Axis-switching Phenomenon Research Articles

Study on the impact of different hole shapes on liquefied gas leakage behavior

Accidental leakage of liquefied gas is a common occurrence during its storage, transportation, and usage. The shape of the leakage holes varies due to different causative factors. In this paper, we have established an experimental setup using R134a as the medium to simulate liquefied gas leakage. Different nozzle shapes are used to simulate the effect of various leakage hole shapes on the release process. The results indicate that, when the hole area (A) is constant, the discharge coefficient (Cd(exp)) decreases in the order of circular, square, and triangular holes. Simultaneously, based on dimensional analysis, we propose an empirical formula to predict the Cd(pre) for both circular and non-circular hole leakage. Notably, non-circular holes exhibit an axis-switching phenomenon during flash vaporization spray, leading to an asymmetric structure in the spray cone angle (θ) of triangular holes. The spray area of circular holes displays significantly larger lowest temperature and low-temperature regions compared to non-circular holes.

A comparative analysis of internal flow and spray characteristics in triangular orifices with diesel and biodiesel

This paper presents an inquiry into the internal flow and spray behavior of diesel and biodiesel in a triangular orifice, using experimental and numerical methods. The inner flow was analyzed through the implementation of Large Eddy Simulation model. Furthermore, two high-speed cameras were utilized to capture spray images of the major and minor axes of the triangle-shaped nozzle simultaneously. The investigation revealed that, in comparison to diesel, biodiesel exhibited a higher discharge coefficient. Additionally, the vorticity magnitudes and turbulence vortex structures for biodiesel were consistently lower than those for diesel. The use of biodiesel can hinder the occurrence of cavitation. Moreover, it was observed that the triangular spray cone angle displayed axis-switching phenomena for both fuels. The axis-switching phenomenon is suppressed by using biodiesel. The research also discovered that the triangular biodiesel spray has a longer spray tip penetration and a smaller angle in all view planes. This could be attributed to the higher viscosity and surface tension of biodiesel, as well as the inhibition of the spray axis-switching during the injection, leading to an increase in the spray tip penetration and a decrease in the spray cone angle for biodiesel.

Experimental study on flow and turbulence characteristics of jet impinging on cylinder using three-dimensional Lagrangian particle tracking velocimetry

When a round jet impinges on a convex cylindrical surface, complex three-dimensional (3D) flow structures occur, accompanied by the Coanda effect. To characterize the flow and turbulence properties of the general system, ensemble averages of 3D Lagrangian particle tracking velocimetry measurements were taken. The radial bin-averaging method was used in post-processing the tracked particles and corresponding instantaneous velocity vectors to generate appropriate ensemble-averaged statistics. Two impinging angles were selected, and at a fixed Reynolds number, the ensemble-averaged volumetric velocity field and turbulent stress tensor components were measured. The flow and turbulence characteristics of the impinging jet on the cylinder were notably different based on the impinging angle, especially in the downstream region. Surprisingly, the attached wall jet with a half-elliptic shape was abruptly thickened in the wall-normal direction, similar to the axis switching phenomenon observed in elliptic jets in the case of oblique impingement. In the jet-impinging region, the flow spread in all directions with high mean vorticity values. With the development of a 3D curved wall jet, both the Coanda effect and centrifugal force played a significant role in the flow behavior. A notable feature of the self-preserving region was the similarity of mean velocity profiles with scaling by the maximum velocity and the jet half-width for both impinging angle cases. Local isotropy of turbulent normal stresses was observed in this region, supporting the existence of self-preservation in the 3D curved wall jet. The volumetric ensemble-averaged Reynolds stress tensor revealed strong inhomogeneous turbulence in the boundary layer region and the curvature effect on the Reynolds shear stress in the free shear layer.

Experimental study on the combustion characteristics of square fire

In this paper, the combustion characteristics of square fire are studied experimentally, with emphasis on the changes in flame structure during the flow evolution. A series of fire tests with different fuel types, heat release rates, and fire scales are performed. The time-averaged temperature and velocity profiles and the flame length are measured and discussed. Experimental results show that as the square fire progresses downstream from the flame base, its cross-sectional shape undergoes a square-to-round transition. In this process, the self-induced axis-switching phenomenon intensifies the square fire's turbulence, manifested as more significant axial and radial temperature fluctuations than the round fire. This enhanced turbulent mixing promotes flame burning, resulting in a greater axial temperature and velocity of the square fire than the round fire. At different fire scales, the critical height at which a square fire completes the axis-switching first increases and then slows down with increasing heat release rate, which can be well correlated by the dimensionless heat release rate normalized by the side length. Experimental data verify that Quintiere and Grove's classic model can well normalize the flame lengths of square fires at different scales. A square fire's three-dimensional flow and enhanced turbulent mixing cause a higher constant representing the near-field entrainment strength than a round fire.

