Blockage Ratio Research Articles

Particle spacing and stability of initially staggered deformable particle trains migrating in a channel

Abstract We investigated the inertial migration of deformable particles in a two-dimensional channel flow. This study analyzes the effects of the channel Reynolds number ($Re$), channel blockage ratio ($k$), particle number ($N_p$) and reduced bending modulus ($E_b$) on the formation of staggered particle trains. The results show that the stable normalized distance $d_{p_{eq}} / H$ between two staggered particles is influenced by $Re$, $k$ and $E_b$, where $H$ is the channel width. As $k$ increases or $E_b$ decreases, $d_{p_{eq}} / H$ decreases. The value of $d_{p_{eq}} / H$ initially increases and then decreases with the increase of $Re$; when $E_b$ is large and $k$ is small, $d_{p_{eq}} / H$ continuously increases with increasing $Re$. With the increase of $N_p$, the closely arranged staggered particle trains evolve into five distinct migration Regimes. We explain the conditions for the formation of each Regime and explore the mechanisms of their interconversion. The findings of this study contribute to a better understanding of the self-organization process of deformable particles in channel flow.

Characterizing a device for easy simulation of compression waves induced by trains passing through tunnels

When a high-speed train enters a tunnel, an initial compression wave (ICW) is generated, which radiates out as it propagates lengthways through the tunnel to the exit, forming an uncomfortable micro-pressure wave (MPW). The aim of this research is to develop a scaled device to quickly simulate this aerodynamic phenomenon. Our device achieves this by using the instantaneous release of high-pressure air in the chamber. In the first part of the paper, the reliability of this device is verified by various methods, including an airtightness check, calibration of transducers, and repeatability experiments. Next, the mapping of the parameters of the device to engineering values is discussed. The propagation process of the ICW and the pressure fluctuations in the tunnel are then analyzed, and the discussion centers around a control variable case. Finally, the MPW generated near the tunnel exit is explored and acoustically evaluated. It is found that the initial pressure in the chamber, the opening voltage, and the number of solenoid valves in the experiment can be mapped to the train speed, the characteristic length of train nose, and the blockage ratio, respectively. When the pressure amplitude of the ICW is higher, there will be a certain steepening phenomenon in the propagation process. The pressure fluctuation cycle in the tunnel is calculated as 4× tunnel length/wave velocity, and the amplitude of fluctuation decays exponentially over the cycles. In most cases, the sound pressure level of MPWs near the tunnel exit exceeds the hearing threshold, based on the auditory properties of the human ear.

Wood jam characteristics influence but do not fully explain wood jam morphologic functions

In-stream wood jams alter their surrounding channel morphology, thus setting riverscape morphology and ecosystem function. While wood jams clearly scour pools, retain sediment, and influence bank erosion, there is a lack of observational evidence of how wood jam characteristics themselves control morphologic effects. Here, I analyzed field observations of hundreds of wood jams to test the hypothesis that wood jam characteristics can predict local morphologic effects such as sediment retention, bar forcing, and pool scour. I found mixed support for this hypothesis: While jam characteristics such as porosity, channel blockage ratio, thalweg occupation, and having rootwads and multiple trunks significantly predicted morphologic effect occurrence and magnitude, they only explained a small portion of the variance in those morphologic effects. While wood jam characteristics are relevant in controlling their overall morphologic functions, those functions are both inherently variable and likely affected by numerous other factors, such as reach-scale topography, the sediment transport capacity to supply ratio, and interactions with surrounding wood and vegetation. Wood function restoration may be more effective if it targets reach-scale objectives across dynamic wood jam assemblages, instead of individual jams.

Predictive Model for Cell Positioning during Periodic Lateral Migration in Spiral Microchannels.

The periodic lateral migration of submicrometer cells is the primary factor leading to low precision in a spiral microchannel during cell isolation. In this study, a mathematical predictive model (PM) is derived for the lateral position of cells during the periodic lateral migration process. We analyze the relationship of migration period, migration width, and starting point of lateral migration with microchannel structure and flow conditions and determine the empirical coefficients in PM. Results indicate that the aspect ratio of the microchannel and the Reynolds number (Re) are key factors that influence the periodicity of the cell lateral migration. The lateral migration width is jointly affected by Re, the cell blockage ratio, and the microchannel curvature radius. The inlet structure of the microchannel and the ratio of the cell sample to the sheath flow rate are critical parameters for regulating the initial position. Moreover, the structure of the pressure field at the inlet constrains the distribution range of the starting point of the lateral migration. Regardless of whether the particles/cells undergo 0.5, 1, or multiple lateral migration cycles, the lateral positions predicted by PM align well with the experimental observations, thus verifying the accuracy of PM. This research helps to elucidate the characteristics of periodic lateral migration of cells in spiral microchannels and can provide practical guidance for the development and optimization of miniature spiral microchannel chips for precise cell isolation.

