Magnitude Of Flux Research Articles

Heat transfer in a wet porous moving inclined longitudinal fin exposed to convection and radiation in the presence of shape-dependent hybrid nanofluid: Adomian decomposition Sumudu transformation approach

This research paper investigates the thermal examination of a non-integer-ordered mobile fin situation with a hybrid nanofluid flowing past it at an unceasing speed U. The combination approach is utilized to evaluate the physical and thermal characteristics of the hybrid nanofluid, excluding the thermal conductivity and dynamic viscosity. This governing equation is transformed into a dimensionless form and the Adomian Decomposition Sumudu Transform method is employed to solve the conundrum of a moving fin immersed in a hybrid nanofluid. The reliability of this research has been confirmed by verifying the results through a comparison with numerical simulations. The influence of diverse factors on the thermal overview for varying noninteger values alpha is analyzed and presented in graphical representations. Moreover, the analysis reveals that the highest heat flux occurs in the scenario where nanoparticles with spherical-platelet shapes are combined. This is succeeded by the spherical-cylindrical combination, and finally, the spherical-spherical pairing, in terms of heat flux magnitude. Here, we discovered that the temperature at the fin tip decreases by 11.19141 % for s-s shaped nanoparticles, 10.45649 % for s-c shaped nanoparticles and 10.21162 % for s-p shaped nanoparticles as the wet parameter (m2) increases by a factor of 400, and also when the radiation parameter is increased by 400 %, the temperature of the fin tip drops by 13.11313 % for s-s shape nanoparticles, 11.97076 for s-c shape nanoparticles and 11.653899 % for s-p shape nanoparticles.

The directional unit hydrograph model: Connecting streamflow response to storm dynamics

Storm velocity (i.e., direction and speed) and structure (i.e., shape and intensity) play a critical role in streamflow response. These characteristics determine the timing and magnitude of precipitation fluxes across the watershed that drive runoff generation and conveyance along the river network. While previous efforts have used spatially explicit hydrologic models to assess the role of storm properties in streamflow magnitude, their computational demand significantly limits the range of scenarios that can be explored, hindering our ability to systematically identify critical conditions leading to extreme events. To address this technical gap, we introduce the Directional Unit Hydrograph (Directional-UH) model, a parsimonious approach based on the classic theory of the Unit Hydrograph. The Directional-UH extends the original theory by relaxing the assumption of spatial uniform rainfall and incorporating storm direction and speed into the unit hydrograph function. The model conceptualizes storms as rectangular structures with constant intensity moving along a linear trajectory with constant speed. We verify and validate our conceptualization by comparing with simulations, based on observations of extreme rainfall events, of the distributed hydrological model Hillslope-Link-Model (HLM) in the Turkey River basin in Iowa, USA. Then, the Turkey River basin is used as a testbed to illustrate three practical applications of the Directional-UH model. First, we identify the storm trajectory that produces the highest peak flow response. Second, we determine the storm characteristics that maximize the peak flow response by synchronizing storm motion and flood wave; we refer to this as the resonance condition. Third, we systematically explore the compounding effects of consecutive storm events with different trajectories to identify critical combinations that exacerbate the peak flow magnitude. The results on our testbed demonstrate that storm velocity has the potential to increase by a factor of two the peak flow magnitude when compared to stationary storm events. Overall, the parsimonious nature of the Directional-UH model offers a unique and valuable tool for modeling, predicting, and interpreting rainfall-runoff dynamics through the lens of storm direction, speed, and structure.

Atmospheric deposition of microplastics in Shiraz, Iran

The atmosphere plays a critical role in the regional and global transportation and redistribution of microplastics (MPs). However, the significance of rainfall and its means of scavenging MPs are not well understood. In this study, MP deposition was determined during successive dry and rainy events over eight consecutive days in the Shiraz region of Iran. Flux magnitudes and temporal distributions at six sites within and outside the city (including a remote, non-urbanised location) were similar and revealed a progressive increase in MP abundance and deposition during dry periods (up to about 50 MP m−2 h−1) and subsequent relatively rapid wet deposition (washout) by incipient rainfall (peaking at about 130 MP m−2 h−1). Wet deposition of MPs progressively decreased throughout the rainfall event, but with evidence of secondary peaks, before atmospheric accumulation and dry deposition increased during the next dry event and the cycle continued. Dry and wet deposition were dominated by fibres (that included polyester-polyethylene terephthalate, polystyrene, polyvinyl chloride and polyethylene) but the evolution of deposition did not appear to be associated with changes in MP size. These observations indicate that, as with other airborne pollutants, initial rainfall is an efficient scavenger of atmospheric MPs. Along with variations in methodology, this effect may contribute to the wide variation in MP fluxes reported in the literature.

