Determination of the influence of the driving speed on the application parameters of orchard sprayers

Orchard sprayers with air transported fine droplets need an exact adjustment of the airflow and the spray nozzles in order to reduce the drift of pesticides. The adjustment is made on one hand side by the manufacturer and on the other hand side by the farmer in the orchard by choosing the tractor speed, the PTO shaft rotation speed and the pump pressure. For testing two test beds have been in charge in the region of Styria since almost 2 decades. One of them is able to measure the flow field in a vertical plane representing the tree row in a distance of approx. 1.5 m from the middle of the track. The second measures the water distribution in the same vertical plane. Both are stationary so that the influence of the driving speed can hardly be assessed. High driving speeds up to 12 km/h and the increasing height of the orchards impose additional uncertainties. This was the reason for the present research project, which was intended to investigate the influence of the driving speed. A new air flow measurement test bed has been build, which is able to measure the flow field also during tractor movement in the described vertical plane up to 5 m above ground. Four different sprayers have been investigated in an orchard with and without leaves by visual method for four different speeds to determine the optimal application parameters. The same sprayers have been tested with the moveable flow field test bed. Results show a reasonable correlation between the measurements for all investigated speeds. The differences between the sprayers are evident, nevertheless a method has been found to deduce the correlation between the stationary measurement and the optimal parameters for the orchard. So the stationary flow test bed can be directly used to develop sprayers

An inter-comparison exercise of mesoscale flow models applied to an ideal case simulation

An exercise is described aiming at the comparison of the results of seven mesoscale models used for the simulation of an ideal circulation case. The exercise foresees the simulation of the flow over an ideal sea–land interface including ideal topography in order to verify model deviations on a controlled case. All models involved use the same initial and boundary conditions, circulation and temperature forcings as well as grid resolution in the horizontal and simulate the circulation over a 24-h period of time. The model differences at start are reduced to the minimum by the case specification and consist mainly of the parameterisation and numerical formulation of the fundamental equations of the atmospheric flow. The exercise reveals that despite the reduction of the differences in the case configuration, the differences in model results are still remarkable. An ad hoc investigation using one model of the original seven identifies the treatment of the boundary conditions, the parameterisation of the horizontal diffusion and of the surface heat flux as the main cause for the model deviations. The analysis of ideal cases represents a revealing and interesting exercise to be performed after the validation of models against analytical solution but prior to the application to real cases

Usage and validation of a fluid structure interaction methodology for the study of different suction valve parameters of a hermetic reciprocating compressor

The dynamics of the flatter valves inside a hermetic reciprocating compressor used in household appliances is the most important factor concerning the gas dynamic behaviour of such a compressor. Hence for a good valve design and for a reliable simulation of the compressor the ability to predict the movement of the valves is indispensable. The present paper describes a methodology which allows the prediction of the valve dynamics. For the validation of the methodology the simulation results of the suction valve dynamics have been compared with experimental data obtained out of measurements with a Laser-Doppler-Vibrometer. Furthermore the method has been used for the variation of some suction valve parameters and their influence onto the overall compressor performance has been shown. The whole methodology has been implemented into a commercial available CFD code (FLUENT) as a user defined function (UDF)

An Intercomparison Exercise of Mesoscale Flow Models Applied to an Ideal Case Simulation.

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra