Solving partial differential equations in deformed grids by estimating local average gradients with planes

For constructing physical science based models in irregular numerical grids, an easy-to-implement method for solving partial differential equations has been developed and its accuracy has been evaluated by comparison to analytical solutions that are available for simple initial and boundary conditions. The method is based on approximating the local average gradients of a field by fitting equation of plane to the field quantities at neighbouring grid positions and then calculating an estimate for the local average gradient from the plane equations. The results, comparison to analytical solutions, and accuracy are presented for 2-dimensional cases.

Clarification of turbid water with the use of Praestol 650 flocculant

Рассмотрена эффективность самостоятельного применения катионного флокулянта Праестол 650 для очистки мутных вод в зависимости от мутности исходной воды и условий флокуляции. Показано, что приоритетными параметрами, определяющими эффективность самостоятельного применения катионного флокулянта Праестол 650 для очистки мутных природных вод, является интенсивность и длительность перемешивания в камере хлопьеобразования. При длительности не менее 20 минут и среднем градиенте скорости перемешивания G = 340 с-1 эффективность снижения мутности составляет 96% (конечная мутность 7 мг/л). Установлена 96%-ная эффективность неионного флокулянта с молекулярной массой 5–7 млн в неоптимальном режиме хлопьеобразования при длительности перемешивания 5 минут и G = 65 с-1. The efficiency of the individual use of the cationic flocculant Praestol 650 for the purification of turbid water is considered, depending on the turbidity of the source water and the conditions of flocculation. It is shown that the priority parameters that determine the effectiveness of the individual use of the cationic flocculant Praestol 650 for the purification of turbid natural water are the intensity and duration of mixing in the flocculation chamber. With a duration of at least 20 min and an average gradient of mixing rate G= 340 s-1, the efficiency of turbidity reduction is 96% (final turbidity being 7 mg/l). A 96% efficiency of the non-ionic flocculant with a molecular weight of 5–7 million was determined in a suboptimal flocculation mode with a mixing period of 5 min and G = 65 s-1.