Numerical Simulations of Internal Tide Dynamics in a Steep Submarine Canyon

Abstract This study investigates three-dimensional semidiurnal internal tide (IT) energetics in the vicinity of La Jolla Canyon, a steep shelf submarine canyon off the Southern California coast, with the Stanford Unstructured Nonhydrostatic Terrain-Following Adaptive Navier–Stokes Simulator (SUNTANS) numerical simulator. Numerical simulations show vertical structure and temporal phasing consistent with detailed field observations. ITs induce large (approximately 34 m from peak to peak) isotherm displacements and net onshore IT energy flux up to 200 W m−1. Although the net IT energy flux is onshore, the steep supercritical slope around the canyon results in strong reflection. The model provides the full life span of internal tides around the canyon, including internal tide generation, propagation, and dissipation. ITs propagate into the canyon from the south and are reflected back toward offshore from the canyon’s north side. In the inner part of the canyon, elevated mixing occurs in the middle layer due to an interaction between incident mode-1 ITs and reflected higher-mode ITs. The magnitude of IT flux, generation, and dissipation on the south side of the canyon are higher than those on the north side. An interference pattern in horizontal kinetic energy and available potential energy with a scale of approximately 20–50 km arises due to low-mode wave reflections. Our results provide new insight into IT dynamics associated with a small-scale canyon topography. Significance Statement Internal waves play an important role in ocean circulations and ecosystems. In particular, internal waves with frequencies of tides, known as internal tides, strongly enhance energy, heat, and mass transport in coastal oceans. This study presents internal tide dynamics in La Jolla Canyon, California, using a high-resolution numerical model. Model results show energy convergence in the canyon leading to internal tide energy dissipation and mixing. Some parts of internal tide energy reflect back offshore resulting in standing internal waves off California. This study provides new insights into internal tide dynamics and energy budgets in submarine canyons.

The Anthropogenic Salt Cycle.

Increasing salt production and use is shifting the natural balances of salt ions across Earth systems, causing interrelated effects across biophysical systems collectively known as freshwater salinization syndrome. In this Review, we conceptualize the natural salt cycle and synthesize increasing global trends of salt production and riverine salt concentrations and fluxes. The natural salt cycle is primarily driven by relatively slow geologic and hydrologic processes that bring different salts to the surface of the Earth. Anthropogenic activities have accelerated the processes, timescales and magnitudes of salt fluxes and altered their directionality, creating an anthropogenic salt cycle. Global salt production has increased rapidly over the past century for different salts, with approximately 300 Mt of NaCl produced per year. A salt budget for the USA suggests that salt fluxes in rivers can be within similar orders of magnitude as anthropogenic salt fluxes, and there can be substantial accumulation of salt in watersheds. Excess salt propagates along the anthropogenic salt cycle, causing freshwater salinization syndrome to extend beyond freshwater supplies and affect food and energy production, air quality, human health and infrastructure. There is a need to identify environmental limits and thresholds for salt ions and reduce salinization before planetary boundaries are exceeded, causing serious or irreversible damage across Earth systems.

Investigating mass transfer around spatially-decoupled electrolytic bubbles

Electrolytic bubbles have a profound impact on mass transport in the vicinity of electrodes and greatly influence the electrolyzer efficiency and cell overpotential. However, experimental measurements of concentration fields around electrolytic bubbles with high spatio-temporal resolution is challenging. In this study, a succession of spatially-decoupled electrolytic bubbles growing in an initially quiescent electrolyte is simulated. The bubbles grow and depart from a hydrophobic cavity at the center of a ring microelectrode. The gas-liquid interface is modeled using a moving mesh topology. A geometric cutting protocol is developed to handle topology changes during bubble departure. The simulated bubbles show good agreement with the bubble growth dynamics observed in experiments. The bubbles in this spatially-decoupled system outgrow the region of electrolyte that is saturated with dissolved hydrogen. This leaves the apex of the bubble interface exposed to an undersaturated region of the electrolyte which leads to an outward flux of hydrogen gas. This is shown to limit the gas evolution efficiency of bubbles even though that they grow at a constant volumetric rate. By analyzing the distribution of the flux of dissolved hydrogen along the bubble interface along with the development of dissolve hydrogen concentration profiles around the bubble, we show that the magnitude of the outward diffusive flux at the apex of the bubble decreases with increasing electrolysis current.

