Local Suction Research Articles

Ventilation of Aerosol in a Thin-Walled Suction Funnel with Incoming Flow. Part 2. Dynamics of Dust Particles1

A dust and air flow approaching a local ventilation suction funnel is considered. Limiting trajectories of the dust particles are constructed for different Stokes numbers and different rates of the incoming (approach) flow. The effect of the angle of inclination of the suction funnel and its length on the ventilation coefficient is discussed.

Effects of roof height on local pressure and velocity coefficients on building roofs

Failures of roofing systems occur due to high local suctions on tiles or shingles, or because of a different failure mechanism triggered by high local wind velocities near the roof surface. In the latter case, the local velocity can induce positive pressures on the lip of a windward facing shingle or tile, which are transmitted underneath, adding to the external surface negative pressure and causing an increase of the net uplift force. Building codes provide estimates of the peak pressure coefficients (peak Cp) based on 3-s gust in the oncoming wind at the roof height. As an approximation, these coefficients are generally taken to be independent of roof height and exposure. This implies that wind tests of roofing system behaviour carried out at one roof height can be used to infer the system behaviour for other roof heights. One of the main objectives of the present study was to examine the validity of this approximation. Regarding the second failure mechanism discussed above, knowledge of surface wind speed is a key element to assess the uplift forces on shingles. Building codes do not address the wind velocities close to the roof surface and estimate it based on the approach wind speed in terms of a wind speed ratio. So the second objective of the present research was to examine the ratio of local wind velocity close to the roof surface to the velocity at roof height in the approach flow and investigate the effect of height on the velocity ratios. Wind tunnel tests were performed on four different gable-hip roof buildings, at various wind directions. Both surface pressures and near-surface velocities were measured and normalized with respect to upwind flow conditions at mean roof height. The results confirm that the velocity ratios and peak Cp values on the gable roof do not vary markedly with building height with no more than 10% change found at most locations. For the velocity ratios a similar conclusion was reached on the hip roof. However, for the Cp values in the corner zones of the hip roofs increases with height were identified and further investigation is recommended.

Localised estimation and control of linear instabilities in two-dimensional wall-bounded shear flows

A new framework is presented for estimation and control of instabilities in wall-bounded shear flows described by the linearised Navier–Stokes equations. The control design considers the use of localised actuators/sensors to account for convective instabilities in an ${\mathcal{H}}_{2}$ optimal control framework. External sources of disturbances are assumed to enter the control domain through the inflow. A new inflow disturbance model is proposed for external excitation of the perturbation modes that contribute to transition. This model allows efficient estimation of the flow perturbations within the localised control region of a conceptually unbounded domain. The state-space discretisation of the infinite-dimensional system is explicitly obtained, which allows application of linear control theoretic tools. A reduced-order model is subsequently derived using exact balanced truncation that captures the input/output behaviour and the dominant perturbation dynamics. This model is used to design an ${\mathcal{H}}_{2}$ optimal controller to suppress the instability growth. The two-dimensional non-periodic channel flow is considered as an application case. Disturbances are generated upstream of the control domain and the resulting flow perturbations are estimated/controlled using point wall shear measurements and localised unsteady blowing and suction at the wall. The controller is able to cancel the perturbations and is robust to both unmodelled disturbances and sensor inaccuracies. For single-frequency and multiple-frequency disturbances with low sensor noise a nearly full cancellation is achieved. For stochastic forced disturbances and high sensor noise an energy reduction in perturbation wall shear stress of 96 % is shown.

A local scattering approach for the effects of abrupt changes on boundary-layer instability and transition: a finite-Reynolds-number formulation for isolated distortions

