Using a simple model for the trail formation of ants, the relation between i)the schedule of feeding which represents the unsteady natural environment, ii)emerging patterns of trails connecting a nest with food resources, and iii)the foraging efficiency is studied. Simulations and a simple analysis show that the emergent trail pattern flexibly varies depending on the feeding schedule by which a...

In this paper, the unsteady flow of non-Newtonian fluid through a porous medium when an external magnetic field is applied is investigated. The non linear equation of motion is transformed to a similarity differential equation which is solved using the method of successive approximations. The rheological effects are shown and discussed on the velocity profile in terms of rheological parameter o...

Unsteady helicopter rotor aerodynamics are complicated. This paper reviews some of the fundamentals and newer developments of unsteady helicopter aerodynamics. Rotor flow is beautiful and complex. Visualizing rotor flow allows for an appreciation of the following theories and solution attempts as well as nature’s complexities. The flow through a helicopter rotor with forward motion is shown in ...

Several approaches for modelling the longitudinal aerodynamic coefficients of a fighter aircraft at high angles of attack, including the unsteady effects are presented. A traditional approach where the model of the coefficient arises in the form of the steady and unsteady effects, the unsteady effect being modelled by means of transfer functions. The second approach uses an internal variable de...

The unsteady flow field in a reversible pump-turbine is investigated during the continuous load rejection using a 3D computational fluid dynamic analysis. Numerical calculations are carried out using the detached eddy simulation (DES) turbulence model and a new approach involving automatic mesh motion. In this way, the instability of the flow field is analyzed by continuously changing the guide...

An unsteady flamelet/progress variable model has been developed and formulated as an extension of the steady flamelet/progress variable model. For this model, a large number of unsteady laminar flamelet simulations is performed for various conditions, and solutions are recorded as function of time. From this, a flamelet library is generated, which provides the filtered quantities of all scalar ...

Linear equilibrium and non-equilibrium models for leaching of solutes in soils give rise to unsteady linear convection–diffusion–reaction problems. We present several numerical schemes to approximate the solution of this kind of problems based on Stabilized Finite Element Methods, including the recent Link-Cutting Bubbles strategy adapted to deal with unsteady problems, which gives the best num...

A number of closed-form fundamental solutions for generalized unsteady Oseen and Stokes flows associated with arbitrary time-dependent translational and rotational motions have been developed. These solutions are decomposed into two parts corresponding to a longitudinal wave and a transversal wave. As examples of application, the hydrodynamic forces acting on a sphere and on a circular cylinder...

Traditionally, solving the adjoint equation for unsteady problems involves solving a large, structured linear system. This paper presents a variation on this technique and uses a Monte Carlo linear solver. The Monte Carlo solver yields a forward-time algorithm for solving unsteady adjoint equations. When applied to computing the adjoint associated with Burgers’ equation, the Monte Carlo approac...

Lin & Pauley [2] studied unsteady boundary-layer separation from an Eppler 387 airfoil at low Reynolds number numerically and compared their results with wind tunnel measurements. They found unsteady large-scale structure might control the lowReynolds-number separation bubble reattachment with smallscale turbulence playing a secondary role [4]. Drela [5], Drela & Giles[6] used a fully coupled n...