Experimental and Numerical CFD Modelling of the Hydrodynamic Effects Induced by a Ram Pump Waste Valve

The hydraulic ram pump or hydram is a machine capable of lifting water to a hydraulic head higher than the level of the supply source. It is a sustainable and self-sufficient device: the working principle is based on the rise of abrupt pressure variations occurring in the feeding pipeline when the liquid inside it undergoes a locally sharp change in velocity as a consequence of the sudden closure of the waste valve. Invented in 1772, the pump has been improved over the decades. Due to its simplicity, low cost and reliability, it has been widely used worldwide to provide adequate domestic water supplies, especially before the spreading of electricity and internal combustion engines. In recent years, the new attention placed on sustainability and energy transition from fossil fuels to renewable energy devices has brought a growing interest to this basic machine, essentially forgotten and abandoned in the last century; it seems promising especially in developing countries. The hydram is, in fact, a very simple machine, with only two moving parts, the waste and delivery valves. The efficiency of the hydraulic ram pump is mainly influenced by the characteristics of the waste valve. However, sufficient data are not available for the design of the hydram and the waste valve. In this work, the behaviour of the waste valve of a hydram was simulated by means of Computational Fluid Dynamics (CFD). Velocity and pressure values were analysed for different scenarios with different closing times of the valve. The data obtained from the developed numerical model were compared, in order to verify the validity of the simulations, with those collected during the operation of the hydram placed at the Laboratory of Environmental and Marine Hydraulics (LIDAM) of the University of Salerno, Italy. The numerical model thus obtained can, therefore, be used to identify the ideal configuration of the valve in order to ensure the best performance of the hydram.