Constant Flow Research Articles

Real-time prediction of heparin concentration in blood extracorporeal circulation by relaxation time distribution (RTD).

Heparin concentration c in a blood extracorporeal circulation has been real-timely predicted based on the relaxation strength Δεm at relaxation frequency fm extracted by relaxation time distribution (RTD). The simulated extracorporeal circulation was conducted to optimize the number of Δεm for the prediction of c using the porcine whole blood (WB) and low-leukocyte and -platelet blood (LLPB) under the condition of the gradual increment of c from 0 to 8 U/mL with constant flow rate and blood temperature. The experimental results show that among the three relaxation strengths Δε1, Δε2 and Δε3 (in ascending order of frequency), Δε2 at f2=5.2∼6.2MHz and Δε3 at f3=42∼50MHz were correlated to c. The Δε3 was decreasing with increasing c in both cases, which was influenced by the plasma macromolecular concentrations, while the Δε2 was increased with increasing c in WB case but was hardly changed in LLPB case because the Δε2 is influenced by the blood cell concentrations and the shape changes of blood cell membranes. Heparin concentration c is estimated by the linear regression formula cPRE=a1(Δε2-Δε2c=0)+a2(Δε3-Δε3c=0) (a1=-0.991, a2=-0.123) within the mean absolute percentage error (MAPE) of 0.291.

Enhanced removal of emerging recalcitrant pharmaceutical contaminants through integrated anaerobic and photocatalytic treatment

This study integrated anaerobic digestion (AD) and heterogenous photocatalysis, an advanced oxidation process (AOP), to treat tetracycline (TC), an emerging recalcitrant contaminant. The integrated system comprising an annular photocatalytic reactor and bioreactor was fed with simulated wastewater containing TC. The photocatalytic treatment was aided by a nano-engineered composite catalyst containing titanium dioxide (TiO2) and multi-wall carbon nanotubes (MWCNT). Heterogeneous photocatalysis as a single approach resulted in 90% TC degradation, 39% chemical oxygen demand (COD) reduction, 28% total organic carbon (TOC) removal, and minimal biochemical oxygen demand (BOD5) reduction. AD on its own removed 56% and 52%, respectively of the COD and BOD5. When applied as a pretreatment, heterogenous photocatalysis improved the biodegradability (BOD5/COD ratio) from 0.12 to 0.42 resulting in improved COD, BOD5, and TOC removals of 71%, 70%, and 76%, respectively in the ensuing AD process. Kinetic studies revealed that the ratio of the photocatalytic reactor unit to the anaerobic reactor unit for an integrated system with constant feed flow should be 12:1. Photodegradation as the only form of treatment used more energy than the integrated approach. The bioenergy generated by AD could supply the energy needs of the sequential system resulting in 20% energy savings and a carbon dioxide emission reduction (CER) of 22.74 kg for every cubic meter of treated wastewater. An integrated AOP-AD approach is thus promising for treating recalcitrant organic contaminants of emerging concern.

Synthesis of cubic-Li7La3Zr2O12 solid electrolyte for all-solid-state lithium-ion batteries via a combination process of induction thermal plasma and calcination

Abstract A combined process enabled the selective synthesis of cubic- and tetragonal-Li7La3Zr2O12 with calcination for nanoparticles synthesized by induction thermal plasma. The effect of O2 partial pressure was investigated by adjusting O2 content within a constant sheath gas flow for plasma-synthesized nanoparticles prepared for calcination. Low O2 partial pressure led to spherical nanoparticles from the liquid mixture via homogeneous nucleation of ZrO2, while high O2 partial pressure produced irregular, highly aggregated particles from a liquid-solid mixture with homogeneous nucleation of La2Zr2O7. The rapid quenching rate induced amorphous-Li7La3Zr2O12, and higher O2 promoted slight crystallization to cubic-Li7La3Zr2O12. This result includes potential for the facile production of ultra-thin cubic-Li7La3Zr2O12 films suitable for all-solid-state lithium batteries.

