Upstream Pressure Research Articles

The influences of jet axis switching and aerodynamic focusing on aerosol deposition in converging–diverging slit impactors

The deposition pattern or “linewidth” of an inertial particle deposit from acceleration of an aerosol through a high aspect ratio slit nozzle-substrate system is influenced by particle size-dependent aerodynamic focusing. In addition to this, high aspect ratio jets will eventually undergo downstream “jet-axis switching”, wherein the jet profile shrinks along its major axis and elongates in the direction of the minor axis. Jet axis switching in an aerosol may also lead to “rotated” particle deposits. In this study, we use a converging–diverging slit nozzle system with a major axis length of 8 mm and a throat width (minor axis) of 200 μm to examine the deposition patterns of monodisperse particles in the 100 nm–5 μm diameter range, in air with an upstream pressure of 252 Torr and variable downstream pressure in the 3–50 Torr range. The nozzle-to-substrate distance L∗ is varied from 90 to 248 times longer than the throat width. We find deposition patterns that are strongly dependent on particle size, downstream pressure, and L∗. Depending on particle diameter and operating conditions, we obtain deposits resembling the nozzle dimensions and orientation, deposits which are completely switched (perpendicular to the nozzle), or deposits which are relatively symmetric and focused at a center point. The latter appear to be the result of the combined effects of jet axis switching and aerodynamic focusing. In general, the influence of jet axis switching is more pronounced on smaller particles at higher downstream pressures, and with larger distances to the substrate. The extent of switching and area of the deposit are also both inversely related to the particle Stokes number.

AN EXPLANATION FOR UNDERESTIMATION OF SYSTOLIC PRESSURE IN CUFF-BASED MEASUREMENT

Objective: Auscultatory blood pressure measurement is the gold standard used to calibrate other measurement devices. However, auscultatory tests systematically underestimate systolic blood pressure (SBP) and overestimate diastolic blood pressure (DBP). While there is some literature explaining overestimation, there is no physical understanding of the underestimated SBP. Our objective is to understand why auscultatory measurement results in the underestimation of SBP. The SBP is recorded when the artery first begins to reopen, during cuff deflation. Prior to this, the cuff cuts off the blood supply and the pressure in the distal part of the artery drops to the venous pressure. We propose this low pressure as a cause of underestimation and investigate this through a controlled variation of the downstream pressure in an experimental rig. Design and method: Figure 1 shows a schematic of the rig. The tube representing the artery is compressed under an inflatable cuff. The downstream pressure is varied between tests. The upstream pressure is fixed with a header tank for simplicity. Therefore, the ‘blood pressure’ measured in the rig is constant rather than oscillatory, resulting in only a single opening of the artery as the cuff is deflated, rather than repeated opening and closing. This single opening is equivalent to the first opening of the artery in the body and so represents the systolic measurement. Figure 2 depicts an example test run. The cuff around the artery is gradually deflated, and the reopening of the artery is indicated by the rise of the downstream pressure (point a). The cuff pressure at this timestamp is recorded (point b), representing the measured SBP. Results: Figure 3 shows that the recorded cuff pressure is a function of downstream pressure, with the cuff reading giving greater underestimation of SBP when the downstream pressure is lowered. Conclusions: The delay in artery reopening which results from lowering the downstream pressure provides an explanation for the systematic underestimation of SBP. This information may lead to recommendations for new measurement protocol which avoid a drop in the pressure distal to the cuff, and the resulting underestimation of SBP.

