Hello, A yearly allocation for the LCRC cluster has been requested with the following updated information: Submitter/PI: Sibendu Som Project Name: LES-Engine Division: ES Project title: LES modeling of injection transients for fuel injectors Associated funding: DOE Office of Vehicle technologies Other Systems: University of Perugia Science: The objective of this study is to evaluate the feasibility and the possible benefits of multiphase LES applied to the simultaneous modeling of in-nozzle and near exit flow in diesel injectors. Transient part of injections are simulated in single-hole injectors using a two-phase three-components Eulerian mixture model. High-resolution (2.5 μm) LES are devised and carried out to capture phenomena at small needle valve lifts and on small orifices. The multiphase model accounts for compressibility of both liquid and gas phase, and it also includes phase change due to cavitation. Transient jet features at the start- and end-of-injection are simulated and results compares well with synchrotron x-ray imaging and radiography data. Simulation results demonstrate the potential to comprehensively understand the physics of start- and end-of-injection transients complementing experimental data. Part of the study focuses on the description of the fast dynamics of these processes , since it is resolved in great detail. Concerning the EOI behavior, liquid jet breakup, gas ingestion, in-nozzle bubble formation and dribbles are predicted. For the SOI behavior it is reported the initial ejection of residual gases trapped in the sac. Prescribing the needle motion from a very low lift, the timing of the first injected fuel is also captured. In addition, some potential effects on the initial evaporation rate and liquid length of the spray are highlighted. Part of the study also focuses on the mesh assessment and suitability for LES of nozzle-flow and jet region. Two criteria are evaluated, one based on the amount of resolved turbulent kinetic energy, and one based on a length-scale resolution. Due to the high computational cost of the simulations, the collection of statistical turbulence quantities is performed in quasi-steady conditions via temporal averaging, and not as ensemble averaging over multiple realizations. This poses some specific challenges tha t will be subject of new work. Instead, the length-scale resolution index allows a local dynamic evaluation of the mesh resolution that can be used either for a posteriori grid assessment or for adaptive LES, in the future. The grid resolutions employed, of about 2.5-5 μm results adequate for the resolution of the external spray, but may not suffice for the extremely challenging requirements of the internal wall-bounded injector flow. Project description: This work reports investigations on diesel spray transients, accounting for internal nozzle flow and needle motion, and demonstrates how seamless calculations of internal flow and external jet can be accomplished in a Large Eddy Simulation (LES) framework using an Eulerian mixture model. Two problems are studied with high level of spatial and temporal resolution. The first one concerns an end-of-injection (EOI) case where gas ingestion, cavitation, and dribble formation are resolved. The second case is a start-of-injection (SOI) simulation that aims at analyzing the effect of residual gas trapped inside the injector sac on spray penetration and rate of fuel injection. Simulation results are compared against experiments carried out at Argonne National Laboratory (ANL) using synchrotron x-ray. LES of both end-of-injection and start-of-injection processes have been carried out on a single hole diesel injector, providing insights in to the physics of the pr ocesses, with internal and external flow details, and linking the phenomena at the end of an injection event to those at the start of a new injection. A mesh sensitivity analysis is conducted to assess the quality of the LES approach by evaluating the resolved turbulent kinetic energy budget and comparing the outcomes with a length-scale resolution index. Concerning the end-of-injection, the model predicts ligament formation and gas ingestion, as observed experimentally, and the amount of residual gas in the nozzle sac matches with the available data. The fast dynamics of the process is described in detail. The simulation provides unique insights into the physics at the end-of-injection. Similarly, the start-of-injection simulation shows how gas is ejected first, and liquid fuel starts being injected with a delay. The simulation starts from a very low needle lift and is able to predict the actual rate-of-injection (ROI) and jet penetration, based only on the prescribed needl e motion. Finally, guidelines and future improvements of the model are discussed concerning the simulation of the transient injection phases. Industry partnership: None Project URL: http://www.transportation.anl.gov/engines/multi_dim_model_home.html Current FY Hours Used: undetermined amount New FY Requested allocation: 1000000 Q1: 250000 Q2: 250000 Q3: 250000 Q4: 250000 Justification: During the past four years, we have been working in close collaborations with the developers of CONVERGE code to ensure that it scales well both on clusters and super-computers. We have implemented METIS algorithm which enables us to load balance significantly better than the original load balancing in CONVERGE. This was the first step towards enabling CONVERGE code for HPC use. In collaboration with researchers at ALCF (during the past couple of years), we have further performed scaling studies with the code on Mira. Based on implementation of MPI-I/O, advancements in chemistry calculation with a stiffness based load balancing criteria and CFD load balancing, we have been able to show good scaling of the CONVERGE code on Mira on up to 4096 processors for a closed cycle engine simulation with about 10 million cells. These advancements were showcased during the VERIFI workshop in Nov. 2014 and we have published a detailed paper highlighting these changes. The a bove changes are not only expected to benefit calculations on Mira but also help on computing clusters like Fusion and Blues. More details and paper can be made available on request. Storage requirements: 1 TB Thank You, The LCRC Accounts System