Effects of temperature on flame structures and local extinctions of swirl spray flames

The effects of air inlet temperature on the flame structures and the local extinctions of n-decane swirl spray flames at constant air flow velocity were clarified by using the simultaneous planar laser induced fluorescence measurements of OH and CH2O. Results show that the blowoff limit decreases 48% as the temperature increases from 298 to 473 K. The OH and the [CH2O] × [OH] overlap are mainly distributed near the shear layer, while a small amount of formaldehyde is also observed in the outer recirculation zone (ORZ), corresponding to the low-temperature reactions. The formaldehyde intensity in the ORZ varies non-monotonically with the temperature. The non-monotonic temperature dependence of the formaldehyde intensity is governed by the competition of the droplet evaporation rate and the initial droplet size. The local extinctions of swirl spray flames can be identified by the formation of holes or breaks in the OH branches together with the accumulation of formaldehyde. It suggests that the combination of OH and CH2O is a good indicator to predict the local extinctions. The probability of the local extinctions decreases gradually with the temperature. The locations of the local extinction move downstream from 333 to 423 K; however, the local extinctions occur frequently near the flame root at 473 K. It reveals that the local extinctions near the flame root are mainly associated with the cooling effect and the perturbation effect of the flame–droplet interactions at low temperature and at high temperature, respectively.

A Novel Microfluidic-Based Fluorescence Detection Method Reveals Heavy Atom Effects on Photophysics of Fluorophores With High Triplet Quantum Yield: A Numerical Simulation Study.

The present study introduces the idea of a novel fluorescence-based imaging technique combined with a microfluidic platform that enables a precise control of dark transient state populations of fluorescent probes flowing over a uniform, top flat supergaussian excitation field with a constant flow rate. To demonstrate the imaging capability of the proposed detection method, numerical simulations have been performed by considering laser, microscope and flow parameters of experimental setup together with photophysical model and electronic transition rates of fluorescent dyes. As an output data to be assessed, fluorescence image data is simulated numerically for bromine-free carboxyfluorescein and its brominated derivatives having different numbers of bromine atoms. Based on the magnitudes of applied excitation irradiances and flow rates, which can be manually controlled by user during experiments, the presence of dark state populations can appear as broadening, shifts and decays in normalized fluorescence intensity signals that are computed from simulated fluorescence images. As such changes in signals become more pronounced upon an increase in the degree of bromination, it is elicited that heavy atom effect can be resolved by properly tuning excitation powers of laser and flow rates. Proposed imaging method has potential to provide invaluable means to conventional fluorescence methods and can open up new perspectives in biomedical research.

Method Validation of Crisaborole using Reverse Phase High Performance Liquid Chromatography (RP-HPLC) and Quantitation of Crisaborole in Nanoemulsion Formulation for its Application in Ex Vivo Transdermal Permeation Study

Crisaborole is a boron containing phosphodiesterase 4 (PDE4) inhibitor which in this study was formulated in nanoemulsion form to treat atopic dermatitis. The study aims to develop and validate a selective analytical method for determining crisaborole in nanoemulsion formulations, facilitating its application in ex vivo transdermal permeation studies for the treatment of atopic dermatitis. Crisaborole was eluted using gradient elution method in reverse phase (C18) chromatography. The mobile phases were comprised of phosphate buffer (pH3) and acetonitrile, which increasing acetonitrile volume from 30 to 95 percent within 15 min with constant flow rate of 0.65 ml/min. Column temperature was set at 40 ºC and detection wavelength was at 252 nm. The method produced linear responses (R2=0.99) in concentrations ranges from 1.56-100 μg/ml (n=7). The developed method was sensitive with limit of detection (LOD) and limit of quantitation (LOQ) values of 1.84 μg/ml and 5.58 μg/ml; respectively. Crisaborole was stable in various working conditions which were within the acceptance value provided by guidelines (±15%). In ex vivo studies, the concentration of crisaborole was plotted in cumulative permeated graph and this quantitative method was proven to provide a selective and sensitive measurement for detection of crisaborole.

