Non-stationary Viscous Flow Research Articles

Impact Assessment of Nonstationary Viscous Flow in a Cycle of a Hybrid Reciprocating Power Machine on Fluid Consumption in a Slot Seal

Impact Assessment of Nonstationary Viscous Flow in a Cycle of a Hybrid Reciprocating Power Machine on Fluid Consumption in a Slot Seal

Efficiency of an auto-propelled flapping airfoil

The present study deals with an investigation of the flow aerodynamic characteristics and the propulsive velocity of a system equipped with a nature inspired propulsion system. In particular, the study is aimed at studying the effect of the flapping frequency on the flow behavior. We consider a NACA0014 airfoil undergoing a vertical sinusoidal flapping motion. In contrast to nearly all previous studies in the literature, the present work does not impose any velocity on the inlet flow. During each iteration the outer flow velocity is computed after having determined the forces exerted on the airfoil. Forward motion may only be produced by flapping motion of the airfoil. This is more consistent with the physical phenomenon. The non-stationary viscous flow around the flapping airfoil is simulated using Ansys-Fluent 12.0.7. The airfoil movement is achieved using the deformable mesh technique and an in-house developed User Define Function (UDF). Our results show the influence of flapping frequency and amplitude on both the airfoil velocity and the propulsive efficiency. The resulting motion is contrasts to the applied forces. In the present study, the frequency ranges from 0.1 to 20 Hz while the airfoil amplitude values considered are: 10%, 17.5%, 25% and 40%.

Обтекание двух сфер нестационарным потоком вязкой жидкости

Обтекание двух сфер нестационарным потоком вязкой жидкости

The wall-jetting effect in Mach reflection: NavierStokes simulations

The wall-jetting effect in Mach reflections in viscous pseudo-steady flows (as obtained in shock tubes) is investigated numerically. The W-modification of Godunov's scheme has been modified to solve the Navier-Stokes equations using a splitting into physical processes. The viscous terms are approximated using an explicit scheme with central differences in space and a two-step Runge-Kutta method in time. Two analytical models are considered. The first is a self-similar viscous flow model in which we consider a flow field with characteristic size L, and assume that as the characteristic size grows from 0 to L, the viscosity of the gas ahead of the shock wave varies from 0 to μ 0 . Consequently, the flow can be made self-similar by using the parameter Re = ρ 0 a 0 L/μ 0 . The second is a real non-stationary viscous flow, in which the molecular viscosity during the growth of a characteristic size from 0 to L remains constant and is equal μ 0 . As a result the viscous effects are only partially accounted for in the self-similar viscous flow model in comparison to a real non-stationary viscous flow model, since they are smaller in the former case

Effect of the Nonstationary Viscous Flow in the Capillary on Oscillating Bubble and Oscillating Drop Measurements

The dynamic behavior of a bubble or drop oscillating at the tip of a capillary immersed in a surfactant solution is considered. The pressure variation in the cell and the nonstationary flow in the capillary are taken into account. The amplitude- and phase-frequency characteristics of the system are obtained, which contain information about the relaxation processes at the interface and in the bulk phases. Their dependency on the system geometry, the bulk properties of contacting media, and the viscoelastic properties of the interface is analyzed.

Calculation of non-stationary viscous flows with domains with strong non-uniformities

The possibilities for using certain implicit schemes to calculate non-stationary flows of a viscous, heat conducting gas with domains where there are strong non-uniformities (a boundary layer, a shock wave, a mixing zone etc.) are considered. The problem of the decay of an arbitrary discontinuity close to a bounding plane is solved numerically.

An implicit difference scheme for calculating non-stationary viscous flows with regions of strong non-uniformities

A difference scheme for calculating high-speed non-stationary two-dimensional flows with regions of strong non-uniformity is proposed. The scheme is based on a divergent form of differential equations combined with methods of splitting and linearization of the nonlinearity.

Calculation of nonstationary viscous flows

The present study will consider the problem of formation of a nonstationary flow of a viscous, thermally conductive gas around a semiinfinite plate, with the gas being set in motion instantaneously from a state of rest (problem I) and behind a shock wave incident upon the gas (problem H). A numerical method will be used, based on integration of the complete system of Navier-Stokes equations. Special attention is given in the solution to these times when the simplifying assumptions of boundary layer theory are invalid.