Spectral analysis of pressure fluctuations on bluff bodies placed in turbulent flows

Pressure fluctuation around automobiles, airplanes and structures plays a major role in determining the noise levels and vibration problems. A new approach to obtain wall pressure fluctuations around bluff bodies placed in turbulent flows is described in this study. The spectral analysis of pressure fluctuation is performed in three steps. Three-dimensional Navier-Stokes equations are solved to get the mean flow quantities with the help of a two-equation model, k-&egr; model, as the first step. In the second step, the Poisson's equation for fluctuating pressure with both linear and non-linear turbulent interactions is solved by employing a turbulent velocity field synthesized from a stochastic description of the three dimensional turbulent motion. Time series for pressure fluctuations at each point in space are obtained as the result of the second step. The third step consists of the application of non-parametric estimation technique to analyze the obtained time series for fluctuating pressure in order to get pressure fluctuation spectrum. The validity of present model is confirmed by comparing the present results with the existing pressure fluctuation data for two-dimensional channel flow. Three different geometries (a 2-D channel, an automobile side window, and a cylinder) are considered for the present analysis. The versatility in grid generation technique used in present model permits the applicability of this model for any geometry to get the knowledge on pressure fluctuations. The accuracy of present model depends on the accuracy of statistical properties used to synthesize the turbulent velocity field that ultimately depends on the accuracy of the turbulent mean flow quantities.