The flow pattern effects of hydrodynamic cavitation on waste activated sludge digestibility

The disintegration of raw sludge is of importance for enhancing biogas production and facilitates the degradation of substrates for microorganisms so that the efficiency of digestion can be increased. In this study, the effect of hydrodynamic cavitation (HC) as a pretreatment approach for waste activated sludge (WAS) was investigated at two upstream pressures (0.83 and 1.72 MPa) by using a milli-scale apparatus which makes sludge pass through an orifice with a restriction at the cross section of the flow. The HC probe made of polyether ether ketone (PEEK) material was tested using potassium iodide solution and it was made sure that cavitation occurred at the selected pressures. The analysis on chemical effects of HC bubbles collapse suggested that not only cavitation occurred at low upstream pressure, i.e., 0.83 MPa, but it also had high intensity at this pressure. The pretreatment results of HC implementation on WAS were also in agreement with the chemical characterization of HC collapse. Release of soluble organics and ammonium was observed in the treated samples, which proved the efficiency of the HC pretreatment. The methane production was improved during the digestion of the treated samples compared to the control one. The digestion of treated WAS sample at lower upstream pressure (0.83 MPa) resulted in higher methane production (128.4 mL CH4/g VS) compared to the treated sample at higher upstream pressure (119.1 mL CH4/g VS) and control sample (98.3 mL CH4/g VS). Thus, these results showed that the HC pretreatment for WAS led to a significant increase in methane production (up to 30.6%), which reveals the potential of HC in full-scale applications.

Modeling of dual-skin asymmetric hollow fiber microporous membranes for predicting the skins parameters separately using gas permeation test

This study presented a comprehensive gas permeation model to predict the skin parameters of a complex system, specifically a hollow fiber membrane with an asymmetric structure consisting of two external and internal skin layers. According to the work of Haefer for n segments of pores connected in series as in hollow fiber membranes, applying the Wakao et al. model, a comprehensive model for the transition regime was derived. The model was examined against the various fabricated PES and PEI hollow fiber membranes. Unlike conventional models, the proposed method predicted the mean pore size and mean pore length independent of surface porosity for each skin layer. The study revealed valuable insights into i) the middle pressure, ii) the difference between the skin parameters of the two membrane skins, and iii) the impact of the feeding direction on gas permeation behavior. It was shown that the dependency of permeation behavior on the feeding direction is linked to the influence of middle pressure on viscous flow, which is closely related to surface porosities of each side. It is evident that even the slightest variations in the fabrication parameters can result in different structures. Furthermore, it is evident that the assumption of neglecting slip flow was reasonable within the experienced Knudsen number range. The model also highlighted that the skin parameters of the two skin layers may not be identical, a distinction not captured by the current models. The traditional approach of setting the middle pressure as the average of the upstream and downstream pressures has been improved by expressing it as a linear function of both pressures. In the feed side, higher pressures led to dominant viscous flow, whilst the permeate side was more influenced by the free molecular regime due to lower pressures. There existed a competition between the Knudsen flow and the viscous flow at a specific Knudsen number for the feeding side pores, whether it was the inner or outer surface. The finding emphasized the significance of porosity values on each side in determining the proximity of middle pressure to feed and permeate side pressures, underscoring the importance of accurate knowledge of surface porosities, mean pore sizes, and pore lengths for both skin layers in understanding processes involving porous dual-skin hollow fiber membranes.

Assessment of cavitation erosion on an asymmetric hydrofoil based on energy conversion via a multiscale approach

Cavitation erosion is a long-standing issue, which plays a pivotal role in the material damage of much hydraulic machinery. However, despite abundant numerical research on cavitation erosion assessment, bubble dynamics has been commonly overlooked. Consequently, we develop an improved cavitation erosion model based on energy conversion and assess an ALE15 hydrofoil surface by its incorporation into a multiscale approach. Our erosion model stands out in considering the bubble behaviors throughout its entire lifespan to eliminate the influence of bubble oscillation on cavitation erosion. Using the bubble information in the well reproduced cavitating flow, we evaluate both the cumulative and instantaneous cavitation erosion, and the results show satisfactory agreement with the experimental pattern. Our findings demonstrate that frequent vapor-liquid alternations, induced by the collaborative effects of upstream pressure gradients and main flow, increase the potential for erosion risk at the hydrofoil leading edge. Downstream erosion primarily results from secondary shedding and the collapse of U-shaped cavities’ legs. By contrast, the acoustic energy emitted by the shedding cavities traveling farther and upwards away from the hydrofoil leads to negligible erosion on the surface.

