It is widely known that losses due to viscous, thermal and molecular relaxation play an important role in sound propagation. Traditionally, acoustics is concerned with the treatment of the fluid as a (linear) continuum using macroscopic quantities such as velocity and pressure as dependent variables. However, the continuum model has its limitations and the model breaks down for Knudsen numbers ...

The open-frame structure of work-class ROVs results in significant model uncertainties, and its motion is strongly disturbed by the umbilical cable. To address these problems, this article developed a nonlinear disturbance observer-based super-twisting double-loop sliding-mode control (NDO-STDSMC) method to achieve trajectory tracking with system uncertainties external disturbances. First, new ...

In this work we present a hybrid particle-grid Monte Carlo method for the Boltzmann equation, which is characterized by a significant reduction of the stochastic noise in the kinetic regime. The hybrid method is based on a first order splitting in time to separate the transport from the relaxation step. The transport step is solved by a deterministic scheme, while a hybrid DSMC-based method is ...

The ability to compute rarefied, ionized hypersonic flows is becoming more important as missions such as Earth reentry, landing high mass payloads on Mars, and the exploration of the outer planets and their satellites are being considered. These flows may also contain significant radiative heating. To prepare for these missions, NASA is developing the capability to simulate rarefied, ionized fl...

A new variable exponential discrete-time sliding mode control (DSMC) reaching law is proposed to suppress the chattering phenomenon and accelerate speed for switching function. The consists of two-phase different term. main effect first phase reduce steps. second can decrease magnitude quasi-sliding-mode domain (QSMD). Otherwise, disturbance term restrained by order difference function which al...

Multi-species modeling is implemented for the particle-based ellipsoidal statistical Bhatnagar–Gross–Krook method monatomic species in open-source plasma simulation suite PICLas. After a literature review on available multi-species extensions of kinetic model equations and approaches determination transport coefficients, Brull's former Wilke's mixing rules collision integrals latter. The implem...

The direct simulation Monte Carlo (DSMC) method is a versatile computational technique capable of simulating a wide range of gas ows. It can compute from the continuum to the rar-eeed regime. It is a molecular simulation method and consequently it can model complex thermo-chemical physics with relative ease. Unfortunately the method is computationally expensive in terms of memory and compute ti...

Underexpanded jets have become widely used in studies of rarefied-gas flows [1][3] and aerodynamics of hypersonic probes in wind tunnels [4]-[7]. The objective of the present study is to analyze shapes and flow parameters in internal regions of hypersonic underexpanded viscous jets, and to apply the jet theory to hypersonic studies. Analytical solutions [7] are used for estimating internal flow...