Jet-like Flow Research Articles

Observations of Interannual Equatorial Freshwater Jets in the Western Pacific

AbstractObservations of TRITON moored array salinity and temperature in the very wet western equatorial Pacific at 137°E, 147°E, and 156°E since the late 1990s reveal the importance of rainfall to the interannual flow and El Niño–Southern Oscillation (ENSO) dynamics. Past work has shown that in this region a fresher surface isohaline layer is embedded in a thicker isothermal layer. Array estimates of dynamic height relative to the 50–70-m isothermal layer depth (ILD) indicate a near-surface salinity-driven contribution to the monthly sea level anomaly that is uncorrelated with, and smaller than, monthly anomalous sea surface height (SSH) estimated from altimeter data. Despite the smaller size of , its meridional gradient dominates the total sea level meridional gradient. Thus, the corresponding shallow equatorially trapped interannual freshwater jet dominates the near-surface zonal interannual flow. This jetlike flow has a meridional scale of only about 2°–3° of latitude, an amplitude of 23 cm s−1, and is associated with the zonal back and forth displacement of the western equatorial warm/fresh pool that is fundamental to El Niño. The jet is not directly forced by the interannual freshwater surface flux but rather by wind stress anomalies that are mostly east of the warm/fresh pool edge during La Niña and mostly west of it during El Niño. A conceptual coupled ocean–atmosphere instability model is proposed to understand these observations. Calculations show that Aquarius satellite sea surface salinity (SSS) data match the TRITON in situ data well and that the satellite SSS can be used to estimate , and hence , geostrophically.

Flow Actuation by DC Surface Discharge Plasma Actuator in Different Discharge Modes

Aerodynamic flow control phenomena were investigated with a low-current DC surface discharge plasma actuator. The plasma actuator was found to operate in three different discharge modes with similar discharge currents of about 1 mA or less. Stable continuous DC discharge without audible noise was obtained at higher ballast resistances and lower discharge currents. However, even with continuous DC power input, a low-frequency self-pulsed discharge was obtained at lower ballast resistances, and a high-frequency self-pulsed discharge was obtained at higher set-point currents and higher ballast resistances, both with audible noise. The Schlieren image reveals that the low-frequency self-pulsed mode produces a synthetic jet-like flow implying that a gas heating effect plays a role, even though the discharge current is small. The high-frequency self-pulsed mode produces pulsed jets in a tangent direction, and the continuous DC mode produces a steady straight pressure wave. Particle image velocimetry (PIV) images reveal that the induced flow field by the low-frequency self-pulsed mode has flow propagating in the radial direction and centered between the electrodes. The high-frequency self-pulsed mode and continuous DC mode produce flow from the anode to the cathode. The perturbed region downstream of the cathode is larger in the high-frequency self-pulsed mode with similar maximum speeds.

An experimental study of multiple zonal jet formation in rotating, thermally driven convective flows on a topographic beta-plane

A series of rotating, thermal convection experiments were carried out on the Coriolis platform in Grenoble, France, to investigate the formation and energetics of systems of zonal jets through nonlinear eddy/wave-zonal flow interactions on a topographic β-plane. The latter was produced by a combination of a rigid, conically sloping bottom and the rotational deformation of the free upper surface. Convection was driven by a system of electrical heaters laid under the (thermally conducting) sloping bottom and led to the production of intense, convective vortices. These were observed to grow in size as each experiment proceeded and led to the development of weak but clear azimuthal jet-like flows, with a radial scale that varied according to the rotation speed of the platform. Detailed analyses reveal that the kinetic energy-weighted radial wavenumber of the zonal jets, kJy, scales quite closely either with the Rhines wavenumber as kJy ≃ 2(βT/2urms)1/2, where urms is the rms total or eddy velocity and βT is the vorticity gradient produced by the sloping topography, or the anisotropy wavenumber as kJy≃1.25(βT3/ϵ)1/5, where ϵ is the upscale turbulent energy transfer rate. Jets are primarily produced by the direct quasi-linear action of horizontal Reynolds stresses produced by trains of topographic Rossby waves. The nonlinear production rate of zonal kinetic energy is found to be strongly unsteady, however, with fluctuations of order 10-100 times the amplitude of the mean production rate for all cases considered. The time scale of such fluctuations is found to scale consistently with either an inertial time scale, τp∼1./urmsβT, or the Ekman spin-down time scale. Kinetic energy spectra show some evidence for a k−5/3 inertial subrange in the isotropic component, suggestive of a classical Kolmogorov-Batchelor-Kraichnan upscale energy cascade and a steeper spectrum in the zonal mean flow, though not as steep as k−5, as anticipated for fully zonostrophic flow. This is consistent with a classification of all of these flows as marginally zonostrophic, as expected for values of the zonostrophy parameter Rβ ≃ 1.6–1.7, though a number of properties related to flow anisotropy were found to vary significantly and systematically within this range.

