Why does drag coefficient decrease with increasing velocity?
As the velocity increased you induced turbulent conditions which caused the flow to re-attach or the separation point to move further to the rear reducing the loss due to the separation. So, the drag coefficient fell.
Does drag coefficient decrease with velocity?
Drag force is proportional to the velocity for low-speed flow and the squared velocity for high speed flow, where the distinction between low and high speed is measured by the Reynolds number. Drag forces always tend to decrease fluid velocity relative to the solid object in the fluid’s path.
Does drag coefficient change with Reynolds number?
Note that the drag coefficient decreases with the Reynolds number, and it becomes almost a constant (CD = 0.4) for a Reynolds number between 103 and 2×105. Hence, a turbulent boundary layer develops as fluid flows past an object will reduce the drag force.
What is drag coefficient in aerodynamics?
The drag coefficient is a number which aerodynamicists use to model all of the complex dependencies of drag on shape, inclination, and some flow conditions. The drag coefficient Cd is equal to the drag D divided by the quantity: density r times reference area A times one half of the velocity V squared.
Why does the drag force on a bullet decrease with velocity?
The drag force on the bullet does not really go down. It basically increases with the -square- of the velocity. Only after this is computed, the drag coefficient is applied to cater for the variation from pure quadratic drag increase. Take for example a bullet that has a cd of 0.660 at 1600 fps and 0.607 at 2200 fps (cd goes down).
How does the friction drag coefficient change on a flat plate?
In the case of a flat plate, the growth of the boundary layer is accompanied by a decrease in the velocity gradient at the wall. This results in a decrease of the wall shear stress and thus a reduction of the friction. The friction drag coefficient is therefore by no means a constant quantity, but depends on local conditions.
How does shape affect the amount of drag produced?
Shape has a very large effect on the amount of drag produced. Comparing the flat plate and the prism, and the sphere and the bullet, we see that the downstream shape can be modified to reduce drag. The drag coefficient for a sphere is given with a range of values because the drag on a sphere is highly dependent on Reynolds number.