MEASUREMENT OF TURBULENT FLUCTUATIONS OF VELOCITY GRADIENT ON THE WALL WITH A PAIR OF SEMICIRCULAR ELECTRODES

Measurement of turbulent fluctuations of vclocity gradient on the wall is important for thorough understanding of turbulence structure, mass transfer and heat transfer in the vicinity of the wall. This paper describes the principle of electrochemical technique as well as the measurement of two-dirnensional fluctuations of velocity gradient with a pair of semicircular electrodes. In a fully developed turbulent pipe flow with pipe diameter of 0.194 m and with a solution of iodine and potassium iodide as flow medium, the measured axial and transversal turbulent intensities of velocity gradient at the wall arc 0.3-0.33 and 0.11 0.12 respectively.