Integrating transient pressure and flow data for determination of hydraulic permeability and specific storage of a shale sample: Experimental tests and sensitivity analysis

This paper describes a comprehensive investigation to accurately determine the hydraulic permeability k and the specific storage Ss of a shale sample. One-dimensional pressure transient tests were conducted on a cylindrical sample under various levels of pore and confining pressures. For the boundary conditions, the upstream pressure was kept constant using a syringe pump, and the downstream storage was minimized for reducing the test duration. Both the downstream pressure and the upstream fluid flow into the sample were continuously recorded throughout the transient period. To estimate the hydraulic properties, the curve fitting technique was applied to the pressure and flow data using theoretical curves. We found that the pressure curve was sensitive to the ratio of hydraulic permeability to the specific storage (k/Ss), but not sufficient to determine the individual components (k and Ss). The upstream flow curve was sensitive to the specific storage but less sensitive to the permeability. Based on our sensitivity analysis, we present a combination of two objective functions of flow and pressure data to optimize both hydraulic properties with reasonable uncertainty. An alternative is to first use the flow data to determine Ss and then use pressure data with the predetermined Ss to obtain the remaining k.

A nozzle design for mitigating particle slowing in the bow shock region during micro-cold spray of 8 YSZ films

During micro-cold spray deposition, also referred to as the aerosol deposition method or vacuum kinetic spraying, performed with conventional nozzles, the particle impact velocities decrease drastically with particle size for fine particles <500 nm in diameter due to slowing in the stagnation region. A new design for a nozzle that contains pressure relief channels is proposed that allows the pressure in the stagnation region downstream of the bow shock to be reduced. This reduced stagnation pressure results in less particle slowing compared to conventional nozzle geometries, particularly for smaller or less dense particles. The effects of the channel geometry on the particle impact velocity are systematically investigated by independently varying the channel parameters. Calculations show that the impact velocities for 100 and 200 nm yttria stabilized zirconia particles is increased by 111% and 31%, respectively, for a selected pressure relief channel nozzle when compared to a comparable conventional nozzle. Although impact velocities are increased, a tradeoff exists with this nozzle design in that the particle focusing in the nozzle is decreased and some of the particles may be removed from the aerosol by the channels. Experiments using a nitrogen as a carrier gas at ∼40 kPa upstream pressure show that, despite the loss of larger particles into the relief channels, the deposition efficiency is improved by 300% when depositing films from fine 8 YSZ powder with the pressure relief nozzle compared to a conventional nozzle.

Effect of upstream injection on local flame intensity in a scramjet combustor fueled with liquid kerosene at Mach 4 flight condition

The intensity of the local flame generated by spark ignition was investigated in a scramjet combustor fueled with liquid kerosene under Ma 4 flight conditions. The study utilized wall pressure evolution and high-speed imaging during experiments to assess the local flame intensity. The rise in wall pressure near the aft edge of the cavity was found to be an indicator of local flame intensity, and the impact of upstream injection on the flame intensity was discussed. The results demonstrated that the dense spray resulting from upstream injection suppressed the local flame intensity. In particular, the spray in close proximity to the shear layer caused weakening of the local flame through evaporation. Additionally, the height of penetration increased with higher upstream injection pressure, leading to the dense spray being located further away from the shear layer flame and thereby strengthening the local flame intensity. Moreover, a larger injection distance marginally decreased the flame intensity due to the presence of additional spray near the wall. Conversely, injections with higher mass rates resulted in a weaker flame intensity as more spray was distributed into the cavity.

