Wall Distance Research Articles

Effects of the Uncertainty of Wall Distance on the Simulation of Turbulence/Transition Phenomena

Effects of the Uncertainty of Wall Distance on the Simulation of Turbulence/Transition Phenomena

Mesoscopic modeling of interaction dynamics for two bubbles in the near-wall region

A nonorthogonal hybrid thermal lattice Boltzmann cavitation model is proposed in this study. The flow and density field are described by the pseudopotential model, while the temperature is realized by solving the macroscopic temperature function. The model is verified by simulating the Laplace law and a bubble evolves in the unbounded region. Furthermore, the interaction dynamics between two bubbles near the wall are investigated. The bubble collapse intensity is dominated by the initial bubble–bubble distance and bubble–wall distance. A pair of inclined reentrant jets are reported for the strong interaction modes, and splashing resulting from the jet collisions may lead to the bubble center shifting away from the wall or the axis of symmetry. For the weak interaction mode with dimensionless bubble-wall distance γ between 1 and 3.5, the maximum collapse pressure increases linearly. The maximum collapse pressure Pc_max decreases with increasing bubble spacing, and Pc_max for distance between two bubbles with d2=40lu increases by 9 % to 16.2 % compared to that of d2=30lu. The variation of the liquid film thickness h between adjacent cavitation bubbles is primarily governed by the expansion velocity of the bubble wall ḣ, and similarly, the thickness of the liquid film between the bubble wall follows the same principle with h∼ḣ−2. The bubble radius in the growth stage aligns closely with the theoretical analysis for the weak interaction mode, while discrepancies appear between the simulation and prediction due to the bubble losing its roundness in the collapse stage.

Tricolored Bat (Perimyotis subflavus) microsite use throughout hibernation

Abstract White-nose syndrome (WNS) has caused dramatic population declines in several bat species, including the Tricolored Bat (Perimyotis subflavus). Several studies have documented bats using colder roosting temperatures after infection; however, this strategy may have costs such as increased freezing risks or greater predation risks and it is unknown when during hibernation bats begin to utilize these colder temperatures. Our aim was to examine Tricolored Bat roost locations in a WNS-positive site in relation to roost microclimate and other environmental conditions throughout the hibernation season. We conducted monthly censuses of tricolored bats across 2 hibernation seasons (November to March 2020 to 2021 and October to March 2021 to 2022) in a WNS-positive hibernaculum in northwestern South Carolina and recorded skin and adjacent wall temperature, tunnel section, and distance from the entrance for each bat species. We continuously measured hibernacula temperature and relative humidity during both hibernation seasons. Most bats roosted in the back part of the tunnel where temperatures were warmer and more stable, and vapor pressure deficit (VPD) and human disturbance were low. However, >20% of bats roosted in the front, where roost temperatures were significantly colder and VPD was higher but more variable; human disturbance was also higher in this section. The proportion of bats in each tunnel section did not vary among months and we did not find evidence of significant movement to the front section of the tunnel as hibernation progressed based on marked bats; however, bats in the front section roosted higher on the wall suggesting that they may be avoiding human disturbance or predators. Our results support the notion that no optimum hibernation temperature exists for tricolored bats and that high VPD and disturbance are likely important factors driving microsite use. Protection of Tricolored Bat hibernacula that offer a range of microclimates or a network of sites in close proximity that offer different microclimates may be helpful for recovery of this species.

The Influence of Kinesiology Tape on Posture and Breathing Mechanics in Healthy Individuals: A Randomized Trial

