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Convective thermo-hydraulic phenomena of turbulent airflow through a solar rectangular channel with modern barriers and blocks
No full textResearchers are currently deeply engrossed in the convective analysis of thermo-hydraulic turbulent air-flow phenomena through a rectangular channel, a field of study that holds immense significance in various engineering applications (continuous metal casting, solar heaters, glass exchangers, laser pulse heating, and transpiration cooling). The hydro-thermal characteristics of turbulent air-flow phenomena in a rectangular channel, particularly when embedded with various types of modern barriers (plane, trapezoidal, diamond, and triangular) and blocks (placed in the intermediate zone of barriers), have been the subject of intense numerical study (this type of compact study has not done before) for several values of Reynolds numbers (Re). To identify the most suitable solar heater tube configuration, we have meticulously examined 25 cases out of all the considered cases. The finite volume approach has been employed to discretize the governing equations, and the FLUENT software has been utilized to visualize the simulation results. At Re = 20,000, 87,300, 1,00,000, and 1,10,000, we have thoroughly investigated the profiles of flow velocity at different locations of the plane, velocity streamlines, absolute pressure drop, temperature, average friction factor, coefficients of skin friction, local and average Nusselt number for all cases. The maximum velocity has been found downstream of the second barrier near the outlet. From all 25 different cases, we have discovered that the rate of thermo-hydraulic phenomena is significantly boosted by introducing rectangular-diamond barriers. These findings, arrived at through a comprehensive and rigorous research process, are not only insightful but also hold the potential to revolutionize the thermal exchange in machines and equipment, making them more cost-efficient
A strongly mass-conservative method for the coupled Navier-Stokes and Darcy-Forchheimer equations
No full textIn this paper, we propose and analyze a strongly mass-conservative numerical scheme for the coupled Navier--Stokes and Darcy--Forchheimer system in both two and three spatial dimensions. The two subproblems are coupled through physically relevant interface conditions, including mass conservation, balance of normal forces, and the Beavers--Joseph--Saffman condition. We employ a staggered discontinuous Galerkin method for the Navier-Stokes equations and use standard mixed finite elements for the Darcy-Forchheimer problem. The proposed formulation incorporates the interface conditions directly, without introducing Lagrange multipliers on the interface or artificial numerical fluxes on the mesh skeleton. As a consequence, although discontinuous Galerkin elements are used in the free-flow region, the resulting discrete velocity field is globally -conforming across the entire domain. In particular, the incompressibility constraint is satisfied exactly in the free-flow region, thereby yielding strong mass conservation over the entire computational domain. Under a suitable small-data assumption, we establish the well-posedness of the resulting nonlinear discrete system. Owing to the exact preservation of mass conservation, the proposed scheme exhibits a pressure-robust behavior, in the sense that the velocity approximation is insensitive to pressure effects. Numerical experiments are presented to illustrate the stability and robustness of the method, including its performance in regimes involving small viscosity, large pressure, and limited solution regularity
Radiative neutron capture cross section of
No full textAccurate neutron capture cross sections are essential for the design and operation of fast reactors using MOX fuels. For Pu, the Nuclear Energy Agency (NEA) recommends 8–12% accuracy in the fast energy region (2–500 keV), compared to the current uncertainty of 35%. Moreover, integral experiments and previous measurements suggest the evaluated Pu(n,) cross section is overestimated, particularly in the JEFF-3.3 library, which shows a 14% overestimation between 1 keV and 1 MeV. Recent measurements from LANSCE reported a 20–30% reduction in the 1–40 keV range relative to evaluations. To solve these discrepancies, the Pu(n,) cross section was measured from 1 to 600 keV at CERN n_TOF-EAR1 facility using a 95(4) mg Pu target, enriched to 99.959%. Gamma rays from neutron capture were detected with an array of scintillators and a novel application of the Pulse Height Weighting Technique was employed. The resulting cross section presents a systematic uncertainty between 8 and 12%, reducing the current uncertainties of 35% and achieving the accuracy requested by the NEA. Analysis using FITACS produced average resonance parameters, consistent with the analysis of the resolved resonance region. Our data align well with Wisshak and Käeppeler, and are 10–14% lower than JEFF-3.3 in the 1–250 keV range, helping to achieve consistency with integral benchmarks. At higher energies, our results are in reasonable agreement with ENDF/B-VIII.1 and JEFF-3.3. In contrast, DANCE results appear to underestimate the cross section by a factor of 2–3 above a few keV
