Visual motion, such as radial optic flow, is an important cue for perceiving direction during ego-motion. Several previous studies have reported that the perceived speed of a radial optic flow is underestimated when the represented ego-motion direction between radial optic flow and non-visual (such as vestibular or/and proprioceptive) information is congruent. In the present study, we examined ...

The transition to turbulence in pipe flow does not follow the scenario familiar from RayleighBenard or Taylor-Couette flow since the laminar profile is stable against infinitesimal perturbations for all Reynolds numbers. Moreover, even when the flow speed is high enough and the perturbation sufficiently strong such that turbulent flow is established, it can return to the laminar state without a...

In an earlier paper in Entropy [1] we hypothesized that the entropy generation rate is the driving force for boundary layer transition from laminar to turbulent flow. Subsequently, with our colleagues we have examined the prediction of entropy generation during such transitions [2,3]. We found that reasonable predictions for engineering purposes could be obtained for flows with negligible strea...

Laminar and turbulent natural convection inside concentric spherical shells with isothermal cold and hot boundaries is numerically investigated up to Rayleigh number values Ra 6 10 and Pr = 0.71. The study utilizes direct numerical simulation (DNS), large eddy simulation (LES) and Reynolds averaged Navier– Stokes (RANS) approaches for investigation of the laminar, transitional and fully develop...

We consider a passive scalar that is advected by a prescribed mean zero divergence-free velocity field, diffuses, and reacts according to a KPP-type nonlinear reaction. We introduce a quantity, the bulk burning rate, that makes both mathematical and physical sense in general situations and extends the often ill-defined notion of front speed. We establish rigorous lower bounds for the bulk burni...

Direct numerical simulation (DNS) is applied to investigate properties of katabatic and anabatic flows along thermally perturbed (in terms of surface buoyancy flux) sloping surfaces in the absence of rotation. Numerical experiments are conducted for homogeneous surface forcings over infinite planar slopes. The simulated flows are the turbulent analogs of the Prandtl (1942) one-dimensional lamin...

in the present work, an engineering method is developed to predict laminar and turbulent heating-rate solutions for blunt reentry spacecraft at hypersonic conditions. the calculation of aerodynamic heating around blunt bodies requires alternative solution of inviscid flow field around the hypersonic bodies. in this paper, the procedure is of an inverse nature, that is, a shock wave is assumed a...

The homoassociation of H(4)TPPF(5)S(3) leads to different J-aggregates depending on whether solutions are shaken (homogenization) or stirred magnetically (square-section flask). Vortex stirring due to the generation of laminar flows decreases lateral diffusion therefore it inhibits cluster-to-cluster aggregation mechanisms.

In shear flows like pipe flow and plane Couette flow there is an extended range of parameters where linearly stable laminar flow coexists with a transient turbulent dynamics. When increasing the amplitude of a perturbation on top of the laminar flow, one notes a a qualitative change in its lifetime, from smoothly varying and short one on the laminar side to sensitively dependent on initial cond...

We study the dynamics of two-dimensional Poiseuille flow. Firstly we check our calculations with previous results concerning the laminar solution and the minimum Reynolds number such that it becomes unstable. Next we studied time periodic solutions which, because of the imposed periodicity in the stream-wise direction, are rotating waves, what allow us to treat them as stationary flows in a mov...