Survival of the heart in different cardioplegic solution delivery systems under extracorporeal normothermic perfusion conditions

Introduction: Preservation of isolated hearts in cardioplegic solution at normothermia is a promising strategy for increasing the organ lifespan. Further development of this strategy and search for new products for solution delivery can help optimize the technology of donor heart transportation. Objective: The study was aimed to test the efficacy of device for normothermic constant perfusion flow with innovative lines for the cardioplegic solution delivery (CardioSystemPharma, Khimki, Moscow Region, Russia) according to the Langendorff mode in comparison with a system based on nodes and tubes of Radnoti Langendorff Constant Perfusion Flow Apparatus (ADInstruments, Colorado Springs, USA) in a series of experiments on rat hearts.Methods: The innovative cardioplegic delivery system (CardioSystemPharma) and traditional perfusion system (Radnoti) were compared in experiments on rat hearts at normothermia without cardioplegic solution and using the cardioplegic solution Normacor (Mosfarm, Moscow Region, Russia). The time until complete cardiac arrest and the changes in the NADH coenzyme fluorescence were recorded. After cardiac arrest, immunohistochemical staining of ventricular sections was performed to detect myocardial injury during perfusion.Results: It was shown that the innovative cardioplegic delivery system was not inferior to the traditional perfusion system (Radnoti) and even surpassed it in terms of the time duration for preservation of the isolated heart. It was found that the using of elevated glucose concentration during normothermic perfusion could significantly increase the organ lifespan. The efficacy of normothermic perfusion in the experiment was confirmed by monitoring cellular respiration through recording the NADH fluorescence.Conclusion: Testing showed that long-term preservation under normothermia with usage of an innovative delivery system of Russian manufacture is a promising replacement for Radnoti solution delivery system. Received 16 October 2024. Revised 23 November 2024. Accepted 10 December 2024. FundingThe study was carried out within the framework of the project “Innovative cardioplegic lines for cardiac surgery” under the Agreement on the provision of a grant from the Government of the Moscow Region in the fields of science, technology, engineering and innovation No. 12/04-24 dated 04/27/2024. Conflict of interestThe authors declare no conflict of interest. Contribution of the authorsConception and study design: V.A. Tsvelaya, S.D. Robustova, V.S. Kachan, M.S. Nosov, A.K. Berezhnoy, V.A. Kozlov, K.I. AgladzeData collection and analysis: S.D. Robustova, V.S. Kachan, D.V. Kononova, A.S. Yarovoy, M.A. Gusev, V.V. Litvinenko, V.D. Dzhabrailov, A.A. Brichagina, Z.V. Obrazumova, S.D. Chekalina, S.S. Bakumenko, E.A. Turchaninova, V.A. TsvelayaStatistic analysis: S.D. Robustova, V.S. Kachan, D.V. Kononova, A.S. Yarovoy, M.A. Gusev, V.V. Litvinenko, V.D. Dzhabrailov, A.A. Brichagina, Z.V. Obrazumova, S.D. Chekalina, S.S. Bakumenko, E.A. TurchaninovaDrafting the article: S.D. Robustova, V.S. Kachan, D.V. Kononova, Z.V. Obrazumova, E.A. Turchaninova, V.A. TsvelayaCritical revision of the article: S.D. Robustova, E.A. Turchaninova, V.A. Tsvelaya, K.I. AgladzeFinal approval of the version to be published: S.D. Robustova, V.S. Kachan, D.V. Kononova, A.S. Yarovoy, M.A. Gusev, V.V. Litvinenko, V.D. Dzhabrailov, A.A. Brichagina, Z.V. Obrazumova, S.D. Chekalina, E.A. Turchaninova, S.S. Bakumenko, M.S. Nosov, A.K. Berezhnoy, V.A. Kozlov, V.A. Tsvelaya, K.I. Agladze