We investigate the influence of abrupt changes on boundary-layer instability and transition. Such changes can take different forms including a local porous wall, suction/injection and surface roughness as well as junctions between rigid and porous walls. They may modify the boundary conditions and/or the mean flow, and their effects on transition have usually been assessed by performing stability analysis for the modified base flow and/or boundary conditions. However, such a conventional local linear stability theory (LST) becomes invalid if the change occurs over a relatively short scale comparable with, or even shorter than, the characteristic wavelength of the instability. In this case, the influence on transition is through scattering with the abrupt change acting as a local scatter, that is, an instability mode propagating through the region of abrupt change is scattered by the strong streamwise inhomogeneity to acquire a different amplitude. A local scattering approach (LSA) should be formulated instead, in which a transmission coefficient, defined as the ratio of the amplitude of the instability wave after the scatter to that before, is introduced to characterize the effect on instability and transition. In the present study, we present a finite-Reynolds-number formulation of LSA for isolated changes including a rigid plate interspersed by a local porous panel and a wall suction through a narrow slot. When the weak non-parallelism of the unperturbed base flow is ignored, the local scattering problem can be cast as an eigenvalue problem, in which the transmission coefficient appears as the eigenvalue. We also improved the method to take into account the non-parallelism of the unperturbed base flow, where it is found that the weak non-parallelism has a rather minor effect. The general formulation is specialized to two-dimensional Tollmien–Schlichting (T–S) waves. The resulting eigenvalue problem is solved, and full direct numerical simulations (DNS) are performed to verify some of the predictions by LSA. A parametric study indicates that conventional LST is valid only when the change is sufficiently gradual, and becomes either inaccurate or invalid when the scale of the local distortion is short. A local porous panel enhances T–S waves, while a local suction with a moderate mass flux significantly inhibits T–S waves. In the latter case, a comprehensive comparison is made between the theoretical predictions and experimental data, and a satisfactory quantitative agreement was observed.

Cholinergic Nociceptive Mechanisms in Rat Meninges and Trigeminal Ganglia: Potential Implications for Migraine Pain.

Parasympathetic innervation of meninges and ability of carbachol, acetylcholine (ACh) receptor (AChR) agonist, to induce headaches suggests contribution of cholinergic mechanisms to primary headaches. However, neurochemical mechanisms of cholinergic regulation of peripheral nociception in meninges, origin place for headache, are almost unknown. Using electrophysiology, calcium imaging, immunohistochemistry, and staining of meningeal mast cells, we studied effects of cholinergic agents on peripheral nociception in rat hemiskulls and isolated trigeminal neurons. Both ACh and carbachol significantly increased nociceptive firing in peripheral terminals of meningeal trigeminal nerves recorded by local suction electrode. Strong nociceptive firing was also induced by nicotine, implying essential role of nicotinic AChRs in control of excitability of trigeminal nerve endings. Nociceptive firing induced by carbachol was reduced by muscarinic antagonist atropine, whereas the action of nicotine was prevented by the nicotinic blocker d-tubocurarine but was insensitive to the TRPA1 antagonist HC-300033. Carbachol but not nicotine induced massive degranulation of meningeal mast cells known to release multiple pro-nociceptive mediators. Enzymes terminating ACh action, acetylcholinesterase (AChE) and butyrylcholinesterase, were revealed in perivascular meningeal nerves. The inhibitor of AChE neostigmine did not change the firing per se but induced nociceptive activity, sensitive to d-tubocurarine, after pretreatment of meninges with the migraine mediator CGRP. This observation suggested the pro-nociceptive action of endogenous ACh in meninges. Both nicotine and carbachol induced intracellular Ca2+ transients in trigeminal neurons partially overlapping with expression of capsaicin-sensitive TRPV1 receptors. Trigeminal nerve terminals in meninges, as well as dural mast cells and trigeminal ganglion neurons express a repertoire of pro-nociceptive nicotinic and muscarinic AChRs, which could be activated by the ACh released from parasympathetic nerves. These receptors represent a potential target for novel therapeutic interventions in trigeminal pain and probably in migraine.

Rainfall-triggered slope instabilities under a changing climate: comparative study using historical and projected precipitation extremes

This study aims to quantitatively assess the impact of extreme precipitation events under current and future climate scenarios on landslides. Rainfall-triggered landslides are analyzed primarily using extreme precipitation estimates, derived using the so-called stationary assumption (i.e., statistics of extreme events will not vary significantly over a long period of time). However, extreme precipitation patterns have shown to vary substantially due to climate change, leading to unprecedented changes in the statistics of extremes. In this study, a nonstationary approach, applied to climate model simulations, is adopted to project the upper bound of future precipitation extremes. Future precipitation estimates are obtained from the coupled model intercomparison project phase 5 (CMIP5) simulations. Baseline (historical) and projected (future) precipitation extremes are obtained for a study area near Seattle, Washington. The precipitation patterns are integrated into a series of fully coupled two-dimensional stress – unsaturated flow finite element simulations. The responses of the baseline and projected models at a 7 day rainfall duration obtained for a 50 year recurrence interval are compared in terms of the local strength reduction factor, displacements, matric suctions, and suction stresses. The results indicate that the usage of historical rainfall data can lead to underestimations in the hydromechanical behavior of natural slopes where locally increased transient seepage rates occur from the upper bound of future extreme precipitation estimates.

