Interaction between the jet and wakes as a method for passive control of plane impinging jets

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.A planar impinging air jet was experimentally investigated, with passive flow control as means of enhancement of impingement heat/mass transfer. The control was achieved by means of an array of small cylinders, fixed at the nozzle lips so as to bridge the nozzle exit gap. Experiments used mainly the naphthalene sublimation technique, with the resultant local mass transfer coefficient converted to prediction of the corresponding heat transfer by means of the heat/mass transfer analogy. Also measured were the local velocities. The experiment revealed the expected spatially periodical character of the flow field and heat/mass transfer distributions. To quantify the heat/mass transfer effects, three procedures are proposed. Compared with the standard planar impinging jet at the optimal nozzle-to-wall distance, the enhancement of the average heat/mass transfer was demonstrated to reach up to 8%.pm201

Annular impinging jet controlled by radial synthetic jets

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.This experimental study focuses on generation and control of annular impinging jets. An annular nozzle was designed with an active flow control system using twelve radial synthetic jets issuing from the central body of the nozzle. Measurements of the wall pressure and wall mass transfer were performed with air as the working fluid. The control action causes modification of the flowfield resulting in changes of the corresponding heat/mass transfer distributions. The convective transfer rate on the stagnation circle can be demonstrably enhanced by 20% at a moderate nozzle-to-wall distance, equal to 0.6 of the nozzle outer diameter.dc201

Comparison of synthetic jet actuators based on sharp-edged and round-edged nozzles

Axisymmetric synthetic jet actuators based on a loudspeaker and on two types of flanged nozzles were tested and compared experimentally. The first type of the nozzle was a sharp-edged circular hole. The second one had a special design with fillets at inner and outer nozzle exit and with a small step in the middle of the nozzle. The function of the step was to prevent the flow reattachment during the extrusion stroke. The actuators with the two types of nozzles were operated at resonance and were compared first qualitatively using a simple phase locked flow visualization. Then the hot-wire anemometer was used to measure velocity distributions along nozzle axis and velocity profiles at the nozzle exit. Comparison of the nozzles was based on evaluation of the characteristic velocity and integral quantities (volumetric, momentum, and kinetic energy fluxes). It was found out that these quantities, which were evaluated at the nozzle exit, differ substantially for both nozzles. On the other hand the velocity flow field in farther distances from the nozzle exit area did not exhibit such prominent differences

Rituximab in adult minimal change disease and focal segmental glomerulosclerosis - What is known and what is still unknown?

Primary forms of minimal change disease and focal segmental glomerulosclerosis are rare podocytopathies and clinically characterized by nephrotic syndrome. Glucocorticoids are the cornerstone of the initial immunosuppressive treatment in these two entities. Especially among adults with minimal change disease or focal segmental glomerulosclerosis, relapses, steroid dependence or resistance are common and necessitate re-initiation of steroids and other immunosuppressants. Effective steroid-sparing therapies and introduction of less toxic immunosuppressive agents are urgently needed to reduce undesirable side effects, in particular for patients whose disease course is complex. Rituximab, a B cell depleting monoclonal antibody, is increasingly used off-label in these circumstances, despite a low level of evidence for adult patients. Hence, critical questions concerning drug-safety, long-term efficacy and the optimal regimen for rituximab-treatment remain unanswered. Evidence in the form of large, multicenter studies and randomized controlled trials are urgently needed to overcome these limitations

Global transpiration data from sap flow measurements : the SAPFLUXNET database

Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land-atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations. Here we introduce the first global compilation of whole-plant transpiration data from sap flow measurements (SAPFLUXNET, https://sapfluxnet.creaf.cat/, last access: 8 June 2021). We harmonized and quality-controlled individual datasets supplied by contributors worldwide in a semi-automatic data workflow implemented in the R programming language. Datasets include sub-daily time series of sap flow and hydrometeorological drivers for one or more growing seasons, as well as metadata on the stand characteristics, plant attributes, and technical details of the measurements. SAPFLUXNET contains 202 globally distributed datasets with sap flow time series for 2714 plants, mostly trees, of 174 species. SAPFLUXNET has a broad bioclimatic coverage, with woodland/shrubland and temperate forest biomes especially well represented (80 % of the datasets). The measurements cover a wide variety of stand structural characteristics and plant sizes. The datasets encompass the period between 1995 and 2018, with 50 % of the datasets being at least 3 years long. Accompanying radiation and vapour pressure deficit data are available for most of the datasets, while on-site soil water content is available for 56 % of the datasets. Many datasets contain data for species that make up 90 % or more of the total stand basal area, allowing the estimation of stand transpiration in diverse ecological settings. SAPFLUXNET adds to existing plant trait datasets, ecosystem flux networks, and remote sensing products to help increase our understanding of plant water use, plant responses to drought, and ecohydrological processes. SAPFLUXNET version 0.1.5 is freely available from the Zenodo repository (https://doi.org/10.5281/zenodo.3971689; Poyatos et al., 2020a). The "sapfluxnetr" R package - designed to access, visualize, and process SAPFLUXNET data - is available from CRAN.Peer reviewe

A new method for fluid input into a hybrid synthetic jet actuator

A new principle of flow rectification for hybrid synthetic jet actuators is introduced in this paper. As is well known, the flow rectification can be best accomplished by means of fluidic diodes. Novelty of the present study are fluidic diodes with two mutually opposed nozzles. Interaction between the periodic jet flows from the nozzles causes a difference between the blowing and suction strokes, resulting in a particularly efficient rectification effect. The distance between the nozzle exits as well as the oscillation frequency were the parameters, which were varied during hot-wire measurements. The combination of those parameters achieving the highest volumetric effciency was identified

