Effects of Reynolds Number on Twin Circular Jets at a Small Space Ratio

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International Journal of Research and Scientific Innovation (IJRSI) | Volume VII, Issue VIII, August 2020 | ISSN 2321–2705

Effects of Reynolds Number on Twin Circular Jets at a Small Space Ratio

Shams Sourav, Ashraful Hossain Rifat, M A Taher Ali
Department of Aeronautical Engineering, Military Institute of Science and Technology, Dhaka-1216, Bangladesh

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Abstract: A twin circular jet of diameter 20 mm is investigated experimentally for a small space ratio of 1.2 and how Reynolds number affects the flow field is analyzed for three different Reynolds number (Re = 16300, 34400 and 49200). The experiment is carried out in an air jet facility and pressure probe method is used to measure and calculate the position dependent data. Mean velocity profiles along the longitudinal, transverse and lateral directions are studied where an impact of varying Re is evident. Static pressure and mean kinetic energy distributions are also investigated where an enormous influence of Re is found. With the increase of Re, interaction of two jets is enhanced and ample amount of energy and mass transfer occur between the shear layers of the twin jets.

Keywords- twin jets, mean velocity, static pressure, kinetic energy, flow field, shear layer.


Twin jets are produced when flow exerted from a nozzle having two orifices. This two orifices can be symmetric, asymmetric or of different shapes. Various advantages have been unfolded for a twin jet over a single jet regarding its mixing characteristics, noise generation level and other phenomena while applying in gas turbine combustion system, mixing in boiler, burner, chemical reactor and so on.
Twin jets have been studied from last few decades where many researchers came up with various results. For example, Tanaka [1], [2] was one of the earliest researchers to study two dimensional parallel jets where he found three regions in the downstream of the flow named converging, transition and combined regions respectively shown in Fig. 1. According to him the region from jet exit to point where inner shear layers merge is called converging region, from merge point to combined point is called transition region and from combined point to onward is called combined region. Elbana et al. [3] experimentally observed the interaction between two plane parallel jets and found that mean velocity profile behaves like a single jet after combined point. Lin and Sheu [4], [5] investigated two parallel plane jets by hot wire anemometry where their result shows that in combined region entrainment and spreading rate are greater in twin jet than single jet. Pandey and Kumar [6] numerically analyzed twin jet flow at a fixed space ratio of 9 and different Mach numbers. They noticed that jet width and merging length increases with Mach number. Behavior of twin axisymmetric free jet at various nozzle spacing was investigated