Thermal Radiation Effect on the MHD Turbulent Compressible Boundary Layer Flow with Adverse Pressure Gradient, Heat Transfer and Local Suction

The combined effect of magnetic field, thermal radiation and local suction on the steady turbulent compressible boundary layer flow with adverse pressure gradient is numerically studied. The magnetic field is constant and applied transversely to the direction of the flow. The fluid is subjected to a localized suction and is considered as a radiative optically thin gray fluid. The Reynolds Averaged Boundary Layer (RABL) equations with appropriate boundary conditions are transformed using the compressible Falkner Skan transformation. The nonlinear and coupled system of partial differential equations (PDEs) is solved using the Keller box method. For the eddy-kinematic viscosity the Baldwin Lomax turbulent model and for the turbulent Prandtl number the extended Kays Crawford model are used. The numerical results show that the flow field can be controlled by the combined effect of the applied magnetic field, thermal radiation, and localized suction, moving the separation point, xs , downstream towards the plate’s end, and increasing total drag, D . The combined effect of thermal radiation and magnetic field has a cooling effect on the fluid at the wall vicinity. The combined effect has a greater influence in the case of high free-stream temperature.

Influence of coupled boundary layer suction and bowed blade on flow field and performance of a diffusion cascade

Based on the investigation of mid-span local boundary layer suction and positive bowed cascade, a coupled local tailored boundary layer suction and positive bowed blade method is developed to improve the performance of a highly loaded diffusion cascade with less suction slot. The effectiveness of the coupled method under different inlet boundary layers is also investigated.Results show that mid-span local boundary layer suction can effectively remove trailing edge separation, but deteriorate the flow fields near the endwall. The positive bowed cascade is beneficial for reducing open corner separation, but is detrimental to mid-span flow fields. The coupled method can further improve the performance and flow field of the cascade. The mid-span trailing edge separation and open corner separation are eliminated. Compared with linear cascade with suction, the coupled method reduces overall loss of the cascade by 31.4% at most. The mid-span loss of the cascade decreases as the suction coefficient increases, but increases as bow angle increases. The endwall loss increases as the suction coefficient increases. By contrast, the endwall loss decreases significantly as the bow angle increases. The endwall loss of coupled controlled cascade is higher than that of bowed cascade with the same bow angle because of the spanwise inverse “C” shaped static pressure distribution. Under different inlet boundary layer conditions, the coupled method can also improve the cascade effectively.

Radiation effect on the turbulent compressible boundary layer flow with adverse pressure gradient

The effects of thermal radiation and localized suction on the steady turbulent compressible boundary layer flow with adverse pressure gradient are numerically studied. The compressible flow is subjected to a constant localized suction velocity and the fluid is considered as a radiative optically thin gray fluid. The plate is adiabatic and the flow is subjected to adverse pressure gradient.The Reynolds Averaged Boundary Layer (RABL) equations with appropriate boundary conditions are transformed using the compressible Falkner Skan transformation. The resulting nonlinear, coupled system of partial differential equations (PDEs) is solved using the Keller box method. For the eddy kinematic viscosity, the turbulent models of Cebeci Smith and Baldwin Lomax are employed. For the turbulent Prandtl number, the extended Kays Crawford model is used. The obtained results are validated with previously published computational results and with experimentally based correlations, showing a good agreement.The results show that the flow is influenced by the combined effect of radiation and localized suction. The coupled effect moves the separation point downstream, towards the plate’s end, and increases total drag. Radiation alters the thermal boundary layer above the plate by cooling the fluid at plate’s vicinity and by slightly increasing the boundary layer maximum temperature.

Design and Analysis of Airfoil-Shaped Impeller Blades of Centrifugal Pump

This paper deals with a comparative study of the outlet pressure-energy between a conventional and normal blade impeller and an airfoil-shaped blade impeller of a centrifugal pump. Although the volute casing is an important component along with an impeller [1], the present comparative analysis makes the volute casing redundant to the study, hence neglected. All centrifugal pumps are usually designed and manufactured using backward swept blades with equal camber on the top and bottom sides. An increased camber on the top side is an ideal trait for a lift generating airfoil. The purpose is to implement the principle of lift generation of airfoil for centrifugal pumps. As a result, a local suction side and pressure side can be visualized using CFX-post processor. The 3D analysis of such a centrifugal pump impeller is designed in SOLIDWORKS® and analyzed using ANSYS® CFX. The SST (Menter’s Shear Stress Transport) model is used as it combines both the k-ω and k-ε turbulence models.