Studies of Jet A1 Fuel Atomization Through Non Circular Orifices


 
 
 The performance of the liquid rocket engine depends on the atomization behavior of the fluid being injected into the combustion chamber. Generally, a plain injector with a circular orifice has been used in the injector, but it has the disadvantage of having a low spray cone angle. The breakup length, mean droplet diameter, and Sauter mean diameter is also higher. Thus, to overcome these drawbacks, non-circular orifices have been utilized in the present study. The shapes used for non-circular orifices are semi-circular and plus. The results obtained with the non-circular orifice is compared with the circular orifices of the same area ratio. The working fluid used for the studies is Jet A1 fuel. Studies were also conducted with different L/D ratios by choosing an effective orifice length to reduce the upstream losses. The axis-switching phenomena were observed with the semi-circular as well as with the plus jets. The mean droplet size of the circular jets was more prominent compared to non-circular jets, and the Sauter mean diameter of non-circular jets droplets was smaller than that of the circular jet droplet. The spray cone angle has increased by 290% for plus jets and 30% for semi-circular jets compared to circular jets.
 
 

Reacting flow characteristics based on the axis-switching phenomenon in a baffled micro combustor with rotated noncircular holes for micro-thermophotovoltaic system

• The geometric features related to the axis-switching phenomenon are numerically investigated for a multihole baffled micro combustor. • In the combustor of noncircular holes, secondary flows are more developed. • The flow mixing and combustion efficiency are improved by noncircular air holes. • The best thermal field for a combustion-based TPV system is obtained for baffles with 30°-rotated square holes and 15°-rotated triangular holes. • The emitter efficiency for TPV applications is better than the swirling flow combustor. For a thermophotovoltaic (TPV) generator, a combustor design for strengthening the axis-switching phenomenon is explored. Various simulations based on a Reynolds stress model and detailed chemical mechanism of GRI 3.0 are performed for methane (CH 4 )–air flames in a multihole baffled combustor. The reacting flow fields are investigated with the baffle plates of rotated square and triangular holes. The spreading and merging of multiple air jets past the baffle plate are significantly affected by rotating noncircular air holes. Considering the crossover location changes of the jet half-width, the air jets have a flow structure that quickly generates the axis-switching phenomenon. Compared with the baffled combustor of circular air holes, the center recirculation zone in the combustor of noncircular holes is enlarged by approximately 200% with a hole rotation. As the hole rotation increases, secondary flows become more complicated and the merging of air jets is quickly finished. Based on these flow structures, the region with the stoichiometric condition is observed in various forms of hexagonal, star, circular, and flower shapes. As a result, the flammable region and combustion efficiency are considerably increased. The flame lengths are roughly evaluated as three times the mixing lengths. From the viewpoint of a heat emitter for the TPV application, the heat transfer on the combustion chamber wall is discussed. Compared with the combustor with circular air holes, the combustor with noncircular air holes shows a 5% increase in flammable region and a 5.9% improvement in combustion efficiency. For a combustion-based TPV system, the best uniformity of wall temperature is observed for baffles with 30°-rotated square holes and 15°-rotated triangular holes and the highest mean wall temperatures are obtained when the flame length is approximately 1/3 of the combustor length.

