Transient Behavior Research Articles

Dynamic Pressure Analysis of Shale Gas Wells Considering Three-Dimensional Distribution and Properties of the Hydraulic Fracture Network

A major challenge in transient pressure analysis for shale gas wells is their complex transient flow behavior and fracturing parameters. While numerical simulations offer high accuracy, analytical models are attractive for transient pressure analysis due to their high computational efficiency and broad applicability. However, traditional analytical models are often oversimplified, making it difficult to capture the complex seepage system, and three-dimensional fracture characteristics are seldom considered. To address these limitations, this study presents a comprehensive hybrid model that characterizes the transient flow behavior and analyzes the pressure response of a fractured shale gas well with a three-dimensional discrete fracture. To achieve this, the hydraulic fracture is discretized into several panels, and the transient flow equation is numerically solved using the finite difference method. Based on the Langmuir adsorption isotherm and the pseudo-steady diffusion in matrix and Darcy flow in the network of micro-fractures, a reservoir model is established, and the Laplace transformation is adopted to solve the model analytically. The transient responses are obtained by dynamically coupling the flow in the reservoir and the discrete fracture. The precision of the proposed model is validated using the commercial numerical simulator, Eclipse. A series of transient pressure dynamic curves are drawn to make a precise observation of different flow regimes, and the effects of several parameters on transient pressure response are also examined. The results show that the shale gas well testing interpretation curves comprise nine flow stages. The pressure drop of shale gas reservoirs is lower than that of conventional gas reservoirs due to the replenishment of desorbed gas. The artificial fracture flow capacity, fracture length, and height are the main engineering factors affecting the pressure responses of shale gas wells. Maximizing the degree and scope of reconstruction can enhance the gas well production capacity during fracturing construction. The research results also indicate that our model is a reliable semi-analytical model for well test interpretations in real case studies.

Repeat Fire Tests of Upholstered Furniture: Variability and Experimental Observations

A series of trials were conducted to investigate the repeatability of furniture-scale calorimetry experiments. Twenty-five identical upholstered chairs were ignited under the same experimental conditions. Experimental results of heat release rate (HRR), mass loss rate (MLR), and emission yields (CO, CO2, N2O, NO, CH4, HCN) are presented. Discrepancies were observed between the time resolved evolution of the various recorded data. However the development of each fire was observed to be tied to common events. By accounting for these events, a more consistent representation of the burning behaviour can be expressed. Each experiment displayed distinct burning regimes (i.e., pyrolysis, flaming, and smouldering) which were identified through visual observation and through analysing the emission data. Some species yields were found to be approximately constant over some burning regimes (e.g., CO2 yield over the flaming regime) while others displayed highly transient behaviour (e.g., CO yield was found to be burning regime dependent). Results from upholstered furniture scale experiments, including HRR and emission yields, are commonly used in various engineering applications; this study lends insight into the variability that can be observed for such data and the implications in applying this data in further analysis.

Investigating the transient electrical behaviors in PEM fuel cells under various platinum distributions within cathode catalyst layers

The spatial distribution of platinum (Pt) within the cathode catalyst layer (CCL) is vital for the electrochemical reactions and mass transport in fuel cells. Though important, the transient effects of these distributions are seldom explored. This study examines the impact of Pt distribution on transient electrical behaviors, including voltage and local current distribution (LCD) uniformity, using a transient, two-dimensional, two-phase, non-isothermal fuel cell model that incorporates catalyst agglomerate. Three Pt distribution types are investigated: uniform, MPL-side biased, and PEM-side biased. Results indicate a voltage undershoot occurs during current loading. Compared to the homogeneous CCL, PEM-side bias reduces this undershoot by 12.5% due to shortened proton transfer paths and decreased ohmic loss, while MPL-side bias increases it by 18.8% due to the inverse effect. Additionally, Pt distribution affects both oxygen transport and reaction resistance within the agglomerate, influencing LCD uniformity. Under loading conditions, gradient CCLs show inferior LCD uniformity than homogeneous ones. Peak non-uniformity values of 0.22, 0.59, and 0.71 are observed for homogeneous, MPL-biased, and PEM-biased CCLs, respectively. From the perspective of voltage and LCD uniformity, the MPL-side biased CCL is not found to enhance dynamic characteristics, whereas the PEM-side bias improves voltage undershoot but at the cost of LCD uniformity. This study provides a novel perspective on fuel cell dynamics, emphasizing the transient effects of Pt distribution and their potential for optimizing dynamic performance by adjusting the Pt gradient.