Aeroelasticity analysis of anisogrid lattice sandwich cylindrical shells: Extended potential and piston theories

Based on the extended potential and piston aerodynamics theories, buckling and vibration analysis of sandwich cylindrical shells subjected to external airflow in both subsonic and supersonic regimes is presented. Sandwich cylindrical shells are considered to be made of same homogenous face sheets and an anisogrid composite lattice core with hexagonal cells. An equivalent single layer (ESL) theory in the framework of classical Love’s shell theory is used to formulate the global mechanical behavior of such shells. According to the extended potential and piston aerodynamic theories, aerodynamic pressure distributions are determined for steady, inviscid, irrotational compressible, and external airflow. The closed–form solutions of critical upstream pressure and natural frequency are developed for different boundary conditions using the Galerkin method. Finally, case studies are presented to compare between results of extended potential and piston theories and investigate the effects of upstream speed, geometric ratios, boundary conditions, and lattice specifications on various response quantities. Findings indicate that the differences in results of extended potential and piston theories are less than 3% in the supersonic regime with 2.3 ≤ M ∞ ≤ 2.7 for intermediate-length shells with a wide range of R . The piston theory is inadequate for analyzing aeroelasticity behavior of very long thin sandwich cylindrical shells.

Utilization of machine learning for the estimation of production rates in wells operated by electrical submersible pumps

AbstractIn this study, a neural network model is developed for the prediction of oil flow rates in wells lifted by electrical submersible pumps (ESPs). Three attributes of the model in this work make this study unique. First, the knowledge on the computational cost of models has been presented, a rarity in most neural network models on this subject; second, the models have been explicitly presented, a feature uncommon in published ANN predictive modelling studies; and third, it includes a sensitivity analysis of input variables. The dataset utilized for the model development comprises 275 data points collected from ESP-lifted wells in the Middle East. Statistical evaluation of the model’s performance using the metrics such as mean square error, root mean square error and coefficient of determination demonstrates high predictive accuracy with respective values of 0.0000201861, 0.00449 and 0.999. In order to ascertain the parametric importance of the inputs, Garson’s algorithm was utilized. In this regard, choke size and upstream pressure had the highest influence (19% and 16%, respectively), while casing head pressure had the least effect (4.8%) on oil flow rate. In terms of memory requirements and processing speed for software applications, the model had a memory footprint of 888 bytes and required 191 multiply and accumulate operations to give an output. By utilizing the proposed models, the time-consuming separator tests measurements of flow rate would no longer be necessary and real-time results could be provided in the field. This work would be useful to production engineers who seek a quick and accurate means of estimating oil flow rate from ESP wells in real time.

Study on ammonia transport and separation in Aquivion® perfluoro sulfonated acid membranes

The present study reports the results of a series of sorption and permeation tests of pure ammonia as well as nitrogen and hydrogen carried out on Aquivion C87-05 (short-side chain perfluoro sulfonic acid ionomer). Such material is indeed of interest for possible applications in sustainable processes for ammonia production, either as base material for polymer electrolyte membranes in low-temperature electrochemical ammonia synthesis or as a membrane for effective product separation.NH3, N2, and H2 permeation tests are performed at different temperatures (20, 35, and 50 °C) and both in dry and humid conditions (R.H. up to 80%), aiming to assess the influence of these parameters on the resulting permeabilities, while ammonia sorption is inspected at the same temperatures, and pressures up to near saturation conditions.Pure ammonia permeability reached outstanding values around 7000 Barrer in dry Aquivion membranes, revealing an increasing trend with upstream pressure, while it decreased with temperature. The same behavior is recorded for NH3 solubility, indicating that sorption drives the ammonia transport through the membrane.The obtained separation performances are found to be significantly better than those of other polymeric membranes proposed for the same separations, as compared to a permeability-selectivity plot.