Morphological characteristics and flashing mechanism of superheated liquid jets released from rectangular breaches

The leakage of liquefied gases such as liquefied hydrocarbons and liquid chlorine is usually accompanied by an intense phase transition that results in two-phase release. This two-phase release will lead to fire, explosion, toxic diffusion and other major dangerous accidents, seriously endangering the safety of personnel and ecological environment, resulting in inestimable losses. To deepen the understanding of such accidents, a 20L tank was used to simulate the accidental release of superheated liquid and study its accident behavior. This work simulated different breaches by using different shapes of nozzles with equal cross-sectional area and more focused on rectangular nozzles. Besides, the influence of initial temperature (110–130 °C) and pressure (6–16 bar) was also taken into account. A high-speed camera was used to record the external morphological characteristics of the superheated liquid jets released from the nozzles. The jet angle and half-width were extracted as the quantitative characterization of the external morphology by threshold processing algorithm. The results revealed that the rectangular nozzle jet (RNJ) has a different external morphology from the circular nozzle jet (CNJ) due to the presence of vortex and axis-switching phenomena. Aspect ratio plays an important role in the determination of external morphology of the RNJ and there is a critical aspect ratio AR = 3. In addition, this study also demonstrates that the rectangular nozzle has a different flashing mechanism from the circular nozzle, which is the underlying reason for the different external morphologies. In summary, compared to the traditional circular breach, rectangular breach has a significant promotion effect on the jet flashing, and the industrial medium released from the slit breach will have a greater impact range, resulting in more serious consequences of accidents.

Flow fields around spanwise-inclined elliptical jets in supersonic crossflow

Motivated by favorable effects in separation control with air-jet vortex generators in aerospace applications, we performed implicit large-eddy simulations to analyze the flow physics of spanwise-inclined elliptical jets in supersonic crossflow and reveal the influence of aspect ratio. Orifices with similar hydraulic diameters and aspect ratios of 0.5, 1.0, and 2.0 were studied at Mach number M=2.5 and momentum-thickness Reynolds number Reθ=7000. The jet injection results in the formation of asymmetric flow features (bow and barrel shocks, upstream and downstream separation regions, and vortical structures), which are qualitatively similar for all cases. Compared with the more commonly-studied wall-normal injection, the axis-switching phenomenon and its effects are very mild for spanwise-inclined injection. For the low-aspect-ratio orifice, the clockwise-rotating major vortex strengthens and vice versa for the high-aspect-ratio orifice. Flow penetration increases with aspect ratio; however, the influence of the injection is limited within the boundary layer and the outer layer is undisturbed. In the far field, the enhanced momentum transfer makes the boundary layer more resistant to separation for all orifices. Combined with the amplified vorticity for elliptical cases, elliptical jet orifices become more effective for separation control purposes than circular orifices.

Aspect Ratio Driven Relationship between Nozzle Internal Flow and Supersonic Jet Mixing

This work attempts to connect internal flow to the exit flow and supersonic jet mixing in rectangular nozzles with low to high aspect ratios (AR). A series of low and high aspect ratio rectangular nozzles (design Mach number = 1.5) with sharp throats are numerically investigated using steady state Reynolds-averaged Navier−Stokes (RANS) computational fluid dynamics (CFD) with k-omega shear stress transport (SST) turbulence model. The numerical shadowgraph reveals stronger shocks at low ARs which become weaker with increasing AR due to less flow turning at the throat. Stronger shocks cause more aggressive gradients in the boundary layer resulting in higher wall shear stresses at the throat for low ARs. The boundary layer becomes thick at low ARs creating more aerodynamic blockage. The boundary layer exiting the nozzle transforms into a shear layer and grows thicker in the high AR nozzle with a smaller potential core length. The variation in the boundary layer growth on the minor and major axis is explained and its growth downstream the throat has a significant role in nozzle exit flow characteristics. The loss mechanism throughout the flow is shown as the entropy generated due to viscous dissipation and accounts for supersonic jet mixing. Axis switching phenomenon is also addressed by analyzing the streamwise vorticity fields at various locations downstream from the nozzle exit.

Inflow characteristics for generating axis-switching phenomenon of heated rectangular jets

Flow characteristics due to the axis-switching phenomenon are numerically investigated for heated rectangular jets with typical inlet conditions and three aspect ratios (AR), namely 1.0, 1.5, and 2.0. To examine various inlets and their relation to the axis-switching flow, an inflow generator is newly devised, wherein jet flows from an orifice plate and a long pipe nozzle can be realized. Depending on the inlet conditions, the 45° and 90° axis-switching phenomena for the rectangular jet are observed to appear differently. As the aspect ratio increases and jet temperature decreases, the axis-switching positions are delayed downstream. It is observed that the strong and weak states of the axis-switching flows can be interpreted by the crossover locations of the jet half-widths and the saddle-shaped velocity profile is not the only main factor for axis-switching flow. As the jet temperature increases, a well-mixed state is quickly obtained, and the mixing performance of the square jet is better than that of the rectangular jet. For both isothermal and heated jets, the flow mixing is improved by the axis-switching flow. Various analyses are attempted to find the specific inlet structure for the axis-switching flow. From the results, the special features for inflow criterion producing axis-switching flow can be explained by factors such as the deformation parameter, interrelations between shear strain and normal rates, turbulence-driven and geometry-driven streamwise vortices, and normal Reynolds stresses.

