Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Vortex shedding control using a permeable plate located around the separation point of a circular cylinder

American Society of Mechanical Engineers (ASME)ASME 2015 International Mechanical Engineering Congress and Exposition, IMECE 2015 --13 November 2015 through 19 November 2015 -- --The flow downstream of a plain cylinder with attached permeable plates having various porosity ratios was investigated experimentally using both Particle Image Velocimetry (PIV) and dye visualization techniques to control the vortex shedding around the circular cylinder. The diameter of the cylinder and length to diameter ratio of the plate were kept constant as d= 50 mm and L/d=1.0, respectively. The porosity ratio, ß which can be defined as the ratio of open area to the whole body surface area was taken as ß=0.4, 0.5, 0.6, 0.7 and 0.8 (permeable plates). The study was performed considering deep water flow conditions and depth-averaged free stream velocity was taken constant as U = 95.2mm/s which corresponded to a Reynolds number of Red = 5000 based on the cylinder diameter. The results of a plain cylinder were compared with the results of cylinder with permeable plates in order to understand the control effect. Both qualitative and quantitative results revealed that the plates are effective on the unsteady flow structure downstream of the cylinder, i.e. the vortex formation length was increased, turbulent statistics was reduced and both width and length of the wake were changed by usage of permeable plates attached around the separation point of the cylinder. Copyright © 2015 by ASME

Flow past a hollow cylinder with two spanwise rows of holes

Abstract: The flow over fixed, hollow, rigid circular cylinders with and without two series of equally spaced holes of equal diameter (0.2 cylinder diameter) along the surface of the cylinder has been studied by means of dye injection flow visualization, particle image velocimetry (PIV), and force measurements. Holes are connecting the front and rear stagnation lines or the upper and lower sides (i.e., they are positioned at ± 90° from the stagnation line) of the cylinder. The center-to-center distance between holes was 7-hole diameter. The experimental data were obtained from water channel and wind tunnel measurements performed at Reynolds numbers of 6900 and 20000, respectively. It was found that cylinder with holes located on the surface at an angle ± 90° from the front stagnation line behaves like a double-chamber synthetic jet actuator when subjected to cross-flow. The interaction of synthetic jet arrays with external flow over the side surfaces instigates the three-dimensional instabilities in the near wake and produces a 14.4% drag reduction compared to the drag of a plain cylinder. It was shown that cylinder with holes located on the surface at angles of 0° and 180° from the front stagnation line also instigates the three-dimensional instabilities in the near wake, but the primary mechanism responsible for drag reduction is self-bleed through downstream holes. This system producing drag reduction was found to have a drag coefficient equal to about 78.9% of that for a plain cylinder. Important flow structures inside and behind the cylinders with holes were also identified. Graphic abstract: [Figure not available: see fulltext.]. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature

PIV measurements in the near wakes of hollow cylinders with holes

The wake flows behind fixed, hollow, rigid circular cylinders with two rows of holes connecting the front and rear stagnation lines were investigated using particle image velocimetry (PIV) for various combinations of three hole diameters, d = 0.1D, 0.15D, and 0.20D, six hole-to-hole distances, l = 2d, 3d, 4d, 5d, 6d, and 7d, and ten angles of incidence (?), from 0° to 45° in steps of 5°, at a Reynolds number of Re = 6,900. Time-averaged velocity distributions, instantaneous and time-averaged vorticity patterns, time-averaged streamline topology, and hot spots of turbulent kinetic energy occurred through the interaction of shear layers from the models were presented to show how the wake flow was modified by the presence of the self-issuing jets with various momentums emanating from the downstream holes. In general, as hole diameter which is directly related to jet momentum increased, the values of time-averaged wake characteristics (length of time-averaged recirculation region, vortex formation length, length of shear layers, and gap between the shear layers) increased. Irrespective to d and l tested, the values of the vortex formation length of the models are greater than that of the cylinder without hole (reference model). That is, vortex formation process was shifted downstream by aid of jets. It was found that time-averaged wake characteristics were very sensitive to ?. As ? increased, the variation of these characteristics can be modeled by exponential decay functions. The effect of l on the three-dimensional vortex shedding patterns in the near wake of the models was also discussed. © 2017, Springer-Verlag Berlin Heidelberg