The Magnetopause Deformation Indicated by Fast Cold Ion Motion

AbstractThe magnetopause deformation due to the upstream magnetosheath pressure perturbations is important to understand the solar wind‐magnetosphere coupling process, but how to identify such events from in situ spacecraft observations is still challenging. In this study, we investigate magnetopause crossing events with fast‐moving cold ions in the magnetosphere from Magnetospheric Multiscale observations, and find when fast‐moving cold ions are present at the magnetopause, they are closely associated with the magnetopause deformation, which is featured by fast magnetopause motion and significant magnetopause normal deflection from model predictions. Therefore, fast‐moving cold ions can be a useful indicator to search for magnetopause deformation events. By integrating the cold ion speed, the inferred magnetopause deformation amplitude varies from 0.1 to 2.0 RE. Further statistics indicate that such magnetopause deformation events prefer to occur under quasi‐radial interplanetary magnetic field and fast solar wind conditions, suggesting high‐speed magnetosheath jets could be one direct cause of magnetopause deformations.

Comparison of partial and deep energy detachment behaviors with Ar seeding on EAST new corner slot divertor

It is necessary for future fusion reactor to reduce the heat fluxes on the entire divertor target, especially if view of long pulse high performance operation. In recent EAST experiments, partial energy detachment without confinement degradation, and deep energy detachment with protection of the entire divertor target have both been confirmed on EAST corner slot divertor by argon (Ar) seeding, which can provide reference for the divertor protection on future fusion reactors. In the deep energy detachment state, the electron temperature T et along entire lower outer divertor target decreases to less than 10 eV and heat fluxes are also strongly mitigated with peak heat flux reduction of more than 90%. Compared to the attached state, there is a moderate confinement degradation with H 98,y2 from ∼1 to ∼0.9 because of Ar radiation in the core region. This confinement degradation can be avoided in the partial energy detachment state, where the radiative power losses in the core are reduced. The experiment and SOLPS-ITER simulation results show that there is no decrease of particle flux js on the divertor target in the partial energy detachment state because the momentum loss in the SOL region is not strong enough. With increasing Ar seeding, there is a js decrease in the deep energy detachment state. The increases of momentum and power losses in the SOL region, and the decrease of upstream pressure all contribute to the js reduction.

A parametric large-eddy simulation study of wind-farm blockage and gravity waves in conventionally neutral boundary layers

We present a suite of large-eddy simulations (LES) of a wind farm operating in conventionally neutral boundary layers. A fixed 1.6 GW wind farm is considered for 40 different atmospheric stratification conditions to investigate effects on wind-farm efficiency and blockage, as well as related gravity-wave excitation. A tuned Rayleigh damping layer and a wave-free fringe-region method are used to avoid spurious excitation of gravity waves, and a domain-size study is included to evaluate and minimize effects of artificial domain blockage. A fully neutral reference case is also considered, to distinguish between a case with hydrodynamic blockage only, and cases that include hydrostatic blockage induced by the air column above the boundary layer and the excitation of gravity waves therein. We discuss in detail the dependence of gravity-wave excitation, flow fields and wind-farm blockage on capping-inversion height, strength and free-atmosphere lapse rate. In all cases, an unfavourable pressure gradient is present in front of the farm, and a favourable pressure gradient in the farm, with hydrostatic contributions arising from gravity waves at least an order of magnitude larger than hydrodynamic effects. Using respectively non-local and wake efficiencies $\eta _{nl}$ and $\eta _{w}$ , we observe a strong negative correlation between the unfavourable upstream pressure rise and $\eta _{nl}$ , and a strong positive correlation between the favourable pressure drop in the farm and $\eta _{w}$ . Using a simplified linear gravity-wave model, we formulate a simple scaling for the ratio $(1-\eta _{nl})/\eta _{w}$ , which matches reasonably well with the LES results.