The Mediating Role of Digital Literacy between Lifelong Learning Tendency and 21st Century Skills

The rapid growth of technology accompanied new requirements in all aspects of life. The constant flow of information and the irresistible rise of technology gave rise to 21st-century skills, digital literacy, and lifelong learning concepts which are all in the spotlight of several organizations, policymakers, and researchers. Due to the increasing accessibility of technology, people, each day, feel the need to adapt to this new pace of life. Thus, teachers not only should be aware of their students’ needs but also be equipped with the qualifications the current age entails. With this in mind, in this paper, the researchers studied the mediating role of digital literacy between teachers' lifelong learning tendency and their 21st-century skills. The sample consists of 273 randomly selected teachers. The researchers used three different multifactor data collection tools. In addition to the acceptable validity and reliability results, the findings indicate varying degrees of positive correlations among the factors of the data collection tools. The outputs also indicate that participants’ lifelong learning tendencies were at a low, but digital literacy and 21st-century skills were at a medium level. Moreover, while lifelong learning tendency directly affects 21st-century skills, ethics and responsibility act as a mediator between lifelong learning tendency and 21st-century skills.

Shear stress-induced restoration of pulmonary microvascular endothelial barrier function following ischaemia reperfusion injury requires VEGFR2 signalling.

Normal shear stress produced by blood flow is sensed by the vascular endothelium and required for maintenance of the homeostatic functions of the endothelium in systemic conduit and resistance vessels. Many critical illnesses are characterised by periods of abnormally reduced or absent shear stress in the lung (e.g. haemorrhagic shock, embolism, ischaemia reperfusion injury and lung transplantation) and are complicated by pulmonary oedema following reperfusion due to microvascular leak. The role of shear stress in regulating the pulmonary microvascular endothelial barrier in the intact vascular bed has not been previously examined. We tested the hypothesis that, in lungs injured by a period of ischaemia and reperfusion (IRI), reduced shear stress contributes to increased pulmonary microvascular endothelial barrier permeability and oedema formation. Furthermore, we examined the role of VEGFR2 as a mechanosensor mediating the endothelial response to this altered shear stress. Following IRI, we perfused isolated ventilated mouse lungs with a low viscosity solution (LVS) or a higher, physiological viscosity solution (PVS) at constant flow to produce differing endothelial shear stresses in of the intact microcirculation. Lungs perfused with LVS developed pulmonary oedema due to increased endothelial permeability whereas those perfused with PVS were protected from oedema formation by reduced endothelial permeability. This effect of PVS required normal VEGFR2 mechanoreceptor function. These data show for the first time that shear stress has an important role in restoring endothelial barrier function in the intact pulmonary microcirculation following injury and have important implications for the treatment of pulmonary oedema in critically ill patients.

Model predictive control for hydrogen fuel cell–driven multi-level permanent magnet synchronous motor drive

ABSTRACT This paper proposes a Model Predictive Control (MPC) strategy for a three-level Permanent Magnet Synchronous Motor (PMSM) drive powered by a Hydrogen Fuel Cell (HFC). The integration of HFC with electric propulsion systems offers a promising avenue for sustainable transportation characterized by high efficiency and low environmental impact. The MPC algorithm optimally manages the power flow between HFC and PMSM drive by predicting future events, with consideration of dynamic interactions and constraints in the system. The proposed MPC strategy was validated through simulation results, which showed a reduction in hydrogen consumption up to 10 liters per minute (lpm) when operating at low speeds, compared to the constant flow of 60 lpm at full power. The system also achieved a nominal motor speed of 1483 rpm at 100 lpm of hydrogen flow, however considering the availability of Oxygen (21%) in the air 50–70 lpm of hydrogen flow will be the optimal. The findings highlight the effectiveness of the MPC approach, resulting in an increase in the HFC stack efficiency under varying motor speed conditions. This research underscores the potential of integrating HFC with three-level PMSM drives, offering a sustainable solution for advanced electric propulsion systems with enhanced energy efficiency and environmental sustainability.