Eulerian Volume Transport Induced by Spatially Damped Internal Equatorial Kelvin Waves

AbstractThe Eulerian volume transport in internal equatorial Kelvin waves subject to viscous attenuation is investigated theoretically by integrating the horizontal momentum equations in the vertical. In terms of small perturbations, the time-averaged horizontal transports are determined to second order in wave steepness. The total Lagrangian volume transport in this problem consists of a Stokes transport plus an Eulerian transport. It is known that the Stokes transport, that is, the vertically integrated Stokes drift, in inviscid internal equatorial Kelvin waves vanishes identically in the rigid-lid approximation for arbitrary vertical variation of the Brunt–Väisälä frequency. The present study considers spatial wave damping due to viscosity. The Stokes transport still becomes zero, but now the radiation stresses due to decaying waves become source terms for the Eulerian mean transport. Calculations of the wave-induced Eulerian transport yield a jetlike symmetric mean flow along the equator from west to east for each baroclinic component, with compensating westward flows on both sides. The flow system scales as the internal equatorial Rossby radius in the north–south direction. The total eastward part of the Eulerian volume flux centered about the equator is estimated to about 0.2 Sv (1 Sv ≡ 106 m3 s−1) for the first baroclinic mode.

PROPERTIES OF CHROMOSPHERIC EVAPORATION AND PLASMA DYNAMICS OF A SOLAR FLARE FROMIRISOBSERVATIONS

Dynamics of hot chromospheric plasma of solar flares is a key to understanding of mechanisms of flare energy release and particle acceleration. A moderate M1.0 class flare of 12 June, 2014 (SOL2014-06-12T21:12) was simultaneously observed by NASA's Interface Region Imaging Spectrograph (IRIS), other spacecraft, and also by New Solar Telescope (NST) at the BBSO. This paper presents the first part of our investigation focused on analysis of the IRIS data. Our analysis of the IRIS data in different spectral lines reveals strong redshifted jet-like flow with the speed of ~100 km/s of the chromospheric material before the flare. Strong nonthermal emission of the C II k 1334.5 A line, formed in the chromosphere-corona transition region, is observed at the beginning of the impulsive phase in several small (with a size of ~1 arcsec) points. It is also found that the C II k line is redshifted across the flaring region before, during and after the impulsive phase. A peak of integrated emission of the hot (1.1 MK) plasma in the Fe XXI 1354.1 A line is detected approximately 5 minutes after the integrated emission peak of the lower temperature C II k. A strong blueshift of the Fe XXI line across the flaring region corresponds to evaporation flows of the hot chromospheric plasma with a speed of 50 km/s. Additional analysis of the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data supports the idea that the upper chromospheric dynamics observed by IRIS has features of "gentle" evaporation driven by heating of the solar chromosphere by accelerated electrons and by a heat flux from the flare energy release site.

DDES study of the aerodynamic forces and flow physics of a delta wing in static ground effect

During takeoff and landing phases, the performance of an aircraft with delta wing configuration is significantly influenced by the ground effect (GE). In this paper, the static ground effect (SGE) of a 65° sweep delta wing (VFE-2) with sharp leading edge at α=20° is investigated by the Delayed Detached Eddy Simulation (DDES) grounded on Spalart–Allmaras (S–A) turbulence model. With the ride height decreasing, the lift, drag and nose-down pitching moment of the delta wing increase nonlinearly, and the majority of aerodynamic force increments in SGE are from the windward side of the delta wing. With the ride height decreasing, under the windward side, the flow is severely blocked resulting in the augmentation of static pressure, and the increasing span wise flow near the leading edge strengthens the shear layer and the leading edge vortex over the leeward side. The strengthened leading edge vortex induces lower pressure over the leeward side, and moves outside along the span wise direction. With the ride height decreasing, the jet-like flow in the primary vortex core is accelerated before the vortex breakdown, and the wake-like flow in the primary vortex core is decelerated after the vortex breakdown.

Three-component particle velocity measurements in the bottom section of a riser

Abstract Coincident three-component particle velocity measurements are performed in an almost 9 m high cylindrical riser (internal diameter 0.10 m) of a pilot-scale cold-flow Circulating Fluidized Bed set-up, using two Laser Doppler Anemometry (LDA) probes. Experiments are performed with superficial gas velocities of 3.5 m/s and 5.3 m/s near the solids inlet line and with an average solids volume fraction of 0.0002. The particle flow is observed to be highly disturbed due to the asymmetrical position of both the gas and the Y-shaped solids inlet line. A jet-like particle flow and a by-passing streaming gas jet around the particles are formed. Just below the solids inlet line a downward oriented particle velocity is measured. Particles are immediately lifted by the ascending gas and spread over the entire cross-sectional tube area. Near the solids inlet line the axial and radial particle velocity fluctuations are of the same order of magnitude as the corresponding mean particle velocity components, showing that the flow is anisotropic. The radial particle velocity fluctuations decrease fast as the radial inflow of particles is transformed into axial particles flow. The turbulence intensity in the inlet section of the dilute riser flow is found to be extremely high, indicating that the flow is far from being fully developed. The total particle shear stress profiles near the solids inlet line indicate a high momentum transfer from radial to axial particle transport. The particle fluctuation energy values calculated based on experimental data are nearly double than the values corresponding in fully developed flow studied previously.

Investigation of flow structure around a horizontal cylinder at different elevations in shallow water

Flow characteristics around a horizontal circular cylinder were investigated in shallow water. The diameter of circular cylinder, the height of shallow water and free stream velocity were kept constant during the experiments as D=30mm, hw=60mm and U=167mm/s, respectively. Particle Image Velocimetry (PIV) was used to measure instantaneous and time-averaged velocity vector fields in the near wake region. In order to investigate the effect of immersion, the cylinder was placed at eight different elevations (hD) between bottom and free surface (from 7.5 to 60mm with 7.5mm increments). Instantaneous and time-averaged velocity vector field, corresponding streamline patterns and Reynolds stress correlation were used to analyze the behavior of the flow downstream of horizontal cylinder. The mean velocity vector field, corresponding streamline topology and Reynolds stress correlation were obtained using 500 instantaneous images. As the immersion level ratio (hD/D) increases, the magnitude of jet-like flow velocity goes up ranged from hD/D=0.25–1. Time averaged flow characteristics show that there is a difference between primary and developing circulation bubble depending on direction of rotation. This occurrence causes the entrainment and this stimulates the momentum transfer between the core and wake flow region for hD/D=1 and 2 cases.

Winglet Type Dielectric Barrier Discharge Plasma Actuators: Performance Characterization and Numerical Comparison

Winglet type dielectric barrier discharge plasma actuator (PA) with two exposed electrodes have been investigated experimentally in a quiescent air and numerically modeled. Three arrangements of electrode positions are used: leading edge type (here after L PA), middle edge type (here after M PA), and trailing edge type (here after T PA) to investigate the effect of electrode position on induced flow. When the electrodes are located at the leading edge of the winglet PA, the stream wise flow is effectively enhanced on the covered electrode; on the other hand when the electrodes are located at the trailing edge, the friction loss is minimized for the near-wall high shear flow over the winglet and thus the highest momentum integral is obtained for the downstream jet-like flow. As all three type of PAs have two exposed electrodes, hence two separate jet flows are induced which are unified to a single jet after the winglet trailing edge. The electrode location also influences the unification velocity at downstream. The longer distance between trailing edge and embedded electrode reduces the downstream unified velocity. Particle image velocimetry (PIV) technique has been implemented to investigate the flow field. Simulation results are found to be consistent and in good agreement with experimental data.

