Static pressure

About: Static pressure is a research topic. Over the lifetime, 9770 publications have been published within this topic receiving 82614 citations.

Experiments on the flow past spheres at very high Reynolds numbers

Abstract: The present work is concerned with the flow past spheres in the Reynolds number range 5 × 104 [les ] Re [les ] 6 × 106. Results are reported for the case of a smooth surface. The total drag, the local static pressure and the local skin friction distribution were measured at a turbulence level of about 0·45%. The present results are compared with other available data as far as possible. Information is obtained from the local flow parameters on the positions of boundary-layer transition from laminar to turbulent flow and of boundary-layer separation. Finally the dependence of friction forces on Reynolds number is pointed out.

Temperatures in the Earth's core from melting-point measurements of iron at high static pressures

Abstract: THE temperature distribution in the Earth's core places important constraints on the Earth's internal heat budget and on models of the geodynamo. The solid inner core crystallizes from a liquid outer core, consisting mainly of iron alloyed with a lighter element, at a depth of about 5,100 km (corresponding to a pressure of about 3.3 Mbar). Thus, the most reliable means of determining the temperature gradient in the core is to estimate the melting temperature of iron and iron-rich compounds at the pressure of the inner core boundary. Current estimates range from about 4,000 to 8,000 K; but these estimates, obtained from shock compression1–3, theory (discussed in ref. 4) and extrapolation of static pressure data2,3,5, are poorly constrained. Here I present melting-point measurements on iron and iron–oxygen compounds at static pressures of up to Mbar. Extrapolation of these results to 3.3 Mbar yields a temperature at the inner-core boundary of 4,850±200 K. A weak change in optical absorption observed above 2,000 K may correspond to the solid–solid phase transition found in shock experiments at 2 Mbar (ref. 1).

Numerical Solutions of Spherical Blast Waves

Abstract: The strong‐shock, point‐source solution and spherical isothermal distributions were used as initial conditions for a numerical integration of the differential equations of gas motion in Lagrangean form. The von Neumann‐Richtmyer artificial viscosity was employed to avoid shock discontinuities. The solutions were carried from two thousand atmospheres to less than one‐tenth atmospheres peak overpressure. Results include overpressure, density, particle velocity, and position as functions of time and space. The dynamic pressure, the positive and negative impulses of both dynamic pressure and static overpressure, positive and negative durations of pressure and velocity, and shock values of all quantities are also described for various times and radial distances. Analytical approximations to the numerical results are provided.

Flow around rectangular cylinders: Pressure forces and wake frequencies

Abstract: This paper concerns an experimental investigation of the flow around and pressure forces on fixed (non-vibrating) rectangular cylinders at angles of attack 0°–90°. Pressure forces and moments for cylinders for cylinders with side ratios B A = 1, 1.62, 2.5 and 3 (shortest side A = 20 mm) were estimated from measurements of static pressure distributions at mid-span. Wake frequencies and associated Strouhal numbers were determined from hot wire measurements in the near-wake regions (A = 4 and 20 mm). With the smaller cylinders 12 side ratios within B A = 1–5 were investigated. The free stream turbulence intensity was less than 0.06%, blockages less than 5% and aspect ratios L A greater than 50. Reynolds numbers, based on A, ranged from about Re = 400 to Re = 3 × 104 (pressure measurements from about Re = 3 × 103). For the square cylinder, the measured pressure forces were used for calculations of quasi-steady galloping response in the plunging mode.

The Determination of Turbulent Skin Friction by Means of Pitot Tubes

Abstract: A simple method of determining local turbulent skin friction on a smooth surface has been developed which utilises a round pitot tube resting on the surface. Assuming the existence of a region near the surface in which conditions are functions only of the skin friction, the relevant physical constants of the fluid and a suitable length, a universal non-dimensional relation is obtained for the difference between the total pressure recorded by the tube and the static pressure at the wall, in terms of the skin friction. This relation, on this assumption, is independent of the pressure gradient. The truth and form of the relation were first established, to a considerable degree of accuracy, in a pipe using four geometrically similar round pitot tubes—the diameter being taken as representative length. These four pitot tubes were then used to determine the local skin friction coefficient at three stations on a wind tunnel wall, under varying conditions of pressure gradient. At each station, within the limits of experimental accuracy, the deduced skin friction coefficient was found to be the same for each pitot tube, thus confirming the basic assumption and leaving little doubt as to the correctness of the skin friction so found. Pitot traverses were then made in the pipe and in the boundary layer on the wind tunnel wall. The results were plotted in two non-dimensional forms on the basis already suggested and they fell close together in a region whose outer limit represented the breakdown of the basic assumption, but close to the wall the results spread out, due to the unknown displacement of the effective centre of a pitot tube near a wall. This again provides further evidence of the existence of a region of local dynamical similarity and of the correctness of the skin friction deduced from measurements with round pitot tubes on the wind tunnel wall. The extent of the region in which the local dynamical similarity may be expected to hold appears to vary from about 1/5 to 1/20 of the boundary-layer thickness for conditions remote from, and close to, separation respectively.