Purdue University - School of Mechanical Engineering. Objective: Study and predict fluid dynamics of a bluff body stabilized flame configuration.

Transcription

1 Extinction Dynamics of Bluff Body Stabilized Flames Investigator: Steven Frankel Graduate Students: Travis Fisher and John Roach Sponsor: Air Force Research Laboratory and Creare, Inc. Objective: Study and predict fluid dynamics of a bluff body stabilized flame configuration. Method: Use Large Eddy Simulation (LES) combined with the finite-rate, eddy dissipation turbulencechemistry interaction model to simulate flame. Use non-reacting simulations to generate flow time scales in the critical regions of the flame for generation of more advanced stability correlations. Turbulent structures colored by velocity magnitude calculated via the second invariant of the velocity gradient tensor are compared for reacting (top) and non-reacting (bottom) flows in the wake of the Fujii bluff body. Results: Validation of RANS and LES turbulence models for use in the bluff body flame problem using Fluent. Evaluation of the capability of the Finite Rate, Eddy Dissipation model to correctly predict turbulence-chemistry interaction near lean blow out.

2 Energy Stable Weighted Essentially Non-Oscillatory (ESWENO) Finite Difference Schemes Graduate Student: Travis Fisher Sponsor: NASA Langley Research Center Objective: Improve capability to perform Large Eddy Simulations of subsonic and supersonic flame configurations through the continued development of robust high-order finite difference schemes, originally developed by Mark Carpenter at NASA. Method: Perform supersonic/subsonic reacting simulations utilizing differencing and artificial dissipation operators that satisfy the Summation-by-Parts (SBP) condition to maintain long-time stability in the energy norm, even for non-linear problems. This requires special treatments of the finite difference stencil near the boundary and the treatment of the boundary condition. Temperature (top), Density (middle), and OH Mass Fraction (bottom) contours are shown for a supersonic reacting shear layer utilizing ESWENO with new boundary closure. Results: Successfully developed boundary closures for 4 th order ESWENO finite difference schemes. Tested for subsonic and supersonic (left) reacting shear layers.

3 Modeling and Simulation of Cavitation Noise in Fluid Power Components Graduate Student: Kameswara Anupundi Sponsor: NSF ERC Objective: Develop and apply the Large Eddy Simulation (LES) technique to study and predict cavitation and noise in hydraulic components such as pumps and valves. Develop acoustic models for cavitation noise. Explore passive and active strategies for cavitation and noise control. Instantaneous vortical structure colored by void fraction in a 3D LES of venturi. Method: Solve the fully compressible Navier-Stokes equations using high-fidelity numerical methods and stateof-the-art subgrid-scale models for turbulence and cavitation. Employ high-performance parallel computing to enable simulations of turbulent cavitating flows and noise. Employ commercial CFD codes to compliment in-house research codes and to interact with industry. Axial piston pump cavitation from Pumplinx software Results: Conducted LES of cavitating flow in a model venturi to study interactions between complex vortical flow structures and cavitation e.g. turbulence-cavitation interactions. Comparisons to experimental data underway.

4 Computational Hemodynamics: Congenital and Acquired Heart Disease Graduate Student: Dinesh Shetty Sponsor: CTLS Objective: Utilize state-of-the-art CFD to conduct flowfield investigations of hemodynamics related to congenital and acquired heart disease. Develop medical-device or other solutions for treatment. Method: Both commercial CFD codes e.g. Fluent, AcuSolve, etc., government codes, and in-house research codes. In-house code focus is on advanced numerics and turbulence modeling, such as large eddy simulation. Results: Conducted a series of simulations over the years related to blood flow through an idealized stenotic blood vessel. Developed a novel percutaneous expandable rotary blood pump for cavopulmonary assist in Fontan circulations. Developed new CFD software for patientspecific high-fidelity LES of pathological flows.

5 Large Eddy Simulation of Turbulent Combustion Graduate Student: Dinesh Shetty Sponsor: NSF Objective: Develop and apply new mixing models for conducting LES of turbulent reacting flows. Validate against experimental measurements. Method: High-fidelity LES is combined with the filtered mass density function (FMDF) approach and a particlebased Lagrangian Monte Carlo method. Detailed chemical kinetics are employed to study flame dynamics such as extinction and reignition. Parallel computing is employed to reduce computational times. Results: LES of a novel three-stream jet mixing problem are conducted with comparisons to recent experimental measurements for scalar mean and rms. A new fractal IEM mixing model is developed and shown to produce accurate results compared to other mixing models from the literature. Extensions to piloted non-premixed jet flames with reduced and detailed chemical kinetics are underway to further test the new mixing model under flame dynamics conditions.

6 High-Order Large Eddy Simulation of Fully-Nonhomogeneous Incompressible Turbulent Flows Graduate Student: Dinesh Shetty Sponsor: NSF Objective: Develop and apply new high-order LES code for fully-nonhomogeneous incompressible turbulent flows. Validate all aspects, especially subgrid-scale turbulence model, with experimental or numerical data. Method: 5 th -order Weighted Essentially Non-Oscillatory (WENO) scheme for convection with high-order centered schemes for diffusion. High-order, multigrid method for accurate and rapid Poisson equation solution. Inclusion of fictitious domain approach for handling complex geometries while still retaining structured Cartesian grid. OpenMP for parallel. Results: LES of cubic lid-driven cavity problem with comparison to published direct numerical simulation (DNS) results; LES of flow over v-gutter; bifurcation and chaos in rotating 2D lid-driven cavity problem; laminar flow through curved pipe with comparisons to experimental measurements; flow through model valve; etc.

7 Large Eddy Simulation of Stratified Turbulent Flows with Application to Oceanic Mixing Graduate Student: Nirinjan Ghaisas Sponsor: Fellowship Objective: Develop and apply LES for scalar mixing in stratified turbulent flows with applications to oceanic flows. Conduct benchmark simulations of test problems such as lock-exchange problem. Method: High-order numerics for incompressible Navier-Stokes equations under Boussinesque assumptions including scalar transport equation. Filtered mass density function approach for mixing involving particle-based Lagrangian Monte Carlo method. Results: LES of lock-exchange problem (below) using both Smagorinsky-based subgrid-scale models with Richardson number dependent eddy-viscosity versus filtered mass density function approach. Comparisons to previous direct numerical simulations and experimental data planned.