Numerical analysis on the direction of groundwater flux effects on the early post-injection migration of a CO2 plume

Several parameters have been analysed in the field of carbon dioxide (CO2) subsurface storage efficiency and security, including the aquifer dip and background water flow, for proper selection of CO2 storage aquifer sites. However, less importance has been assigned to the impact of the direction of groundwater flow on the migration of the injected CO2 plume, and hence the aquifer storage performance. This study investigates, using a numerical modelling method, the effect of the direction and magnitude of groundwater flux on the CO2 plume displacement and trapping in dipping aquifers during the early stages of the post-injection migration. The groundwater flow is established using water injection and production wells at the extremities of the model, while the direction of flow is altered from downdip to updip by swapping the locations of these wells. The study estimates and compares the extent of the total injected plume and the mobile portion of the plume, in addition to the instantaneous velocity of the leading tip of the plume, when groundwater flows downdip and when it flows updip. Our results indicate that when the groundwater flows downdip, counter to the overall direction of the CO2 plume migration, the plume is more stretched in both the updip and downdip directions than when groundwater flows updip. The size of mobile CO2 plume enlarges to a greater extent with downdip groundwater flow, causing the advancing tip to accelerate during its updip migration due to increasing buoyancy, with the effect being more pronounced at lower flow velocities. This increases the risk of CO2 leakage during the early stages of the plume migration when groundwater flows downdip. On the other hand, updip groundwater flow reduces the risk of leakage by reducing the velocity and extent of the plume, and increasing the impact of trapping mechanisms. Thus, the direction of groundwater flow can control the migration velocity of the CO2 plume in dipping storage aquifers, not due primarily to any induced viscous force, but due to the impact of trapping on buoyancy. Therefore, choosing the appropriate injection location for CO2 relative to the direction of flux is important for storage efficiency.

BioGeoChemical‐Argo Floats Reveal Stark Latitudinal Gradient in the Southern Ocean Deep Carbon Flux Driven by Phytoplankton Community Composition

AbstractThe gravitational sinking of particles in the mesopelagic layer (∼200–1,000 m) transfers to the deep ocean a part of atmospheric carbon fixed by phytoplankton. This process, called the gravitational pump, exerts an important control on atmospheric CO2 levels but remains poorly characterized given the limited spatio‐temporal coverage of ship‐based flux measurements. Here, we examined the gravitational pump with BioGeoChemical‐Argo floats in the Southern Ocean, a critically under‐sampled area. Using time‐series of bio‐optical measurements, we characterized the concentration of particles in the productive zone, their export and transfer efficiency in the underlying mesopelagic zone, and the magnitude of sinking flux at 1,000 m. We separated float observations into six environments delineated by latitudinal fronts, sea‐ice coverage, and natural iron fertilization. Results show a significant increase in the sinking‐particle flux at 1,000 m with increasing latitude, despite comparable particle concentrations in the productive layer. The variability in deep flux was driven by changes in the transfer efficiency of the flux, related to the composition of the phytoplanktonic community and the size of particles, with intense flux associated with the predominance of micro‐phytoplankton and large particles at the surface. We quantified the relationships between the nature of surface particles and the flux at 1,000 m and used these results to upscale our flux survey across the whole Southern Ocean using surface observations by floats and satellites. We then estimated the basin‐wide Spring‐Summer flux of sinking particles at 1,000 m over the Southern Ocean (0.054 ± 0.021 Pg C).

Analysis and Application of the Electromagnetic Wave Propagation, Fields, and Dispersion Relation in an Elliptical Chiro Plasma Waveguide Immersed in Magnetized Plasma

AbstractThis research proposes and investigates an elliptical waveguide filled with chiro plasma as its core and magnetized plasma as its clad region. The clad region is in the constant infinite magnetic field, and its direction is the same as the wave propagation in the chiro plasma elliptical waveguide. The electromagnetic wave propagation in the considered waveguide is studied. The expressions for electromagnetic field components in the chiro plasma core and magnetized plasma cladding are derived. The dispersion relations for the hybrid modes are calculated considering appropriate boundary conditions at the chiro plasma and magnetized plasma interface. The behavior of the energy flux and the dispersion curves are numerically and graphically studied. It is seen that the magnitude of the power density decreases with the increase of the cyclotron frequency and it increases with the increase of the plasma frequency and supports power flow in the backward direction for the considered mode. Furthermore, it is shown higher values of the chirality parameter cause the magnitude of the power flux to increase in the backward direction.

