Numerical investigation of energy and Reynolds stress distribution for a turbulent flow in an orifice

• In the present study the steady, turbulent, two-dimensional flow of heavy water and light water in a cross sectional orifice is considered to study the influence of process fluid on turbulent parameters and on the FAC rate.
• The vortical structure in an orifice examined extensively. For the different Re values, the zero shear stress lines are captured to describe the separation flow at the downstream of the orifice.
• The TKE, its DR and Reynolds stresses were calculated at the solid surface downstream of the orifice and also in the recirculation region at different axial locations along the transverse direction.
• Also, to examine the FAC rate of heavy water flow and light water flow in an orifice the Sh distribution has been calculated along the solid surface at the downstream of the orifice.
• From the present study the review of peak values of turbulence parameters and Sh in the orifice will help to locate the locations which are susceptible to FAC in the recirculation region and gives the intimation to pay attention at the orifice edge.

The turbulent heavy water and light water flows through an orifice, which characterize different reactor systems in nuclear power plants, are studied. The aim was to reveal the influence of process fluid on the turbulence parameters by considering heavy water and light water flows under the unique flow accelerated corrosion (FAC) conditions. The heavy water and light water are referenced based on their density values. The change in density values may have an effect on the flow dynamics and hence on FAC. These effects are brought out in this study and they can be extended to other cases for example, the change in the density of light water due to the chemical additions for controlling the pH values. The flow details at the downstream of orifice were studied extensively with the aid of computational modelling for different Reynolds numbers. Also structural development of the entire vortical flow field which could immensely enhance the knowledge about vortical structures occurring in the recirculation regions at the upstream and downstream of orifice is investigated. This study has been started with the exploration of flow topology of the velocity field by checking the topological consistency. The kinetic energy and dissipation rate were predicted by the modelling of turbulence using the Realizable k–ɛ model. Also the Reynolds stresses were calculated using the Reynolds stress model. The recirculation region showed maximum value for these parameters near the center line of the elliptic point, but for the dissipation rate this maximum value is observed at the wall. The maximum values of kinetic energy and wall shear stress are observed at the periphery of the orifice in comparison with that of the recirculation region. The predicted turbulent parameters have higher values in the recirculation region for heavy water flow and at the periphery of the orifice for light water flow with respect to each other flows. Also, the Sh distribution has been analyzed to estimate the FAC rate along the solid surface. The predicted peak values of these parameters will help to locate the locations which are susceptible to FAC.