We present the results of an investigation of the drag force on a horizontal grid of bars moving vertically through a stratified fluid. A novel approach was used to calculate the drag, based on measurements of the terminal velocity of a freely rising grid. In the homogeneous case the drag coefficient of the grid is found to be approximately constant for a range of grid-based Reynolds numbers. I...

Analysis of the aerodynamic forces acting on baseball pitches from major league games reveals a large variance in the measured coefficients of lift and drag. We have examined possible explanations for this effect and found that, while uncertainties introduced by measurement error and the method of reporting major league pitch trajectories do explain some of the spread, the reasons for the large...

Sintered metal porous media currently plays an important role in air bearing systems. When flowing through porous media, the flow properties are generally represented by incompressible Darcy-Forchheimer regime or Ergun regime. In this study, a modified Ergun equation, which includes air compressibility effects, is developed to describe friction characteristic. Experimental and theoretical inves...

Accurate estimates for the drag coefficients of a satellite are important in reducing the biases in densities derived from satellite drag measurements as well as explicitly reducing the errors in orbit prediction. This develops a approach to estimate the drag coefficient for debris objects with known shape models.This paper focuses on rocket bodies in particular. The attitude and angular veloci...

Constant rise in fuel price in recent times has caused manufacturers of heavy commercial vehicles (HCV) to turn to efficient aerodynamic design of trucks, wagons, tractors as well as trailers. The comparative analysis in this study compares the coefficient of drag of the following four aerodynamic configurations of a tractor-trailer combination: 1. Semi-trailer with no devices. 2. Semi-trailer ...

The towing of an underwater object by means of a cable attached to a ship is an important problem in underwater technology. An underwater towed body is generally at the mercy of hydrodynamic and hydrostatic forces, which controls its motion through water. These forces affect the depth characteristics of the towed body giving specific configuration to the towline. This work consists of the devel...

The distribution of dynamic pressure behind a Harris' hawk's wing was sampled using a wake rake consisting of 15 pitot tubes and one static tube. The hawk was holding on to a perch, but at an air speed and gliding angle at which it was capable of gliding. The perch was instrumented, so that the lift developed by the wing was known and the lift coefficient could be calculated. The mean of 92 est...

Dynamical assimilation of surface elevation from tide gauges is investigated to estimate the bottom drag coefficient and surface stress as a first step in improving modeled tidal and wind-driven circulation in the Chesapeake Bay. A two-dimensional shallow water model and an adjoint variational method with a limited memory quasi-Newton optimization algorithm are used to achieve this goal. Assimi...

The drag coefficient C_{D} of a solid smooth sphere moving in a fluid is known to be only a function of the Reynolds number Re and diminishes rapidly at the drag crisis around Re∼3×10^{5}. A Leidenfrost vapor layer on a hot sphere surface can trigger the onset of the drag crisis at a lower Re. By using a range of high viscosity perfluorocarbon liquids, we show that the drag reduction effect can...