Pressure Measurements in Jet Diffusion Using a Developed Hot-Wire Static Pressure Sensor

Abstract

The aim of this experimental study is to investigate the diffusion of jets, with particular attention focused on the relationship between the static pressure and the stream wise mean velocity on the development of a two-dimensional air jet. A jet with three injection Reynolds numbers (Re=1.0×104, 2.0×104, 3.0×104) was generated in a two-dimensional wind tunnel. The velocity distributions were measured by an X-type hot-wire anemometer. The static pressure distributions were measured by a static pressure probe developed in our laboratory, which incorporates a hot-wire anemometer. There are two important characteristics for the hot-wire static pressure probe. The one is that mean static pressure and the static pressure fluctuation can be measured at the same time. The other is that the probe is not affected by the flow and the changes of physical properties (thermal conductivity) of gases, because the sensing hot-wire is always in the air bias flow. The sensitivity of the fstatic pressure probe is 92.3 mV/Pa. The frequency response is flat from 16 Hz to 2.5 kHz. As a result of the experiment, it was found that negative static pressure exists in the turbulent shear layer. It is considered that the entrainment processes from the negative static pressure by the vortex structure motion of the turbulent shear layer.