난류경계층에서 벽마찰력과 유동방향 속도성분과의 상관관계(I)-시간 평균된 공간-시간 상관관계의 분석-

Correlation of the Wall Skin-Friction and Streamwise Velocity Fluctuations in a Turbulent Boundary Layer(I) -Analysis of Long-Time Averaged Space-Time Correlation-

A simultaneous measurement of the wall skin friction and near-wall streamwise velocity fluctuations is performed using hot film and hot wire anemometers to investigate the relation between them. Near-wall turbulence statistics measured with a hot-wire probe are in good agreement with previous results. Turbulence properties of the wall skin friction fluctuations measured with a hot film also show fairly good agreements with those measured by others except that rms level is lower in the present study. Long-time averaged space- time correlations show that the wall skin friction is highly correlated with a turbulence structure which is tilted from the wall in the streamwise direction. Tilting angles are obtained from the phase shifts between the wall skin-friction and streamwise velocity fluctuations. The convection velocity of the near-wall streamwise velocity obtained from the space-time correlation is in good agreement with that from the direct numerical simulation database.