Measurements of Pressure Fluctuation in the Wake of Cylinder

抄録

With a view to observing pressure fluctuations in turbulent flow of fluid, a new apparatus was constructed by using a condenser microphone as a transducer with a ratio-discriminator. The frequency response of the apparatus was calibrated by means of Kármán vortices produced by a circular cylinder. The Helmholtz resonance and the loss in the pressure duct were compensated electrically by a band-rejection filter and a high-frequency booster. By these devices, the overall frequency response of the pressure-measuring apparatus was made flat between 50 and 1500 cycles per second. Using the apparatus in combination with a single rotary type hot-wire anemometer, it proved succesful in determining the intensity of static pressure fluctuation as well as the correlation between pressure and velocity fluctuation. Consequently all the terms in the energy equation became measurable, and the energy equation for the fluctuating quantities was ascertained experimentally for the first time in the wake of a circular cylinder, 1 cm in diameter, placed in an airstream of the speed 14 m/s, at a section 42 times the cylinder diameter downstream.