A wind tunnel is used to measure the pressure distribution in the airflow over an airplane model (Fig. P7–33). The air speed in the wind tunnel is low enough that compressible effects are negligible. As discussed in Chap. 5, the Bernoulli equation approximation is valid in such a flow situation everywhere except very close to the body surface or wind tunnel wall surfaces and in the wake region behind the model. Far away from the model, the air flows at speed V_∞ and pressure P_∞, and the air density ρ is approximately constant. Gravitational effects are generally negligible in airflows, so we write the Bernoulli equation as

Nondimensionalize the equation, and generate an expression for the pressure coefficient C_p at any point in the flow where the Bernoulli equation is valid. C_p is defined as

FIGURE P7–33

Transcribed Image Text:

P + 1/ PV² = P ₁ + 1/2 PV ²/0