Non-Newtonian effects in the peristaltic flow of a Maxwell fluid

We analyzed the effect of viscoelasticity on the dynamics of fluids in porous media by studying the flow of a Maxwell fluid in a circular tube, in which the flow is induced by a wave traveling on the tube wall. The present study investigates novelties brought about into the classic peristaltic mechanism by inclusion of non-Newtonian effects that are important, for example, for hydrocarbons. This problem has numerous applications in various branches of science, including stimulation of fluid flow in porous media under the effect of elastic waves. We have found that in the extreme non-Newtonian regime there is a possibility of a fluid flow in the direction {\it opposite} to the propagation of the wave traveling on the tube wall.Comment: to Appear in Phys. Rev. E., 01 September 2001 issu

Compact modeling of high-voltage LDMOS devices including quasi-saturation

The surface-potential-based compact transistor model, MOS Model 20 (MM20), has been extended with a quasi-saturation, an effect that is typical for LDMOS devices with a long drift region. As a result, MM20 extends its application range from low-voltage LDMOS devices up to high-voltage LDMOS devices of about 100V. In this paper, the new dc model of MM20, including quasi-saturation, is presented. The addition of velocity saturation in the drift region ensures the current to be controlled by either the channel region or the drift region. A comparison with dc measurements on a 60-V LDMOS device shows that the new model provides an accurate description in all regimes of operation, ranging from subthreshold to superthreshold, in both the linear and saturation regime. Thus, owing to the inclusion of quasi-saturation also the regime of high-gate and high-drain bias conditions for high-voltage LDMOS devices is accurately described

MM20 HVMOS Model : a surface-potential-based LDMOS model for circuit simulation (Chapter 3)

MOS Model 20 is an advanced public-domain compact LDMOS model, to be used for circuit simulation of high-voltage IC-designs. By combining the description of the MOSFET channel region with that for the drift region of an LDMOS device, MOS Model 20 includes all specific high-voltage aspects into one model. This chapter presents the physical background of the model, the model parameter extraction strategy, and ends with the verification in comparison to dc- and ac-measurements

Compact modeling of high-voltage LDMOS devices including quasi-saturation

The surface-potential-based compact transistor model, MOS Model 20 (MM20), has been extended with a quasi-saturation, an effect that is typical for LDMOS devices with a long drift region. As a result, MM20 extends its application range from low-voltage LDMOS devices up to high-voltage LDMOS devices of about 100V. In this paper, the new dc model of MM20, including quasi-saturation, is presented. The addition of velocity saturation in the drift region ensures the current to be controlled by either the channel region or the drift region. A comparison with dc measurements on a 60-V LDMOS device shows that the new model provides an accurate description in all regimes of operation, ranging from subthreshold to superthreshold, in both the linear and saturation regime. Thus, owing to the inclusion of quasi-saturation also the regime of high-gate and high-drain bias conditions for high-voltage LDMOS devices is accurately described

Net flow of compressible viscous liquids induced by travelling waves in porous media

The influence of ultrasonic radiation on the flow of a liquid through a porous medium is analyzed. The analysis is based on a mechanism proposed by Ganiev et al. according to which ultrasonic radiation deforms the walls of the pores in the shape of travelling transversal waves. Like in peristaltic pumping, the travelling transversal wave induces a net flow of the liquid inside the pore. In this article, the wave amplitude is related to the power output of an acoustic source, while the wave speed is expressed in terms of the shear modulus of the porous medium. The viscosity as well as the compressibility of the liquid are taken into account. The Navier–Stokes equations for an axisymmetric cylindrical pore are solved by means of a perturbation analysis, in which the ratio of the wave amplitude to the radius of the pore is the small parameter. In the second-order approximation a net flow induced by the travelling wave is found. For various values of the compressibility of the liquid, the Reynolds number and the frequency of the wave, the net flow rate is calculated. The calculations disclose that the compressibility of the liquid has a strong influence on the net flow induced. Furthermore, by a comparison with the flow induced by the pressure gradient in an oil reservoir, the net flow induced by a travelling wave can not be neglected, although it is a second-order effect