Impinging Circular Turbulent Jets

The normal impingement of turbulent circular jets on smooth walls is studied both experimentally and analytically. This type of flow can be divided into three distinct flow regions: the free-jet region; the impingement region; and the wall-jet region. The impingement region is the most important. It is shown that the impingement region occupies about 14% of the impingement height above the wall, whereas it extends about 22% of the impingement height radially. Semi-empirical methods to predict axail variations of velocity and static pressure are developed. Similarity of velocity and static pressure profiles is investigated and it is shown that these profiles are well described by the Gaussian error function. Variation of pertinent length scales are obtained empirically using dimensional analysis so that the time-averaged velocity and pressure fields in the impingement region can be predicted. A method to predict the wall shear stress in the impingement region is developed.