Axis-Switching Behavior of Liquid Jets Issued from Non-Circular Nozzles Under Low-Intermediate Pressure

HighlightsThe flow behavior of water jets discharged from different orifices was investigated.High-speed photography (HSP) was used to obtain surface structures and spread characteristics of water jets.The deformation process in axis switching related to the corner vortices effect of non-circular jets was researched by numerical simulation.The axis switching of non-circular jets enhances entrainment ability of the jet.ABSTRACT. Low-intermediate pressure sprinkler irrigation systems are important research topics in the field of water-saving irrigation. Non-circular nozzles improve spray uniformity at lower pressures and are key components of sprinkler irrigation systems. In this article, the behavior of discharged water jets from nozzles with circular, square, and equilateral triangular orifices designed with the same flow rate was investigated. High-speed photography (HSP) was used to capture jet characteristics in the near field (z<20D). The largest spread angle was obtained for the square jet, which was on average 37% larger than that of the circular jet. In addition, numerical simulations were performed to analyze the axis-switching process using the large-eddy simulation (LES) method and the coupled level-set and volume of fluid (CLSVOF) method. The axis-switching phenomenon was observed in non-circular jets, in which surrounding air mixed with the jet and promoted the formation of thin diaphragm structures. The deformation process that occurs in axis switching is described according to the simulated vorticity and velocity fields. The research results suggest the axis-switching phenomenon is induced by corner vortex motions produced by the polygonal orifice, which accelerate the decay of the axial velocity and increase the jet entrainment rate. Thus, the effect of corner vortices should be considered in the design of polygonal nozzles. Keywords: Axis switching, High-speed photography, Liquid jet, Low-intermediate pressure sprinkler irrigation, Non-circular nozzle, Numerical simulation.

On the radiative heat loss and axis-switching phenomena of a decaying laser spark

A three-dimensional numerical simulation of a decaying laser spark in gaseous nitrogen has been carried out in Cartesian co-ordinate. The simulation starts with the introduction of a laser pulse in the domain. Thermal equilibrium has been assumed throughout the numerical simulation involving the species N2, N, N+, e−. The boundary conditions are treated following characteristic property of the waves to ensure smooth transmission of the blast wave out of the computational domain. The previously unexplained axis-switching phenomenon of the breakdown region has been explained, and a qualitative comparison of the same with experimental schlieren images has been made. The total radiation loss, including the loss during the breakdown, has been calculated. The variation of inverse Bremsstrahlung radiation, black body radiation, and spectral radiation of atomic nitrogen with time have been shown separately. Additionally, the temporal variation of radiation intensity of atomic nitrogen over a wavelength range has been plotted. The total radiation loss has been found to be small compared to the deposited laser energy.

Experiment and Large-Eddy Simulation on Free Air Jets Issuing from a Rectangular Nozzle with Deflectors

The purpose of the present study was to establish a passive flow control method for a rectangular jet using two types of deflectors installed symmetrically inside a nozzle. This deflector in a rectangular nozzle generates the rectangular coaxial jets. The effect of the slant angle of the deflectors on the flow characteristics and the spread of the rectangular jet was investigated experimentally and by large-eddy simulation. The experiment and the numerical simulation were carried out at a Reynolds number of 9000. The rectangular jet with no deflectors generates a vortex ring from the nozzle exit. The vortex ring collapses in the downstream region and the outline of the jet changes from rectangular to diamond-shaped as a result of the axis-switching phenomenon. The rectangular jet with divergent and convergent deflectors shows particularly noticeable changes in the flow characteristics and vortical structures, as compared to the case with no deflectors. In the case of the rectangular jet with divergent deflectors (slant angle of α = 6°), minor axis spread is promoted more than major axis spread, and axis switching occurs closer to the nozzle exit than that in the case of no deflectors. The outline of the jet also changes from lateral rectangular to vertical rectangular as a result of axis switching. On the other hand, in the case of a rectangular jet with convergent deflectors (α = -6°), minor axis spread is suppressed more than major axis spread, and axis switching occurs farther from the nozzle exit than that in the case with no deflectors. The outline of the jet does not change until the downstream region. Therefore, the spread and the axis-switching location for the rectangular jet can be controlled by the deflectors inside the rectangular nozzle.

