Purpose The purpose of this paper is to design a double parabolic nozzle and to compare the performance with conventional nozzle designs. Design/methodology/approach The throat diameter and divergent length for Conical, Bell and Double Parabolic nozzles were kept same for the sake of comparison. The double parabolic nozzle has been designed in such a way that the maximum slope of the divergent curve is taken as one-third of the Prandtl Meyer (PM) angle. The studies were carried out at Nozzle Pressure Ratio (NPR) of 5 and also at design conditions (NPR = 3.7). Experimental measurements were carried out for all the three nozzle configurations and the performance parameters compared. Numerical simulations were also carried out in a two-dimensional computational domain incorporating density-based solver with RANS equations and SST k-ω turbulence model. Findings The numerical predictions were found to be in reasonable agreement with the measured experimental values. An enhancement in thrust was observed for double parabolic nozzle when compared with that of conical and bell nozzles. Research limitations/implications Even though the present numerical simulations were capable of predicting shock cell parameters reasonably well, shock oscillations were not captured. Practical implications The double parabolic nozzle design has enormous practical importance as a small increase in thrust can result in a significant gain in pay load. Social implications The thrust developed by the double parabolic nozzle is seen to be on the higher side than that of conventional nozzles with better fuel economy. Originality/value The overall performance of the double parabolic nozzle is better than conical and bell nozzles for the same throat diameter and length.

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An ultrasonic nebulization technique has been used for uniform wetting of soil by introduction of an aerosol. Values obtained for aggregate stability of air‐dried soils were greater when this technique was used than with conventional wetting techniques, apparently because of reduced slaking effect.

Computational study on the development of mean flow and mixing capability of a rectangular tab placed at the exit of a Mach 1.6 single and twin jet nozzles has been presented. Placing two identical conical nozzles side by side separated by a distance of 1.5 times exit diameters makes the twin jet configuration. The mitigation technique for twin jet cross coupling effects by rectangular tabs for the enhancement of aerodynamic and acoustic characteristics is validating. The results are relevant to situations wherever shock cell structures, potential core length, jet mixing related noise are of concern. Centre line pressure decay characteristics shows that there is an abrupt reduction in the core length and suppression of shock cell structure at off design conditions. The results are in good agreement with the experimental results.

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