Entrainment Phenomena Research Articles

Experimental and theoretical research on upper plenum entrainment with air-water and steam-water

Upper plenum entrainment phenomenon occurs in the automatic depressurization process during the Small Break Loss of Coolant Accident (SBLOCA) in reactor pressure vessel, which may result in reactor disaster. The upper plenum entrainment experiments with and without reactor internals were carried out with air-water and steam-water as working mediums on the Automatic Depressurization and Entrainment Test Loop for Upper plenum entrainment (ADETEL-U) which scaled after AP1000 nuclear reactor. The experimental phenomena were observed by visualization method and the reliable data were collected and analyzed. The results indicate that the entrainment rate will increase with the increase of gas flow rate under the same hg∗, and the entrainment rate will decrease significantly with the decrease of the mixed liquid level when the range of hg∗ is low. The results confirm that a large number of liquid droplets will be deposited on the surface of the reactor internals, which greatly reduces the entrainment rate. Under the same conditions, the entrainment rate with the reactor internals is about 10% of that without the reactor internals. There is a huge discrepancy between the existing pool entrainment rate models and the experimental data, with the maximum deviation of 200 times. Based on the experimental results, new upper plenum entrainment models for near surface region and high gas flux region of momentum controlled region are proposed. The error decreases by orders of magnitude compared to existing models, which suggested that the new model can accurately predict upper plenum entrainment phenomenon in the pressure vessel.

A study on the classification performance of water-injection hydrocyclone

Aiming at the problem of fine particles entrainment in the underflow of hydrocyclone during the metal grinding classification process, a water-injection hydrocyclone was proposed to improve the classification efficiency. Through external injection of water on the wall surface of the cone section, the particles settling in the region were loosely graded so that the fine particles settled in the wall surface returned to the inner swirl again, thus reducing their entry into the underflow. Numerical simulation was used to explore the differences in the internal flow field characteristics and separation performance of the hydrocyclone after adding the water-injection structure. Then the industrial tests were conducted on the classification performance of the water-injection hydrocyclone. Numerical results showed that compared with the conventional hydrocyclone, the static pressure, tangential and axial velocity of the fluid inside the water-injection hydrocyclone increased, while the turbulence intensity decreased. The experimental results showed that with the increase of water-injection flow rate, the content of -74 μm particles in the underflow of water-injection hydrocyclone first decreased and then increased, and the comprehensive classification efficiency increased and then decreased accordingly. Compared with the conventional hydrocyclone, the content of -74 μm particles in the underflow of the water-injection hydrocyclone was reduced from 26.34% to 23.95%, and the comprehensive classification efficiency was increased from 69.22% to 73.03%, which mitigated the phenomenon of fine particles entrainment in the underflow.

Development of advanced AI-based segmentation and prediction method for air entrainment in plunging water jets

Understanding air entrainment phenomena induced by plunging water jets is critical in the fields of nuclear and hydraulic engineering. Air entrainment is one of the key safety design parameters for nuclear systems. However, most existing studies rely on empirical correlations or curve-fitting models to estimate bubble penetration depth, and no agreed-upon calculation principle exists for varying jet conditions. To address these limitations, this research developed two advanced AI approaches: an improved YOLOv5 for segmenting air entrainment and the NSGA-III-BPNN method for predicting penetration depth. The improved YOLOv5 enables real-time segmentation and extraction of air entrainment motion and dynamics under diverse conditions, demonstrating high scalability and robustness. The penetration depth estimated using the improved YOLOv5 shows greater accuracy compared to conventional empirical correlationsand is more efficient than traditional image post-processing techniques for classifying shape regimes based on dynamic air entrainment patterns. To overcome the limitations of object segmentation, which typically relies on video or image data, the NSGA-III-BPNN method predicts maximum penetration depths with greater accuracy than YOLOv5, offering a more effective prediction model for air entrainment penetration depth. By leveraging advanced AI techniques, the research not only provides valuable segmentation data for refining computational fluid dynamics (CFD) modeling but also paves the way for significant advancements in both nuclear and hydraulic engineering.

