Ram Pump

Ram Pump — ANSYS Fluent CFD Simulation

Description

This project simulates a ram pump using ANSYS Fluent, with the mesh-motion technique driving the moving valves at the heart of the device. A ram pump is a clever, energy-free pump: it uses the pressure surge created when a moving column of water is suddenly stopped by a closing valve — the water-hammer effect — to lift a portion of that water to a higher level, without any external power source. Capturing this behavior means physically moving the valves within the simulation, which is exactly what the mesh-motion approach provides. Within the Rotary Equipment: Beginner CFD Training Package, this project opens the pump group, applying mesh motion to a valve-driven pumping device.

Methodology

The two-dimensional geometry is produced in SpaceClaim, with a computational domain 220 cm long and 153 cm high, meshed in ANSYS Meshing using unstructured elements for a total of 325,579 elements. Because the flow is incompressible, a pressure-based solver is selected and the simulation is transient, with gravity taken into account at −9.81 m/s² along the y-axis. Turbulence is modeled with the k-omega SST model. The mesh motion is applied to the left and right valves as a cell-zone condition with a rotational velocity of 1 rad/s. The inlet is defined as a velocity inlet at 1 m/s, the outlet as a pressure outlet at 0 Pa gauge, and the walls as stationary. Pressure–velocity coupling uses the Coupled scheme; spatial discretization is second-order for pressure, second-order upwind for momentum, and first-order upwind for both the turbulent kinetic energy and the turbulent dissipation rate. The solution is initialized with the hybrid method.

Analysis

At the end of the simulation, the velocity and pressure fields can be examined to reveal how the moving valves control the flow. When both valves are half-closed, the resulting restriction increases the pressure inside the pipe. When one valve is fully open and the other completely closed, all of the inlet fluid exits through the open side under the high pressure created there. By the end of this project, you'll be able to set up a transient mesh-motion simulation with moving valves defined as cell-zone conditions, apply the k-omega SST turbulence model to an incompressible internal flow, and interpret the velocity and pressure fields to understand how a ram pump develops and uses its pressure surge.