Direct Numerical Simulation of Wave Packets in Hypersonic Compression-Corner Flow

Direct numerical simulations of a three-dimensional wave packet propagating over a 5.5 deg compression corner at the freestream Mach number 5.373 are carried out. The Navier–Stokes equations are integrated using an implicit finite volume shock-capturing method with the second-order approximation in space and time. After computing the laminar flowfield, unsteady disturbances are imposed onto the steady solution via local suction blowing on the wall surface. The undisturbed boundary layer separates upstream of the corner and reattaches downstream, forming a shallow separation bubble. The suction-blowing pulse generates a three-dimensional wave packet propagating downstream. If the pulse is produced near the leading edge, the wave packet is dominated by oblique waves relevant to the first mode, whereas plane waves of the second mode are relatively small. At sufficiently strong forcing, the nonlinear effects destabilize the wave packet in the separation region and lead to its nonlinear breakdown downstream of the reattachment line. Ultimately, a young turbulent spot is formed in the reattached boundary layer. If the pulse is produced sufficiently far downstream of the leading edge, so that the major portion of the first-mode instability region is not involved, the wave packet is dominated by the second mode. These examples show that the wave-packet contents and its downstream evolution strongly depend on how and where the initial disturbance is excited.

Modeling of Air and Dust Flows in the Range of Action of a Round Suction Funnel Above an Impermeable Plane. Part 2. Characteristics of Separation Region and Efficiency of Capture of Dust Particles1

Current near a round local ventilation suction port in the form of a funnel situated above an impermeable plane is considered. Limiting trajectories of dust particles are constructed in the velocity field found from a new computer program and the capture coefficient as a function of the slope and length of the funnel and distance from the plane is determined. The geometric dimensions of the separation region at the inlet to the funnel as functions of the distance from the plane and the length of the funnel are determined.

A local scattering theory for the effects of isolated roughness on boundary-layer instability and transition: transmission coefficient as an eigenvalue

This paper is concerned with the rather broad issue of the impact of abrupt changes (such as isolated roughness, gaps and local suctions) on boundary-layer transition. To fix the idea, we consider the influence of a two-dimensional localized hump (or indentation) on an oncoming Tollmien–Schlichting (T–S) wave. We show that when the length scale of the former is comparable with the characteristic wavelength of the latter, the key physical mechanism to affect transition is through scattering of T–S waves by the roughness-induced mean-flow distortion. An appropriate mathematical theory, consisting of the boundary-value problem governing the local scattering, is formulated based on triple deck formalism. The transmission coefficient, defined as the ratio of the amplitude of the T–S wave downstream of the roughness to that upstream, serves to characterize the impact on transition. The transmission coefficient appears as the eigenvalue of the discretized boundary-value problem. The latter is solved numerically, and the dependence of the eigenvalue on the height and width of the roughness and the frequency of the T–S wave is investigated. For a roughness element without causing separation, the transmission coefficient is found to be approximately 1.5 for typical frequencies, indicating a moderate but appreciable destabilizing effect. For a roughness causing incipient separation, the transmission coefficient can be as large as $O(10)$, suggesting that immediate transition may take place at the roughness site. A roughness element with a fixed height produces the strongest impact when its width is comparable with the T–S wavelength, in which case the traditional linear stability theory is invalid. The latter however holds approximately when the roughness width is sufficiently large. By studying the two hump case, a criterion when two roughness elements can be regarded as being isolated is suggested. The transmission coefficient can be converted to an equivalent $N$-factor increment, by making use of which the $\text{e}^{N}$-method can be extended to predict transition in the presence of multiple roughness elements.

Cutting and Welding of High-Strength Steels Using Non-Vacuum Electron Beam as a Universal Tool for Material Processing

Using a non-vacuum electron beam, a two-step process chain for plate materials is a feasible possibility. Cutting and welding can be performed in subsequent steps on the same machine for a highly productive process chain. The electron beam is a tool with high energy conversion efficiency, which is largely independent of the type of metal. Its high power density qualifies the non-vacuum electron beam as an outstanding energy source for the well-known NVEB welding as well as for high-speed cutting. Welding is possible with or without filler wire or shielding gas, depending on the application. The NVEB-cutting process employs a co-moving cutting head with a sliding seal for extremely high cutting speeds producing high quality edges. Due to direct removal of fumes and dust, NVEBC with local suction is an exceptionally clean and fast process. The NVEB welding process is possible directly after cutting, without further edge preparation. The potential directions of development of non-vacuum electron beam technologies are discussed. An exemplary two-step process chain using high-strength steel is presented to highlight possible application in industries such as general steel construction, automotive, shipbuilding, railway vehicle or crane construction. An analysis of the mechanical properties of the resulting weld seam is presented.