Queen bee egg-laying dynamics: evaluation of Roger-Delon and Warre hives

The aim of the present study is to evaluate the egg-laying dynamics of queen bees in Roger-Delon and Warre hives located in an apiary at an altitude of less than 1000 m. The study was conducted during the active season of 2023, in an apiary located at an altitude of 860 m in south-western Bulgaria, Pernik district. The bee colonies were balanced before the beginning of the experiment. Two groups of 6 colonies were formed from each Roger-Delon and Warre system. Sealed worker brood was measured until the appearance of constant nectar flow (April – June), and after the appearance of constant nectar flow (September – November). There is currently a need to examine and quantify the egg-laying dynamics of queens in new hive systems. Queen egg-laying activity is affected by a variety of seasonal, nutritional and social factors. According to the results obtained, the average sealed worker brood in Warre hives and Roger-Delon hives are 10484±1031 cm2 and 9564±1057 cm2 (mean±SD) respectively, for the whole period until appearance of constant nectar flow.

Keheningan menurut Henri Nouwen dalam Dunia Modern

This study focuses on understanding the concept of silence according to Henri Nouwen and its relevance to spiritual life in the modern era. The research aims to explore Nouwen's idea of silence, which is often equated with solitude or loneliness. However, silence is a distinct concept that plays a crucial role in fostering spiritual growth. In contemporary times, we are inundated with a constant flow of information through digital devices and media platforms, a hallmark of the modern age. Consequently, we often find ourselves too busy and struggle to carve out moments of stillness and tranquility. Such conditions, sooner or later, can hinder the development of spiritual life. This paper examines the relevance of silence in the modern world and provides practical ways to integrate it into daily life. The methodology employed is a literature review, analyzing Nouwen's writings and other relevant sources from books and journals on modern life. The findings reveal that silence is essential and can be meaningfully practiced in today's modern context.

Penetration Grouting Mechanism of Bingham Fluid in Porous Media Based on Fractal Theory

Penetration grouting is a significant grouting technique. The pore structure has important impacts on the infiltration mechanism of slurry in porous media. In this study, based on fractal theory, a theoretical penetration grouting model for Bingham fluid is established. An experimental apparatus for simulating the penetration process of Bingham fluid with a constant flow rate is developed. A series of penetration-grouting experiments are conducted to validate the theoretical model established in this study and analyze the impacts of the water–cement ratio and flow rate on the slurry injection pressure. The results show that the theoretical values of the slurry pressure along the penetration direction obtained from the penetration grouting model match the experimental values well. This indicates that the proposed model can better describe the process of slurry infiltration and provide valuable support for related grouting projects.

Experimental evidence on the impact of climate-induced hydrological and thermal variations on glacier-fed stream biofilms.

Climate change is predicted to alter the hydrological and thermal regimes of high-mountain streams, particularly glacier-fed streams. However, relatively little is known about how these environmental changes impact the microbial communities in glacier-fed streams. Here, we operated streamside flume mesocosms in the Swiss Alps, where benthic biofilms were grown under treatments simulating climate change. Treatments comprised four flow (natural, intermittent, stochastic, and constant) and two temperature (ambient streamwater and warming of +2 °C) regimes. We monitored microbial biomass, diversity, community composition, and metabolic diversity in biofilms over three months. We found that community composition was largely influenced by successional dynamics independent of the treatments. While stochastic and constant flow regimes did not significantly affect community composition, droughts altered their composition in the intermittent regime, favouring drought-adapted bacteria and decreasing algal biomass. Concomitantly, warming decreased algal biomass and the abundance of some typical glacier-fed stream bacteria and eukaryotes, and stimulated heterotrophic metabolism overall. Our study provides experimental evidence toward potential and hitherto poorly considered impacts of climate change on benthic biofilms in glacier-fed streams.

