The mechanism of asymmetric pipe-wall thinning behind an orifice by combined effect of swirling flow and orifice bias

Influence of swirling flow on mass and momentum transfer downstream of a pipe with elbow and orifice

“…The swirl intensity of the flow, defined by the ratio of the circumferential momentum to the axial one, is estimated as 0.26 at 3 diameters upstream of the orifice. Since then, several experimental studies on the mass and momentum transfer downstream of the orifice have been carried out to elucidate the mechanism of pipe-wall thinning in the pipeline [12][13][14][15][16][17][18][19][20][21][22].…”

“…Recent studies on the measurement of mass transfer coefficient downstream of the orifice in swirling flow are conducted in a water tunnel and found that the pipeline elements upstream of the orifice modify the characteristics of mass and momentum transfer [17,[20][21][22]. Although these experiments provide important findings, such as the occurrence of non-axisymmetric mass transfer downstream of the orifice, the influence of the swirl on the mass and momentum transfer downstream of the orifice is still not clear.…”

On flow structures associated with large wall mass transfer coefficients in orifice flows

“…Furthermore, some researchers have used the naphthalene sublimation method to measure the wall mass transfer coefficient of flows behind orifices and have discussed the mechanism involved in asymmetric pipe-wall thinning in relation to the combined effect of swirling flow and orifice bias [13,14]. In this respect, the naphthalene sublimation method allows the measurements of mass transfer coefficients in air flows at low Schmidt numbers.…”

Mechanism of non-axisymmetric pipe-wall thinning in pipeline with elbow and orifice under influence of swirling flow

“…In the experiment by NISA (2005), the magnitude of the swirling flow in pipeline A, which is defined as the ratio of the circumferential momentum to the axial one, was 0.26 at a position three diameters upstream of the orifice of pipeline A and 0.08 at the same position in pipeline B. Since then, several studies have been conducted to elucidate the mechanism of FAC in the pipeline (Yoneda et al, 2008;Ahmed et al, 2012;Fujisawa et al, 2012;Takano et al, 2012;Utanohara et al, 2012); however, this mechanism has not yet been fully understood because of the complexity of the flow field related to the FAC. It should be mentioned that the thinning rate of pipeline A is much higher than that on the other side and that of pipeline B.…”