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Applying a high-voltage electric field in a flow (electro-hydrodynamics or EHD) is a highly effective approach to locally accelerate a fluid to a desired speed. In this paper, a finite volume implementation is used to study the fluid flow around a fixed cylinder at a low Reynolds number. Two pairs of wire-plate electrodes are used to generate the electric field for fluid acceleration. Two Reynolds numbers are considered: Re=40, 100. We show that by increasing the Reynolds number, the relative effect of EHD is decreased. Further, we study the change in drag force due to EHD actuation. Finally, we showed that under certain voltage, electrode placement and Reynolds number the EHD fluid acceleration does not increase the total drag on the cylinder and yet leads to an increase in the total streamwise momentum transfer by augmenting the velocity at the top of the boundary layer. [ABSTRACT FROM AUTHOR]

When charged particles are exposed to an electric field the well-known Coulomb force acts on them. In this investigation, this force is utilized to induce vertical motion of spherical steel particles submerged in a dielectric liquid. The interelectrode space of a two parallel electrode system is filled with the liquid and dispersed steel particles, which become charged after contact with the electrodes. Experiments were carried out to measure the effect of this particle motion on the heat transfer between an electrode surface and an adjacent stagnant dielectric liquid. In order to interpret the experimental data, the dynamics of particles was analytically studied for low particle volume concentrations. Experimental results demonstrate significant heat transfer enhancement on low viscosity dielectric liquids. A detailed discussion is presented on the possible mechanisms responsible for such an enhancement. [ABSTRACT FROM AUTHOR]

An experimental study of stationary and non-stationary dielectric barrier discharge (DBD) plasma actuator is presented to control the flow around a NACA0024 airfoil. First, an induced air velocity of ~5 m/s is generated on a flat plate in still air using an AC-DBD actuator to find the optimal setup of the actuator (voltage, frequency, electrode width and gap size). Using the same actuator in the optimal position/setup on a NACA0024 airfoil at Reynolds number of 0.48 106, we are able to increase the stall angle of the airfoil to 18°, compared to 16° in no-actuator state. Furthermore, during the plasma actuation, the lift is increased by up to 5%. We show that non-stationary actuation, while yielding a performance similar to stationary actuation, leads to a considerable reduction of ~51% in plasma power consumption. [ABSTRACT FROM AUTHOR]

In this paper, the air flow around a blunt flat plate with a rounded leading edge has been experimentally examined with and without the presence of a plasma actuator. Tests have been conducted with Reynolds numbers ranging from 104 to 105. Significant phenomena in this flow field is the flow separation at the leading edge of the body, which called separation bubble. There are two considerably dimensionless parameters in this experiment. One of them is the leading edge radius ratio to body thickness and other one is the ratio of maximum velocity induced by plasma actuator to free stream velocity. Geometries with the values of R/D=0, 1/16, 2/16, 4/16 were tested. For each geometry, the effectiveness of plasma actuator on the separation bubble is studied in different values of velocity ratio. The results show that, the effect of plasma actuator for the geometry with sharp edge (R/D=0), is negligible, while in geometry with rounded edge, the plasma actuator has significant effect on the separation bubble domain. This effectiveness is enhanced, by increasing of leading edge radius and velocity ratio, so that in rounded edge geometry (R/D=4/16) length of separation bubble is reduced about 75%. [ABSTRACT FROM AUTHOR]

Abstract: An experimental study was carried out to investigate heat transfer and friction factor characteristics of γ-Al2O3/water nanofluid through circular tube with twisted tape inserts with various thicknesses at constant heat flux. In this work, γ-Al2O3/water nanofluids with two volume concentrations of 0.5% and 1% were used as the working fluid. The twist ratio of twisted tape remained constant at 3.21, while the thicknesses were changed through three values of 0.5 mm, 1 mm and 2 mm. The experiments were performed in laminar flow regime from 150 to 1600 Reynolds numbers. Results indicated that twisted tape inserts enhanced the average convective heat transfer coefficient, and also more the thickness of twisted tape is more the enhancement of convective heat transfer coefficient is. Also, the highest enhancement was achieved at maximum volume concentration. Results showed that nanofluids have better heat transfer performance when utilized with thicker twisted tapes. At the same time, the increase in twisted tape thickness leads to an increase in friction factor. In the end, the combined results of these two phenomena result in enhanced convective heat transfer coefficient and thermal performance. Finally, two new correlations were offered for Nusselt number and thermal performance based on our experimental observation. [Copyright &y& Elsevier]

In this paper, characteristics of the flow induced in the boundary layer by an AC-Dielectric Barrier Discharge (DBD) plasma actuator are compared against those of a DC-corona wind actuator. This is achieved by visualization of the induced flow using smoke injection and measuring the horizontal induced velocity. Our measurements show that the maximum induced velocity of an AC-DBD actuator is about one order of magnitude larger than that of a DC-corona actuator. For an AC-DBD actuator, the induced velocity is maximized on the plate surface while for a DC-corona actuator the induced velocity peaks at about 20mm above the surface. Using flow visualization, we demonstrate that the induced velocity of an AC-DBD actuator is parallel to the surface, while the induced velocity of a DC-corona actuator has components perpendicular to surface. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, hydrodynamics and heat transfer characteristics of γ-Al2O3 nanoparticles inside a circular tube in laminar flow with constant heat flux was investigated. For this purpose, γ-Al2O3 nanoparticles with 15 nm diameter and distilled water as base fluid were used. The primary objective is to evaluate the effect of different volume concentration on convective heat transfer. In addition, the effect of volume concentration is also studied on friction factor. Increasing the particle volume fraction leads to enhancement of convective heat transfer coefficient. Results revealed that the average heat transfer coefficient increased 6.8% with 0.5% volume concentration and enhanced 19.1% at 1% volume concentration in comparison with distilled water. More the heat flux is more the heat transfer coefficient is. From the results, there is no significant change of friction factor for nanofluids in comparison with base fluid. A new correlation was proposed based on our experimental observation in order to present a deep insight into the current issue. [Copyright &y& Elsevier]