Balancing: A solution to our distorted indices of transient dynamics

AbstractBecause populations are at the mercy of random disturbances large and small, they rarely, if ever, converge on predicted long‐term behaviors. Therefore, when employing matrix population models, ecologists study the dynamics of populations that depart from stable distributions. Necessary for such studies are indices of transient dynamics that measure the size of short‐term population fluctuations. These indices advance our understanding of population dynamics by revealing that population growth rate in a single timestep can far exceed the stable population growth rate. Despite their value, indices of transient behavior possess two major shortcomings: they are scale dependent and easily distorted by outsized population classes. Distortion occurs whenever immature classes, due to their sheer size, carry greater weight in the calculation of population size than mature classes. Beluga sturgeon (Huso huso), for example, have an immature age class (eggs) that is several orders of magnitude larger than its mature age classes. To remove the undue influence of outsized classes, I use balancing, which rescales classes by the stable population distribution and makes the indices of transient dynamics scale invariant. I apply balancing to 1800 population projection matrices for various species across the Animal Kingdom, using reactivity and the Henrici metric of non‐normality as indices of transient dynamics. I found that balancing profoundly changes the picture of which populations have the greatest or least potential transient dynamics. Using a population projection matrix for northern pike (Esox lucius), I demonstrate how balancing influences pseudospectra contour plots that are used to infer transient dynamics.

Transient behavior of liquid film deposition and surface heat transfer upon cryogen-spray cooling coupled with cold air jet

Cryogen spray cooling (CSC) has become a promising auxiliary-cooling technique for laser dermatology, which recently enhanced by cold air jet (CSC-CAJ). However, the CAJ-to-spray interactions could worsen the CSC performance and associated liquid film behavior. In this study, the transient behavior of liquid film deposition and surface heat transfer of CSC-CAJ was investigated. A high-speed camera was used to capture the film intensity through Mie-scattering technique. Fast-response TFTC thermocouple was used to measure the transient surface temperature. The large eddy simulation (LES) was used to extract the vortical structure, while the discrete-phase model (DPM) and Eulerian wall film (EWF) were coupled for the spray process and the transient film modeling. The results showed that the CAJ significantly enhanced CAJ-to-spray mixing and mitigated the film thickness (i.e., 32 % reduction). The CSC-CAJ had asymmetric film coverage due to induced counter-rotating vortex-pairs (CRVP) from the CAJ-to-spray interaction, which laterally clustered the spray. It permitted fast evaporation with dominant CAJ at the spray-periphery while permitting fast evaporation with dominant spray at the spray-core. Consequently, the CSC-CAJ showed 75 % temperature increment at the windward side and 15 % temperature reduction with 60 % heat transfer coefficient enhancement at the impingement point. The experimental film intensity and simulated film thickness were linearly correlated and significantly influenced the surface temperature. The combined results affirmed the significant impact of the CAJ on the transient film deposition, which potentially helps promote advanced cooling technology.

Experimental investigation and phenomenological modeling of fatigue crack growth in X80 pipeline steel under random loading

Ocean structures are subjected to random environmental loads during their service life. Under the action of random loads, fatigue crack growth within pipeline steel exhibits transient behaviors such as retardation or acceleration. This poses significant challenges in predicting the fatigue life of ocean structures under random loadings. To establish a predictive model for fatigue crack growth in X80 pipeline steel under random loadings, this study first conducts fatigue crack growth experiments under constant amplitude and random loading conditions. Then, based on deep learning methods and the fracture yield zone theory, a phenomenological model is developed to predict fatigue crack growth in X80 pipeline steel under random loading conditions. The results show that under random loading conditions, the fatigue crack growth curve of X80 pipeline steel maintains a relatively clear logarithmic-linear feature during the stable crack growth stage. However, due to the continuous variation of stress ratio with loading sequence, the fatigue crack growth curve exhibits strong fluctuation characteristics; The phenomenological model established in this study for predicting fatigue crack growth under random loading conditions can relatively accurately reflect the overall trend of fatigue crack growth under random loadings, with a maximum prediction error of less than 10%.

