Tech Briefs

FSI of a Fuel Rod: Numerical versus Experimental Results

ADINA is widely used in safety studies in the nuclear industry. In this Brief, we show the use of ADINA FSI in the simulation of the dynamic response of a bar subjected to a force and released in a fluid flow field. The objective is to predict the effective damping of the bar, in a setup that simulates the behavior of a fuel rod in a nuclear reactor.

A 1.5 m long metal bar with a cross section of 8 mm x 20 mm is placed in a 3D fluid flow field. The bar is fixed at one end and pinned at the other end, and an initial force is applied at the center point to give a displacement of about 10 mm, as shown in Figure 1. The force is then instantly removed and the bar vibrates in the fluid flow. The dynamic response of the bar is sought.

Figure 1  Schematic of the problem, not to scale, of bar in a three-dimensional fluid flow field

The response of the structure, presented as the displacement of the central point of the bar, was obtained with different fluid flow velocity conditions. Figures 2, 3 and 4 show that the ADINA results compare very well with experimental data for still water, and for a flow velocity of 1 m/s and 3 m/s. The physical experiment was performed at Vattenfall Alvkarleby.

Figure 2  Displacement of center of bar, still water

Figure 3  Displacement of center of bar, flow velocity of 1 m/s

Figure 4  Displacement of center of bar, flow velocity of 3 m/s

In the movie above, we show the stress in the bar (upper band plot) and the pressure in the fluid (lower band plot) obtained using ADINA.

ADINA FSI was used to accurately predict the damped frequency response of the fuel rod. The effectiveness and accuracy of ADINA allows engineers to predict with confidence the effects of many loading conditions on, and systemic failures in, nuclear power plants in order to safely design these critical industrial applications.

For more information on ADINA FSI capabilities, refer to our web page on fluid-structure interaction capabilities of ADINA.

FSI, fuel rod, damping, oscillation, nuclear reactor, safety

Courtesy of Jan Sundqvist, ASUPPORT