Inertia

About: Inertia is a research topic. Over the lifetime, 12006 publications have been published within this topic receiving 164291 citations.

On driving a viscous fluid out of a tube

Abstract: Two problems are considered. First, it is shown experimentally that the amount of viscous fluid left on the walls of a horizontal tube, when it is expelled by an inviscid fluid, reaches an asymptotic value of 0.60 of the amount required to fill the tube, when the parameter μU/T is increased, μ and T being the coefficients of viscosity and interfacial surface tension respectively, and U the velocity of the interface between the two fluids. Secondly, by neglecting the inertia terms in the equations of motion and the effect of gravity, a theory for the passage of this type of bubble is presented, together with experimental results in support of the theory. It is shown that such a solution is only valid under certain other restrictions, and then only to within half a tube diameter of the nose of the bubble.

Analysis and Design of a Direct-Drive Arm With a Five-Bar-Link Parallel Drive Mechanism

Abstract: The direct-drive arm that has no gears between motors and their loads have several important advantages including no backlash, small friction, and high mechanical stiffness. The arm mechanism, however, becomes extremely massive, when each motor is directly attached to its joint along a serial linkage mechanism. The complicated dynamics resulting from varying inertia, interactions, and nonlinearities, is also more prominent than that of a robot with gears. This paper describes a lightweight arm mechanism with invariant and decoupled inertia characteristics. Instead of having motors at serial joints, a parallel drive mechanism with a closed-loop five bar linkage is utilized. The dynamic behavior of this mechanism is analyzed and the condition for the elimination of the interactions and nonlinearities in the mass properties is derived. The decoupled and invariant arm dynamics significantly reduces the complexity of controlling the direct-drive arm. In the latter half of the paper, a prototype robot developed on this basis is described. By using high torque brushless motors which were specially designed for the direct-drive robot, top speed and maximum acceleration were increased by an order-of-magnitude to about 10 m/s and 5 G, respectively.

The Viscous Spreading of Plane and Axisymmetric Gravity Currents

Abstract: Measurements of the spreading rates of gravity-driven currents at both the surface and the bottom of a fluid layer of different density are reported. For the case of a constant inflow rate the spreading relations are derived by estimating the order of magnitude of the forces involved. After an initial balance between gravity and inertia forces the final spreading phase is governed by the balance between gravity and viscous forces. For the latter flow regime, measurements in plane and axisymmetric flow geometries agree well with the spreading relations for gravity currents with a no-slip boundary. The proportionality factor, which is not predicted from this model, is then determined from the measurements and a good agreement is found with the theoretical value derived in the accompanying paper by Huppert (1982).