Pressure Fluctuation Characteristics of Complex Turbulent Flow in a Single Elbow With Small Curvature Radius for a Sodium-Cooled Fast Reactor

Abstract

A multi-elbow piping system is adopted for the Japan sodium-cooled fast reactor (JSFR) cold-legs. Flow-induced vibration (FIV) is considered to appear due to complex turbulent flow with very high Reynolds number in the piping. In this study, pressure measurement for a single elbow flow is conducted to elucidate pressure fluctuation characteristics originated from turbulent motion in the elbow, which lead potentially to the FIV. Two different scale models, 1/7- and 1/14-scale simulating the JSFR cold-leg piping, are tested experimentally to confirm whether a scale effect in pressure fluctuation characteristics exists. A distinguishing peak can be seen in each power spectrum density (PSD) profile of pressure fluctuation obtained in and downstream of the flow separation region for both scaled models. When nondimensionalized, the PSD profiles show good correspondence regardless of scale model and even of Reynolds number simulated in this study.

Unsteady wall pressure characteristics of a 90 degree elbow in high Reynolds numbers

“…We concluded, from these facts, that the structural vibration caused oscillations with 7 ± 1 and 12 ± 1 Hz. This kind of oscillations had been also found in experiments conducted by Ebara et al (2010). Pressure measurements including these oscillations were not preferable, since we would like to focus only on flow induced vibrations.…”

“…Measurements were always done with that at the reference point, since the reference data should be obtained simultaneously. Ebara et al (2010) Fig. 3 is the outside point at the elbow inlet: The value shown in Fig.…”

Numerical Investigation on Large Scale Eddy Structure in Unsteady Pipe Elbow Flow at High Reynolds Number Conditions with Large Eddy Simulation Approach

“…A few investigations on pipe elbow flow in a short curvature radius (Rc/D<3) were found in literature (17)- (22) and they were listed in Table 1 including recent experiments for the JSFR hot-leg piping investigation (2)- (5) . As a notable study, Frried and Idelchik (16) proposed a useful classification on the trend of the total resistance (pressure loss) coefficient for the curved duct with a short curvature radius into three regimes as function of Reynolds number.…”

“…Coffield et al (22) measured the total pressure loss coefficients in the smooth surface finished pipe elbow of Rc/D=1.2 in the post-critical regime of 2x10 5 <Re<4x10 7 . Useful information related to the short-elbow flow at very high Reynolds number conditions (Re>5x10 5 ) in the post-critical regime could be obtained by (5) and Yuki,et al (33) 3.2x10 5 ~ 1x10 6 1 0.127 Water the several experiments (2)-(5), (32), (33) and the Coffield's measurement (22) . Shiraishi et al (2) measured pressure loss coefficient of the test section and axial velocity profiles of water flow in the post critical regime of 3.2x10 5 <Re<8.0x10 6 by using the Laser Doppler Velocimetry (LDV) technique.…”

“…Since axial flow in the upstream vertical pipe turns quickly to horizontal flow through the short-elbow, it can be easily conjectured that flow through the short-elbow may be different from those through a pipe elbow with long curvature radius (hereinafter, called as the long-elbow) and that flow instability may induce in the hot-leg piping. In order to study unsteady flow characteristics through the short-elbow at high Reynolds number condition, several water experiments (2)- (5) and numerical investigations (6)- (10) have been conducted. In the experiments (2) , significant pressure fluctuation with dominant frequency at approximately 0.5 in Strouhal number was observed on the pipe wall.…”