Effect of high porosity screen on the near wake of a circular cylinder

DANTEC DYNAMICS GmbH;KAMAX Holding;LENAM s.r.o.;MIT s.r.o.;SPECION s.r.o.7th International Conference on Experimental Fluid Mechanics 2012, EFM 2012 --20 November 2012 through 23 November 2012 -- Hradec Kralove --The change in flow characteristics downstream of a circular cylinder (inner cylinder) surrounded by a permeable cylinder (outer cylinder) made of a high porosity screen was investigated in shallow water using Particle Image Velocimetry (PIV) technique. The diameter of the inner cylinder, outer cylinder and the water height were kept constant during the experiments as d = 50 mm, D = 100 mm and hw = 50 mm, respectively. The depth-averaged free stream velocity was also kept constant as U = 180 mm/s which corresponded to a Reynolds number of Red = 9000 based on the inner cylinder diameter. It was shown that the outer permeable cylinder had a substantialeffect on the vortex formation and consequent vortex shedding downstream of the circular cylinder, especially in the near wake. The time averaged vorticity layers, streamlines and velocity vector field depict that the location of the interaction of vortices considerably changed by the presence of the outer cylinder. Turbulent statistics clearly demonstrated that in comparison to the natural cylinder, turbulent kinetic energy and Reynolds stresses decreased remarkably downstream of the inner cylinder. Moreover, spectra of streamwise velocity fluctuations showed that the vortex shedding frequency significantly reduced compared to the natural cylinder case. © Owned by the authors, published by EDP Sciences, 2013

Passive flow control in the near wake of a circular cylinder using attached permeable and inclined short plates

The main objective of this study is to assess the effectiveness of attached permeable plates in suppressing nominally two-dimensional vortex shedding from a fixed cylinder. The permeable plate along the entire span of the cylinder was made of a chrome-nickel screen and was attached normal to the cylinder surface. The main parameters of the study are porosity of the permeable plate, ß, and the plate angle of the cylinder-plate arrangement, ?, with respect to the freestream. Experiments were performed using Particle Image Velocimetry (PIV) and Flow Visualization Techniques. Additionally, drag force measurements were carried out in a wind tunnel to analyze the effects of permeable plates on drag coefficient of the circular cylinder. The results revealed that the use of a permeable plate successfully suppresses the vortex shedding downstream of the circular cylinder by reducing the velocity fluctuations in the wake, elongating the vortex formation region further downstream and attenuating the vortex shedding frequency. The porosity values of ß=0.4 and 0.5 with plate angles in the range of 35°???90° were found to be effective on suppressing the vortex shedding. Furthermore, both the drag coefficients of the cylinder-plate arrangement and the <TKE>maxwere reduced almost for all porosity ratios for ?<30°. © 201

PIV studies around a bus model

The three-dimensional flow structures around a bus model have been investigated experimentally. The time-averaged and instantaneous velocity vector maps, vorticity contours, streamline topology and other turbulent quantities were obtained using the particle image velocimetry (PIV) technique. The measurements were carried out in vertical, horizontal and cross-sectional planes. The three-dimensional wake region was asymmetric in the vertical plane while the wake flow was almost symmetric in the horizontal plane. In cross-planes the flow field downstream of the model is dominated by a pair of counter rotating vortices originating from the bottom and upper corners of the model. © 2011 Elsevier Inc.Firat University Scientific Research Projects Management Unit: MMF2006D32The authors would like to acknowledge the financial support of the Office of Scientific Research Projects of Cukurova University for funding under contract No: MMF2006D32

Control of vortex shedding using a screen attached on the separation point of a circular cylinder and its effect on drag