Background and Purpose: Kinesiology tape (KT) has been used clinically to improve posture, mobility, and muscle strength. Limited research has investigated the effect of KT on respiratory function. The purpose of this study was to explore the effects of KT on posture and breathing in healthy individuals. Methods: Ninety-two adult participants were randomly assigned to a KT, sham tape (ST), or control group. Data collection occurred over 2 sessions. Baseline measurements included chest wall expansion (CWE) at the sternal angle (SA) and xiphoid process (Xi), maximal inspiratory pressure (MIP), and tragus (TWD) and acromion (AWD) to wall distances. Next, KT or ST was applied to the upper back and neck, or no tape was applied based on group assignment. Measurements were then repeated. Participants returned for a final round of measurements 48 hours later. Mixed-measures ANOVAs were used to determine the influence of tape at baseline (T0), immediately post-taping (T1), and 48 hours post-taping (T2). Post hoc analyses used the Tukey method. Results: Analysis showed significant differences between T0 and T1 (P = .004) and between T1 and T2 (P = .004) for AWD on the left. CWE-Xi data showed within group differences T0-T2 (P = .004) and T1-T2 (P = .004). MIP data showed within group differences between T0 and T1 (P = .001), T0 and T2 (P < .001), and T1 and T2 (P < .001). Discussion: KT had a limited and inconsistent impact on posture where there was a decrease in AWD on the left from T0 to T1 and then an increase from T1 to T2. No other changes in posture were found. Taping did not affect CWE at the SA. There was an evident training effect for CWE-Xi and MIP, where all groups saw increases over time. Conclusion: This method of KT application is not supported as an intervention for influencing posture and enhancing inspiratory breathing mechanics in healthy adults. Further investigation of KT in other populations is needed.

Dynamics of single cavitation bubble collapse jet under particle-wall synergy

The interaction between a particle and a cavitation bubble significantly influences the erosive effect on the wall surface of flow passage components in fluid machinery. This paper investigates the dynamics of a single bubble collapse jet under the synergetic effects of a particle and a wall, using Kelvin impulse theory and high-speed photographic experiments. A theoretical model to predict the intensity and direction of the collapse jet at arbitrary locations near the particle and the wall is constructed on the basis of the image method and Weiss's theorem. The accuracy of the model is verified by comparison with a large number of experimental results. The mechanisms underlying the relative contributions of the particle and wall to the behavior of jet intensity and direction are explored. The effects of key parameters on jet intensity and direction are also quantitatively analyzed, including the relative positions of the particle, wall, and the bubble and the dimensionless particle radius. The main conclusions are as follows: (1) the particle will cause a deflection in the direction of the collapse jet near the wall, leading to the formation of a jet attraction zone. The proposed theoretical model effectively predicts the spatial location of this zone. (2) There exists a region in which the jet is weak, and there is a jet equilibrium point with zero impulse between the particle and the wall. The position of this equilibrium point gradually approaches the wall in a nonlinear manner with increasing particle size and in a quasi-linear manner with decreasing particle–wall distance. (3) When the particle and the bubble are the same distance from the wall, the jet direction gradually changes from toward the particle to vertical to the wall in a nonlinear manner as the bubble–particle distance increases. Moreover, the effective range of the particle's influence on the jet direction decreases as the particle–wall distance decreases.

On the interaction between a pulsating bubble and a particle on the rigid wall

Sand-laden cavitation poses significant challenges in high dam hydrodynamics and hydraulic machinery. This study examines the interaction between a pulsating bubble and a rigid spherical particle attached to a wall, aiming to reveal its mechanical mechanisms. Particle motion is strongly influenced by two dimensionless distances: the bubble–wall distance γ and the horizontal bubble–particle distance l, both scaled by the maximum bubble radius. Parameter γ determines the bubble's evolution characteristics and affects the particle's motion. Smaller γ means the particle is mainly influenced by bubble pulsation, while larger γ makes the particle more affected by wall vortices. The effect of l is primarily seen in the particle's velocity magnitude. A larger l causes the particle to move toward the bubble, while a smaller l makes it move away, due to the relative strengths of bubble expansion and contraction. We also identify parameter sets that result in 0 particle velocity and observe unique particle motions during bubble splitting and the formation of oblique jets. This study may further promote the application of underwater cavitation cleaning.