Carbon-capture potential of industrial by-products for post-carbon society

To contribute to the realization of carbon neutrality by 2050, the authors have focused on the fact that some of the by-products of social activities have the ability to fix carbon dioxide, and have envisioned the creation of a carbon-capture urban environment using these materials. Also, the authors have emphasized carbon capture capabilities of industrial waste disposal facilities named as “Disposal Facility CCS”, since these are where substances containing large amounts of free calcium accumulate. As described herein, the authors have emphasized several kinds of by-product as carbon capture materials, and propose datasets of these carbon capture capabilities by measurement using constant flow aeration type CO2 fixation testing, which we developed. Furthermore, using these datasets, the authors estimate the potential carbon capture capability of a specific industrial waste disposal facility as an example of “Disposal Facility CCS”, and demonstrate its relative effectiveness compared to that of forests. Furthermore, the authors estimate the carbon capture potentials of industrial by-products generated in Japan as some examples. Consequently, this study proposed carbon capture future society concept using CO2 fixation materials on the basis of the estimation results conducted in this study.

Comparisons of atomic layer etching of silicon in Cl2 and HBr-containing plasmas

This paper reports an experimental investigation of Cl2 versus HBr for plasma atomic layer etching of silicon. An inductively coupled plasma (ICP) source with a constant flow of Ar carrier gases and HBr or Cl2 as a dosing gas was used for etching Si (100). Two modes of dosing were investigated: plasma gas dosing, in which pulsed flows of Cl2 or HBr are partially dissociated with the ICP with no substrate bias, and gas dosing, where the ICP is off during the dosing step. Following either dosing mode, a purge step of up to 5 s is followed by a 1 s period of ICP and substrate bias power, leading to etching of the halogenated surface layer. Optical emission spectroscopy was used to follow relative yields of SiCl, SiCl2, and SiBr, and scanning electron microscopy and profilometry were used to measure etching rates. Plasma gas dosing resulted in etching rates three to four times higher than gas dosing. Small differences were found between the two etchant feed gases, with Cl2 exhibiting about 3%–15% higher etching rate. Etched profiles for HBr plasma gas dosing produced little or no microtrench adjacent to the SiO2-masked line, while HBr gas dosing or Cl2 with either mode of dosing produced microtrenches at the bottom of the Si sidewall.

Determination of Pressure Jump Dependence and Time Constants of Hydraulic Pumps with Constant Pressure and Variable Flow

Simulations of the pump response time refer to the determination of the time constant of the transient process when the flow and pressure change. The changes mentioned in the standards are precisely defined and prescribed by the “MIL-P-19692E” norms. The simulation showed that the time constants are within the permissible limits prescribed by these norms. The diagram shows the responses for the considered pump and for the case when the flow changes from Qn to Qmin and changes from Qmin to Qn. The time constants t1 and t2 are defined on the diagrams, with the parameters that the pump has. In addition, the standards define the pressure jump that occurs during the transient process as well as time constants. From the flow change diagram, it can be seen that the flow change is also very fast and takes place in time intervals shorter than 0.1 s. By evaluating the size of the time constants, t1 and t2, it can be concluded that they have a value below 0.05 s, which meets the regulations in that area. Also, the size of the jump pressure meets the regulations because it is only 1.2 M Pa above the nominal pressure.