Flow features induced by a rod-shaped microswimmer and its swimming efficiency: A two-dimensional numerical study

Abstract The swimming performance of rod-shaped microswimmers in a channel was numerically investigated using the two-dimensional lattice Boltzmann method (LBM). We considered variable-length squirmer rods, assembled from circular squirmer models with self-propulsion mechanisms, and analyzed the effects of the Reynolds number (Re), aspect ratio (ε), squirmer-type factor (β) and blockage ratio (κ) on swimming efficiency (η) and power expenditure (P). The results show no significant difference in power expenditure between pushers (microswimmers propelled from the tail) and pullers (microswimmers propelled from the head) at the low Reynolds numbers adopted in this study. However, the swimming efficiency of pushers surpasses that of pullers. Moreover, as the degree of channel blockage increases (i.e., κ increases), the squirmer rod consumes more energy while swimming, and its swimming efficiency also increases, which is clearly reflected when ε ≤ 3. Notably, squirmer rods with a larger aspect ratio ε and a β value approaching 0 can achieve high swimming efficiency with lower power expenditure. The advantages of self-propelled microswimmers are manifested when ε > 4 and β = ±1, where the squirmer rod consumes less energy than a passive rod driven by an external field. These findings underscore the potential for designing more efficient microswimmers by carefully considering the interactions between the microswimmer geometry, propulsion mechanism and fluid dynamic environment.

Influences of blockage ratio and Reynolds number on the spatiotemporal dynamics around a rectangular prism

Particle image velocimetry is used to experimentally investigate the influence of blockage ratio (BR) and Reynolds number (Re) on the turbulent flow around a rectangular prism with depth-to thickness ratio of 3. The prism was selected because it falls within the intermediate regime where the turbulent dynamics is sensitive to the incoming boundary condition. The tested blockage ratios were 2.5%, 5%, and 10% at Reynold numbers of 3000 and 7500. The results are analyzed in terms of the mean flow, turbulent kinetic energy (TKE), frequency spectra, reverse flow area, as well as spectral proper orthogonal decomposition (SPOD). The results indicate that as blockage ratio and/or Reynolds number increase, the tendency of reattachment of the separated shear layer onto the surface of the prism increases while the location of maximum TKE over the prism shifts toward the leading edge, indicating earlier transition of the separated shear layer from laminar to turbulence. For the cases without mean reattachment over the side faces of the prisms, the separated bubble over and downstream of the prism exhibits strong tendency of synchronization in terms of the instantaneous areas of the flow reversal, suggesting a global instability mechanism encompassing the entire prism. In cases with mean flow reattachment, conversely, the low-frequency flapping motion manifests over the prism. SPOD analysis further shows that the relevant shedding dynamics are captured in the first mode and the von Kármán shedding structures have the highest energy.

Hydrodynamic response characteristics of curved shape trash intercepting net under wave–current combined conditions

Under the influence of waves and ocean currents, the mesh panels of trash nets at nuclear power plants exhibit a curved shape. The combined action of waves and currents creates a Doppler effect that significantly influences the hydrodynamic response of these nets. This paper used OpenFOAM to establish a porous media macroscopic computational fluid dynamics model for analyzing the forces on curved trash nets. Wave–current combined conditions were simulated by introducing a uniform current in the direction of wave propagation. Forces on the nets under wave–current combined conditions were analyzed and compared with forces under separate uniform current and wave conditions. The results indicate that wave run-up on the nets is more significant under wave–current combined conditions than under wave action alone. The dimensionless horizontal force decreases more rapidly with increasing wave steepness (kA) and wave number (kd) under combined conditions than with linear superposition. Specifically, the rate of increase in dimensionless horizontal force with current speed, at the same blockage ratio, is about twice that of linear superposition. Additionally, the tension in the main cable of the nets is 17% higher under combined conditions than with linear superposition.