Experimental study on effect of pressure on ADS-4 liquid entrainment characteristics in T-junction

Liquid entrainment phenomenon can occur in the T-junction formed by the vertical ADS-4 pipeline and the hot pipe section during SBLOCA process in AP1000 reactor. At present, most of the studies on the liquid entrainment phenomenon in T-junction with large branch pipe concentrate on the atmospheric pressure condition, which is difficult to accurately reflect the real state of the accident process. The liquid entrainment experiments were carried out at 0.1–0.4 MPa on ADETEL facility. The results show that there will be obvious reverse flow phenomenon in the branch at 0.1 MPa and the phenomenon disappears gradually with the increase of pressure. Furthermore, the occurrence of intermittent two-phase slug flow in the horizontal tube was observed at lower pressures. As pressure increases, the entrainment process will become more continuous and stable, with a concomitant reduction in intermittency. The steady-state entrainment liquid level and the onset of entrainment liquid level both decrease with increasing pressure, indicating that increasing pressure can facilitate the liquid entrainment amount. The existing correlations cannot accurately estimate the entrainment amount during SBLOCA in nuclear reactor with a deviation of more than +100% between the predictions and experimental data.

Entrainment: Transcendental Condition that Affected with Musical

This research examines the phenomenon of entrainment, which is associated with atmospheric phenomenon in meteorology, and is now also used in a person’s psychological and neurological state that leads to a state of brainwave synchronization (neural entrainment). In the most extreme conditions, this neural oscillation process will make a person enter the transcendental phase. This research is examined through a qualitative method by conducting a literature study of a number of studies on the phenomenon of entrainment. The findings obtained by researchers and academics related to entrainment can be a source of evidence for this research. The results of the research conducted found that entrainment can be the most logical explanation to explain a number of transcendental phenomenon associated with traditional or modern music. Entrainment is also a scientific explanation for the phenomenon of being possessed by spirit in a number of traditional arts in Indonesia and entrainment also affects human behavior which can reach the most extreme phase when affected by music to the subconscious level. This article is not sufficient to provide a significant explanation for the phenomenon of trance in some traditional Indonesian arts. More proofs, experiments, and literature studies are needed to strengthen the explanation of the phenomenon scientifically.

Influence of a Pair of Unequal Rotational Fluxes on Entrained Gaseous Filament

Abstract Efforts are made to elucidate a comprehensive analysis of entrainment dynamics triggered by a couple of unequal rotational fluxes within a viscous pool. Cylindrical rollers are employed to establish the rotational field. The top drum is equally submerged in both phases and also it provides a constant rotational inertia. Concomitantly, the bottom roller is completely submerged in the viscous bath, and it provides an unequal rotational strength in reference to top roller. The average rotational strength of both rollers is measured using average Capillary number (Caavg). The entrainment phenomenon is strongly influenced by both Caavg and gap between the rollers (W/D). Characterization of entrained filament is elucidated by predicting the horizontal distance (L*), radial distance (r*), temporal vertical displacement (Y*), maximum vertical displacement (Ymax*), width (H*), and location of V-shaped diversion (Øs*). Characterization of liquid tip is performed by measuring the travel rate (γ*) along periphery of drum from receding to advancing junction. Air mass ejection from filament tip is analyzed by estimating the first bubble ejection time (t1st*), volume of accumulated of ejected gaseous masses (v*), and ejection frequency (f). Furthermore, the effect of gravitational pull (specified by Archimedes number, Ar) and viscous drag (measured by Morton number, Mo) on the pattern of entrained air filament is described. Lastly, an analytical framework is established to determine the width of the V-junction by balancing the important influencing forces, which are strongly affecting the filament. Analytical observations show a satisfactory agreement with numerical findings.

Numerical and experimental investigation on droplet entrainment mechanism and closed equations of two-fluid model

As a clean and low-carbon energy source, natural gas is an important force in achieving carbon peaking and carbon neutrality goals. Affected by the strong force of gas and liquid during mining and transportation, it exhibits the phenomenon of droplet entrainment. Entrained droplets change the properties of gas and liquid phases, which is crucial for accurate measurement of liquid film thickness, gas holdup, pressure drop and flow rates in natural gas pipelines. The measurement of entrained droplets has always been a focus and difficulty in the two-phase flow research field. Therefore, numerical simulation combined with experimental measurement are presented to study the droplet entrainment mechanism and closed equations of two-fluid model. The specific parameter settings for simulating horizontal gas–liquid annular flow based on numerical method are discussed, and effective simulation of droplet entrainment and deposition in annular flow is achieved. By comparing liquid film thickness and wave velocity from the simulation results with the experimental results, the correctness of the simulation method is verified. Then, the mechanism and dynamic evolution process of entrained droplets in annular flow are revealed, and the generation and deposition characteristics of entrained droplets are studied. As a result, the closed equations of two-fluid model such as droplet velocity, gas–liquid interface velocity, and gas–liquid interface friction factor are established. The proposed two-fluid model is validated using dual mode ultrasound and differential pressure sensors, demonstrating its good applicability and extrapolation.

