532 Mechanik der Fluide; Mechanik der Flüssigkeiten
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- English (11)
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- Acetylene (1)
- Detaching (1)
- Ethane (1)
- Ethylene (1)
- Hydrogenation (1)
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- Lattice Boltzmann (1)
- Multiphase flow (1)
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- Pd on alumina (1)
Lattice Boltzmann method (LBM) simulations of incompressible flows are nowadays common and well-established. However, for compressible turbulent flows with strong variable density and intrinsic compressibility effects, results are relatively scarce. Only recently, progress was made regarding compressible LBM, usually applied to simple one and two-dimensional test cases due to the increased computational expense. The recently developed semi-Lagrangian lattice Boltzmann method (SLLBM) is capable of simulating two- and three-dimensional viscous compressible flows. This paper presents bounce-back, thermal, inlet, and outlet boundary conditions new to the method and their application to problems including heated or cooled walls, often required for supersonic flow cases. Using these boundary conditions, the SLLBM's capabilities are demonstrated in various test cases, including a supersonic 2D NACA-0012 airfoil, flow around a 3D sphere, and, to the best of our knowledge, for the first time, the 3D simulation of a supersonic turbulent channel flow at a bulk Mach number of Ma=1.5 and a 3D temporal supersonic compressible mixing layer at convective Mach numbers ranging from Ma=0.3 to Ma=1.2. The results show that the compressible SLLBM is able to adequately capture intrinsic and variable density compressibility effects.
This study explores the tuning of a Pd/Al2O3 hydrogenation catalyst for the selective removal of trace acetylene from ethylene-rich feeds by coating the catalyst with non-functionalized and functionalized ionic liquids (denoted as SCILL and Advanced SCILL materials, respectively). These materials were tested in an automated continuous hydrogenation rig converting 3300 ppm of acetylene in excess ethylene, a gas mixture mimicking a technical front-end steam cracker feed composition. While the sulfonic-acid-functionalized IL coating resulted in a highly active but very unselective catalyst converting mainly ethylene to ethane, an Advanced SCILL catalyst prepared from a nitrile-functionalized IL reduced the acetylene concentration down to less than 1 ppm, while leaving over 99% of the ethylene untouched. We also examined the potential transformations of the IL layer under reaction conditions by means of 1H NMR. Except for a ketone-functionalized IL, which was inherently labile, all tested ILs primarily underwent C2-ethylation or remained unaltered. Our findings highlight the great potential of functionalized ILs in modifying heterogeneous hydrogenation catalysts.
Characterization methods of pressure sensitive adhesives (PSA) originate from technical bonding and do not cover relevant data for the development and quality assurance of medical applications, where PSA with flexible backing layers are adopted to human skin. In this study, a new method called RheoTack is developed to determine (mechanically and optically) an adhesion and detaching behavior of flexible and transparent PSA based patches. Transdermal therapeutic systems (TTS) consisting of silicone-based PSAs on a flexible and transparent backing layer were tested on a rotational rheometer with an 8 mm plate as a probe rod at retraction speeds of 0.01, 0.1, and 1 mm/s with respect to their adhesion and detaching behavior in terms of force-retraction displacement curves. The curves consist of a compression phase to affirm wetting; a tensile deformation phase intercepting stretching, cavity, and fibril formation; and a failure phase with detaching. Their analysis provides values for stiffness, force, and displacement of the beginning of fibril formation, force and displacement of the beginning of a failure due to fibril breakage and detaching, as well as corresponding activation energies. All these parameters exhibit the pronounced dependency on the retraction speed. The force-retraction displacement curves together with the simultaneous video recordings of the TTS deformation from three different angles (three cameras) provide deeper insight into the deformation processes and allow for interpreting the properties’ characteristics for PSA applications.