Dynamics of a single cavitation bubble near an oscillating boundary

Cavitation and its effects are well investigated, especially single bubble cavitation and its collapse near rigid and elastic boundaries. In our current article, we investigated novel experiments of a single cavitation bubble near an oscillatory boundary. We generated the cavitation bubble by laser focusing in water. A flat glass plate was fixed to the shaft of the magnetostriction oscillator coil. We investigated the dynamics of bubbles at two relative wall distances (ratio of the distance between the bubble center and plate surface to the maximum radius of the bubble) of the bubble from the glass plate in combination with four modes of oscillation. Each mode has specific frequency and amplitude of oscillation. The high-speed camera captured the dynamics of the bubble using the back-illumination method with a framing rate of 120Kfps and simultaneously we used an optical CMOS sensor to measure the oscillation of the glass plate. We presented a clear comparison among the bubble dynamics near stationary and oscillating plates with parameters such as oscillating modes and direction. We correlated the dynamics of the bubble with the motion of the plate. In addition, we highlighted the differences including the characteristics of bubble shape and jetting that occurred during the collapse phase. The comparison of the time histories of the bubble’s equivalent size postulated that the bubble’s collapse times vary significantly in some cases compared to the bubble’s dynamics near the stationary plate. In all cases, we noticed the shortening of the bubble’s collapsing time, i.e. accelerated collapses. In our findings, we noticed a collapse times reduction of about 4–15%. Our finding signifies the importance of introducing the oscillation of the boundaries to obtain effective energy concentration over the time during the collapse. Our study also suggests that forced oscillation of boundaries is undesirable for destructive cavitation effects. The method we suggested for the manipulation of bubble dynamics holds potential for enhancing the efficiency of applications such as lithotripsy in biomedical devices, actuation and micro pumping in microfluidic devices, and effective semiconductor surface cleaning. Not but least, obtained results can be used as benchmark in future for validating numerical methods.

Can the Newer Model of Breast-Specific Positron Emission Tomography Reduce the "Blind Area"?

Objectives: Breast-specific positron emission tomography (PET) provides higher sensitivity and spatial resolution than whole-body PET/CT, but it has a blind area. Mammary glands near the chest wall sometimes present outside the field of view (FOV). A newer, dedicated breast PET (dbPET) model has a cylindrical detector with a larger diameter than previous models, so it is expected to eliminate or reduce blind areas. This study aimed to compare breast images acquired on the new dbPET model with images acquired on an older dbPET model to evaluate blind area reduction. Methods: The nipple-to-chest wall distance (mm), maximum breast cross-sectional area at the FOV edge (cm2) on the dbPET transverse images of the scanners, and the effects of patient age and body mass index (BMI) were compared. Results: There was no significant difference in the nipple-to-chest wall distance between the models (p = 0.223). The maximum breast cross-sectional area at the FOV edge was significantly larger on the newer model's images (p < 0.001). There was no significant correlation between breast size and the rate of change in both parameters. Conclusions: The new ring-type dbPET scanners with larger diameter detectors did not reduce the blind area observed on older dbPET scanners.

Experimental analysis of particle dynamics influenced by cavitation bubbles near a rigid wall

This study utilized experimental methods involving high-speed cameras to observe the interaction between cavitation bubbles, generated by a low-voltage electric spark device, and particles near a rigid wall. The dynamic characteristics of the particles were analyzed under varying conditions, including different cavitation bubble sizes, particle sizes, and distances between the cavitation bubble and the wall. Two characteristic parameters were introduced: χ for the particle and cavitation bubble sizes, and λ for the cavitation bubble wall distance. Qualitative distinctions were made among types of particle–bubble interactions, and force analysis was conducted under conditions where χ exceeded the threshold χt. The findings reveal that when χ &amp;lt; χt, particle motion is primarily influenced by the jet effects produced by the cavitation bubble. Conversely, when χ &amp;gt; χt, particle motion is dominated by the radiation forces exerted by the cavitation bubble. Under jet-dominated conditions, particle trajectories were observed to be erratic and unpredictable. For cases where λ &amp;lt; 0, the high-speed jet directly impacts the particle. Conversely, for λ &amp;gt; 0, the jet's velocity decays rapidly upon reaching the particle. In scenarios dominated by radiation forces, the cavitation bubble drew particles away from the wall, followed by their free fall back toward it. The influence of gravity, buoyancy, bubble radiation force, fluid resistance, and virtual mass force on particles was studied when radiation forces prevailed. The acceleration formula for particles was derived through the application of the bubble dynamics equation and was refined based on experimental observations.