Preliminary Investigation on the Kinetic Characteristics of the Glacial Debris Flows in Tianmo Valley, Tibet Plateau, China

AbstractGlacial debris flows occurring on the Tibetan Plateau consistently result in significant property damage and loss of human life. A comprehensive field investigation was conducted in Tianmo valley along the Sichuan‐Tibet Highway to reveal the dynamics of a debris flow that occurred on 11 July 2018. Furthermore, a depth‐averaged multiphase debris flow model was proposed and employed to reconstruct the characteristics of the debris flow. The model derivation, implementation, evaluation, and application were presented to demonstrate its performance. The Voellmy model was chosen because it adequately accounts for both basal frictional effects and the entrainment phenomenon. The entrainment processes, the ice melting, and the lubrication effect, were also taken into consideration. Based on the numerical results combined with field investigation data, the kinetic characteristics of the glacial debris flow were analyzed. The Tianmo valley has a small area, but the volume and erosion rate of debris flows were much larger than that of two‐phase debris flows in the same location due to ice melting. The simulation results demonstrated that the glacial debris reached a peak velocity of 20 m/s. Additionally, the volume of the debris flow increased by 50% due to the erosion over a short runout distance of approximately 4,000 m. This increase was a result of the high velocity and abundant entrainment sources on the slope. This study aims to improve understanding of the high velocity and destructive potential of debris flows in the Tianmo valley.

Investigation of Hydraulic Performance and Arrangement Optimization of Non-Prismatic Water Conveyance Tunnel—A Case Study of Project X

The water conveyance tunnel is an important hydraulic structure in water conservancy projects. Typically, it manifests as a non-prismatic tunnel due to variations in the cross-sectional geometry, which give rise to an unpredictable flow pattern that significantly impacts the secure and stable operation of the tunnel. This study takes water conservancy project X as a case and investigates the hydraulic performances of a non-prismatic water conveyance tunnel using a scale model test and numerical simulation; the hydraulic performance, such as flow pattern, discharge, flow velocity, and water depth profile are analyzed for both free flow and submerged flow conditions. The results show that the simulation data fit well with the experimental value observed in the scale model test for free flow; however, a substantial discrepancy emerges under submerged flow conditions. This discrepancy is attributable to the presence of a vacuum in the distortional plan section. Notably, the effect of water entrainment phenomena on flow rate and velocity is diminished in the scale model test, emphasizing the advantage of numerical simulation in predicting hydraulic parameters for the prototype. On this basis, the optimization of the gate shaft arrangement is executed through numerical simulation; the results indicate that the vacuum issues in the contraction section were partially resolved through structure optimization. The simulation values are close to the experimental results, and the modified design of the tunnel can be used in a water conveyance project.

Spatiotemporal Dynamics of Periodic and Aperiodic Brain Activity Under Peripheral Nerve Stimulation With Acupuncture.

Brain activities are a mixture of periodic and aperiodic components, manifesting in the power spectral density (PSD) as rhythmic oscillations with spectral peaks and broadband fluctuations. Periodic oscillatory properties of brain response to external stimulation are widely studied, while aperiodic component responses remain unclear. Here, we investigate spatiotemporal dynamics of periodic and aperiodic brain activity under peripheral nerve stimulation with acupuncture by parameterization of power spectra of EEG signals. Regarding periodic brain activity, spectral peak in delta band emerges in frontal and central brain regions indicates a typical phenomenon of neural entrainment, which is formed by coupling periodic brain activity to external rhythmic acupuncture stimulation. In addition, the statistical results show that alpha periodic power is an important indicator for characterizing the modulatory effects of acupuncture on periodic brain activity. As for aperiodic brain activity, broadband EEG spectral trend analysis demonstrates a steeper aperiodic slope in left parietal lobe and a stronger negative correlation with the aperiodic offset under acupuncture compared with resting state, with the absolute value of correlation coefficient increasing from 0.27 to 0.50. Based on the two parameters that can best characterize the acupuncture effect, alpha periodic power and aperiodic slope, the accurate decoding of acupuncture manipulation is realized with AUC = 0.87. This work shows the modulatory effect of peripheral nerve stimulation with acupuncture on the brain activity by characterizing the periodic and aperiodic spectrum features of EEG, providing new insights into the comprehensive understanding of the response processes of human brain to acupuncture stimulation.