The control of flow in the wake of a circular cylinder by an attached permeable plate having various porosity ratios was analyzed experimentally using both particle image velocimetry (PIV) and dye visualization techniques. The force measurements were also done in order to interpret the effect of control method on drag coefficient. The diameter of the cylinder and length to diameter ratio of the plate were kept constant as D=50mm and L/D=1.0, respectively. The porosity ratio, ß, which can be defined as the ratio of open surface area to the whole body surface area, was taken as ß=0.4, 0.5, 0.6, 0.7, and 0.8 (permeable plates). The study was performed considering deep water flow conditions with a constant Reynolds number of ReD=5000 based on the cylinder diameter. Each permeable plate was attached on the separation point and the results were compared with the results of cylinder without permeable plate (plain cylinder) in order to understand the control effect. Both qualitative and quantitative results revealed that the permeable plates of 0.4 ? ß ? 0.6 are effective on controlling the unsteady flow structure downstream of the cylinder, i.e., the vortex formation length was increased, turbulent statistics was reduced and vortex shedding frequency was diminished when the permeable plate attached normal to the cylinder surface from the lower separation point. However, the drag force acting on the cylinder was found to be increased due to the increased cross-sectional area. © 2017 by ASME

Effect of High Porosity Screen on the Near Wake of a Circular Cylinder

The change in flow characteristics downstream of a circular cylinder (inner cylinder) surrounded by a permeable cylinder (outer cylinder) made of a high porosity screen was investigated in shallow water using Particle Image Velocimetry (PIV) technique. The diameter of the inner cylinder, outer cylinder and the water height were kept constant during the experiments as d = 50 mm, D = 100 mm and hw = 50 mm, respectively. The depth-averaged free stream velocity was also kept constant as U = 180 mm/s which corresponded to a Reynolds number of Red = 9000 based on the inner cylinder diameter. It was shown that the outer permeable cylinder had a substantialeffect on the vortex formation and consequent vortex shedding downstream of the circular cylinder, especially in the near wake. The time averaged vorticity layers, streamlines and velocity vector field depict that the location of the interaction of vortices considerably changed by the presence of the outer cylinder. Turbulent statistics clearly demonstrated that in comparison to the natural cylinder, turbulent kinetic energy and Reynolds stresses decreased remarkably downstream of the inner cylinder. Moreover, spectra of streamwise velocity fluctuations showed that the vortex shedding frequency significantly reduced compared to the natural cylinder case

Flow around a cylinder surrounded by a permeable cylinder in shallow water

The change in flow characteristics downstream of a circular cylinder (inner cylinder) surrounded by an outer permeable cylinder was investigated in shallow water using particle image velocimetry technique. The diameter of the inner cylinder and the water height were kept constant during the experiments as d = 50 mm and h w = 25 mm, respectively. The depth-averaged free-stream velocity was also kept constant as U = 170 mm/s which corresponded to a Reynolds number of Red = 8,500 based on the inner cylinder diameter. In order to examine the effect of diameter and porosity of the outer cylinder on flow characteristics of the inner cylinder, five different outer cylinder diameters (D = 60, 70, 80, 90 and 100 mm) and four different porosities (ß = 0.4, 0.5, 0.6 and 0.7) were used. It was shown that both porosity and outer cylinder diameter had a substantial effect on the flow characteristics downstream of the circular cylinder. Turbulent statistics clearly demonstrated that in comparison with the bare cylinder (natural case), turbulent kinetic energy and Reynolds stresses decreased remarkably when an outer cylinder was placed around the inner cylinder. Thereby, the interaction of shear layers of the inner cylinder has been successfully prevented by the presence of outer cylinder. It was suggested by referring to the results that the outer cylinder having 1.6 ? D/d ? 2.0 and 0.4 ? D/d ? 0.6 should be preferred to have a better flow control in the near wake since the peak magnitude of turbulent kinetic energy was considerably low in comparison with the natural case and it was nearly constant for these mentioned porosities ß, and outer cylinder to inner cylinder diameter ratios D/d. © 2012 Springer-Verlag Berlin Heidelberg