Purpose Impinging jets have been widely studied, and the addition of swirl has been found to be beneficial to heat transfer. As there is no literature on Reynolds-averaged Navier Stokes equations (RANS) nor experimental data of swirling jet flows generated by a rotating pipe, the purpose of this study is to fill such gap by providing results on the performance of this type of design. Design/methodology/approach As the flow has a different behaviour at different parts of the design, the same turbulent model cannot be used for the full domain. To overcome this complexity, the simulation is split into two coupled stages. This is an alternative to use the costly Reynold stress model (RSM) for the rotating pipe simulation and the SST k-ω model for the impingement. Findings The addition of swirl by means of a rotating pipe with a swirl intensity ranging from 0 up to 0.5 affects the velocity profiles, but has no remarkable effect on the spreading angle. The heat transfer is increased with respect to a non-swirling flow only at short nozzle-to-plate distances H/D < 6, where H is the distance and D is the diameter of the pipe. For the impinging zone, the highest average heat transfer is achieved at H/D = 5 with swirl intensity S = 0.5. This is the highest swirl studied in this work. Research limitations/implications High-fidelity simulations or experimental analysis may provide reliable data for higher swirl intensities, which are not covered in this work. Practical implications This two-step approach and the data provided is of interest to other related investigations (e.g. using arrays of jets or other surfaces than flat plates). Originality/value This paper is the first of its kind RANS simulation of the heat transfer from a flat plate to a swirling impinging jet flow issuing from a rotating pipe. An extensive study of these computational fluid dynamics (CFD) simulations has been carried out with the emphasis of splitting the large domain into two parts to facilitate the use of different turbulent models and periodic boundary conditions for the flow confined in the pipe.

No abstract

No abstract

The excavation performance of swirling jets impinging normally against a sand bed from several distances is described. A specially-designed nozzle with adjustable swirl vanes was used to generate swirling jets of various swirl intensities. Two sand beds of different grain size distributions were considered. The main scour patterns on the sand bed produced by the swirling jets were measured by image processing of photographs of the bed illuminated by a laser sheet. The velocity profiles of the swirling jets at the nozzle exit were measured using Laser Doppler Anemometry for various test conditions. The scour patterns were then analysed in relation to the details of the velocity profile of the swirling jets, their Reynolds numbers and the distances from the nozzle to the bed. The optimum jet features resulting from the different swirl nozzles and the best impinging distances for sea bed excavation are identified and discussed.

No abstract