Reactor simulation takes the heat
(page 3 of 4)
Too demanding
Fischer says the code his group is devising demands too much computational power for practical use in design programs. Instead, it will set standards for less demanding codes and will be compared against reactor experiments.
“With these high-fidelity simulations, we can with great confidence explore regions that have not been explored experimentally,” Fischer says. “We could get to data points that are different from the current designs.”
The unusual geometry created by the wire wrap, however, makes the simulation difficult. On top of that, the fluid moving past the rods typically is highly turbulent, and the large number of rods is hard to simulate without demanding enormous computer resources.
“We have this wire and the flow is skewed with respect to the wire,” Fischer says. “What we’re doing is setting up some rather simple calculations that basically look like a channel, plus a wire.”
To calculate what’s happening, Fischer’s group uses a spectral element algorithm. In essence, it sets up a grid of data points in the area being modeled and calculates what’s happening at each point at a particular time.
Researchers will compare the detailed calculations with other simulations that eliminate small phenomena in the fluid to cut the demand for computer resources. The comparisons will show whether the less demanding codes accurately depict heat transfer and fluid flow.
Conserving computer power is important. It takes 10 million data points to simulate heat transfer for one pin. Simulating a container of 200 pins would require 2 billion grid points – an enormous job, even for a supercomputer.
Fischer figures seven pins will require calculating about 100 million data points. That should be possible with the 1 million processor hours INCITE has allotted to the project.