Critical heat flux, heat transfer and pressure drop at high mass fluxes for R123 in a single microchannel

This paper presents new experimental data on pressure drop, heat transfer coefficient, and critical heat flux during flow boiling of low-pressure fluid R123 in microchannels. High mass velocities were used, above the values found in the literature in tests with this fluid. Experiments were conducted in a single smooth and horizontal microchannel, with an internal diameter of 1.1 mm and heating sections of 46 and 100 mm. The mass velocities used were between 1500 and 7500 kg/m2s. Saturation temperature ranged from 40.1 to 85.1 oC. The outlet vapor quality varied between -0.54 and 0.53 for the CHF results, between 0 and 0.5 for the pressure drop results, and between 0 and 0.35 for the HTC results, respectively. Record critical heat flux values for flow boiling of R123 in smooth microchannels were achieved, reaching 1.44 MW/m2. An analysis was made of the influence of an upstream pressure drop in avoiding instabilities during critical heat flux experiments. The highest heat transfer coefficient values during convective boiling of R123 in smooth microchannels were also obtained, with values close to 43.3 kW/m2K. The saturation temperatures used were among the highest for flow boiling of R123 in smooth microchannels found in the literature. Correlations for frictional pressure drop, heat transfer coefficient, and critical heat flux were evaluated in predicting the experimental data. An analysis was made on the influence of the void fraction correlation when estimating both the accelerational and frictional pressure drop.

Detekcija udara i poboljšanje dizajna za pneumatski kontrolni ventil

The existence of shockwaves in pneumatic valves can greatly affect their efficiency and cause damage to important parts. This study focuses on the examination of a cost-effective pneumatic directional control valve with the aim of augmenting its output mass flow rate. Emphasis is placed on scrutinizing and modifying the critical flow area to facilitate increased flow rates under specific upstream pressures while eliminating the formation of shockwaves. To achieve these objectives, numerical simulations are harnessed to accurately capture the onset of shockwave formation and elucidate the associated conditions, allowing optimizing valve's capacity without introducing the risk of shockwave occurrence. The modified valve design demonstrated the capability to eliminate shockwave formation within the valve while concurrently increasing the mass flow rate by up to 70% within the same range of inlet pressures. This novel approach holds substantial promise for enhancing system response and represents a significant contribution to the field of pneumatic control valve design.

Experiment and numerical investigation on flow characteristics and near-field structure of dense phase CO2 pipeline leakage

Accidental leakage of high-pressure CO2 is not only a safety hazard, but also may have a great negative impact on the operating efficiency of some circulating systems. To analyze the accident hazards and improve the ability to predict the transient release flow behavior of high-pressure CO2, a set of small pipeline leakage test equipment was built. The changes of near-field pressure, temperature, and jet structure under different upstream pressure (6–12 MPa), temperature (280–300 K) and orifice diameter (5 mm, 10 mm, 20 mm, 40 mm) were analyzed. Secondly, as a supplement to the experiment, the near-field CO2 gas phase distribution and critical mass flow were studied by numerical model. The results show that the near field pressure peak is negatively correlated with the initial upstream pressure, but positively correlated with the release diameter. In addition, the increase of upstream initial pressure and release diameter will lead to the increase of radial development range of near-field jet cloud. Based on the numerical results, an empirical correlation of critical mass flow based on upstream initial conditions and RHP is established. The error between the experimental data and the predicted value within the range of the correlation is within ± 18%. The research data and results can help to enhance the understanding of the rapid release characteristics of high-pressure CO2 in the near field region and provide a basis for the study of CO2 diffusion in the far field region and the leakage risk assessment.

