Numerical investigation of rarefied vortex loop formation due to shock wave diffraction with the use of rorticity
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Citations
Prediction and visualization of supersonic nozzle flows using OpenFOAM
Effects of bulk viscosity, vibrational energy, and rarefaction on flow and vorticity fields around simple bodies at hypersonic speeds
Atmosphere Re-Entry Simulation Using Direct Monte Carlo Method (DSMC)
Investigation on the Opposing Jet in the Hypersonic Rarefied Flow over a Vehicle Based on the DSMC Method
Pressure amplification effect of initial compression waves in circumferential cracks of high-speed railway tunnel linings
References
The secondary vortex rings of a supersonic underexpanded circular jet with low pressure ratio
A hybrid DSMC/Navier-Stokes frame to solve mixed rarefied/nonrarefied hypersonic flows over nano-plate and micro-cylinder
Shear layer behavior resulting from shock wave diffraction
A novel simplified Bernoulli trials collision scheme in the direct simulation Monte Carlo with intelligence over particle distances
Study of rarefied gas flows in backward facing micro-step using Direct Simulation Monte Carlo
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Frequently Asked Questions (12)
Q2. What is the effect of a thruster on the lip of the nozzle?
During the transient period as a thruster begins to fire, the sudden ejection of relatively high-pressure supersonic gas from a nozzle into a low-pressure environment generates a shock diffraction around the lip of the nozzle, resulting in lateral vortex formation.
Q3. What is the rorticity field of a vortex loop?
As the rorticity field of a vortex loop core is an irregular shape, an equivalent diameter of a vortex is defined asdeq = √ AR π18H , where t∗0 is the time that the rorticity loop formed and it is 0.25ms, 0.18ms, 0.15ms,0.13ms, 0.1ms for Ms = 1.3, Ms = 1.4, Ms = 1.5, Ms = 1.6, Ms = 2.0, respectively.
Q4. How many particles are required to reduce the statistical error in the computed collision rates?
The number of particles in each cell must be sufficient to reduce the statistical error in the computed collision rates; typically at least 20 particles per cell are required when using the no time counter (NTC) method to calculate the number of possible collision pairs42.
Q5. What is the effect of the shock Mach number on the vorticity?
Increasing the shock Mach number causes the shape of the rorticity loop cross-section to change comma-like shape to a mushroom shape.
Q6. What is the method for investigating rarefied flows?
The direct simulation Monte Carlo (DSMC) method3 is a standard tool for investigating rarefied flows with moderate to high Knudsen number.
Q7. What is the flow flux of a vortex?
The circulation can be decomposed into a rorticity flux that describes the fluid-rotational strength of a vortex and a shear vector flux that represents the shear strength of a vortex.
Q8. What is the main reason for the demand for thrusters in low Earth orbit?
The continuous growth of applications for cost-effective micro-satellites in low Earth orbit (LEO) is leading to a requirement for specialized thruster systems that can provide thrusts in the micro- and mili-Newton range, in order to control their motions and orbits8.
Q9. How many ensembles are required to obtain a 10% uncertainty in the velocity of nitrogen gas?
For instance, to obtain a 10% uncertainty in the velocity for nitrogen gas at a Mach number of 0.1, 286 ensembles with 25 particles in each cell are required.
Q10. What did the authors do to avoid reflections of expansion waves and incident shock waves?
The authors enlarged the fluid domain outside the shock tube exit to allow for a longer time scale and avoid reflections of expansion waves and incident shock waves.
Q11. What is the rorticity field of a vortex?
The rorticity field always coincides with the closed-loop streamlines if the vortex is stationary in the plane perpendicular to the rotational axis, such as in a Taylor-Green vortex sheet or a Burgers vortex, and it does not coincide with the closed-loop streamlines if the vortex translates.
Q12. What is the basic algorithm that all DSMC solvers follow?
An overview of the basic algorithm that all DSMC solvers follow can be given as:1. Update the position of all particles in the fluid domain using the particle tracking algorithm, which also deals with the motion of particles across faces of the mesh, and applies boundary conditions.