Flow around Propeller 4381 with duct is computed with the large eddy simulation methodology during crashback condition. A non-dissipative robust numerical algorithm developed by Mahesh et al. (2004) for unstructured grids is used. The ducted propeller without stator blades is solved in a rotating frame of reference. The flow is computed up to about 86 revolutions at the advance ratio J=-0.7 and...

Much effort has been undertaken for the estimation of propulsive force of swimmers in the front crawl. Estimation is typically based on steady flow theory: the so-called quasi-steady analysis. Flow fields around a swimmer, however, are extremely unsteady because the change direction of hand produces unsteady vortex motions. To evaluate the force correctly, it is necessary to know the unsteady p...

In this paper we present a hybridized discontinuous Galerkin (HDG) discretization for unsteady simulations of convection-dominated flows on mapped deforming domains. Mesh deformation is achieved through an arbitrary Lagrangian-Eulerian transformation with an analytical mapping. We present details of this transformation applied to the HDG system of equations, with focus on the auxiliary gradient...

Hydraulic turbines exhibit total load rejection during operation because of high fluctuations in the grid parameters. The generator reaches no-load instantly. Consequently, the turbine runner accelerates to high speed, runaway speed, in seconds. Under common conditions, stable runaway is only reached if after a load rejection, the control and protection mechanisms both fail and the guide vanes ...

We report the numerical simulations of the horizontal convection within a rectangle cavity tank at high Rayleigh numbers. The physical solution of horizontal convection depends on the spatial resolution of the meshes. The necessary mesh number N is proportion to Ra. The unstable numerical solutions are obtained asN < cRa. This power law also implies that the spatial resolution is dominated by v...

T.J. Trella, U.S. Department of Tr~nsportation, Transportation Systems Center, Cambridge, Massachusetts 02142 and A mathematical model of non-linear reciprocating air-compressor discharge valve . system unsteady response was presented :n Part I. As a first step, to demonstrate the application of the unsteady modeling approach, a comparison of discharge discvalve response was made with a more po...

Over the last decade, interest in animal flight has grown, in part due to the possible use of flapping propulsion for micro air vehicles. The importance of unsteady lift-enhancing mechanisms in insect flight has been recognized, but unsteady effects were generally thought to be absent for the flapping flight of larger animals. Only recently has the existence of LEVs (leading edge vortices) in s...

Vortical structures and instability mechanisms of the unsteady free surface wave-induced separation around a surface-piercing NACA0024 foil at a Froude number of 0.37 and a Reynolds number of 1.52 10 are studied using an unsteady Reynolds-averaged Navier–Stokes (URANS) code with a blended k e/k o turbulence model and a free surface tracking method. At the free surface, the separated flow reatta...

This paper presents a technique used to accelerate the convergence of unsteady flows to a periodic steady state. The basis of this procedure is to assume the time period of the solution's oscillation and to transform both the solution and residual using a discrete Fourier transform. However, this paper also presents a method which iteratively solves for the time period during the process of cal...