Experimental study of fuel distribution and combustion characteristics under subatmospheric pressure in an afterburner

The fuel distribution and ignition characteristics of an afterburner with typical components under subatmospheric inlet conditions are important references for improving the performance of the afterburner at high flight altitudes. In this work, lean ignition limits, outlet temperature distributions, fuel droplet size distributions and flame propagation processes in the afterburner were obtained experimentally. The results show that with increasing fuel injection angle, the fuel atomization characteristics improve, but the flame intensity fluctuation increases, and the ignition performance deteriorates; thus, a proper ratio of liquid-phase fuel to vapor-phase fuel is one of the key elements for successful ignition. On the one hand, the increased stabilizer blockage ratio results in a localized flow velocity increase near the trailing edge of the stabilizer, which effectively promotes fuel atomization in the shear layer, resulting in a fuel droplet size reduction of 25–30 μm. On the other hand, the extent of the recirculation zone increases, and a large low-pressure and low-turbulence recirculation zone is not conducive to fuel atomization in the flow direction. During the ignition process in an afterburner with all the typical components, the flame kernel first propagates along the flow direction for a certain distance and then propagates and anchors toward the shear layer. At subatmospheric pressures, the decrease in the intensity of the combustion reaction causes a reduction in the heat released by combustion, and the fuel droplet size increases by 10–25 μm, which requires more heat for evaporation. Therefore, the flame propagates an increased distance along the flow as the pressure decreases. Furthermore, the difficulty of ignition increases, and the ignition equivalence ratio increases by 0.1–0.15.

Numerical and experimental analysis of structural optimization and flow resistance effect of safety barrier based on a pump device

The safety barrier is often positioned at the entrance of the inlet passage in large and medium-sized low-lift pump stations, to ensure the safety of people and animals. To elucidate the blocking effect of the safety barrier and its influence mechanism on the internal flow of the inlet passage, numerical simulation combined with the physical model test were employed to investigate the impact of the cross-section and bar spacing of the safety barrier on the head loss, and the impact mechanism was clarified. The results showed that the optimal cross-section form of the safety barrier was found to be circular from the standpoint of head loss. When the blockage ratio of the safety barrier exceeds 0.3; prompt clearance of the blockage is recommended.

Experimental Optimization of the Propeller Turbine Performance Using the Response Surface Methodology

The growing global energy demand necessitates a shift towards sustainable sources to mitigate environmental issues and ensure energy security. This work explores the design and optimization of propeller-type hydrokinetic turbines to efficiently harness renewable energy from water currents. Through experimental testing and regression modeling, the research aimed to maximize the power coefficient (Cp) by determining the optimal values of the number of blades (Z) and the turbine diameter to hub diameter ratio (d/D). By correcting for experimental biases, the study elucidates the importance of factors such as the blockage ratio and turbine configuration on its performance. A second-order polynomial regression model, which was validated through analysis of variance, determined that when Z and d/D were set at 4 and 0.15, respectively, the optimal value for Cp was 53.62%. These findings provide valuable insights for optimizing hydrokinetic turbine efficiency, contributing to the advancement of renewable energy technologies.

Effects of branched tube on pressure waves in the hyperloop system: An experimental study

In this study, we experimentally investigated the aerodynamic characteristics of the Hyperloop with branch tube, an important applicational situation. Experiments were performed considering two velocities (258.6 and 295.8 m/s) and five branched angles (θ = 30°–150°) using 8.75 cm of scaled pod model (blockage ratio = 0.34). The leading shock waves LSW1 and LSW2 generated in front of the pod model were measured, and their intensity was analyzed before, on, and after the branching. The intensity of LSW1 and LSW2 at the straight tube before branching was the same as that without branching. LSW1 and LSW2 were divided by branching and propagated to the branched tube, where their intensity decreased to branched shock waves BSW1 and BSW2, respectively. The degree of decrease in BSW1 was linear as θ increased, whereas BSW2 decreased as θ and speed of the pod model increased when θ ≤ 90° and was nearly constant at 0.80 when θ ≥ 120°. The pressure characteristics near the branching were non-axisymmetric and became axisymmetric as it moved forward through the branching when x/lt ≥ 0.66. When LSW1 and LSW2 passed through the branching and were propagated as transmitted shock waves TSW1 and TSW2 after branching, their intensity decreased to approximately 86% and 91%, respectively, and was not significantly affected by the pod speed and θ.