The effects of a nonuniform electric field on the formation, detachment, and breakup of a single inert bubble surrounded by a dielectric liquid were studied experimentally and numerically. In experiments, air bubbles were injected into kerosene at a constant flow rate through an orifice at the bottom wall of the test cell. The liquid was subjected to a nonuniform electric field, applied between the horizontal and vertical electrodes. During the experiments, the behavior of bubbles was recorded continuously, and the position, shape, and volume departure of the bubbles were digitally extracted from the sequential frames with the aid of graphical software. The experimental results show that in the presence of the nonuniform electric field, bubbles take a prolate shape and skew to the opposite direction of the ground electrode. With an increase in the electric potential, the bubble growth time and departure volume will decrease continuously. Bubble breakup is also observed at high enough voltages. As a further study, a 3-D numerical simulation was performed, using a commercial finite element code (Comsol Multiphysics) to determine the distribution of electric stresses along the bubble surface. The numerical results show that the nonuniform electric field generates some inhomogeneous stresses at the bubble surface. The bubble is compressed and deviated by the horizontal component and elongated by the vertical component. Numerical outcomes prove the physical behavior of the bubble observed in the experiments. [ABSTRACT FROM AUTHOR]

Controlling and manipulating liquid jets are of great interest in practical and scientific aspects. In the present work effects of transverse uniform electric field on behaviour of liquid jet, streaming downward due to the gravity, is experimentally investigated in details by performing a precise image processing of the extracted high speed video frames. In the experiments, by altering liquid flow rate and applied electric field strength, authors have tried to study the interplay of electrical and hydrodynamic forces which are indeed the main factors acting on the jet behaviour e.g. deflection, rhythmic motion, breakup mechanism and satellite droplets formation. Major aim of this study is to manipulate liquid jet so as to attain uniformly sized droplets by removing satellite droplets which has potential applications in various industrial and laboratorial units. This procedure was performed by applying dielectrophoretic force to the water jet as a polar liquid. Furthermore the droplets and also satellites behaviour, influenced by transverse electric field, have been investigated thoroughly. [ABSTRACT FROM AUTHOR]

Background: The mechanisms of the function of interferon beta (IFN-β) and natalizumab (NTZ) in multiple sclerosis (MS) patients have not yet been fully understood. Over the past decades, many studies have been conducted to evaluate gene expression changes especially regulatory non-coding RNAs such as microRNAs (miRNAs) following therapy in MS patients., Objective: To assess the changes in the expression of miR-20b in MS patients treated with IFN-β or NTZ., Methods: Sixty patients with relapsing-remitting MS (RRMS) and 30 healthy controls (HCs) were enrolled. The patients were categorized as untreated (N=20), IFN-β-treated (N=20), and NTZtreated (N=20). For the expression analysis, real-time PCR was performed on the whole blood. The bioinformatic tools were applied for signaling pathways enrichment analysis of miR-20b targetome., Results: The relative expression of miR-20b was significantly downregulated in the untreated patients compared with the HCs (-1.726-fold, p<0.001), while IFN-β-treated and NTZ-treated patients showed no statistical difference compared with the HCs (0.733-fold, p=0.99 for IFN-β and 1.025-fold, p=0.18 for NTZ). This indicates the restoration of miR-20b expression to normal level in the treated patients. Additionally, in silico analysis demonstrated that the Jak-STAT signaling pathway is enriched with miR-20b targets (p<0.0001)., Conclusion: Our findings suggest that the positive effects of IFN-β and NTZ in the RRMS patients could be potentially mediated by returning miR-20b expression to baseline.

Objective: Researchers are actively investigating new diagnostic and prognostic biomarkers that offer improved sensitivity and specificity for systemic lupus erythematosus (SLE). One area of interest is DNA methylation changes. Previous studies have shown a connection between the RUNX3 gene dysfunction and SLE. In this study, the focus was on examining the methylation level of the RUNX3 promoter in peripheral blood mononuclear cells (PBMCs) of SLE patients and healthy individuals., Methods: A total of 80 individuals diagnosed with SLE from Iran, along with 77 healthy individuals, were included. The methylation levels of the RUNX3 gene in the extracted DNA were evaluated using the MethyQESD method. To determine the diagnostic effectiveness of the RUNX3 promoter methylation level, a receiver operating characteristic (ROC) curve was generated., Results: The methylation of the RUNX3 promoter was found to be significantly higher in patients with SLE compared to healthy individuals ( p < .001). This difference in methylation levels was observed between SLE patients and healthy individuals and between SLE patients with renal involvement and those without renal involvement (86.29 ± 10.30 vs 40.28 ± 24.21, p < .001). ROC analyses revealed that the methylation level of the RUNX3 promoter had a diagnostic power of 0.769 [95% CI (0.681-0.814)] for SLE. Additionally, there was a positive correlation between the RUNX3 methylation level and levels of creatinine and C4., Conclusion: The findings of this study emphasize the potential use of RUNX3 methylation levels in PBMCs of SLE patients as biomarkers for diagnosing the disease, predicting renal damage, and assessing disease activity., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.