Remanent flux detection method for a protection current transformer based on fluxgate theory

Protection current transformer (CT) saturation caused by the remanent flux will affect the performance of protective relays. The saturation can be suppressed by demagnetizing the iron core. Detecting remanent flux can make demagnetization more effective. This paper proposes a remanent flux detection method based on the fluxgate theory, which can effectively measure the magnitude and polarity of the remanent flux using the second harmonic of the current generated by a single-phase electronic inverter. The proposed method can detect the remanent flux without changing it, no matter whether the CT is connected to the power system or not, which means that this method can measure the remanent flux when the CT is under normal operating conditions. The effectiveness of this method is verified in EMTP-RV software, and the simulation results show that this method can detect the remanent flux with high accuracy.

A Low-Cost Programmable Reversing Flow Column Apparatus for Investigating Mixing Zones.

This note describes the development and testing of a novel, programmable reversing flow 1D (R1D) experimental column apparatus designed to investigate reaction, sorption, and transport of solutes in aquifers within dynamic reversing flow zones where waters with different chemistries mix. The motivation for constructing this apparatus was to understand the roles of mixing and reaction on arsenic discharging through a tidally fluctuating riverbank. The apparatus can simulate complex transient flux schedules similar to natural flow regimes The apparatus uses an Arduino microcontroller to control flux magnitude through two peristaltic pumps. Solenoid valves control flow direction from two separate reservoirs. In-line probes continually measure effluent electrical conductance, pH, oxidation-reduction potential, and temperature. To understand how sensitive physical solute transport is to deviations from the real hydrograph of the tidally fluctuating river, two experiments were performed using: (1) a simpler constant magnitude, reversing flux direction schedule (RCF); and (2) a more environmentally relevant variable magnitude, reversing flux direction schedule (RVF). Wherein, flux magnitude was ramped up and down according to a sine wave. Modeled breakthrough curves of chloride yielded nearly identical dispersivities under both flow regimes. For the RVF experiment, Peclet numbers captured the transition between diffusion and dispersion dominated transport in the intertidal interval. Therefore, the apparatus accurately simulated conservative, environmentally relevant mixing under transient, variable flux flow regimes. Accurately generating variable flux reversing flow regimes is important to simulate the interaction between flow velocity and chemical reactions where Brownian diffusion of solutes to solid-phase reaction sites is kinetically limited.

Groundwater exfiltration pattern determination in the sub-arctic catchment using thermal imaging, stable water isotopes and fully-integrated groundwater-surface water modelling

Groundwater-surface water (GW-SW) interactions play an important function in northern catchments, but their dynamics and role in water, carbon, and nutrient balances are still poorly understood. In this case study, we (1) explored groundwater-surface water dynamics in a sub-arctic headwater watershed in Pallaslompolo, Finnish Lapland. (2) We compared fully-integrated physically-based simulations of the groundwater and surface water and their interactions with unique spatially distributed field datasets of drone-derived thermal infrared imaging (TIR) and surface peat pore stable water isotopes. Simulations and field observations point to similar GW-exfiltration areas, with an agreement between slightly over 50% for stable water isotopes and modeling and more than two thirds for thermal infrared and modeling. The agreement provides evidence that a fully-integrated GW-SW model with a simple parameterization approach can successfully identify the main features of GW-SW interactions in the high-latitude catchment. All methods suggest the complex nature of GW-SW exchange that is focused in topographical lowlands. Our simulation results also highlight how specific locations serve as groundwater exfiltration zones, surface water downwelling zones, or ‘mixed’ zones, where both interaction types occur at different times according to the hydrological state of the system. Modeling results suggest abrupt GW-SW interaction reversals – a phenomenon known to occur in peatland areas. To conclude, the three methods should be treated as complementary when describing and understanding GW-SW interactions within peatlands, but only the fully-integrated physically-based modeling can provide comprehensive estimates for both the spatial and temporal patterns and magnitudes of GW-SW interaction fluxes.

