Wall jet similarity of impinging planar underexpanded jets

Fillingham, Patrick; Novosselov, Igor

doi:10.1016/j.ijheatfluidflow.2019.108516

Cited by 13 publications

(6 citation statements)

References 39 publications

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“…Guo et al [23] identified that the confinement of an impinging jet has no significant effect on the velocity decay rate, and the presence of the upper confinement plate accelerates the wall jet growth rates compared to those reported in the previous plane and radial wall jet experiments. However, the numerical study results of radial wall jet by Fillingham and Novosselov [24] exhibited an excellent agreement with those of plane wall jet reported by Naqavi et al [11] in terms of the evolution of both length and velocity scales. Bagherzadeh et al [2] reported that wall roughness influences the decay rate.…”

Section: Introductionsupporting

confidence: 79%

Numerical Study on Plane and Radial Wall Jets to Validate the 2D Assumption for an Idealized Downburst Outflow

Zhong

Yan

et al. 2021

Advances in Civil Engineering

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Turbulent radial and plane wall jets have been extensively investigated both experimentally and numerically over the past few decades. Previous studies mostly focused on the heat and mass transfers involved in jet flows. In this study, a comprehensive investigation was conducted on turbulent radial and plane wall jets, considering both jet spread and velocity decay for different parameters. The numerical results were compared with existing experimental measurements. The comparison focused on the velocity profile, jet spread, and velocity decay, and revealed that the Reynolds stress model (RSM) performs well in the simulation of both radial and plane wall jets. The results show that with a typical ratio of cloud base height to diameter for most downburst events, the effects of nozzle height and Reynolds number on the evolution of the radial wall jet are not significant. Both the jet spread and velocity decay exhibit a clear dependence on the Reynolds number below a critical value. Above this critical value, the plane wall jet becomes asymptotically independent of the Reynolds number. The co-flow was found to have a significant influence on the evolution of the plane wall jet. Comparatively, the jet spread and velocity of the radial wall jet were faster than those of the plane jet. For applications in civil engineering, it is valid to approximate the downburst outflow with a two-dimensional (2D) assumption from the perspective of longitudinal evolution of the flows.

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Section: Introductionsupporting

confidence: 79%

Numerical Study on Plane and Radial Wall Jets to Validate the 2D Assumption for an Idealized Downburst Outflow

Zhong

Yan

et al. 2021

Advances in Civil Engineering

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“…The velocity profiles were not measured for x < 10 mm due of likely probe interaction with the plasma zone (plasma length ∼7 mm). The flow is accelerated in the plasma discharge region [76] and as the wall jet propagates downstream, the velocity profile flattens due to viscous losses, momentum displacement [44] and specific to the EHD scenario, due to space charge effects. This jet-like expansion from the active electrode has been shown in similar pitot-tube experiments and the PIV experiments and some have modeled DBD actuators using wall-jet similarity [25,44,45].…”

Section: Velocity Characteristicsmentioning

confidence: 99%

“…Considering 2D geometry, the volume of ionization can be calculated from length and height measurements. The size and the charge density in the ionization zone can be considered analogous to virtual origin parameters in the wall jet literature [40][41][42]. DBD wall similarity analysis was recently proposed [43]; however, additional experimental data is needed to perform robust non-dimensional analysis.…”

Section: Introductionmentioning

confidence: 99%

Empirical relations for discharge current and momentum injection in dielectric barrier discharge plasma actuators

Tang¹,

Vaddi²,

Mamishev³

et al. 2021

J. Phys. D: Appl. Phys.

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Dielectric barrier discharge (DBD) plasma actuators with an asymmetric, straight edge electrode configuration generate a wall-bounded jet without moving parts. Mechanistic description of the interaction between the Coulombic forces and fluid motion as a function of DBD parameters remains unclear. This paper presents an experimental investigation of DBD actuators, including electrical current associated with microdischarges, plasma volume and the wall jet momentum over a range of alternating current (AC) frequencies (0.5–2 kHz) and peak-to-peak voltages up to 19.5 kV. Discharge current is measured with a high temporal resolution, plasma volume is characterized optically and the momentum induced by the DBD wall jet is computed based on the axial velocities measured downstream of the actuator using a custom-built pitot tube. Discharge current analysis demonstrated asymmetry between the positive and negative semi-cycle; both currents yielded a power–law relationship with empirical fitting coefficients. Plasma length varies linearly and volume quadratically with voltage. Although plasma length reached an asymptotic value at a higher frequency, the plasma volume grows due to the increasing height of the ionization region. In a simple two-dimensional configuration, the DBD wall jet momentum shows near-linear dependency with discharge current in the range of voltages and frequencies considered in this work. The presented empirical model characterizes the DBD wall jet momentum and the discharge current based only on the AC inputs. With the estimation of plasma volume, the model can be applied for determining more realistic boundary conditions in numerical simulations.

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“…The constriction bends to form an impinging jet on the upper surface of each baffle (Figure ). The behavior of impinging jets has been described in the literature, − and their comprehensive analysis is beyond the scope of this paper. However, for the purpose of this work, it is important to understand that the angled impinging jets create stagnation regions (Figure Ai, left).…”

Section: Resultsmentioning

confidence: 99%

Miniaturizing Wet Scrubbers for Aerosolized Droplet Capture

et al. 2021

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Aerosols dispersed and transmitted through the air (e.g., particulate matter pollution and bioaerosols) are ubiquitous and one of the leading causes of adverse health effects and disease transmission. A variety of sampling methods (e.g., filters, cyclones, and impactors) have been developed to assess personal exposures. However, a gap still remains in the accessibility and ease-of-use of these technologies for people without experience or training in collecting airborne samples. Additionally, wet scrubbers (large non-portable industrial systems) utilize liquid sprays to remove aerosols from the air; the goal is to "scrub" (i.e., clean) the exhaust of industrial smokestacks, not collect the aerosols for analysis. Inspired by wet scrubbers, we developed a device fundamentally different from existing portable air samplers by using aerosolized microdroplets to capture aerosols in personal spaces (e.g., homes, offices, and schools). Our aerosol-sampling device is the size of a small teapot, can be operated without specialized training, and features a winding flow path in a supersaturated relative humidity environment, enabling droplet growth. The integrated open mesofluidic channels shuttle coalesced droplets to a collection chamber for subsequent sample analysis. Here, we present the experimental demonstration of aerosol capture in water droplets. An iterative study optimized the non-linear flow manipulating baffles and enabled an 83% retention of the aerosolized microdroplets in the confined volume of our device. As a proofof-concept for aerosol capture into a liquid medium, 0.5−3 μm model particles were used to evaluate aerosol capture efficiency. Finally, we demonstrate that the device can capture and keep a bioaerosol (bacteriophage MS2) viable for downstream analysis.

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Wall jet similarity of impinging planar underexpanded jets

Cited by 13 publications

References 39 publications

Numerical Study on Plane and Radial Wall Jets to Validate the 2D Assumption for an Idealized Downburst Outflow

Numerical Study on Plane and Radial Wall Jets to Validate the 2D Assumption for an Idealized Downburst Outflow

Empirical relations for discharge current and momentum injection in dielectric barrier discharge plasma actuators

Miniaturizing Wet Scrubbers for Aerosolized Droplet Capture

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