Correction: Reiswich et al. Effect of Flexible Flaps on Lift and Drag of Laminar Profile Flow. Energies 2020, 13, 1077

The authors wish to make the following corrections to their paper [...]

Time-Resolved Measurements of the Unsteady Boundary Layer in an Annular Low-Pressure Turbine Configuration with Perturbed Inlet Submitted for Publication

In this study the unsteady behavior of the boundary layers developing on a LPT stator profile and their effect on secondary flow patterns in a 1.5-stage turbine configuration are investigated under the influence of periodic inflow perturbations. For this the experimental setup has been enhanced by hot-film sensor arrays placed on the stator profiles to provide time-resolved data from within the passage. The inflow is perturbed by periodically passing bars and a modified T106-profile has been considered for the blading. The profile, labeled as T106RUB, was developed for matching the transition and separation characteristics of the original T106 profile at low flow speeds, thus facilitating measurements to be taken in a large-scale test rig with its improved accessibility. The transition phenomena occurring in the profile boundary layers are investigated under both unperturbed and periodically perturbed inflow by means of spectral analysis, the characterization of the wall-stress system and an evaluation of the statistic quantities. In particular, the periodic changes of the suction side boundary layer flow region towards the trailing edge are studied in detail. Furthermore, time-resolved hot-film measurements at different blade height positions facilitate a detailed comparison of the quasi two-dimensional mid-span profile flow and the near end wall profile flow which is subject to influence of secondary flow structures. These information are employed to assess to which extent the additional turbulence originating from the wakes affects the blade boundary layers and thus the secondary flow structures.

Endovascular Treatment of Intracranial Aneurysms in Small Peripheral Vessel Segments—Efficacy and Intermediate Follow-Up Results of Flow Diversion With the Silk Vista Baby Low-Profile Flow Diverter

Background and Purpose: Low-profile flow diverter stents (FDS) quite recently amended peripheral segments as targets for hemodynamic aneurysm treatment; however, reports on outcomes, especially later than 3 months, are scarce. This study therefore reports our experience with the novel silk vista baby (SVB) FDS and respective outcomes after 8 and 11 months with special respect to specific adverse events.Materials and Methods: Forty-four patients (mean age, 53 years) harboring 47 aneurysms treated with the SVB between June 2018 and December 2019 were included in our study. Clinical, procedural, and angiographic data were collected. Follow-ups were performed on average after 3, 8, and 11 months, respectively. Treatment effect was assessed using the O'Kelly Marotta (OKM) grading system.Results: Overall, angiographic follow-ups were available for 41 patients/45 aneurysms. Occlusion or significant reduction in aneurysmal perfusion (OKM: D1, B1–B3 and A2–A3) was observed in 98% of all aneurysms after 8 months. Only 2% of the treated aneurysms remained morphologically unaltered and without an apparent change in perfusion (OKM A1). Adverse events in the early post-interventional course occurred in seven patients; out of them, mRS-relevant morbidity at 90 days related to FDS treatment was observable in two patients. One death occurred in the context of severe SAH related to an acutely ruptured dissecting aneurysm of the vertebral artery.Conclusion: The SVB achieves sufficient occlusion rates of intracranial aneurysms originating from peripheral segments, which are comparable to prior established conventional FDS with acceptably low complication rates. However, alteration of a hemodynamic equilibrium in distal localizations requires special attention to prevent ischemic events.

Mathematical analysis of a non-Newtonian polymer in the forward roll coating process

This article describes the development of a mathematical model of forward roll coating of a thin film of a non-Newtonian material when it passes through a small gap between the two counter-rotating rolls. The conservation equations of mass, momentum, and energy in the light of LAT (lubrication approximation theory) are non-dimensionalized and solutions for the velocity profile, flow rate, pressure distribution, pressure, forces, stresses, power input to the roller, and temperature distribution are calculated analytically. It is found that by changing (increasing/decreasing) the value of material parameters, one can really control the engineering parameters like, stress and the most important the coating thickness and is a quick reference for the engineer working in coating industries. Some results are shown graphically. From the present study, it has been established that the material parameter is a device to control flow rate, coating thickness, separation points, and pressure distribution.