Interaction between cavitation bubbles and plastrons on superhydrophobic surfaces

The interaction between cavitation bubbles and plastrons on superhydrophobic surfaces was investigated using a low-voltage discharge device and high-speed photography techniques. The plastron adhered to the superhydrophobic surface acts as a liquid–gas interface, giving the boundary the ability to repel cavitation bubbles. The direction of bubble collapse is determined by the vector synthesis of the Bjerknes repulsive force from the plastron and the Bjerknes attractive force from the rigid wall when the bubble collapses for the first time. Various collapse behaviors were observed, including bubbles moving away from the plastron, bubbles orienting towards the plastron, and bubbles splitting into sub-bubbles in opposite directions. During the subsequent evolution of the bubbles, the expansion of the plastron led to the reversal of the downward jet or reduced the impact velocity of the jet. Seven jet patterns were identified based on the evolution of the cavitation bubble. Starting from the impact velocity of the jet, three jet patterns, namely, the jet away from the plastron (JA), the funnel-shaped jet away from the plastron (JAF), and the funnel-shaped jet away from the plastron with vortex shedding (JAFV), were found to have a weaker effect on the boundary. Three criteria for the design of plastrons on superhydrophobic surfaces were established: VP>0.25Vmax, HP>0.55Rmax, DP>1.2Rmax. Passive pulsation of the plastron in response to the cavitation bubble exhibited similar behaviors across seven jet patterns except for the JAF pattern: torus-shaped, dish-shaped, and skirt-shaped. The dimensionless wall distance, volume ratio, and plastron morphology parameters were identified as significant factors influencing the interaction between cavitation bubbles and the plastron.

Sensitivity study of resolution and convergence requirements for the extended overlap region in wall-bounded turbulence

Direct numerical simulations (DNSs) are among the most powerful tools for studying turbulent flows. Even though the achievable Reynolds numbers are lower than those obtained through experimental means, DNS offers a clear advantage: The entire velocity field is known, allowing for the evaluation of any desired quantity. This capability includes the computation of derivatives of all relevant terms. One such derivative provides the indicator function, which is the product of the wall distance and the wall-normal derivative of the mean streamwise velocity. This derivative may depend on mesh spacing and distribution, but it is extremely affected by the convergence of the simulation. The indicator function is crucial for understanding inner and outer interactions in wall-bounded flows and describing the overlap region between them. We find a clear dependence of this indicator function on the mesh distributions we examine, raising questions about classical mesh and convergence requirements for DNS and achievable accuracy. Within the framework of the logarithmic plus linear overlap region, coupled with a parametric study of channel flows and some pipe flows, sensitivities of extracted overlap parameters are examined. This study reveals a path to establishing their high-Reτ or nearly asymptotic values at modest Reynolds numbers, but larger than the ones used in this work, accessible by high-quality DNS with reasonable cost. Published by the American Physical Society 2024

Prediction of Hydrogen Storage Vessel Explosion with Blast Wall using Machine Learning

We present a prediction of hydrogen storage vessel explosion using machine learning. A neural network model is trained to learn the waveform of a hydrogen explosion with a blast wall and used to predict the waveform with arbitrary blast wall position. The initial training revealed one of the features, blast wall distance, greatly affects the blast waveform. To emphasize the effect of that feature, feature multiplication is used instead of normalization and this enabled the training to learn the waveform correctly. The trained model can predict the blast waveform with an arbitrarily located blast wall. The result can be used in structural analysis and this will help to construct the blast wall in the hydrogen refuelling station. This research uses the CFD (Computational Fluid Dynamics) simulation by Pukyong University, South Korea, as training data.

Numerical simulation and analysis of a ducted-fan drone hovering in confined environments

Ducted-fan drones are expected to become the main drone configuration in the future due to their high efficiency and minimal noise. When drones operate in confined spaces, significant proximity effects may interfere with the aerodynamic performance and pose challenges to flight safety. This study utilizes computational fluid dynamics simulation with the Unsteady Reynolds-averaged Navier–Stokes (URANS) method to estimate the proximity effects. Through experimental validation, our computational results show that the influence range of proximity effects lies within four rotor radii. The ground effect and the ceiling effect mainly affect thrust properties, while the wall effect mainly affects the lateral force and the pitching moment. In ground effect, the rotor thrust increases exponentially by up to 26% with ground distance compared with that in open space. Minimum duct thrust and total thrust are observed at one rotor radius above the ground. In ceiling effect, all the thrusts rise as the drone approaches the ceiling, and total thrust increases by up to 19%. In wall effect, all the thrusts stay constant. The pitching moment and lateral force rise exponentially with the wall distance. Changes in blade angle of attack and duct pressure distributions can account for the performance change. The results are of great importance to the path planning and flight controller design of ducted-fan drones for safe and efficient operations in confined environments.

