Rotation of Greek Cross Cylinder

To validate the capability of Flow Simulation to simulate the rotation by using the Local region(s) (Sliding) option, let us consider a rotating cylinder of a Greek cross section with axes perpendicular to the direction of motion and determine the air force acting on the rotating cylinder.

The model was tested at an airspeed of 10 m/s in infinite length-diameter ratio; cross-sectional dimensions are shown in Figure 1. The results of its experimental study are given in Ref. 20.

Figure 1. Cylinder cross-section.

The experimental data consist of drag and lift forces as functions of the ratio of peripheral to translation speed:

where U´ is the peripheral speed, U0 is the airspeed, ω is the rotation speed, L is the ‘lift’ or the cross-wind force, D is the ‘drag’ force, q is the dynamic pressure and S is the projected area of the cylinder.

For the calculation, a time-dependent analysis with the constant time step from 1/160 of the rotation period for ω ≤ 1000 rpm up to 1/80 of the rotation period for ω > 1000 rpm has been performed on the 100x80x1 computational mesh. The flow fields at ω = 300 rpm and ω = 2000 rpm are shown in Figure 2 and Figure 3 respectively.

Figure 2. Flow field at ω = 300 rpm.

Figure 3. Flow field at ω = 2000 rpm.

The aerodynamic coefficients, which were predicted by Flow Simulation and compared against the experimental data (see Ref. 20), are shown in Figure 4 and Figure 5.

Comparison of the aerodynamic coefficients shows that Flow Simulation predicts the rotation effects with good accuracy.

Figure 4. The lift coefficient predicted by Flow Simulation and measured experimentally.

Figure 5. The aerodynamic coefficients predicted by Flow Simulation and measured experimentally.