Transcirculation Silk Vista Baby-assisted coiling in half-T configuration for the treatment of posterior communicating artery aneurysms associated with a fetal posterior circulation: An alternative flow diversion strategy

Flow diverter devices have become a routine first-line option for treatment of an increasing population of intracranial aneurysms at many neurovascular centers. Despite the promising results of flow diverter stents on anterior circulation, incomplete occlusion on the presence of fetal posterior circulation has been described on several reports. Here we describe a novel technical alternative to conventional flow diversion approach for this specific subgroup of aneurysms using the low-profile flow diverter, Silk Vista Baby. The device was selectively placed into the fetal type posterior cerebral artery in half-T configuration for the treatment of a posterior communicating aneurysm using a transcirculation approach through the anterior communicating artery. This represents a useful and effective technique and should be considered when encountering the above-described situation.

Time-Resolved Measurements of the Unsteady Boundary Layer in an Annular Low-Pressure Turbine Configuration With Perturbed Inlet

In this study the unsteady behavior of the boundary layers developing on a LPT stator profile and their effect on secondary flow patterns in a 1.5-stage turbine configuration are investigated under the influence of periodic inflow perturbations. The experimental setup previously employed to analyze the unsteady secondary flow in the stator wake has been enhanced by hotfilm sensor arrays placed on the stator profiles at different blade height positions to provide time-resolved data from within the passage. The turbine inflow is perturbed by periodically passing circular bars and a modified T106-profile has been considered for the blading. The modified profile, labeled as T106RUB, was developed for matching the transition and separation characteristics of the original T106 profile at low flow speeds, thus facilitating measurements to be taken in a large-scale test rig with its improved accessibility. The transition phenomena occurring in the profile boundary layers are investigated under both unperturbed and periodically perturbed inflow by means of spectral analysis, the semi-quantitative characterization of the wall-stress system and an evaluation of the statistic quantities. In particular, the periodic changes of the suction side boundary layer flow region towards the trailing edge are studied in detail. Furthermore, time-resolved hot-film measurements at different blade height positions facilitate a detailed comparison of the quasi two-dimensional mid-span profile flow and the near end wall profile flow which is subject to influence of secondary flow structures. These information are employed to assess to which extent the additional turbulence originating from the wakes affects the blade boundary layers and thus the secondary flow structures. Furthermore, the role of the perturbation frequency on the coupled system of boundary layers and secondary flow structures is evaluated.

Periprocedural safety and technical outcomes of the new Silk Vista Baby flow diverter for the treatment of intracranial aneurysms: results from a multicenter experience

PurposeThe aim of our study was to assess the technical success and the safety of this new low-profile flow diverter Silk Vista Baby (SVB) by evaluating the intraprocedural and periprocedural complication rate.Material/methodsClinical, procedural, and angiographic data were analyzed.Results: 41 consecutive patients (28 women; age average 50.5 years) with 43 aneurysms were treated with SVB. Aneurysm sizes were classified by their maximum diameter, with an average size of 9.5 mm (range 2–30 mm). Thirty-four cases were unruptured. five aneurysms previously ruptured, had recurrence after the initial coiling. There were two ruptured cases. Aneurysms' locations were: M1 segment (five cases), M2 segment (three cases), M3 segment (one case), middle cerebral artery (MCA) bifurcation (six cases), carotid-T (two cases), anterior communicating artery/A1/A2 (11 cases), pericallosal artery (four cases), supraclinoid ICA (two cases), PCom (one case), V4 segment (three cases), PCA (three cases), SCA (one case), and PICA (one case). We had five intraprocedural complications which resolved without clinical consequences and three events postprocedural events. Initial occlusion rates were: eight aneurysms (18.6%) were completely occluded, five aneurysms (11.6%) showed near-complete occlusion, four cases (9.3%) showed incomplete filling, and 26 cases (60.4%) showed persisting filling. The mRS score at discharge from the hospital did not change from the admission mRS score.ConclusionOur study demonstrated that the use of the new low-profile flow diverter, SVB device, for the treatment of intracranial aneurysms is feasible and technically safe.