A reassessment of the role of high
No full textWe present updates within the MSHT global PDF fit that focus on the high x region, and on improving our understanding of the interplay of various theoretical contributions and experimental constraints here. We revisit the question of target mass and higher twist corrections, considering their impact for the first time at approximate LO order in a global PDF analysis. Their inclusion is found to be moderate but not negligible on both the PDFs and preferred value of the strong coupling. Increased stability in these at LO is observed in comparison to lower orders. We also study the impact of an updated treatment of various fixed-target DIS data, the inclusion of SeaQuest fixed-target Drell Yan data, and new ZEUS data that extends coverage into the high x region. The SeaQuest data have the largest effect of these, in particular on the light quark separation at high x, while the impact of the other updates is rather mild
Impact of embedded circumplanetary winds on the circumstellar disk. I. Reshaping the local accretion environment
No full textAmong the uncertainties related to the growth of giant planets is the existence of winds at a protoplanetary scale. Such outflows have been proposed to explain kinematic and chemical structures in protoplanetary disks.
We investigate the immediate impact of circumplanetary outflows on the circumstellar disk environment, the planetary vicinity, and planetary growth.
We performed 3D hydrodynamic simulations using , implementing a parametric wind launched from the vicinity of an embedded planet. FARGO3D
Although the imposed configurations for the outflows do not significantly alter the global structure of the disk, they do substantially redistribute material in the vicinity of the embedded planet. In particular, the wind redirects accretion flows from polar to equatorial latitudes, resulting in variable accretion patterns over time. Although the mass accretion rate variations depend on the efficiency of the outflows, their presence diminishes the accretion rate over time and the total mass reservoir within the Hill sphere and the planet's direct vicinity, potentially slowing or limiting planetary growth
Fostering sustainable fermentation system for alternative food source: Local spiced-modified
No full textThis study evaluates the impact of modifying traditional ragi (Na Ko Liong, NKL) with locally sourced spices (black pepper, jamu chili, garlic, galangal) on the quality of black glutinous rice tape (tape injin), a Balinese-Indonesian fermented food rich in anthocyanin antioxidants. Using a randomized complete block design with three replications, five ragi concentrations (0.6%, 0.9%, 1.2%, 1.5%, 1.8% w/w) were tested against a control. The 1.5% spice-modified ragi yielded optimal results: pH of 4.12 ± 0.05, total alcohol of 4.8 ± 0.3%, total acid of 0.45 ± 0.02%, with high microbial counts (mold of 6.2 × 105 CFU/g, yeast of 5.8 × 105 CFU/g). Sensory scores, as assessed by 10 trained panellists, showed superior taste (6.4 ± 0.4), aroma (6.2 ± 0.3), texture (6.3 ± 0.2), and overall acceptance (6.3 ± 0.3), which were significantly better (p × 0.05) than those of the control. Spice bio actives, such as allicin and piperine allegedly, enhanced microbial activity and stability aligning with reports of reduced fermentation failure in similar systems. This innovation supports sustainable food security by leveraging local resources
Deciphering transmission spectra by exploring the solar paradigm
No full textAims. Transmission spectroscopy allows to measure the wavelength dependence of the transit signal of an exoplanet, thus enabling probing of its atmospheric composition. However, the transmission spectrum also carries information of the host star, generally referred to as ‘contamination‘. Stellar activity leads to an apparent change in the stellar radius, directly impacting the transit depth. This contamination is regarded as the major hurdle in discovering and characterising the atmospheres of exoplanets.
Methods. The objective is to understand how the chromatic effect (i.e. the wavelength dependence) of the stellar activity-induced transit depth depends on the surface distribution of magnetic features. The surface distribution of other stars generally is unknown, with the exception of our very own star, the Sun. We therefore investigate the solar paradigm as ‘ground truth’ to explore how much the chromatic effects depends on the distribution of magnetic features. In particular, we explored the impact of centre-to-limb variations (CLV) of the magnetic features and their resulting chromatic effect. Specifically, we investigated the solar paradigm as the ‘ground truth’.
