Measurement and Interpretation for the Turbulent Flow Wall Pressure Field of a Dilute Polymer Solution Within a Rectangular Channel Containing Smooth Walls.

摘要

Measurements of the one and two-point spectral statistics of the wall pressure field were conducted within a smooth-wall turbulent channel flow containing both Newtonian (water) and non-Newtonian liquids. The test section of the channel was located far enough downstream to insure fully developed turbulence and the high aspect ratio of the channel (1 8: 1) provided homogeniety of the flow in the transverse direction. Single component laser Doppler velocimetry (LDV) measurements were conducted in both the Newtonian and non-Newtonian cases in order to validate the channel kinematics and aid in the interpretation of the pressure fluctuation statistics. Reynolds number effects were examined and compared to similar experimental results in the literature. Recently developed signal processing techniques were utilized to enhance the statistical quality of the wall pressure field at low frequencies and those results pertaining to the polymer flow regime are believed to be the first of such high quality. The most interesting feature indicated from the pressure statistics is the loss of information at high frequencies which contain eddies at the smallest scales. Furthermore, the pressure spectra scaled on outer variables suggest that the limits on this smallest scale can be related to the relaxation time of the polymer molecule. At the present time, it is believed that non-Newtonian fluids primarily affect the production of turbulence energy. However, results from the single point pressure statistics suggest that polymer flows enhance a fluid's ability to dampen out turbulence via dissipation. .... Noise cancellation, Channel flow, Turbulent flow, Wall pressure, Dilute polymer solutions, Drag reduction.