Quasi-Period Dynamics of Soliton Molecules: Route to Chaos and Intrinsic Frequency Entrainment

Soliton molecules in optical resonators have attracted remarkable attention in nonlinear dynamics, driven by their compelling analogies with matter molecules. So far, while extensive research has been conducted on their generation, pulsations, and dissociation behaviors, the investigation of their quasi-periodic dynamics has been relatively limited. Here, we present a systematic exploration of the quasi-periodic dynamics of soliton molecules using advanced balanced optical cross-correlation techniques. The incommensurable quasi-period bifurcations constituted of cascaded Hopf bifurcations are found, providing an unambiguous pathway toward chaotic soliton molecules. The chaotic intramolecular dynamics are analyzed by time series, radio frequency spectra, phase portraits, and Lyapunov exponent analysis. In addition, we reveal an intrinsic frequency entrainment phenomenon experimentally. Such frequency entrainment provides a novel perspective on synchronization in optical resonators, encompassing the competition and interaction of oscillations across multiple temporal scales. Our experimental findings offer clear proof that the gain dynamics serve as the origin of the binding forces between solitons within the molecule, which are well supported by the numerical simulations. By advancing the understanding of sub-femtosecond resolved quasi-period dynamics of optical soliton molecules, this study contributes to the broader field of complex nonlinear dynamics, paving the way for future explorations into the intricate behaviors of solitons within optical resonators and relevant fields.

A Study of Prosodic Entrainment and Social Factors in Mandarin Conversations

In conversations, interlocutors usually adopt prosody to that of their partner, and they become similar in prosodic production for successful communication. This phenomenon of prosodic entrainment is related to complex factors. This study aims to explore the relationship between prosodic entrainment and social factors. Two analyses are accomplished: the analysis of prosodic entrainment and gender, and the analysis of prosodic entrainment and role. In terms of prosodic entrainment and gender, it is found that the most prosodic features are entrained in female-male conversations, and the least in male-male conversations. In terms of prosodic entrainment and roles, it is found that different roles have influence on the entrainment degree, and information givers entrain more to followers in conversation.

Effect of frother on bubble entraining particles in coal flotation

Understanding the effect of frother on bubble entraining coal particles is an important guidance for regulating coal flotation behavior. The bubble properties and the flow field surrounding the bubble were investigated using the particle image velocimetry (PIV) technique. The bubble equivalent diameter, bubble deformation rate and low-velocity region area reduced as the frother concentration increased due to a decrease in surface tension. The oscillation of the bubble and low-velocity region were subsequently analyzed. As the frother concentration increased, the oscillation frequency of the bubble and low-velocity region gradually decreased until 1.6 × 10−4 mol/L after that it tended to be stable. The oscillation amplitude of the bubble and low-velocity region slightly varied with the frother concentration but increased as the distance away from the bubble increased. The coal particle trajectories and entrainment phenomenon under the effect of frother were explored via the high-speed motion acquisition equipment. Three typical trajectories that Escape, Offset entrainment, and Entrainment were used to describe the coal particle behavior around the bubble. A predictive model of coal particle entrainment probability influenced by frothers was established. Our findings can provide valuable insight into the development of technology for mineral flotation.

Experimental research on liquid entrainment in the inclined up tee branch

The tee branch structure is broadly used in the nuclear power systems, and liquid entrainment in the tee branch has been studied in depth. However, most of the existing research focuses on the vertical tee branch, while the study about the entrainment phenomenon in the inclined tee branch hasn’t formed mature contents. This research aims to analyze the liquid entrainment in the inclined up tee branch. The liquid level measurement method of the Automatic Depressurization and Entrainment TEst Loop (ADETEL) was improved and supplementary experiments were conducted with single-end gas inlet of vertical tee branch. In addition, the test loop was modified to conduct visualization experiments on liquid entrainment experiments of the tee branch with a 45 degree angle. The experimental result reveals that the liquid entrainment phenomenon in the inclined tee branch is significantly different from that in the vertical tee branch. Based on the experimental phenomena and data, a new OLE (Onset of Liquid Entrainment) model is proposed which is well fitted with the existing data. Then, an entrainment rate model is proposed by nondimensionalizing the key parameters affecting the steady-state entrainment, with the error within ± 15% of the experimental data.