Terahertz-induced second harmonic radiation from transient electron behavior in water

Laser-induced liquid plasma is expected to be an efficient medium for a new generation of terahertz (THz) devices. However, the mechanism of interaction between liquid plasma and THz waves is currently unclear. Here, we observed two phenomena related to THz wave interaction with water plasma: THz-induced second harmonic (TISH) radiation in water plasma and THz absorption by water plasma. We established an internal relationship between these two macroscopic phenomena by utilizing a photocurrent model and the Drude model. Using liquid water and air as examples, a scheme is proposed to analyze the photonic characteristics of plasma in different physical states. This study offers an experimental basis for predicting the TISH phenomenon across various substances and states and also provides the theoretical support for the practical implementation of liquid-based detection of THz waves.

Spotted Hyena Optimizer enhances the performance of Fractional-Order PD controller for Tri-copter drone

AbstractIn this study, nonlinear control design is presented for trajectory tracking of Tricopter system. A Fractional Order Proportional Derivative (FOPD) controller has been developed. The performance of controlled Tri-copter system can be enhanced by suggesting modern optimization technique to optimally tune the design parameters of FOPD controller. The Spotted Hyena Optimizer (SHO) is proposed as an optimization method for optimal tuning of FOPD's parameters. To verify the performance of controlled Tricopter system based on optimal SHO-based FOPD controller, computer simulation is implemented via MATLAB codes. Moreover, a comparison study between SHO and Particle Swarm Optimization (PSO) has been made in terms of robustness and transient behavior characteristics of FOPD controller.

A comprehensive experimental study of cooling photovoltaic panels using phase change materials under free and forced convection – Experiments and transient analysis

Solar radiation is captured by photovoltaic (PV) panels, which use it to create electricity. However, an overabundance of photons striking the PV's surface raises its temperature, which lowers its efficiency. These days, cooling solar panels is very important, and research on these methods is widely available in the literature. Thus, the study field's problems truly lie in developing new or improved methods for doing the same tasks. The goal of this work is to further boost the efficiency of photovoltaic (PV) panels beyond what can be achieved with PCM and free/forced convection alone. To do this, phase change materials (PCM) are cooled using both free and forced convection. In accordance with the latitude of Lebanon's Bekaa Valley, four cooling techniques are experimentally investigated. A photovoltaic panel using phase-change material (PCM) with copper and aluminum wires in a 70 %–20 %–10 % mass ratio (CPCM-PV), respectively, is the first cooling method. In the second approach, four 5 cm long fins are fixed under free convection using the same combination of aluminum fins inside the PCM container while preserving the same ratio (IEF-PCM-Free-PV). The third technique is the same as the second but with forced convection (IEF-PCM-Forced-PV), while the fourth technique uses an aluminum finned plate with 16 finned plates under forced convection (F-Forced-PV). IEF-PCM-Forced-PV showed the most relative increases in efficiency rate of energy dissipated of 20.36 % and 62.24 %, respectively, as compared to the regular PV panel, according to the results. F-Forced-PV, IEF-PCM-Free-PV, and CPCM-PV showed an increase in relative efficiency of 16.87 %, 6.3 %, and 3.9 % respectively, and correspondingly, these enhancements were accompanied by an increase in energy dissipation of 55.80 %, 44.85 %, and 41.18 % for each system. Economically, the IEF-PCM-Forced-PV had the highest total yearly savings of $17.87 with a payback period of 1.9 years. An appropriate transient energy balance is conducted and permitted to demonstrate clearly the transient behavior of the system under the various cooling techniques. Finally, the percentage of enhancement using the newly suggested composite PCM with internal and external fins under forced convection is compared to the enhancement found in the literature for various classical techniques and shows greater potential for further enhancement of the PV performance.

Investigation of the Influence of Contact Patterns of Worm-Gear Sets on Friction Heat Generation during Meshing

Friction losses and scuffing failures are interesting research topics for worm gears. One of the factors leading to scuffing is the heat generated in the contact of gear teeth. The contact geometry of worm gears is complex, leading to high friction between contact surfaces. High friction between contact surfaces during operation generates heat friction that causes the occurrence of scuffing, which in turn determines the scuffing load capacity. To analyse the thermal characteristics of a worm-gear pair and the thermal behaviour of contact teeth, a direct-coupled thermal–structural 3D finite element model was applied. The heat flux due to friction-generated heat was determined on the gear tooth to investigate thermal characteristics and predict transient temperature fields. This study permits an in-depth understanding of the temperature fields and the friction heat generation process. Also, better control of the contact pattern between worm-gear teeth would decrease friction heat and increase scuffing load capacity. This paper investigates the transient thermal behaviour among different pinion machine setting parameters that can result in an optimal tooth-contact pattern that produces a lower temperature field, thus achieving higher transmission efficiency.

