# Is there drag in inviscid flow?

## Is there drag in inviscid flow?

In inviscid flow there is no drag due to normal stresses, that is, the pressure field. However, in viscous flow, as illustrated in Figure 9.1, the normal stresses contribute to form, or profile, drag. The fluid viscosity retards the flow near a surface through the action of frictional, or tangential, stresses.

## How do you find the drag coefficient?

The drag coefficient Cd is equal to the drag D divided by the quantity: density r times half the velocity V squared times the reference area A. The drag coefficient then expresses the ratio of the drag force to the force produced by the dynamic pressure times the area.

In fluid dynamics, d’Alembert’s paradox (or the hydrodynamic paradox) is a contradiction reached in 1752 by French mathematician Jean le Rond d’Alembert. D’Alembert proved that – for incompressible and inviscid potential flow – the drag force is zero on a body moving with constant velocity relative to the fluid.

### How do you reduce drag coefficient?

Methods of decreasing the drag coefficient of a vehicle include re-shaping the rear end, covering the underside of the vehicles, and reducing the amount of protrusions on the surface of the car.

### What is a potential flow Why is it called a potential flow?

In fluid dynamics, potential flow describes the velocity field as the gradient of a scalar function: the velocity potential. As a result, a potential flow is characterized by an irrotational velocity field, which is a valid approximation for several applications.

Why is there no drag in inviscid flow?

In inviscid flow there is no drag due to normal stresses, that is, the pressure field. However, in viscous flow, as illustrated in Figure 9.1, the normal stresses contribute to form, or profile, drag. The fluid viscosity retards the flow near a surface through the action of frictional, or tangential, stresses.

#### How is the induced drag coefficient ( CDI ) calculated?

The induced drag coefficient Cdi is equal to the square of the lift coefficient Cl divided by the quantity: pi (3.14159) times the aspect ratio AR times an efficiency factor e. Cdi = (Cl^2) / (pi * AR * e) The aspect ratio is the square of the span s divided by the wing area A. AR = s^2 / A

#### Which is the vorticity of an inviscid flow?

Many interesting inviscid flows (e.g. a uniform flow approaching a body) are initially irrotational, i.e. the vorticity, Ω, is everywhere zero: ω = ∇ x V = 0. Hence, by Kelvin’s theorem, such flows remain irrotational; † the flow is then referred to as potential flow and is associated with the velocity potential, ϕ, where V = ∇ϕ.

How to calculate the induced drag of a wing?

Cdi = (Cl^2) / (pi * AR * e) The aspect ratio is the square of the span s divided by the wing area A. AR = s^2 / A. For a rectangular wing this reduces to the ratio of the span to the chord c. AR (rectangle) = s / c. Considering the induced drag equation, there are several ways to reduce the induced drag.