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Tracer pathline statistics have rarely, if at all, been used in the investigation of compressible subsonic, transonic and supersonic flows past a circular cylinder. Here, we report pathline histogram, conditional histogram and zonal histogram data, focusing on the characteristics of particle instantaneous flow reversal and their dependencies on Mach number and tracer release position. The far-upstream Mach number and the diameter-based Reynolds number used for these three flow regimes are $ ({0.2, 10000}), ({0.9, 3900}) $ (0.2 , 10000) , (0.9 , 3900) and $ ({1.2, 10000}) $ (1.2 , 10000) , respectively. The subsonic surface-release histogram profiles display unexpected persistent oscillations at a frequency $ 50 $ 50 times of the periodic vortex shedding frequency, reflecting the effect of a very small magnitude zig-zagging type of particle motion in a region very close to the wall and slightly behind the mean flow separation location. No similar high-frequency oscillation is observed in the corresponding transonic and supersonic histograms likely because, at $ \textrm{Ma} \ge 0.9 $ Ma ≥ 0.9 , periodic vortex shedding ceases to exist and the near-wake becomes a quasi-laminar recirculation zone bounded by a pair of converging slip-layers with a neck opening to the far-wake. At the instant of $ 5 $ 5 subsonic vortex-shedding periods after being released from the cylinder surface, there are $ 1.67\% $ 1.67 % , $ 35.2\% $ 35.2 % and $ 39.7\% $ 39.7 % particles that experience flow reversal in the subsonic, transonic and supersonic flows, respectively. Surprisingly, in the present transonic flow, growth of the turbulent far-wake behind the pair of lambda-shocks is constrained over a considerable streamwise distance. [ABSTRACT FROM AUTHOR]

There are numerous aerodynamic and nonaerodynamic methods to control flying devices, one of which is lateral jets, i.e. a high-speed method with convenient operation at low speeds or high altitudes. In this research, a new arrangement of lateral jets is examined by testing in a wind tunnel. The test is conducted on the Basic Finner model. In this design, the jets at the top and bottom of the model are arranged in pairs and parallel to each other. This combination, in addition to controlling pitch channel, provides the necessary conditions to control the roll channel. In this paper, pressure distribution is examined in the upstream and downstream areas as well as middle of jets. The flow visualization method is also used. The results are provided for subsonic, transonic, and supersonic free flow regime at the positive and negative angles of attacks. In the subsonic and supersonic flows, the achievements of the binary jets are the further pressure reduction on the middle line of jets compared with the same position at downstream of a single jet, and maintaining a high-pressure area of a single jet at the upstream of jets compared with the upstream area. However, the pressure reduction rate is lower in the transonic regime and the effectiveness of the angle of attack is greater than the subsonic and supersonic flows. Finally, a comparison with numerical result is accomplished. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of finding a stationary point of a nonlinear dynamical system whose state variables are under inequality constraints. Systems of this type often arise from the discretization of PDEs that model physical phenomena (e.g., fluid dynamics) in which the state variables are under realizability constraints (e.g., positive pressure and density). We start from the popular pseudo-transient continuation method and augment it with nonlinear inequality constraints. The constraint handling technique does not help in situations where no steady-state solution exists, for example, because of an under-resolved discretization of PDEs. However, an often overlooked situation is one in which the steady-state solution exists but cannot be reached by the solver, which typically fails because of the violation of constraints, that is, a non-physical state error during state iterations. This is the shortcoming that we address by incorporating physical realizability constraints into the solution path from the initial condition to steady state. Although we focus on the DG method applied to fluid dynamics, our technique relies only on implicit time marching and hence can be extended to other spatial discretizations and other physics problems. We analyze the sensitivity of the method to a range of input parameters and present results for compressible turbulent flows that show that the constrained method is significantly more robust than a standard unconstrained method while on par in terms of cost. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]