Hemodynamic study of overlapping bare-metal stents intervention to aortic aneurysm

To investigate the hemodynamic performance of overlapping bare-metal stents intervention treatment to thoracic aortic aneurysms (TAA), three simplified TAA models, representing, no stent, with a single stent and 2 overlapped stents deployed in the aneurismal sac, were studied and compared in terms of flow velocity, wall shear stress (WSS) and pressure distributions by means of computational fluid dynamics. The results showed that overlapping stents intervention induced a flow field of slow velocity near the aneurismal wall. Single stent deployment in the sac reduced the jet-like flow formed prior to the proximal neck of the aneurysm, which impinged on the internal wall of the aneurysm. This jet-like flow vanished completely in the overlapping double stents case. Overlapping stents intervention led to an evident decrease in WSS; meanwhile, the pressure acting on the wall of the aneurysm was reduced slightly and presented more uniform distribution. The results therefore indicated that overlapping stents intervention may effectively isolate the thoracic aortic aneurysm, protecting it from rupture. In conclusion, overlapping bare-metal stents may serve a purpose similar to that of the multilayer aneurysm repair system (MARS) manufactured by Cardiatis SA (Isnes, Belgium).

Volumetric intake flow measurements of an IC engine using magnetic resonance velocimetry

Magnetic resonance velocimetry (MRV) measurements are performed in a 1:1 scale model of a single-cylinder optical engine to investigate the volumetric flow within the intake and cylinder geometry during flow induction. The model is a steady flow water analogue of the optical IC-engine with a fixed valve lift of \(9.21\) mm to simulate the induction flow at crank-angle \(270^{\circ }\)bTDC. This setup resembles a steady flow engine test bench configuration. MRV measurements are validated with phase-averaged particle image velocimetry (PIV) measurements performed within the symmetry plane of the optical engine. Differences in experimental operating parameters between MRV and PIV measurements are well addressed. Comparison of MRV and PIV measurements is demonstrated using normalized mean velocity component profiles and showed excellent agreement in the upper portion of the cylinder chamber (i.e., \(y \ge -20\) mm). MRV measurements are further used to analyze the ensemble average volumetric flow within the 3D engine domain. Measurements are used to describe the 3D overflow and underflow behavior as the annular flow enters the cylinder chamber. Flow features such as the annular jet-like flows extending into the cylinder, their influence on large-scale in-cylinder flow motion, as well as flow recirculation zones are identified in 3D space. Inlet flow velocities are analyzed around the entire valve curtain perimeter to quantify percent mass flow rate entering the cylinder. Recirculation zones associated with the underflow are shown to reduce local mass flow rates up to 50 %. Recirculation zones are further analyzed in 3D space within the intake manifold and cylinder chamber. It is suggested that such recirculation zones can have large implications on cylinder charge filling and variations of the in-cylinder flow pattern. MRV is revealed to be an important diagnostic tool used to understand the volumetric induction flow within engine geometries and is potentially suited to evaluate flow changes due to intake geometry modifications.

Convective Flows in Evaporating Sessile Droplets

The evaporation rate and internal convective flows of a sessile droplet with a pinned contact line were formulated and investigated numerically. We developed and analyzed a unified numerical model that includes the effects of temperature, droplet volume, and contact angle on evaporation rate and internal flows. The temperature gradient on the air/liquid interface causes an internal flow due to Marangoni stress, which provides good convective mixing within the droplet, depending upon Marangoni number. As the droplet volume decreases, the thermal gradient becomes smaller and the Marangoni flow becomes negligible. Simultaneously, as the droplet height decreases, evaporation-induced flow creates a large jet-like flow radially toward the contact line. For a droplet containing suspended particles, this jet-like convective flow carries particles toward the contact line and deposits them on the surface, forming the so-called "coffee ring stain". In addition, we reported a simple polynomial correlation for dimensionless evaporation time as a function of initial contact angle of the pinned sessile droplet which agrees well with the previous experimental and numerical results.

Mass transport in internal coastal Kelvin waves

We investigate theoretically the mass transport in internal coastal Kelvin waves by integrating the horizontal momentum equations in the vertical. Applying a perturbation method, the time-averaged Lagrangian horizontal fluxes are determined to second order in wave steepness. The linear wave field is expanded in the vertical using orthogonal functions. Due to the orthogonality property of these functions, formulae for the non-linear Stokes drift and the mean vertically-averaged Eulerian transport driven by the radiation stress can be derived for arbitrary vertical variation of the Brunt–Väisälä frequency N. For values of N typical of the thermocline in the Caspian Sea, the calculation of the non-linear transports yields a jet-like mean flow along the coast, limited in the off-shore direction by the internal Rossby radius. It is suggested that this wave-induced mean drift may contribute to the mean circulation in the Caspian Sea.