Liquid Velocity and Local Fouling in Coagulation-submerged Microfiltration Module for Drinking Water Treatment

Effects of aeration intensity on local fouling were investigated in submerged membrane modules. Higher liquid velocities were observed at the section with the lower fiber packing density. The liquid velocity is increased with increasing the gas-liquid injection factor. The high shear stress coincided with the high liquid velocity. The shear stress increases with the increasing of gas-liquid injection factor and the liquid velocity improves with the increasing of gas-liquid injection factor. Irreversible fouling resistance (Rir) of the fiber position is significant in a local region of high suction pressure near the suction point of the fiber (position 1). The ratio of Rir/Rm and Rir/Rr of position 1 was highest compared to the position 2 and 3. Irreversible fouling resistances results confirmed the preferential deposition of foulants near the suction part of the fiber where the local suction pressure is the highest and correspondingly, more particles are accumulated to the membrane surface. The effects of local fouling along the fiber length are significant factors to optimize the design of submerged modules.

BOUNDARY LAYER FLOW AND HEAT TRANSFER OF A DUSTY FLUID OVER A VERTICAL PERMEABLE STRETCHING SURFACE

The steady boundary layer free convective flow of a dusty fluid past a vertical permeable stretching surface is studied .The governing equations are converted into first order ordinary differential equations using similarity transformations. These equations are solved numerically by using Runge kutta forth order method. The effects of physical parameters like fluid-particle interaction parameter, local Grashof number, suction parameters, Prandtl number, radiation parameter and Eckert number on the flow and heat transfer characteristics are computed and presented graphically. Also the rate of heat transfer at the surface is discussed. The present results are compared with the previous study and there is a good agreement. AMS classification 76T10, 76T15

Numerical study on boundary-layer receptivity with localized wall blowing/suction

Most of previous studies focused on the boundary-layer receptivity to the convected disturbances in the free stream interacting with localized wall roughness. Whereas the research on the boundary-layer receptivity induced by localized blowing or localized suction is relatively few. In this paper, we investigate two-dimensional boundary-layer receptivity induced by localized blowing/suction within free-stream turbulence through using direct numerical simulation and fast Fourier transformation. High-order compact finite difference schemes in the y-direction, fast Fourier transformation in the x-direction, and a Runge-Kutta scheme in time domain are used to solve the Navier-Stokes equations. The numerical results show that Tollmien-Schlichting (T-S) wave packets are excited by the free-stream turbulence interacting with localized blowing in the two-dimensional boundary layer, which are superposed by a group of stable, neutral and unstable T-S waves. The dispersion relations, growth rates, amplitude distributions and phase distributions of the excited waves accord well with theoretical solutions of the linear stability theory, thus confirming the existence of the boundary-layer receptivity. And the frequencies of the instability waves are between the upper and lower branches of the neutral stability curves. According to the evolutions of the wave packets, the positions of peaks and valleys are tracked over time to calculate the propagation speed by taking the average. The propagation speeds of the wave packets are approximately one-third of the free-stream velocity, which are in accordance with Dietz's measurements. The propagation speeds of wave packets are also close to the phase speeds of the most unstable waves for the numerical results. The relations of the receptivity response to the forcing amplitude, the blowing intensity, and the blowing width are found to be linear, when the forcing amplitude and the blowing intensity are less than 1% free-steam velocity amplitude and 0.01, respectively. And the maximum amplitudes of the T-S waves can be excited while the blowing length is equal to the resonant wavelength /(TS-FS), where TS is the wave-number of the T-S wave, and FS is the wave-number of the forcing disturbance. These results are similar to those given by Dietz [Dietz A J 1999 J. Fluid Mech. 378 291]. Additionally, T-S waves with the same dispersion relations but opposite phases are generated by localized blowing and localized suction respectively, and the amplitudes of the T-S waves excited by localized blowing are nearly 15% greater than those by localized suction under the same condition. According to this theory, an optimal design of localized suction device is able to enhance or delay the laminar-turbulent transition for turbulent control.