Design and FPGA implementation of a hyperchaotic conservative circuit with initial offset-boosting and transient transition behavior based on memcapacitor

A charge-controlled memcapacitive conservative chaotic circuit with trigonometric function terms is constructed in this paper. By analyzing the characteristics of the infinite equilibrium point and the divergence of the system, it is proved that the system is conservative. Under the influence of system parameters, hyperchaotic and chaotic characteristics can be switched to each other. With the increase of parameters and initial values, the Lyapunov exponent is also greatly improved. In addition, the transient chaos phenomenon accompanied by the internal crisis is also found, which leads to the sudden change of the orbit state of the attractor, and different types of coexisting attractors in different regions of the basins are also found. Through further analysis of the phase diagram, bifurcation diagram and time-domain waveform, it is found that there are three initial offset-boosting behaviors with different characteristics in the system. Finally, the spectral entropy (SE) algorithm is used to compare the memcapacitive circuit complexity under different initial conditions and system parameters. We find that the SE complexity distribution map is consistent with the Lyapunov exponent trajectory, which further reflects the influence of system parameters and initial conditions on the dynamic characteristics of the system. On the platform of Cyclone IV E series, the FPGA main chip of EP4CE10F17C8N is used to complete the hardware implementation of the system. The FPGA implementation results are consistent with numerical simulation, and verify the realistic feasibility of the memcapacitive conservative chaotic circuit in practical application.

Study on the effect of particle morphology on transient dispersion behavior and ignition of Al[sbnd]Mg alloy powder

Particle morphology has a significant effect on the explosion of energetic dust which includes heat transfer and transient dispersion behavior. This study aimed to investigate the differences in transient dispersion characteristics of Al-Mg alloy powders with different shapes using Particle Image Velocimetry (PIV) and to elucidate their effects on subsequent flame propagation and explosion parameters. The results demonstrated that irregular dust exhibited lower agglomeration and terminal fall velocity (TFV) compared to spherical dust, leading to a higher overall concentration of dust involved in the explosion. In addition, the turbulence intensity in the critical ignition zone of irregular particles was relatively high, resulting in particles having more active motion characteristics during the initial ignition phase. Therefore, irregular dust exhibited more intense flame phenomena and higher explosion parameters. These findings emphasize the importance of considering particle morphology when assessing the risk associated with metal dust explosions.

A nonlinear transient-dynamics approach to atopic dermatitis: Role of spontaneous remission

Atopic dermatitis (AD) is a common skin disease that can occur in all age groups. An intriguing phenomenon associated with AD is spontaneous remission, in which the symptoms can disappear even without any treatment, especially for patients at a young age. From the point of view of dynamical evolution, spontaneous remission in AD is a transient phenomenon. A clinic implication is that, if the transient time is short, then aggressive treatment may not be necessary. A key question is thus, statistically, how long the transient time can be? Due to the lack of clinic data, mathematical modeling is a viable approach to addressing this question. Modeling AD as a nonsmooth dynamical system and regarding the disease as a transient phenomenon with spontaneous remission marking the end of the transient, we obtain a quantitative understanding of the statistical characteristics of AD. In particular, we find that, depending on the immune state, two different types of transient behaviors can arise. For type-I spontaneous remission characterized by a healthy immune level with its skin state exhibiting mild oscillations, the transient time is short, which typically occurs in patients between infancy and childhood. In contrast, type-II spontaneous remission is characterized by a low immune level and its skin state exhibits severe oscillations with a long recovering time. Quantitatively, a scaling relation exists between the average transient time (or recovery time) and some key physiological parameters, revealing that the transient is superpersistent in the sense that its average lifetime can diverge in a drastic way: e∞ as a bifurcation parameter approaches a critical value. In this case, the disease is essentially permanent, thereby requiring and justifying active treatment.

Heat transfer near a growing bubble during nucleate boiling using dual-tracer laser-induced fluorescence thermometry

