An investigation into the scaling law of converging length for compressible round twin-jet

Abstract

An experimental investigation has been conducted to develop the scaling law for the converging length of compressible round twin-jets. A twin-jet system with nozzle exit diameter D and normalized inter-nozzle spacing [Formula: see text] of 3, 4, and 5 was investigated at ideally expanded jet Mach numbers [Formula: see text] of 0.3, 0.5, 0.7, 1.0, 1.35, and 1.56. Scaling analysis performed for the converging length xcp revealed that the relationship [Formula: see text] could be reduced to [Formula: see text], where g1 and g2 are different functions. This scaling law extended to include both perfectly and imperfectly expanded sonic and supersonic twin-jets, leading to the relation [Formula: see text], is proportional to [Formula: see text], where [Formula: see text], γ, and jc are the nozzle expansion ratio, gas specific heat ratio, and index number, respectively. It has been documented that [Formula: see text] is the length scale to normalize xcp, which is valid for subsonic, sonic, and supersonic twin-jets. As such, for a given [Formula: see text] and Mj, the dependence of [Formula: see text] on S/ D can be predicted using the scaling law [Formula: see text]. Further, the scaling law is discussed, leading to an interpretation of the physical meaning of the dimensionless parameter [Formula: see text].