Investigation of different configurations of alumina packed bed reactor for coke free conversion of benzene

Conversion of producer gas tar without coke generation is a great challenge. This study investigates conversion of tar model benzene using different configurations of highly non-porous ɣ-Al2O3 packed bed reactor at 1000–1100 0C. The configurations comprised of different positions (relative to top (P1), center (P2) and bottom (P3) of reactor furnace), heights (5, 13 and 25 cm) and particles sizes (0.5, 3 and 5 mm) of alumina packed bed. Steam and CO2 were used as reforming media for tested benzene concentrations (0.4–1.8 vol%). The results showed benzene conversions of 48–91% with negligible steady thin coke generation using a packed bed (height: 25 cm, particles size: 3 mm) at P1. Whereas, relative high benzene conversions of 63–93 and 68–95% at P2 and P3 respectively with unsteady thick coke generation at benzene concentrations greater than 0.4 vol% increased differential upstream pressures (DUPs) of beds. Similar unsteady coke generation at benzene concentrations greater than 0.8 vol% and temperature of 1100 0C was observed with packed beds of heights of 5 and 13 cm, and particles size of 0.5 mm at P1. Generation of unsteady coke with condensed structure as evidenced by its characterization was attributable to increased benzene polymerization and reduced bed surface gasification reactions due to improperly installed packed bed. Developed kinetic model predicted well the generated coke. As conclusion, properly installed alumina packed bed pertaining to tar concentration and other experimental conditions may inhibit coke generation during tar conversion.

On flow disturbances caused by pressure taps in highly elastic flows around a microfluidic cylinder

The objective of this work is to characterize the onset of laterally asymmetric flow of viscoelastic solutions around a confined microfluidic cylinder, which was encountered in a recent study [Rodrigues et al., J. Non-Newtonian Fluid Mech. 289, 104406 (2020)]. To this end, two non-Newtonian fluids were employed in the same micro-geometry. Two microchannels were studied, both with a cylinder of diameter 75 μm, aspect ratio (channel height over width) of 0.37, and blockage ratio (cylinder diameter over channel width) of 0.28, differing only on the width of the pressure taps, located 500 μm up- and downstream from the respective cylinder face, on opposing walls. The working fluids consist of two poly(ethylene oxide) solutions: an elastic weakly shear-thinning fluid and an elastic shear-thinning fluid. Micro-Particle Image Velocimetry and streak imaging techniques were used to evaluate the flow over a Weissenberg number range 100≤Wi≤500, while maintaining a low Reynolds number, Re &amp;lt; 1. The elastic shear-thinning solution showed laterally asymmetric flow past the cylinder with both pressure tap designs, while with the weakly shear-thinning solution asymmetric flow was only observed with the wider pressure tap intake. In both cases, the fluids preferentially chose the cylinder/wall gap opposing the upstream pressure tap, which was found to influence the flow greatly, seemingly associated with time-dependent flow and possibly the lateral flow asymmetry itself. This work brings to light the necessary compromise between optimal pressure tap design for quality pressure measurements and minimal flow interference, due to the increased susceptibility of elastic microfluidic flows to flow perturbations.

Numerical study of divertor detachment in TCV H-mode scenarios

The effect of divertor closure and nitrogen seeding on the detachment process has been studied by performing 2D numerical simulations of tokamak à configuration variable (TCV) H-mode divertor scenarios with the SOLEDGE3X-EIRENE edge plasma transport code. The simulations reveal that, in the cases with only deuterium gas fuelling, detachment occurs at a similar level of divertor neutral pressure (0.76 Pa), despite the difference in divertor closure achieved by changing the length of the outer baffle. Nitrogen reduces the target temperature with little effect on the upstream density and momentum loss but drops the upstream pressure, leading to a decrease in the target particle flux and divertor neutral pressure. Furthermore, when the radiation front starts to move up from the outer target, the peak parallel heat flux level at the outer target remains approximately the same ( MW m−2), regardless of whether it is a deuterium fuelling scan, a nitrogen seeding scan at a fixed fuelling rate, or a change in the length of the outer baffle. An empirical partial detachment qualifier calibrated on AUG experimental data was compared with the TCV simulations. The results show good agreement in detachment state prediction, indicating the potential of this detachment qualifier to be applied in devices of different sizes, emphasizing the combined influence of input power entering the divertor, neutral pressure, and the concentration and species of impurity in achieving divertor detachment.