Numerical simulation of an axial compressor with nonaxisymmetric casing treatment

This study deals with unsteady numerical simulation of casing treatment in a stage of an axial compressor. The stall inception process is first investigated in the compressor with smooth wall. At low mass flow, the simulation shows the development of large reversed flow regions near the casing that leads to rotating stall. Then, a simulation is performed for a compressor stage with casing treatment. Despite a strong impact on the rotor casing flow, the operating range extension is low, meaning that other processes like rotor/stator interactions may play a role in the loss of stability

Extended integral wall-model for large-eddy simulations of compressible wall-bounded turbulent flows

International audienceWall-modeling is required to make large-eddy simulations of high-Reynolds number wall-bounded turbulent flows feasible in terms of computational cost. Here, an extension of the integral wall-model for large-eddy simulations (iWMLESs) for incompressible flows developed by Yang et al. ["Integral wall model for large eddy simulations of wall-bounded turbulent flows," Phys. Fluids 27(2), 025112 (2015)] to compressible and isothermal flows is proposed and assessed. The iWMLES approach is analogous to the von Karman-Pohlhausen integral method for laminar flows: the velocity profile is parameterized, and unknown coefficients are determined by matching boundary conditions obeying the integral boundary layer momentum equation. It allows non-equilibrium effects such as pressure gradient and convection to be included at a computing cost similar to analytical wall-models. To take into account density variations and temperature gradients, the temperature profile is also parameterized and the integral compressible boundary layer energy equation is considered. Parameterized profiles are based on the usual logarithmic wall functions with corrective terms to extend their range of validity. Instead of solving a set of differential equations as wall-models based on the thin boundary layer equation approach, a simple linear system is solved. The proposed wall-model is implemented in a finite-volume cell-centered structured grid solver and assessed on adiabatic and isothermal plane channel flows at several friction Reynolds and Mach numbers. For low Mach number cases, mean profiles, wall fluxes, and turbulent fluctuations are in agreement with those of Direct Numerical Simulation (DNS). For supersonic flows, the results are in good agreement with the DNS data, especially the mean velocity quantities and the wall friction, while standard analytical wall-models show their limits

HOW TO MAINTAIN EFFICIENCY ON VECTOR AND SMP PLATFORMS FOR LARGE AERODYNAMIC CALCULATIONS

Abstract. Large industrial aerodynamic calculations are nowadays performed indifferently on parallel vector computers or on clusters of SMPs. From a software design point of view it is crucial to ensure the best possible sustained megaflops rate on both platforms while for sake of minimal labour effort it is important to maintain only one source code. In this paper we describe software techniques that have been implemented to comply with these constraints. We first show how we succeeded to obtain a sustained megaflops rate that is independent of the mesh size. We then investigate the possibilities of using OpenMP in some of the main time consuming routines to replace the vectorization by fine grain parallelism to better exploit the shared memory available within each node of the SMP computers. Numerical experiments are reported on HP-Compaq, IBM SP based on Power 3 and Power 4 where tremendous savings can be obtained at a cost of a very little code change.

Space Adaptive Methods/Meshing

This chapter describes space adaptive approaches developed by six TILDA partners for the application in scale-resolving simulations. They are designed to provide sufficient spatial resolution in regions where required and to allow a lower resolution elsewhere for efficiency reasons. Adaptation techniques considered include mesh (h-refinement), order refinement of the spatial discretization (p-refinement) or a combination of both (hp-refinement). Furthermore, near-wall local mesh refinement, refinement using feature-based indicators and indicators obtained from the Variational Multiscale Method are considered

The T2K experiment

The T2K experiment is a long baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle θ13 by observing νe appearance in a νμ beam. It also aims to make a precision measurement of the known oscillation parameters, and sin22θ23, via νμ disappearance studies. Other goals of the experiment include various neutrino cross-section measurements and sterile neutrino searches. The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295 km away from J-PARC. This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem