scholarly journals Steric Effects on Electroosmotic Nano-Thrusters under High Zeta Potentials

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3222
Author(s):  
Jiaxuan Zheng ◽  
Siyi An ◽  
Yongjun Jian
Keyword(s):  
Electric Potential ◽  
Steric Effect ◽  
Specific Impulse ◽  
Fluid Motion ◽  
Finite Size ◽  
Numerical Algorithms ◽  
Ionic Species ◽  
Double Layers ◽  
Power Ratio ◽  
Zeta Potentials

Here, space electroosmotic thrusters in a rigid nanochannel with high wall zeta potentials are investigated numerically, for the first time, considering the effect of finite size of the ionic species. The effect, which is called a steric effect, is often neglected in research about micro/nano thrusters. However, it has vital influences on the electric potential and flow velocity in electric double layers, so that the thruster performances generated by the fluid motion are further affected. These performances, including thrust, specific impulse, thruster efficiency, and the thrust-to-power ratio, are described by using numerical algorithms, after obtaining the electric potential and velocity distributions under high wall zeta potentials ranging from −25.7 mV to −128.5 mV. As expected, the zeta potential can promote the development of thruster performances so as to satisfy the requirement of space missions. Moreover, for real situation with consideration of the steric effect, the thruster thrust and efficiency significantly decrease to 5–30 micro Newtons and 80–90%, respectively, but the thrust-to-power ratio is opposite, and expends a short specific impulse of about 50–110 s.

scholarly journals Steric Effects on Space Electroosmotic Thrusters in Soft Nanochannels

Mathematics ◽  
2021 ◽  
Vol 9 (16) ◽  
pp. 1916
Author(s):  
Jiaxuan Zheng ◽  
Beinan Jia ◽  
Yongjun Jian
Keyword(s):  
Steric Effect ◽  
Specific Impulse ◽  
Finite Difference Methods ◽  
Ionic Species ◽  
Input Power ◽  
Steric Effects ◽  
Power Ratio ◽  
Total Input ◽  
Difference Methods ◽  
Ion Size

The influence of steric effects on the performances of space electroosmotic thrusters (EOTs) was numerically delineated in soft nanochannels for which its walls are covered with polyelectrolyte materials. The size effect of the ionic species, namely the steric effect, is neglected in many previous research studies, but it has vital influences on electrostatic potential and electroosmotic velocity, which is further introduced into the present study in order to understand and improve the exploration of nano electroosmotic thrusters with soft channels. The thruster’s thrust, specific impulse, total input power, thruster efficiency and thrust-to-power ratio are computed based on finite difference methods. It is found that the thruster’s thrust and specific impulse increase with the steric parameter while the efficiency and thrust-to-power ratio possess opposite trends due to the enhancement of Joule heating dissipation. For real situations with the consideration of ion size, although the thruster’s thrust could be promoted, the efficiency is only 30–70%, and the peak values of thrust-to-power ratio fade away.

scholarly journals Space Electroosmotic Thrusters in Ion Partitioning Soft Nanochannels

Micromachines ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 777
Author(s):  
Jiaxuan Zheng ◽  
Yongjun Jian
Keyword(s):  
Specific Impulse ◽  
Fluid Motion ◽  
Design Parameters ◽  
Fluid Viscosity ◽  
Power Ratio ◽  
Hydration Effect ◽  
Ion Partitioning ◽  
Solution Layer ◽  
The One ◽  
Electric Double Layer Thickness

Space electroosmotic thrusters (EOTs) are theoretically investigated in a soft charged nanochannel with a dense polyelectrolyte layer (PEL), which is considered to be more realistic than a low-density PEL. When the PEL is dense, its permittivity is smaller than the one of the electrolyte solution layer, leading to rearrangement of ions in the channel, which is denoted as the ion partitioning effect. It is noted that fluid viscosity becomes high within the PEL owing to the hydration effect. An analytical solution for electroosmotic velocity through the channel is obtained by utilizing the Debye–Hückel linearization assumption. Based on the fluid motion, thruster performances, including thrust, specific impulse, thrust-to-power ratio, and efficiency, are calculated. The ion partitioning effect leads to enhancement of the thruster velocity, while increase of the dynamic viscosity inside the PEL reduces the flow rate of the fluid. Therefore, these performances are further impacted by the dense soft material, which are discussed in detail. Moreover, changes or improvements of the thruster performances from the dense PEL to the weak PEL are presented and compared, and distributions of various energy items are also provided in this study. There is a good result whereby the increase in electric double layer thickness promotes the development of thruster performances. Ultimately, the simulated EOTs produce thrust of about 0 to 20 μN and achieve thruster efficiency of 90.40%, while maintaining an appropriate thrust–power ratio of about 1.53 mN/W by optimizing all design parameters.

Finite size effects of ionic species sensitively determine load bearing capacities of lubricated systems under combined influence of electrokinetics and surface compliance

Soft Matter ◽  
2017 ◽  
Vol 13 (37) ◽  
pp. 6422-6429 ◽  
Author(s):  
Kaustubh Girish Naik ◽  
Suman Chakraborty ◽  
Jeevanjyoti Chakraborty
Keyword(s):  
Size Effects ◽  
Mechanical Response ◽  
Finite Size ◽  
Ionic Species ◽  
Finite Size Effects ◽  
Load Bearing

Electrokinetic effects, including finite size of ions, can significantly alter the mechanical response of lubricated systems with a deformable wall.

Electrokinetic Phenomena and Surface Characteristics of Fly Ash Particles

1984 ◽  
Vol 43 ◽  
Author(s):  
R. I. A. Malek ◽  
D. M. Roy
Keyword(s):  
Fly Ash ◽  
Surface Characteristics ◽  
Ionic Species ◽  
Point Of Zero Charge ◽  
Fly Ashes ◽  
Electrokinetic Phenomena ◽  
Zeta Potentials ◽  
Low Calcium ◽  
High Calcium

AbstractThe zeta-potentials of two fly ashes were studied (high-calcium and low-calcium). It was found that they possess a point of charge reversal at pH = 10.5 to 12. The point of zero charge (low-calcium fly ash) was found to be at pH = 5. Furthermore, it shifted to more acidic values after the fly ash is aged in several calcium-containing solutions. The surficial changes that could happen when mixing fly ashes with cement and concrete were further evaluated by aging fly ashes in different solutions: Ca(OH)2, CaSO4·2H2O, NaOH and water solutions. Information from analyses for different ionic species in the solutions and characterization of the solid residues (XRD and SEM) was used in tentative explanations for the different behavior of the two types of fly ash in cementitious mixtures and concrete.

Macro-scale description of transient electro-kinetic phenomena over polarizable dielectric solids

2009 ◽  
Vol 620 ◽  
pp. 241-262 ◽  
Author(s):  
G. YOSSIFON ◽  
I. FRANKEL ◽  
T. MILOH
Keyword(s):  
Electric Field ◽  
Electrolyte Solution ◽  
Time Scale ◽  
Temporal Evolution ◽  
Fluid Motion ◽  
Double Layers ◽  
Uniform Field ◽  
Micro Particles ◽  
Macro Scale ◽  
Dielectric Solids

We have studied the temporal evolution of electro-kinetic flows in the vicinity of polarizable dielectric solids following the application of a ‘weak’ transient electric field. To obtain a macro-scale description in the limit of narrow electric double layers (EDLs), we have derived a pair of effective transient boundary conditions directly connecting the electric potentials across the EDL. Within the framework of the above assumptions, these conditions apply to a general transient electro-kinetic problem involving dielectric solids of arbitrary geometry and relative permittivity. Furthermore, the newly derived scheme is applicable to general transient and spatially non-uniform external fields. We examine the details of the physical mechanisms involved in the relaxation of the induced-charging process of the EDL adjacent to polarizable dielectric solids. It is thus established that the time scale characterizing the electrostatic relaxation increases with the dielectric constant of the solid from the Debye time (for the diffusion across the EDL) through the ‘intermediate’ scale (proportional to the product of the respective Debye- and geometric-length scales). Thus, the present rigorous analysis substantiates earlier results largely obtained by heuristic use of equivalent RC-circuit models. Furthermore, for typical values of ionic diffusivity and kinematic viscosity of the electrolyte solution, the latter time scale is comparable to the time scale of viscous relaxation in problems concerning microfluidic applications or micro-particle dynamics. The analysis is illustrated for spherical micro-particles. Explicit results are thus presented for the temporal evolution of electro-osmosis around a dielectric sphere immersed in unbounded electrolyte solution under the action of a suddenly applied uniform field, combining both induced charge and ‘equilibrium’ (fixed charge) contributions to the zeta potential. It is demonstrated that, owing to the time delay of the induced-EDL charging, the ‘equilibrium’ contribution to fluid motion (which is linear in the electric field) initially dominates the (quadratic) ‘induced’ contribution.

Viscoelectric Effect on the Electroosmotic Flow in Nanochannels With Heterogeneous Zeta Potentials

2018 ◽  
Author(s):  
Edson M. Jimenez ◽  
Federico Méndez ◽  
Juan P. Escandón
Keyword(s):  
Electroosmotic Flow ◽  
Fluid Velocity ◽  
Volumetric Flow Rate ◽  
Mass Conservation ◽  
Double Layers ◽  
Fluid Viscosity ◽  
Governing Equations ◽  
Flat Plates ◽  
Zeta Potentials ◽  
Poisson Boltzmann

In the present work, we realize a study about the influence of viscoelectric effect on the electroosmotic flow of Newtonian fluids in nanochannels formed by two parallel flat plates. In the problem, the channel walls have heterogeneous zeta potentials which follow a sinusoidal distribution; moreover, viscoelectric effects appear into the electric double layers when high zeta potentials are considered at the channel walls, modifying the fluid viscosity and the fluid velocity. To find the solution of flow field, the modified Poisson-Boltzmann, mass conservation and momentum governing equations, are solved numerically. In the results, combined effects from the zeta potential heterogeneities and viscosity changes yields different kind of flow recirculations controlled by the dephasing angle, amplitude and number of waves of the heterogeneities at the walls. The viscoelectric effect produces a decrease in the magnitude of velocity profiles and volumetric flow rate when the high zeta potentials are magnified. Additionally, the heterogeneous zeta potentials at the walls generate an induced pressure on the flow. This investigation extend the knowledge of electroosmotic flows under field effects for future mixing applications.

A sensitivity analysis of DC resistivity prospecting on finite, homogeneous blocks and columns

Geophysics ◽  
2007 ◽  
Vol 72 (6) ◽  
pp. F237-F247 ◽  
Author(s):  
Qi You Zhou
Keyword(s):  
Sensitivity Analysis ◽  
Electric Potential ◽  
Finite Size ◽  
Sensitivity Matrix ◽  
Subsurface Hydrology ◽  
Block Boundary ◽  
Scheme Design ◽  
Vertical Arrays ◽  
Analytic Expressions ◽  
Resistivity Inversion

Besides field applications to geophysical prospecting and subsurface hydrology, electrical resistivity tomography can be applied to finite-scale blocks in the laboratory to characterize the resistivity structure of the blocks and to monitor internal physical and chemical processes. This requires a fast and accurate calculation of the sensitivity matrix to perform a successful resistivity inversion for such blocks. However, the complex geometric shape and boundary and the finite size of the block limit the application of field-suitable sensitivity calculation methods to these blocks. As blocks and finite columns are often used in the laboratory experiments, this paper develops practical analytic expressions, based on the method of image charges, for the sensitivity matrix for these two types of homogenous bodies. The corresponding formulae for the electric potential distribution and theelectrode array coefficient are also presented. As a result of the theory, the effects of placing limits on the sum index in the electric-potential calculation can be analyzed, and a comparison of the theoretical and the numerically simulated electric potential is shown. The results demonstrate the correctness of the theory and indicate that even the addition of only one set of mirror current sources greatly reduces the effects of the block boundary on the electric-potential calculation. Finally, several interesting sensitivity distributions for cross-surface arrays on blocks, and for circular and vertical arrays on columns, are given. Although the formulae developed here are only valid for homogeneous blocks and columns, and an element of relatively small volume is required to permit a good approximation to the sensitivity, the theory is useful in the verification of numerically simulated results, in sensitivity-analysis for optimum probing-scheme design, and in successful resistivity inversion calculation for finite bodies.

Near-contact electrophoretic particle motion

1995 ◽  
Vol 288 ◽  
pp. 103-122 ◽  
Author(s):  
Michael Loewenberg ◽  
Robert H. Davis
Keyword(s):  
Slip Velocity ◽  
Point Contact ◽  
Reynolds Numbers ◽  
Spherical Particles ◽  
Double Layers ◽  
Electric Double Layers ◽  
Low Reynolds Numbers ◽  
Fluid Removal ◽  
Zeta Potentials ◽  
Analytical Formulae

The near-contact axisymmetric electrophoretic motion of a pair of spherical particles with thin electric double layers and differing surface zeta-potentials is analysed for low Reynolds numbers and moderate surface potentials. Near-contact electrophoretic motion of a spherical particle normal to a planar conducting boundary is analysed under the same assumptions. Pairwise motion is computed by considering touching particles in point contact; relative motion is described by a perturbation about the touching state using lubrication theory. Analytical formulae are derived for two particles of disparate sizes, and for the motion of a single particle towards a boundary; numerical calculations are performed for all size ratios. The results have a universal form with respect to the particle zeta-potentials. All results indicate that the electrophoresis is a much more efficient mechanism of near-contact motion than is buoyancy. An explanation for this finding is given in terms of the electro-osmotic slip velocity on the particle surfaces that facilitates fluid removal from between approaching surfaces.

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