Numerical simulation of separated flows past bluff bodies
Abstract
The steady twodimensional flow past bluff bodies is simulated numerically using a hybrid EulerianLagrangian model. The boundary layer effects, such as the location of the separation points and the rate of the generation of vorticity, are determined by a boundary layer solver. This solver uses Prandtl's boundary layer equations transformed by the FalknerSkan transformation and then solved using a cubic spline approximation and a mean weighted residual technique. The vorticity generated at separation is discretized into elemental point vortices and convected downstream into the wake in a Lagrangian manner. The wake is modeled in a finite Eulerian computational domain using a modified CloudinCell (CIC) method. The velocity field at each time step is obtained as a solution to the rotationality condition using the finite element method in a cartesian mesh with ninenode elements and biquadratic shape functions. The biquadratic shape functions introduce a higher order interpolation scheme for the distribution of the vorticity at the nodal points than the bilinear (area) interpolation used in the original CIC method. The higher order interpolation as used in the CIC formulation performs better than the bilinear interpolation of the original method. This is demonstrated by the simulation of an isolated Rankine vortex. The ability of the CIC method to simulate the dynamics of vortex structures is also tested for the cases of flow past a flat plate and a circular cylinder.
 Publication:

Ph.D. Thesis
 Pub Date:
 December 1986
 Bibcode:
 1986PhDT........15A
 Keywords:

 Bluff Bodies;
 Boundary Layer Equations;
 Computational Fluid Dynamics;
 EulerLagrange Equation;
 Flow Equations;
 Separated Flow;
 Two Dimensional Flow;
 Vorticity;
 Aerodynamic Drag;
 Boundary Layers;
 Circular Cylinders;
 Computational Grids;
 Flat Plates;
 Interpolation;
 Lift;
 Spline Functions;
 Vortex Shedding;
 Vortices;
 Fluid Mechanics and Heat Transfer