Dispersion of cryogenic hydrogen through high-aspect ratio nozzles

Liquid hydrogen is increasingly being used as a delivery and storage medium for stations that provide compressed gaseous hydrogen for fuel cell electric vehicles. In efforts to provide scientific justification for separation distances for liquid hydrogen infrastructure in fire codes, the dispersion characteristics of cryogenic hydrogen jets (50–64 K) from high aspect ratio nozzles have been measured at 3 and 5 barabs stagnation pressures. These nozzles are more characteristic of unintended leaks, which would be expected to be cracks, rather than conventional round nozzles. Spontaneous Raman scattering was used to measure the concentration and temperature field along the major and minor axes. Within the field of interrogation, the axis-switching phenomena was not observed, but rather a self-similar Gaussian-profile flow regime similar to room temperature or cryogenic hydrogen releases through round nozzles. The concentration decay rate and half-widths for the planar cryogenic jets were found to be nominally equivalent to that of round nozzle cryogenic hydrogen jets indicating a similar flammable envelope. The results from these experiments will be used to validate models for cryogenic hydrogen dispersion that will be used for simulations of alternative scenarios and quantitative risk assessment.

Influence of inlet vorticity and aspect ratio on axis-switching and mixing characteristics of heated rectangular jets

To investigate interactive characteristics between the inlet condition and axis-switching phenomenon, heated rectangular jets are numerically investigated for seven aspect ratios (AR = 1.0 − 6.0) with three jet temperatures of 300, 500, and 1000 K. The corresponding Reynolds number is 11,400 – 21,000. To examine the relative importance of ωθ and ωx on axis-switching, seven inlets are obtained by an inflow generator. For the flows of nozzle part, various geometry-driven and turbulence-driven vortices are observed. It is shown that the rotational directions of turbulence-driven vortices have the rotational direction hindering the axis-switching flow. By using the crossover location of the jet half-widths and the mixing length, the axis-switching condition depending on AR and jet temperature is explained. The crossover location is changed to the ωx-variation, which is approximately eight times as sensitive as the ωθ-variation. Based on the results of AR and temperature changes, the strong influence on axis-switching flow and mixing is confirmed for the ωx-change. Also, the heat transfer effect on mixing enhancement becomes strong for the weak axis-switching condition. As AR increases, the mixing performance decreases, but mixing enhancement of the axis-switching flow is confirmed for AR ≤ 4. Finally, to explain the ωx-variation related to the axis-switching mechanism, the ωx transport equations are analyzed by three terms of the Prandtl's first kind and the baroclinic torque. The roles of the vortex stretching and baroclinic torque terms are analyzed for the positive effect of the ωx-variation on the axis-switching phenomenon.

Numerical Modeling of Instability and Breakup of Elliptical Liquid Jets

Numerical simulations are performed to provide an in-depth insight into the effect of instabilities on liquid jets discharging from elliptical orifices. The axis-switching phenomenon and breakup are simulated and characterized under the effect of disturbances imposed at the nozzle exit. The simulations are based on the volume of fluid approach and an adaptive meshing. A range of orifice aspect ratios from 1 to 4 at the Rayleigh breakup regime is considered. The evolution of the jet cross section and axis switching under the influence of disturbances is compared with that of nonperturbed elliptical jets. It is found that the axis-switching repetition and breakup length exponentially decrease with the initial amplitude of disturbances. For a fixed amplitude, the optimum wavenumber responsible for minimum breakup length is observed to be dependent on ellipticity of the orifice. Moreover, it is found that the form of final breakup leads to elimination of the satellite droplets at the optimum wavenumbers, while the droplet size decreases and becomes more uniform.