The Influence of Geological Engineering and Geotechnical Conditions on Parameter Selection of the Primary Lining of a Road Tunnel in Laliki

Tunel drogowy w Lalikach został wykonany w silnie niejednorodnych, w dużym stopniu zniszczonych tektonicznie i w przeważającej części bardzo słabych utworach fliszowych Karpat Zachodnich. W przeważającej części tunel był drążony w warunkach dużego udziału procentowego bardzo słabych łupków ilastych laminowanych i utworów strefy zwietrzelinowej, niekorzystnego, bardzo stromego nachylenia warstw skalnych i zmiennego zawodnienia z wypływami wody w rozluzowanych strefach tektonicznych. Górotwór ten charakteryzuje się dużą niepewnością rozpoznania jego właściwości i struktury. Praca omawia wpływ warunków geologiczno-inżynierskich i geotechnicznych na dobór parametrów obudowy wstępnej tunelu drogowego. Przeprowadzono analizę deformacji obudowy wstępnej w zależności od procentowego udziału piaskowców i łupków, punktacji klasyfikacji geomechanicznych RMR (Bieniawski 1989) i QTS Tesařa (1979), typów obudowy wstępnej oraz wykorzystania kotew i mikropali. Analiza ta została poprzedzona charakterystyką warunków geologiczno-inżynierskich na trasie tunelu oraz charakterystyką typów zastosowanej obudowy wstępnej. W trakcie drążenia tunelu z wyprzedzeniem w kalocie, kilkakrotnie występowały przemieszczenia obudowy wstępnej kaloty większe od projektowanych maksymalnych. W przypadku, gdy wartości deformacji osiągały stan alarmowy dla danego typu obudowy i nie wykazywały tendencji do stabilizowania się, podejmowano decyzję o jej wzmocnieniu dodatkowymi kotwami, siatką oraz torkretem do czasu osiągnięcia stabilizacji deformacji. W najtrudniejszych warunkach obudowa wstępna była wzmacniana parasolem mikropalowym. Parametry obudowy dobierano, zgodnie z zasadami NATM, na podstawie prowadzonych na bieżąco obserwacji geologiczno-inżynierskich i geotechnicznych. Tunel w Lalikach jest przykładem bardzo słabej samonośności górotworu. Obserwowane przemieszczenia w górotworze wskazywały, że strefa spękań wokół wyrobiska była stosunkowo silnie rozwinięta. Obudowy wstępne stosowane w tego rodzaju warunkach, na niewielkich głębokościach, powinny charakteryzować się stosunkowo dużą nośnością. Doświadczenia, jakie uzyskano wskazują, że realizacja obudowy wstępnej w silnie zmiennych warunkach fliszu karpackiego wymaga prowadzenia szczegółowych badań geologiczno-inżynierskich w trakcie drążenia tunelu, które należy wykonywać na bieżąco wraz z postępem dobowym dla weryfikacji założeń projektowych. W przypadku potrzeby należy zastosować wzmocnienia obudowy wstępnej na podstawie wyników właściwie prowadzonych pomiarów geotechnicznych zachowania się układu obudowa-górotwór.The road tunnel in Laliki was excavated in highly heterogeneous, severely tectonically damaged and mainly very weak rocks of the Western Carpathians flysch. In particular, the conditions were characterized by a high percentage of very weak laminated shale and weathered rock mass, an unfavorable and very steep slope of the rock layers and unstable hydrological conditions with outflows of water in loosened tectonic zones. That structure and properties of the rock mass highly uncertain. This paper describes the influence of geological engineering and geotechnical conditions on the primary lining of a main road tunnel. The deformation of the primary lining was analyzed in terms of the percentage share of sandstones and shale, geomechanical classifications RMR (Bieniawski 1989) and QTS (Tesar 1979), types of the primary lining and the use of rock bolts and micropiles. The analysis was preceded by characterization of geological engineering conditions and technological characterization of applied primary linings. Displacements of the primary lining, greater than acceptable, occurred several times in a top heading during tunneling. The primary lining was reinforced by additional rock bolts and wire mesh, a thicker layer of shotcrete and micropiles if deformation reached the emergency state for some types of linings and they didn't indicate any tendency for stabilization. The reinforcement was used until the deformation stabilization was achieved. In the most difficult conditions, the lining was reinforced by a longer micropile umbrella. Parameters for the primary lining were selected on the basis of ongoing geological engineering and geotechnical measurements, in accordance with NATM's principles. The rock mass around the tunnel in Laliki is an example of weak carrying capacity. The observed displacements in the rock mass indicate that the disturbed zone around the tunnel was heavily developed. The primary lining used in such conditions must bear a relatively high load capacity from overlying loosened material and therefore the lack of interaction with the surrounding rock mass should be assumed. The data obtained indicate that the use of the primary lining in the highly variable conditions in the Carpathian flysch requires accurate geological engineering and geotechnical analysis during the day-to-day process of tunneling in order to verify the projected assumptions. The primary linings should be reinforced as needed based on the results of geotechnical measurements, monitoring the interaction between the rock mass and the system of lining

Active control of the jet in coaxial arrangement

An axisymmetric jet flow, issuing as a fully developed flow from a long straight pipe at Re = 1600 and 5500, was actively controlled by an annular synthetic jet. The Pitot tube, hot-wire anemometry (CTA) and flow visualization were used for an experimental investigation of the flow control. The working fluid was air. The effect of varying Strouhal number (St = (0.18÷1.94)) on a width and entrainment of the main jet flow was studied. It was found that the main jet is the most sensitive to the actuation at St = 0.28÷0.60 and St = 0.18, for Re = 1600 and Re = 5500, respectively