We derive and evaluate expressions for the frictional Coulomb drag between disordered two-dimensional electron gas layers. Our derivation is based on the memory-function formalism and the expression for the drag reduces to previously known results in the ballistic limit. We find that Coulomb drag is appreciably enhanced by disorder at low temperatures when the mean-free-path within a layer is c...

Studies of insect flight have focused on aerodynamic lift, both in quasi-steady and unsteady regimes. This is partly influenced by the choice of hovering motions along a horizontal stroke plane, where aerodynamic drag makes no contribution to the vertical force. In contrast, some of the best hoverers--dragonflies and hoverflies--employ inclined stroke planes, where the drag in the down- and ups...

We calculate the spin-drag transresistivity ρ↑↓(T ) in a two-dimensional electron gas at temperature T in the random phase approximation. In the lowtemperature regime we show that, at variance with the three-dimensional low-temperature result [ρ↑↓(T ) ∼ T 2], the spin transresistivity of a twodimensional spin unpolarized electron gas has the form ρ↑↓(T ) ∼ T 2 lnT . In the spin-polarized case t...

High-Reynolds number flow over tree-like fractals is considered, with emphasis on the drag forces produced. Fractal objects display large scale-disparity and complexity while being amenable to a simple and standardized description. Hence, they offer an elegant idealization of the actual boundaries in practical applications where turbulence interacts with boundaries that are characterized by mul...

CL, CD, CD0 = lift coefficient, drag coefficient, and drag coefficient with zero lift DSi = dynamic soaring number sample E, Emin = aircraft total energy and minimum sustainable total energy, J g = gravity acceleration, m∕s h, hmin = altitude and safety altitude, m K = drag-polar-induced drag gain k1, k2, k3 = necessary and sufficient conditions inequality parameters L, D = lift and drag forces...

In the present study, the mechanism of turbulent drag reduction by polymer additives in a fully developed channel ow is investigated using direct numerical simulation. In order to see the elastic e ect on turbulent drag reduction, the dilute polymer solution is expressed with an Oldroyd-B model which shows a linear elastic behavior. Simulations are carried out by changing the Weissenberg number...

There are different methods to reduce drag in high speed hulls. One of these methods is a change in the shape of the body by adding longitudinal side tunnels. In this paper it has been attempted to determine the influence of the tunnel height on hydrodynamic characteristics of the hull to achieving an optimum shape for the tunnel. To achieve this purpose, numerical simulation of the problem has...

A variational solution of the coupled electron-phonon Boltzmann equations is used to calculate the phonon drag contribution to the thermopower in a one-dimensional system. A simple formula is derived for the temperature dependence of the phonon drag in metallic single-walled carbon nanotubes. Scattering between different electronic bands yields nonzero values for the phonon drag as the Fermi le...

The photon drag effect of a 2D electron gas is measured using the ps infrared pulses of the wavelength-tunable free electron laser source FELIX. The pulsed photon drag response is found to depend critically on the coupling characteristics of the electrical circuit. We therefore developed an impedance and velocity matched photon drag detector. It consists of a GaAs/ AlGaAs multi quantum well sam...

The present study compares and quantitates both solvent drag and solute drag forces in a system with both heteropore and homopore membranes. It is shown that tracer solute permeability can be increased if solution flow or driver solute flux is in the direction of tracer diffusion. Either force can decrease tracer permeability if the force can decrease tracer permeability if the force is opposit...