밀도 차이가 있는 비원형 제트에 대한 축전환 현상 및 유동 특성 해석

밀도 차이가 있는 비원형 제트에 대해 축전환 현상과 혼합 특성이 수치 해석적으로 조사되었다. 공기 속으로 분사되는 원형, 사각형, 삼각형 제트에 대해서 수소, 메탄, 공기, 프로판, 네 개의 유체가 선택되었다. 등가 지름 기준의 레이놀즈수는 10,000으로 고정되었다. 축방향 속도 감쇠와 제트 반폭의 결과로부터 비원형 제트의 유동 혼합에 대한 밀도 차이의 영향이 검토되었다. 축전환 현상의 유동 구조에 대해서 와도 수송방정식의 생성항이 분석되었다. 제트 유체의 밀도에 의존해서 축전환 현상이 매우 다르게 영향을 받았다. 가벼운 제트에서 밀도 차이는 축전환 현상을 방해하지만 무거운 제트에서는 밀도 차이의 반대 효과가 얻어졌다.

Comparative study on interfacial oscillations of rectangular and elliptical liquid jets

The instability characteristics and flow structures of water jets injected from rectangular and elliptical nozzles with aspect ratios varying from 2 to 6 were experimentally studied and compared. Shadowgraph technique was employed for flow visualization, and structures on the liquid jet surface were captured using high speed photography. It was found that disturbances originating from the nozzle geometry initially perturbed the liquid column, and then, at high jet velocities, disturbances generated within the flow dominated the jet surface. It was also found that rectangular nozzles introduced more disturbances into the flow than the elliptical ones. The characteristic parameters of axis-switching phenomenon including wavelength, frequency, and amplitude were measured and compared. Axis-switching wavelength was found to increase linearly with Weber number. Also, the wavelengths of rectangular jets were longer than the elliptical jets. Further, the frequency of axis-switching was shown to be reduced with increase of both Weber number and aspect ratio. It was observed that the axis-switching amplitude increased monotonically, reached a peak, and then decreased gradually. It was also found that the axis-switching amplitude varied with Weber number. At lower values of Weber number, the rectangular nozzles had higher amplitude than the elliptical nozzles. However, at higher values of Weber number, this relation was reversed, and the elliptical nozzles had the higher axis-switching amplitudes. This reversal Weber number decreased with the orifice aspect ratio. The reversal Weber number for aspect ratio of 4 was about 289, and it had decreased to 144 for the aspect ratio of 6.

Wavelength and frequency of axis-switching phenomenon formed over rectangular and elliptical liquid jets

A theoretical and experimental study was performed to investigate the wavelength and frequency of axis-switching oscillations established over rectangular and elliptical liquid jets. Several injectors with aspect ratios ranging from 2 to 6 were manufactured for both rectangular and elliptical shapes. Shadowgraph technique was used for flow visualization and high speed photography was employed to capture the flow physics of the liquid jets. The theoretical model developed by Tadjfar and Jaberi (2019) was rewritten by looking at frequency analogous to the previous one for wavelength. The model rewrote the Rayleigh's classical analysis in terms of three segments identifying the influence of shape, aspect ratio, and Weber number. This model was modified to improve predictive accuracy by adding a correction term in terms of powers of aspect ratio. This time, instead of a constant power, a logarithmic function was used to evaluate the coefficients. The modified model improved the predictive accuracy of Rayleigh's model significantly. The results were analyzed from the viewpoint of frequency and wavelength.

Numerical modeling of aerosol deposition process

Aerosol Deposition (AD) method is an emerging coating process for deposition of ceramic particles for industrial applications such as MEMS, fuel cells, optical devices and radio frequency components. In this process, various parameters such as nozzle geometry, powder size and type, pressure inside the deposition chamber, and carrier gas flow rate have significant influence on the in-flight particle behavior before impact, and therefore, on the coating properties. In this study, a two-way coupled Eulerian-Lagrangian model is used to study the effects of gas flow rates and substrate location on the gas flow characteristics, bow shock near the substrate, and more importantly on the particle velocity and trajectory upon impact. The study is carried out with a rectangular sonic nozzle. To validate our simulations, locations of the Mach disks in highly under-expanded free-jet conditions are compared with the theoretical and experimental results in the literature. Two different computational geometries are utilized; a 2D planar and a quarter slice of 3D. It is found that, for the rectangular nozzle, the 3D geometry produces more accurate results and can capture the axis-switching phenomenon. Moreover, it is observed that the gas flow structure as well as the in-flight particle behavior obtained from 2D and 3D geometries are almost identical before the Mach disk. In addition, two different drag expressions are employed and it is shown that the influence of Mach and Knudsen numbers on particle behavior in vacuum condition is significant.