Aerodynamics and Design for Ultra-Low Reynolds Number Flight
Aerodynamics and Design for Ultra-Low Reynolds Number Flight
Aerodynamics and Design for Ultra-Low Reynolds Number Flight
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Chapter 5<br />
The micro-rotor case that has been analyzed is a four-blade 2.5cm diameter rotor. The<br />
computational cost is reduced by assuming a steady-state flow-field <strong>and</strong> by<br />
implementing periodic boundary conditions on the blade entrance <strong>and</strong> exit planes of a<br />
single rotor segment. In spite of reducing the computational volume by one quarter, the<br />
computational grid still contains over five million grid points. The near-body grids<br />
comprise 40% of the cell count.<br />
The computational domain utilizes a Chimera overset grid topology with two cell<br />
minimum overlaps. One quadrant of the rotor is modeled in a domain extending five<br />
radii above <strong>and</strong> below the rotor plane <strong>and</strong> five radii out along the vertical inflow <strong>and</strong><br />
outflow planes. The near body grids consists of 250,000 grid points about the hub,<br />
180,000 grid points about the blade tip-cap, 520,000 grid points about the blade-hub<br />
intersection collar, <strong>and</strong> one million grid points about the blade itself, with 189 chordwise<br />
panels. The initial grid point spacing on the blade places at least 25 grid points within a<br />
laminar boundary layer at x/c=0.1. The resulting rotor model is pictured in Figure 5.13.<br />
The near-body grid geometry is depicted in Figure 5.14.<br />
92<br />
FIGURE 5.13 Computational Model of the four-blade 2.5cm diameter rotor.
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