Numerical modeling of body shape effect on the performance of a square cyclone separator

This study aims to determine the effect of a square cyclone body shape on the performance of a square cyclone separator. To achieve this goal, four square cyclone separators with square lengths 0, 1, 2, and 3 times the hydraulic diameter of the cyclone body were considered. The simulation of the gas-solid flow was carried out using the Euler-Lagrange approach, while the gas flow was modeled by Navier–Stokes equations and the Reynolds stress turbulent model (RSTM), and the injected solid particle was solved using the Newton equation. The pressure drop, separation efficiency, and flow pattern were investigated to evaluate the performance of square cyclone separators. The results revealed that the pressure drop and separation efficiency decreased as the relative square length increased. In the case with a lower relative square length, the vortex core penetration is less than that in the other cases, which leads to a decrease in the entrainment phenomena and separation efficiency enhancement. At an inlet velocity of 16 m/s, an increase in the relative square length from 0 to 3 reduced the pressure drop by approximately 35%. At an inlet velocity of 24 m/s and a particle diameter of 8 µm, with an increase in the relative square length from 0 to 3, the efficiency decreased from 88.7 to 77.4%.

Comparative study on the influence of incident heat flux on thermal runaway fire development of large-format lithium-ion batteries

In response to the growing demand for higher energy density in various applications, large-format batteries have gained popularity. However, the larger size of these batteries also increases their exposed area, which may lead to more severe thermal events. This study aims to understand the influence of incident heat flux on the occurrence and progression patterns of fires in large-format lithium-ion batteries. Two representative large-format lithium-ion batteries, 38 Ah LiNi0.3Co0.3Mn0.3O2 prismatic cell and 78 Ah LiNi0.8Co0.1Mn0.1O2 pouch cell, were investigated. To evaluate the thermal hazard to the environment, the heat release rates (HRR) of the lithium-ion battery fire were measured under incident heat fluxes ranging from 10 to 50 kW∙m−2, using the oxygen consumption principle. The results highlight significant differences in thermal runaway and fire development between the 38 Ah and 78 Ah cells, attributable to variations in structure and materials, and scale effect. The 38 Ah cell exhibited an evident venting stage, characterized by an unignited jet on the verge of ignition, followed by a transition from momentum-driven jet fire to buoyancy-driven jet fire. In contrast, the 78 Ah cell experienced direct ignition, accompanied by strong air entrainment, overflow flame, and flame sinking phenomena as the fire progressed. Notably, unlike the 38 Ah cell, the peak HRR, THR, and burning time of the 78 Ah cell were minimally sensitivity to the incident heat flux. Furthermore, a generalized relationship model between the incident heat flux and the ignition time was established and validated based on the energy conservation equation during the ignition stage of the cell. This model enhances our understanding of the interplay between incident heat flux and ignition time, contributing to the development of strategies for fire prevention and mitigation in large-format lithium-ion batteries.

Impact of buoyant jet entrainment on the thermocline behavior in a single-medium thermal energy storage tank

This paper presents the characterization and management of dynamic thermocline behaviors in a single-medium thermocline (SMT) thermal energy storage tank with the aim of its performance improvement. In particular, the flow mixing induced by the entering thermal jet, its impact on the temperature stratification and its mitigation measure are systematically explored by both numerical and experimental methods. Results of CFD simulation and Particle Image Velocimetry (PIV) visualization clearly demonstrate the jet entrainment phenomenon and the typical flow patterns featured by the rising buoyant plumes. For the storage tank with simple inlet port, this thermal jet would cause the thermal overturning, the strong fluid mixing and convection heat transfer, resulting in the degradation of temperature stratification and the thermocline decay (Rigradient<0.25 at certain positions of the tank). It has also been shown by PIV measurement that the impact of thermal jet, characterized by the jet penetration length, becomes stronger with the increasing injecting flow rate and with the decreasing temperature difference between the injecting and existing fluids.Orifice baffle-type distributor has then been proposed and optimized, showing clearly its effectiveness for mitigating the impact of thermal jet on the temperature stratification. Both the initial uniform orifice baffle and the optimized orifice baffle distributors are then fabricated and installed into a lab-scale cuboid SMT storage tank. Charging operations are performed under different inlet flow rates (Qin: 0.3 to 1.5 L·min−1) and temperature differences between hot and cold fluids (∆T: 30 to 50 K). Experimental results obtained show that the optimized distributor could always lead to the better thermal performance (capacity ratio up to 0.94 and charging efficiency up to 0.8) than the initial uniform baffle distributor, providing more flexible operating conditions of the SMT storage systems in different industrial sectors.