Boiling heat transfer associated with bubble growth is perhaps one of the most efficient cooling methodologies due to its large latent heat during phase change. Despite the significant advancements, numerous questions remain regarding the fundamentals of bubble growth mechanisms, which is a major source of enhanced heat dissipation. This work aims to accurately measure three-dimensional (3D), space and time-resolved, local liquid temperature distributions surrounding a growing bubble to quantify the heat transfer in the superheated liquid layer during bubble growth. The dual tracer laser-induced fluorescence thermometry technique combined with high-speed imaging captures transient 2D temperature distributions, that will render 3D temperature distributions by combining multiple 2D layers, within a 0.3 °C accuracy at a 30 μm resolution. Two fluorescent dyes, fluorescein and sulforhodamine B, were used to measure transient temperatures, by account of their temperature-sensitive emissions. The results show that the temperature close to the heated surface and bubble interface exhibits an acute transient behavior at the time of bubble departure. The growing bubble works as a pump to remove heat from the surface with a peak temperature difference of up to 10 °C during its growth and departure. The experimental results were compared with previously reported studies to validate the accuracy of the technique. It was found that the heat transfer coefficient close to the bubble interface and heater is approximately 1.3 times higher than the heat transfer coefficient in the bulk liquid.

Configuration size optimization of gas-electric hybrid power systems on ships considering energy density and engine load response

System component sizes and their energy densities impact the long-term ship energy efficiency and economics, whereas power source load response influences system transient behavior, posing challenges to system design and energy management when clean fuels are used onboard. In this paper, a novel component sizing method is proposed for integrating reciprocating gas engines and energy storage systems (ESS) on ships, considering energy density and load response simultaneously. By specifying gas engine powers and ESS capacities as normalized optimization variables by ship scales, this method optimizes them based on the A. J. Klee multi-index evaluation and single-objective particle swarm optimization (PSO). Energy densities of engines and ESS were introduced to demonstrate the trade-off between the power-splitting and increased system mass and hull resistance. The engine load response was incorporated into the rule-based energy management strategy (EMS) to limit power ramps. This method was examined in the case study by taking four cruise ships as examples. It can be found that implementing the proposed evaluation-based optimization can improve cruise ship energy efficiency while maintaining reliability over the voyage. It is possible to reduce fuel consumption and carbon emissions by up to 17.1% and 14.8%, respectively. The minimum system reliability can be increased from 0.025 to 0.475 during transients. Furthermore, ship life-cycle costs can be reduced compared to the original design method, and the payback period for gas engines, ESS, and fuel tanks can be shortened to less than six years. Among the various cases, the definition of normalized optimization variables broadens the applicability of this method away from a specific ship, allowing it to be applied to ships of various tonnages and types.

The effect of anisotropic rate dependency on the deformation response of Ti-6242 during dwell fatigue loading

The α phase of titanium alloys is known to exhibit both elastic and plastic anisotropic mechanical behavior during deformation loading. Recent experimental studies indicate that single crystal rate dependency may also be anisotropic, though these studies are limited in scale and scope. Consequently, we present a study in which anisotropic rate dependency is studied on polycrystalline samples via crystal plasticity finite element (CPFE) simulations, which are compared against previously-published data from electron backscatter diffraction/digital image correlation (EBSD-DIC) experiments. Cold dwell fatigue loading is utilized, owing to the propensity for transient behavior during constant-load dwells, which is hypothesized to be sensitive to the relative rate dependencies on different slip families (i.e., basal, prismatic, and pyramidal) in hexagonal close packed crystals. A suite of CPFE simulations is conducted on polycrystalline samples in which the slip family rate dependency values are parameterized. We analyze simulation results by focusing on the slip activity and accumulation of slip on the various slip families as a function of dwell cycles, as well as the transient effect during singular dwell cycles, for hundreds of crystals simultaneously. Results are further discussed through the lens of findings from EBSD-DIC experiments.

A stable implicit nodal integration-based particle finite element method (N-PFEM) for modelling saturated soil dynamics

In this study, we present a novel nodal integration-based particle finite element method (N-PFEM) designed for the dynamic analysis of saturated soils. Our approach incorporates the nodal integration technique into a generalised Hellinger-Reissner (HR) variational principle, creating an implicit PFEM formulation. To mitigate the volumetric locking issue in low-order elements, we employ a node-based strain smoothing technique. By discretising field variables at the centre of smoothing cells, we achieve nodal integration over cells, eliminating the need for sophisticated mapping operations after re-meshing in the PFEM. We express the discretised governing equations as a min-max optimisation problem, which is further reformulated as a standard second-order cone programming (SOCP) problem. Stresses, pore water pressure, and displacements are simultaneously determined using the advanced primal-dual interior point method. Consequently, our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM formulation. Numerical experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy, obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM approaches. This work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.

Cannabidiol for moderate-severe insomnia: a randomized controlled pilot trial of 150 mg of nightly dosing.

