Numerical simulation of the flow in wire-wrapped pin bundles: Effect of pin-wire contact modeling

The rapid advancement of numerical techniques and the availability of increasingly powerful supercomputers recently enabled scientists to use large eddy simulation (LES) to simulate numerically the flow in a full subassembly composed of wire-wrapped pins. Because of the extreme computational cost of such simulations, it was not possible to conduct a sensitivity case on the pin-wire interface modeling. Since such calculations are likely to be extended to conjugate heat transfer, however, a sensitivity study is necessary to assess the reliability of the numerical results. It is well known, for example, that conjugate heat-transfer results are often strongly influenced by near-wall modeling. The objective of the present work is to investigate the effect of pin-wire contact modeling from the point of view of both the hydraulics and the heat transfer characteristics. In particular, the focus is on the prediction of the hot spot in conjugate heat-transfer calculations. The primary test case is the simplified geometry recently proposed by Ranjan et al., which consists of a simple channel flow with a wire embedded in one of the walls. After reproducing the results using the LES code Nek5000, we examined several other choices for the wire-pin interface modeling, including the introduction of a nominal gap between the wire and wall. The results shed light on the sensitivity of CFD calculations results to the modeling of the interface region between wires and pins.