Hello, A yearly allocation for the LCRC cluster has been requested with the following updated information: Submitter/PI: Prasad Vegendla Project Name: CFD-TPM Division: NE Project title: Computational Fluid Dynamics Modeling and Validation of Two-phase Boiling Flow and Critical Heat Flux Associated funding: NEAMS - Reactor Product Line Other Systems: Science: Multi-phase flow and boiling are of fundamental importance in the design of nuclear reactors used for energy generation, the vast majority of which are cooled by water. These reactors, referred to as Light Water Reactors (LWRs), can be divided into two major types: the Boiling Water Reactors (BWR) designed to operate under saturated boiling conditions, and the Pressurized Water Reactors (PWR) designed to operate at higher pressure than the BWRs and under sub-cooled boiling conditions. The assessment of the fuel assembly behavior under two-phase flow conditions is of particular importance, since many design and safety criteria depend on it. In particular, boiling flows are subject to the phenomenon known as "boiling crisis" where, for high cladding surface heat fluxes (exceeding the critical heat flux or CHF), the heat transfer between the cladding and coolant deteriorates, leading to sharply higher cladding surface temperatures. Such temperatures lead to a deterior ation of cladding structural integrity and ultimately to fuel pin failure and radionuclide release. Therefore, the Nuclear Regulatory Commission requires vendors to accurately evaluate the CHF phenomenon in their nuclear reactor designs, and to demonstrate that the “boiling crisis” can be avoided in their reactors even under unlikely hypothetical accident scenarios. New fuel assembly designs need therefore to be tested in very expensive high-power, full-scale water loops, of which very few exist. • The main objective of this project is to build and validate two-fluid boiling framework in the Nek5000 solver. As a first step, a homogeneous, drift-flux model and two-fluid models are successfully implemented, which will be used to validate more advance boiling framework that will be developed later. Project description: In boiling water reactors, dryout is an important limiting phenomenon in the design of heat exchangers and is associated with the disappearance of the liquid film on the wall in heat exchanger tube. A consequence of this non-wetting heated surface deteriorates the convective heat transfer mechanism resulting in a large rise in the wall temperature of heat flux imposed system such as nuclear reactor fuel rod assemblies. Since dryout is a hydrodynamic phenomenon involving entrainment and re-deposition of droplets as well as boiling/evaporation of the liquid, the location of dryout is dynamic and its fluctuation may also give rise to thermal fatigue and corrosion. A large number of experimental and theoretical studies have been conducted over the past several decades to understand and quantify the processes leading to dryout in a heat exchanger tube. * Nek5000 is a highly-scalable open-source transient CFD code developed by MCS-Argonne National Laboratory. This code is based on spectral element method and it is written in basic FORTRAN and C languages. It has more than 200 users world-wide and a long history of development, verification, and validation. * In this project, Nek5000 is used as a platform to develop two-fluid model. * In order to validate the Nek5000 development for two-phase boiling capability, several simulation runs are planned for wide range of pressure, mass flux and wall heat flux. * In FY2017, blues allocated hours are efficiently used for projects of CFD-TPM and NE_RANS. * A total of 4 members can use the allocated hours Industry partnership: Project URL: Current FY Hours Used: undetermined amount New FY Requested allocation: 495000 Q1: 125000 Q2: 125000 Q3: 120000 Q4: 125000 Justification: Nek5000 is a highly scalable tool on fusion. NE users demonstrated good scalability up to several hundred cores. Recent simulations of homogeneous two-fluid boiling model on Fusion cores reported 10% and 58% overhead associated with MPI communication for 128 and 256 cores, respectively. Storage requirements: 1 TB Thank You, The LCRC Accounts System