ASCOMP provides consulting services in hydraulic engineering and water technology, interpreted widely, with applications of relevance to water filtration and separation technology, heavy rain and dam failure induced floods, land- & rock-sliding, snow avalanches, water storage systems, coastal engineering, etc. Provided consultancy studies are based on detailed 3D simulations using TransAT Multiphase, more particularly the powerful free surface modules of the code combined with its advanced turbulence modelling, as shown in the examples selected below.
Secondary water clarifiers
Investigating the flow within wastewater treatment plants is essentially dictated by design interests: It is aimed at helping to design secondary clarifiers, whose efficiency is such that the overall performance of the entire wastewater treatment does not require post operations. An intensive scientific effort has recently been made in order to understand this type of flow, and various CFD models have been developed for the purpose, most of which are based on RANS models describing turbulent non-Newtonian fluid flow pattern and sediment-induced density currents. Other mechanisms could also be accounted for today, viz. flocculation, coagulation, and filtration. The transported phase settles at a velocity strongly influenced by its concentration. TransAT results of modelling the sedimentation of a sludge blanket in a circular, secondary clarifier with inclined bottom and central withdrawal are shown below.
Stagnant water aeration
Bubble plumes are often involved in environment protection problems such as the aeration of lakes, mixing of stagnant water and, generally, de-stratification of water reservoirs. For all these applications the basic need is to determine the currents induced by the gaseous phase evolving in the surrounding liquid and thereby to establish the consequent mixing and partition of energy, or species concentration in the body of the liquid. More important is the fact that predicting bubbly flows cannot be achieved without suitable models capable of correctly representing interphase momentum transfer mechanisms and turbulence modulation induced by the bubbles. This includes the effect of bubble migration through the liquid, and more often the interactions between eddies and the dispersed phase via what is known as turbulent dispersion models.
Heavy rain induced floods
The catastrophic results of extreme flood events continue to have major damaging effects in both the developed and the developing world. Floods are due to unusually heavy, prolonged, and sometimes torrential rains, and are accompanied with landslides. The complexity of the environmental flows in general and floods in particular induce still large uncertainties in the assessment and policies for mitigation of flood hazard. The development of a flood simulation methodology to evaluate hazard zone maps is now the objective of various policy and decision makers in the developed world in particular. Risk analysis based on these maps determine conditions which cause flooding and define the degree of the flood risk in different regions of the city. CFD and CMFD are now used to develop sustainable and passive flood defense systems, which require no operational cost and which reduce the impact of flooding worldwide and alleviate its financial and social cost.
Water storage reservoirs (WSR) in arid zones
These open-air storage areas are used to collect water which is then kept in quantity so that it may be drawn off for use. In arid zones like in the Middle East, WSR are built to control water supply for domestic and agricultural use. Changes in weather cause the natural flow of streams and rivers to vary greatly with time. Periods of excess flows and valley flooding may alternate with low flows or droughts. The role of water-storage reservoirs, therefore, is to impound water during periods of higher flows, thus preventing flood disasters, and then permit gradual release of water during periods of lower flows. Simple storage reservoirs were probably created early in human history to provide water for drinking and for irrigation.
Dam break induced floods
Floods and associated damages can also be caused by dam failure due to excessive water pressure. The estimation of inundated areas is necessary for mitigation of hazards. Dam-break flood waves are hydrodynamically dangereous (accelerating high-inertia flows) and could be worse when they propagates over complex topography, which changes the head velocity, flow pattern and penetration depth. Obstacles could be local sills, debris in river beds as well as buildings, cars in urban areas. TransAT is now used to predict this sort of floods and defense systems for various types of debris and obstacles, as shown below.