Abstract
In this study, the drag exerted by an accelerating fluid on a stationary 2D circular cylinder is numerically investigated using Fluent 19.2 based on the finite-volume method. The SST k–ω model is chosen as the turbulence model because of its superiority in treating the viscous near-wall region. The results are compared to literature, and the numerical methods are validated. The acceleration of the inflow is analyzed for the range of 0.0981–9.81 m/s2, and the drag for each acceleration is compared. Additionally, the effect of the initial velocity on the drag acting on the circular cylinder is investigated at two initial velocities. As a result, a supercritical region, typically found under steady state conditions, is observed. Furthermore, vortex shedding is observed at a high initial velocity. This flow characteristic is explained via comparison with respect to the recirculation length and separation angle.
Highlights
Sudden bursts of flow or impulsive motions of a body within the flow can be observed during natural phenomena, for example, in the case of structures affected by extreme atmospheric phenomena such as tornadoes, tropical cyclones, or thunderstorms
The results show, in a fragmentary way, that when flow accelerated from an initial quiescent state, both the amplitude and frequency of force coefficient fluctuations exceeded those recorded during steady flow tests
Solvers with second-order accuracy were chosen for pressure and scheme momentum, turbulent kinetic operator algorithm wasand adopted for the pressure–velocity that uses a relationship between the velocity pressure corrections to enforce coupling mass conservation and obtain the pressure energy, andthe specific dissipation-rate
Summary
Sudden bursts of flow or impulsive motions of a body within the flow can be observed during natural phenomena, for example, in the case of structures affected by extreme atmospheric phenomena such as tornadoes, tropical cyclones, or thunderstorms. Conducted specialized wind tunnels for a bluff body under a sudden increase (impulsive starting flow) in wind velocity They explained that drag overshoot is generated by an inertial force proportional to du/dt and the formation of vortices. Fackrell [17] developed a numerical model to determine the force on a 2D circular cylinder in the case of constant relative acceleration and applied the dimensionless technique to separate drag and added mass coefficients. The drag change according to initial velocity was compared considering low and high initial Reynolds numbers, and the acceleration range was extended to 0.01–1.0g. Because the fluid force acting on the bluff body is closely related to the shape of the wake, their relationship is investigated to identify the drag increase due to acceleration and to provide a basic understanding thereof
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