# Grid-converged Solution and Analysis of the Unsteady Viscous Flow in a Two-dimensional Shock Tube

## TL;DR

This paper provides a detailed, grid-converged numerical analysis of unsteady viscous flow in a 2D shock tube at Re=1000, revealing complex flow phenomena and establishing benchmark data using a high-order gas-kinetic scheme.

## Contribution

It offers the first grid-converged solution for the shock tube problem at Re=1000 using a new high-order scheme, advancing numerical simulation accuracy for complex shock-driven flows.

## Key findings

- Identification of vortex formation and shock bifurcation mechanisms
- Detailed analysis of Kelvin-Helmholtz instability near contact surface
- Benchmark data for high Reynolds number shock tube flows

## Abstract

The flow in a shock tube is extremely complex with dynamic multi-scale structures of sharp fronts, flow separation, and vortices due to the interaction of the shock wave, the contact surface, and the boundary layer over the side wall of the tube. Prediction and understanding of the complex fluid dynamics is of theoretical and practical importance. It is also an extremely challenging problem for numerical simulation, especially at relatively high Reynolds numbers. Daru & Tenaud (Daru, V. & Tenaud, C. 2001 Evaluation of TVD high resolution schemes for unsteady viscous shocked flows. Computers & Fluids 30, 89-113) proposed a two-dimensional model problem as a numerical test case for high-resolution schemes to simulate the flow field in a square closed shock tube. Though many researchers have tried this problem using a variety of computational methods, there is not yet an agreed-upon grid-converged solution of the problem at the Reynolds number of 1000. This paper presents a rigorous grid-convergence study and the resulting grid-converged solutions for this problem by using a newly-developed, efficient, and high-order gas-kinetic scheme. Critical data extracted from the converged solutions are documented as benchmark data. The complex fluid dynamics of the flow at Re = 1000 are discussed and analysed in detail. Major phenomena revealed by the numerical computations include the downward concentration of the fluid through the curved shock, the formation of the vortices, the mechanism of the shock wave bifurcation, the structure of the jet along the bottom wall, and the Kelvin-Helmholtz instability near the contact surface.