Spontaneous dyadic behavior predicts the emergence of interpersonal neural synchrony

Synchronization of neural activity across brains – Interpersonal Neural Synchrony (INS) – is emerging as a powerful marker of social interaction that predicts success of multi-person coordination, communication, and cooperation. As the origins of INS are poorly understood, we tested whether and how INS might emerge from spontaneous dyadic behavior. We recorded neural activity (EEG) and human behavior (full-body kinematics, eye movements, and facial expressions) while dyads of participants were instructed to look at each other without speaking or making co-verbal gestures. We made four fundamental observations. First, despite the absence of a structured social task, INS emerged spontaneously only when participants were able to see each other. Second, we show that such spontaneous INS, comprising specific spectral and topographic profiles, did not merely reflect intra-personal modulations of neural activity, but it rather reflected real-time and dyad-specific coupling of neural activities. Third, using state-of-art video-image processing and deep learning, we extracted the temporal unfolding of three notable social behavioral cues – body movement, eye contact, and smiling – and demonstrated that these behaviors also spontaneously synchronized within dyads. Fourth, we probed the correlates of INS in such synchronized social behaviors. Using cross-correlation and Granger causality analyses, we show that synchronized social behaviors anticipate and in fact Granger cause INS. These results provide proof-of-concept evidence for studying interpersonal neural and behavioral synchrony under natural and unconstrained conditions. Most importantly, the results suggest that INS could be conceptualized as an emergent property of two coupled neural systems: an entrainment phenomenon, promoted by real-time dyadic behavior.

Experimental Study on the Smoke Temperature Decrease near Natural Vents Induced by Air Entrainment in a Tunnel Fire

Previous studies have shown that there is a large difference in the temperature of smoke in the upstream and downstream of a vertical shaft, but no quantitative study on the subject has been conducted. In this paper, a model experimental test was conducted to study the effect of a natural vertical shaft on the distribution of smoke temperature in tunnel fires. A laser sheet was used as an assisting tool to show the smoke flow field. A series of tests were conducted with shaft heights varying from 0.2 m to 1.2 m and a heat release rate (HRR) of 9 kW, 17 kW, 29 kW, and 65 kW. The entrainment phenomenon around the vertical shaft was analyzed, and the results showed that the amount of fresh air entrainment is the main reason for the temperature decrease in upstream and downstream smoke temperatures. Based on the experimental results, an empirical model for predicting the amount of fresh air entrainment and a prediction model of the downstream smoke temperature were proposed, and the predicted values are in good agreement with the experimental values.

A feasibility study of pre-sleep audio and visual alpha brain entrainment for people with chronic pain and sleep disturbance.

Chronic pain and sleep disturbance are bi-directionally related. Cortical electrical activity in the alpha frequency band can be enhanced with sensory stimulation via the phenomenon of entrainment, and may reduce pain perception. A smartphone based programme which delivers 10 Hz stimulation through flickering light or binaural beats was developed for use at night, pre-sleep, with the aim of improving night time pain and sleep and thereby subsequent pain and related daytime symptoms. The aim of this study was to assess the feasibility and give an indication of effect of this programme for individuals with chronic pain and sleep disturbance. In a non-controlled feasibility study participants used audio or visual alpha entrainment for 30 min pre-sleep each night for 4 weeks, following a 1 week baseline period. The study was pre-registered at ClinicalTrials.gov with the ID NCT04176861. 28 participants (79% female, mean age 45 years) completed the study with high levels of data completeness (86%) and intervention adherence (92%). Daily sleep diaries showed an increase compared to baseline in total sleep time of 29 min (p = 0.0033), reduction in sleep onset latency of 13 min (p = 0.0043), and increase in sleep efficiency of 4.7% (p = 0.0009). Daily 0-10 numerical rating scale of average pain at night improved by 0.5 points compared to baseline (p = 0.027). Standardised questionnaires showed significant within-participant improvements in sleep quality (change in median Global PSQI from 16 to 12.5), pain interference (change in median BPI Pain Interference from 7.5 to 6.8), fatigue (change in median MFI total score from 82.5 to 77), and depression and anxiety (change in median HADS depression score from 12 to 10.5 and anxiety from 13.5 to 11). Pre-sleep use of a smartphone programme for alpha entrainment by audio or visual stimulation was feasible for individuals with chronic pain and sleep disturbance. The effect on symptoms requires further exploration in controlled studies.