Analyzing the impact of various factors on leaf surface temperature based on a new tree-scale canopy energy balance model

Trees are one of the effective ways to regulate the microclimate, while the environmental parameters influence their transpiration rate. These complex processes manifest at the macro scale through leaf surface temperature (LST). Therefore, the key to studying the influence of trees on the microclimate is to calculate the LST. In this paper, we propose a new tree-scale canopy energy balance (CEB) model related to tree canopy height based on the big-leaf model to calculate the LST and analyze the influence of various factors on both LST and each sub-term of CEB. The results indicate that air temperature and solar radiation have a greater effect on LST than relative humidity on it. When the total solar radiation flux remains constant, air parameters primarily affect the latent heat flux of trees through the vapor pressure deficit between leaves and the air. The transpiration rate of trees is influenced not only by air parameters, but also by stomatal resistance. Solar radiation can directly determine the magnitude of the net radiation flux in the CEB, while its influence on latent heat flux is insignificant. Under high solar radiation flux conditions, an increase in wind speed can mitigate the rise of LST.

Reconstructing the ocean's mesopelagic zone carbon budget: sensitivity and estimation of parameters associated with prokaryotic remineralization

Abstract. Through the constant rain of sinking marine particles in the ocean, carbon (C) trapped within is exported into the water column and sequestered when reaching depths below the mesopelagic zone. Atmospheric CO2 levels are thereby strongly related to the magnitude of carbon export fluxes in the mesopelagic zone. Sinking particles represent the main source of carbon and energy for mesopelagic organisms, attenuating the C export flux along the water column. Attempts to quantify the amount of C exported versus C consumed by heterotrophic organisms have increased in recent decades. Yet, most of the conducted estimations have led to estimated C demands several times higher than the measured C export fluxes. The choice of parameters such as growth efficiencies or various conversion factors is known to greatly impact the resulting C budget. In parallel, field or experimental data are sorely lacking to obtain accurate values of these crucial overlooked parameters. In this study, we identify the most influential of these parameters and perform inversion of a mechanistic model. Further, we determine the optimal parameter values as the ones that best explain the observed prokaryotic respiration, prokaryotic production and zooplankton respiration. The consistency of the resulting C budget suggests that such budgets can be adequately balanced when using appropriate parameters.

Global termite methane emissions have been affected by climate and land-use changes

Termites with symbiotic methanogens are a known source of atmospheric methane (CH4), but large uncertainties remain regarding the flux magnitude. This study estimated global termite CH4 emissions using a framework similar to previous studies but with contemporary datasets and a biogeochemical model. The global termite emission in 2020 was estimated as 14.8 ± 6.7 Tg CH4 year−1, mainly from tropical and subtropical ecosystems, indicating a major natural source from upland regions. Uncertainties associated with estimation methods were assessed. The emission during the historical period 1901–2021 was estimated to have increased gradually (+ 0.7 Tg CH4 year−1) as a result of combined influences of elevated CO2 (via vegetation productivity), climatic warming, and land-use change. Future projections using climate and land-use scenarios (shared socioeconomic pathways [ssp] 126 and 585) also showed increasing trends (+ 0.5 to 5.9 Tg CH4 year−1 by 2100). These results suggest the importance of termite emissions in the global CH4 budget and, thus, in climatic prediction and mitigation.

Intermittency in turbulent emulsions

We investigate the statistics of turbulence in emulsions of two immiscible fluids of the same density. We compute velocity increments between points conditioned to be located in the same phase or in different phases, and examine their probability density functions (PDFs) and the associated structure functions (SFs). This enables us to demonstrate that the presence of the interface reduces the skewness of the PDF at small scales and therefore the magnitude of the energy flux towards the dissipative scales, which is quantified by the third-order SF. The analysis of the higher-order SFs shows that multiphase turbulence is more intermittent than single-phase turbulence. In particular, the local scaling exponents of the SFs display a saturation below the Kolmogorov–Hinze scale, which indicates the presence of large velocity gradients across the interface. Interestingly, the statistics of the velocity differences in the carrier phase recovers that of single-phase turbulence when the viscosity of the dispersed phase is high.

