Time-domain harmonic balance method for aerodynamic and aeroelastic simulations of turbomachinery flows

A time-domain Harmonic Balance method is applied to simulate the blade row interactions and vibrations of state- of-the-art industrial turbomachinery configurations. The present harmonic balance approach is a time-integration scheme that turns a periodic or almost-periodic flow problem into the coupled resolution of several steady computations at different time samples of the period of interest. The coupling is performed by a spectral time-derivative operator that appears as a source term of all the steady problems. These are converged simultaneously making the method parallel in time. In this paper, a non-uniform time sampling is used to improve the robustness and accuracy regardless of the considered frequency set. Blade row interactions are studied within a 3.5-stage high-pressure axial compressor representative of the high-pressure core of modern turbofan engines. Comparisons with reference time-accurate computations show that four frequencies allow a fair match of the compressor performance, with a reduction of the computational time up to a factor 30. Finally, an aeroelastic study is performed for a counter-rotating fan stage, where the rear blade is submitted to a prescribed harmonic vibration along its first torsion mode. The aerodynamic damping is analysed, showing possible flutter

A Pre-Landing Assessment of Regolith Properties at the InSight Landing Site

This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be ≥3--5 m thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission.Additional co-authors: Nick Teanby and Sharon Keda

Implicit schemes for unsteady Euler equations on unstructured meshes

Communication to : International Forum on Aeroelasticity and Structural Dynamics, Strasbourg (France), May 24-26, 1993SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1993 n.64 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Solution of 3-D Euler equations with unstructured meshes for aeroelasticity problems

Tire de : International forum on aeroelasticity and structural dynamics 1991, Aachen (Germany), June 3-6, 1991SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1991 n.62 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Velocity measurements in hypersonic flows

Communication to : 9th international symposium of unsteady, Lyon (France), September 04-07, 2000SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.2000 n.167 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Infection by Cryptosporidium parvum in renal patients submitted to renal transplant or hemodialysis

The frequency of infection by Cryptosporidium parvum was determined in two groups of renal patients submitted to immunosuppression. One group consisted of 23 renal transplanted individuals, and the other consisted of 32 patients with chronic renal insufficiency, periodically submitted to hemodialysis. A third group of 27 patients with systemic arterial hypertension, not immunosuppressed, was used as control. During a period of 18 months all the patients were submitted to faecal examination to detect C. parvum oocysts, for a total of 1 to 6 tests per patient. The results showed frequencies of C. parvum infection of 34.8%, 25% and 17.4%, respectively, for the renal transplanted group, the patients submitted to hemodialysis and the control group. Statistical analysis showed no significant differences among the three groups even though the frequency of C. parvum infection was higher in the transplanted group. However, when the number of fecal samples containing C. parvum oocysts was taken in account, a significantly higher frequency was found in the renal transplanted group