Results. We utilised spot and faculae masks obtained from SDO/HMI magnetograms and intensitygrams together with the SATIRE approach of calculating solar variability to calculate the chromatic dependence of the apparent radius of the Sun for the last solar cycle. We tested several approaches to convolving the area coverage with the spectra to uncover the potential biases and we investigated the drivers responsible for the chromatic effect.
Conclusions. We find that using a simplified approach that only relies on the disc area coverage and neglects CLV in the spectra to calculate the chromatic effects lead to an underestimation of the apparent radius. In particular, for the faculae component, the CLV need to be taken into account accordingly, especially since the facular area coverage is by far larger than that of spots for stars with near-solar activity level. We report that this chromatic dependence can be detected in transits of an Earth-sized and a Jupiter-sized planet. Additionally, we assessed the amplitude of this effect between solar minimum and solar maximum. We found that for a Jupiter-like transit this amplitude is at the level of 40 ppm, well above the 10 ppm noise floor of JWST. However, this effect is only on the level of 0.4 ppm for the Earth-like transit
Hotspot images driven by magnetic reconnection in Kerr–Sen black hole
No full textIn the Kerr–Sen black hole, this study investigates the changes in hotspot images before and after the occurrence of magnetic reconnection. After reviewing the Comisso–Asenjo magnetic reconnection process and introducing the hotspot imaging method, we examine the temporal evolution of hotspot intensity, including when energy extraction occurs, when it does not occur, and when the observer’s azimuthal angle is altered. We also discuss the influence of the black hole’s expansion parameter and spin on hotspot imaging. The results indicate that the first flare may serve as a potential signature of ongoing energy extraction; changing the observer’s azimuthal angle may alter the time interval between the first and second flares; a larger expansion parameter makes it more difficult to identify the energy extraction signal, and a higher spin also makes it more challenging to detect the energy extraction signal
The RoPES project with HARPS and HARPS-N
No full textContext. Earth-like planets orbiting in the habitable zone of K- to G-type stars create an RV effect in amplitude of less than 1 ms−1 and have orbital periods of hundreds of days. Only long-term RV surveys with sub-meter per second precision instruments can explore the outer regions of Sun-like stars and look for Earth-like planets and super-Earths. Detecting Earth-like or super-Earth planets in the habitable zone of Sun-like stars is crucial to provide targets to the next generation of direct imaging facilities.
Aims. We present the analysis of the K-type star HD 176986. It has a brightness of V=8.45 mag and a distance from the Sun of d = 27.88 pc. This star hosts a known planetary system of two super-Earths. We utilize historical and recently collected RV measurements to investigate the presence of Earth- and super-Earth-like planets in the habitable zone of HD 176986.
Methods. We monitored the system with HARPS and HARPS-N. We joined historical datasets with new data collected in an ongoing blind search program. We took advantage of recently developed tools for RV extraction and stellar activity filtering. The analysis of activity indicators permits us to determine the period of the magnetic cycle of the star alongside its rotation period. We performed a joint analysis of RVs and activity indicators through multidimensional GPs to better constrain the activity model in RVs and avoid overfitting.
Results. We detected a new planet orbiting the star and retrieved the two known planets. HD 176986 b has an orbital period of 6.49164−0.00029+0.00030 d and a minimum mass of 5.36 ± 0.44 M⊕. HD 176986 c has an orbital period of Pc = 16.8124 ± 0.0015 d and a minimum mass of 9.75−0.64+0.65 M⊕. HD 176986 d has an orbital period of 61.376−0.049+0.051 d and a minimum mass of 6.76−0.92+0.91 M⊕. From the analysis of activity indicators, we find evidence of a magnetic cycle with a period of 2432−59+64 d, along with a rotation period of 36.05−0.71+0.67 d.
Conclusions. We discover a new planet in the multi-planet system orbiting the K-type star HD 176986. All the planets have minimum masses compatible with super-Earths or mini-Neptunes