14,605 research outputs found
Radial convection of finite ion temperature, high amplitude plasma blobs
We present results from simulations of seeded blob convection in the
scrape-off-layer of magnetically confined fusion plasmas. We consistently
incorporate high fluctuation amplitude levels and finite Larmor radius (FLR)
effects using a fully nonlinear global gyrofluid model. This is in line with
conditions found in tokamak scrape-off-layers (SOL) regions.
Varying the ion temperature, the initial blob width, and the initial
amplitude, we found an FLR dominated regime where the blob behavior is
significantly different from what is predicted by cold-ion models. The
transition to this regime is very well described by the ratio of the ion
gyroradius to the characteristic gradient scale length of the blob.
We compare the global gyrofluid model with a partly linearized local model.
For low ion temperatures we find that simulations of the global model show more
coherent blobs with an increased cross-field transport compared to blobs
simulated with the local model. The maximal blob amplitude is significantly
higher in the global simulations than in the local ones. When the ion
temperature is comparable to the electron temperature, global blob simulations
show a reduced blob coherence and a decreased cross-field transport in
comparison with local blob simulations
Post-harvest sown catch crops – results from two years of organic field trials
Post-harvest sown catch crops should be sown as early as possible in order to obtain maximum biomass and nutrient uptake in the harvested crop, as biomass production decreased by 2-3.5 percent per day, when time of sowing was postponed throughout August. Furthermore, the winter hardy species included in these experiments had a tendency to yield less than the non-winter hardy catch crops. These experiments imply that early sown catch crops may become a biomass supplement for organic biogas production, provided sufficient yields are obtained and costs for harvest, transportation and storage are adequately low
Oxidation resistant porous material for transpiration cooled vanes
Porous metal sheet with controlled permeability was made by space winding and diffusion bonding fine wire. Two iron-chromium-aluminum alloys and three-chromium alloys were used: GE 1541 (Fe-Cr-Al-Y), H 875 (Fe-Cr-Al-Si), TD Ni Cr, DH 245 (Ni-Cr-Al-Si) and DH 242 (Ni-Cr-Si-Cb). GE 1541 and H 875 were shown in initial tests to have greater oxidation resistance than the other candidate alloys and were therefore tested more extensively. These two materials were cyclic furnace oxidation tested in air at 1800 and 2000 F for accumulated exposure times of 4, 16, 64, 100, 200, 300, 400, 500, and and 600 hours. Oxidation weight gain, permeability change and mechanical properties were determined after exposure. Metallographic examination was performed to determine effects of exposure on the porous metal and electron beam weld joints of porous sheet to IN 100 strut material. Hundred hour stress rupture life and tensile tests were performed at 1800 F. Both alloys had excellent oxidation resistance and retention of mechanical properties and appear suitable for use as transpiration cooling materials in high temperature gas turbine engines
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