Model Predictive Current Control of an Induction Motor Considering Iron Core Losses and Saturation

The paper considers the model predictive current control (MPCC) of an induction motor (IM) drive and evaluates five IM models of different complexities—from conventional to magnetic saturation, iron losses, and stray-load losses—for the MPCC design. The validity of each considered IM model and the corresponding MPCC algorithm is evaluated by comparison of the following performance metrics: the total harmonic distortion of the stator current, the average switching frequency, the rotor flux magnitude error, the rotor flux angle error, and the product of the first two metrics. The metrics’ values are determined in wide ranges of the rotor speed (0.1–1 p.u.) and load torque (0–1 p.u.) through simulations performed in the MATLAB Simulink environment. The obtained results allow us to identify the IM model that offers the best tradeoff between the practicability and accuracy. Furthermore, a control effort penalization (CEP) is suggested to reduce the average switching frequency and, hence, the power converter losses. This involves constraining the simultaneous switching to a maximum of two branches of the three-phase power converter, as well as inclusion of the weighted switching penalization term in the cost function. Finally, the performance—both steady-state and dynamic—of the proposed MPCC system with CEP is compared with that of the analogous field-oriented controlled (FOC) IM drive. The inverter switching frequency is reduced more than twice by including the frequency-dependent iron-loss resistance in the MPCC. It is additionally reduced by implementing the proposed CEP strategy without sacrificing many other performance metrics, thus achieving a performance comparable to the FOC IM drive.

Experimental and computational study of convective heat fluxes in swirling two‐phase flows

AbstractThe convective mode of heat transfer is mainly due to the bulk motion of the fluid. Its turbulent nature and enhanced heat transfer coefficients have always attracted the academic, scientific community, and industrialists for many decades. The current research is based on the experimental and theoretical investigations on the turbulent convective heat transfer in swirling (60–300 rpm) steam (1–3 bars) injection into cocurrently flowing water. An exponential increase in the convective heat transfers up till the most swollen part of the swirling steam‐water volume of fluids has been observed. However, the convective heat transfer of the remaining part of the steam's plume shows an almost stagnant decreasing trend. The range of Rayleigh number that supports the transition in trends of the convective heat fluxes is 2.84 × 1011–3.71 × 1011. This transition affects the magnitude of the convective heat fluxes and the extent of the effective momentum fluxes, which is evident in the dominant role of the flow instabilities acting across the length of the steam's plume. Computational Fluid Dynamic analysis also has supported the exhibition of the heat fluxes magnitudes under the influence of the interacting Kelvin–Helmholtz instabilities and inertial instabilities across and along with the cocurrently acting shear layer.

Моделирование нисходящего переноса 210Pb на примере естественного торфяника Иласского болотного массива Европейской Субарктики России: модель IP-CRS

The paper presents the results of the modelling of the transport of 210Pb down the peat core for the Ilassky natural bog massif. The activities of radionuclides 210Pb and 137Cs were investigated in the core layer by layer. Due to the nonexponential decrease of 210Pb activity, significant errors are possible in determining the age and accumulation rates of peat when applying classical dating models. The article presents 210Pb dating data obtained using the IP-CRS model. Data analysis showed that the vertical distribution of 137Cs and 210Pb is related to peat parameters: ash content and bulk density. The 210Pb dating of the core showed an age of 1963 for a depth of 17—19 cm, which is consistent with the 137Cs data. The dating of this horizon is indirectly confirmed by the data of the ash content and bulk density of peat. The above mentioned confirms the correctness and adequacy of the chosen model of dating of the natural peat bog. The peak of anthropogenic radionuclide content in peat deposits corresponds to 1963, the date of signing the Partial Nuclear Test Ban Treaty, being a reference point for geochronological studies. The results of linear accumulation rate, peat deposit mass accumulation rate and the magnitude of the atmospheric flux of 210Pb presented in the study are in good agreement with the data on peatlands of Northern Europe and the European Subarctic of Russia.

Mach probe diagnostic for determining positive ion fluxes in H- ion sources

In NNBI ion sources neutral hydrogen atoms and positive ions impacton low work function grid surfaces where they are converted to negative ions, andsubsequently extracted. Knowledge of the positive ions flux iscrucial for optimizing the negative ion yield, and also for benchmarking numericalmodels. To this end a Mach probe (MP) diagnostic can be used, which determines thedirection and magnitude of the positive ion flux. The plasma in ion sources is typicallyweakly magnetized, rendering the interpretation of Mach probe data difficult. Forthis reason a two step approach is chosen, where at first a previously used Machprobe is re-commissioned and applied in a well diagnosed and versatile laboratoryscale experiment. From these experiments important insights regarding the designof a new combined Langmuir- and Mach probe, its calibration procedure, and datainterpretation are obtained.