Effects of Materials and Riblets on Erosion Mitigation Induced by Multiple Collapses of Cavitation Bubbles

The current research investigates the effects of materials and riblets on cavitation-induced erosion morphology, depth, and cross-sectional area through experimental approaches. To achieve these aims, the erosion of pure aluminum (1xxxAl or Al) and alpha brass (CuZn37 or CZ108), in the presence and absence of bio-inspired sawtooth riblets, was examined after exposure to multiple collapses of single cavitation bubbles with a wall distance of 1.8 (dimensionless). The results indicate that the erosion morphology resembles a rounded cone with a circular cross-section. Brass provides 21.6% more erosion resistance compared to that of Al in terms of material properties. Furthermore, the erosion for both Al (depth by 3.8% and width by 18.3%) and brass (depth by 7.9% and width by 27.4%) decreases in the presence of riblets compared to the results for flat surfaces. The greater erosion resistance of brass compared to Al is attributed to the superior mechanical stability of brass, making it a potentially suitable alloy for use in propellers and hulls in the shipping industry. In summary, the results reveal that riblet-equipped materials with high mechanical durability are promising erosion-resistant materials for the shipping industry. However, the potential for chemical reactions in a cathodic environment should be addressed to provide a comprehensive perspective in regards to reducing corrosion intensity.

Wall Shear Stress Characteristics Of A Turbulent Boundary Layer Obtained With Multi-Aperture Defocusing Micro-PTV And High-Speed Stereo Profile-PIV

A multi-aperture 3d 3c micro PTV system is presented which relies on single window optical access for both high-speed tracer illumination and image recording. Similar to the “defocusing” concept described by C. Willert &amp; Gharib (1992), the wall distance of individual particles is obtained from the size of projected particle image triplets formed by a triplet of apertures on the entrance pupil of the microscope lens. The present article extends upon previously published material Klinner &amp; Willert (2022) by applying multi-aperture micro particle tracking velocimetry (MA-micro PTV) on a canonical turbulent boundary layer (TBL) to track the near-wall motion of tracer particles with the aim of estimating the unsteady wall-shear stress from particle tracks. The technique is validated with measurements of a TBL inside the closed test section of the 1 m wind tunnel of DLR in Göttingen (1mWK) at free- stream velocities of 5.2 to 20 m/s with corresponding shear Reynolds numbers between 560 and 1630. In the viscous sublayer, the probability density distributions of stream- and span-wise wall shear stress (WSS) components could be reliably captured down to probability densities of 10E−3. As far as we know, this has not been achieved in the past, particularly not for the span-wise component. For the stream-wise component the measured Reynolds-number dependency of the root mean squared fluctuations agrees to correlations by Örlü &amp; Schlatter (2011). Furthermore, the skewness of the stream-wise WSS agrees well to values from DNS. On the other hand, the span-wise WSS fluctuations consistently underestimate the predicted DNS values, for which it is assumed that the deviation can be explained by the rapid decrease of the span-wise velocity fluctuations with increasing wall distance. Wall-normal profiles of 3c velocity statistics were obtained by bin averaging of particle velocities. Up into the buffer layer, these profiles agree well with profiles from stereo PIV as well as from DNS and LES, indicating an accurate determination of both near-wall velocities and inner scaling.

A high-pressure strategy to refine and multiply nanoprecipitates for improved strength-ductility synergy in a medium-entropy FeCrNiTiAl alloy

Dispersion strengthening is one of the most effective methods to strengthen a metallic material. The strength of an aged alloy is largely affected by the precipitate size and number density of precipitates, which are often controlled by the change in temperature, time, and composition. Here we report a new high-pressure (HP) strategy for regulating the nanoprecipitates (NPs) in a Fe50Cr16Ni27Ti4Al3 medium-entropy alloy. Using a HP of 4 GPa largely refines the size of NPs from 15 to 4nm (due to the suppressed grain-growth rate) and increases the number density of NPs by two orders of magnitude (due to the increased nucleation rate). The decreased size and increased density of NPs lower the spacing distance of high-density dislocation walls and result in the formation of microbands during deformation, causing sustainable strain-hardening in the MEA, thereby improving both strength and ductility.