Linear stability of the Moore-Saffman model for a trailing wingtip vortex

This paper presents an investigation of the stability of a trailing vortex using mean flow profiles given by an approximate solution of the Navier-Stokes equations. The axial and tangential velocity profiles obtained from this solution, deduced by Moore and Saffman [“Axial flow in laminar trailing vortices,” Proc. R. Soc. London, Ser. A 333, 491–508 (1973)], agree well with experiments involving wings at slight angles of attack. In particular, the Moore-Saffman profiles better describe the jet-like and wake-like axial flows near the center of the vortex than does the much-studied Batchelor vortex. We determine solutions numerically for these profiles and find that they are well suited to describe the flow at short and intermediate distances behind the wingtip. Growth rates for unstable perturbations are presented for different values of n, the wingtip loading parameter. These growth rates are shown to be somewhat larger than those obtained for the Batchelor vortex, and instability persists for larger values of the swirl. The largest amplification rates were found to occur near n = 0.5, the value corresponding to elliptic loading. This is within the range 0.44 < n < 1.0, where the core axial flow is wake-like. For n < 0.44, the flow in the vortex core is jet-like and the growth rates of unstable perturbations become progressively smaller, with all modes damped for n ≈ 0.25.

CFD study of effect of inclination angle on transport and reaction in hollow cylinder catalysts

This work examines how the angle to the flow of a 1-hole catalyst particle impacts its catalytic performance. Computational fluid dynamics (CFD) simulations are reported for flow past a single equilateral hollow cylinder under methane steam reforming conditions, for 1000≤Re≤10,000, and for approach angles from 0° to 90°. The simulations show that at 0°, the flat end of the particle causes separation and formation of a large wake region, while a jet-like flow results through the center hole. These flows result in a pattern of vortices behind the particle, with reverse flow along the particle length. These features are distorted as the approach angle increases, with boundary-layer formation on the upstream side of the particle and a complex vortex pattern on the downstream side. The flow through the particle hole decreases with incidence angle. Surface heat and mass fluxes decrease for the flat ends and the inside curved surface, and increase on the outside curved surface. Both reactant consumption and energy uptake show maxima as a result of the changes in transfer rates through the various particle surfaces, caused by the incident flow.

Numerical Analysis of Flow in a Transonic Compressor With a Single Circumferential Casing Groove: Influence of Groove Location and Depth on Flow Instability

The effect of circumferential single grooved casing treatment on the stability enhancement of NASA Rotor 37 has been examined with computational fluid dynamics analysis. Stall inception mechanism of Rotor 37 is presented first with principal focus on the tip leakage flow behavior, passage blockage, and the vortical flow structures. Detailed observation showed that the combined interaction of the stagnated flow of tip leakage vortex breakdown and the jetlike leakage flow from the midchord region leads to the blade tip-initiated stall inception. The result of numerical parametric study is then demonstrated to show the effect of varying the axial location and the depth of a circumferential single groove. The evaluation based on stall margin improvement showed a higher potential of deeper grooves in stability enhancement, and the optimal position for the groove to be located was indicated to exist near the leading edge of the blade.

Three-dimensional flow features in a nominally two-dimensional rectangular cavity

The object of the present paper was to look at the three-dimensional features of a flow in a nominally two-dimensional rectangular cavity having the length-to-depth ratio equal to 3, with laminar incoming boundary layer. The motivation was to give a contribution to the understanding of the origin of the spanwise flow structures observed in cavity flows. Particle image velocimetry was used to highlight the flow structure at low Reynolds number in the plane parallel to the cavity external flow and normal to the cavity bottom (vertical plane) and in planes parallel to cavity bottom (horizontal planes). The results demonstrate that the present measurements are qualitatively and quantitatively in agreement with published studies having as object the observation of the cavity flow behavior in the vertical plane, assuming the cavity to be nominally two-dimensional. Results in the planes parallel to the cavity bottom show the three-dimensional nature of the flow, characterized by the discontinuous presence of jet-like flows directed towards the cavity leading edge and towards the cavity trailing edge. The origin and nature of these discontinuous “jets” are examined and discussed in the paper. The flow structures are characterized by a wavelength scaling with the cavity length in proximity of the leading edge and with the cavity depth in the region of the trailing edge. Isolated three-dimensional flow structures consisting of side by side counter-rotating vortices have been also observed in the horizontal planes and tentatively interpreted as secondary flows induced by the instability of the main recirculation bubble.