Numerical Analysis of Enhanced Forced Convection in Perforated Surface Wavy Plate-Fin Core

Abstract Steady, periodically fully developed forced convection through three-dimensional perforated sinusoidal wavy-fin cores with uniform wall temperature is computationally investigated. Constant property air flow (Pr ≈ 0.71) with a Reynolds number range of 50 – 4000 covering both laminar and turbulent regimes is considered. The computational solutions, validated with in-house experimental data for continuous and perforated wavy-fin coupons, highlight the effects of perforation locations (characterized by phase angle β), fin porosity, inter-fin spacing, and corrugation amplitude on the thermal-hydraulic performance of the fins. The local temperature, velocity, and pressure variations, and the corresponding local heat transfer coefficient and friction drag (or the Fanning friction factor f and Colburn factor j) are reported. Fluid flows from the adjacent channels through wavy-surface perforations induce secondary flow and interrupt the boundary layer leading to an increase in f and j in both laminar and turbulent regimes. Decrease in corrugation amplitude and inter-fin spacing leads to the suppression of recirculation zones, whereas higher porosity yields increased f and j. Perforated fins nevertheless require less surface area to fulfill a specified heat load condition with a fixed pressure drop as compared to the continuous wavy fins. Furthermore, the perforation location has a noticeable effect on the local heat transfer and flow dynamics and, except for Re <∼200, wavy fins with perforations at relatively higher phase angle β perform better.

Convective Drying with the Application of Ultrasonic Pre-Treatment: The Effect of Applied Conditions on the Selected Properties of Dried Apples.

The aim of this study was to evaluate the effect of ultrasound used as a preliminary treatment and drying temperature on the properties of dried apples (var. Golden Delicious). The aim of the work was also to optimise the process in terms of reducing the drying time and obtaining a product with specific properties. The apple tissue was sonicated for various times from 30 to 60 min. Then, the tissue was air-dried with a constant air flow of 55 to 85 °C. The work determined the dry substance content, water activity, colour parameters, content, antioxidant activity, and hygroscopicity of the dried material. The drying kinetics were also analysed. The results showed that the decrease in sonification time increased the dry matter content and reduced water activity. Also, the decrease in drying temperature caused a smaller intake of water and led to a lower hygroscopicity of dried apples. The selected parameters of the process had a positive effect on the preservation of bioactive compounds and led to an increase in antioxidant activity. Experimental results were adapted by a second-order polynomial model, where analysis of variance was utilized to define optimal drying conditions. Therefore, considering the shortest drying time, the lowest colour difference, ΔE, and the highest antioxidant activity, the best condition for the drying of apple tissue can be obtained with the application of 30 min of samples sonication and drying of apples at a temperature of 80.9 °C.

Darcy–Forchheimer gravity currents in porous media

We theoretically and experimentally study gravity currents of a Newtonian fluid advancing in a two-dimensional, infinite and saturated porous domain over a horizontal impermeable bed. The driving force is due to the density difference between the denser flowing fluid and the lighter, immobile ambient fluid. The current is taken to be in the Darcy–Forchheimer regime, where a term quadratic in the seepage velocity accounts for inertial contributions to the resistance. The volume of fluid of the current varies as a function of time as $\sim T^{\gamma }$ , where the exponent parameterizes the case of constant volume subject to dam break ( $\gamma =0$ ), of constant ( $\gamma =1$ ), waning ( $\gamma <1$ ) and waxing inflow rate ( $\gamma >1$ ). The nonlinear governing equations, developed within the lubrication theory, admit self-similar solutions for some combinations of the parameters involved and for two limiting conditions of low and high local Forchheimer number, a dimensionless quantity involving the local slope of the current profile. Another parameter $N$ expresses the relative importance of the nonlinear term in Darcy–Forchheimer's law; values of $N$ in practical applications may vary in a large interval around unity, e.g. $N\in [10^{-5},10^{2}]$ ; in our experiments, $N\in [2.8,64]$ . Sixteen experiments with three different grain sizes of the porous medium and different inflow rates corroborate the theory: the experimental nose speed and current profiles are in good agreement with the theory. Moreover, the asymptotic behaviour of the self-similar solutions is in excellent agreement with the numerical results of the direct integration of the full problem, confirming the validity of a relatively simple one-dimensional model.