Effect of boundary layer thickness and dimensionless wall distance y+ on numerical simulation of heat pipes

Effect of boundary layer thickness and dimensionless wall distance y+ on numerical simulation of heat pipes

Statistics and evolution of Reynolds shear stress structure in cylinder-wake/boundary-layer interaction

The three-dimensional structures based on the quadrant classification of the tangential Reynolds stress (Qs), are studied in direct numerical simulations of cylinder-wake/boundary-layer interaction with a moderate gap ratio (G/D=1.0) and low or middle Reynolds numbers. In this paper, direct numerical simulations are performed using the immersed boundary lattice Boltzmann method (LBM). We utilize a three-dimensional clustering method to identify Reynolds shear stress structures (Qs-structures) associated with intense events. The kinematic characteristics of coherent structures are discussed through the statistical properties of Qs-structures. The spatial relationship of between vortex clusters and Qs-structures (mainly Q2-structures as well as Q4-structures) is explained by their evolution characteristics. The spatial distribution of Qs-structures, determined by the volume distribution of the minimum and maximum wall distances (ymin and ymax), are found to be similar to that of vortex clusters in the cylinder/wall interaction. In the near-wall statistical region, the secondary vortex clusters are surrounded by the parallel Q2 and Q4 pairs, and mostly lodged within the Q2. During the evolution process of coherent structures, the Q2-structures and the secondary vortex clusters developed into hairpin-like structures, respectively. The conditional average results demonstrated that the generated hairpin vortex structures are attributed to the momentum transfers.

Utilizing indicator functions with computational data to confirm nature of overlap in normal turbulent stresses: Logarithmic or quarter-power

Indicator functions of the streamwise normal-stress profiles (NSP), based on careful differentiation of some of the best direct numerical simulations (DNS) data from channel and pipe flows, over the range 550&amp;lt;Reτ&amp;lt;16 000, are examined to establish the existence and range in wall distances of either a logarithmic-trend segment or a 1/4-power region. For nine out of 15 cases of DNS data we examined where Reτ&amp;lt;2000, the NSP did not contain either of the proposed trends. As Reτ exceeds around 2000 a 1/4-power, reflecting the “bounded-dissipation” predictions of Chen and Sreenivasan [“Law of bounded dissipation and its consequences in turbulent wall flows,” J. Fluid Mech. 933, A20 (2022); “Reynolds number asymptotics of wall-turbulence fluctuations,” J. Fluid Mech. 976, A21 (2023)] and data analysis of Monkewitz [“Reynolds number scaling and inner-outer overlap of stream-wise Reynoldss stress in wall turbulence,” arXiv:2307.00612 (2023)], develops near y+=1000 and expands with Reynolds numbers extending to 1000&amp;lt;y+&amp;lt;10 000 for Reτ around 15 000. This range of 1/4-power NSP corresponds to a range of outer-scaled Y between around 0.3 and 0.7. The computational database examined did not include the zero-pressure-gradient boundary layer experiments at higher Reynolds numbers where the logarithmic trend in the NSP has been previously reported around y+ of 1000 by Marusic et al. [“Attached eddy model of wall turbulence,” Annu. Rev. Fluid Mech. 51, 49–74 (2019); “The logarithmic variance of streamwise velocity and conundrum in wall turbulence,” J. Fluid Mech. 933, A8 (2022)] according to a “wall-scaled eddy model.”

Hydroelasticity effects induced by a single cavitation bubble collapse

To investigate hydroelasticity effects on a single cavitation bubble dynamic, a focused laser was used to generate the bubble in water near a flexible aluminium foil fixed to a specimen holder with a circular aperture to allow the foil to vibrate. The bubble was generated below the foil's center. A laser-based optical sensor measured the displacement at the center of the foil. Simultaneously, a high-speed camera monitored the bubble's dynamics to correlate it with the foil's displacement. By directly measuring the foil's displacements, we provided building block missing in previous investigations. We found that a key difference between bubble dynamics near a rigid and an elastic structure was that, at relative wall distances larger or equal to unity, the bubble did not collapse on the elastic foil. The bubble's dynamics caused dominant foil displacements during its first growth (after plasma seeding) and during its subsequent collapse. Foil displacements during the bubble's first collapse were about twice as large as those during its growth phase. For lower relative wall distances, the induced foil displacements were significant until the bubble's third collapse. At larger relative wall distances, the bubble did not collapse on the elastic foil and, thus, it did not induce erosion. However, it caused foil vibrations and, therefore, may contribute to the foil's structural fatigue damage. Our study postulates that the cavitation may not be erosive, however it can induce impulsive loads causing vibrations and thereby fatigue damage of nearby structures.