Numerical and experimental investigation on the operating characteristics of fan-shaped pulse detonation combustor

The internal flow channel of a turbine engine is typically annular. When circular pulse detonation combustors (PDCs) are installed in this channel, there is a problem with low section utilization rates. To solve this problem, a single-tube fan-shaped PDC test system was developed. The effects of ignition distance on the operating characteristics of the fan-shaped PDC using air and gasoline under different frequencies were studied through both experiment and 3-D numerical simulation. Numerical simulation was also used to investigate the formation and propagation characteristics of detonation waves. The results show that the fan-shaped PDC can operate stably at frequencies ranging from 5 to 25 Hz when the ignition distance is either 2.30 or 2.70 times the equivalent circle diameter from the thrust wall, and it is found to be better to ignite at a distance of 2.30 times the equivalent circle diameter. The blockage ratio of the lower arc surface is larger than that of the other surfaces. This results in more intense collision and reflection. A larger local high pressure area forms near the lower arc surface, which is conducive to the formation of detonation waves. However, the larger blockage ratio makes the flow loss larger, which weakens the intensity of the pressure waves near the lower arc surface. The detonation waves in the fan-shaped PDC travel closer to the upper arc surfaces.

Numerical investigation of premixed syngas/air flame evolution in a closed duct with tulip flame formation

In this study, the dynamic behavior of the premixed syngas/air flames in enclosed ducts with obstacles at the blockage ratio of 0.5, as well as without obstacles, was studied via large eddy simulation and the turbulent flame speed closure model. The hydrogen volume fraction (hydrogen content in fuel) was set to 50 %. Results indicate that the simulation reproduced the flame shapes, flame speed and explosion overpressure observed in the experiments. In cases without obstacles, a “tulip” flame with a tulip cusp can be seen, and secondary cusps emerge on tulip lips due to the high-pressure zone ahead of “tulip” flame lips, leading to in a distorted “tulip” flame. In cases with obstacles, the flame develops hemispherical and finger shapes upstream of the obstacles and evolves into a “tulip” flame downstream of the obstacles due to vortices and adverse pressure gradients. The alteration of the flow direction within the unburned and burned zones results in intricate flame shapes. Flame speed and overpressure show a close relationship and exhibit oscillations following the generation of the “tulip” flame. Typically, the velocity, pressure and flow fields adjacent to the flame front can affect dynamic behaviors of premixed syngas/air flames.

Numerical investigation of fluid flow and heat transfer of a nanofluid around two circular cylinders arranged in tandem in horizontal duct

In this study, two-dimensional unsteady laminar convective heat transfer from two isothermal cylinders arranged in tandem in horizontal duct has been numerically investigated. The numerical study is performed by solving the governing equations (continuity and momentum) and energy equations using a finite volume-based code ANSYS Fluent. The present study was conducted using nano sized copper particles suspended in water. The Prandtl number Pr of the resulting suspension being equal to 7. The range of solid volume fractions studied is and the flow Reynolds number is equal to 100.The spacing ratio of the two cylinders was varied from 2 to 5 while the blockage ratio was kept constant β=0.25. A detailed discussion has been provided regarding the variation of flow structure and the characteristics of flow, including total drag and lift coefficients, as a function of the dimensionless parametersIn order to visualize the flow and heat transport, streamlines, vorticity contours and isotherms were generated. In addition, the local and average Nusselt numbers for the upstream and downstream cylinders are calculated. The results demonstrate that the force coefficients, the wake structure behind the cylinders, and the Nusselt number are significantly influenced by the value of the spacing ratio and the volume fractions of nanoparticles. The results demonstrate a significant enhancement in heat transfer efficiency relative to the base fluid. The aforementioned improvement is more pronounced in the case of higher gap ratios and higher nanoparticle volume fractions.

