Building Internal Pressure: Sudden Change

The change of the internal pressure of a building caused by the sudden opening of a window or door under the action of wind is analyzed using the Bernoulli equation of fluid mechanics. The problem is treated at several levels of sophistication, from the simplest quasi-steady isothermal incompressible solution to the most complex solution assuming unsteady isentropic compressible flow with due regards to the inertia effect. Following the break of a window or door by wind, the internal pressure reaches the external pressure at the opening rather rapidly. After the internal pressure has reached the external pressure, there is an overshoot and subsequent oscillation of the internal pressure, in spite of the constancy of the external pressure under a steady wind. The results are compared to solutions obtained from the Helmholtz resonator model of acoustics.