MATHEMATICAL SIMULATION OF A WATER HYACINTH (EICHHORNIA-CRASSIPES) TOWING SYSTEM

A mathematical model representing a water hyacinth towing system of moderate size was formulated as a network of mechanical components. The system consisted of a rectangular device enclosing water hyacinth mats of various shapes and sizes and towing them by an applied input velocity. Three physical properties of a mat were found to be significant: viscous drag of plant rhizomes in water, viscous friction of leaves sliding over each other during compaction, and masses of the mat and accelerated water. Mass of the enclosure and a spring in the enclosure for measuring towing force also was incorporated in the model. Descriptions of the components and their interconnections were based on experimental observations and physical and hydromechanical fundamentals. Analyses of model behaviour were performed for towing velocity less than 0.4 m/s, the experimentally observed velocity at the onset of mat instability. Effects of different acceleration patterns, mat physical characteristics, and towing velocity on system behaviour were investigated in physical experiments and simulations with the model. The model and new information upon which it was based permit engineering design of different types of systems for harvesting water hyacinths in sewage treatment, canals, and lakes.