Effects Of Wall Properties Research Articles

Effect of wall properties on the peristaltic flow of a third grade fluid in a curved channel with heat and mass transfer

Analysis has been carried out to study the heat and mass transfer effects on the peristaltic flow in a curved channel with compliant walls. Firstly, mathematical modelling is performed and then solution is obtained under the assumptions of long wavelength and low Reynolds number. Stream function, temperature and concentration fields are derived. The effects of emerging parameters in the obtained solutions are discussed.

Peristaltic Motion of Power-Law Fluid with Heat and Mass Transfer

The effects of wall properties and heat and mass transfer on the peristalsis in a power-law fluid are investigated. The solutions for the stream function, temperature, concentration and heat transfer coefficient are obtained. The axial velocity, temperature and mass concentration are studied for different emerging parameters.

Reflecting on posture

Cardiovascular parameters are most often assessed at rest, and in many cases in the supine position. This generally facilitates measurement procedures and obviates the need to account for external and usually complex confounding factors, other than those related to the inherent physiology being investigated. Although the supine resting position may be relevant for some part of circadian living, a large part of human activity is characterized by locomotion and the upright posture. Physiological adaptations to locomotion are studied under controlled conditions and at varying degrees of exercise. However, although primary measures of basic physiological quantities (e.g. stroke volume) can be obtained with some level of confidence at rest in supine position, it becomes extremely difficult to measure them during exercise, and so they are generally derived from other measurable quantities, with the associated errors. Notwithstanding this, the large body of work done so far on the physiological response to exercise has been extremely beneficial in elucidating both underlying and adaptive mechanisms for the function of the circulatory system. On the other hand, assessment of the changes occurring in cardiovascular variables when shifting from supine to standing is the procedure most commonly adopted to explore the response of cardiovascular control mechanisms to gravitational challenges, both when investigating physiological adaptations to the upright posture in healthy individuals and when assessing alterations in cardiovascular regulation in patients with a variety of diseases.

Effect of wall properties on the magnetohydrodynamic peristaltic flow of a Maxwell fluid with heat transfer and porous medium

AbstractThe elastic effect of the flexible walls is analyzed on the peristaltic motion of Maxwell fluid in a channel with heat transfer. An incompressible and magnetohydrodynamic (MHD) fluid fills the porous space. The series solution of the modeled problem is derived by considering small wave number. The influence of pertinent parameters is shown and discussed with the help of graphs. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010

Effect of Wall Surface Properties at Different Drying Kinetics on the Deposition Problem in Spray Drying

Current methods in alleviating the wall deposition problem in spray drying emphasize mainly controlling the stickiness of the drying particles and less attention is placed on the properties of the dryer wall. In this experimental study, the effect of wall surface properties on the deposition mechanism has been investigated. Properties considered in classifying different wall materials were surface energy, roughness, and dielectric properties. The model solution contained sucrose, representing low-molecular-weight sugars commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produced higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation of the drying chamber. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) tends to enhance deposition of dry particles because of attrition at the surface. Higher wall temperature was found to produce slightly more deposition. The results of this work give a general indication of the effect of wall material on the deposition problem and provide the fundamental understanding for further studies along this line. Proper selection of dryer wall material will provide potential alternatives for reducing the deposition problem.

A new model for study the effect of wall properties on peristaltic transport of a viscous fluid

The present study extends the two-dimensional analysis of peristaltic motion to include a compliant wall. The fluid-solid interaction problem is investigated by considering equations of motion of both the fluid and the deformable boundaries. The driving mechanism of the muscle is represented by assuming the channel walls to be compliant. A perturbation solution of the stream function for zeroth, first and second order in a small amplitude ratio is obtained. The phenomenon of the “mean flow reversal” is found to exist both at the center and at the boundaries of the channel. The effect of wall damping, wall elastance and wall tension on the mean axial velocity and reversal flow has been investigated. The numerical results show that the possibility of flow reversal increases by increasing the wall damping and decreases by increasing the wall elastance and wall tension.

Effect of wall properties on the behavior of bench‐scale reverse flow reactors

AbstractAlthough in big‐sized industrial fixed bed combustors the effect of the reactor wall in heat transfer phenomena can often be neglected, this is not so for smaller reactors. This article focuses on the study of the wall influence (especially the effect of the wall physical properties, such as thickness, heat capacity, and thermal conductivity) in the performance of bench scale reverse flow reactors. The reaction considered is the combustion of methane lean mixtures, very relevant for environmental applications, and useful as a model for VOC combustion. The study was carried out both experimentally (in a bench‐scale apparatus, equipped with a temperature control system that minimizes the heat exchange between the reactor and the surroundings) and by simulations (using a heterogeneous one‐dimensional model). The results confirm the importance of the wall effects on the performance of reverse flow reactors, and the influence of the physical properties of the wall is reported. So, higher wall thermal conductivity leads to a decrease in the reactor stability range. High wall heat capacity is also detrimental for the reactor performance, although its effect depends strongly on the range of the wall thermal conductivity considered. Finally, the stability range of reverse flow reactors is less affected by wall effects as the surface velocity increases. © 2006 American Institute of Chemical Engineers AIChE J, 2006

The effect of wall properties on the timbre of organ pipes

The influence of the wall vibrations on the timbre of flue organ pipes is one of the most disputed questions of organ building. Wall vibrations of metal and wooden labial pipes have been investigated by using miniature piezoelectric accelerometers and optical noncontact vibrometers. Both free and forced vibrations have been studied. Two sets of diapason pipes that were built with different wall properties but identical dimensions have been voiced to very similar speech and timbre, then vibration and sound spectra and attack transients were recorded. While large differences have been found in vibration spectra, hardly any change in the sound signal was observed. Similar investigations have been performed on wooden pipes. In this case the voicer ‘‘tuned’’ the side wall resonances in order to make the sound richer in overtones. The effect of this ‘‘tuning’’ on the vibration and sound spectra has been investigated. The ‘‘tuning’’ resulted in a significant increase of the vibration amplitude, while the radiated sound-pressure level decreased and the overtones became relatively stronger.