Variable Viscosity and Thermal Conductivity on Convective Heat Transfer in a Dusty Fluid over a Vertical Permeable Surface with Radiation and Viscous Dissipation

effects variable viscosity and thermal conductivity on a steady free convective boundary layer flow of a dusty fluid past a vertical permeable stretching surface with viscous dissipation and thermal radiation is studied. The system of partial differential equations together with the prescribed boundary conditions governing the equations of motion are reduced to a system of ordinary differential equations using similarity transformations. The resultant boundary value problems are then solved numerically using shooting technique based on fourth order Runge-Kutta method. The effects of physical parameters viz., viscosity parameter, thermal conductivity parameter, fluid-particle interaction parameter, local Grashof number, suction parameter, Prandtl number, radiation parameter and Eckert number on the flow and heat transfer are computed and presented graphically. The temperature gradient which gives the rate of heat transfer at the surface and skin friction coefficient are also obtained and present in Tables. The effects of all the parameters are quite significant. Keywordsviscosity and thermal conductivity, Dusty fluid; fluid-particle interaction parameter; radiation parameter; viscous dissipation

Water Retention Characteristics and State-Dependent Mechanical and Petro-Physical Properties of a Clay Shale

A series of clay shale specimens in equilibrium with various humidity conditions were used to establish the water retention characteristics, the influence of suction on ultrasonic p-wave velocity and rock mechanical properties such as Young’s modulus, Poisson’s ratio, onset of dilatancy, unconfined compressive strength and Brazilian tensile strength. Opalinus Clay, a clay shale considered as host rock for the disposal of nuclear waste in Switzerland was utilized. The results showed that the p-wave velocity normal to bedding (vp,n) dropped sharply upon desaturation until suction approached the air-entry value. The sharp decrease was associated with desiccation cracks solely oriented parallel to bedding. For suction in excess of the air-entry value, vp,n was constant, indicating no further desiccation damage. The suction at the shrinkage limit and at the air-entry point is similar in magnitude. The p-wave velocity parallel to bedding (vp,p) remained constant in the entire range of suction investigated in this study. The constant vp,p with increasing suction might be associated with the disproportional decrease in the Poisson’s ratio and Young’s modulus and its opposing effect on p-wave velocity. An almost linear increase in unconfined compressive strength, Brazilian tensile strength, stress at the onset of dilatancy and Young’s modulus with increasing suction was observed up to a suction of 56.6 MPa. For suction larger than 56.6 MPa, relatively constant strength and stiffness was observed. The increase is associated with the net contribution of suction to strength/stiffness, which decreases nonlinearly with decreasing volumetric water content. The rate of increase in tensile strength and unconfined compressive strength with increasing suction is different depending on the rock anisotropy. Compared to the strength values (Brazilian tensile and uniaxial compressive strength) obtained from specimens loaded parallel to bedding, the tensile strength parallel to bedding and the unconfined compressive strength obtained from specimens loaded normal to bedding are considerably more affected by increasing suction or decreasing water content. The reasons for the different rates in strength increase are considered to be related to local variations in suction (i.e., local suction) as a consequence of zones of contrasting pore-size distribution. These variations may influence the effect of suction on strength, especially when the load is applied parallel to bedding and crack growth occurs predominately along bedding layers with comparably low suction.

Mechanical Thrombectomy in Basilar Artery Thrombosis: Technical Advances and Safety in a 10-Year Experience

Multiple endovascular devices have been used for mechanical thrombectomy (MT) in basilar artery occlusion (BAO) for >10 years. Based on a single-center experience during the course of one decade, we present data on safety and efficacy of previous MT devices compared with modern stent retriever and suction thrombectomy. Eighty-one patients (29 women, 52 men, mean age 61.5 years, range 17-90) with angiographically confirmed BAO that had been treated by MT between 2001 and 2011 were retrospectively evaluated. Patients in group 1 (n = 60) had been treated between 2001 and 2008 with different devices available at that time. Patients in group 2 (n = 21) had been treated by modern stent retriever or local suction devices between 2008 and 2011. Recanalization rate, needle to recanalization time, procedure-related complications, and distal embolization of thrombotic material were recorded and compared. Recanalization rates of 95% were high in both groups. Procedure-related dissection (n = 5) and subarachnoid hemorrhage (n = 9) occurred in group 1 but not in group 2 (p < 0.016). Needle-to-recanalization time was less than half in group 2 compared with group 1 (54.6 vs. 132.3 min, p < 0.01). Frequency of distal embolization was comparable in both groups (47%). High recanalization rates have been achieved since the introduction of MT in BAO. However, modern stent retriever and suction devices allow for safer and more rapid recanalization compared with previous MT devices.