Phased cell division, specific division rates and other biological observations of Dinophysis populations in sub-surface layers off the south coast of Ireland

The proportions of viable cells of Dinophysis spp. that were paired (dividing) and recently divided during a cell cycle were measured on populations of D. acuta and D. acuminata observed off the south coast of Ireland in July 2007 and July 2009. Both species exhibited phased cell division in 2009 with maximum frequency of division (fmax) 2h after sunrise. Different patterns of division (timing of fmax) were shown by D. acuta in 2007, when the population aggregated in a thin layer was transported by a coastal jet flow. High resolution (decimetre-scale) profiles within the thin layer showed large differences in the vertical distribution of biological properties (feeding status, mortality). Values of the specific growth rate µ were compared to estimates derived in similar fashion from observations on Dinophysis populations elsewhere. Different patterns exhibited by the same species in different regions may be attributed to adaptations to latitudinal differences (length of photoperiod). The question of whether phased cell division always occurs in Dinophysis populations, and the incorporation of the potential specific division rate into models of Dinophysis growth are discussed. Comprehensive field data sets demonstrate the impact of the results on the coherence of Dinophysis populations during their transport along the Irish coast in jet-like flows towards sites of intensive shellfish culture.

Heat transfer near an isolated hemispherical gas bubble: The combined influence of thermocapillarity and buoyancy

Thermal Marangoni convection about a 1mm radius hemispherical air bubble attached to a heated wall immersed in a silicone oil layer of constant depth of 5mm was numerically investigated. Tests were performed for a range of Marangoni numbers (145⩽Ma⩽915) with varying levels of gravitational acceleration between zero gravity and earth gravity in order to quantify the rates of heat transfer. For the zero gravity condition, a thermocapillary-driven vortex develops around the bubble extending the entire height of the channel. This flow structure causes a jet-like flow of heated liquid to emanate from the bubble tip which impinged on the cold wall. With the addition of gravity, a counter rotating secondary buoyancy-driven vortex forms which reduces the size of the thermocapillary vortex and disrupts the jet flow from the bubble tip. The wall heat flux profiles indicate that under zero gravity, the peak heat fluxes increase monotonically with Ma with an area of influence that increases asymptotically with Ma. Likewise, under gravity conditions the peak heat flux also increases with Ma and for low Ma is higher than that of 0-g. However, the area of influence is considerably smaller and not sensitive to Ma or the level of gravity. Experimental validation of selected terrestrial gravity numerical results was obtained using particle image velocimetry (PIV) for low to moderate Marangoni numbers. For all experiments, steady-state Marangoni convection was observed. The experimental flow patterns showed good agreement with the numerical solutions.

Experimental and computational study of the flow induced by a plasma actuator

A complementary experimental and computational study of the flow field evoked by a plasma actuator mounted on a flat plate was in focus of the present work. The main objective of the experimental investigation was the determination of the vector force imparted by the plasma actuator to the fluid flow. The force distribution was presently extracted from the Navier–Stokes equations directly by feeding them with the velocity field measured by a PIV technique. Assuming a steady-in-mean, two-dimensional flow with zero-pressure gradient, the imbalance between the convective term and the momentum equation’s right-hand-side terms reveals the desired resulting force. This force-distribution database was used afterwards as the source term in the momentum equation. Furthermore, an empirical model formulation for the volume-force determination parameterized by the underlying PIV-based model is derived. The model is tested within the RANS framework in order to predict a wall jet-like flow induced by a plasma actuator. The Reynolds equations are closed by a near-wall second-moment closure model based on the homogeneous dissipation rate of the kinetic energy of turbulence. The computationally obtained velocity field is analysed along with the experimental data focussing on the wall jet flow region in proximity of the plasma actuator. For comparison purposes, different existing phenomenological models were applied to evaluate the new model’s accuracy. The comparative analysis of all applied models demonstrates the strength of the new empirical model, particularly within the plasma domain. In addition, the presently formulated empirical model was applied to the flow in a three-dimensional diffuser whose inflow was modulated by a pair of streamwise vortices generated by the present plasma actuator. The direct comparison with existing experimental data of Grundmann et al. (2011) demonstrated that the specific decrease of the diffuser pressure corresponding to the continuous forcing was predicted correctly.