Flow of Polyethylene. 2. Molecular Weight Dependence and Low-Temperature Anomaly, Macromolecules 29 (1996) 4115-4119.  Wang SQ, Drda PA, Inn YW: Exploring Molecular Origins of Sharkskin, Partial Slip, and Slope Change in Flow Curves of Linear Low Density Polyethylene, J. Rheol. 40 (1996) 875-898.  Pérez-Gonzáles J, de Vargas L, Pavlínek V, Hausnerová B, Sáha P: Temperature Dependent Instabilities in the Capillary Flow of a Metallocene Linear Low Density Polyethylene Melt, J. Rheol. 44 (2000) 441-451.  Han CD, Lamonte RR: A Study of Polymer Melt Flow
on a fast Fourier transformation (FFT) were used as
numeric tools applied to register and control the extru-
sion process. The flow of molten polymer was studied
under various processing conditions, giving an oppor-
tunity to split high frequency pressure fluctuations by
means of the autocorrelation function and fast Fourier
transform, and to create, in the future, a catalogue of data
which can be used to define particular distortions in tech-
Keywords: autocorrelation; flowinstabilities; frequency
Laser Doppler Velocimetry. In addition to the experimental ap-
proach, we used Computational Fluid Dynamics analysis to complete the flow
study. Numerical and experimental investigations reveal a class of instabilities of
the Taylor-Dean flow not previously observed in the Taylor-Couette flow due to
the cylinder rotation neither in the Dean flow due to the external pumping fluid.
KEYWORDS: flow, instabilities, shear wall, Taylor-Couette-Dean fluency
Taylor-Couette flow refers to the viscous flow in the fully filled annulus of
frequency, and the porosity of the
porous medium on the growth rate of the unstable mode is examined analitically. Routh's test of
stability is applied to confirm the above results.
PACS: 47.20.-k; 47.55.Mh; 47.65.+a; 52.30.-q; 52.35.-g.
Key words: Hydrodynamic Stability; Flows through Porous Media; Magnetohydrodynamics;
Plasma flow; Instabilities in Plasma.
The instability of a plane interface separating two
uniform superposed streaming fluids under varying
assumptions of hydrodynamics and hydromagnetics,
has been discussed by Chandrasekhar [1
Fluctuations of the non-Newtonian fluid flow in a Kenics static mixer: An experimental study
The measurements for a Kenics static mixer were carried out using Laser Doppler Anemometer (LDA). The test fluid was non-Newtonian solution of CMC, Blanose type 9H4. The velocity data inside the 5th Kenics insert were collected for the axial components at five levels of Reynolds number, Re = 20 ÷ 120. Velocity fluctuations were also analyzed in the frequency domain, after processing them with the help of the Fast Fourier Transform (FFT) procedure. The spectra of fluctuations provided information about level of the fluctuations in the observed range of Reynolds number. The obtained data were then also used to plot the velocity profiles for the fifth insert of the Kenics mixer. It was concluded that in the investigated range of Reynolds numbers (Re = 20 ÷ 120) a strong dependence of the velocity profiles and the flow fluctuations on Reynolds number was observed.
In this paper the application of model predictive control (MPC) to a two-mode model of the dynamics of the combustion process is considered. It is shown that the MPC by itself does not stabilize the combustor and the control gains obtained by applying the MPC algorithms need to be optimized further to ensure that the phase difference between the two modes is also stable. The results of applying the algorithm are compared with the open loop model amplitude responses and to the closed loop responses obtained by the application of a direct adaptive control algorithm. It is shown that the MPC coupled with the cost parameter optimisation proposed in the paper, always guarantees the closed loop stability, a feature that may not always be possible with an adaptive implementations.
Alaa-Eldin M. Adris
A novel fluidized bed membrane reactor with internal catalyst circulation is
being developed for the production of high-purity H2 from an autothermal re-
former. In order to provide guidance to pilot reactor testing, a cold model was
built to study the influence of reactor configuration on hydrodynamics and cata-
lyst circulation. It was found that catalyst circulation was reproducible, but that
parallel non-communicating flow channels could lead to flowinstability. Solids
circulation was found to be adequate for design of the
, thereafter velocity decreases. Another important observation is that for large n , flowinstability is marked which has been discussed above analyzing the limiting cases of the governing equation. Further, another contribution is well marked due to the presence of porous medium ( Fig. 3 ). Contribution of porous medium has two parts: Figure 2 (a) Horizontal velocity profiles (b) Horizontal velocity profiles Figure 3 Horizontal velocity profiles (i) k p , linear Darcy model (ii) F , nonlinear Forchheimer’s contribution. This shows that k p clearly reduces velocity for