Mean Streamwise Centerline Velocity Decay and Entrainment in Triangular and Circular Jets

Effect of nozzle geometry on the dynamics and mixing of self-similar turbulent jets

“…The results revealed that the orifice plate nozzle provided the highest rate of mixing and the pipe jet had the least mixing with the ambient fluid (Mi et al 2001). Furthermore, the orifice jets had higher rate of decay and entrainment compared to the top-hat jets in the near-field region (Quinn et al 2013).…”

“…Non-circular jets have been experimentally and numerically studied by various researchers because of their potential to enhance mixing between jets and the ambient fluid (Ho & Gutmark 1987;Hussain & Husain 1989;Quinn 1989Quinn , 2005Grinstein et al 1995;Miller et al 1995;Mi et al 2000). Considerable research efforts have also been made to understand the effects of nozzle geometry on mixing performance and turbulence characteristics of turbulent jets in the near-field (Hussain & Husain 1989;Mi et al 2001;Quinn 2005;Mi & Nathan 2010;Azad et al 2012;Hashiehbaf & Romano 2013;Quinn et al 2013;Xu et al 2013aXu et al , 2013bAleyasin et al 2017). In general, it has been found that the loss of axisymmetry of the orifice nozzle configuration increases the decay rate of mean and RMS velocities in the near-field, from which higher entrainment into the jet may be concluded (Mi et al 2001).…”

“…It has also been claimed that the statistics in the self-similar region may depend on the initial conditions (George & Arndt 1989). Furthermore, many of the past studies only focused on the mean velocity and turbulence intensities along the centerline (Mi et al 2000;Mi & Nathan 2010;Azad et al 2012;Quinn et al 2013).…”

Experimental study on the forcing design for an intermittent injection

“…It is defined by Wygnanski and Fiedler (1969), Crow and Champagne (1971) and Liepmann and Gharib (1992) as the spatial derivative of the mass flow rate Q in the streamwise direction dQ dx , or conversely as its deficit with respect to its amount at the inlet location Q 0 compared to the Q 0 itself E = Q−Q 0 Q 0 . The mass flow rates Q were numerically estimated integrating the samples mean streamwise velocity at each subperiod of the pulse cycle making use of the definition (Quinn et al 2012): where dA is an elemental area in the x-y plane, evaluated assuming the axisymmetry of the phenomenon. In correspondence to all the streamwise locations, the integration was carried out until the radial location where the samples mean streamwise velocity was equal to the 10% of the corresponding centerline value, c.f.…”

“…In correspondence to all the streamwise locations, the integration was carried out until the radial location where the samples mean streamwise velocity was equal to the 10% of the corresponding centerline value, c.f. (Quinn et al 2012). In this way, by integrating only the core of the jet, and by assuming conservation of momentum, E can be seen as a metric of mixing, since it assesses the mass entrained by the jet from the ambient fluid.…”