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In aerodynamics, aerodynamic drag, also known as air resistance, is the fluid drag force that acts on any moving solid body in the direction of the air's freestream flow. [ 22 ] From the body's perspective (near-field approach), the drag results from forces due to pressure distributions over the body surface, symbolized D p r {\displaystyle D ...
drag force F d. Using the algorithm of the Buckingham π theorem, these five variables can be reduced to two dimensionless groups: drag coefficient c d and; Reynolds number Re. That this is so becomes apparent when the drag force F d is expressed as part of a function of the other variables in the problem:
Drag coefficients in fluids with Reynolds number approximately 10 4 [1] [2] Shapes are depicted with the same projected frontal area. In fluid dynamics, the drag coefficient (commonly denoted as: , or ) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water.
A particular aircraft may have different curves even at the same R e and M values, depending for example on whether undercarriage and flaps are deployed. [2] Drag curve for light aircraft. C D0 = 0.017, K = 0.075 and C L0 = 0.1. The tangent gives the maximum L/D point. The accompanying diagram shows C L against C D for a typical light aircraft.
For Reynolds numbers below about 1 the dependence is linear, above 1000 (turbulent flow) it becomes quadratic. In air, which has a kinematic viscosity / around 0.15 cm 2 /s, this means that the drag force becomes quadratic in v when the product of object speed and diameter is more than about 0.015 m 2 /s, which is typically the case for ...
The aerodynamic force is the resultant vector from adding the lift vector, perpendicular to the flow direction, and the drag vector, parallel to the flow direction. Forces on an aerofoil . In fluid mechanics , an aerodynamic force is a force exerted on a body by the air (or other gas ) in which the body is immersed, and is due to the relative ...
Consider fluid flow around an airfoil. The flow of the fluid around the airfoil gives rise to lift and drag forces. By definition, lift is the force that acts on the airfoil normal to the apparent fluid flow speed seen by the airfoil. Drag is the forces that acts tangential to the apparent fluid flow speed seen by the airfoil.
A force arrow should lie along the line of force, but where along the line is irrelevant. A force on an extended rigid body is a sliding vector. non-rigid extended. The point of application of a force becomes crucial and has to be indicated on the diagram. A force on a non-rigid body is a bound vector. Some use the tail of the arrow to indicate ...