence will not do anything to change the amount of wave drag you get on a supersonic vehicle.
 
I guess I said that last one wrong. I only meant that at supersonic speeds that wave drag appears.
 
Thanks for all the replies.
 

Thread '1:1 versus 2:1 Mechanical Advantage debate'

The rope is tied into the person (the load of 200 pounds) and the rope goes up from the person to a fixed pulley and back down to his hands. He hauls the rope to suspend himself in the air. What is the mechanical advantage of the system? The person will indeed only have to lift half of his body weight (roughly 100 pounds) because he now lessened the load by that same amount. This APPEARS to be a 2:1 because he can hold himself with half the force, but my question is: is that mechanical...
View full post »

Thread 'Newton's first law?'

Some physics textbook writer told me that Newton's first law applies only on bodies that feel no interactions at all. He said that if a body is on rest or moves in constant velocity, there is no external force acting on it. But I have heard another form of the law that says the net force acting on a body must be zero. This means there is interactions involved after all. So which one is correct?
View full post »
Thread 'Beam on an inclined plane'

Thread 'Beam on an inclined plane'

Hello! I have a question regarding a beam on an inclined plane. I was considering a beam resting on two supports attached to an inclined plane. I was almost sure that the lower support must be more loaded. My imagination about this problem is shown in the picture below. Here is how I wrote the condition of equilibrium forces: $$ \begin{cases} F_{g\parallel}=F_{t1}+F_{t2}, \\ F_{g\perp}=F_{r1}+F_{r2} \end{cases}. $$ On the other hand...
View full post »

Similar threads

Golf ball and Tennis ball turbulence
Replies
7
Views
4K
How increased mass and drag affect speed
Replies
1
Views
2K
B Some Questions About Drag (for ships in water and airplanes in air)
Replies
5
Views
2K
Is Turbulence Necessary for Lift on a Wing?
2
Replies
61
Views
5K
Aerodynamics: flow separation's effect on lift and drag
Replies
4
Views
3K
I Drag equation - relative flow velocity
Replies
11
Views
3K
Difficulty Understanding 'Drag Crisis' (transitionary period from laminar to turbulent flow)
Replies
1
Views
910
I Force applied on sphere by turbulent flow
Replies
28
Views
2K
Why do we add turbulence to the rotating water in our experiment?
Replies
10
Views
2K
Why does Cd increase until Mach1 while drag force increases?
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top