We present an absolute measurement of the total ion-drag force on one single microparticle at the edge of the dust free region in low pressure complex plasmas: the void. In order to do so, the particle confinement position was monitored as a function of the gas pressure for two particle sizes under normal gravity conditions and under microgravity conditions during parabolic flights. At the bord...

A viscous discrete adjoint approach to automatic aerodynamic shape optimization is developed, and the merits of the viscous discrete and continuous adjoint approaches are discussed. The viscous discrete and continuous adjoint gradients for inverse design and drag minimization cost functions are compared with finite-difference and complex-step gradients. The optimization of airfoils in two-dimen...

Two simple feedback control laws for drag reduction are derived by applying a suboptimal control theory to a turbulent channel flow. These new feedback control laws require pressure or shear-stress information only at the wall, and when applied to a turbulent channel flow at Reτ = 110, they result in 16–22% reduction in the skin-friction drag. More practical control laws requiring only the loca...

It has recently been shown that the combined effect of gas drag and pressure gradients causes solid objects to rapidly migrate toward the location of maximum pressure in a gaseous nebula [1, 2]. Such rapid migrations result in the accumulation of objects in the vicinity of local pressure enhancement and may increase the rates of their collisions and coagulations. In a disk with a mixture of gas...

The ability of the three-dimensional Navier-Stokes method, PAB3D, to simulate the e ect of Reynolds number variation using non-linear explicit algebraic Reynolds stress turbulence modeling was assessed. Subsonic at plate boundary-layer ow parameters such as normalized velocity distributions, local and average skin friction, and shape factor were compared with DNS calculations and classical theo...

Wave-swept macroalgae present an excellent system for studying the effects of chronic physical stress on the morphological evolution of plants. Wave-induced water velocities impose great drag forces, leading to a morphological tradeoff between light interception and drag reduction/tolerance. What are the hydrodynamic consequences of morphological diversification, such as increased branching? Dr...

Computational Fluid Dynamics (CFD) simulations were performed to predict the interference drag produced by two streamlined struts intersecting at various angles in transonic flow since no relevant experimental data are available for use in design studies. The one-equation Spalart-Allmaras turbulence model was employed in a RANS formulation assuming fully-turbulent flow. Selected cases were run ...

Tests have been made at a Mach number of 4.03 and Reynolds number of 3'4 million on two families of models, consisting of delta wings with underslung half-Cone bodies. The wing sweepback angles were 75 ° and 80 °, and the appropriate cone semi-vertex angles tested were 4 °, 10 ° and 13 ° for the larger wing and 4 °, 6"7 ° and 10 ° for the smaller wing. The surface distributions were measured at...

Recent work in bio-fluid dynamics has studied the relation of fluid drag to flow speed for flexible organic structures, such as tree leaves, seaweed, and coral beds, and found a reduction in drag growth due to body reconfiguration with increasing flow speed. Our theoretical and experimental work isolates the role of elastic bending in this process. Using a flexible glass fiber wetted into a ver...