Investigation of temperature field variations induced by the air thermodynamic behavior when trains pass through a high-speed railway tunnel in cold regions

High-speed railway tunnels in the cold region, whose numbers are increasing, are widely exposed to the threat of frost damage caused by extremely negative temperatures. The operation of high-speed trains has made this problem even more pronounced. But there are fewer studies focusing on the dynamic changes in temperature during train operation. In this paper, the air thermodynamic behavior of trains passing through a tunnel and its consequences were investigated with the help of the CFD method. In numerical simulations, conditions of different natural airflows, different train speeds, different blockage ratios, as well as two trains intersecting in the tunnel were involved. The following valuable results were obtained. In cold environments, train-induced pressure wave effects will affect the air thermodynamic behavior, but the overall trend in air temperature is mainly influenced by the heat transfer between cold and warm air. The high-speed train will lead to massive cold air being carried into the tunnel and some warm air inside being pushed out. Heat transfer between cold and warm air will cause a significant decrease in tunnel air temperature. This air thermodynamic behavior is particularly prominent in the case of large blockage ratios. When there are same-direction natural airflows, they will be coupled with train-induced airflows, causing a greater decrease in tunnel air temperature. In contrast, opposite-direction natural airflows can reduce the negative effects of the train. Taking the case of opposite-direction natural airflow velocity of 5 m/s as an example, the temperature changes of the three cross-sections are only 16.7 %, 14.8 %, and 42.1 % of those in the case of no natural airflow. Whatever the direction of natural airflows, coupling effects between them and train-induced airflows will be more significant as the natural airflow speed increases. Greater train speed means more cold air entering the tunnel and stronger heat transfer between cold and warm air, causing a more significant temperature decrease. When two trains intersect through the tunnel, airflows caused by them will be coupled. As a result, only a little air enters the tunnel from the entrance and exit, and the heat transfer between air with different temperatures is weak. In this case, the air temperature doesn't decrease but slightly increases as the air is compressed.

The Blockage Effect on Resistance Coefficients Estimation for AUVs with Different Configurations in the Towing Tank

When a resistance test of an underwater vehicle model is conducted in a towing tank, the blockage effect will inevitably occur, particularly since the experimental model is relatively large. This paper investigates the estimation of resistance coefficients for an Axisymmetrical Rotary Body Underwater Vehicle (ARBUV) and a Blended Wing Body Underwater Vehicle (BWBUV). The Computational Fluid Dynamics (CFD) method is employed to predict the resistance of Autonomous Underwater Vehicles (AUVs). In order to quantify the blockage effect on the resistance coefficients of AUVs with different configurations, the resistance coefficients of AUVs are calculated in the infinite domain and finite domain under various blockage ratios. Through analysis of the resistance results, velocity distribution, and pressure distribution, the action law of the blockage effect is provided. It indicates that blockage effects have a greater influence on the pressure resistance for ARBUV. Surprisingly, the resistance coefficients of BWBUV are less affected, though it is closer to the sidewalls. It suggests that the blockage ratio of ARBUV and BWBUV should be separately smaller than 0.375% and 2.5% in the towing tank test. The towing tank experiments satisfy the blocking ratio with a Reynolds number greater than 107, which saturates the blocking effect and further reduces the effect on the drag coefficient.

Experimental investigation into effects of combustor structure on characteristics of rotating detonation of cracked kerosene gas

This study examines the influence of the structure of the combustor on the propagation of rotating detonation waves (RDWs) of cracked kerosene gas (CKG) by using oxygen-rich air, with mass fractions of oxygen of 36% and 48%, as the oxidant while maintaining stable values of the state parameters of CKG. The experimental results showed that the structure of the combustor played a key role in the initiation and stable propagation of CKG, and suitable values of its width and the width of its outlet promoted the stable self-sustained propagation of the RDWs. Combustors of 8 and 14 mm width failed to initiate with 36% oxygen-rich air and without blockage ratio. In the combustors of 20 and 26 mm width, as the blockage ratio increased, the modes of propagation of the RDW included a single stable RDW, intermittent single RDW, and four, six, and eight counter-rotating RDWs. With the further increase in the blockage ratio, the reflected shock wave at the end of the combustor was enhanced, resulting in an increase in the number of RDW wave heads. As a result, the height of the fresh fuel layer was decreased, the mixing time was decreased and led to a decrease in the RDW velocity. The increase in the width of the combustor was conducive to the radial and axial diffusion of fuel and oxidizer in the combustor, which led to an obvious increase in the propagation velocity of RDW. In the 26 mm width combustor, the maximum RDW velocity is 1769 m/s.