Low-dose cannabidiol (CBD) has become readily available in numerous countries; however, little consensus exists on its efficacy as a sleep aid. This trial explored the efficacy of 150 mg of CBD (n = 15) compared with placebo (n = 15) as a sleep aid in primary insomnia. CBD supplementation was hypothesized to decrease insomnia symptoms and improve aspects of psychological health, relative to placebo. Using a randomized, placebo-controlled, parallel design featuring a single-blind placebo run-in week followed by a 2-week double-blind randomized dosing phase, participants consumed the assigned treatment sublingually 60 minutes before bed nightly. Wrist-actigraphy and sleep diaries measured daily sleep. Sleep quality, sleep effort, and well-being were measured weekly over 4 in-laboratory visits. Insomnia severity and trait anxiety were measured at screening and study conclusion. Insomnia severity, self-reported sleep-onset latency, sleep efficiency, and wake after sleep onset did not differ between treatments throughout the trial (all P > .05). Compared with placebo, the CBD group reported greater well-being scores throughout the trial (trial end mean difference = 2.60; standard error: 1.20), transient elevated behavior following wakefulness scores after 1 week of treatment (mean difference = 3.93; standard error: 1.53), and had superior objective sleep efficiency after 2 weeks of treatment (mean difference = 6.85; standard error: 2.95) (all P < .05). No other significant treatment effects were observed. Nightly supplementation of 150 mg CBD was similar to placebo regarding most sleep outcomes while sustaining greater well-being, suggesting more prominent psychological effects. Additional controlled trials examining varying treatment periods and doses are crucial. Registry: Australian New Zealand Clinical Trials Registry; Name: Cannabidiol (CBD) treatment for insomnia; URL: https://anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12620000070932; Identifier: ACTRN12620000070932. Narayan AJ, Downey LA, Rose S, Di Natale L, Hayley AC. Cannabidiol for moderate-severe insomnia: a randomized controlled pilot trial of 150 mg of nightly dosing. J Clin Sleep Med. 2024;20(5):753-763.

Characterizing the mechanical deformation response of AHSS steels: A comparative study of cyclic plasticity models under monotonic and reversal loading

This study evaluates the performance of a user-defined combined hardening modeling method for advanced high-strength steels (AHSS) under monotonic and reversal loading conditions. The plastic behavior of TWIP980 and TRIP980 AHSS sheet metals is investigated using a cyclic plasticity modeling approach. The model incorporates an isotropic von Mises yield criterion and a single-term Chaboche nonlinear kinematic hardening rule. Monotonic and reversal loading stress-strain curves are predicted and compared with experimental results. The model accurately captured the Bauschinger effect for both materials, but it needs help to effectively model the permanent softening behavior observed in TWIP980 steel. Overall, the proposed modeling method agrees well with experimental results for monotonic loading and accurately represents the Bauschinger effect and transient behavior during reversal loading. However, better improvements are needed to capture the permanent softening behavior of TWIP980 steel.

A Detailed Study of Boiling Phenomena in Forced Convective Quenching Experiments

A detailed study at the microscopic level of the transient behavior of boiling phenomena during quenching of an AISI 304 stainless steel, conical-end, cylindrical probe in flowing water at 60 °C was conducted using high-speed video recordings and cooling curve data acquisition. Two free-stream velocities (0.2 and 0.6 m/s) and two initial probe temperatures (850 and 950 °C) were investigated. It was complemented by video recordings at 60 fps to calculate the wetting front velocity. Surface heat flux histories at the thermocouple positions were estimated by solving the corresponding Inverse Heat Conduction Problem. As the water velocity increases the duration of the vapor film at each thermocouple position shortens and the difference among cooling curves at the thermocouple positions decreases. Increasing the initial temperature increases the duration of the vapor film stage. The wetting front velocity increased from 4 to 6 m/s. The time to reach the maximum surface heat flux at the position of the thermocouple closest to the probe tip ranged from 9.7 to 18 s. Undulations at the vapor-liquid interface that appear periodically and propagate in the direction of quenchant flow were observed early during the vapor film stage. Later, before the collapse of the vapor film, a kind of a shock wave was generated at the probe tip which modified the appearance of the film. Once the Leidenfrost temperature is reached, a wetting front (which consists of many small bubbles that coalesce rapidly in a very small area) is formed and travels in the direction of quenchant flow while fewer and larger bubbles nucleate and grow upstream. The nucleation, growth and detachment of the larger bubbles was studied; as the free-stream velocity decreases larger values of bubble maximum diameter and half-life time were observed, while the initial temperature has a marginal effect on these quantities.