School of Mechanical Engineering Efraim Shtainberg and Hen Balbas
SCHOOL OF MECHANICAL ENGINEERING SEMINAR
Wednesday, November 6, 2019 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
Hydrothermal processing of green seaweed biomass for biorefinery
MSc. Student of Prof. Avraham Kribus, Prof. Alexander Golberg
Seaweed conversion to biofuel is a major challenge for biorefineries. Common methods use acid or enzymatic hydrolysis, which are expensive and could damage the environment. Hydrothermal processing is an ecological technology for seaweed deconstruction, carbonization, and liquefaction. However, subcritical hydrolysis generates a wide range of products from a heterogeneous raw material such as seaweed biomass. In this work, the hydrothermal processing of the whole biomass directly, was compared to hydrothermal processing of individual extracted carbohydrates fractions (starch, cellulose), with the attempt to find the best sustainable process for optimal seaweeds monosaccharide release (glucose, xylose, rhamnose, fructose and glutaronic acid) for bioethanol production, bio-char and PHA. The effect of main process conditions such as temperature and treatment time (using sea water as reaction medium) on these yields was examined. The solid residue (hydrochar) heating value and chemical composition were also determined. The results enable to recognize the potential offered by sustainable biorefinery process.
MSc student of Prof. Issac Harari
In this work we employ Nitsche's method for weak enforcement of kinematic boundary conditions on problems of shear deformable plate bending. Suitable scaling of the rotations enables the use of a single stabilization parameter.
This approach is particularly useful for a locking-free formulation to the plate bending problem, in which transverse shear strains, instead of rotations, are treated as the primary unknowns alongside the deflections. Due to higher regularity requirements and unusual definition of boundary conditions, this change turns it difficult to use conventional finite elements methods.
Weak enforcement of kinematic boundary conditions with Nitsche's method enables the use of non-interpolatory basis functions and direct treatment of the unusual boundary conditions. Moreover, the domain geometry can be embedded in the mesh.
At first, Nitsche's method is applied to the conventional Reissner-Mindlin formulation, where the primary unknowns are deflections and rotations. In this case, domain geometry can be embedded in the mesh and non-interpolatory basis can be used. Good result are obtained for relatively thick plates. Nevertheless, erroneous results are obtained for thin plates due to transverse shear locking.
The locking-free formulation is investigated afterwards. In this case, with adequate mesh, good results can be obtained for thin plates as well.