Enhancement of the subcritical boiling heat transfer in microchannels by a flow-induced vibrating cylinder

The flow boiling heat transfer in microchannels has been extensively used in engineering due to its high heat dissipation with a small temperature difference. This study employs a hybrid method to numerically investigate the effects of a flow-induced vibrating cylinder on enhancing the subcritical boiling heat transfer in microchannels. The hybrid approach integrates the pseudopotential multiphase lattice Boltzmann method for modeling unsteady flows, the finite difference method for solving the heat transfer equation, and the immersed boundary method for handling the boundary condition at the fluid–cylinder interface. Flow boiling simulations in the microchannel are performed for three setups: a smooth vertical channel, a vertical channel with a stationary cylinder, and a vertical channel with a flexibly supported cylinder. Simulations have been conducted by varying the Reynolds number based on the diameter of the cylinder (Red) from 35 to 333.3, the dimensionless boiling number (Bo) from 0.001 84 to 0.045 97, and blockage ratio (BR) of 3.0, 4.0, and 5.0. It is found that the vortical wake of the cylinder is important in enhancing the heat transfer in microchannels, which is quantified by the (Red). Specifically, when Red<48.0, both stationary and flexibly supported cylinders have almost the same effect on heat transfer during the flow boiling process, as there is no vortex shedding from both cylinders; when 48.0≤Red<68.2, the flexibly supported cylinder achieved higher enhancement than the stationary cylinder, which is due to the vortical wake generated by the flow-induced vibration in a subcritical Reynolds number regime; when 68.2≤Red, both stationary and flexibly supported cylinders have comparable effect on the rates of heat transfer, because both cylinders generate similar vortical wakes. Flow field analysis indicates that the disturbance due to the vortex wakes on the thermal boundary and/or the vapor insulation layer is the mechanism of the heat transfer enhancement in channels.

Wake flow behind a transversely rotating sphere confined in a pipe at low Reynolds numbers

Direct numerical simulations are performed to investigate the flow past a transversely rotating sphere confined in a pipe. Three sphere diameters of d=0.2D, 0.5D, and 0.8D (D is the pipe diameter) and sphere Reynolds numbers (based on the sphere cross-sectional mean velocity and d) of Res=250–500 are considered. The simulation results highlight the combined effects of the blockage ratio (BR=d/D) and the nondimensionalized rotation rate Ω in the range of 0.2–1.2 on the wake flow. For each BR, with increasing Res and Ω, the wake flow undergoes a transition of the flow pattern from steady symmetry and unsteady symmetry to unsteady asymmetry. For BR=0.2, the variation in flow behaviors with Ω is similar to those reported in the previous studies on a transversely rotating sphere subjected to a uniform flow. With increasing BR from 0.2 to 0.5, the unsteady asymmetric wake flow is characterized by distorted near-wake vortex rings and a series of staggered inward rolled-up vortex arcs on the double streamwise vortex threads, which results in a low-frequency modulation of the unsteady wake flow. These rolled-up vortex arcs are connected with downstream quasi-streamwise vortices and form hairpin-like vortices. Dynamic Mode Decomposition (DMD) analysis shows that the distorted near-wake vortex rings are associated with the antisymmetric DMD mode at the adjacent frequency around the symmetric primary DMD mode. With BR=0.8, there is a drastic increase in the sphere's force coefficients. A more complex wake flow behavior is found due to a strong interaction between the wake flow and the near-pipe-wall flow. At Ω=1.2, dominant asymmetric flow structures are characterized by impingement of the vortex filaments. The low-frequency modulation of these wake structures is also analyzed using the DMD analysis.

An experimental study on the flame behaviors of H2/CO/Air mixtures in closed tube with varying number of obstacles

In order to investigate the flame behavior of syngas/air mixtures after leakage in industrial scenarios. A series of fence-type obstacles with a blockage ratio of 0.3 were installed in a closed tube to simulate common blockage scenarios. The stoichiometric mixtures of H2/CO/Air with hydrogen fractions ranging from 10 % to 50 % were used to simulate typical syngas compositions. Results indicate that the increase in hydrogen fractions and the number of obstacles can enhance flame acceleration and oscillation downstream of obstacles. The flame inverts into the tulip shape after it passes the obstacle area, and then the distorted “tulip” flame appears. The obstacles number has no influence on the instant of the planar flame formation, because the flow competition initiates when the flame passes the first obstacle channel. However, the initial instant of the first “tulip” distortion decrease with the increasing obstacle number. The “tulip” flame is a hydrodynamic phenomenon, while the distortion of the “tulip” flame is related to pressure waves. At higher hydrogen fractions, the obstacle number increases the maximum overpressure more significantly. In practical scenarios, it is advisable to limit the number of obstacles as much as possible and prevent syngas leaks with higher hydrogen fractions.