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This paper presents some results from a computational fluid dynamics (CFD) model of a multi-megawatt crosswind kite spinning on a circular path in a straight downwind configuration. The unsteady Reynolds averaged Navier-Stokes equations closed by the k−ω SST turbulence model are solved in the three-dimensional space using ANSYS Fluent. The flow behaviour is examined at the rotation plane, and the overall (or global) induction factor is obtained by getting the weighted average of induction factors on multiple annuli over the swept area. The wake flow behaviour is also discussed in some details using velocity and pressure contour plots. In addition to the CFD model, an analytical model for calculating the average flow velocity and radii of the annular wake downstream of the kite is developed. The model is formulated based on the widely-used Jensen’s model which was developed for conventional wind turbines, and thus has a simple form. Expressions for the dimensionless wake flow velocity and wake radii are obtained by assuming self-similarity of flow velocity and linear wake expansion. Comparisons are made between numerical results from the analytical model and those from the CFD simulation. The level of agreement was found to be reasonably good. Such computational and analytical models are indispensable for kite farm layout design and optimization, where aerodynamic interactions between kites should be considered.

Soil loss from root crop harvesting is a significant erosion process contributing to soil degradation. While organic fertilization could promote soil structure and reduce soil loss, the variation in the effectiveness of different organic fertilizers vis-a-vis inorganic fertilization remains unclear. Such understanding is critical for adequate soil management for reducing harvest-related soil loss. A two-year field-based study was carried out to compare the effect of two commonly used organic amendments and inorganic fertilizer on carrot yield and harvest-related soil loss. Treatments included a control, inorganic fertilizer, pig manure, and poultry manure; with each manure applied at a rate to supply 60 kg K ha-1. Compared to the control where the average soil loss for the two years was 1.21 t-1 ha-1 harvest -1, inorganic fertilization induced a soil loss of 2.70 t-1 ha-1 harvest -1, while 1.94 t-1 ha-1 harvest -1 and 1.87 t-1 ha-1 harvest -1 of soil was lost under poultry manure and pig manure amendments, respectively. The higher soil loss in the fertilized treatments compared to the control was attributed to the higher crop yields. However, the reduced soil loss in organic amendments compared to the inorganic fertilizer was due to more improved soil aggregation. Also, higher nutrient uptake arising from the increased yield resulted in significant loss of soil nitrogen, phosphorus, potassium, and calcium in the second year. Higher carrot yield due to fertilization is associated with higher soil removal, especially under inorganic fertilization. It is suggested that cleaning carrot roots during harvesting will ensure minimal soil loss. [ABSTRACT FROM AUTHOR]