Considering CFD approach, the flow fields were simulated, and compared with local pressure and previous velocity measurements. In laminar regime, the pressure fluctuation increases with the mixing rate (0 to 30 Hz), but remains negligible (below 30 mbar) due to the sharp decline of the periodic contribution. The empirical correlations are established to estimate their intensities as a function of rotation frequency and radial position.

Wherein, periodic pressure fluctuations dominate as opposed to random pressure signals. In turbulent regime, The 'resonance frequency' of Imp 1 was clearly identified at 21.1 Hz, which induces the maximum pressure fluctuation that cannot be neglected during microfiltration process. The instantaneous pressure is decomposed into the time-averaged pressure and its fluctuating quantities using Statistical Analysis (SA), Probability Distribution Function (PDF) and Fast Fourier Transform (FFT). Mean radial pressure and core velocity coefficient (k) were quantified versus flowrate, viscosity, radial position, impeller shape and mixing rate. For specific operating conditions (feeding flowrate, mixing rate, viscosity), the increase of temperature (inlet/outlet) superior to 5℃ may be damageable for cell culture growth or bioproduction.For semi-local and local approaches, the local pressure at the membrane surface was measured with a specially designed and instrumented porous substrate. The balance between nominal power and thermal dissipation was investigated. The calculated mechanical power with the empirical correlation of local shear stress was underestimated. For global approach, friction and power consumption curves were established as a function of mixing and feeding Reynolds number. Then, the experimental data were confronted with numerical simulations. Global, semi-local and local parameters have been characterized during experimental campaigns with Newtonian model fluids and 3 different impellers (Imp 1, 2 and 3). Combined with previous studies, the investigation of hydrodynamics in laminar and turbulent regimes were furtherly scrutinised to answer new scientific questions. The objectives are to propose an exhaustive benchmarking and classification of DF modules, to develop an experimental device for local and instantaneous measurements of the driving force (pressure), then to describe pressure fluctuations using 3 different theoretical approaches, and finally to validate Computational Fluid Dynamics (CFD) simulation in laminar and turbulent regimes. This PhD is devoted to exploring a technology called Rotating and Vibration Filtration (RVF) to get insight into its complex hydrodynamics at global and local scales, to understand and to explain its performances in membrane bio-reactor (MBR). Permeate fluxes were consistently much higher than in classic cross-flow filtration.ĭynamic filtration (DF) exhibits superior performances (high permeate flux, fouling limitation) to dead-end and cross-flow filtrations for various applications (water treatment, food engineering, bioprocess engineering). Fouling was limited to the central part of the membrane at 1,500 rpm and disappeared completely for a disk equipped with vanes. This factor rose to 64% when the disk was equipped with small vanes.

The inviscid fluid core in the axial gap was observed to rotate at 42% of angular velocity with a smooth disk. The permeate flux was independent of the axial gap (disk to membrane), but increased when the radial gap (from disk to housing) was raised from 2 to 5 mm. Several inlet and outlet configurations were tested. The shear stress on the stationary membrane in the laminar boundary-layer regime was estimated from a similarity solution, and in the turbulent regime from the friction coefficient for a flat plate. The test fluid was a calcium carbonate suspension (4.7-μm mean particle diameter), and the membranes were in nylon (0.2-μm mean pore diameter) and PVDF (0.1 and 0.18 μm). This module consists of a disk rotating at speeds up to 2,000 rpm inside a cylindrical housing equipped with a fixed flat membrane. The influence of internal geometry and angular velocity on the performance of a rotating-disk filtration device is described.

Old rotating disk animation desk